booster for my BBS 02 48 volt

I have a BBS 02 750 watt with a 11.6AH 48 volt battery.
When the battery is freshly charged things are very good.
By the time the battery is down to half charge things are a bit more lethargic and the performance is not so good.
I could fix the problem by adding an extra cell set in series and am tempted to go that way but........

As a radio amateur I have similar problems when operating mobile 12 volt radio transmitters which pull ~25 amps at peak and the output level is very sensitive to battery volts as soon as the engine stops. So to fix this problem we have a unit called "battery booster" which keeps the output at full volts.

I am thinking of doing something similar for my BBS 2. So that the output would always be at (say) 55Volts on to the controller even as the battery output falls. Then when my 13S battery drops to (say) 40 volts drop the booster out and still have a bit of charger to limp home on.

First is there anything out on the market that is doing something similar ?
second what would the group think of such a gadget.

I have the skills to make one and it would be something fun to do, and may just do it anyway.

Regards Bob

Hi Bob

Welcome to ES. Alan, W6AKB here.

Folks have talked about doing something along those lines, but as far as I know no one has done it. The power levels involved here are a bit higher, not so easy to do due to weight and volume at the required current, and the losses will eat some energy and reduce your range. Probably simpler and better to add a cell.

Get a better controller, 20s battery, and you'll have badass performance until the cells deplete. The motor will love the increased voltage.

The BBS02 controller is integrated, so changing to another is a major increase in complexity and you have to deal with locating it and the wiring. Not too many folks consider that seriously. However an FOC PhaseRunner would be excellent.

The BBS02 controller has a voltage limit of 60V so 14S is about all that is practical, but it is a useful improvement. To go up from there perhaps move to a BBSHD.

Another option to maintain more consistent performance is to change to LiFePO4 chemistry with a flatter voltage discharge curve.

Thanks guys. As they say watch this space. The size and power is not too bad, I am running the motor at a 20 amp current limit at the moment so for a 15 volt boost and 20 amps that's 300 watts and I would go for ~95% eff ie an extra 15 watts of losses. even at 90% that's only 30 watts extra. So its doable. The main thing was has someone done it already. I suspect I will start with a hacked computer power supply and go from there.
Before I get busy does anyone in Australia have 6 good cells for me or a local source?

change your pack to a chemistry with a flatter discharge curve like lifepo4

that's my issue also w/ these NCA cells that i'm using w/ the bbs02. 4.2v full, 2.5v empty. a huge voltage swing.

you could also try manually and incrementally connecting 1S segments to keep your voltage up. but it would be tedious...

You're starting to tempt me. Part of the problem also is the way the BBS (and most of the drives) work. There is no "regulation" and the fall off in performance is very noticeable as the battery gets discharged. And yes one of my fall back plans is to have another 1S plenty parallel cell available to hook in. The peak volts seem to be a bit close to the limit for the controller, but it seems that its working for some people.

Again looking for cells inside of Australia that I can make into the extra "bit" that I need any offers ?

Regards Bob :?