OK you guys, school me on adding another battery. My XM-3150 runs good, but since when is that an excuse for making it run better. Besides, playing with this thing has become my favorite hobby.
I already have some experience at overvolting. I added a battery to my Currie e-zip 750 and it worked out great. I went from 15 mph at 24 volts to almost 30 mph at 36. I’m not expecting that kind of improvement here but if I can increase the voltage on my XM by 20%, I should see an even larger increase in range because I won’t have to push the batteries as hard.
I’ve already ordered another battery, same size and capacity as stock. My plan going in is to simply add the new battery (in the storage compartment) and wire it in series to the top of the stack. I’d like to leave my stock charger across the first five batteries and charge the sixth battery separately with my little Schumacher 12 volt charger set at 4 amps. Here are some of the issues I see:
I’m assuming the stock controller can handle it. From what I’ve read, most people are getting away with it.
I’m a little less sure of the DC-DC converter. I can think of lots of schemes (like powering it with only the first five batteries) but they involve more complications like how do you turn it on? With a 72 volt relay I suppose. Another possibility is to put the new battery on the bottom of the stack and use it for your 12 volt power supply. It’ll be charged separately so balance shouldn’t be a problem. Or I guess I could add another small battery just to handle the 12 volt needs. You’ll still need a relay to turn it on though. The easiest way is to hope the stock converter can handle it.
The stock voltmeter and my Doc Wattson power meter are meant to measure 55-65 volts. Can I just add a resistor to drop my 72 volts back into that range? I’m hoping so. Of course my power readings won’t be accurate but maybe the amps still will be.
Of course the low voltage cut-off won’t work, but I don’t think that will be a problem for me. If you have any advice let me know.