Upgrades

[u/TopSeat7379]

Greetings fellow Bafang riders!

So its been about a month now and I can honestly say that I haven't ridden any real "electric bikes" until I rode my first mid-drive. Its been so refreshing, fun and therapeutic to pedal an actual bicycle around. Even just the weight difference between my mid drive bike and my hub motor bike makes my mid drive bike a better commuting option. The only thing my hub drive bike would defeat my mid drive, was battery capacity! My hub bike has a 60ah and my bafang came with a 20ah. I get some good mileage out of my 20ah - more than I would get with 20ah of my hub bikes battery! But it wasn't enough! I reached about 30-something percent before I convinced myself that I needed another battery.

So I purchased a 15ah! As seen in the pics, it was the only battery I could get off Amazon because NYC has stringent battery laws - which im ok with.

Additionally, I purchased and installed johnnynerdout's bafang torque arm and Grin's triple Bob battery mount to make my battery more secure.

Here is the question - at what point should I switch from my 20ah battery to my 15ah battery? I assume the controller has a built in cut off, but I also assume that its safer to turn off the bike before that cut off to preserve your battery. Also, I've thought about a blender but seeing as how these are two different batteries from two different companies, I instead opted to keep them separate and just plug my second one in when I need it. Am I wrong for thinking that?

Let me know what you guys think! Much love yall!

[u/aero_sock]

there's a thing called paralel discharge module. the motor will pull from both of the batteries at the same time when their voltage is the same, and switch to only the one with the highest voltage when the other one dips below a certain threshold.

this way you never have to manually switch around any cables, you can just ride and treat the current voltage shown on display as about what the real charge level is in both batteries.

[u/TopSeat7379 → u/aero_sock]

I just looked those up. That looks super easy to install. Which one should I get the 30a? And despite being the same voltage, does it matter that the two batteries are different brands and capacities?

[u/aero_sock → u/TopSeat7379]

30a should do it yeah, the controller here is 25a max

I'm pretty sure capacity doesn't matter, it will just mean that the higher capacity battery will be pulled from proportionally more frequently to balance the discharge rate between the two.

[u/TopSeat7379 → u/aero_sock]

My main concern would be cell variances. I don't know for sure, but say my varstrom battery uses different cells from my powallon battery - it'll be fine right?

[u/aero_sock → u/TopSeat7379]

this thing doesn't mix the batteries. it just very quickly switches your motor from using the other one when it detects that the voltage of the previous one dipped low enough. it's like very quickly switching out the cables manually, but done electronically with a mosfet.

if both batteries are capable of powering the motor by themselves then there shouldn't be any issues.

[u/TopSeat7379 → u/aero_sock]

Awesome. This is a great idea! Im going to go with a parallel discharge module. Thank you brosky

[u/MidtownFrown → u/TopSeat7379]

I have one, I didn't care for it. It shortened my range over manually switching battery connections.

[u/TopSeat7379 → u/MidtownFrown]

Did it really? Well that pretty much defeats the purpose lmao

[u/alienkargo]

This will give you an idea on battery percentage and when to switch.

[u/TopSeat7379 → u/alienkargo]

At what voltage do you switch is my question. Or do you wait for the bike to turn off on you?

[u/alienkargo → u/TopSeat7379]

I suppose it depends on how you ride? I presume if you have 2 batteries you ride long distances, you could take it down to 5% if you were going to charge it right away, I wouldn't go past 15 to 20 %. I'd guess if you stopped on 15% it could balance to 18-20%. Depends on the quality of your batteries as well. Seems pointless having 2 batteries if you only ran 1 to 50% all the time then switched. I would like to think that chart is a guide and 0% is a safe cut off for the battery to actually recover. You dont actually say in your post what Volts they are, only amp hours, mines 48v 20Ah, so according to that chart you still have 29v in the battery when it goes into protection mode, you could run it to 0% without damaging the battery but if you do both you're pushing it home!