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Lipo advice please

10s vs 2 x 5s

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Phil B07/10/2019 14:53:50
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148 forum posts
147 photos

Does anyone have experience of using 10 cell Lipos?

I am setting up an electric conversion of a 50cc model the motor requires 10 cell Lipo at 100 amps. Am I best getting a single 10s battery or will 2 5s wired in series be the same? All are rated at 5000mah.

Dickw07/10/2019 15:07:13
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480 forum posts
76 photos

I use 10s packs regularly.

I buy 5s packs or 6s and 4s packs and solder them in series to make a 10 s pack. A 10 s pack is just 10 cells wired in series, so it doesn't really matter how you do that.

Where it does matter is in charging. If you want to charge a 10s pack you will need a 10s charger and there are relatively few on the market. If you use 2 x 5s packs plugged together, you can separate them and charge them on a more common 6s charger. I use 10s chargers.

Dick

Peter Jenkins07/10/2019 15:48:54
1279 forum posts
132 photos

Agree with Dickw. Also, if 1 cell in a 10S goes down the whole pack is scrap. With 2 x 5S, in the same situation, you have one good 5S pack left. The biggest issue is charging a 10S as Dickw has mentioned. I use parallel charging for my 2 x 5S packs. You will need to solder up sort of Y lead to connect the 2 5S packs in parallel and use a charger than can charge 5S at 10 amps as the charger sees a 10 Ah 5S pack. If your existing 5S charger can do that you are good to go. I use 2 chargers each having 2 outputs able to charge at more than 10 A each so in 2 hours I can charge 6 flight packs and 3 Rx packs.

I use the Hobby King 4 mm shielded bullets as they add to safety by not exposing any bare bullets. Also 4 mm bullets are good for up to 100 amps and my setup has never exceeded 80 amps in the air. Different when tethered on the ground! The other advantage of these shielded bullets is that they are polarised and, therefore difficult to cross connect by accident! Yes, did thst with 5.5 mm bullets once and the result was little short of disastrous!

Hope that helps your decision making process.

Peter

Phil B07/10/2019 16:22:20
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148 forum posts
147 photos

Thanks to both for helpful advice. I have one 5s pack. Presumably to make a 10s setup I need 2 identical 5s packs?

Peter Jenkins07/10/2019 17:20:42
1279 forum posts
132 photos

I have always bought pairs of 5S cells. However, that doesn't guarantee that they will have been assembled from matched cells but you should be looking for packs with voltage difference between the cells in the pack of 5 mV or less and ideally internal resistance of 1-2 m ohms per cell - the lower the better.

I only charge to 95% capacity - it's a lot faster than 10p% - and try not to drop below 3.75 v/cell 18.75 v/half pack or 37.5 v/full pack. On a typical LiPo checker this shows as 14% remaining. I fly competition aerobatics so trying not to go below 30% is a non starter as you would not get through the schedule. I have several packs that have reached 90 cycles and are still going strong. These are all Zippy Flightmax or Zippy Compacts. You may have seen in the latest BMFA News, in the F3A Aerobatics section, that our No 1 pilot has just exceeded 300 cycles and is still doing a good job. I think those are Optipower packs so roughly twice as expensive but worth considering if you have good throttle control technique!

Peter

Allan Bennett07/10/2019 21:05:37
1555 forum posts
39 photos
Posted by Phil B on 07/10/2019 16:22:20:

Thanks to both for helpful advice. I have one 5s pack. Presumably to make a 10s setup I need 2 identical 5s packs?

The packs don't have to be identical, but they need to be similar. Since they're in series, the total motor amps will be passing through both of them, so they both need to be specced to handle that amps.

Apart from the advantages of two packs mentioned above, since you've already got a 5S pack it's likely that it's a size you're using for one or more model already, so it's good to standardise. I use 6S packs singly in one heli, in parallel (for double the mAh and amps capability) in another, and in series for 12S in a fixed-wing model.

Tim Hooper07/10/2019 21:25:17
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2863 forum posts
2363 photos

I have a couple of 10 cell models, and use 2x5S packs in them.

Besides being able to use 'standard' chargers, I can also use the individual 5S packs in other, smaller models.

Tim

Phil Green08/10/2019 19:06:51
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1530 forum posts
309 photos

My ebike is 10S, two 5S 5000mAh HK Blues. Charge in parallel, run in series.

img_20170314_105814.jpg

Tom Sharp 208/10/2019 20:49:15
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3545 forum posts
18 photos

Could I use two 4s packs plus one 2s pack to make ten. Identical specs of course.

Allan Bennett08/10/2019 20:57:49
1555 forum posts
39 photos

Yes, it doesn't matter how many packs you put in series, they will result in a pack which is the sum of all the cell-counts voltage-wise, and the capacity of the smallest pack mAh-wise. As you say, identical spec. (capacity, C rating, and condition) is the best. Only practical problem is the extra wiring and plugs.

Peter Jenkins08/10/2019 20:57:59
1279 forum posts
132 photos

Yes, you can do that but you need to consider how you are going to charge them. 2 x 4S in parallel and the 2S on its own.

john davidson 108/10/2019 21:05:28
19 forum posts

, when making up a lead to connect two 5s packs in series or any other plug soldering,be very carefull to check polarity, it is possible to fry the receiver and all the servos in a twinke of an eye,

Peter Jenkins08/10/2019 21:11:43
1279 forum posts
132 photos

I would not recommend using a 10S pack to power the radio system. Better to use a separate power supply dedicated to running the Rx and servos.

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