Lithium for RV

[Guy]

Got my LiTime 100amp battery and have been told that I must have a DC to DC charger on my pickup truck in order to charge the Lithium battery in my 5th wheel. My alternator is 180 amp. I realize that the RV converter must be set to Lithium instead of standard battery mode. If mine doesn't switch I will have to upgrade that but was never told or saw on youtube where one needed a dc-dc charger. Some say you do but those people have large battery banks on motorhomes. I realize that the standard alternator won't get the Li to full charge. Just don't want to hurt the new battery or the truck alternator. The battery specs say the BMS will shut the charging down when battery gets to 14.2v. My alternator digital readout states it is putting out 14v when charging only the truck batteries, mines a ram diesel. Just don't want to buy extra things if I don't have to. I'm not an off the grid/full time camper. Thanks.

 

[Rocketman]

You want at least one charging source that will charge the lithium batteries how they want to be charged. This is usually either the a grid/generator charger (the converter) or solar.

The alternator will not add much power unless you engineer it to do so. Long wire runs, smaller OEM wire on the truck, higher charge voltages for the lithiums- usually mean not a lot a charge happens- but you do want to verify that’s what happens on your rig. (MotorHomes have to be very careful and use Dc-Dc chargers because of large wires can transfer large amps and overload the alternator). If you want the alternator to charge the lithiums- a Dc-Dc charger is needed to boost the truck voltage up a little so you get good charging (you may need to upgrade the wires so they are big enough).

I would double check those charging specs - most lithium batteries want 14.2 to 14.4 charging so the bms can balance the cells. The bms usually stops at a cell level of 3.65v *4 = 14.6v

 

[Guy]

I will be getting a Li converter so when I plug into shore power I can charge the battery correctly. My MPPT has a setting for charging Li. I always plug in the rig to load up a few days before I go out, so the battery should be 100 charged before I drive away. So since the battery is fully charged, it should not be asking for any power from the alternator on the pickup at all. After camping awhile and I drive out the battery may be down a little but I would think the truck batteries are full, or almost, and would not need alot and neither would the RV Li need alot. So the alternator should be able to handle the needs of all. I would think.........

 

[scrubjaysnest]

Have a battery isolator in my 2008 Ram. It is solid state and wired the alternator to the isolator. B1 is cranking battery and B2 is to the trailer batteries via 8 AWG marine grade wire. With the truck in tow/haul at idle and the refer on dc there is 15.5 volts at the battery bank. The flooded batteries at the time were very happy. Current was 0.2C. That was 2012, today the battery brand wants you to limit it to 14.8 volts. We now have a motor home, with just an isolation switch between cranking and house batteries. Voltage at the house batteries runs 14.4 at up to 60 amps. Been that way for 2 years now, the relay I took out kept burning the contacts. MH batteries are AGM and I would not try either method with lithium or Gels.

 

[Benjamin Yang]

For lithium batteries, especially in trucks, using a DC to DC charger may be a good option, especially if the generator output voltage is insufficient. This ensures that the battery is properly charged and prevents damage to the battery and generator.