AGM BATTERY CHARGING - ALTERNATOR VOLTAGE BOOSTER

OK great, happy that you have chosen to run yours that way. Happy that people get them to last 5 years without doing the increase. I will still be increasing my voltage to match the battery's suggested charging profile. It is well established there is danger in overcharging, we already know.

 

Well that’s the good thing we each get to do what we want here lol.
I’m always open for learning new things though, got a link to your battery suggested charging? Is that for using a charger?
Your alternator is essentially a float charger, your battery never fully discharges under normal operation. Perhaps you use yours in a deep cycle operation separate from your cranking battery? The cycle service rating on the pic below is for applications where you discharge and recharge the battery, deep cycle use and you would typically use a separate charger to charge in that application (such as for a boat trolling motor, solar power setup, etc). That’s not what your normal battery is doing it stays topped off as you drive via the alternator, a float charge.

 

Post #5 in this thread links to the other AGM charging thread created by TacomaWorld users who are much, much smarter than I am and explains what you are asking:

https://www.tacomaworld.com/threads...ernator-voltage-booster.611314/#post-20702483
https://www.tacomaworld.com/threads/the-northstar-agm-battery-voltage-booster-upgrade.604478/

 

Oh I’ve read that thread before. Don’t agree with it. I’m an electrical engineer and do my own research, have worked with battery banks in power plants etc. As you said we each get to determine things ourselves.

 

What don't you agree with? Will you share your knowledge with TacomaWorld?

 

lol I just did in my post 222. I don’t agree you need to boost the alternator voltage for an AGM for standard use in your truck. And as I stated in an earlier post I have yet to see an AGM battery manufacturer recommend boosting the alternator voltage for a standard automotive battery application. Not saying there’s not one out there but I have looked and not found it. I tend to rely on manufacturers rather than forum posts.

 

Got it. Thanks for sharing. I'm going to continue on my journey to boost voltage into the desired range. Cheers.

 

May not hurt and could gain you an amp hour. Go for it.

 

I just found this on Odyssey's site regarding charging voltage:

A. If the battery is used in a starting application, the alternator should provide between 14.2 and 14.5 volts at the battery terminals. In cycling applications, the absorb voltage should be between 14.4 and 14.8 volts, while the float setting (if applicable) should be between 13.5 and 13.8 volts.

 

Now that’s interesting have a link? Worth reading to me. Doesn’t agree with what they say in my post #220 so I want to see what battery that applies to. The one I posted are for their yellow and red tops which are sold at automotive stores.

 

You posted info for Optima batteries - the used-to-be gold standard. I don't know of anyone that will run an Optima any more - but that is another discussion.

Here is the FAQ page on Odyssey's site: https://www.odysseybattery.com/faqs/

The last question is the one regarding charging voltage. Unfortunately, I could not find much tech info on their site. I'll check my batteries after work - I think there is a charge voltage listed there.

 

Odyssey or Northstar/ X2Power are the only three I will touch. They are expensive, but so worth it given the way they perform.

 

I misread your post thinking Optima. I agree with using the specs recommended by the specific battery manufacturer. I note that the float voltage (such as maintained on a separate charger) a voltage of 13.5 to 13.8 is adequate. I wouldn’t be concerned therefore if my alternator produced 13.8 or higher, the capacity loss will not be that much of any. But if you want to increase your alternator voltage that’s ok too, just don’t think it’s going to give you much of an increase in capacity.
Here’s a link to the Optima battery data sheet for those interested:
https://sqlvawbi4pg46k2imi.blob.cor...rary/battery_user_guide.pdf?sfvrsn=2c363857_4

And here’s a link to the Odessey battery spec sheet:
https://www.odysseybattery.com/wp-content/uploads/sites/2/AM-ODY-OM.pdf

Note that per the Odessey spec sheet at 12.84V your battery is fully charged:


Therefore if you have this battery using your standard alternator (no boost) and when you turn the engine off the battery is at 12.84 V or higher then it’s fully charged and you really don’t need an alternator voltage boost to keep it fully charged. If it’s slightly less than you have slightly less than a full charge and the note regarding battery life applies if less than 12.8V. Up to you to boost or not but don’t expect a big capacity increase.
Update: Seeing this post in the Northstar AGM thread, the issue with Tacomas typical alternator voltage allows for sulfation and the manufacturer recommends a higher alternator voltage. So I concur with sticking with whatever the battery manufacturer recommends. I did not see the same requirement for the Optima battery though it appears to have reliability/quality issues these days compared to earlier models per posts.
https://www.tacomaworld.com/threads...e-booster-upgrade.604478/page-4#post-20407925

Though I’ve read posts of Odessey failures, Northstar failures (one boosted) as well.

 

Don’t most people install AGM’s so they can use them to power accessory devices? I know I discharge mine completely sometimes since I use it to power my fridge and lights at camp.

 

May be true.

 

Why else would you buy a $400 battery designed for deep discharges if you aren’t deep cycling it? Otherwise, wouldn’t any $100 battery would do?

 

AGMs are supposed to have a much longer life. Prices are more like $300 -$340 except for larger sizes.
Those sold for automotive are typically not just thick plate deep cycle which aren’t made for high starting currents, but instead dual use thin plates pure lead for high starting current loads and deep cycle capability.
https://www.odysseybattery.com/news...benefits-the-odyssey-battery-tppl-agm-design/
https://www.northstarbattery.com/agm

 

I get it. I have an Odyssey Extreme 27F. I remember it being more than $400 and it only lasted 3-1/2 years before I had to warranty it. Couldn’t tell you why since I definitely didn’t 80% discharge anywhere near the rate # of cycles.

Now I’m trying to decide the best way to make this one last a bit longer. My factory battery pretty much saw the same usage and easily lasted 5 years.

 

This is very interesting information, thanks for sharing. Odyssey, Northstar, and X2Power batteries are all the same thing now, all manufactured by EnerSys so it should hold true across the lines. I'm going to call/email EnerSys when I have a bit more time just to confirm some things.

That being said I'm copy/pasting my response in the other AGM megathread because I'm too lazy to re-type it all here:

So for now ignore my previous statements about the 14.9 volts. I need to repair/replace some things and then confirm data before I can trust the numbers. Will share back what I find later.

 

I am back to this opinion myself. I ran my current AGM battery for 6 years without a diode then decided to try it. Then my alternator's voltage regulator failed after about 6 months of that, charging at about 14.5V. Could have been a coincidence but not worth taking the chance again, IMO. So now with the new alternator in for about 6 months my AGM is still chugging along just fine. Charges at about 13.8 to 14.2V and all is well.