On my 88 Toyota RV I have a modest solar system. 200 watts of panels, 20 amp charger controller, 2 X 6 volt lead acids in series with a AiLi Battery Monitor. DC demand is just lights and a diesel parking heater. I am researching an upgrade to a Lithium battery and a DC to DC charger. Does a single Lithium 100 amp hour lithium battery and a 20 DC to DC charger sound about right.
Modest Solar System Update
- Thread starter GlennDale
- Start date
400bird
Solar Wizard
Without knowing the capacity of your current 6 volt batteries, I'd say the 100Ah lithium is good place to be.
Rednecktek
Solar Wizard
That means a 100Ah LFP would be a pretty direct swap. Lead acid is good for about 50% or so.
fratermus
Solar Enthusiast
- Joined
- Mar 19, 2021
- Messages
- 511
200Ah of lead and ~125Ah of LiFePO4 have the same amount of usable capacity. In practice 100Ah of LFP will probably behave about the same as the lead bank.
Anecdote: I replaced 220Ah of lead (2x 6v FLA) with 100Ah of LiFePO4 to good effect. Capacity is theortetically lower but overall performance better, with no stress about partial states of charge.
If you are adding alternator charging for the first time then DC-DC is probably best to baby the 1988 alternator. You might want to pick one that lets you derate to 10-15A in case the old girl complains.
If you are already charging the bank with a relay or isolator you might see what it does with 100Ah of LiFePO4 before spending on the DC-DC. I saw ~42A with the FLA bank above and that dropped to ~32A with the smaller Li bank. Fairly common with setups that have NEG return through the chassis.
I already have a Cole-Hersee Seloioid connecting the alternator with the current pair of lead/acids. Your point well made concerning pushing my somewhat antique rigs alternator towards a premature death. Before installing first a new LiFePO4 I will disconnect the solenoid and charge the house battery from the solar array only.
Last edited:
