Adding solar to a motorhome

[Ampster]

Good post explains it better than the expert did.

[nairbg]

Somebody here that seems to know everything apparently needs to see this:

https://www.power-sonic.com/blog/how...po4-batteries/

[Ampster]

I am not stupid. I know both Float and EQ are the exact same thing (algorithm). Like calling black ebony.

No, I know you are stupid, but if you assume the person asking the question is stupid they could take you literally and keep the same Pb settings for their LFPs and ruin them by keeping them at high SOC for extended periods of time. Or worse, no Float on a Pb battery so it self discharges when the motor home is parked. Maybe that is not a problem for you.

[Sunking]

I do think you would agree that putting a LFP on Float or EQ would not be a good thing?

I am not stupid. I know both Float and EQ are the exact same thing (algorithm). Like calling black ebony.

[Ampster]

Huh? There is no difference between a PB Charger and LFP. They both use the exact same voltage and algorithm.

I think what you mean is constant current and constant voltage are the same algorithms. Just my personal preference, but I prefer different voltage settings for longer life of LFPs. I do think you would agree that putting a LFP on Float or EQ would not be a good thing?

[Sunking]

I know that the Pb-acid type battery charge profile (that the converter will have resident) cannot hurt the LiFePO4 house batteries. I wonder if the Solar Charge Controller's LiFePO4 charge profile will damage the Pb-acid chassis battery? More research to follow.

Huh? There is no difference between a PB Charger and LFP. They both use the exact same voltage and algorithm.

[nairbg]

Having researched my MH's Battery Control Center (BCC) unit (F73-1020) I have discovered that there is a dynamic battery-charging priority logic built into the BCC. This logic provides that the system gives charge priority to the chassis (starter) battery when the engine alternator is feeding the system and once it reaches full charge the BCC switches charge current to the house batteries.
In the alternative, the BCC feeds shore power and the generator charge current through the converter to the house batteries first and to the chassis battery when the house batteries are fully charged.

If I convert the house battery bank to LiFePO4 batteries...
With the solar system's Charge Controller feeding directly to the house batteries I am afraid that there will be a conflict because the house/chassis batteries are mismatched and their respective charge cycle parameters are different.

I know that the Pb-acid type battery charge profile (that the converter will have resident) cannot hurt the LiFePO4 house batteries. I wonder if the Solar Charge Controller's LiFePO4 charge profile will damage the Pb-acid chassis battery? More research to follow.

[NCmountainsOffgrid]

RVs are wired to go directly from the Solar Panels to the Solar Controller to the HOUSE BATTERY bank.... nothing in between. The solar is simply to CHARGE the house battery bank.

Most motorhomes also make use of an INVERTER, which gives the house 120v power from the batteries when no generator is running or no 120v shore power is available.[edit: the Inverter is typically only to power low-draw amperage appliances, or basically OUTLETS, where things plug in, though it's not for anything with a high-draw, such as heaters, air conditioners, etc. - those are left to the generator or shore power only.]

I own one with all of the above.

[Mike90250]

It all depends on how the existing system is designed.

The main principle is to reserve the vehicle starting battery as absolutely top priority, so you can always start and go. With contactors and voltage sensitive relays, there are a dozen ways to cobble it together, and you have to reverse engineer it all, when you want to add another charge source.

[nairbg]

Given the complex charging system in a large old RV which charges the house batteries and the chassis battery from the engine alternator, from an onboard genset, and from a shore-power plug-in, and which includes one or more automatic "interruptors":

Is adding a 300-500W solar system simply a matter connecting the system to the batteries, or is there some controller interface with the existing system to prevent electrical conflict between the existing RV system and the solar addition?