[ms0072]

I have been trying to find the best and biggest battery for my 08.
Ive read quite a few threads and responses and the more I read the more I am unclear about it.

Some threads talk about our alternator not putting out the correct voltage to properly charge AGM batterries, other threads completely ignore this and have many people recommending different agm batteries.
I do some camping with the runner but basically the battery is just for starting. I live in the northeast and do spend some time in northern part of ny state over the winters.

So -- does our stock charging system correctly charge the AGM batteries or not ? If not then why are so many recommending them and what have their results been over the years ?

Also what is the biggest battery I can fit properly without any mods ?
I dont mind spending a few extra bucks to get a bigger or better battery within reason.


Thanks for any help you can provide.

[CA-RJ]

I've had an Odyssey 34R-PC1500T in mine for the last 4 years and love it. I've had no issues with it staying charged. When camping, I run a fridge off of it as well and haven't had any issues there either.

[Bogrun]

I am by no means an expert but in doing my own research for my next battery this seems to be what I've found out:

- The alternator is more than capable of supplying the necessary voltage to an AGM battery. The problem the fuse that regulates the charging of the battery. To get around this, there is a OEM GM fuse that will fit with only minor filing of the plastic housing. The part number is: 12135037. It's about $8 on Amazon. This should give your AGM battery the constant ~14v it needs to stay fully charged. Do you need to replace the fuse? I'm not sure. It seems like it would be best practice but I've also read some conflicting information about it. Some people don't seem to have any problems running AGM's stock and others seem to have issues and swear off AGM's entirely because one went bad on them prematurely.

- As for the largest battery, it seems like a group 34 will fit with only a spacer underneath it. There are also group 31 batteries but those seem to require some modification of the cables and a larger battery tray to fit. There are some pretty detailed threads on here that could probably offer more insight on the subject. Although if you're primarily just using the battery for starting I don't know if you would really notice the difference of a 31 or even a 34. I haven't had any issues running a 710 CCA lead acid in the coldest parts of winter in Detroit and if you upgraded to an AGM you'll get a pretty substantial bump in CCA even if you keep the stock battery size. With that being said, you could always go to a group 34 battery and keep it a lead acid and not worry about any voltage issues and get the benefit of higher CCA's.

There's definitely a lot to consider but hopefully this helps get the ball rolling on your continued research!

[mysticz]

Have a Diehard Platinum Group 35 as primary and Diehard Platinum Marine as a secondary battery in my rig for over 5 years with no issues but I heard DH does not offer the Platinum series any longer, so my research shows now that Northstar makes the identical battery now. I ran stock alternator for most of the 5 years which had no problem maintaining a consistent 13.7-13.9 charge rate but upgraded to a high output alternator since I added a whole bunch of electronics and a fridge in my rig.

Other brands I have used in since 2005 were Odyssey and Optima both good but my current has proved best in my opinion.

[Whytey]

I've got a Northstar Group 31 Battery in the stock spot with stock tie down and stock tray.
Cables needed to be modified a little bit (some trimming on positive mount and new negative to fender wall cable).

To solve the low voltage issue from the stock alternator I purchased and installed a HKB adjustable voltage fuse. This allows me to boost the voltage from 0v to 1v in increments on .2v.

The Northstar battery requires 14.4-14.8v.
I boosted my voltage by .4v and that has me sitting around 14.6v on startup after a few days of sitting.
It will drop to around 14.1-14.4 after a bit.
It never spikes higher then 14.7v (I wanted to ensure it never hit 15v so I did not damage anything.)

[4RunnerAquasport]

AGM batteries are a good fit for off road vehicles. Wet cell will weep acid if you go off road much, or are on a crappy roads with a stiff suspension. They have good CCAs for starting and decent amp hours for running off grid for short periods.

But, like what has been mentioned, they require 14.4v to 14.8v to properly get a top off charge. There are thousands of people running them with insufficient voltage and are having no issues. Some people who use their rigs for extended wilderness trips, have mentioned having some concern for a proper charging voltage on these AGMs. I would guess that these batteries will last 6+ years if taken care of, but might not go 4 years if not charged properly.

You can put a charger on it two or three times a month, especially after a camping trip. You can also install a GM diode that fits in place of the Alt S 7.5 amp fuse. The GM diode does not have a fuse, it is a diode that tricks the alternator in to putting another .6 volts to your battery, there by raising your charging voltage to accommodate an AGMs charging needs. Now this is a concern for some who worry that there is no fused protection in the Alt S circuit by running the GM diode. So enter the HKB voltage boosters with fused protection. There is also ArcLights offering and looks well made with a switchable voltage boost, but he is a small business and Covid has him shut down for awhile.

I recently went with "Dirty Parts" Voltage booster. It arrived across country in less than a week. Ironically I installed it yesterday. Here is a link to Dirty Parts page and a video I did installing it.

Dirty Parts

https://www.toyota-4runner.org/3474576-post87.html

[chaz]

dirty parts has been working fine for myself also.

[agua.fresca.viaje]

Hi all,

thanks for the experiences shared in this thread!
I got my 2005 4runner SR5 in Chile, and it seems that the engine is set up a bit differently than in the US version... so I am struggling to find where to put the second battery under the hood, even when looking at deep-cycle batteries

Cheers!


---------------------------
2005 4Runner SR5

[Daemoro]

I know this is over a year old, but thanks for the info here. Got the Dirty Parts part and sitting at 14.64 now for my new Optima Redtop.

[originalg00kster]

Originally Posted by Daemoro

I know this is over a year old, but thanks for the info here. Got the Dirty Parts part and sitting at 14.64 now for my new Optima Redtop.

PLEASE NOTE - VERY IMPORTANT:



WHEN ORDERING, PLEASE LET US KNOW IF THE FRONT LEG(towards the front bumper)OR REAR LEG (towards the firewall) OF THE "ALT-S" FUSE IS 12-VOLT HOT ON YOUR VEHICLE WITH THE KEY ON (and the factory fuse out) TO MAKE SURE YOU GET THE CORRECT UNIT

^^ How would we check with no volt meter?

[Daemoro]

Other than a multi meter an automotive test light would work I think. I just broke down and bought a multi meter and started learning how to use it. I had never used one before reading this thread.

A multi meter costs less than the part.

[yourfriendcasey]

Old thread but as I'm doing my tidbit of research on getting a new battery, you should note that a higher group number does not always equal bigger battery. Look up the BCI group sizes and calculate the volume. Obviously there are different quality levels at each size but generally, this is what I found to be the order of largest to smallest capacity that will fit a 4th gen (by volume only): 31F>27F>24F>35F

I'm sure many of you know this but I only figured it out after spinning my wheels for a bit. 27F seems like the best option without creating unnecessary extra work.