Lithium battery

Charging systems in tow vehicles are not the same as when it was a simple voltage regulator. To get better mileage, the charging systems in new vehicles also use a charge control system that is barely adequate to charge the vehicle's battery fully, let alone trying to charge a LiFePO4 battery. I found when we first got our LiFePO4 battery and tried to use it with the Frontier's charging system that I would end up with less charge than when I started. One overnight stay and then driving several hours the next day and the battery ended up even lower in charge. I think the LIFePO4 battery's charge was fooling the Frontier's charge system into thinking the truck's battery was charged when in reality, the LiFePO4 battery was feeding back into the truck. That is the reason I say that you need a DC to DC charger if you intend to run the LiFePO4 battery. Of course, if your tow vehicle is an older one that uses a simple voltage regulator, you might be okay. However, any recent vehicle is likely to have issues.

Hello OTTR,

ummm.

Battle Born recommends using a high quality ac charger specifically configured for Li batteries. The key concern is not undercharging, which won't hurt a Li battery, (just limits useful capacity) but overcharging during bulk or equalization mode. That is dangerous.

My WFCO failed and took my flooded golf cart batteries up to 16V plus volts. No harm done to those batts, just excessive water consumption, because I caught it before the plates were exposed. But that would be very harmful and dangerous for a Li battery. Battle Born's BMS is designed to prevent that level of overcharging but after my experience I wouldn't want to count on it as the sole line of defense against overcharge.

Battle Born also recommends using a DC/DC converter for alternator charging. They are master distributors for both Progressive Dynamics (ac chargers) and Victron (solar charge controllers and DC/DC converters) so you can get all your hardware from them if you want. PD and Victron both make good products for this application.

I'm not recommending Battle Born as a source though, they are overpriced for my budget. I'd personally go with StephenH's lower cost approach. Either way will work fine, but you do need to take some care in a Li conversion. I wouldn't recommend just dropping a Li battery into an rpod without other modifications.

+1. The AGMs (absorbed glass matt) batteries are quite a bit more expensive but perform no better than flooded deep cycle batteries. They are also more sensitive to overcharging (because you can't just take off the caps and add distilled water) so you have a bit lower peak charging voltage. They do have one advantage which is lower maintenance so if you can't bring yourself to check the water level every month or so by all means spend the extra $$$ for the AGM's.

Thanks for all the info and advice.  Think I am going to pass for now.  What about the “AGM” type batteries?  Anything special to add one of those or is just a straight swap?