I am planning a 24V system with 1000 watts of solar
, a Midnite Classic 150 MPPT solar
controller, and a 24V input Magnum 4000 watt hybrid inverter
Those are the main components. I also need 12V to power various items such as water
heater controls, some electronics
, led lights
, and the furnace fan.
I initially was going to go with just lead acid, but am entertaining the idea of LiFePO4
. I want to have at least 3.5kwh of useable battery
capacity and so was considering four Lifeline 6V 300ah AGM
(so they can mount on their side in the space available).
I am not comfortable right now with the state of LiFePO4
to sink $3000 into it as the main battery
bank, but I am considering using the LiFePO4 as the 12V house battery so I can experiment
with it. If I have great results, I would eventually switch out the AGMs for 8 big LiFePO4 cells.
plan is complicated, but I think it has some potential. I would utilize the high current
from the solar during the peak sun hours to bulk charge the lead acid, then when they needed to be in absorption charge state, I would switch to charging
the LiFePO4 house battery. In this way I would be able to utilize the remaining peak sun amps instead of letting them go to waste.
I am thinking of programming a microcontroller (just an Atmel 8 bit) to monitor
the four 3.2V 100 ah LiFePO4 cells of the house battery and also control the charger
for them, which would be powered off of the main house batteries/Midnite MPPT
. I may need a sensor to determine the level of insolation available at the solar panels
and I need to research
what the Midnite controller would do if it was charging
the 24V lead acid in absorption and suddenly a 15 amp load on those batteries kicked on (the 24V to 14V LiFePO4 charger).
Even though this all sounds complicated, it does sound doable, and doesn't really use that many more parts
than other methods since I need 12V and you can't directly tap from two of the cells in the 24V lead acid pack without causing imbalance (unless you use special devices). It may be a fun way to dip one's toe into LiFePO4 without breaking the bank, as a 12V 100AH pack should cost me under $600 from CALB.