eBike Battery

[Ayydan]

Just want to track the progress of the battery updates, currently running a top end balance, currently the lowest cell is 200mV behind the highest. Hopefully it doesn't take too long, but I don't like that I can't trust the LED on my "charger". 

The active balancer will allow it to balance everywhere but the top end, so hopefully it'll improve the charging speed since my top end balancing only happens at about 50mA. Will update when I have that setup.

In other news, it turns out that knocking over a battery and snapping off the charging plug is a great way to smoke a barrel jack. I'm just glad that I had the thing already open for this testing or it'd have sucked to replace.

[Ayydan]

Alright, just completed a 4A discharge test, I was able to get 476Wh out of the pack, with a nominal wattage estimate of ~750Wh, which give ~63% of the packs theoretical capacity, which almost exactly lines up with the maximum charge the low group is able to reach. Following the test I allowed the cells to return to a float voltage and measured them, 7/10 groups read ~3.7V, 2/10 groups are about 50-80mV below that, and the low group is floating at 3.2V. So most of the groups are a bit below 50% SoC but are getting held back by the weak group. 

At least now I know how far I can trust the pack to go before cutting out until I can get the balancer installed

[Ayydan]

Balancer has arrived, I've got it wired up, with minimal sparking no less. Running a test now, so here's hoping it'll work

[Ayydan]

I waited too long to start the test so I had to interrupt it, but after drawing ~450Wh all cell groups were reading within 50mV and were floating at 3.7V. I'm excited to see the results of a complete discharge tomorrow

[Ayydan]

Full discharge test completed, and the results are in, I was able to pull 706Wh out with a constant discharge of ~160W. I'm honestly so stoked, This effectively gives a 50% increase in my useable capacity! I can't wait for a full capacity range test next. This is the best possible result I could have hoped for!

[Ayydan]

An interesting side effect I have noticed with the balancer. Since it keeps the groups voltages together until around 3.9-4.0v, the weak pack now charges to 4.2v much faster than the rest of the pack. As a result the balance charge function of the BMS has to start sooner, which means overall charge time to reach full is longer than before, but 0-80 is still fast

[Ayydan]

   

New trailer pack is done, and my god is it fun. I hit 30km/h easily, and it got up to ~33 on a straight. Considering the pack isn't even fully charged (the cells sat at a full charge for about a year), the outcome is exactly what I wanted. Still have some work to do on order to clean up the lid, and sealing to reduce weather impact since the trailer will love outside. But otherwise, very fun