Battery pack for
barakta's electric assist trike:
Ping 20Ah 48V LiFePO4 battery, BMS and auxiliary electronics, built into Rixen & Kaul rear carrier box.
Speakon connector (one of the posh reasonably weatherproof ones) for the trike power, XLR internally for the charger (60V 5A switching power brick, on the left). IP67 illuminated main switch.
Two seperate weatherproof enclosures, mainly due to awkward size:
On the right, the SignalLab battery management system (Ping enclose this in shrinkwrap, which seems suboptimally robust). I've tapped into the thermal cutout header to provide a remote shutdown switch, avoiding the need for a high-current isolator to turn everything off. The 16 blinkenlights indicate when the series cells have reached full voltage.
On the left, a Turnigy 130A DC power meter (this only measures current flowing *out* of the battery, unfortunately, but is cheap, accurate
[1] and draws minimal power), DC:DC converters to efficiently step down the 52V nominal (can reach 60V when on charge) buss voltage to 7.5V for the trike's dynamo lighting, and 5V for USB charging. (The e-bike console is wireless and charges from USB, so it seemed like a good idea to integrate this.)
I've used a regulator board designed for power-over-Ethernet applications for the first stage converter, and the lovely Recom 78B5.0-1.5 regulator (a drop-in replacement for the 7805) to provide the 5V. Crowbar circuit and fuses to give the converters a fighting chance if something bad happens. There's a relay to latch the BMS shutdown in the 'on' position while the charger is connected (so it doesn't fail to charge because you forgot to switch it on), which also disconnects the power to the lights.
As ever, it's the tedious mechanical stuff that I've been half-arsed with. I couldn't get encosures with transparent lids in an appropriate size, so had to cut holes and fix clear acrylic windows. Cable-entries are a botch. Hot-melt glue used to excess.
The battery itself I've mounted to a sheet of 1.5mm aluminium, which is free-floating on a layer of closed-cell foam at the bottom of the box. It's a snug, rattle-free fit with the lid closed, and protects the battery from the screws and fittings on the inside of the box.
[1] With the disclaimer that it doesn't seem to register current until it's in the 100mA range or so, which means the quiescent power of the motor controller, electronics and bike lighting doesn't show up. This is actually useful, as it means the elapsed time clock stops when the motor isn't doing work.