15s BBS02b

Just data for anybody that can use it. 10/19 purchased BBSO2 48v 750w mid Drive from em3ev.

I built a 15s battery pack from 12.5aH lithium soft pouches. No BMS and I am using an Active Balancer 1.2amp. I use Low Voltage cell monitoring to alert me when my cells get to 3.2v.

I bought a 15s battery charger with fan from Aliexpress. With the internal potentiometer adjustment pot I was able to lower the charger voltage down to 61.5 which was as low as the adjustment would allow.

My 15s pack now charges to 61.5v (4.1 per cell). My BBS02 gives me an OVER VOLTAGE (07) until i drop the voltage to 61.3v using a standard light bulb for a minute.

My reasons for building the 15s pack is simply because I had only enough cells to build 1p15s so I made it work.

Pros:
The pack is fast to charge using 3 amp charger and only charging to 61.5 volts.

Even when the pack is low enough to need charging the mid drive performance is still very perky due to the voltage.

My 15s battery pack discharging to only 48 volts before recharging to 61.5 volts should provide a long battery life.


Cons:
I have to drain the battery for 60 seconds(60watt load) in order to lower the voltage before riding.


Happy riding.

Thanks for sharing, seems worth it. Stock controller?

keithvi225@gmail.com said:

No BMS and I am using an Active Balancer 1.2amp. I use Low Voltage cell monitoring to alert me when my cells get to 3.2v

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Can you link to the devices you are using?

To me, BMS is just a collection of functionality, however implemented, rather than a single gadget.

In what voltage range do yo balance, i.e. top or bottom?

By "no BMS" I infer you rely on the charger alone to stop-charge, no additional HVC.

And also no LVC at all, rely on the rider to avoid allowing any one cell to go to low.

No OCP? Temperature ?

The active balance board balances anytime voltage's exceed 0.2v between cells.

The Lipo cell alarm lets me know when my cell voltages Get Low.

This is not something I recommend unless you are willing to experiment. So far I've been pleased.

Yes, Stock controller! No overcharge protection other than my 61.5v charger is unable to meet or exceed my packs limit of 63v.

most of those controllers are only rated for 63v max or they fry if not protected. yours is protected. ive been running my packs without a bms on 2 15s5p packs in parallel charged to 61.5v and after 4000km not an issue but they were second hand before I got the cells. I bottom balanced the packs before charging them and then you don't top balance them and its worked for me.

goatman said:

most of those controllers are only rated for 63v max or they fry if not protected. yours is protected. ive been running my packs without a bms on 2 15s5p packs in parallel charged to 61.5v and after 4000km not an issue but they were second hand before I got the cells. I bottom balanced the packs before charging them and then you don't top balance them and its worked for me.

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Thank you for confirming Goatman. I had a few used pouch cells that I wanted to put to use and 15s was the best I could do. I hope the active balancing board keeps them all somewhat together.

I hope it's understood that I put a very low value fuse in place in case things go south.

when I bottom balanced I went to 3.0 volts on each cell then charged to 61.5v like you do. when your pack is charged all your cells may not be 4.10v but that's ok. I was using second hand cells and messing around with what voltages I wanted before buying a bms. I was at 14s with a bms then went 15s and blew a couple controllers for various reasons and decided to go 14s again to save controllers, didn't like it so I bought a phaserunner controller and am going to go to 16s. I liked 15s but I wanted a little more power and range. id rather more volts for power than amps once I have the AH I want

I have been running a full charged 15s2p 5ah battery on my Tongshen tsdz2 midrive for 1.5 years and for over 2000 miles. I also ordered an adjustable charger but it was DOA so I bought a cheap non adjustable one (63v1a) for $12. If I charge the batteries and wait a few hours the battery works fine right from the start, but if I try to use it fresh off the charger I have to turn on the running lights and pedal for a block or two before the assist will kick on. I had to go with a 15s battery because I was flying overseas and bringing my bike and I needed batteries under 100wh each to take them on the plane in the cabin. My 3x $20 Hercules 20v 5ah batteries (samsung 25R cells) are stamped 90wh each and all 3 sailed through TSA without a question.

I have not had any issues except for a display issue, when I reach the inactivity timeout the display turns off but assist remains on low and pressing the on/off button on the display won't turn it back on. I have to disconnect the battery for a second and reconnect and that turns the display on (it is not supposed to turn on that way though, I am supposed to press the button after connecting the battery to turn it on). I am not sure if this error is due to the overvoltage or just from lots of use as the bike has over 3000 miles so far.

I agree that I like the extra voltage, the motor has much better power through the entire battery range. I can also run my battery further down when necessary as I start at 63v and can run it all the way down to 43v if necessary (although I seldom do).