Due to being forced to take a second paycut in in 4 years 
but having discovered an excellent local source of free 18650 cells I have decided to build my own 44.4v pack rather than go LiPo ( i had planned to use 4 x 22.2v 5ah packs). A laptop shop gives me them free and only about 20% are turning out to be duff thus far. Though I’m spending many hours of an evening stripping them out/testing, slowly bringing back up to 4.2v !
Nope, it won’t be an light pack, nor have a high C rating. But it will be free and functional - after all I'm using 18650 cells no inside a 8fun botle battery and booster pack) ! There will be a few very cheap sundry items
I would be grateful for input or thoughts on my plan. Which is -
Building 2 x 22.2v 10ah packs and series them to 44.4v. This way I can wire in a 6s balance lead into each pack. This would allow me to charge/balance charge each pack separately using my imax b6 charger (it only goes up to 6s)
I also recall D8veh saying that BMS battery chargers can have the voltage changed by turning a screw inside. If I get one of these then I could charge the whole pack at 50.4v for convenience and balance charge every now and again as required. This is a nice to have and I will bear in mind whilst building but not actually an essential.
All the cells I have are 2000mah Sanyo, 2200 mah Samsungs or 2500mah LG branded. I am going through a very slow and painful process of charging them all up and discharging to discover their actual capacity so I can ensure the cells are acceptable match.
Question 1. I think I need to match both voltage and actual capacity but to what accuracy, I’ve found vastly differing opinions on this over the webbernet ? 0.1v ? and 100mah ? To test the charge they hold I am charging to 4.2v and leaving overnight to see what charge they have in the morning. Most drop to between 4.10 to 4.15 and only drop very slowly thereafter
Question 2. When building a 22.2v pack what is the best arrangement ? I think it would be make 6 lots of 1s5p packs and then series them up ? I think this is better than making 5 x 6s1p packs and paralleling up? In fact I think i answered own question as balance leads dont work the second way
I will need (I think)
•60 x 18650 cells (2000mah) – if I can get higher capacities then I won’t need 60 of them. I’m assuming not so this is the maximum required. I know I do I need 10ah pack to provide the distance/performance I require. (GOT)
•2 x 6s 22.2v balance leads (To BUY)
•2 x lipo alarms (TO BUY)
•Connectors. I’m using xt60 as I like them. Easy to use and seem pretty waterproof if well sealed with heatshrink.(GOT)
•Plenty of wire (GOT)
•A protective case – to be made later once I know the final dimensions. To go into custom frame bag my brother will make for me
Is there anything I have missed ? Always grateful for any input
Many thanks
Kirstin
but having discovered an excellent local source of free 18650 cells I have decided to build my own 44.4v pack rather than go LiPo ( i had planned to use 4 x 22.2v 5ah packs). A laptop shop gives me them free and only about 20% are turning out to be duff thus far. Though I’m spending many hours of an evening stripping them out/testing, slowly bringing back up to 4.2v ! Nope, it won’t be an light pack, nor have a high C rating. But it will be free and functional - after all I'm using 18650 cells no inside a 8fun botle battery and booster pack) ! There will be a few very cheap sundry items
I would be grateful for input or thoughts on my plan. Which is -
Building 2 x 22.2v 10ah packs and series them to 44.4v. This way I can wire in a 6s balance lead into each pack. This would allow me to charge/balance charge each pack separately using my imax b6 charger (it only goes up to 6s)
I also recall D8veh saying that BMS battery chargers can have the voltage changed by turning a screw inside. If I get one of these then I could charge the whole pack at 50.4v for convenience and balance charge every now and again as required. This is a nice to have and I will bear in mind whilst building but not actually an essential.
All the cells I have are 2000mah Sanyo, 2200 mah Samsungs or 2500mah LG branded. I am going through a very slow and painful process of charging them all up and discharging to discover their actual capacity so I can ensure the cells are acceptable match.
Question 1. I think I need to match both voltage and actual capacity but to what accuracy, I’ve found vastly differing opinions on this over the webbernet ? 0.1v ? and 100mah ? To test the charge they hold I am charging to 4.2v and leaving overnight to see what charge they have in the morning. Most drop to between 4.10 to 4.15 and only drop very slowly thereafter
Question 2. When building a 22.2v pack what is the best arrangement ? I think it would be make 6 lots of 1s5p packs and then series them up ? I think this is better than making 5 x 6s1p packs and paralleling up? In fact I think i answered own question as balance leads dont work the second way
I will need (I think)
•60 x 18650 cells (2000mah) – if I can get higher capacities then I won’t need 60 of them. I’m assuming not so this is the maximum required. I know I do I need 10ah pack to provide the distance/performance I require. (GOT)
•2 x 6s 22.2v balance leads (To BUY)
•2 x lipo alarms (TO BUY)
•Connectors. I’m using xt60 as I like them. Easy to use and seem pretty waterproof if well sealed with heatshrink.(GOT)
•Plenty of wire (GOT)
•A protective case – to be made later once I know the final dimensions. To go into custom frame bag my brother will make for me
Is there anything I have missed ? Always grateful for any input
Many thanks
Kirstin
