Hi
This thread and the ideas in it will not be for everyone but will work for some.
Although the zephyr has now arrived I have been working on a method of charging my LiPo's reliably, I did not need to charge them super fast as long as if put on to charge in the evening after ridding my bike I had a fully charged battery pack, the resulting charged pack must also be fairly well balanced.
I was looking through my LBS and saw they had electric bikes for sale with LiPo battery packs there did not appear to be any BMS in the battery box and the only input to the charger was a 2 way connector, this lead me to wonder what the bike company knew that I had missed, I had a word with jozzer and was told that now people are starting to charge 10 cell LiPo battery packs with 10 cell Li Ion smart chargers. I thought I would have a go and see what the result was as I use 5 cell turnigy packs I started with the same size pack as in my LBS 10Ah, the battery pack I chose was pretty well balanced, I first charged up the pack with my RC charger to make sure it was full and balanced, I then got out my bank of car bulbs each 55W 8 in total fitted BM6 units to the batteries ND connected up the lights through a turnigy watts up meter the lights were pulling about 400W out constantly I checked there were no problems then left the battery pack and lights to do their work knowing the BM6 units would let me know when the batteries hit their LVC value. It hit the LVC point at about 9.5 Ah I pulled the lights away from the battery pack looked at the BM6 units and found the packs had started to go out of balance, now for the acid test I set up a Li Ion charger to charge up the battery pack with the turnigy meter to let me know what was put into the pack cellogs were fitted to see what the voltage of each cell I started it going first thing in the morning that way I could keep an eye on the battery as it charged.
The charger put in a steady 1.7 amps although it said it was a 2 amp charger, the voltage was 42V more than I expected but not too much, within an hour the packs were virtually balanced the total charge time was 6 hours in the last hour the amp level dropped to less than half an amp. The end voltage of each cell was 4.2 V with a balance value of less Than 15 mV I have repeated this several times with similar results. I also set up a DC to DC converter that controls voltage and amperage to see if I could charge a small lower cell battery I set it up for a 4 cell battery pack and set the charger going it charged up the battery perfectly so now I had a charging system that worked and was small. Now I had to see just how big a battery pack it would charge I have yet to find out the method needed to charge 20 cells but I have found that it can charge a 40Ah battery pack that a friend uses with similar balance results, it took about 11 hours from flat for the 40 Ah pack not too long considering the size.
I now feel safe to put this out on ES I think that with a LVC or LVC HVC board this system would make an ideal slow charging system that can be put on overnight and left alone to do it's job, checking every few months to see how out of balance the pack has got and doing a RC balance charge might be needed I don't know yet. The chargers cost about $45 each not bad for a overnight set and forget charger add in 2 LVC boards a $25 each and you have a system that will be just about perfect for those out there that use 5 cell turnigys.
Geoff
This thread and the ideas in it will not be for everyone but will work for some.
Although the zephyr has now arrived I have been working on a method of charging my LiPo's reliably, I did not need to charge them super fast as long as if put on to charge in the evening after ridding my bike I had a fully charged battery pack, the resulting charged pack must also be fairly well balanced.
I was looking through my LBS and saw they had electric bikes for sale with LiPo battery packs there did not appear to be any BMS in the battery box and the only input to the charger was a 2 way connector, this lead me to wonder what the bike company knew that I had missed, I had a word with jozzer and was told that now people are starting to charge 10 cell LiPo battery packs with 10 cell Li Ion smart chargers. I thought I would have a go and see what the result was as I use 5 cell turnigy packs I started with the same size pack as in my LBS 10Ah, the battery pack I chose was pretty well balanced, I first charged up the pack with my RC charger to make sure it was full and balanced, I then got out my bank of car bulbs each 55W 8 in total fitted BM6 units to the batteries ND connected up the lights through a turnigy watts up meter the lights were pulling about 400W out constantly I checked there were no problems then left the battery pack and lights to do their work knowing the BM6 units would let me know when the batteries hit their LVC value. It hit the LVC point at about 9.5 Ah I pulled the lights away from the battery pack looked at the BM6 units and found the packs had started to go out of balance, now for the acid test I set up a Li Ion charger to charge up the battery pack with the turnigy meter to let me know what was put into the pack cellogs were fitted to see what the voltage of each cell I started it going first thing in the morning that way I could keep an eye on the battery as it charged.
The charger put in a steady 1.7 amps although it said it was a 2 amp charger, the voltage was 42V more than I expected but not too much, within an hour the packs were virtually balanced the total charge time was 6 hours in the last hour the amp level dropped to less than half an amp. The end voltage of each cell was 4.2 V with a balance value of less Than 15 mV I have repeated this several times with similar results. I also set up a DC to DC converter that controls voltage and amperage to see if I could charge a small lower cell battery I set it up for a 4 cell battery pack and set the charger going it charged up the battery perfectly so now I had a charging system that worked and was small. Now I had to see just how big a battery pack it would charge I have yet to find out the method needed to charge 20 cells but I have found that it can charge a 40Ah battery pack that a friend uses with similar balance results, it took about 11 hours from flat for the 40 Ah pack not too long considering the size.
I now feel safe to put this out on ES I think that with a LVC or LVC HVC board this system would make an ideal slow charging system that can be put on overnight and left alone to do it's job, checking every few months to see how out of balance the pack has got and doing a RC balance charge might be needed I don't know yet. The chargers cost about $45 each not bad for a overnight set and forget charger add in 2 LVC boards a $25 each and you have a system that will be just about perfect for those out there that use 5 cell turnigys.
Geoff
