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AGM batteries and charging volts

cocodataco

cocodataco

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Hey guys wanted to see what everyone was doing to get the max volts to charge their AGM batteries.

I have done some searching on TW/google and it sounds like us guys with the 3rd gens don't have a way to boost our alternator voltage to charge AGMs. I will be putting a group 31 in my rig over the next few weeks and already own a battery charger that supports AGMs. But I would like to do something more than just hooking it up to the charger every month or so..

For reference the Odyssey AGM batteries needs anywhere from 14.1-14.7 volts, while our rigs output range maxes at 13.8v. Unlike the 2nd gen rigs that have an ALT-S fuse which you can place a diode to boost the volts our 3rd gens are ECU controlled.
 
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So it goes in-between your alternator and spare battery. It will charge your spare battery at 14.4v. I have a dual battery voltage meter on both of my batteries and have had no problems with the alternator sufficiently charging the starter battery. Its been in my truck for over 2 years and the starter battery voltage is still holding 14v.
 
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Odyssey extreme
C28753FE-19A9-47F5-A947-168335827894.webp
 
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I'll be running a single group 31 in my truck so I don't believe the DC to DC charger would work for me. Thanks tho looks very interesting
 
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cocodataco said:
I'll be running a single group 31 in my truck so I don't believe the DC to DC charger would work for me. Thanks tho looks very interesting
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Yeah, that DC to DC charger solution definitely answers a question you did not ask. KD Max can make a tune for you that basically amounts to an "AGM charging update." I cringe at the thought of paying hundreds of dollars for .5 voltage increase though. I have a nice agm battery.
 
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You or a tuner you use can bump the charging voltage up with VF tune. A nice bonus if you are tuning your truck. It's easy, I have done it myself.
 
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ForTheWin said:
Yeah, that DC to DC charger solution definitely answers a question you did not ask. KD Max can make a tune for you that basically amounts to an "AGM charging update." I cringe at the thought of paying hundreds of dollars for .5 voltage increase though. I have a nice agm battery.
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I agree with you about the thought of spending hundreds of dollars for that however, sometimes if you wanna do things the right way instead of half assed, it will cost money.
 
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XxMagpulxX said:
I agree with you about the thought of spending hundreds of dollars for that however, sometimes if you wanna do things the right way instead of half assed, it will cost money.
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When you get a tune it's for a lot more than increasing the alternator output. It was literally an afterthought when they discovered the settings for it. It is very handy though.
 
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XxMagpulxX said:
I agree with you about the thought of spending hundreds of dollars for that however, sometimes if you wanna do things the right way instead of half assed, it will cost money.
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I contacted a tuner (OV tune?, can't remember) He was like a salesman shill, when I had told him exactly what I wanted. "you're gonna love what it does to your tacoma!". (oh goody, it will fool the accelerator into thinking I press the the pedal down harder and deeper than I did). I don't want all that. I just wanted little more than half volt increase output from the alternator at idle (then stay that way throughout the rpm band). I brushed aside the whole project because of that one exuberant tuner guy. How does someone do it themselves?
 
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Optima specifies 13.2 to 13.8 float charge and up to 15.6 for rapid charge.

Odessy says the same except if the battery is deeply discharged you need to go 14.1 to 14.7.

-M
 
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Alternators aren't chargers. They're maintainers. They aren't doing the work of reading charge level and changing the input to charge vs float. If you want to add a charger it's probably cheaper than getting a tune and will be much better for the battery. But I don't know if that would be good for the rest of the electrical system. So the tacomas put out the right voltage for maintaining an AGM, provided it isn't significantly depleted.

These Noco charger/maintainers are probably good for long term maintaining and charging from depleted: https://www.amazon.com/dp/B07W3QSMF9/?tag=tacoma3g-20

-M
 
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So funny you mention that.....I just picked up a Genius 10. I LOVE that thing. It works as advertised. I am considering getting a battery tender at Costco for AGM batteries to keep on my truck.
 
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StormRnr said:
Alternators aren't chargers. They're maintainers. They aren't doing the work of reading charge level and changing the input to charge vs float. If you want to add a charger it's probably cheaper than getting a tune and will be much better for the battery. But I don't know if that would be good for the rest of the electrical system. So the tacomas put out the right voltage for maintaining an AGM, provided it isn't significantly depleted.

These Noco charger/maintainers are probably good for long term maintaining and charging from depleted: Source: https://www.amazon.com/dp/B07W3QSMF9/?tag=tacoma3g-20


-M
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Correct, the voltage regulator handles the voltage part. The stock system will not ever charge an AGM fully, meaning you will never be able to utilize its full potential and its life will be shortened. A charger works, but not for my needs. I already had the OV tuning hardware, so that was an easy one for me.
 
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May I get some advice for a Tacoma Off Road replacement battery? Oddly enough my dealer confirmed that Toyota does not sell an AGM TrueStart battery for this vehicle. I'm leaning toward an expensive Optima YellowTop D35 because Optima claims that their battery does not need a higher voltage charge from the alternator to maintain them like some others do. I'd love to save some money by getting the Duralast AGM but I cant find charging requirements for it. I use the truck for towing/hauling/camping and light off road, sometimes in remote areas. If you can point me to charging requirements on a good battery or just tell me about good or bad experiences with batteries, I'd really appreciate it. Thanks.
www.optimabatteries.com

Tacoma Voltage Booster?

Do you need a voltage booster in your Toyota Tacoma if you use an OPTIMA battery?
www.optimabatteries.com www.optimabatteries.com
 
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a Toyota tech friend highly suggested not to mess with the internal voltage settings with a tune. It compromises the longevity of the trucks various ECU’s. The computers don’t like see such high voltage. Our alternators are capable of outputting 14.3 when needed. Use a tender 👍
 
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djw.pro said:
a Toyota tech friend highly suggested not to mess with the internal voltage settings with a tune. It compromises the longevity of the trucks various ECU’s. The computers don’t like see such high voltage. Our alternators are capable of outputting 14.3 when needed. Use a tender 👍
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Any specific model of Battery Tender better than another?
 
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