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sparkysx

Linking lipos

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No you can't link to form a 3s.

Both the batteries you have are 2s, and linked together would make a 4s if series connected and 2s if parrallel conected.

 

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They aren't both 2s, as one of them is half of a saddle pack, it would only be a 2s with the other saddle pack attached.

 

The 2s is 5000/60-120

and the saddle pack half is 5000/30-60

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I've a similar quandary, but mine are the same C rating, but different Mah (2s is 4300 and the half saddle is 5300).

I'm presuming if you don't demand any more amps than the lowest C rating, then it shouldn't matter? 

Maybe raise the lipo cut off voltage in the esc to try and compensate for any difference between the cells? 

I wouldn't charge them together as a 3s though, that would be asking for trouble.

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well the discharge is exactly half of the 2s battery, so when the saddle packs are together the ratings of both batteries are exactly the same.

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Wouldn't that only be,if the saddle was linked in parallel, not serise? 

How I understood, 2S ("2"cells in "S"erise). The saddle is 3.7v, 5000mah and 30-60C discharge rate each.

2 saddle in Serise (normal way) = 7.4V , 5000mah 30-60C 

2 in Parallel = 3.7v, 10000mah 60-120C 

 

 

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well I would wire it in series, so that should equal 11.1v. I already tried it (briefly) and the wheels were spinning a lot faster.

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It would work in theory but I wouldn't trust the capacities to be matched (even though they have the same theoretical rating).  There's the problem, because if one cell goes under min voltage but the other 2 are still over, you wouldn't get a cut-off but the low cell would be dead.  Also, to be pedantic (but it is important) the one half saddle you have is actually a 3 cell pack (3P).  So you have even more chance of balance issues and you couldn't detect it or do anything about it if it happened.

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You need to be able to charge them as 1 battery to get them to balance properly, then you should be able to run them. If the capacities are the same or very close, then you need to wire them to together so you can balance them as 3s.

Assuming 1/2 a saddle is 1s, and not 2s, but half the capacity.

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I don't think anyone makes a 3S saddle battery.  If you had three identical "1S" saddle units you could use them in the 3S config.  In this case, if you want to be safe, I would probably charge each one separately as a 1S.  You could also install a separate low voltage alarm on each saddle unit in the car if you want to avoid messing with making up the 3S balance wiring.

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For the cost of a factory made 3 cell LiPo I wouldn't muck about with it. You'll save maybe £25 over buying a new 3S harcase lipo from HobbyKing, but that'll be cancelled out if the home made battery goes poof when you're using it or charging and there's a fire in your model / garage.............

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well only the wiring would be homemade, but I'm pretty good at that part tbh. I keep the lipos in an ammo box, but what could cause them to blow anyway?

 

 

cheers!

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9 hours ago, sparkysx said:

well only the wiring would be homemade, but I'm pretty good at that part tbh. I keep the lipos in an ammo box, but what could cause them to blow anyway?

 

 

cheers!

I was thinking about using cells with mis-matched C ratings, maybe trying to charge it all as one lump. LiPo have been known to go bang / swell just under normal use. The other thing to consider is the chance of damaging the cells in an accident / roll over when using the model. I don't know what you're putting them in, but I've scraped up battery packs when trying to custom fit (bodge) batteries into cars they're not designed for or part built cars. If money is not a problem then I would get a 3S Zippy LiPo hardcase pack from HobbyKing. I just think it's job done in a neat package, and erring on the side of safety.

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they would be going in an Ansmann X2C pro, and all three batteries would be exactly the same ie: 3 of the smaller batteries in the picture above.

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