i want to make 18650 battery pack for my bicycle light. I know that this topic was actual already before, but i didn’t find any useful information regarding this. So, the idea is to connect 3 or 4 pieces of protected 18650 in parallel. Why … because they are usual batteries i use around home and always have couple of spare pieces somewhere. Why parallel , because i will use sipik68 clone and want to have long runtime. The problem is that i can’t find anywhere normal charging pcb board for 3 or 4 batteries with balance capabilities, and want to use only 12v or similar power adapter for charging.
I would shy away from 18650 packs unless you plan on making a holder where they can easlie added and removed since balancing with them would be difficult and it would cost more than buying a premade pack. Protected lions are expensive too and while I like using them in my handheld lights (Since someone cant run them down, cause them to vent/explode as easily) they are just too expensive and heavy for me to use in packs.
At the very least I’d buy a tap and use a hobby charger that is balance equipped (Or just a balance charger) to charge the cells so they all get charged up equally. A monitor could be used to hook up to the balance tap to check individual cell voltage state as well.
I would go with a premade lipo pack and hobby charger since lipo’s are cheap and will easily work for modern light current needs (long as you properly size them) and hobby chargers are pretty affordable and can be used for charging your lions as well. Look at company’s like HobbyKing and other hobby shops to get better pricing than premade “Light”systems.
I’m not sure that I’d go with a “Mystery Charger” (That’s its name! :0) but if it charges alright though a balance charger it should work fine. I’d still recommend looking at lipos if you plan on using it soley for cell use since since you wouldn’t have to solder and wire up the pack. Long as you use the Lipo’s safely (Like unprotected cells) then you shouldn’t have any issues, you could even wire up a monitor to it to tell you active charge state (But be sure to unplug it since it draws power).
I partially forgot what i have learned on my electrical engineering classes long time ago… so what will happen if i take for example 3 batteries with different voltage each… furthermore, I’m pretty sure that charging current will be to low if i put this circuit board on. 1000 mA / 3 = 333 mA per cell or 250 mA for 4 cells
besides that, what are the options for 8.4v version … 2 + 2 cells …
put it more simple. You probably already have charger for single 18650, don’t you? I’m assuming you have if you use them elsewhere.
What I recomend you is just buy some type of 98 zoomie and carry few spares 18650 along. You might get Ultrafire SK 98 below $10. On low mode you’ll have aprox. 2h runtime with one NCR18650A.
If you want to make a pack, then balance them to the same voltage, then properly solder/weld them together in parallel. Since it’s parallel, there is no balancing needed as they all have the same voltage, you’re only increasing capacity and possible current output.
Charge the pack as any other single cell Lion, as they are 4 of them you can pick some charger with a bit of more charging current according to the batteries you use.
It’s best to connect batteries of the same type, size, brand, age, capacity, internal resistance. I would certainly try to stick with the same capacity and similar internal resistance.
Protection of the pack is the same as a single cell.
If you wire them up in series, you should balance charge the pack and also have a monitor, alarm, protection of every part of the serial pack. 2S2P = 2 parts, 4S1P = 4 parts.
If you want a big capacity and 3.7V just do the 1S4P and all the balancing troubles go away. Plus for more cells in series you would need a proper charger, like the above linked hobby charger Turnigy Accucel 6.
