Customizing alternator charging profile for Odyssey AGM batteries?

Hey guys. I have dual Odyssey 25-PC1400 AGM batteries in my 2018 Tundra Limited. This is a considerable investment so I'd like to keep the batteries in good condition.

From what I've read, the Odyssey are quite finicky about how they are charged. In this thread, @pickeledpigsfeet quoted an email from Odyssey, wherein they said, "... the battery can take up to 300A and prefers a charging voltage of 14.4-14.8V ... if not, the battery will fail prematurely due to consistent undercharging or being maintained in an undercharged condition." In another thread, @Stig mentioned the Tundra alternator tends to charge at 14.5 volts, and mentioned that adding a resistor to the alternator fuse can boost this up 0.4 volts.

I'm curious if anyone has a spec that shows the charging profile of the stock alternator in the 2018 Tundra, such as voltage range and amperage over the various RPM range. That way I can confirm whether the Odyssey batts are being undercharged. And if so, I'm thinking this day in age, there's probably a fancy computer controller that tweaks the behavior of the charging system, maybe something I can hack... or perhaps look into the resistor trick above.

PS: The two batts are linked together with and Genesis Offroad's dual battery kit. Genesis' solenoid basically links the batteries' + together when either battery is above 13.2v (+/- 0.1v) for 2 minutes, and disconnects them when they drop below 12.7v (+/- 0.1v) for 1 minute. So as long as the alternator is putting out 13.2v or more, the batts will be charging in parallel.

 

I run one of these in my FJ, 4runner, and Taco with no issues for over 100k miles on each. I see 14.5 at idle and 14.7 at anything above 1500rpm. They have one for a Tundra, but I havent read about anyone using it.

https://www.hkbelect.com/

 

I’ve had the exact same thing in my 2018 for almost a year and no issues. One thing I’ve noticed though is the battery dash gauge is a little low. It matches my bullydog connected to the OBD port, which is about .3 too low. I have the g screen also and it show accurate voltages. I’ll look at what it says next time I drive somewhere.

I’ve also checked with a volt meter and it matches the g screen and is .3 above what the bullydog says.

 

While shopping for my Northstar, research indicated the chief threat to AGM batteries was the internal heat generated from charging too quickly. This results in the charging mantra applied to AGM batteries..."low (current) and slow". The Odessy comments quoted above sound totally inconsistent with anything I've seen on AGM or even conventional lead-acid batteries, but they should know their batteries. I would probably verify those before charging my battery at 300 amps.

Anyway, for fwiw, Toyota designs Tundra alternators to charge at "Standard Voltage" of 13.2V to 14.8V, and "Standard Current" of 10 amps or less @ 2000rpm (unloaded) to 30 amps @2000rpm (loaded). Where the alternator is on the curve is likely set by the ECU.

Here is some general info on battery charging (see paragraph on deep cycle AGM), and on the CTEK smart charger to show how they think an AGM battery should be charged:

https://www.centurybatteries.com.au...alk/issue-2-battery-talk-battery-charging.pdf

https://youtu.be/V_oI3jdlD84?list=PLDs87p4b0x8ypyao0wWhWtN4y341yJatL

 

This is what I use for my dual Optima batteries setup. Charges them to 14.6v every night. My alternator could only get them to 13.6.

CTEK (56-353) MULTI US 7002 12-Volt Battery Charger

$158 CTEK Multi US 7002, 12V Battery Charger for Cars, SUVs and Trucks, All Weather Smart Charger, Battery Desulfator, Power Supply Mode and Reconditioning Mode

https://www.amazon.com/dp/B000FRLO9Y/ref=cm_sw_r_cp_api_i_gC.7Db41XVAZ9

 

Additional info on CTEK charging program to give you idea of the charging voltages and currents at various steps of charge program. Auto battery program is at the bottom, AGM is second line down:

 

That's exactly what I use. Had it since the day I put in a batteries plus Northstar. It's a little pricey for what it is and isn't hard to build your own for only a few dollars but I decided to just buy from hkb.

If anyone running an agm battery doesn't want to go that route, I'd think as long as you hook it up to a good battery charger every so often that runs the proper charging profile you should be just as well off.

 

Just checked and my g screen says it’s at 14.2/14.3 when the truck is running.

 

Alt-s diode will help, there's a GM part number 12135037 that will work or get one of the add a fuse ones from ebay. Highway running helps charge them back up, also solar with a charge controller that has AGM as a selection on the other end is nice to keep them topped off too.

Reference for the part number:
https://www.chitown4x4.com/tech-center.html

 

Thanks, just spent another 50 bucks.

 

Can you please tell me what is meant by "loaded" and "unloaded"

Boy I'd sure love to see a graph of the voltage and amperage output. I wonder if it's in the online FSM, maybe it's worth paying for a day of access to geek out.

 

I ordered the 5A my 2010 called for, they responded it's out of stock but the 7.5A is fine. I said ok, does that mean it will make more power?

 

No, that diode is only gonna give you the half(ish) volt bump. I think the 7.5A rating is for the fuse it’s (also) replacing (5A), pretty minimal risks in my opinion running a 7.5A vs. 5A in there.

 

Thanks.

Which fuse does it replace?

 

There is a very extensive thread on Tacomaworld regarding this topic: https://www.tacomaworld.com/threads/the-northstar-agm-battery-voltage-booster-upgrade.604478/
If the tundra electrical system operates similar to 2nd gen tacomas, there should be a fuse that can be changed to increase the charging cutoff voltage.
The Alt-s fuse is an option/ HKB is another option.

 

Unloaded means with no electrical load beyond the normal driving condition; no AC/heater blower, no headlights, etc. In earlier manuals, it calls for turning on the headlights for the test.

It's unlikely there will be a curve of voltage or amps vs speed in the online SRM. There may not even be a "curve", but charging steps according to battery status. The technical detail is not required by shop technicians. The manual is intended for instructing techs in a "Go/No Go" type evaluation. They're only interested in the alternator meeting the maximum output specifications. If the alternator meets the max specs, then it is satisfactory; if it doesn't, they replace it.

 

What about adding a mini diode LittleFuse 1 amp??

https://www.oreillyauto.com/detail/...ittelfuse-1-amp-mini-diode/02400113xp/4414229

 

While the Diode is able to increase the voltage in the system. You lose the fuse function.
The HKB product is specifically designed to be a voltage booster that maintains the fuse function.

 

The ALT, from what I understand...

 

Yep, in the engine compartment fuse box

 

Here’s more for further reading on this topic regarding a diode replacement

 

Thank you for this link!

And @stuckinohio
Thank you for the tacoma world link.

I’ve been trying to come up with a solution for our trucks not being able to properly charge my group 31 and all the stuff I run. I ended up ordering the adjustable voltage version. Leigh at HKB was super responsive and easy to talk to. Now I wait to see how long something from Australia takes to get here, haha.

 

10 days

 

I ordered the $3 version.

 

Sounds like voltage loss thru wire run...normal

 

Crashandburn on tacomaworld is a very reputable information source. I am OEM part development engineer and trust his recommendation.
We have had disagreements but i understand his viewpoints and respect his quest to be fully DOT complaint from a lighting standpoint.
I recently investigated this mod for my tacoma. I ordered the fuse through HKB's ebay website for $34 US dollars.
Delivery is at least 3 weeks. still waiting (Nov 29th order date)
Long story short, my 2012 tacoma got hit and has sat in the shop for 3 months. I just got it back 12/6/19 but have been planning on upgrading from the OEM stock battery. It somehow started at 12.2v.
I will find out if my noco charger helped or if i need a new battery tomorrow, truck has been sitting at the factory for 3 days while i travel.
Tundra was a required upgrade for towing reasons.

 

So the 7.5a version came, it did bump up the charging as advertised and my Pioneer NEX 8200 hu started having AMP ERROR that caused me to have to shut down the truck. The Pioneer has been in the truck issue free for over a year. I put the fuse back, no more AMP ERROR.

 

Weird. I’m running the $3 GM diode and have the 8200nex unit too. Everything has been running great on my truck since diode install. Is that error in relation to your amplifier or amps (as in drawing too much current)?

 

I searched the owner's manual and it seems to be referring to the internal amp which I have never used.

I can't remember if this unit has detachable harnesses (I have had Pioneers, Kenwoods & Alpines over the years) it has been over a year since I installed this unit. It either does not have the internal amp wires connected or they were never stripped and are taped up fully insulated.

The manual says the error refers to issue with the internal amp.

I never had any issues with the unit until putting this in and it went away when I restored the 5A fuse.

 

Did you make sure to put the fuse in the right way around? Polarity matters