Anyone have experience or need to adjust alternator voltage to accommodate an AGM battery? I recently upgraded the ‘12 Tundra with an Odyssey 27F AGM battery. So far I’m happy with the new set up but stock, the Tundra only puts out about 13.2 volts. AGM requires 14+ volts to stay fully charged. I recently purchased this product to help fix this issue.
Anyone have experience with having to adjust voltage for an AGM or this product in particular?
Hey Carlos! Yes I do have experience with having AGM battery. There are options out there that you could contemplate on. One method is that you could pay for an OTT tune. A tune will be beneficial in two aspects. One it will improve your driveability with the gears on your truck and the second is you can request with the tune to change the output that your alternator puts out to the 14.2V necessary for adequate charging of your AGM. This method is the more expensive route, but once you are customer of OTT you can get future tune updates for free.
The other much cheaper option would be buying a battery maintainer. It is a hassle and requires routine plug and charge. It’s still a good idea to have a battery maintainer so you can fully top off your AGM battery on a routine basis to maintain the longevity of the battery.
Another option is to buy a hood solar panel that will charge your AGM battery. It’s a much lesser hassle option. But you would need to keep in mind that it require solar to function.
Something to also think about is, you could also combine some of these options as well so you’re not dependent on one system.
Thanks for the thoughtful answer @BOMBS510 ! I just learned a couple weeks ago a tune could help with this.
@carlospalooza I’ve went back-and-forth with Bryan from Voltage Booster a few years back. Great service, great company. This is a great solution for now if you’re not wanting a tune. I’ve used a Bluetooth OBD adapter to see the voltage the truck is putting out while on, can do this with a multimeter too I’d imagine. I run mine at +1V to stay within charging range.
This was the root of a wiring issue I had for months with an older battery dying because it was never properly charged because I didn’t have this.
Hoa. Thanks for the OTT explanation again. I do remember discussing this with you on our DV trip however I missed the part about the tune including an alternator voltage change as an option. I’ve also had my eye on Lensun but price per watt killed the deal for me. The need didn’t justify the cost (yet). The OTT tune seems like a better option for all the other enhancements you’re getting, +future tunes.
For now I’ll run the VoltageBoosterPro and see if it works as advertised. My guess is I won’t really see any immediate benefit or change unless the new battery goes through some extremes or documented testing over the life of the battery. Running this product seems like a safe option for now.
Thanks for chiming in Matthew! Glad to hear you have had a positive experience with this company.
I want to throw this in also.
If you use a tune to raise your voltage, you never can put a regular lead acid battery in even an an emergency. The new voltage will be too high. This will over voltage the battery and will not only damage it but can cause it to explode.
I’ve run multiple AGMs for decades. In what we do the positive outweighs any negatives. Running an AGM at the lower voltage won’t hurt it but it will never hit 100%. Most likely it will charge to somewhere in the low 90%. Unless you actually use that extra power most don’t notice a difference.
I personally raise my voltage to just shy of 15 volts. The electronics not only don’t care but some parts are happier at the higher voltage.
As for not raising the voltage, I’ve run pairs of AGMs for years at the lower voltage (13.5-14.0) without lessening the life span.
you never can put a regular lead acid battery in even an an emergency
Great call out @Smritte !
The safe bet would be to have a battery jump pack.
That is good information to know.
Just want to provide an update. The VoltageBoosterPro has been installed and works as advertised. Super easy install and extremely easy to either toggle between high (~14v) or higher (~14.5v) voltage, or remove it all together and revert back to stock any time.
The device is very well made and seems like it will last. The only minor odd ball thing is it uses a larger sized blade fuse as opposed to the “mini” fuses that come stock with the 2nd gen Tundra.
Although about $100, I feel it’s worth it and you’re supporting US (TX) product and small business.
Cool, think I will get one.
@carlospalooza great to hear.
+1V keeps my battery within the charging range (14.4-14.7V).
For context on the VoltageBoosterPro (I researched this extensively when I purchased):
Batteries have optimal and max charging voltages. The goal is to run as high as possible without going over the number. Higher voltage charging can dangerously raise battery temps.
What I believe is happening here is a lack of complete information and wrong information.
Out of this information, what do people remember? Hot and under hood temps. If your somewhat well versed, you know the vehicle “magically” keeps the battery at the proper voltage especially if its not mounted under the hood. Add in idiot U-Tube people and now a bunch of people think a certain way.
Here’s how the manufacture does a variable charging voltage. Your regulator is somewhat set to 13.8 volts (ish). One of the wires is a sensing wire. This wire monitors voltage. If its too high, the regulator lowers output voltage, too low and it raises it. There can also be a battery temp sensor to make sure the battery doesn’t get too hot..
The issue we have running lithium’s and AGM’s is our alternator voltage is set for Lead Acid batteries. All we have to do is change the regulator spec up one volt.
OR we drop the voltage on the sensing circuit. Today cars monitor voltage the same as old school and they monitor the fuse block voltage. If we lower the voltage slightly at the fuse block, it tricks the alternator into raising the voltage to compensate.
Diodes will cause a .5-.7 volt loss. Putting a diode across the alternator ignition sensing circuit (alternator fuse) is one of the easiest ways to do this. The alternator draws ~7amps through there so, all you need to do is make sure the diode you install there is properly sized.
This company web site cautions about using the GM “diode fuse”. This will work except you removed the fuse part and its not high enough rated for what your doing but, it achieves the same thing.
Scott. Thanks for the clarification and details.
I thought about the diode but seemed like cheap insurance to go with the VoltageBooster. I also like the option of running “low” and “high” voltage with the slide of the switch. This seems like it would address the heat aspect if concerned with that. I also saw a hack that used the diode, but added a fuse inline which is cheaper and overall, seemed similar to this product, without the build quality
Nice to better understand the whole battery and charging process while having a couple of solutions (diode, VoltagePro or just stock) that have been in use for some time.
In my opinion, the diode method is the best way to go. You could have a custom alternator built with higher voltage output or have the PCM (in some) programmed for higher output but, you cant easily go back.
Even though I can make my own, its just easier for me to buy one of those. What I really like is the voltage switch. Different vehicles will have diffrent output voltages. With the switch I can choose the optimum on my build. The optimal safe area for AGM is 14.4-14.8 with 15 at max.
In reality, once a battery is fully charged, the voltage should be dropped by 1 volt (13.4-13.8). This is called “Float”. Unfortunately, cars don’t do this.
The other reality is, cold is very hard on batteries. Rapidly decreasing lifespan
In my opinion, this is why we only get five years out of batteries and with the higher end ones giving us a bit more.
When I start my truck my voltage is around 14.1 - 14.2. After a minute or so, it drops down to about 13.7. I run an Optima Yellow Top battery.
Ron W.
Cool.
Just when you think you’ve seen everything. Start up is going to be higher and it normally drops once the power used to start the vehicle is replaced but, normally its just a couple tenths.
Next time you check your voltage, see if it goes beck up if you bring the rpms up over 1k. There’s four ways an alternator can be wound internally. One of the higher outputs needs to have the rpm brought up slightly. These are one of the higher output windings. No ill effect from it, just design.
It stays consistent at about 13.2 -13.7 while driving. My 2013 Tacoma does have the factory high output alternator.
Ron W.