The $20 Way to Protect Your Boat's Starter Battery

[@BrianBHatteras43c]

I always come away from a Clark and/or Emily video having better knowledge and skill. Your content is sincerely appreciated.

[@Clarks-Adventure]

Please tell your friends and leave links everywhere you go!! Seriously I'd like a few more subscribers.

[@nodogrunner]

I am not sure why you are not the #1 cruising channel on KZbin.

[@Clarks-Adventure]

Thanks. Well tell your friends please.

[@nodogrunner]

@@Clarks-Adventure Been captivated about sailing for the last year, (scaring my wife badly) learning, researching, thinking, praying about retirement in 4-6 years. Wondered what you think of electric sailboat propulsion. Do you have a video where you talk about your stance on the subject? It's my honor to converse with you.

[@Clarks-Adventure]

I wanted to go electric since I bought Temptress over 30 years ago. I really analyzed it about 10 years ago when I repowered her. I seldom motor but when I do I find myself running it for long periods like days at a time. I feel I need the range diesel allows. I guess with today's cheaper Lifepo4 one could take the dive if it fit their criising style or even add a diesel generator and accept the efficiency loss. It's such a personal decision. No universally wrong answers. But really wrong choices for a given person. Would you repost a form of this question on the BankManager Facebook page? facebook.com/groups/bankmanagerplus/?ref=share

[@genglandoh]

I installed a Voltage Sensitive Relay (VSR) last week and it is working great. My setup is the alternator charges the starting battery and my solar panel charges the house battery. With the VSR installed when the solar panel has fully charged the house battery the VSR closes and allows the starting battery to get charged from the solar panel. When the engine is on the alternator will charge the starting batter first and then the VSR closes and charges the house battery. So simple to install and low cost. Thanks so much for your great videos.

[@gefginn3699]

Great post Clark. Stay strong, free, happy and healthy my friend. 🌞🌴⛵️

[@MrBuglerbear]

Very informative video .I really like the way you simplify concepts that may be hard to grasp for some. The money saving tips are also very appreciated too. Please keep the how to content coming.

[@vincentstouter449]

Clark, that was a brilliant pair of similes concerning the house and starter battery banks. The house bank, like a draft animal supplying the “Hotel” loads while the start bank is like the lion, lying idle but then expending tremendous energy over a short time to help the engine “roar to life”. You have the heart of a teacher, using analogy to make your point to some who may be unfamiliar with the technology you’re teaching. I’ve noticed the clear, simple way you teach and admire the care and preparation that you and Emily demonstrate in your presentations. 👍 An important point (with which I disagree) is that many now use high output alternators to charge their banks, and refrain from having a dedicated standby generator for savings of $, space, and weight. The flaw in this thinking is (of course) that if one inadvertently depletes the starting bank then the ability to charge batteries is also lost. If in a remote area, the house bank will eventually deplete and ultimately lights, navigation equipment, and radio are lost, which places the sailor back in the 17th century. This same scenario (of course) occurs if the engine is lost for any other reason. 🤔 How does the VSR regulate the different charge profiles for different battery chemistries and how does it distribute the charge when charging batteries which are at a different charge states?

[@Clarks-Adventure]

That's really outside it's scope. It just connects and disconnects lead based battery chemistries. And that's all you need to make sure your starting battery is ready to do it's thing. If you want something that lets you mix lead with Lifepo4 there is my BankManagerPlus. www.emilyandclarksadventure.com/bbms

[@raycaballero6386]

Your a man gifted to teach and to educate fellow mariners. A very uplifting presentation. Thanks

[@francleo2002]

Thanks for the tips and explanations for having the proper care of the electrical elements that run the house/boat. There is so much to learn from your videos. Have not seen this advice anywhere else, and it is extremely important, especially in the marine environment. I can't imagine having no motor at all, when in the water/current/winds/etc. that changes constantly, because of a depleted battery!! Yikes!!

[@Clarks-Adventure]

That's nice of you to say.

[@scarol99]

Another excellent video, Clark. Thanks!

[@Clarks-Adventure]

Thanks Steve

[@LanceCustomWoodcraft]

First time visitor, explained my house & starting conundrums w/o the expense of Blue Sea, etc., who pour most finance into marketing, apparently. Thank you! :)

[@Clarks-Adventure]

Good to hear. I hope you subscribe and watch my back catalog. I promise there is a lot there worth learning.

[@davfre8000]

Awesome videos. You guys are my favorite channel.

[@Clarks-Adventure]

Thanks

[@braithmiller]

Excellent, I am surprised how few know of or consider to use vsr to solve basic needs. I extend vsr use especially the adjustable ones to control load shedding, eg not killing house batteries on cloudy days with loads that are not priority. Like a stupid version of computer load scheduling and control. Make water only when above x volts etc. Easy!

[@Clarks-Adventure]

Yes.

[@johnross440]

Thanks Clark, you are on my style of understanding... you are an excellent instructor... really appreciate your videos.. John, Ontario, Canada

[@Clarks-Adventure]

Thanks John. PS we are in Ontario visiting friends just now.

[@coreybabcock2023]

I use a victron cyrix 120 amp bi directional relay to maintain my vans starting battery

[@acromegla]

You guys and your channel are a gem! I recommend your channel so often to other boaters. Keep the good stuff coming.

[@Clarks-Adventure]

We really appreciate that Scott

[@deaconyates2671]

Nice work sir, good video

[@Clarks-Adventure]

Thanks Deacon

[@laurenceholden]

Great!

[@bradfordsimms715]

Great tip. Thanks

[@Clarks-Adventure]

You're welcome Bradford

[@Jacoblejd]

Keep em coming. Love the technical tutorials

[@Clarks-Adventure]

Thanks Jacob

[@garyagish]

Thanks Clark. I was not aware that there was such a device.

[@andreasfink6751]

Very good idea. Makes a lot of sense.

[@Clarks-Adventure]

Thanks

[@annhysell6064]

Excellent video Emily & Clark. Appreciate your knowledge as I am restoring a Tartan 37 (1978). Now I will go back & watch the other parts of this series. Thank you!

[@Clarks-Adventure]

Hope you find some new ideas there.

[@Clarks-Adventure]

After watching that playlist you might like this one. CAPABLE CRUISING GUIDES: kzbin.info/aero/PLsT7_jPsZM5pFpq8RX0oxjibknM2Gz361

[@360unltd]

Couldn‘t find a link to it. Love to get one. Direct search on A had no result. Thanks for the idea

[@Clarks-Adventure]

Follow the link in the description to our Amazon store. I think it's in the electrical tools section but if not there it's someplace.

[@chancederosier3378]

Great info thanks

[@johnnylightning1491]

Well Clark you've got a new sub. I couldn't find the relay in your store but I did find one by searching on Amazon. Looks like a neat device.

[@Clarks-Adventure]

It's usually best to get the dual sending version. Hope you found one. If not you have to put all the charge lines to one battery, usually not a problem.

[@thetraveller3577]

Thanks clarke....useful as usual.

[@douglundy5755]

Cool..good to know

[@TomSvellingen]

Great video, as always😀 Personally I would choose to not have a separate starter battery, if the house bank is large. Historically you might have 1-2 batteries in the house bank, today a lot of boats have 4 batteries or more. The power required to start a “small” diesel engine should be no trouble when shared between 4 large batteries. This way you avoid all the trouble of managing multiple banks, and you can use your battery capacity more efficiently. (If I had no generator, I might have an offline “emergency” battery).

[@Clarks-Adventure]

That's a way to go. I had some really thick plate house batteries. 1000ah of them couldn't reliably start my Perkins 4-108. But with AGMs that's a very valid approach as long as you are confident you won't ever discharge too far. I personally use the "starter bank" for the engine and windless. Both like the thin plate type batteries.

[@stevenjones1359]

Thank you for your knowledge.

[@Clarks-Adventure]

You're very welcome Steven. Thanks for watching, please consider sharing links with your friends.

[@justuscrumlish2209]

Excellent as always

[@Clarks-Adventure]

Thanks

[@marklapierre5629]

Wicked good.

[@Clarks-Adventure]

Thanks. Please consider sharing links with friends.

[@franktartan6808]

Very good info Clark. Keep them coming while your traveling the country.

[@Clarks-Adventure]

Thanks Frank

[@Gypsywind]

Great job with the videos. Thanks man

[@Clarks-Adventure]

Thanks and you're welcome

[@redwood1957]

Nice could you show a schematic? I have an outboard thinking of going lipo4 for houseThanks

[@braithmiller]

Lead + between engine battery and 2 battery combination switch. Vsr in line in this instance. Assuming you have engine start a a constant standalone (as it should be my opinion) some boats setup so you can toast your alternator if you open the switch while running. So one diagram will not work.

[@Clarks-Adventure]

We are traveling just now and pressed for time. Emily said you get animated lions or schematics. Not both this week :)

[@braithmiller]

@@Clarks-Adventure Scheming Lyon icons. 👌

[@energyscholar]

Yes, the isolator is a terrific idea. That said, for another $20 one can put a tiny PV solar panel to charge each battery system. I expected to hear about the combo of isolator & tiny PV panel. A small PV panel that's less than 1% the watt-hour capacity of the battery is safe to directly connect. I.e. If the engine battery is 50 amp-hours that's 50A*h times 12V == 600 watt-hours. 1% of 600 is 6. Thus, directly connect a 5W (or smaller) PV panel to your battery array and you're good to go.

[@SailingAndInvesting]

Great video. I have been thinking of this for a while where I want to connect my single solar panel with charger, but the charger needs to be set for the batter it's charging. Can this be used to charge both chemistries at the same time?

[@braithmiller]

Obtuse yes. Multiple ways are possible. Most will use one vsr between engine and house so your solar on house will not charge engine. Use a solar battery pwm or mppt off the solar panel lead one is enough to split charge between topping engine and house charging. $10+ solution. Some have much more expensive dc-dc solutions.

[@Clarks-Adventure]

If you mean different versions of lead you can pick the more conservative. If you mean lead and li no. You need one of these.www.emilyandclarksadventure.com/bbms

[@bryrensexton4618]

👍!!!

[@theislandretreat4326]

Dude, I owe you drinks before we've even met.....

[@dougstearns6746]

You are a great DIY guy and I watch a lot of your videos. Obviously your very smart and know what your talking about but a lot of times you go down so many rabbit trails I (maybe others too) get lost.

[@Clarks-Adventure]

Well you can always watch the video again Anything to get my view numbers up... Thanks

[@zaceriwata]

Much better without the beard too. Cheers from a Melbourne Australia

[@Clarks-Adventure]

Thanks

[@darrylrjp]

With these, you can raise the disconnect voltage ( 12.8v ) by putting a skotchy diode or normal diode on the earth wire. This with the forward voltage drop of say 0.4v you raise the disconnect to happen at 12.8 + 0.4 or 13.2v, they of course only join when above the 13.2 + 0.4 or 13.6v but that is fine on most cases

[@Clarks-Adventure]

Why would you want to do this? Li on both sides?

[@darrylrjp]

@@Clarks-Adventure Ahh my message was meant to be a reply to those people saying about the batteries being joined until down to 12.8v. the extra diode on the earth line raises the disconnect voltage ( by the doide voltage drop ) if they wanted the starter battery to separate at higher voltage than the device standard 12.8 volts. This was mainly in relation to the stock lead acid starter and AGM house banks most comments were messaging about.

[@josesantin9082]

Great simple explanation on battery systems. I use an even simpler setup that I believe is more reliable and safer. Using a high power schottky diode (1N6392e3 ) in series with a 20A breaker. This combination is wired from the house bank to the starting bank. I picked up this method from the Ample Power website and it has worked like a champ for many years.

[@Clarks-Adventure]

Still a voltage drop with that diode. Not as much but some. .8v I think

[@josesantin9082]

@@Clarks-Adventure A schottky diode has a forward drop of about .6v, and this drop is even less ( according to the data sheet Vf=.4v ) as the current drops to less than an amp . Yes this is not optimal, but close enough. Using the relay, if there is a short in the starting battery, there is no current limiting protection except for the failure of the relay.

[@Clarks-Adventure]

Sure lots of ways to do it. People used battery isolators for years happily.

[@lenwhatever4187]

Thanks for the update. One question... or maybe just comment. You did not really say where the sense pin (post) should be connected to. I guess it should be obvious though that it needs to be on the side where the charging system is (unless it is dual sensing)... maybe dual sensing is more fool proof or even, more desirable. I guess the first question is, which battery should the alternator be connected to? My answer would be the starting battery because the engine/alternator/starting battery are meant to be a unit and depending on the situation, more than one start may be required within a short time period. However, I would think it would be better for the solar panels to charge the house (again, dual sensing please) because your electronic relay still has _some_ drop across the "points" and a solar panel setup that is charging lithium cells, is probably dealing higher voltages too. Shore power charger, which might be much higher current output than solar panels or your voltage controlled relay can handle. (I'm probably missing something as I am thinking this while watching, so not long) Maybe there is a place for a single sense unit connected to the starting battery/alternator and a lower voltage drop diode (.6v seems common enough) from the house side to starter side with a limiting resistor to just allow 2 amps or so charging from house to start side (so starter draw doesn't blow anything , hmm dual sensing bad?). Next question is, what happens if house is greatly discharged? Starter Battery won't allow the switch to close until it's charge level hits switching level. Then the switch closes. What happens now? Depending on the voltage spread for on/off, the alternator _and_ the starter battery start to charge the house battery at alternator rate _plus_ battery rate, that is over 200 amps. Does the switch handle that? or does the house bank pull the voltage low enough for the switch to turn off? (then back on as the voltage is again high enough, acting like a switching power supply? As you have been using the device for some time, it must handle it some how. (same with starter current, but I guess that would pull voltage down below switch voltage anyway) Last comment: A diagram would have been easier for me to follow ;) A diagram would have shown which battery you in your head thought was the right battery for the alternator to be connected to, where sense was, all those things. My little 9.9hp OB starts off my house AGM bank without harm but even a 10 HP diesel would not. Anyway, you patient explanations are much better than I could do because I always seem to expect others to pick things up at the same speed I would. Thank you again. As you can see above, I have probably answered all my own questions.

[@Clarks-Adventure]

There is always a bunch of engineering required to set up charging systems. Any video that tried to answer it all in 15 minutes would fail. Yes you answered your questions fine. Dual is often better. If you use lead on both sides you will find that the internal resistance limits current quite a bit for battery to battery discharge. If you use smallish longish wire to hook these up it can limit their current in a good enough way.

[@Parsonshill2]

Thanks for these informative videos. We have an ACR (Automatic Charge Relay) installed on our boat. It sounds like it does the same thing as the Voltage Sensitive Relay. Is that correct?

[@Clarks-Adventure]

Yep sounds like the same kind of name. There are also battery combiners. All the same but the price. But nothing is cheaper than what you already have.

[@WRMannIII]

Nice video, per usual. Like one of the prior commenters I have concern about the 12.8 cut out voltage. I'm thinking that this will allow the starting battery to remain connected to the house bank as the house bank is used for ship service. Thus the starting battery will be kept in service and giving up charge for ship service until the voltage is drawn down to 12.8 V. It would be better if it were to disconnect at the completion of the charging cycle when the float voltage is achieved (13.2 ~ 13.4 with my Lifeline AGM's) thereby preserving the 'fully charged' state in the starting battery. I have a device on my boat that accomplishes this, albeit at greater cost (~ $ 150) . . . it's a Xantrex Digital Echo-charge. It never directly connects the house and starting batteries. Instead it watches the voltages of the house and starting batteries and whenever the starting battery voltage is .5 ~ 1 volt less than the house battery it will supply a charge current of up to 15 amps to the starting battery. Thus whenever the house batteries are being charged the starting battery will receive the same 3-stage charge. This is especially appropriate when both the house and starting batteries are of the same type.

[@Clarks-Adventure]

Actually leaving a lead battery disconnected allows it to self discharge. The REAL charge in the plates doesn't start leaving until the voltage is below 12.8. There is a phenomenon called surface charge that happens first. So it's better to leave your starter bank connected as long as it's above 12.8. If you add li to the mix all your lead gets heald at float all night. Like it's on vacation...

[@barrellcooper6490]

Clark, Thanks for this! Question: I have a smart charger that uses shore power to charge the batteries independently. It monitors each battery's condition and can charge one battery or the other independently or it can decided to charge both at the same time. Seems like this would interfere with how that functions. I realize if I was away from shore power it could also make things be different. I would appreciate your thoughts on this.

[@Clarks-Adventure]

I'm curious what you have. Usually the battery chargers that make that claim just have some diodes in their charge terminals. Either way it won't make that much difference. If you have lead maybe one battery gets charged longer. It's tough. If you have LiFePO4 you should be running my BankManager and it will manage the li safely.

[@KubotaTee]

Hi Clark. I really enjoy your videos and find them very useful for performing DIY on my sailboat. I recently did a major electrical refit where I completely isolated my starter battery from my house bank. The starter battery is used for my main engine, my generator and my windlass. I only run the windlass when the main engine is running. My charging sources for my engine battery are the engine battery alternator, generator alternator and the aux (trickle) charger on my Victron charger/inverter. The charging sources for my house bank are the Victron charger/inverter and solar. While I love the idea of using all charging sources for all batteries, I’m a little concerned regarding the difference in charge profiles between my starter battery and my house bank. Is there a risk that the VSR will overcharge either my house bank or my start battery? Also, is there a risk of very large amp loads flowing between the batteries if their voltages are quite different?

[@Clarks-Adventure]

Yes the batteries need to be the same type at least chemistry. You didn't say what types of batteries you have. Generally you are safe if you choose the setting for the lower voltage of your two types assuming they are both lead. Your batteries will just charge a bit slower. If you have any Li you can solve that issue easily with my BankManager. Regardless you might like this video. kzbin.info/www/bejne/jqGZpKahaayoq8U

[@KubotaTee]

Clark - thanks for your kind reply. Both of my battery banks are AGM (lead). The starter battery is an Optima Marine starting battery and my house bank is made up of dual 230AH Victron Super Cycle (460AH total). These two battery banks are currently totally separated. The main charging source for the engine start battery is the engine alternator (50 Amp). There is also a trickle charge source for the engine start battery that comes from my Victron Inverter/Charger. The house bank currently has 2 charging sources - the Victron Inverter/Charger as well as 400watts of solar coming through a Victron MPPT charge controller. Although I like the idea of using my engine alternator to charge my house bank (especially during long passages), it is not a smart alternator and therefore does not have the 3 phase (bulk, absorption, float) charging like the Victron equipment. Therefore, will using my alternator (via the VSR) to charge my house bank have a negative impact since it doesn’t follow the same charging algorithm? Thanks for your thoughts / reply to this question.

[@Clarks-Adventure]

It depends on the alternator voltage. Usually the dumb ones just charge too slowly. You can put a switch on the ground wire of your VSR. When off your house won't get a charge.

[@KubotaTee]

My alternator is rated for 50 Amps and it is a dumb alternator - ie, it only supplies current at a fixed voltage. For this reason, I decided to forego the VSR route which would not supply my house bank with the preferred 3 phase charging approach of bulk, absorption and float. I opted to spent a bit more money and went with a 30amp DC-DC charger that senses when my alternator is on and delivers the desired 3 phased charging. This setup can also be used for when I eventually switch my house bank to Lithium as the chargers are all programmable.

[@Clarks-Adventure]

Not so useful for Li as they claim. Before you go Li you should really consider this. www.emilyandclarksadventure.com/bbms

[@abuzman123]

Very good video and helpful. But I have questions. I’ve thought about changing my house batteries to lithium. Don’t lead batteries and lithium batteries have very different charging requirements? What about over or under charging the lithium battery?

[@Clarks-Adventure]

I have you covered. www.emilyandclarksadventure.com/bbms It's how I feel is the best way. Basically the only safe way to charge Lifepo4 without having to worry about low current overcharge. -C

[@SailingwithMaury]

So a point I missed in the video but got in your response to a comment is that the voltage-sensitive relay is only for motor lead to house lead, NOT motor lead to house lithium. Is this correct.

[@Clarks-Adventure]

Correct for a couple of reasons. If you are using the BankManager it always needs lead attached to function properly. And, a vsr can connect when the charge states are very different. That can be dangerous with li

[@eliasmichalis]

Thanks for the great video. One question can I hook a 12v battery to a cigarette adapter to charge it while my boats engine running ? Just to have a spare ready starter battery available always .

[@braithmiller]

If the charge demand is high only being controlled by resistance this is likely to be unsatisfactory if not exciting.

[@Clarks-Adventure]

Yeah I wouldn't recommend it

[@claytonburch5181]

Constant duty solenoid would also work

[@Clarks-Adventure]

Yep, Shure would. But they tend to use a lot of coil power.

[@claytonburch5181]

@@Clarks-Adventure if you use more than a trickle charger you shouldn’t see any difference. Ive put them on a lotta stuff

[@luiscoppelli9077]

Question: You did not say how, and where do you connect the VSR?

[@Clarks-Adventure]

8n the positive line between the house and starter battery. Often parallel to an existing switch that will now be left off for normal operation.

[@matth.2922]

If the VSR cuts out at 12.8v and you have a Lithium house bank, that holds ~13.2v, the relay will stay energized (connected) almost always. Right? This would be the same idea as letting the Li float the Pb house with you BBMS.

[@Clarks-Adventure]

Yes. But the bank manager does so much more.

[@matth.2922]

@@Clarks-Adventure Understood. I guess my question is really about isolating the starter battery to only supply cranking amps instead of pulling from both starter & house banks.

[@Clarks-Adventure]

Yes this does that all by itself. That is after the first few seconds when the voltage drops. If your wire is real big and your Li is large enough the li could keep the voltage up. I have a feature in the bank manager (sort of a software fuse) that can protect from this but if the li is big enough to start your engine without it's voltage dipping below 12.8, what's the harm?

[@Clarks-Adventure]

Mostly this device is to keep the discharging house battery from eating up your start battery.

[@ianwillcock6314]

Hi Clark, slightly different question about charging the seperate starter battery I have on Arabella. On shore power all's fine as the starter battery gets charged however with my current solar panel setup I don't have the solar panel connected to the starter battery just the house batteries. I think when I bought the solar panel the supplier said not to do that !!. My question is, is there a way to have the solar panels I have connected to the house batteries charge the starter battery as well or am I better getting a seperate small solar panel to just charge the starter battery ?. cheers, Ian

[@Clarks-Adventure]

As I remember your starter battery is lead as it should be. Use one of these devices as described in the video. It will work for you and not only charge your starter from solar but from any source and your starter will be floated by your Li at night. It's what I do on Temptress.

[@ianwillcock6314]

@@Clarks-Adventure Hi Clark I've already got one of those devices installed for the lead batteries so are you saying with that connected the starter battery should be getting charged via the solar panels already ?

[@Clarks-Adventure]

If you have it's positive sides connected to your starter battery and your house battery (ground connected of course) and it's the bi-sensing version you should see your starter at the same voltage as your Li.

[@ianwillcock6314]

As I Inherited the gig with the boat and it’s a nightmare trying to see how it’s all connected without removing all the batteries and whatever I’ll see what gets charged next time on solar rather than shore power . Hopefully it’s as you say and I don’t have to do anything 😊

[@Clarks-Adventure]

You could temporarily remove your shore power wire to the starter battery, leaving it on the house side. If the voltage doesn't come down in the starter battery you are good.

[@PrivateUsername]

So, does that VSR actually just power on/off a actual physical relay, or is it just mosfets or something? Seems like you could use one to pass a helluva lot more than 120A/12V if you used that to power a relay bank (in case you run 48 or 96 volt systems or similar, like Sophisticated Lady is doing with that new 6kw alternator).

[@braithmiller]

Specific solid state transistor, not sure if it is a mofsfet good question, never chased this down. You can use a small vsr to control a larger contactor, many designs depending on the system requirements. Look at high power wind generation like household scale many do this. Latching or usually for safety non-latching are used. I have rebuildt power plant scale pneumatic contactors so it is what fits the need.

[@Clarks-Adventure]

I don't think it's worth trying to use one of these for anything but nominal 12v. If you can't find a premade circuit to work for the voltage/amperage you want you could slap together an Arduino and contactor to do it cheap and easy.

[@kevindouglasmiles2324]

Hi Clarke How does it work if you have an emergency parallel switch?

[@Clarks-Adventure]

I don't understand your question.

[@kevindouglasmiles2324]

Thanks Clarke I really appreciate you taking the time to answer my query. I have both emergency parallel and VSR installed by a previous owner but just wondered if the parallel is on whether it interferes with the VSR… in fact should I leave the emergency parallel left on at all anyway?

[@Clarks-Adventure]

I have no way of knowing how your boat is connected up. But, if it's connected as I do mine leave the "emergency" switch off for the vsr to be full automatic. On to just have the batteries always connected.

[@kevindouglasmiles2324]

@@Clarks-Adventure brilliant thank you 🙏

[@fourfortyroadrunner6701]

You left out the most important and dangerous aspect of diode isolators. Because the main battery is the only one being "sensed" this means that if the diode on the main side fails, the main will not be charged, the "sense" circuit to the VR will say " oh let's charge more" and the aux battery will now get BOILED Frankly I believe in "keep it simple stupid." A SIMPLE CONTINUOUS DUTY SOLENOID, keyed by the engine ignition switch, has ALWAYS worked very well in boats and RVs It's just a great big solenoid relay, and you simply wire it so when the engine is running, the batteries are connected. Most all have a 2 post coil connections, and you can wire a small switch in series with that to disable it for some reason

[@Clarks-Adventure]

You are correct. Diodes were a great way to go on 1960.

[@jrmil1454]

Your post could not be more timely. We just replaced our batteries and have been struggling to ensure charging and using the batteries is done correctly. The boat originally had lead for both starter and house. We now have lead starter but AGMs for house. Can this solution be used for lead/AGM combination?

[@Clarks-Adventure]

Yes no problem. All the lead batteries have the same resting voltage 12.8

[@coreybabcock2023]

My relay is switched on and off on the negative side of it i have a switch on my dashboard to do that bought it for 5.00 at a unique thrift store

[@haydenwatson7987]

Hey @Emily & Clark's Adventure , I have a question on these VSR's. The ones that I found have a cut-in voltage of 13.3v and a cut-out voltage of 12.8v. I have an AGM start battery and a 560A LFP house bank. My house bank has never dropped below 13.0v even after several days at anchor so with a cut-out voltage of 12.8v it would never disconnect from the AGM. Can you get them with different in-out voltages?

[@Clarks-Adventure]

Good day Hayden, First off if you are going to mix Pb and li I really recommend you use one of these. www.emilyandclarksadventure.com/bbms As well as the obvious thing it does it is the only device that protects your Li from low current overcharge. Though charge controllers have a li setting, they don't do it right. As far as the vsr goes. That's the right setting as I see it. Your Li will float your pb and keep it happy. It should only disconnect if the li is depleted.

[@haydenwatson7987]

@@Clarks-Adventure I think I will stick with an ArgoFET from Victron which works like a diode combiner without the high voltage drop. I do not like the idea of the LFP "supporting" the AGM start battery. I have had batteries that have failed in that they would take charge forever and still have relatively little capacity. With the LFP supporting the AGM you would not have any symptoms of a problem because the start will continue to start the engine but will be sucking the life out of the LFP. If my AGM requires a constant trickle charge to keep starting my engine, I want to know it. My current AGM start battery is about 10-years old and has never been on any shore power charger, getting all charging from the alternator. It will routinely sit with no charging for 4-months over the off-season and still start the engine on the first try. If it does not, I will replace it. My house and start are totally separate each with its own discharge master switch. The only connection is when the condition is met that alternator output exceeds battery voltage and it breaks the connection as soon as the alternator voltage drops. In addition, that connection is a one-way check valve (diode or FET based).

[@markflint9089]

What do you think about the situation where your starter and house banks are at different voltages, say 12.8v on one bank and 12.4 on the other? If you switch them into parallel connection there will be a massive current flow into the lower voltage bank. I imagine this will have a detrimental effect, particularly on the bank with the lowest capacity, ie, the starting battery.

[@Clarks-Adventure]

With lead it's not that big of a deal as the lead batteries have a fairly high internal resistance. For Li this would be a big issue. This can be mitigated further by wiring this in with longish smallish wire. The resistance will slow that surge of power. (p=I²R). My BankManagerPlus www.emilyandclarksadventure.com/bbms Is careful to only connect banks when it's safe. Good observation.

[@douglundy5755]

I don't see the difference is 12.8 and 12.4 as massive although at various points Clark says that it is.

[@Clarks-Adventure]

During testing there was a point where I had a software bug and my BankManager tried to connect batteries with a large voltage spread (Much more than your .4v). Wires got hot to the point you could smell it and my tester quickly forced the battery banks apart. .4v should be ok I suspect and I don't have the data from our test, as it wasn't a planned test, but likely fairly discharged lead and fully charged li, caused an issue.

[@douglundy5755]

Yes .4 is not large..:)

[@markflint9089]

Assuming an internal resistance of 0.1 ohms, a 0.4v difference this would yield a transfer rate of around 4 amps. Even halving the resistance will only give 8 amps momentarily, so not a problem for lead acid batteries.

[@MotorhomeDIY]

The only issue buddy with a vsr you can’t have a b2b Best option is a b2b with a battery master But again if using lithium leisure and lead starter not all battery masters or maintainers work One I found that work is one from vanbitz in the uk or the amt-12 at widebus the vsr definitely interrupts the set up

[@Clarks-Adventure]

Mine works fine with a VSR, the BankManagerPlus, and it's the only one to not cause low current overcharge that will slowly destroy your Lifepo4. www.emilyandclarksadventure.com/bbms

[@MotorhomeDIY]

@@Clarks-Adventure ok cool … but it’s this the device for a hybrid set up I’ve noticed wildbus sells his own version on this now doesn’t he

[@Clarks-Adventure]

There are a lot of ways to go. We are all captains of our own ships. I designed this from scratch to solve the li charging and use problem the best way possible with no loss (b2bs drop about 20% of their power as heat) The Wildbus unit is just a programmable VSR. Not really in the same class.

[@bigpistol2]

The only potential issue with VSRs are that most fail closed, so if the VSR fails it will keep your batteries in parallel 100% of the time no matter what.....people should be aware and try and find one that fails open so the batteries are disconnected in a VSR fail state.

[@tednottodd]

I’m not understanding exactly which pole to connect the starter battery to. I guess where I’m struggling is if the voltage drops below 12.8 and you’ve connected it to the wrong pole you might shut off the house and left the starter battery to drain. Maybe I’m still not understanding the concept of how this works.

[@Clarks-Adventure]

If you need this functionality just buy one. It's instructions will help you understand it.

[@davidlindquist3113]

Will you place a link to the relay in your Amazon store?

[@Clarks-Adventure]

It's there. I just checked I forget which department but you should find it fairly easily if you look around.

[@Clarks-Adventure]

It's in the tools for Electrical work section. It's by DEWINNER. I can't modify the list or links from my phone. Not at a computer today.

[@davidlindquist3113]

@@Clarks-Adventure Thanks, found in now and ordered it.

[@giterdunpete]

Clark, .........the problem solver before you know that you have a problem.