Lithium batteries and new solar charger
I am replacing my 4 6V batteries I think 2 lithium, have never been impressed by the 30A PWM charger for my 600W solar, probably my fault for using 8 avg wire on a 9m run. Thinking if I get a Victron ...
Forum Discussion
600w aimed at a high sun on a nice day will supply 6 x 6.2 amps (you get Isc value worth of amps to battery with PWM) so 37.2 amps. With the panels lying flat you get fewer amps than that. How many amps will depend on your location and time of year.
(I have three 100w and have often seen 18.6 amps to the battery with them aimed. )
So the 30 amp controller is already not enough except the panels are flat so you are under 30 and the controller has not over-heated.
Your length of #8 is not an issue because voltage drop doesn't matter so much with PWM. Panel voltage will be close to battery voltage so you have room for the voltages drop without it bothering anything.
Voltage drop matters greatly with MPPT though. You benefit from the 24v needing thinner wire than 12v, but adding panels will increase the amps and it could be a wash so you could need fatter wire anyway.
Two LFPs will have fewer usable AH than four 6s, but with the solar you will only notice when there is an overcast for a couple of days so you need your battery bank as a "reserve" until the sun comes back out. It "depends" whether your two LFPs will be enough reserve, but it also "depends" whether the four 6s would be enough, so there is no way to be sure. You have to figure the odds on that. Obviously the odds are better in CA than in WA, eg.
(I have three 100w and have often seen 18.6 amps to the battery with them aimed. )
So the 30 amp controller is already not enough except the panels are flat so you are under 30 and the controller has not over-heated.
Your length of #8 is not an issue because voltage drop doesn't matter so much with PWM. Panel voltage will be close to battery voltage so you have room for the voltages drop without it bothering anything.
Voltage drop matters greatly with MPPT though. You benefit from the 24v needing thinner wire than 12v, but adding panels will increase the amps and it could be a wash so you could need fatter wire anyway.
Two LFPs will have fewer usable AH than four 6s, but with the solar you will only notice when there is an overcast for a couple of days so you need your battery bank as a "reserve" until the sun comes back out. It "depends" whether your two LFPs will be enough reserve, but it also "depends" whether the four 6s would be enough, so there is no way to be sure. You have to figure the odds on that. Obviously the odds are better in CA than in WA, eg.
