# 1s2p? 2s1p? ??



## fightnut (Jul 5, 2007)

Can anyone provide a link to somewhere that explains battery pack configurations, like 1S2P, 2S1P, etc, etc.?

Preferably something in simple terms (not overly technical, lol!).

I'm looking at these holders on ebay, and I don't fully understand what the differences are.


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## emu26 (Jun 23, 2008)

fightnut, it might be easier if you give an indication as to what voltage from the pack you are looking for then someone can explain it in specific terms for your needs.

I'm going to do something I don't normally do because I usually get this around the wrong way but I'm pretty sure when batteries are wired in parallel you add their capacity but the overall voltage stays the same and when you wire them in series the capacity stays the same but the voltage tallies up.

So, if you had two 3.7v cells at 2000mAh capacity each and you wired them in parallel you get a 3.7v battery with a capacity of 4000mAh. If you wire them in series you get a 7.4v cell at 2000mAh capacity. If you had 4 of them and wired them 2s2p it would end up 7.4v 4000mah.

Someone please correct me if I have done the usual and got these arse about.

As for how to wire them so you get series or parallel, I'll leave that to someone else to draw up.

Have you had a look at batteryuniversity.com ? It is usually a great source of info for all things battery related.


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## fightnut (Jul 5, 2007)

I just wanted to use the 18650 batteries I already have around (used in various torches) in one of these holders and wire it up to a Magicshine plug to use it with my Magicshine for shorter rides.

But then I just found these, which are cheaper (and they don't even mention any of the 1S2P, 2S1P stuff). What's the difference?


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## mfj197 (Jan 28, 2011)

emu26 said:


> I'm going to do something I don't normally do because I usually get this around the wrong way but I'm pretty sure when batteries are wired in parallel you add their capacity but the overall voltage stays the same and when you wire them in series the capacity stays the same but the voltage tallies up.


Absolutely spot on. A 1S pack is nominally 3.7V, a 2S pack 7.4V, a 3S pack 11.1V etc.

The first holder you linked to (2S1P) would indeed give you the same voltage as your Magicshine pack, which is 2S2P. So you would be able to use it with your Magicshine no problems (although with reduced runtime as you're only using 2 cells rather than 4). The second holder doesn't say whether the cells are wired in series or parallel, so if you bought it you would have no way of knowing whether you'd end up with a 7.4V pack (if they are wired in series) or a 3.7V pack which wouldn't power your light. It looks like the batteries are wired in series, but you wouldn't be absolutely sure until you received it.


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## Ofroad'bent (Jul 10, 2010)

fightnut said:


> Can anyone provide a link to somewhere that explains battery pack configurations, like 1S2P, 2S1P, etc, etc.?
> 
> Preferably something in simple terms (not overly technical, lol!).
> 
> I'm looking at these holders on ebay, and I don't fully understand what the differences are.


FMABattery on eBay can make you whatever holder you want. I've had good experiences with them.

For Magicshine you need 2S, for 7.4v. They can sell you a 2S1P (2 cells, 7.4v) or a 2S2P (4 cells, 7.4v.) or more.

You can also get 1S2P- (2 cells, 3.7v) and probably 1S4P, for different lights using L-flex.

FMA also sells complete battery packs in whatever configuration you want, and uses Sanyo cells. The female connectors that come with the battery pack can fit a Magicshine male, especially if you use some heat-shrink tubing to make it seal to the Magicshine male. The wires on these are a bit heavier duty than the holders he sells.


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## BlueMoon100 (Jan 30, 2009)

What about charging let's say a 2P pack - (2) 18650's in parallel 3.7v @ 4800 mah. 

Using the iMax B6 - would I simply use the lipo setting at 3.7v but change the capacity to 4800mah? For some reason, the charger doesn't recognize or distinguish the two cells.


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## mfj197 (Jan 28, 2011)

BlueMoon100 said:


> What about charging let's say a 2P pack - (2) 18650's in parallel 3.7v @ 4800 mah.
> 
> Using the iMax B6 - would I simply use the lipo setting at 3.7v but change the capacity to 4800mah? For some reason, the charger doesn't recognize or distinguish the two cells.


The cells are effectively forming a 3.7V 4800 mAh pack so you would charge it as such, with a 3.7V setting on the charger. However don't get confused between capacity and charge current - you can't charge "@ 4800 mah". 4800mAh is the capacity - the cell could theoretically produce a current of 4800 milliamps (mA) continuous for one hour (h). Charging your two-cell 3.7V 4,800 mAh pack should probably be done at 4.8 amps (4,800mA) or preferably less - I'd probably go for 2.4 amps to be on the safe side.


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## BlueMoon100 (Jan 30, 2009)

mfj197 said:


> The cells are effectively forming a 3.7V 4800 mAh pack so you would charge it as such, with a 3.7V setting on the charger. However don't get confused between capacity and charge current - you can't charge "@ 4800 mah". 4800mAh is the capacity - the cell could theoretically produce a current of 4800 milliamps (mA) continuous for one hour (h). Charging your two-cell 3.7V 4,800 mAh pack should probably be done at 4.8 amps (4,800mA) or preferably less - I'd probably go for 2.4 amps to be on the safe side.


If I charge at 2.4 - will both batteries charge to 2.4 or is that 'overall' and I would only get 1.2 out of each cell.

I know these are really elementary questions - this is my first run with lions.


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## Ofroad'bent (Jul 10, 2010)

BlueMoon100 said:


> If I charge at 2.4 - will both batteries charge to 2.4 or is that 'overall' and I would only get 1.2 out of each cell.
> 
> I know these are really elementary questions - this is my first run with lions.


2.4 is just the rate of charge, not the total charge capacity. You could charge them at 1A and get the same capacity, it'll just take longer.

I charge mine at 2A or so with a Turnigy charger on LiPo 3.7v (1S) setting.


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## essenmeinstuff (Sep 4, 2007)

fightnut said:


> Can anyone provide a link to somewhere that explains battery pack configurations, like 1S2P, 2S1P, etc, etc.?
> 
> Preferably something in simple terms (not overly technical, lol!).
> 
> I'm looking at these holders on ebay, and I don't fully understand what the differences are.


Just going to throw this in here.

1S2P means 1 cell in *S*eries (ie single cell), with two of those in *P*arallel. ie the voltage of a single cell with the capacity of two.

2S2P means 2 cells in series, with two of those sets of cells in parallel, ie double the voltage of a single cell, and 4 times the capacity of a single cell. 4 cells total.

4S1P would be a single "string" of 4 cells in series.

To connect two cells in series, connect the +ve of one cell to the -ve of the other, and the remaining +ve and -ve terminals form the new "battery" with double the voltage.

Parallel connection is + to + and - to -, which then also forms the terminals of the new battery (same voltage double capacity).


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## BritOnTour (Feb 17, 2011)

BlueMoon100 said:


> What about charging let's say a 2P pack - (2) 18650's in parallel 3.7v @ 4800 mah.
> 
> Using the iMax B6 - would I simply use the lipo setting at 3.7v but change the capacity to 4800mah? For some reason, the charger doesn't recognize or distinguish the two cells.


cells in parallel are seen by the charger as one larger capacity cell. So, yes, set the charger to 3.7V LiPo, set the capacity to equal to sum of the paralleled cells and set the charge rate to the recommended rate times the number of parallel cells.

Parallel cells naturally balance their voltage and charge/discharge current throughout their working life. However, if you you accidentally over charge/discharge the pack, you will most likely end up damaging all of the parallel cells.

When you have cells in series, it is recommended to balance charge the cells to extend their working life, but it is not absolutely necessary. Remote Control battery packs that endure very high discharge rates (can be 10-100Amps in certain cases!) always have balance taps built in and should be used. For lower discharge rates typical with LED lighting (1-5A usually) the series cells should stay relatively in balance and the taps are not always fitted.

If the series cells get out of balance, the potential problem is that the stronger cell will reach the 4.2V max cell voltage sooner, but the total pack voltage (8.4V for 2S) may not be reached due to the weaker cell being less than 4.2V. Without balance taps, the charger can only work on the pack voltage and may therefore overcharge the stronger cell to achieve the total pack voltage. Every one knows that LiPo cells do not like being over charged and tend to express this dislike by exploding or catching on fire!!

ALWAYS: charge LiPo packs in a fire safe location (garage floor, concrete patio etc), under continuous supervision!


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## fightnut (Jul 5, 2007)

Okay, I'm sorta getting it, although I'm still a little unclear. If anyone has a link to something with diagrams, that might help me wrap my head around it even better.



essenmeinstuff said:


> Just going to throw this in here.
> 
> 1S2P means 1 cell in *S*eries (ie single cell), with two of those in *P*arallel. ie the voltage of a single cell with the capacity of two.
> 
> ...


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## emu26 (Jun 23, 2008)

fightnut said:


> Okay, I'm sorta getting it, although I'm still a little unclear. If anyone has a link to something with diagrams, that might help me wrap my head around it even better.


does this help?


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## manokaiser (Jun 30, 2008)

> I'm looking at these holders on ebay, and I don't fully understand what the differences are.


These are obviously 2s1p holders: "Model:18650-2S1P-7.4V"



> But then I just found these, which are cheaper (and they don't even mention any of the 1S2P, 2S1P stuff). What's the difference?


These are also 2s1p, as can be seen.


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## BlueMoon100 (Jan 30, 2009)

Check these holders out. You can make your own configuration. These obviously don't have any built in circuitry protection PCB's. Buy the TrustFire Li's with the individual protection and you are golden.

Battery Holders, Clips, Contacts | Digi-Key


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## find_bruce (May 8, 2011)

I found this website was helpful in figuring out the difference between battery configurations.


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## Ofroad'bent (Jul 10, 2010)

fightnut said:


> I just wanted to use the 18650 batteries I already have around (used in various torches) in one of these holders and wire it up to a Magicshine plug to use it with my Magicshine for shorter rides.
> 
> But then I just found these, which are cheaper (and they don't even mention any of the 1S2P, 2S1P stuff). What's the difference?


The second holder is also 2S1P ie 7.4v, but unprotected, and with much smaller gauge wires which could be a problem.

I'm not sure if you can upgrade the wires- these look like they have crimped connectors, not soldered ones.


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## fightnut (Jul 5, 2007)

@Bluemoon, those look like they need to be wired up, being as I've never done that, not sure how easy or difficult it is (?). I imagine it can't be too hard.

@Bruce, thanks, that's what I was looking for!


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