4Runner Voltage Booster Fuse for Under $10 to Properly Charge Your AGM Battery.

[@Mudog715]

Three big facts people are missing here (oversimplifying for brevity): #1 the charge spec on that battery (14.4-14.8v) is the MAX the BULK stage of charging and typically spec'd at 85°F. The MAX bulk charge rate allowed quickly drops as temps rise AND as the battery state of charge (SOC) nears 100%. When >120°F, the maximum allowable charge rate typically drops to 14.0v or less. Typical engine compartment temp on a summer day with A/C on can easily exceed 210°F. Charging at too high a rate will cause the battery to offgas and possibly vent. On a flooded battery, you can add back water that boils off. On an AGM, once it vents that loss is irreversible. If you push it too far, dried out cells could enter thermal runaway and cause the battery to get hot enough to melt the case (I've seen this on a couple Optimas over the years). #2 the typical Toyota alternator, like most internally regulated alternators, is "temperature" compensating. In other words, the set-point voltage (target charge voltage) will vary according to ambient temp. When you first start on a cold Winter morning the charge rate could be 14.7v initially, first start on a hot Summer day may only be 14v, and as the engine compartment warms that will continue to drop, typically settling around 13.5-13.8v (lower v the hotter it gets). This is to prevent overcharging a hot battery and damaging it. If you "fool" the regulator into boosting the output by a constant 0.7v, it's possible in the winter to get 15.3v or higher...that's high enough to stress a lot of the electronics in the vehicle and shorten lifespans. #3 You are assuming the voltage displayed on your scan tool is accurate. IT IS NOT. The only voltage that matters as far as the battery charging is THE VOLTAGE MEASURED AT THE BATTERY. The "ALT-S" fuse serves to provide the regulator with a sensing voltage that is as close to the actual battery voltage as possible. In my own tests, I've seen ScanGauge, ODB2 adapter and "consumer" digital voltmeter readings in the vehicle 0.5v lower than what a lab-grade calibrated meter shows at the battery terminals. So while you think the system voltage is 13.8v, it's actually closer to 14.3-14.4v at the battery. And as I previously stated, the voltage at the battery is what matters. As long as it's seeing a cold charge north of 14v, tapering down to 13.5-13.8v (AT THE BATTERY) as temperatures rise and battery becomes fully charged it will live as long as your environment allows (automotive batteries generally to last longer in cooler climates, as do batteries that don't live in the hot engine compartment). Heat is what kills batteries and a sure-fire way to kill one is overcharge it while it's hot.

[@timdunlap7565]

Gave you a thumbs up because you sound like you know what you’re talking about. Thanks for saving me $8 and potentially a lot more!

[@switchman956]

I like the idea of the heat shield, installed an AGM battery in my truck and I will monitor voltage and cranking amps(have battery tester) . I’m not changing out the signal fuse, I will only be charging battery with AGM charger at home once a month while truck is off.

[@peterolfert7477]

Great post Mudog715. So, I assume you recommend against this work around?

[@320dak]

I believe you are spot on! I live in Phoenix and most lead acid batteries, from Costco, last only around two years. This is because of the heat. A lot of people do not take this into consideration. It is the heat that kills, not the cold. Bought the X2 Power battery 2 1/2 years ago. So far so good! Time will tell.

[@Paul-sk2pc]

I didn’t buy the “need” of boost charging AGM battery when I first saw the post at ih8mud forum. These x2 came with 5 years warranty under standard charging condition which is plenty long. Boost charging “may or may not” extend battery life a tiny bit but you are stressing everything else in the electrical system include alternator. Squeeze another month or two out of a $200~$300 battery is equivalent of saving $20 in 5 years.

[@whiskeymountainwood]

For anyone wanting to know, this works perfectly for 2nd and 3rd Gen Tacoma trucks as well.

[@craftmansnapon8035]

I have 14 Tacoma I’ve tried it and works when Engine is cold but hardly A difference once the engine is warmed up.. I’m wonder 2014 Tacoma has a smart alternator where it can take the diode. The big difference is only when when you’re at idle

[@McFlysGarage]

3rd Gen Tacomas do not use a diode for alternator voltage. It’s all through the ECU

[@norbertoespinoza5158]

Just did it on a 2004 Lexus is300 voltage before was 13.8v. after diode it's at 14.4v it also works

[@roblinprasad528]

Your video had all the answers i had about the diode. I have a 02 lexus ls430 with aftermarket audio system. Have a yellow top optima under the hood and xs power d925 battery in the trunk. Before installing the diode at idle voltage was at 13.7 afterwards sits at 14.2 volts. Thanks for the video. Anyone wondering if this works for lexus ls430 yes it does. 😊 bass now is more deeper.😅

[@spelisha]

Amazing video man Saved me so much time and the life of my AGM I just bought Thank you!

[@WEESHBONE]

Thank you for this smart charging modification! Very grateful 😊

[@7overland514]

I like the way you do things. Just do it, but keep an eye on it. I do however have a concern about the voltages. I see zero problems when everyday driving especially if you are drawing current when the vehicle isn’t running. But AGMs are prone to overcharging, and on a long trip, this could be a problem. 14.6-7 is great for bulk charging, but once fully charged, you would want to drop to a max of 13.8 for float charging. Your system doesn’t system to address overcharging. On a long trip constantly pumping in 14.6 could lead to overcharging.

[@albowrx]

Can't you say the same for stock setup one. stkck battery?!

[@4estrnr472]

@@albowrx Stock battery is lead acid not AGM

[@ronaldchan3401]

@@4estrnr472 AGM are also lead acid, please get your facts right.

[@VINNY5674]

People read the specs on these agm batteries and how wonderful they sound. Newer cars that start and stop when in traffic require this agm technology as these batteries can take that kind of punishment. Now these newer car usually put the agm in different places like the trunk or under seat why because agm batteries don't like the heat from the engine. The heat will wear the battery over time. Next the charging system of the vehicle lot's of alternators don't communicate with the agm battery properly causing over charging and eventually wearing down the battery. Now voltage spikes and drops can be a potential problem with the alternator and agm battery. If your vehicle came with a flooded lead acid battery you replace it with a lead acid if your vehicle came with an agm you replace with an agm. AGM batteries are great for let's say my trolling motor on my boat or as my second battery to power a power converter during camping as you can drain the battery completely out and recharge it with out damaging it. (always keep your battery charged up after draining it) So installing an agm that's not recommended by the manufacturer of your vehicle is simply at your own risk. My advice here if from a person who has experience installing car audio, led light bar's and all kind of electrical projects on vehicles ,boat's, homes... ETC

[@JohnG1000]

Lol lead acid isn't a good idea for car audio second battery and if you have a second battery it should be the same as your under hood battery so it only makes sense to change both vehicle batteries to AGM .

[@JayM026]

Just performed this mod on my 18 4Runner, Worked like a charm! THANKS!!

[@issaal-shukaili1328]

U put diod fuse ? And how the battery preform before u put the booster ?

[@cheesem0nkeys]

Thank you for this. I was tempted to buy the premade $70 résister boards people have made but didn’t want to reverse engineer them.

[@ninja-vanish8086]

I'm going to try this on my ford flex using the ford diode. I have amplifiers that need more voltage than what is regulated. 14.4 would be perfect. Its currently sitting at 13.1 I hope it works 🙏

[@brucesimpson8579]

Just an FYI that on a 2021 Tundra the arrow of the GM fuse will need to point towards the front of the vehicle (i.e., left), otherwise the battery light will come on if the fuse is inserted the wrong way.

[@DjR3aper]

Does the tundra still say ALT-S my 21 camry only has BAT S. My 2014 & 2012 Camrys both had ALT S

[@markwhitney4047]

Thank you man so much I've been trying for months to up my volts but thanks to you I did that

[@TwistedJake]

Glad I could help. I'm 8 months into this mod and still working great.

[@issaal-shukaili1328]

@@TwistedJake thanks for the video , Did u find any improvement compared. With out the fuse ?

[@KauaiMoney808]

Perfect video. Just installed the same diode but with a fuse jumper so I didn’t need to shave to fit. Upped my 2014 4runners voltage by .05-.07 volts

[@MarkMollat]

Awesome! Thanks. For something as simple as this I find the ArcLight way to expensive!

[@josea.garcia3994]

Great video!!!👍👍👍 It was very informative!!! I have a 2012 TOYOTA 4RUNNER SR5 LIMITED that I would love to do the same voltage booster upgrade on it!!! I use nothing but AGM BATTERIES on it myself!!! I currently have a XS POWER D3400R battery that I been using since June 2017 in my 4RUNNER with no problem at all!!! But I always wondered why my voltage was running between 13.4 to 13.8 after letting it idle down to it's curb idle!!! The cold start voltage is in the 14.2 to 14.6 range but then it gradually drops down to 13.6 to 13.8 once it's fully warmed up and reached it's curb idle!!! So with this voltage booster upgrade does it mean that my 4RUNNER should always be in the 14.2 to 14.4 range regardless of the outside temperature and regardless of the amount of accessories that im using or is that statement totally incorrect and why??? I have been told by mechanics that the voltage readings are affected by the outside temperature and by the amount of electrical accessories that you use in your vehicle!!! The readings that you showed on that monitor screen after the voltage booster upgrade, were without any accessories on like the radio, A/C, lights and so forth correct??? The accessories being on do make a difference I believe in the final readings if I'm not mistaken!!! Your help to understanding how this voltage booster upgrade works with or with out accessories on would surely be appreciated!!! Thank You!!! ✌️✌️✌️

[@christ-runnerdavidhettenba4029]

Well it’s almost May how is it working for you. I have a 2018 4Runner with a agm battery and am looking into the charging of it. No one told me about the need of 14 plus volts when buying the battery I think they should have. And thanks for the video it’s a great video great job. Thanks for the help.

[@joelslaughter9056]

I’m about to do this to my 2001 Tundra. I have 2 103ah agm batteries for my stereo install. Running a 300amp alternator & unless it’s 1200+rpms, it will charge just barely at 13v. Just ordered from eBay.

[@xBLACKxOPSxSECRETSx2]

Did it help? My camry had that problem with a 320a alt... I returned the alt cuz cudnt figure it out:/

[@joelslaughter9056]

@@xBLACKxOPSxSECRETSx2 I ended up adding 2 diodes running in series to the sensor wire from the under hood fuse box. Mine was white. I have a 45ah Cmax battery & I charge now at 15.7-8v while driving & 15.3 idling.

[@xBLACKxOPSxSECRETSx2]

Your 300a alt is pcm controlled right?

[@joelslaughter9056]

@@xBLACKxOPSxSECRETSx2 yes. But adding diodes at the sense wire at the fuse box puts resistance at that wire making the PCM think it’s under demand & will charge higher. Add them 1 by 1 until you get to the voltage you need

[@thetruelifelover]

Where or what brand of alternator did you go with? Im looking for one and I found 3 possible companies that I'm researching to see if they are legitimate a good product.

[@YouTubeMaster1611]

Doesn’t your electrical system run off of the alternator while the engine in running? Will the above factory voltage damage the electrical system?

[@rowboyto156]

no unless you go over 15.8v

[@joecantu5252]

It really works, Great video.....

[@secalcavazos3204]

Correct me if I'm wrong but 11.9 rest is quite a bit low wouldn't you say? I rest a full volt more then the 11.9 not to mention I would go crazy seeing that... maybe I'm crazy but I'll have a look @ my grounds to make sure I getting my full charge. Cool video either way.

[@itsSpecialSteve]

which head unit are you useing? i like how it has voltage info

[@griffinpk1]

Great explanation. New subscriber

[@XXxBMXBOSSxXX]

I have a 2005 sequoia. Also have the same alternator s 7.5amp fuse. Will this work for mine aswell??!! Just ordered one can't hurt to try it. Also have 2 agms that need proper charging!

[@nathanrice1796]

Because it's only a diode that's shaped like a small fuse, it will not blow if there is more than 7.5 amps going through it. So therefore, it's slightly unsafe. Although there's a very small chance that that would ever happen.

[@peterolfert7477]

Awesome video...thanks! What's the bluetooth system you are using to monitor voltage?

[@TwistedJake]

Carista for the BT adapter linked to an app called Torque on my tablet.

[@arnoldsalazar5851]

Will this mod work any vehicle? I have an 05 Honda accord with a 2.4 and I’m upgrading to a group 34 AGM battery, I’m doing this because I have as sound system and I want the accessories to get the most from the charging system. Thank you man.

[@vladd5291]

Thanks for this! The same should work for group 31 AGM battery too, right?

[@jordanwhite3152]

I have the same battery in my 2017 Toyota Tacoma. Can I do this to my fuse replacement for it?

[@YouTubeMaster1611]

What are you using to monitor your voltages? I did this mod a year ago and I have no issues yet. Knock on wood! I’ve done lots of long trips and no over charging issues that I aware of.

[@rodmyyk]

Thanks, this worked for me...

[@SlamryCamry19]

Will this work for a 2019 Camry im trying to increase my voltage to 14.4 for charging lithium batteries for my audio system

[@NorthBayDisc]

Hey Jake, what is the system you using to monitor you voltages? Looks like a slick app. LMK

[@james10739]

When you said gm part I just remembered my moms car charges at like 15v because the battery is under the back seat and supposed to be an agm I figured with the extra length and I knew agm were a little higher but ya I had seen that diode symbol I assumed it was a diode for some actual reason not to drop a volt or half

[@variomario9620]

Will this work on the 4th gen 4 runner

[@mikebates4815]

Any update on the condition of your battery? Thanks

[@rippspeed1]

Did the mod only getting 14.1 max and when down to 13.8 ... Battery is 2 days old. Does that mean battery is fully charged ???

[@rippspeed1]

@@xxnatas69xx thank you ... The mod has worked ... And no issues with the battery at all. Thanks for the informative videos

[@rowboyto156]

this also works on vehicles with the 1mzfe engine. the arrow face the other way for it to work. now my sound system is hittin hard

[@cheesem0nkeys]

One consideration with this is does it take a fuse out of that circuit? So unprotected circuit?

[@tee228]

Is it the same for a 4th gen 4R?

[@bdc211]

right!!!! ima try it... but i just changed to a 240 amp alternator.. i believe the voltage reg is in the alternator... idk.. im figuring the system is regulating as well.. hence the need for this fuse... 🤷 im going for it let me know if you tried it.. thanks!!

[@tee228]

@@bdc211 i have a 240A alt too for my sub and amps. this mod works for 4th gen. went from 13.8 to 14.5

[@bdc211]

@@tee228 sweet!!! thanks again!! 👍

[@sansantos75]

Wow 🙌! 👏 😮

[@s302jzget]

Would this mod charge a lead battery any faster?

[@HarpreetSingh-sr6eb]

Tried it on my 2015 IS250 it didn’t work. It melted in 30 seconds and I had to quickly turn off the car and pull it out with a nose plier🤦‍♂️. Factory uses a 20 amp fuse and actually looks like there is a load connected to it not just a signal to ecu. I tried 5 diodes in parallel (double size than GM) they also started over heating after 3-4 minutes and voltage only increased from 13.6 to 13.9. Am running an aftermarket 250amp alternator but am low on voltage for my dual AGM batteries. Any help will be appreciated ..

[@basshead100]

please drop the link where to buy

[@anthonyzarraga2993]

This may work for a toyota camry right??

[@mikhailzhidko2252]

I have 06 Lexus GX470. Will the same GM fuse work for me? I got dual AGM battery setup.

[@ollyolyoxenfree]

yes

[@johnrommelt6560]

So long term Is everything Working Properly?

[@TwistedJake]

Yes. Been well over 2 years and all is well. That being said, I was recently sent a switchable hi/lo charge fuse purpose built for this and I plan to swap it in and try it. The downside is they are about 10x the cost of this OEM GM fuse. The upside is you retain the fusible protection aspect I believe. I need to read a little more before swapping and making a new video.

[@johnrommelt6560]

@@TwistedJake So it might be safer, added protection?

[@johnrommelt6560]

@@TwistedJake What if you have regular battery and do this Mod?

[@johnrommelt6560]

@@TwistedJake what if you use it with regular battery?

[@TwistedJake]

@@johnrommelt6560 I don't know that there is a benefit with a regular battery.

[@Matt-tf1wz]

Just wanted to add something here, on the 2020 and up the alts fuse is in a different location, also I don’t no if they have changed something in the programming but after Installing this diode it’s only hitting 13.7 13.8 so not sure what’s going on but I’m gunna drive it around a bit and see what happens, I’ll update

[@alwaysreal74]

Would this work on 2005 Yukon Denali ?

[@sunapeelakers]

Hey man, it’s been about 9 months, how’s this holding up? Just did it to my 2011 that I just put an optima red top in. Don’t want to ruin it!

[@TwistedJake]

Still running strong. Just for curiosity a few weeks ago, and while trying to diagnose an alarm issue, I reversed the fuse and sure enough I got a bunch of warning lights. Flipped it back the regular way and they cleared. Bottom line, no issues at all.

[@sikandinc]

Is the GM product a fuse, a diode fuse or just a diode? I do not see it being fused in some of the material I've seen.

[@IAnonymousl]

any issues?

[@richanderssohn7318]

Nice MicroTech

[@TwistedJake]

I believe it's pronounced Benchmade.

[@richanderssohn7318]

@@TwistedJake :)

[@TheRealitarian]

Anyone know if this works on 3rd Gen Runners?

[@Gunnisack21]

Can you explain the doll looking legs in the background?

[@TwistedJake]

Yeah, they are the legs of a doll.... Check the pics on my instagram, it will make more sense. Maybe....

[@Docfrazier81]

Shiiiit... I'm going to try this on my Tahoe, that damn thing drops as low as 12.1 volts at times.

[@TheMellemel86]

Does this work with the 2021 4Runner?

[@Silvia0073]

No, only up to 2019.

[@FONTJA]

@@Silvia0073 do you know of a solution for the 2020+ 4Runner

[@YouTubeMaster1611]

One year later, has anyone had problems with this modification?

[@TwistedJake]

None what so ever.

[@YouTubeMaster1611]

@@TwistedJake I did this mod also and I haven’t had any issues either. Just wanting to see if anyone else had. Thanks for your help!

[@sogbryan6633]

@Twisted Jake **Something Very Wrong with Those Numbers** Working voltage for a battery is 12-12.6v. A battery going from 12.6v to 12v is equivalent to playing your car stereo full blast for 3-4hrs+. In other words, your battery went from completely full to 95% dead, over night. Something wrong with the volts reader or you have a very bad draw happening somewhere.

[@TwistedJake]

The volt reader is straight from the ECU via obd2 port. I've gone days without starting the rig and never a problem so I doubt there is a draw.

[@sogbryan6633]

@@TwistedJake My main point is, 12volts is a dead battery so somethings wrong. @12volts, there's only 5% of the batteries workable power left, so the battery is 95% dead. Again, I am simply giving you a heads up that somethings wrong. Do a test with a multi-meter. With the vehicle off, turn your lights on and play your stereo for a few hours; then shut everything off, wait 10 minutes and check the standing voltage. Do this until you've drained the battery down to 12volts, then try and start you vehicle. Very unlikely that it will start.

[@rippspeed1]

Any updates ???

[@TwistedJake]

Everything working as it should. No hiccups at all.

[@cory89183]

Doesn't work unfortunately only last at 14.2 for 15 min then back to 13.8

[@sikandinc]

What SOC was your battery at? I'd assume this is a regulated source so if it senses your battery is fully charged it would dial it back.

[@ls_gill1582]

Did this turn on your battery light?

[@TwistedJake]

No. Unless you install the fuse backwards.

[@ls_gill1582]

@@TwistedJake 🤔 it’s on either way I place it.

[@TwistedJake]

Ah, then something else is wrong. My battery light only comes in if I put the fuse in backwards. It has never came on otherwise.

[@ls_gill1582]

@@TwistedJake thanks for the info! It’s weird that’s the only thing I touched and I didn’t even have the light on. I’m seeing the improvements but the light is on.

[@lilijuanvelasco7310]

Did you figure it out? The same thing just happened to mine.

[@RickeyLawrence-nr7ov]

Battery light stays on

[@dragonflymoxie5646]

The diode needs .6v to forward bias (turn on and flow signal)…. Thus the computer thinks it needs to supply .6v more….. simple.

[@_mymygee5393]

what if you just leave that alt s fused un plugged?

[@brokeassgarage]

You’ll definitely get a check engine light 🤣, and a code for “system low voltage” in every module in the vehicle.

[@secalcavazos3204]

I like to just keep it nice trickle charger prominent health to my car so when I get home and I remember just plug it in overnight make sure my battery state topped off the way they need to be because the alternative can't do that and I mean good becomes systems it's all about the amperage So for the guy with the 300 amp alternator and three AMG's I would've left well enough alone

[@craftmansnapon8035]

Do you think the alternator will work harder thus more voltage means more heat will wear out the alternator. This is my theory. I have tried this in my 2014 Tacoma and have little success. I mean it works but at times it will be at almost the same as the 7.5 fuse originally. It seems as if my alternator is a smart alternator where it can adjust it self back to specs like the 7.5 fuse. About a .1 .2 number different

[@TwistedJake]

No, I don't think so. Alternators are capable of so much more power than we "allow" them to create. That is why we run voltage regulators. While asking it to produce marginally more voltage than it did from the factory may technically put more wear on it I doubt it is even a measurable amount. Remember, it is also only producing that "extra" voltage when the battery needs a charge or there is a draw calling for it. Once the battery is topped off and you aren't running anything calling for a lot of voltage it is just creating the minimal power it always has. It isn't working harder all the time.

[@chupo4putin]

i have a safer solution. my altenator is primary source of power for my 2xAGMs in winter with solar charge controller when there is sun so it charges correctly. batteries for 2 years now work good with really good capacity results. probably maxed out. im not an expert at this so im not putting any replacement instead of a fuse.

[@GasBrakeSim]

Did we really have a 15min video of how to install a fuse ?lol

[@TwistedJake]

Yes. Thanks for watching and commenting.

[@GasBrakeSim]

@@TwistedJake this ‘overlanding’ bonanza needs to stop . But have a great day . Off the grid now .