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The Battery
We wanted to charge the battery with the solar cells. The battery is a lithium battery and will accept about 10% more Watts (volts times amps) per hour than its Wattage. We needed to collect between 350 W and 400 W. Below are the calculations we made to decide what battery to use.
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36 V Battery
40 V x 2.5 A = 100 W
Not enough because we should produce 300 to 400 W per hour.
48 V Battery
52 V x 5.5 A = 286 W
Not enough because we should produce 300 to 400 W per hour.
52 V Battery
58 V x 5 A = 300 W (up to 10 A but charging at high A is worse for the battery so we programmed the MPPT to charge at 5 A)
We went with this one.
The other possible solution was to put some power into the battery and some directly into the motor, which prevents loss of energy. The mppt has a load outlet to connect the mppt directly to the controller. The load would send the demand to the motor and the excess to the battery. We wanted to get 300 W to the load and any remainder to the battery. Because the Anderson connectors in the controller melted when we tested it, though, we disconnected the load thinking this was the problem. Now that we know this wasn’t actually the problem (the controller was), having power sent directly to the motor as well as to the battery will be a good solution for next time.