AGM BATTERY CHARGING - ALTERNATOR VOLTAGE BOOSTER

What AGM do you have? Would be interesting to know what your battery voltage is with the engine off, that should give you a good idea if it’s fully charging and indicative of your battery health.

 

It's the Advance Auto house brand (can't remember what they called them) AGM before they rebranded to DieHard. Probably the same exact battery. I haven't checked the battery when shut down for a long time but I see voltage on my ScanGage 2 after I shut it down and it is ~13V... but that surface charge will go away over time and it will settle a little lower. My real test of battery health is how she turns over when it is 12 degrees outside. When it slows down appreciably from how it starts when warm it is time to get a new battery.

And a positive note, batteries on Tacomas seem to last a long time, far longer than I am used to getting on other vehicles. I bought my truck November 2008. The OEM battery went ~7 years. Current AGM is almost 6 1/2 years old.

 

OK, I was getting curious, so I went down and checked my battery voltage now the truck has been shut off for a couple hours. It is down to 12.2V, which is not good. That equates to a ~50% state of charge. Not sure if that is the AGM not getting enough voltage to fully charge issue or if it is just because it is old. I will put it on an external charger one of these days on the AGM cycle and see where that takes the charge level to. I may have to go back to the diode after all. Or maybe I am just almost due for needing a new battery? We'll see. Damn it all.

 

I think I read somewhere, that deep cycle doesn't exactly mean deep cycle.
My dad accidentally destroyed one of my X2 when he cleaned my truck from the inside and accidentally turned the light bar on. The battery was toast after.
Also the solenoid dual battery switch doesn’t protect the battery from deep cycling, that’s why I then also invested in a cteck dual battery system which monitors the auxiliary battery and disconnects the consumers when the load is getting too low.

now I am running since three year without issues and without having to think about it

 

Interesting, I think putting it on a charger with an AGM setting is a good idea to see if there’s any recovery.
My OEM battery is losing capacity after only 2 1/2 years but I attribute that to not driving it much these days, it’s sometimes a week or two before I drive it so it’s left setting. Voltage is around 12 to 12.2 after sitting that long. Charged back up when driving but I noticed it was craning a little slower the other day, first time that’s occurred. Been researching AGMs but so far I’m leaning to getting a regular battery, if it lasts 3 -4 years I can get two for the price of one AGM and not have to worry about alternator voltage. I also don’t really want to add stress to electrical components, lights etc. by jacking up the voltage. Still researching though.
For comparison the battery in my Accords on OEM batteries have lasted up to 7-8 Years, but if they set a while it’s down to 3 years, as I’ve seen since working from home since 2020.

 

Yeah, I am leaning towards going back to a flooded battery in my Tacoma. I really don't want to jack the voltage and risk blowing another alternator since changing that was unfun. I did use an OEM replacement alternator so hopefully it is fairly robust, but it was also $. My original Toyota battery lasted 7 years but this truck is my daily driver so never really sat for long periods. Could get another one of those or the DieHard Gold from Advance. Probably not until fall, however, since even with this low SOC the AGM easily starts my truck and with warmer weather coming it should easily survive till fall.

The other thing that can mimic losing capacity is if all you do is short trips. The battery never really recovers all the charge used for the starts. Repeat that over a longer period of time and it will drop down to what we are seeing from full charge that IIRC should be ~12.7 V for flooded and ~12.9 for AGM. Not exactly sure about those numbers... need to go look them up again. I've read that some folks who only make short trips or let their cars sit for long periods also use the diodes or other boosters to get as much charge as they can in the short trips.

I'll post back after I have charged this thing.

 

So for those running AGM (of any type), but actually DON'T have any deep/constant cycle needs (versus usual start/run), have you actually found the AGMs to be cost effective - ie. divide price by how many years they last to see 'cost per year' compared to standard flooded?

 

Hard to say... yet. Because my AGM is still going. And the premium for an AGM is only like $20 or $30 unless you get an Optima or somesuch. But the Diehard line and similar are just fine IMHO and the AGM will likely be cost effective.

Just reviewed my maint records and I was a bit off on some stuff. The OEM battery lasted 6 years and 3 months. I installed the replacement Autocraft (old Advance Auto brand) AGM battery in January 2015 so it is currently 7 years 2 months old. I just put it on my NOCO charger in AGM cycle... interesting that the NOCO indicated that it wasn't all that discharged... the 3 bars were lit up and the green final indicator started flashing pretty soon after starting the charge. I'll let that go until it goes solid and enters maintenance mode then let it sit for awhile and check the voltage. Bottom line, I am not going to worry about the battery anymore until it fails.

 

Just curious about this but back to what davidstacoma was saying, as per the Odyssey AGM battery intruction manual when doing a full recharge of the battery the potential should be the 14.7V and once the battery is fully charged (6-8hrs) then the potential should be a 13.6V float charge. The way I see the voltage regulator being handy is when you want to give the battery a full recharge and there isn't a wall outlet available, but you just have to remember to set the charging voltage back to the float charge after that fixed period. What's your guys take on this?

Just wanted to point out as well that the northstar AGM 27f is now the Odyssey extreme AGM 27f incase some people didn't know

 

The alt has a temp sensor and adjusts downward temps rise. Initially mine goes to 14.7 but then trends down to 13.8.

 

^

 

Well I thought I'd look into getting another AGM battery, was doing some searching and ran across this thread.

My current battery is an AGM odyssey group 31.
Had it in my Ramcharger for 8yrs and then stuck it in my Tacoma for the last 6.5yrs. Still going strong with not an issue. total 14.5 years on it
Never did anything to the electrical nor did I use a charger on it.
Still starts my truck fine even in winter up here in Canada. Also starts fine even when truck is left parked for several weeks.

I just figure to be safe, replace battery now before a planned big summer.
Probably try a group 27f this time.

If I can better my alternator charging the battery in anyway I'm all for it.

So which way do I go. Which is best?

1. Leave it as is now?
2. Do the HKB fuse thing from Australia?
3. Is there a computer manipulation tune that works for the 2nd gen like I heard there is for the 3rd gen?

Tuning truck later anyway, so if it can be done that route it might be my first pick.

Cheers

 

The HKB fuse works pretty well and is what I run on my truck for my 27F AGM from Baterries Plus. No tune option for the 2nd gens from what I've found.

No voltage problems or other issues that I've seen w/ the HKB. It did make my lights a bit brighter, but that's to be expected with the increased voltage in the system.

I'm curious to see if there's any issues with running a stereo amp. I'm assuming not, but we shall see.

Edit - no issues with my Morel MPS 4.400. Battery seems to handle the extra draw without issue.

 

@Charger92 That’s some damn good battery life. And a heavy battery, how is that Taco lean? That beast weighs around 70 lbs. The battery may still be good, use a load tester to see if it’s still good. I invested $40 in a fancy pansy Topdon AB101 and it has been accurate in testing batteries. Its quick and painless to evaluate a battery. I once told my sister my tester showed REPLACE on her car battery. Three months later, her battery died while she was running errands. Guess who had to go save her ass? My tester currently reads REPLACE on wife’s 2018 RX350 OEM battery. Gonna go get her an AGM Interstate at Costco. $150.

 

Personally I would leave it alone if you have had that type of performance. There are several levels of Group 31's that weigh from 60 lbs to 80+ lbs. and I would guess you have the heavier version with bigger plates. Ford makes a factory replacement that also boosts the charging but at a significant discount. Adding a second battery in a Tacoma opens a whole new rabbit hole that doesn't need to be gone down. Just my .02 not gospel by any means. If you still have the urge to spend money just get a NOCO GB 70.

 

Voltage boosting isn’t necessary and it’s near impossible to say if it will improve battery life long term. It will however not hurt your trucks electronics (unless excessively done), alternator voltage fluctuates with RPM anyway. Where the boosters come in handy is if you use a winch. Even with engine idling winching still draws down the battery. That’s also a nice little load test, btw. If your batter won’t run your winch anymore, definitely replace it because it will strand you right quick.
AGM is nice for that reserve capacity and it doesn’t spill out off-road

 

I have an odyssey 34R AGM battery. being retired I can sometimes not drive the tacoma for weeks..
In lieu of the diode mod I keep it plugged in to a NOCO 5 amp charger/maintainer when I am not using it which has switchable mode for AGM.
Within a very short time (5 -10 minutes) it indicates 100% charge and then goes into maintenance mode for as much as 24 hrs. See screen shot below

Considering how little I drive it would this solution be appropriate in this case vs the diode?

https://no.co/gen5x1

 

I just got an installed and x2Force group 24 (they were out of 34's). Also, installed the diode mod. my 14 went from 13.4-8 to 14.3-4. Just in my initial install and letting it run for a min in my driveway.

 

Old post I realize but you would only need 1 add-a-fuse and the sense curcuit fuse slot. Add-a-fuses have two female slots connected on one end and not connected on the wire end. Cut the pin off recessed into the end opposite the wire and replace that pin with a fuse tap

$12 WirthCo 30001 Battery Doctor Fuse Tap Kit for ATO Fuses

https://www.amazon.com/WirthCo-3000...r=53BGJJQT67VR6TMESA35&qid=1684385375&sr=8-20 connected to the wire. Then the current has to travel through both the fuse and the diode so you get voltage boost and fuse protection.

 

Since I am retired and drive very little now (maybe 3000 miles a year and sometimes not for weeks) I have installed a NOCO 5 amp charger underhood set for AGM mode and leave it plugged in almost all the time my truck is parked.

And its overkill but its the marine version so is water proof. I used stainless rivet nuts and stainless button head caps screws to mount.