Has anyone had problems fully charging an AGM battery?

[Seymore Butts]

I'm considering replacing my conventional starting battery with a Bosch AGM battery. I see on the label that it's optimal charging voltage is 14.4 +/- 0.2v

According to my system voltage monitor, the alternator puts out 14.1 volts for a few minutes after starting the engine, then the system voltage drops down to a range of 13.2 to 13.8 volts for the remainder of the drive.

I'm wondering if the AGM battery will always be somewhat below full charge or will it just take longer to reach full charge than the standard flooded battery.

 

[RedSled]

My understanding is that you will need to top it off now and then with a charger designed for agm batteries.

 

[RigidYota]

If running via your alternator as per stock, then it will only charge to 80%. Any reason you also want to use it as a starter and not a separate battery? As a separate battery with a DC-DC charger you would be golden. Im currently looking at a ctek charger for my AGM.

 

[ZiaMan]

Haven't read about battery charging in a while but I don't think a alternator ever fully recharges a battery as it takes higher voltage/amps as you get closer to 100%. You will need a battery charger to keep it as close to 100%. CTEK is good, I have an Optimate6.

 

[riceandpho]

i top it off one a month with a good charger, i do use a ctek for my dual battery setup, also i run dual group 31 battery and a high output alternator.
i like to maintain my batteries here and there.

https://smartercharger.com/products/batterychargers/ctek-multi-us-25000/

 

[YetiX]

I got one of these from HKB: LINK

I believe I got the MK3 version. I don't know jack about electronics, but I have several friends who do and who run them in their 4Runners with AGM batteries and they have had zero problems keeping their batteries charged. I have an Odyssey 31 and I installed the HKB at the same time.

 

[alia176]

I'm considering replacing my conventional starting battery with a Bosch AGM battery. I see on the label that it's optimal charging voltage is 14.4 +/- 0.2v

According to my system voltage monitor, the alternator puts out 14.1 volts for a few minutes after starting the engine, then the system voltage drops down to a range of 13.2 to 13.8 volts for the remainder of the drive.

I'm wondering if the AGM battery will always be somewhat below full charge or will it just take longer to reach full charge than the standard flooded battery.

As you found out already, our charging system can't do a real good job w/o outside intervention. To me, this isn't worth it for the cost of these fancy batteries.

I tried running AGMs (Red/Yellow/Die Hard) in the landcruiser and ended up toasting few of them due to this issue, even with topping them off. So, I run all traditional batteries now (blems that cost $45) from my local Interstate distributor. Batts are consummable items that I tend not to waste big $$$ on. $45 and toss them every few years.

 

[having fun]

I'm considering replacing my conventional starting battery with a Bosch AGM battery. I see on the label that it's optimal charging voltage is 14.4 +/- 0.2v

According to my system voltage monitor, the alternator puts out 14.1 volts for a few minutes after starting the engine, then the system voltage drops down to a range of 13.2 to 13.8 volts for the remainder of the drive.

I'm wondering if the AGM battery will always be somewhat below full charge or will it just take longer to reach full charge than the standard flooded battery.

Check this pig tail out. I've been using for couple months now.
https://www.tacomaworld.com/threads/mike-singer-voltage-booster-groupbuy-feeler-thread.541223/

 

[radlynx]

I use an Exide AGM battery and so far, I don't recharge it. I often drive short distances and sees the charge is okay though. I will check next the voltage next time directly from the battery and see what I have.

I've been using it for 2 years now.

I'm considering replacing my conventional starting battery with a Bosch AGM battery. I see on the label that it's optimal charging voltage is 14.4 +/- 0.2v

According to my system voltage monitor, the alternator puts out 14.1 volts for a few minutes after starting the engine, then the system voltage drops down to a range of 13.2 to 13.8 volts for the remainder of the drive.

I'm wondering if the AGM battery will always be somewhat below full charge or will it just take longer to reach full charge than the standard flooded battery.

 

[blackoutt]

Very timely post. I've noticed anecdotally that my AGM house battery won't charge fully from my alternator and that topping it off when parked in the garage makes it much happier. Then today my starter battery finally gave up the ghost, I decided to swap my house battery to the starting location, and order a second AGM for the house battery again. Now I see that there's known issues charging AGM from the alternator and it all makes sense. I checked out the HKB and poked around, considered building my own "ALT-S" fuse diode, then got lazy and ordered one of these...

https://www.ebay.com/itm/163204446226?ViewItem=&vxp=mtr&item=163204446226

 

[TowMeOut]

Front battery is regular flooded but my "house" battery is AGM. When I'm home the truck is plugged in so the fridge can run off the 110V. At the same time, I've got a Noco Genius in the back that takes care of topping off the AGM. I've thrown the tester on there now and then and it still shows 100% capacity. However, I've only had this setup for about 6 months. Time will tell.....

 

[radlynx]

maybe I need that too to keep my agm battery happy. that link are for those with 2010 and newer model. I have the 2005 model.

Very timely post. I've noticed anecdotally that my AGM house battery won't charge fully from my alternator and that topping it off when parked in the garage makes it much happier. Then today my starter battery finally gave up the ghost, I decided to swap my house battery to the starting location, and order a second AGM for the house battery again. Now I see that there's known issues charging AGM from the alternator and it all makes sense. I checked out the HKB and poked around, considered building my own "ALT-S" fuse diode, then got lazy and ordered one of these...

https://www.ebay.com/itm/Mini-Fuse-Alternator-Voltage-Booster-For-Toyota-FJ-Cruiser-4Runner-Tacoma/163203370792?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

 

[blackoutt]

maybe I need that too to keep my agm battery happy. that link are for those with 2010 and newer model. I have the 2005 model.

Just made sure my link was for 4th gen and FJ but yes order carefully, there's newer versions with low profile fuses and even newer versions with reversed diode polarity. Reviews for this seller on other forums are positive so hopefully all works well!

 

[BackOff]

I have never heard of this before either.

I have had AGM style in since 2011.
Have one in now.

As I start to drive it can go to 14.2v at first.
Then as you drive it is usually at 13.6 (+/- 1).
Resting over night it is 12.55v.

My first AGM lasted 6.5years.
OEM Panasonic was in for 7.

How do you guys know your not charged up to 'full'?

 

[kingofthehill]

I have never heard of this before either.

I have had AGM style in since 2011.
Have one in now.

As I start to drive it can go to 14.2v at first.
Then as you drive it is usually at 13.6 (+/- 1).
Resting over night it is 12.55v.

My first AGM lasted 6.5years.
OEM Panasonic was in for 7.

How do you guys know your not charged up to 'full'?

Mine acts the same way. Ive only had my AGM for about a year. Seems to be fully charging then lowers voltage once charged.

 

[blackoutt]

From odyssey extreme manual, their AGM's are to be charged at 14.1-14.7V (page 9) and a 100% state of charge is at 12.84V (pages 6 and 8). Therefor my 4runner charging at 13.9V on the interstate is just below the required voltage to ever top off the battery and in fact it never reads higher than 12.5-12.6V ever even after long drives. Just to squeak the extra life and energy storage out of the battery it makes sense to up the voltage a bit.

http://www.odysseybatteries.com/docs/us-ody-om-012_1014.pdf

 

[YetiX]

From odyssey extreme manual, their AGM's are to be charged at 14.1-14.7V (page 9) and a 100% state of charge is at 12.84V (pages 6 and 8). Therefor my 4runner charging at 13.9V on the interstate is just below the required voltage to ever top off the battery and in fact it never reads higher than 12.5-12.6V ever even after long drives. Just to squeak the extra life and energy storage out of the battery it makes sense to up the voltage a bit.

http://www.odysseybatteries.com/docs/us-ody-om-012_1014.pdf

^^ This.

 

[Seymore Butts]

What is the long term effect on the rest of the 4R's systems when you modify the voltage output higher than OEM spec?

 

[YetiX]

What is the long term effect on the rest of the 4R's systems when you modify the voltage output higher than OEM spec?

My understanding, again from my friends who actually know about this stuff, is that there should be no long term effect. The increased output is well-within the alternator's capability so it should have no effect. The stock limit is put in place with a standard battery in mind. If you were putting 14.1V to a stock battery, it would fry it. So Toyota limits the output to 13.7V or whatever it is. However, the alternator is easily capable of producing the additional .4 needed.

 

[grapemilk]

How do these plug-in fuse adapters work? Do they present a false low voltage to the sensing wire of the alternator to force it think it's not providing enough voltage?