The heart of our WattCycle conversion is the 51v battery pack, likely the most expensive part of the conversion. There were so many directions we could have gone when selecting a power solution, flooded lead acid, AGM, lithium, battery configuration, charging system, and the list goes on. I wanted to use a system that met my demands for power throughout the day, giving me a range of 15-20 miles if needed. I also needed a system that I could charge with a solar panel anywhere I went, WITHOUT plugging into the grid (I will cover the charging system in the next blog post). I also had to seriously consider weight, durability and price. I could have gone with the battery pack sold by the motor manufacture, easy but very pricey at $800-1500, depending on the amp hour rating. All of these variables created hours of research, with the hope that it pays off.
The hub motor requires 36 - 51 volts for correct operation, the higher of the voltages will reduce my amperage consumption. We went with a 51 volt battery pack because of readily available charging systems in that voltage and the flexibility for configuring a battery circuit. Our next choice was either eating the expense of lithium batteries or purchasing sealed AGM (Absorbed Glass Mat). Lithium packs are extremely expensive however have great advantages when installing them in a system such as what we were assembling, we bit the bullet and ordered lithium.These lithium phosphate modules are rated at 12.8 volts and will give us 6.4 amp hours of current. When wired up in series we should have 51.2 volts being supplied to our controller and eventually the motor. The amount of Amp hours has been a big concern when developing this power system. When you increase amp hours you also increase the duration of operation as well as the price you are going to pay for the power pack. For our system, 6.4 amp hours falls on the low side of the scale, however the solar charging system that we are installing should (in theory) overcome this shortcoming.
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