Ok, I've been reading threads and I've got a headache now. I plan on making a battery pack with 18650 batteries. Looking at 14.8v 5200mAH. I plan on installing a PCB and a Polyswitch for protection. My question is.....Do I need protected batteries or will I be supplying the needed protection with the above components?? Thanks fellas....
Protected or not??
- Thread starter bncrshr77
- Start date
Help Support Candle Power Flashlight Forum
VidPro
Flashlight Enthusiast
well yes, you will certannly want protection especially with the cells in series.
BUT
like you said, if you put in PACK protection PCB and its descent fully center-tapped each battery protection, then that IS protection.
Pack protection is completly sufficent to protect each of the cells, when done correctally, and can even have thermal protection too.
which just leaves the Addition of tapped out for balancing for charging. if you tap out the cells for proper balance charging too, then you will be able to properly charge it also, and it will last a long time.
BUT
like you said, if you put in PACK protection PCB and its descent fully center-tapped each battery protection, then that IS protection.
Pack protection is completly sufficent to protect each of the cells, when done correctally, and can even have thermal protection too.
which just leaves the Addition of tapped out for balancing for charging. if you tap out the cells for proper balance charging too, then you will be able to properly charge it also, and it will last a long time.
You wouldn't happen to have a diagram or anything showing me what you mean by "Tapped out"? I've read a hundred forums on li-ion batteries and I'm more confused now than when I started!! The pack I'm planning on building is 14.8v 5000mAH. I know I need 8, 3.7v 2500mAH batts wired in a 4s2p configuration. I was looking at an 8amp PCB and 7amp Polyswitch from batteryspace that they use on their pack similar to what I'm building. Is there a simple diagram or drawing of how to properly wire this configuration up?
Tap as in what you do to a keg, not what you do when someone puts you in a leg lock.
If the pack has a tap for each cell so you can access them individually, you could perform balancing and diagnostics at any time without disassembling the pack.
If the pack has a tap for each cell so you can access them individually, you could perform balancing and diagnostics at any time without disassembling the pack.
VidPro
Flashlight Enthusiast
|protection| pcb conn|ctions . .|
|{======]|{======]|{=====]|
| Balance. | charge co|nnections|
center tapped, center being between the 2 cells, probably a bad way to say it.
Tapping: to feed-tap-wire off of the batterys connection points
tapping each cell unit at its postive and negative points.
the protection PCB will Usually have some minor instructions, and a B+ B- B1+ B2+ type of connection data, so it wont be hard. (B meaning battery + meaning the top postive connection point)
|{======]|{======]|{=====]|{=====]|
|{======]|{======]|{=====]|{=====]|
|B+ . . . . .|B2+ . . . . |B3+ . . . |B4+ . B-|
the setup your talking about is like this, you get a 4X li-ion protection for a 14.4 pack protection , and wire the connection points of the battery and the center taps, to the protection PCB. then on the other side (electrically) of the PCB you connect the "load" and the "charge" the output + -.
but to BALANCE the pack for charging, which is highly recommended, you tap off of the SAME 5 points you sent to the PCB (or just tap the same points off the PCB itself), and that goes to your Hobby balancing charger thing.
all this making it sound much harder than it is.
Balanced charging will finish the charge like this
|{==4.2V==]|{==4.2V==]|{==4.2V==]|{==4.2V==]|
instead of this
|{==4.1V==]|{==4.0V==]|{==4.2V==]|{==3.8V==]|
This being when protected,
with protection, you cannot do permenent damage, you just do not get a full charge on all cells, without balancing.
it will get even worse than that without protection
|{==4.1V==]|{==4.0V==]|{==4.4V==]|{==3.8V==]|
without protection even with a proper charger , you could permenetly damage a cell
so with balancing during the charge, all the cells will be balanced up to the same charge voltage (which doesnt define the same exact capacity, but then nothing could do that)
|{======]|{======]|{=====]|
| Balance. | charge co|nnections|
center tapped, center being between the 2 cells, probably a bad way to say it.
Tapping: to feed-tap-wire off of the batterys connection points
tapping each cell unit at its postive and negative points.
the protection PCB will Usually have some minor instructions, and a B+ B- B1+ B2+ type of connection data, so it wont be hard. (B meaning battery + meaning the top postive connection point)
|{======]|{======]|{=====]|{=====]|
|{======]|{======]|{=====]|{=====]|
|B+ . . . . .|B2+ . . . . |B3+ . . . |B4+ . B-|
the setup your talking about is like this, you get a 4X li-ion protection for a 14.4 pack protection , and wire the connection points of the battery and the center taps, to the protection PCB. then on the other side (electrically) of the PCB you connect the "load" and the "charge" the output + -.
but to BALANCE the pack for charging, which is highly recommended, you tap off of the SAME 5 points you sent to the PCB (or just tap the same points off the PCB itself), and that goes to your Hobby balancing charger thing.
all this making it sound much harder than it is.
Balanced charging will finish the charge like this
|{==4.2V==]|{==4.2V==]|{==4.2V==]|{==4.2V==]|
instead of this
|{==4.1V==]|{==4.0V==]|{==4.2V==]|{==3.8V==]|
This being when protected,
with protection, you cannot do permenent damage, you just do not get a full charge on all cells, without balancing.
it will get even worse than that without protection
|{==4.1V==]|{==4.0V==]|{==4.4V==]|{==3.8V==]|
without protection even with a proper charger , you could permenetly damage a cell
so with balancing during the charge, all the cells will be balanced up to the same charge voltage (which doesnt define the same exact capacity, but then nothing could do that)
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Thanks for the replies VidPro! Ok, i've done a bunch more reading of threads specific to 4s2p pack building and I've got all the basics figured out. I do understand the dangers involved with li-ion batts. One thing I'm still not sure of is do I need a PCB with balancing function or the 5 lead balancing wire or could I use either one? It would be great if someone had a detailed picture walk through of a pack build similar to the one I want to build!!
VidPro
Flashlight Enthusiast
the Protection PCBs with built in balancing look pretty useless COMPARED to just having a connector with the 5 connections, that plugs into a hobby type charger, and Fully charges each battery.
if the PCB had in it a balancing charger itself , or full balancing curcuit stuff that you plug in power to, and it CHARGES balanced, then that would be good.
instead
the balancing Protections (from thier data sheet) just discharge the cells that are higher than the other ones , pretty lame way of doing it.
Without any actual knowledge , i suspect that the things would probably end up having more "parasitic" drain (teeny tiny discharges) than the normal protection. And that the acuracy of the balancing is not as good as charge balancing.
PLUS
with hobby charger balancing you can SEE things, you get loads of usefull info, like the final voltage of each cell, and the current, and have a good idea the batteries are working as they should. and Now you can get all that for as little as $40 in a cheap china balancing hobby charger, like the turnigy
if the PCB had in it a balancing charger itself , or full balancing curcuit stuff that you plug in power to, and it CHARGES balanced, then that would be good.
instead
the balancing Protections (from thier data sheet) just discharge the cells that are higher than the other ones , pretty lame way of doing it.
Without any actual knowledge , i suspect that the things would probably end up having more "parasitic" drain (teeny tiny discharges) than the normal protection. And that the acuracy of the balancing is not as good as charge balancing.
PLUS
with hobby charger balancing you can SEE things, you get loads of usefull info, like the final voltage of each cell, and the current, and have a good idea the batteries are working as they should. and Now you can get all that for as little as $40 in a cheap china balancing hobby charger, like the turnigy
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Yeah, the 5 leads with the hobby charger makes sense to me. I will most likely go that route. Now the question is the hardest one of all... which 18650's to use....cheap "trustfire, ultrafire, etc" or expensive "aw, sanyo, etc". Thanks for the help!!
VidPro
Flashlight Enthusiast
LG if you can find real LGs, and NOT LCs which is not an LG but might try to look like one 
sony, or sanyo, and mabey panasonic. 100% new and fresh, dont get some old Pulls that sombody is unloading for cheap.
the rest of that stuff, wont last good enough time.
because you dont need single cell protections on the cell, you can get most of those premium cells unprotected for about $7-9 each
sony, or sanyo, and mabey panasonic. 100% new and fresh, dont get some old Pulls that sombody is unloading for cheap.
the rest of that stuff, wont last good enough time.
because you dont need single cell protections on the cell, you can get most of those premium cells unprotected for about $7-9 each
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I'm looking at some LG 2600mAH batteries right now for about $8.00 a piece w/shipping. You're probably right about not wasting my time with cheap batteries. If I'm gonna put the effort into making a pack and sealing it up I would hate to end up tearing it open and replacing cheap cells so I guess I'll bite the bullet and get some good ones. Thanks for all the help again!
