Combining Solar and Alternator charging for 150 Ah 12V LiFePO4-battery

rilonau

New Member
Hi all,

i am new here but have some experience in electronics and Solar power.
We drive a big solar generator on a big barn roof (about 1000 m2 and 92 kWp) and a small testing PV (300 Wp) on our roof.
My brother wants to build a small solar driven RV, about 300 - 400 Wp with a 150 Ah LiFePO4 (Xenes battery) and also wants to charge it via the alternator.

As 12 V LiFePO is very close to lead acid specs (at least at end-of-charge voltage 14,4 V) i would just connect the LiFePo directly to the alternator (same as the starter lead acid) but disconnect the lead acid when discharging (to prevent deep discharge of the lead acid which tends to build lead sulphats at low SOC for a longer time). Is it o.k. for the alternator (current) to charge 2 batteries (say 75 Ah lead acid and 150 Ah LiFePO) at the same time or would it possibly overload?
I am sure there is a regulator connected directly to the alternator that controls voltage and amperage and will reduce current if nessecary - but not 100% sure here?
Does anybody know how to take care and if this solution will work (on a modern RV - more on the smaller side - no monster RV).

thanks in advance!

Cheers, Rilo
 

mikefitz

Solar Addict
Is it o.k. for the alternator (current) to charge 2 batteries (say 75 Ah lead acid and 150 Ah LiFePO) at the same time or would it possibly overload?
If you search the forum this as been discussed many times.

The recommended and safest method to protect the alternator and to ensure both batteries are not compromised is to install a battery to battery charger between the starter battery and house battery. Some B to B chargers have a solar charger built in, for example the Renogy DCC50S.
A stand alone B to B that performs well is the Victron Orion 12 12 30.

Mike
 
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