Hello this is my first post on here, thanks in advance for being here. What do I need to charge 10 18650 cells in parallel? I think I need a pcb charging controller which will monitor each cell to balance the charge out, I have not had much luck finding what I am looking for. It also needs to be on the small side because I have limited room in my flashlight body. I am running a 10 cree with a 3.7v driver. Thanks.
Charging 10 18650's in parallel
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Flashaholic
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Is there any reason why you can't charge them on separate chargers?
Is there any reason why you can't charge them on separate chargers?
If they are all in parallel (no series strings) then you only need 1 charger for them as the voltage input will bring them up all the same. 10 of them in parallel would mean a decent 5A charger for them that would give you 500ma/cell. I'm not sure where to get such a charging circuit out there though.
I have them built into my flashlight body then I just was going to put an outlet on the back to charge through. Plus they are all soldered together. I'll have to build a charger I guess. I was charging it with a 6volt car charger then when it would get to the correct voltage I would quit charging, very time consuming and I think I ruined some cells from overcharging.
I have them built into my flashlight body then I just was going to put an outlet on the back to charge through. Plus they are all soldered together. I'll have to build a charger I guess. I was charging it with a 6volt car charger then when it would get to the correct voltage I would quit charging, very time consuming and I think I ruined some cells from overcharging.
If they are in parallel you either overcharge them all or none of them. The problem is when you charge them at too high a charge rate for the weaker cells those can be ruined and drag down or even cause other issues in the pack. What you have to do is figure out the lowest capacity cell(s) of the pack and adjust your average charge rate so as to not charge those too fast. Also another issue would be if you mix cells the internal resistance of each cell can add into the equation under heavier loads those with higher internal resistance will deliver less current to the load and instead heat up more.
I'm sure there are a lot better experts on these batteries than me out there that can correct me and give additional information.
The recommendation for 18650 I've seen (generically) is about 0.2-0.5C charging rate that is why I mentioned about 5A as that would be about 0.2C average for a pack with 2500mah batteries. You could charge the 10 cell pack at 10A if they were 2000mah batteries or even higher if you don't like waiting but I wouldn't recommend charging too fast with a set of cells that are sealed up in a pack as the heat could build up with no way to escape.
The 5amps for a charge rate is fine with me. I overcharged the whole pack because I wasn't watching the 6volt charger close enough and let the volts get too high.
So if I build a 5 amp charger I want it to put out 4.2v? To achieve the 3.7v? I'll most likely build a cut out so it shuts off when it gets to the correct voltage.
Is there any other suggestions or any reason I should use anything other than 18650's? It's just what I had. Thanks
So if I build a 5 amp charger I want it to put out 4.2v? To achieve the 3.7v? I'll most likely build a cut out so it shuts off when it gets to the correct voltage.
Is there any other suggestions or any reason I should use anything other than 18650's? It's just what I had. Thanks
Buy a cheap hobby charger? ie - https://hobbyking.com/en_us/turnigy-accucel-6-80w-10a-balancer-charger-lihv-capable.html
You don't need to balance them in parallel, only if they are in series. Parallel they will all balance out themselves. That charger could charge them up to 10 amps. Use the li-po charge setting, 4.2v (1S). li-ion are charged with a CC/CV method, constant current until the voltage reaches 4.2v and then constant voltage with reducing current until they are full. I'm guessing your 6v charger is not a li-ion charger and wouldn't recommend it.
I would try and be sure that all the batts are in a similar state of charge before charging them all in parallel. Look out for bad cells.
You don't need to balance them in parallel, only if they are in series. Parallel they will all balance out themselves. That charger could charge them up to 10 amps. Use the li-po charge setting, 4.2v (1S). li-ion are charged with a CC/CV method, constant current until the voltage reaches 4.2v and then constant voltage with reducing current until they are full. I'm guessing your 6v charger is not a li-ion charger and wouldn't recommend it.
I would try and be sure that all the batts are in a similar state of charge before charging them all in parallel. Look out for bad cells.
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DIWdiver
Flashlight Enthusiast
Actually, they need to be in the same state of charge before CONNECTING them in parallel. If you connect a charged cell to a discharged one, fireworks may ensue. Once connected in parallel, it is impossible for them to be in different states of charge.
Lithium ion batteries are actually pretty easy to charge properly. You have to do one thing really well, one thing reasonably well, and one thing okay.
What you have to do really well is the voltage. At 4.1V a cell will take pretty nearly a full charge (IIRC it's around 95%). At 4.2V it will take a full charge, but will take fewer charges before it starts degrading. At a little over 4.2V, it starts degrading much faster.
What you have to do reasonably well is limit the current. To do this you have to know your cells and your goals. Many cells are ideally charged at 0.2 to 0.5C. Some can handle 1C or even much more without a significantly shortened life. You have to know what your cells can handle, and choose how fast you want to charge vs. how many charge cycles they need to last.
What you have to do okay (actually you don't even really NEED to do it at all) is terminate the charge. Once you have your voltage and current limits set up, you hook up the battery and it starts to charge at the current limit. The voltage begins to rise. Once the voltage hits the limit, the battery starts to take less and less current. Once the current drops to 0.05 - 0.1C, you should stop charging. Continuing to charge beyond this point is called a 'float' charge, and will simply result in a shorter battery life (this is not true of all chemistries - Lead-acid batteries love float charge). The lower your voltage limit is, the less critical charge termination is. For best shelf life, a LiIon cell should be kept at around half-charge, or about 3.7V. So a float charge at 3.7V would give great shelf life, but would only keep your batteries half charged. Anything above that is a trade-off.
Cheap hobby chargers can actually do a pretty good job of charging your batteries, especially if you charge and use them frequently. But once you know what goes into making the decisions, you can make a more informed choice about a charger for your particular application.
Lithium ion batteries are actually pretty easy to charge properly. You have to do one thing really well, one thing reasonably well, and one thing okay.
What you have to do really well is the voltage. At 4.1V a cell will take pretty nearly a full charge (IIRC it's around 95%). At 4.2V it will take a full charge, but will take fewer charges before it starts degrading. At a little over 4.2V, it starts degrading much faster.
What you have to do reasonably well is limit the current. To do this you have to know your cells and your goals. Many cells are ideally charged at 0.2 to 0.5C. Some can handle 1C or even much more without a significantly shortened life. You have to know what your cells can handle, and choose how fast you want to charge vs. how many charge cycles they need to last.
What you have to do okay (actually you don't even really NEED to do it at all) is terminate the charge. Once you have your voltage and current limits set up, you hook up the battery and it starts to charge at the current limit. The voltage begins to rise. Once the voltage hits the limit, the battery starts to take less and less current. Once the current drops to 0.05 - 0.1C, you should stop charging. Continuing to charge beyond this point is called a 'float' charge, and will simply result in a shorter battery life (this is not true of all chemistries - Lead-acid batteries love float charge). The lower your voltage limit is, the less critical charge termination is. For best shelf life, a LiIon cell should be kept at around half-charge, or about 3.7V. So a float charge at 3.7V would give great shelf life, but would only keep your batteries half charged. Anything above that is a trade-off.
Cheap hobby chargers can actually do a pretty good job of charging your batteries, especially if you charge and use them frequently. But once you know what goes into making the decisions, you can make a more informed choice about a charger for your particular application.
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I know the 6volt charger wasn't correct for the battery array. That's why i am on this forum so I can figure out what I need to do so I don't have to babysit the incorrect charger. All the cells were new and evenly charged before I soldered them into parallel, everything has been fine because I have a dmm hooked to the charger and with the voltage drop blah blah I have been watching it until it gets up to the correct voltage then terminating the charge manually. This has worked for almost a year but I knew I would have to find a better method of charging eventually and since I overcharged and ruined 10 cells the time is now. Thanks for sharing your knowledge with me, I am an electrician but don't have much experience with the 18650's yet. Thanks again.
