? Balancing parallel batts

[Dougiestyle]

I want alot of charge capacity. I'm planning on running 4 18500 or 18650. In looking at battery packs and coming across the battery balancing issue, I'm wondering if this will work :
http://www.hobbyking.com/hobbyking/...6S_50W_5A_Balancer_Charger_w_accessories.html

Ideally, I'd like to plug the mod in at night and have a good charge for a full day or more. Any suggestions about wiring the batteries with this particular charger? How many amps would be safe to charge 4 protected cells?

I just want to go about this with safety and excellent performance. The excess batteries will be to power a boost circuit that is prone to draw alot of amps, if you're wondering.

 

[Java_Az]

That charger would charge batteries in parallel but it wont balance them. Balancing is for battery packs wired in series. So you would have to have at least a 2S battery pack for it to balance after the charge. Really it is a bit overkill to balance a 2S pack. Personally i wouldn't use a balancer unless i was using a 3S or higher battery pack. What your wanting to do is put 4 batteries in Parallel so that would be a 4P set up. Really the proper way to do that so you can charge them all off the same charger is to make a pack and use one protection circuit made for multiple batteries @ 3.7 volts like this one Protection Circuit Module (PCB) for 3.7V Li-Ion Battery (8.0A limit). you would use unprotected 18650's with tabs and make a pack with that protection PCB. For singly protected 18650's i would charge them by them self's or in a dual channel charger that most people use.

 

[Dougiestyle]

I intend to make a semi-sealed (vented with blow-out plugs) battery compartment and all other components installed into the upper compartment. The batteries will have neg and pos contacts that would be comparable to ceiling and floor of the lower compatment. So, I could basically wire the PCB that you linked to the charger port and use a 4.2v charger? Does this PCB limit output of the batteries? As the Kick by Evolv demands high amp draw, I'd hate to limit it's production. I believe 8A is enough, tho. The function of the PCB is to regulate charge current? This will work with IMR batteries?

 

[CraigHB]

You can treat a parallel pack the same as a single cell. The only thing you have to watch out for is big currents occurring between the cells if there's any charge mismatch when initially connected.

If you want to remove and replace the cells regularly, you will have to make sure they all have the exact same charge level (measured voltage) when installing them in the pack. An easy way to do that is to install them only when they've all completed charging using the same charger. Another way to do it would be to use built-in charging or a dedicated charger connector so the cells never have to be disconnected from each other. The latter would be my recommendation.

Since you are using four 18650s or 18500s in parallel, there should be no need to use an unprotected cell and I would recommend against it. For example, a protected 18500 has a drain limit of 3 Amps. With 4 in parallel, you have a drain limit of 12A which is more than enough for any mod. A protected cell will guard against any condition that could be hazardous including high equalization currents, but that's not something you want to rely on routinely.

 

[Dougiestyle]

That makes sense. Would a small 3.7v charger like an eGo USB work for on-board charging of ~4-8Ah? I ask, because, ideally, the PCB is small enough to fit in the box I have planned. I'm guessing charge time would be increased. Would it be beneficial to parallel 2 ego chargers to keep charge time under 8hrs?

I would hesitate to assume that each cell would not match the parallel cells if they are all in constant contact pos and neg. Any scenarios that come to mind?

 

[CraigHB]

You might be able to parallel chargers, but I would avoid that. I've never thought about it so I can't say for sure if it would work okay or even be safe. You'd be experimenting with something like that and it's better not to mess around when charging Li-Ions.

An eGo USB charger, gives you around a 400mA rate which would be a minimum of 15 hours for a parallel pack with a total of 6 amp-hours. Four protected 18650s would have at least 10 amp-hours capacity so that would be a very long charge cycle.

I would use one of these which will give you a 1A rate. That would be approximately one hour of charge time per 1000mAh of capacity. Use a USB charging adapter with that, typically a wall wart. MadVapes sells a good one with 2A output capability. Better to use a supply with a higher rating than your demand to be sure it's not over-loaded at all.

As long as the negatives of all cells are connected to each other and postives of all cells are connected to each other they will remain balanced regardless of how fast the pack is discharged. The same is true for charging. The only time they will be unbalanced is if they are removed then installed with mismatched charge levels.

 

[Dougiestyle]

Thanks for the link! That's a perfect size! Out of stock tho Subscribed for email notification. Thanks CraigHB! That site's prttey neat, too. Never knew it was there.

 

[WillyB]

... As the Kick by Evolv demands high amp draw, I'd hate to limit it's production.

No it doesn't, it's only a 10W device.

 

[Dougiestyle]

Got the email notification yesterday and ordered that charger circuit from adafruit. Going to assemble a solar chrager, as well. Would a 5V/3A regulator be too much for that PCB?

 

[Java_Az]

At one amp it is going to take around 16 hours to charge 4 2600mah 18650's wired in parallel. The way i was talking about doing it, you could have used the charger you posted from hobby king set it to s1 or 4.2 volts and charge at 3 amps or i even higher if you used quality cells to make the pack. here is a link to a pre made 3.7 volt 18650 x4 battery pack made by a pro. It incorporates the 8 amp PCB that i linked to in my first post. Customize Li-Ion 18650 Battery: 3.7V 10.4 Ah (38.48Wh, 4A rate) wrap with black PVC it is a flat pack which might be tough to make a decent mod with i was thinking you would want to make a square one for a PV. By making a battery pack with brand new batteries of the same type and batch you ensure that batteries don't get mixed up or mismatched which can be dangerous.

Would a 5V/3A regulator be too much for that PCB?

If by PCB you mean the adafruit charger then no not too much, it would work just fine to power the charger. The 3amp is max rating doesn't mean it puts out 3 amps when hooked up. It would put out around 1 amp when hooked to that charger well under the 3 amp maximum.

So, I could basically wire the PCB that you linked to the charger port and use a 4.2v charger? Does this PCB limit output of the batteries? As the Kick by Evolv demands high amp draw, I'd hate to limit it's production. I believe 8A is enough, tho. The function of the PCB is to regulate charge current? This will work with IMR batteries?

Yes you would use a 4.2 volt charger. Yes it does limit the output of the batteries to 8 amps. 8 amps is way more then you would ever need for any atomizer you wanted to use. No the Protection PCB for the battery pack does not regulate charger current unless it was over 8 amps. charge current is regulated by the charger chip. Yes this could work with IMR batteries but it is hard to find them with tabs. Batteryspace is the only place i know of to get IMR's with tabs. Tabs are spot welded on to the batteries so they dont heat up to a damaging temp that solding them can do. Nice thing about the IMR's are they don't vent violently like Li ions do when they go terminal. Imr's just kinda ooze their insides out slowly.

 

[Dougiestyle]

Thanks Java Az! Alotta good info there, bud! I have an avenue I plan to travel now. Instead of 4 18650s, I've determined 2 18650s will be enough for all-day *even pushing a booster. I'll use the 1A charger, but intend on keeping a 5V/1300mah solar battery pack on-hand. I work outside, so may as well put the sun to use for more than skin cancer lol.

Thanks for all the help and info, y'all! I'm getting there quickly. It's just not fast enough for my aspirations and brainstorms. You guys rock! Thank you!