Trying (and failing) to build a 48v DC Generator for Off-Grid Backup

[@RandomZ88]

I think that this has been mentioned previously, The alternators will work in the way you have them set up. However, you have to isolate the second alternator from the chassis. Due to the chassis being the ground for the First alternator. Best way would be to find a way to isolate both the alternators from the chassis and each other. In the way that you have is wired/set up, the first alternator is shorted to itself through the second alternator case because it is connected to the frame and by default the case of the first alternator.

[@DannyBokma]

Sorry for being blunt, but if you didn't see this problem coming ( the common ground being a problem for putting them in series), then it will be very challenging to make the system work with your proposed solutions. A few pointers for the proposed solutions: 1) Since the windings are fixed your are not going to change a 24V output to a 48V output with any usable power output. 2) The field applied to the rotor has a linear relation to the output current, not the output voltage. The field is used to control output current, not the output voltage. 3) Sidenote; alternators are current sources, not voltage sources ( although they try to regulate to a certain voltage, they highly depend on a battery for making that system stable ), current sources should not be put in series without additional care of making them stable. By far the simplest solution to this problem is: Use the alternators as intended (beware that some alternators need a light / lamp to operate correctly ), connect each alternator to a 24V battery ( preferably leadacid to keep it simple ), isolate both systems from each other and the machine it's mounted to. Then connect both systems in series.

[@jomangeee9180]

I am electronically challenged so let me ask you some questions 1-isn't the whole premise of an alternator being to generate electricity/voltage? 2-putting circuits in parallel makes the voltage additive? 3- wouldn't diodes help fix his problem 4- would't a cheap Automatic Voltage Regulator stabilize the voltage?

[@Trialnerror]

I didn't see it coming because I put zero real thought into it but thanks for being blunt anyway. Windings are fixed but I'm already getting 70 volts out of it by turning up the field on the rotor (next video). I did think about your two battery option already, and I may end up going there but first I want to play around with them a little longer to see if I can find a simpler solution. I do appreciate the constructive feedback part of your reply though.

[@martehoudesheldt5885]

1- change the armature volts you change output volts. that is how voltage regulation works. take a 60's 70's Chrysler alternator (2 wire external regulated alternator and try it . they used to make a kit that you could get 120vdc out of them for drills and such with brushed motors(universal) it looped the output back to the arm. but remember double volts half the current. 2- you are right and wrong at the same time- volt and amp are intertwined to load. volts battery being base volts, alt volts = to batt= 0 amp. raise alt volts above batt volts you get current (amps) . that is how the volt regulator works. 3 - if that is the case how does a chevy 1 wire alternator work? only wire that goes to it is the battery lead. if you must use 2 alternators replace the diode bridge and regulator in one to pos ground .

[@jomangeee9180]

@@martehoudesheldt5885 you guys seem to know a lot, so please answer me simple question: when he connected the 2 negative leads of off the alternators, they are no longer in series, and they cancelled each other out! so why didn't he connect the positive lead to the negative lead?

[@martehoudesheldt5885]

@@jomangeee9180 because the case is the negative of both and would short one out

[@jasoncarter5002]

One of those two spade terminals is a voltage sense wire that allows you to measure voltage at the battery instead of the alternator to account for voltage drop due to resistance . It is internally connected with a high value resistor so it will sense at the output terminal without the sense wire on since that would be a common and horrible problem. Use two equal value resistors to create a 2:1 voltage divider. Connect your 1/2 voltage signal to the sense terminal. 24v become 12v so the alternator regulator sends more power to the rotor until the sense wire reads 24v. Output will be 48v. In theory you will need 2x rpm, In practice maybe not that much. Also, you might as well go get at least the 420 predator. Alternators are tough but not efficient.

[@mihkus]

He couldve just bought one off aliexpress... " Range extender fully automatic 5kw " Neodymium magnet generators are much smaller and super efficient when compared to those car alternators.

[@Chris_at_Home]

@@mihkusI have a remote cabin and 20 years ago I got a 48v inverter charger. I thought about making one of these or even getting a 24 v alternator with a 24-48 converter. Instead I got a Honda that has an eco throttle. The inefficiency of converting 120 vac to 48v with the Honda probably offsets doing it directly with something like this. Also I can control the charge rate and run time of the Honda through the inverter..

[@susanvaughn741]

Why not use regular car altinator with external regulator set to 48volts?

[@tombrenes2411]

Awesome content Love all the hard work My 2 cents : The entire unit I’d put it on a metal dolly (mobile unit camping or off grid ) The pedifile motor change it to run off propane, remove the governor, a racing carb better out put at low RPM save even more fuel To calm the vibration platform to frame weld used valve springs To ground use heavy long welding ground clamp with magnet In an off grid system get those copper rods cut in quarters, point and into the ground or clamp to a bumper bracket (member 2 separate grounds) * one motor . . . 2 alts one set to do refrigeration / or ice machine to prolong cooling and lighting Second pair of alts (can disengage from main motor) used as a back up or power washer and a shop for tools maintenance or even build a house, stable, ranch, mill wood I got my idea from Brazil they got this down the power companies keep this hush hush

[@danielohara2974]

I made a 48v generator using an 8kw 48 volt motor I got from amazon a few years ago. I used a chain and sprockets and with a few switches I was able to power the motor so it started the gas engine. after the engine was running I would switch off the battery and then use the motor as a generator. The motor was only 400 bucks brand new.

[@carld3184]

I am assuming that you bought a 40V DC motor?? Which implies the use of a commutator inside the motor, in other words like an older DC automotive generator? Or am I missing something?

[@danielohara2974]

@@carld3184 Yes it was a 48v dc brushed motor. since then I changed over to a dual engine setup with two 24v dc motors so I have two separate systems just in case one breaks down.

[@jeeper426]

you could use externally regulated alternators (or convert those to externally regulated) the more voltage you put to your windings the more voltage output it gives, using a custom rolled AVR or finding a 48V AVR and as i said converting those alts to externally regulated, then pushing the whole 48v (or i guess 50V in this case) through a set of full bridge rectifiers to get your full power output, add some caps and you can smooth any output ripple and get clean output power to what you are trying to charge

[@keithm8715]

Exactly, get two large case Ford 100amp externally regulated alternators. I have welded off these for years. You just need to pony up $$$$ for a 48 volt regulator. You can try amptech alternator for one of their regulators, but think they may only do 12/24 volt.

[@shashiekka7917]

This is just what is needed for partial rv backup. Operates the ac and stuff perfectly. kzbin.infoUgkxOTeIs0vv4_9B5hsmnLsk9r930uDQLu_Y is quieter than my rv generator. Only suggestion is that it needs a fuel shutoff valve. So it is easier to store.

[@barrellcooper6490]

Go look at what David Poz did. To bad you guys didn't collaborate. His design worked electrically, very cool. His mechanical setup not so great but he was trying to get 48v down and dirty... Cheap. Tesla is going to a 48v system for accessories, lighting etc. Ditching 12v. Hopefully as that makes 48V stuff will become more available. I imagine the day when I'm running solar into a 48 VDC battery bank and then feeding it to the house directly to power 48V HVAC, lighting, and other devices. Meaning no inverter or a very small one to handle legacy 120V appliances. I except to see Marine and RV applications move to 48V. I can dream right?

[@AdamDavisEE]

As you're finding out, you can convert the alternators to output a higher voltage. The current will be the same, and with a higher voltage you can achieve a higher power output. That's why alternators are rated in amps, and an alternator for 12v costs roughly the same as a 24v alternator at the same amperage - same amount of copper. Rectifying it yourself will solve the problem of the negative case grounding, and you will need a new control system since the alternator's field control is also tightly integrated with the negative chassis ground - once you properly isolate it you might as well make your own. Further, with your own control system you can make it constant voltage, constant current, or follow a charge profile - at that point it becomes a much more useful generator than a simple alternator based generator. You aren't going to be running high enough voltages to worry about coil arcing. One thing to be aware of and consider mitigating is the alternator/rectifier combination is going to produce ripple, which may impact battery degradation. The research paper "The effects of high frequency current ripple on electric vehicle battery performance" (free access through ScienceDirect link: www.sciencedirect.com/science/article/pii/S030626191630808X ) indicates that low frequency ripple results in slightly more cell degradation than zero ripple charging, and high frequency ripple is less damaging than low frequency ripple. Since you've got the horsepower, I'd suggest increasing the speed of the alternator(s) by increasing the diameter of the pulley on the engine, and running the engine at a higher RPM. These engines are governed to 3,600 RPM, but their peak power occurs just over 4,000 rpm, so altering the governor will not only make your generator more efficient, it'll also increase the ripple frequency which will reduce the cell degradation caused by the ripple. As a nice bonus, it'll make it easier to reduce the ripple with capacitors - higher frequency ripples require less capacitance to reduce them appreciably.

[@AdamDavisEE]

Ah, the downside of the higher voltage is that the rotor winding may not support the current required to maintain the stronger field. Measure the temperature of the rotor after a long run and make sure you're not in danger of overheating it. That is one big reason that might force you back into two alternators in series. Even if you implement more air cooling, it represents an energy loss, so overall lowered efficiency. You've already got the two alternators, properly rated to generate a field suitable for 24v each, might as well use them. If you do overvolt them to 48v, make sure you have some margin for hot summer days. On the other hand, gas is so inefficient and expensive to start off with, that the extra energy lost is probably not significant compared to what you'll be generating.

[@AdamDavisEE]

And just in case it's not clear - the field will need to be stronger the more power the alternator outputs. Checking the temperature after a no-load test won't tell you much. Figure out how much power the alternator was intended to generate - for instance, 24v at 70A is 1,600W, then run a 1,600W load at 48v - about 33A - for two hours and check the rotor temperature. Add some margin to cover hot days and you'll probably be in good shape.

[@paulkaygmailcom]

optimal BSFC for those engines stock is ~12-13ft/lb @ 2750-3000 rpm

[@sea_bass21]

such a great idea and then the announcement of part 2. That felt so relatable to when I build something.

[@northidahodreaming5657]

Thanks for doing this. I really enjoy your channel and humor. I'm also stuck with running an AC gas genny to charge my off grid system in the winter. I think that I've exhausted my searching for a reasonably priced commercially produced DC battery charging generator. I run a 5 kw AC generator between 70 to 125 hours annually. I look at this cost of this operation as reasonable. I don't know enough electrical engineering to build my own DC charging unit. In my mind, as a sort of parallel thought, I rationalize that I drive a 14 mpg 4x4 truck for about 2K miles per year in the deep snow and a 48 mpg Prius the rest of the year. The large inefficiency and expense of my winter transportation is necessary and reasonable. but please keep doing Trial N' Error and I'm delighted to watch.

[@frosthoe]

I put two deep cycle 12v 100AH batteries and boxes mounted on the bottom of a wheeled movers dolly. Added a shelf with a 6.5HP briggs engine 2 -110 A 12v alternators. Battery disconnect , fuse/breaker, cables and a power inverter. 100 % portable! Works like a charm, mobile, 2kw pure sine 110Vac power anywhere anytime... silent or loud. Right about $500 total. Saved our casket freezers and basement from floods 3 times over last 18 months already. its paid for! Thinking about getting a small diesel car like VW jetta etc and making it into a gennerator. Seen a few conversions around now.

[@markglanville6495]

If you ever build a version 2 and wanted to make it less top heavy, turning the engine 90 degrees and having two pulleys on the crank with two belts running an alternator each side of the engine should work without additional tensioner pulleys. You mentioned decreasing the rpm, but it needs to be high enough to provide sufficient cooling when producing 100 amps as the alternators could overheat. I've thought about the same type of project, I have a cheap 100 amp DC inverter welder that could be used on my generator. The off load voltage is about 70v and can be finely adjusted with the welding current knob. Inverter technology is surprisingly efficient, and it would be a very cheap option. In the UK gasoline is very expensive, Amazon sell cheap natural/propane gas conversion kits for clones of the Honda GX200 engine that replace the Carburetor, providing three fuel options. I bought one for only £25 from Amazon in the UK. Great option for a generator that hardly gets used as no gasoline to turn bad, it will just work when needed! If cheap gas is not important, a propane cylinder will sit for years before it is used. All food for thought!

[@shiningirisheyes]

Buthane and propane gas 🎉in EU and GB costs about double the cost of liquid fuels like gasoline or diesel per kilo and energy equivalent so gets pricy per kw compared to liquid fuels .I don't know cost for propane and buthane gas in USA but natural gas might be cheap enough on direct pipe feeds but I don't know if there is natural gas bottles😅😢

[@cliffweatherbee6914]

DavidPoz just built something like this. He used a treadmill DC motor that produced over 100V but lower amps, attached that to an MPPT charge controller to output 48v and 14 ish amps. Another issue you have is that most Automotive engines have an 8-11 inch crankshaft pulley. That coupled with a 3ish inch alternator pulley will give you your desired RPM and allow you to use less power to drive the alternators.

[@paulkaygmailcom]

power needed to drive the alternators will remain the same.. ideally you want to run the engine in it's peak torque/efficiency RPM range

[@cliffweatherbee6914]

@@paulkaygmailcom power to drive the alternator goes up as demand/output goes up. It could be anywhere from 1-5 HP PER alternator. There's two and these are 24V High Output. Which means the load on the engine could be even more. We could be looking at using upto 15 HP to run these at high load.

[@paulkaygmailcom]

@@cliffweatherbee6914 i doubt the 24v/100a rating of those old delco alts.. better off using the large frame hairpin denso units

[@soldierski1669]

For what it's worth, great idea, back in the early days of YT you would see projects like this, mostly riding mowers converted to welders. Another guy on YT ran into a similar issue doing this with a Bike, he used a separate DC input to excite the regulator. I would simply isolate the grounds on each alternator, get the power from both units and figure it out post. Going to check your next vid and see what you did...and maybe see if you got a heater.

[@virgilius68]

I got this Chinese DC range-extender for charging my 48V battery, it works great! It costed 240 Euro. Seen it charging up to 70Amps so far and it think it will do more. I use it on a sailboat for actualy extending my range if needed

[@grahamswain7356]

I like the way you looked into the alternator construction and the explanation , so grateful for your video I would to see it again much appreciated many thanks .

[@platnumspider999]

I have done this many times in the past. And have built these all you need is two 100 a bridge rectifiers. Hook up a ground wire to each rectifier on the incoming 3-phase AC terminal doesn't matter which one. And then Bridge the other two incoming AC terminals together with a link . And then hook a positive wire to the to link AC terminals from each individual alternator. This will give you two separate negatives and 2 separate positives totally isolated from the system that you can then run the dc outputs in a series to create your 48 volts. I would also recommend putting a 100-amp breaker on each rectifier that way if the rectifier shorts or goes bad it doesn't take out the system it just trips the breaker

[@platnumspider999]

AC to DC Bridge rectifier in also be used as dc-to-dc isolators. As the same and you can use these to charge for 12 volt batteries independently isolated even though they're all hooked up in series for 48 volts

[@platnumspider999]

I always put 100 amp breaker in between everything as well. that way in case a rectifier blows it doesn't take out the system it just trips the breaker

[@stevenschildhauer9853]

When I was in the Navy Seabed, our Chevy blazers and 1 ton pickups had dual 12 volt alternators wired in series to produce 24 volts to charge the 24 volt starting system and for NATO compliance. The alternators were 100 amp, 12 volt, ISLOATED GROUND units. They were NOT case GROUND. The vehicle ran on 12 volt except the starter and military radios. Each alternator was wired to a paint of 6TN batteries and one was wired to the main harness in the vehicle. The wiring the the vehicle was the same as any square body Chevy from the mid 80's.

[@sstorholm]

What I’d do is figure out a high enough field voltage to generate around 30 V per alternator, feed that constantly to the field, remove the regulator entirely, and just rectify the output externally with 6 diodes. That way you can then wire them in series, and use a solar charger to manage the battery charging. Solar chargers work just fine with any DC source except regulated ones (you see this quite well when you bench test solar chargers with a current limited bench supply, the solar charger will load the source until it starts current limiting, causing the charger to back off, and you get this constant back and forth between the source and the charger). Otherwise you’ll constantly fight with the internal regulator, as the alternator expects a lead acid battery for it to charge. There might also be special purpose alternators on the market that are meant to be used with an external regulator, or ones that are just constant 24V with isolated output terminals.

[@imchris1978]

Probably been said before but you can remove the regulation and use a separate source to power the rotor then feed the output (from a converted 12v its approx. 120v no idea if a 24v alternator would be the same) into a 'wind turbine' mppt to charge your batteries, With this method you could use just a single alternator and have it directly coupled to the engine as its a little more efficient.

[@jdrissel]

As soon as you said 2 24v alteratators I knew you were in trouble. My 2¢ is to go with a 24v system and a boost converter. You will need some voltage stabilization on the alternator output. An 8D truck battery is actually perfect because it is heavy and can take vibration. This will help keep your generator from shaking the whole county when it runs. Make sure you grab a buck converter to make a battery maintainer that runs off your solar battery. If you use a maintainer and keep the battery in somewhat climate controlled conditions it will last for decades as long as you do not over-discharge it. Best part is all this can make what you just built actually work.

[@spacecase0]

When you try modifying them to just put out 48V each and wire them in parallel, you might run into the diodes built in not being rated for enough voltage, but unlikely. Running your own circuit to drive the field coils is going to work, I know plenty of people that do that. Some use a DC motor speed controller to set the coil current. And that works, but you will need to get it some feed back so it can regulate voltage and not just current out of the alternator. Anyway, I wish you good luck

[@MustangsTrainsMowers]

March 2020 my moms retired friends gave me an older Generac 6500 watt generator that hadn’t been ran in a long time. I had to buy a new fuel shut off valve as the old ones gasket failed. I have to still install the valve and try to get it running. My moms friends also gave me a full trash pump, gas leaf blower and a 2 wheel battery powered weed sprayer cart. So when something breaks they just buy a new one and give me the old one to fix.

[@casen2007]

Great video and impressive DIY project! I had a thought regarding the challenge with the 24v alternators. Instead of wiring the alternators in series directly, what if you wire each alternator to its own 24v battery or capacitor in parallel? Once charged, you can then connect the two batteries or capacitors in series to achieve the desired 48v output. This approach might simplify the setup and ensure efficient charging without interference. Just a suggestion! Keep up the fantastic work, and I'm looking forward to the next video!

[@oisforoffroad]

Cool intro 1:30 That's a neat way to introduce what you were doing.

[@billbush-t5x]

You can adjust the field in GM Delco alternators up to about 90 volts. reg. screwdriver through the back fins to field screw.

[@specialservicesequipment393]

you'd have to pull the regulators and diode sets from the alternators, and connect the coils in series to give you double the power, you'd in reality probably need 2 alternators, then the 48 VAC can be routed through a full wave bridge rectifier, then to an external regulator. you need to have an engine with enough HP, then setup a pulley system that will spin all the alternators at the proper speed.

[@evildaddysteve]

You could have set up two 24 volt batteries with each alternator charging and voltage sensing off of a one of the batts. Then rig the series output of the batteries to your system.

[@ithoughtitoldyou1956]

Absolutely awesome and a far better way than buy the super expensive 48 volt alternators. simple put a throw switch separating your battery bank into( 2) 24 volt banks and charge each bank from each alternator you have done an amazing top quality job. I like your work . Sincerely Glen

[@battery_solar_ev]

Just to toss this out there I have a 12 volt set up i built myself that works really nice Im very happy with it. If you want 48 volts your going to need a 48 volt brushless turbine or alternator (permanent magnet) some where in the 2000 watts area but that will only give you about 40 amps + or - 5 depending on efficiency. What type of batteries you have is going to play in a factor or 2 as well. I run a hybrid AGM and Li-Ion system myself but 12 / 15.8 volts. That 50 amp breaker you have on this build will fail they are junk best off to use a ANL fuse.

[@GarthClarkson]

Now that you have done the hard work, all that is left is to do proper wiring. Why do you have to ground them to the chassis? Keep them separate and floating (insulated/isolated). Use a 24v battery in parallel with each alternator as a buffer and wire each circuit accordingly. Then wire the two circuits in series and if you are super paranoid put a heavy duty (>100A) diode between them to isolate the battery sensor wire. That should do it in a way that they won't get any phase issues or efficiency losses. The main reason that vehicles use a ground is to halve the amount of wiring needed and make it easy to complete circuits. If you really have to ground it then ground the lower alternator as per usual and float the upper (24-48v) circuit. Cheers.

[@GarthClarkson]

You could also add a heavy duty dual battery balancer unit to make sure they don't get out of hand...

[@martehoudesheldt5885]

if you must use the 2 alternator setup then replace the diode bridge and regulator to a positive ground model then you can series them. but remember that the regulator can only sense the output of the one alternator (the one that it is on) and not the total volts. or use isolated truck alternators then it doesn't matter what they are mounted to

[@BenderOMetal]

Wouldn't it be easier to output the alternators to two separate 24 volt batteries and then pull your 48 volts from the two batteries run in series? That would allow you you use your current build, which looks nice by the way, and keep the alternators stock so they would still be easy to replace if they fail. Which they eventually will.

[@jmaus2k]

The negatives of both 24v sets would be tied to ground. Can't be connected in series or they short.

[@michaelbenoit248]

@@jmaus2k, or u could use a diode on the power wire to the batteries from the alternators. To keep current flowing one way, & not backwards. If u put a diode on each wire going to the alternators ground & hot it could work. Or I wonder if he could just spin the crap out of one of the alternators & get 48v. See what the max rpm for the engine they are meant to be on is, get an extended warranty on the alternators, then when ur burn em out get a new one for free.

[@obiecanobie919]

Take one alternator apart and insulate the negative from its body so it can be connected to the first alternator’s positive.it’s voltage regulator should follow the same path .

[@jmyers9853]

i built sort of the same but used an alternator off a bmw, it is rated at 180 amp and 12 vols. used a car tensioner with the belts. even with 5 horsepower it will start cars with a dead battery

[@motomech83]

how did you electrically isolate at least one of the alternator cases so you could put them in series without shorting. also if they are externally controlled id recommend keeping them off till the engine rpm gets up to prevent stalling the engine. ops spoke to soon i see. good luck ill be looking for second video

[@dodgeme1986truck]

Here is how the army used to create 24v charging from 2-12v alternators they used divorce (floating) ground alternators to start with... You will need a positive battery connection for each alternator in the stack for you example each 24vdc alternator needs a 24v battery connection. Connected alternator 1 ground to chassis ground, alternator 1 positive to 24v battery connection, next the alternator 2 ground connects to alternator 1 positive (24-48 battery negative) connect the alternator 2 positive to the 24-48 battery positive. Another option is to run the alternators in parallel powering a 24vdc to 48vdc converter to reach your final charge voltage

[@stevenfrazier8939]

The PMA produces 3,500 watts at 2700 RPM. The diesel runs at 3,000 RPM maximum. Running 2,000 RPM it will consume about 0.25 gal/h. Running at 2,000 RPM the PMA will produce around 2,500 watts. So around 10 Kilowatts per gallon of Veggie-Oil with a 30% gasoline blend for the winter. Gasoline is need as a solvent to thin the viscosity and prevent gelling. Summer blends are around 10%. Although these PMA's can out put 3,500+ watts it is not advisable to do so., as the small motor would struggle at peak output. These numbers are not set in stone and do change a little, We need to take into account the losses of the AC to DC to DC conversion and whether or not the batteries need all the power the PMA is producing. The Midnite classic determines the charge need. In case your wondering the cost of the winter blend is about 5 cents per kilowatt hour. The electric grid rate in our area is 17.4 cents per kilowatt hour.

[@jimthvac100]

for a 48volt battery back you will need close to 57Volts potential to properly charge it. Regarding efficiency, power transfer etc.. You need about a 2 HP engine to drive a 1KW generator so your choice of a 7.5HP engine to drive your generator was spot on; However your choice to use automotive 24V alternators was a bad choice as they are terribly inefficient as compared to a PMA alternator.

[@james10739]

I have seen people talking about getting 100v or so out of modified alternators that seems like a decent idea maybe just with an arduino or something to control it I don't remember how it was done I think just by bypassing any regular but it was obvious unregulated so if you could control the voltage to the field windings you could probably dial it in and it would be cool to have current reading and it could very the voltage to limit current appropriately

[@SmogFighter]

Isolation of the two housing will give you the ability to series them together. Also, since the power being generated initially is AC, then rectified to DC, it doesn’t matter which way the alternators are mounted. As for rectification, swapping the diode orientation on one of the alternators would also work.

[@evil17]

The direction of rotation is important for cooling as the fan blades are generally orientated to induce cooling in one direction.

[@DoctoreE644]

​@@evil17 you can get reversed blades to get the air flow going the right way. They are used on twin engine boats, where one engine turns opposite the other. Also, because the field is rotating, an alternator can be spun in either direction and it will work. As far as getting 48 volts out of the setup, I'm not sure it will work the way you plan. An alternator without a load will put out lots of voltage, but as soon as a load is applied, the Voltage will drop to it's designed output. If you plan to run it at 48 volts, you will have to remove the internal regulator and use a separate rotor supply source, because running 48 (50 volts or more in reality) will destroy the built in regulator. It will require an electronic power supply that is voltage variable, so output doesn't exceed 50 volts or whatever the 48 volt operating system requires. it is complex, but not unattainable. Out of my 50+ years of rebuilding alternators (and starters), I have never had the opportunity running two alternators in series. At this point, I wish I had. It's an interesting concept.

[@oliverscorsim]

Also you can isolate ground just check the setup in the duse and a half they have one 12v for 12v then a second 12v to make 24v the second has an isolated ground. Take the back cover off and follow it to case ground and isolate that to external. And follow what Chevy did. Biggest issue is it wont sense voltage great so the high amp charge wont last long enough with any modern battery. But doable

[@shaunnightfire8269]

Great video, and good idea (in theory) on using 24v alternators.

[@amulocog]

This is a great work, congrats. You've put lots of efforts and commitment but note that two ac sources can be in series only when they are perfectly 180 degree out of phase, having no common ground. This is though possible, difficult to achieve. However, you can rectify each to dc, and put the two resulting dc outputs in series. This I think will work fine.

[@earlelf3142]

Easy as mounting 1unit to a plastic isolator. the + from the grounded unit on the frame to the case of the isolated unit, the + on the isolated now is 48vdc. wire the voltage regulator for each unit only to its self. 24 +24 = 48 gust like 2 24v battery's = 48v.

[@Guds777]

Alternators will work spinning either direction. The only problem is the cooling fan, but you can get aftermarket fan blades that will cool the alternator in reverse...

[@amjtech]

Bypass/remove the diode packs go to an external rectifier and run them full field at 12v into a 120v max MPPT charge controller.. easy peasy.. heat only gets generated with wattage.

[@BlindDude]

Man the things Lego has now.. When I was a kid, 51 now, I got the first electric motor Lego came out with. Boy was it slow but had good torque. I got bored with it and hooked up a lamp cord. BOOM!

[@mafosa9563]

"damn good project! you got everyone chiming in! im watching too!!

[@stevenfrazier8939]

I wanted to charge our 48 VDC nominal battery bank without having conversion loss. This is how we do it. Using Waste Veggie-Oil ia a $230 196cc diesel connected to a $660 48 VOLT - 3 phase PMA going into a $89 300 amp rectifier and then going into a $650 Midnite classic 150. This #DC1248AC Dual Core PMG/PMA turns at 2,700 RPM and makes 3,500 Watts + and charges the 46KW LifePO4 battery bank for pennies. The Midnite classic treats the PMA as a solar source and controls the charge parameters perfectly. Total cost $1,629. I would post the links but KZbin deletes them. You could also use a 212cc Harbor Freight Predator engine and pay for gasoline.

[@mbanc443]

on 15:28 if both generators put in series - left is getting shorted, so to resolve this problem left generator needs to be put on isolating block like fiberglass or will be good for testing at least wood. Ultimately both AC generators need to be isolated in order to connect them in series and then load onto rectifier bridge and only output from the bridge for ex. negative can be connected to the stand as common ground if negative need to be a common.

[@ronmoore3290]

Isolated ground alternators are common. Two regulators or one with an isolated output made by you will work. I think I would build a programable regulator. Regulators are simple devices that switch the field on and off depending on the temperature and voltage of the alternator.

[@seansysig]

You’ll need to provide a thermally actuated cooling fans to cool the engine. Your alternators would require identical internal construction. They would have to be properly phased (and remain locked to that phase). Note they can’t be belt driven as slippage and belt travel would take them out of phase! You could drive them with chain and sprocket, but they must spin at the same ratio. As you stated you’d need a 48 volt DC source such as a 48 volt DC battery bank to produce the exciter coil current so they could generate an output voltage. Good luck finding the proper diodes.

[@Trialnerror]

I could be wrong here but phase issues are regulated to the AC side. I'm not having a problem there, it's the DC side that's the issue. Doesn't matter how they spin individually so long as you're not trying to tie in the unrectified AC outputs.

[@leealsing1539]

The rectifier circuit deals with AC to DC and once DC phase is no longer a problem. The engine and alternates have fans inbuilt, so heat dissipation should not be an issue, but if enclosed then thought will need to be given to ensure airflow.

[@growleym504]

Normally I would say using a gasoline engine is a terrible mistake. However, if you are using solar and maybe wind as primary charge sources,and the gas powered generator is only for backup, it is more acceptable to take the efficiency and lifespan hit. But a small diesel pull from a scrapped out or upgraded sailboat would be a lot more dependable and you would not have to worry about gasoline fumes blowing up your garage. A floating ground generator is easy sneezy. Mounting two floating ground alternators on the same chassis not so easy. You could rewind for 48v, but my solution would be to source a used BLDC or PMAC motor, and a Kelly sine wave controller. The motor and controller, in regen mode, produces current. Probably more efficient than an alternator and rectifier, almost certainly more efficient than TWO alternators. The key element is the controller. It must be regen capable and put out reasonably clean DC. Motenergy is a good reputable maker of reasonably inexpensive motors in the 5kw class. A 5kw motor and controller charging 54V (okay call it 50V for simple arithmetic) at 20A is a kilowatt. The motor would run basically forever at that load. If you want to charge at more than 1kw, better to get a 10 or 12kw motor and a 500A or better controller. The controllers are rated at peak not sustained power so 500A is not really all that big. A ME0913 motor (I don't remember if it is rated at 10kw or 12kw but I always treated it as a 12kw motor) or the new model that replaces it, don't remember the number, would be a good machine for sourcing say a 5kw load. You would also want an engine capable of at about a 10hp power output to take full advantage of that size motor. These motors are air cooled and brushless and so are extremely low maintenance. A used one should be fine, and you should be able to find one for about $300 if you are patient, about the same amount for a controller, maybe a bit more. I prefer the Kelly controller because it is user programmable. Tech support from China can be a little dodgy but I accidentally knocked over a coffee can full of quarters on my DIY electric sailboat and long story short (pun unintended but I will let it stand) one landed right on the output phase terminals of the controller and when I powered it up, kablooey. I sent it back to the factory and two months later I had a rebuilt controller with new finals, no cost. So points for Kelly. You could also build an axial flux permanent magnet alternator pretty easy. Many builders of DIY 1kw class wind generators have made them, and you can find a lot of documentation online. Maybe run the rectified output through a solar charge controller?

[@windsine]

just use a 120vac or 240vac AC generator, rectify it to DC and send it into a Midnite charge controller (Hawkes Bay would work great), park the PPT. Thats the easiest way to have reliable DC generator that is careful about charging your batteries. Ive used a DC genset on my batteries for the last 15 years and works great. I prefer to custom build the alternator from scratch.

[@CookieManCookies]

I see you are trying to put them in series together, you should be adding them later after the bridge rectifier, the two coils aren't going to be in "sync" when creating AC.

[@topnotchcontent]

I seen a video where they used 5" pulleys 1:1 and it was perfect voltage at Low RPM 2500 WITH 100A current.

[@glumpy10]

Nice Diy work in the fabrication and idea. I didn't think of the grounding issue but knew it wouldn't work as you are using internally regulated alts which will limit to 24/ 30V output on the final output. I built a 24V backup system using a Diesel engine and a truck alternator. Look forward to seeing how you figure the 48V problem!

[@Trialnerror]

Believe it or not, I've already got one to produce 70v at the output just by turning up the field windings, so I have some hope. I'm going to keep messing around with it and see what I can figure out. Thanks for watching!

[@67bajabuilder]

You could simplify things greatly by leaving the alternators alone and charging your 48 volt battery bank as two groups of 24 volt banks.

[@rockskipper5353]

So can u just ground both alternators with a jumper cable and a ground rod or something metal (like a welder )???

[@leealsing1539]

The issues I'm seeing are when you increase output you are going to probably change the rectifier due to power/heat dissipation (possible that voltage may exceed components design specification.) Also may need to think about a soft start circuit, to prevent engine stalling when load first applied and for starting the engine. I believe that you will need to run in parallel to achieve the current output. (This may also cause issues balancing the load, but not 100% sure.) It would be worth contacting a rewind/ reconditioning centre. As they may have access to the 48v rated electric components which will reduce work, and save having to design your own circuits (ie rectifier and voltage regulator)

[@briankuhn7396]

14:25 Words to live by! Your commentary had me laughing through this whole video. 😂

[@dane9175]

A 48 Volt conversion cool the see it would also make a cleaner install😎

[@shiningirisheyes]

Thanks I suspected this issue I would charge 2 battery banks of 24 volts and then series the battery banks would be my logic preference but would love to see your 48 volt solution. In marine diesel normal 12volt alternators can't supply rated power for very long they heat up and basically go to 13 volts and low amp slow charge. Proper marine types take longer to heat up and step down in stages but power will go down to low volts and low amps .Alternators to give ,100 amps continuous at 12 volts have to be top end bigger more costly types . I assume same for 24 volts alternators Normal v belts with high drag nearly always slip so serpentine belt or chain is the normal solutions The gasoline engine needs to go more like 2x faster than alternators RPM as it is awful low end torque so needs high RPM to work correctly is my best advise but suspect it's still too small .Mostarine diesel generators are twice the power in watts than the generators demands where continuous several day demands are made .In those cases the generators or alternators need to run at 2 times diesel engine RPM to make usefull amps and volts due to slow RPM high torque nature of diesel engines .EG why diesel engines are the majority in higher than 6 kw electric in generator production I suggest single pot 10 hp 7.5kw diesel air-cooled l100 yanmar or similar as minimum preferably 10 kw to give 5 kw power output at 50 volts and 100 amps DIY plans exist for 12 inch diameter home brew 50 volt wind generator with higher effency than alternators and are not to difficult to make and fairly cheap .That would strain the engine less I suspect and allow the gasoline 7.5 hp to work

[@johnbroadbent9034]

a question in in the uk a generator has 2 windings 110/240 volts I think in series to acheav

[@kamikazekunze]

Maybe….. add a charge controller to the mix? It’ll take the 24v x2 and spit out the voltage you need. Sub’d

[@johnbroadbent9034]

240 volts and parallel for the 110volts ,so how are the windings in the usa 110volt output if you have 2 windings is it possible to redo them for 50 volt output

[@rhiantaylor3446]

This would have been simpler with a single 12v 100a alternator. Remove the regulator so that you have direct access to the three AC phases and to the rotor brush connections. The alternator is designed to produce 12V below idle rpm with 12V on the rotor and, without the internal regulator, it will output volts in proportion to rotation speed. A typical alternator might be geared to run at 3x crank speed so will give over 12V at 3x600 crank rpm (say). so if you gear it to run at 6000 alternator rpm you will be getting close to your target output voltage with 12V on the rotor. You then need a bit of simple electronics to adjust the rotor volts to give the required output volts. An external 3 phase rectifier is also needed - I wouldn't trust the internal rectifier to work at the higher voltage.

[@eddygoodwin7089]

Good idea

[@jmaus2k]

Can you get a positive ground 24v alternator? Then you could have one of the negative ground and positive ground to give you 48V. You should be able to rewire the one you have as a positive ground, but might require mounting the regulator outside the alternator chassis.

[@shadowdemon13]

Instead of all the measurements to mount the motor, use some tape, trim to the mounting surface of the motor, punch out holes. Then put the tape (this time measured) to the rails. Drill the hole punch out and done. Saves a few minutes AND is a bit more accurate than being off a 16th or more. Nice design.

[@dLikesDDs]

isolate grounds, 2 battery banks @24v each so each bank is charged independent from the other. with them in series you would still get 48v

[@papabits5721]

A cheap Chinese dc generator head unit? They make belt driven units that would eliminate all the fuss. Great idea and video.

[@carnaud]

Couldn’t you use rectifiers and then join them up afterwards?

[@awesometrades5036]

Suggestion, use something like a Victron Orion-Tr DC-DC 24 / 48 Volt converter

[@AussieDev81]

Well deserved like for 2 reasons: 1. That thing looks like a twin turbo water pump. 2. "Rectum-fire" 😂

[@evil17]

Great vid & not a bad build effort mate, a fun & handy project. I believe it is possible to control ur rotor voltage separately to boost ur output voltage, you could then use a MPPT controller to regulate ur output voltage to a safe & stable set output limit to ur batteries regardless of rpm. I have serious doubts that motor will have enough power to run 2 x 100A alternators which would be around 5kw total, I think 1 alternator could make that engine work hard enough if modified to output a higher voltage, and then it could be directly coupled also increasing efficiency. I’m guessing 2-3kw will probably pull it up, & u could possibly need to consider extra cooling for the alternator also.

[@2000freefuel]

about 9 minutes in here, you most definitely can run an alternator "backward" there are universal vane-type fans available for them, as for wiring them in series yeah it was done on the 1980s GM CUCV trucks used by the ARMY but I'd recommend removing the internal regulators and running an external that will let you push to voltage up to your 48-volt charging voltage. also don't forget that incandescent "IDIOT LAMP" is a critical part of the charging system.

[@Nele_BiH]

you could use permanent magnets motors from fitness track or how you say it

[@barrellcooper6490]

To those saying just buy a regular 120V generator and 48V charger: You missed the whole point of generating 48V directly!! Every device or component you use to transform power reduces efficiency. You take gasoline and turn it into mechanical energy (torque and rpm) at the shaft output. Probably recover about 30% of the chemical energy in gasoline. Then turn a generator to transform mechanical energy into electrical energy. Using an inverter inside the 120V generator you converter the actual generators out put into 120VAC maybe 90-95% efficient. Then run that through a device to convert 120VAC to 48VDC at maybe 70-90% efficiency. So instead he's trying to go straight from the mechanical output to 48VDC directly, hopefully improving efficiency 20- 50% of the overall energy conversion.

[@Trialnerror]

Nailed it!

[@jp-ny2pd]

If the problem is to charge a 48v nominal battery bank then I would probably suggest a different approach. I'd get a 240v primary to 120v secondary AC transformer. Feed 120v from your generator to the primary (240v) side which will give you 60v on the secondary (120v) side. You can then pretty easily convert the 60v AC to DC with a bridge rectifier and smoothing capacitor. You'll drop a few volts through the rectifiers which will be about right for charging a 48v battery bank.

[@orbitONhigh]

problem with that is you have no current regulation, you dump 60V onto bus that say is at 53v because the batteries at at a lower state of charge you pull hundreds of amps out of that transformer. if the transformer, generator, and batteries are not all capable of handling that something will break. you would have to hack the generator voltage regulator to correct this. also high amp low voltage transformer are not super common so they are expensive or you would have to use and oversized say 480 to 240 transformer. where the secondary can handle hundreds of amps so like 25kva transformer for like 6kva of power which is also expensive. plus you still have core and copper losses in the transformer to deal with.

[@jp-ny2pd]

​@@orbitONhigh My issue is not with his approach but the use of automotive alternators. Those 100-amp alternators are really only designed around a 30% or so duty cycle. What he wants is 100% duty cycle or 48v@100a for days on end. In order to do that reliably he'd probably need 3 or 4 alternators. If he is adamant about greatest efficiency and generating 48-60v directly I would recommend customizing and controlling a genset itself similar to what he is doing with the alternators. It wouldn't be any less expensive than what he's currently doing but it would likely be more reliable. As far as using an AC step-down transformer goes the goal for me would be to create a reliable 60V-ish DC bus using mostly commodity parts. I would never try to charge directly off the DC bus without using a charger/controller. You are correct that he would likely need to get a 25KVA transformer in order for the windings to handle 100-amps at 60v. The good news is you can get a used 240/480v to 120/240v NEMA 3R dry-type transformer for around $500 if you don't mind taking your time and picking it up yourself. As far as 100s of amps goes you are only ever going to pull what the generator can provide before popping it's own over-current protection. For safety I would still breaker the secondary side of the transformer just to limit overall power through it. Efficiency wise you are going to be 95% efficient through a common 60hz AC transformer. The goal with my approach was to be as robust and reliable as possible using mostly commoditized off-the-shelf components. Even with the 25KVA transformer if it does fail for whatever reason you can buy another one and just wire it in since they're a super-common transformer. With a customized alternator setup or a re-wired genset if that fails you are just kind of done. There is no driving somewhere, picking something up, and simply slapping it back in where the old one was. In all likelihood you will get years if not decades of service life out of a transformer while being able to move to more efficient gensets at any time. The input for the Transformer could just be a weatherized L6-30 connector so you could hot-swap the generator whenever you want.

[@KevinSmith-os5yz]

If he allready has a 110v generator, why not just get a 48 volt charge controller? And use the existing generator.

[@jp-ny2pd]

@@KevinSmith-os5yz he's got one but it's only 2kw and he wants 5kw. He also wants to remove losses from the various inverters in the setup and go directly to the DC bus for his battery chargers to use

[@corborst4872]

It's not so difficult, but I wouldn't use 24 volt truck alternators for this but rather a strong (4 -7kw) permanent magnet hub motor from an electric scooter or E-Bike. I did do this on a slow running diesel 1 cylinder (Hatz diesel) and got amazing efficiency out of this 35yo engine, almost 28% while charging the LiFePo4 48vdc batteries, place a capable 3 phase rectifier between the 3 phase wires of the hub motor and this will get you a nice 48vdc output for your batteries. You have to mate the engine speed and the hub motor speed to get maximum output and efficiency, my hub motor runs 600rpm and my engine speed is 1400rpm, all belt driven, output about 2200watt, but I use a 3000 watt MXUS hub motor only. I'm planning to use a 5kw hub motor in the future to get a 3000watt continues output at 1700~ish engine rpm, this would be the most efficient I think.

[@Defianthuman]

I saw a video where someone took a normal car alternator and removed the regulator got it up to 80v. You could do something like this for 48v but I don’t know if it would still do 100amps.

[@Trialnerror]

I did try this as well, got up to 100v but of course the amperage dropped in relation to it.

[@geoffmolyneux9173]

1) on one alternator just remove the case ground on diode Bank. Hook this electrical diode ground to other alternator positive 2) just electrically isolate whole alternator case. Then then hook this case to other alternator positive.

[@eddygoodwin7089]

Bingo

[@EelingStudios]

Have you thought about Agni DC motor/generator?

[@devincarson5978]

it will work without rewiring, add a lead acid battery bank and isolate your positive and negative on the battery bank. wire the alternators as normal then from there you can wire the batteries as a 48 volt out to charge your lipo batteries.

[@gulag_inmate69]

Parallel? With a boost converter?

[@driverjamescopeland]

Also, you didn't need to tear the alternator apart. You just needed to rectify the feed to the sense circuit... or split your batteries into 4 banks with an intelligent or manual switch. You could have banks A-B charging separately, while banks C-D are bridged in series for supply... and vice versa. This could be handled by a cheap 48v BMS... costs around $60.

[@007700jr]

I died at the Chris Hanson joke.

[@mainsource527]

So 2 alternators .. can I also use a battery or batteries and an inverter to recharge ?

[@spacecase0]

I am half way into the video and wondering how you are going to put them in series when you grounded them together

[@oliverscorsim]

So I actually sell a preconveted alternator but I dont set them up to be 48v alternator. Instead feed a solar controller at 100vdc. My recommended set up for customers is run a all in one inverter growatt is recommended. Then the inverter can deal with charge and discharge along with bypassing the battery during usage. My kits $400 ready to bolt on and I rate them at 80a but honestly 120a isnt very hard one part swap needed but the growatts dont like more than 100a and 80 at idle works out to 95-100 driving. Feel free to ask questions some stuff I'd be willing to share not publicly if you want help converting yours

[@oliverscorsim]

Also your hp to kw math is wrong it takes about 18hp to make this work at 100a in my system

[@lukefarmer5391]

Treadmill motor will work as well. I’ve seen a few KZbin videos on guys getting thrown away treadmills and making it work.

[@goldcountryruss7035]

Might work to remove or disable the voltage regulators, leave the rectifiers, and add a 100amp 48V solar charge controller as the voltage regulator. Add a switch to kill the charging so starting the engine is easier.

[@michaelvw11]

Maybe a windturbine charger to start with would be a cheap and easy way to go. These chargers accept a alternating current as input, with a wide variation range of voltages and frequencies. Just hookup a windturbine generator to the gasoline engine and your done. ( they have 48 volt dc chargers 40A for about ~40 usd. )

[@FFLFFS]

I wanted to build a 36v battery charger for my two 36 v trolling motors. (our dock is built that parallel parking sometimes is a must) I found on line a unit that changes 12v to 36v. A similar one must exist for 48v

[@jamesrossi4260]

Hey old question about the split system you installed, you were using resistor to make it run at lower temp, I have a Mr cool system and on the remote it has a Fp button, if you push and hold it it goes in freeze protection mode it will set temp to 46* just fyi shit

[@douglaswindsor120]

I had a Ford f350 I used haul a mobile high pressure washing unit since I needed power for my power tools I found a unit you hooked up to your alternator it basically shut off the power to the battery and bypassed the regulator and put power to a 120 volt plug it had a voltage meter and you increased the motor speed until it got to 110 volts on day I had a power wash job that I was doing on a oil rig camp unit I found out that everytime they rented it out they painted the new company colors over the old Greece dirt and all so everytime I thought I was almost done the next layer started peeling off so after starting at 8 am it started getting dark so I plugged in the lights on the units and reved up the truck almost to full revs before I got to 110 but I got it it and after it got dark I had finally got to the last layer of paint and dirt and I had the front and ends done before it got dark so I was doing the inside of the tool room when the Forman came by to see if I was going to finish it up as he had gotten word it would be shipped out the next day I told him I'd have to finish it the next day as I still had the back side of the unit's to do and no light and he informed me that the backside was well lighted and so I come out to take a look and found while i had switches in the various units to turn the lights on and off the backside of each unit had four 150 watt bulbs no wonder I had so much trouble getting up to voltage as that was 600 watts of bulbs on 4 unit's and I found out that I wasn't just running 8 60 watt bulbs inside the units but 2400 watts of bulbs on the backside of the units as well I finished up just before daylight packed up and left your problem is the new alternators have a built in regulator that sets the output voltage

[@joelnorton9742]

I'm just wondering how phases between the two alternators stay synced? How would you sync the phases?

[@joelnorton9742]

Of course I'm writing before I watch so...

[@RobertFulton-o9j]

In the car or truck the alternator speed is 4to6 times the engine speed in order to get a full load / charge

[@WaqarAhmadA]

Seen alternators in series first time