Greetings,
I set out to build a powerbank for camping / Festivals etc and finished it last week.
I used the best cells I had to date that were similar, all from ebike batteries. Altogether I used 160 cells in a 4s40p config. It was 80x LG MG1's, 40x Panasonic NCR18650PF and 40x Panasonic NCR18650BE. They all had close to new capacities, testing in at 3000-3100mAh on the OPUS, the BE cells had 3250-3350 on the OPUS. I split the cells equally per group.
The steel case was originally a battery case all ready. I got these from a customer and the Li-ion puch cells configured in a 13s had all died. Upon pulling them out of the case, thesecond rubber internal case they were inexpanded to roughly double the size and broke open. These cells were really really really dead! and dangerous, but the voltage was super low so no problem there.
The case had some holes in it for the +- cables, charge port and switch but they were too small so I drilled out bigger hols for the 4cm wide USB chargers etc.
I fused them singly because I wanted to keep the option of easily dissasembling the pack again when I want to use the cells for something else.
A 10A fuse between blocks 3 and 4 acts as a mid pack fuse.
I was able to fit 120 cells in the base of the case in a 10x12 and another 40 cells in 2x 2x10 on top of these. lying flat, essentially in the top part of the case.
From the 4s BMS I used another fuse to connect to the 3 way position switch I had. Output from the swtich has another 10A fuse that then splits up into the two 12-24V dual USB chargers. Another positive goes to the magnetic Rosenberger charge port. BMS shares the same +- for discharge and charge. *** I have not yet tried to charge the battery yet because I still havnt managed to empty it...... :**
The current draw would be so low (max 8.4A at 5V so about 2 A at 16V (cell level) that I really did not have to worry about equal loads etc.
The one USB charger has a voltmeter built in, that way I know the capacity and I didnt have to bother with another device.
For some reason the packwere at 16.6V, but the BMS only ouputed 16.07V??? Anyone know why? cheap chinese BMS maybe?
I then added a lot of silicone around the switchto stop potential water ingress, and the terminals to glue them in place. The USB chargers and Rosenberger are waterproof all ready.
Padded the case with thick foam, hard plastic sheetand foam gives a safe layer between the 40cells on top and the 120 underneath.
Lots of duct tape covers all the contacts
Closed up the lid with a lot of silicone again, popped in the screws and let it dry.
Ended up using this for 5 people for 4 days all ready, charging phones and speakersand running 2 USB fans constantly.
remaining voltage, 15.6 from the 16.1 I started with.
Total weight, about 8kg.
Total capacity, about 1640Wh. (2850mAh average x 160, x 3.6V )
If I end up using it more I will add a proper 12V output socket as well so I can power some more stuff.
I set out to build a powerbank for camping / Festivals etc and finished it last week.
I used the best cells I had to date that were similar, all from ebike batteries. Altogether I used 160 cells in a 4s40p config. It was 80x LG MG1's, 40x Panasonic NCR18650PF and 40x Panasonic NCR18650BE. They all had close to new capacities, testing in at 3000-3100mAh on the OPUS, the BE cells had 3250-3350 on the OPUS. I split the cells equally per group.
The steel case was originally a battery case all ready. I got these from a customer and the Li-ion puch cells configured in a 13s had all died. Upon pulling them out of the case, thesecond rubber internal case they were inexpanded to roughly double the size and broke open. These cells were really really really dead! and dangerous, but the voltage was super low so no problem there.
The case had some holes in it for the +- cables, charge port and switch but they were too small so I drilled out bigger hols for the 4cm wide USB chargers etc.
I fused them singly because I wanted to keep the option of easily dissasembling the pack again when I want to use the cells for something else.
A 10A fuse between blocks 3 and 4 acts as a mid pack fuse.
I was able to fit 120 cells in the base of the case in a 10x12 and another 40 cells in 2x 2x10 on top of these. lying flat, essentially in the top part of the case.
From the 4s BMS I used another fuse to connect to the 3 way position switch I had. Output from the swtich has another 10A fuse that then splits up into the two 12-24V dual USB chargers. Another positive goes to the magnetic Rosenberger charge port. BMS shares the same +- for discharge and charge. *** I have not yet tried to charge the battery yet because I still havnt managed to empty it...... :**
The current draw would be so low (max 8.4A at 5V so about 2 A at 16V (cell level) that I really did not have to worry about equal loads etc.
The one USB charger has a voltmeter built in, that way I know the capacity and I didnt have to bother with another device.
For some reason the packwere at 16.6V, but the BMS only ouputed 16.07V??? Anyone know why? cheap chinese BMS maybe?
I then added a lot of silicone around the switchto stop potential water ingress, and the terminals to glue them in place. The USB chargers and Rosenberger are waterproof all ready.
Padded the case with thick foam, hard plastic sheetand foam gives a safe layer between the 40cells on top and the 120 underneath.
Lots of duct tape covers all the contacts
Closed up the lid with a lot of silicone again, popped in the screws and let it dry.
Ended up using this for 5 people for 4 days all ready, charging phones and speakersand running 2 USB fans constantly.
remaining voltage, 15.6 from the 16.1 I started with.
Total weight, about 8kg.
Total capacity, about 1640Wh. (2850mAh average x 160, x 3.6V )
If I end up using it more I will add a proper 12V output socket as well so I can power some more stuff.