1, 2 or 3p in lipo's. Which is better?

[crazyjr]

Having a chat with Coolhand and sjcrss about Lipo's and the question of cells in parallel came up. The question is: Is there an advantage in going with cells in parallel? or, Is it better to go with single cells for the P?

My thoughts are that if you can go with single on the P side, it makes the pack less complicated and possibly safer. Can a cell in P go out of balance with the other cells? or , Is it just in series?

Thanks for any input and look foreward to many pages of discussion:005: :007:

[BrianG]

I suppose if one cell in a "p" set goes bad, it would drag the other down as well. Or if one cell opens (internally disconnected) somehow, that single cell would be forced to supply the full current possibly exceeding its C rating.

Sometimes a single cell doesn't have enough of a discharge C rating to cope with high currents. Or it could simply be a physical size issue.

[MetalMan]

A "P" cell can not go out of balance. Like Brian said, a low "P" cell would drag the others with it.

Going with "P" cells might be for several reasons:
-cheaper to go with more cells than a single cell (cost decreases when quantity increases)
-increased capacity where no larger cells have a form factor that will work
-form factor of smaller cells is good, but capacity/discharge rate isn't enough

[crazyjr]

So the answer would be, if the cells can handle the discharge in single form, the single p would be the best.

[MetalMan]

It's hard to say. You'd have to compare several smaller cells in parallel to a single cell of the same chemical composition that has the same capacity of all of the parallel cells combined. My thoughts are that if you can go with a single "P" setup, it would run more efficiently.

[crazyjr]

What we were looking at was the single cell P 10,000mah 15c packs as oppose to the 2P 8,000mah 20c packs. The 10k's are 15c (150 constant) and the 8k's are 20c (160 constant). With similar output currents, Which would be better? Durability and efficiency wise.

[MetalMan]

I think the only to know is to do actual testing with the two packs, checking temp., capacity change, number of cycles before the pack goes to 80% capacity, check voltage under load as the cycle # increases, etc. The quality of the cells would have a rather large impact on this.

[crazyjr]

Ok, i understand. I got some of the 8k lipo's coming, maybe have to add the 10 k's to the collection and find out. Thanks guys, I knew you'd have a good answer to the question

[starscream]

This is an interesting question but I would think that any time you add an extra cell to the mix you'd be applying additional resistance so a 1P setup, with the same C rating, would be more efficient. In the case of the 8Ah 20C's and the 10Ah 15C's, I would think that the 20C cells would perform and be happier in slightly higher current setups and the 15C cells would give you longer runtimes in higher voltage applications. So, like usual, it doesn't seem very clear cut. What vehicle are you running and at what voltage?

[danverz]

I surely would go for a 1P setup.
More efficient at all.
And I am sorry but in my experience, the 1P stay a lot more balanced.
The only one thing is the price: to achieve the right C discharge you have to buy
big, great and expensive lipos.

Just my 2 cents,
Daniele

[coolhandcountry]

I was thinking what if the you have say a 4000 mah 2s1p pack rated at 20c.
You have 4000total 2s2p pack rated at 20c. Both have the same voltage.
Both have the same amp rating. Which is better?

[BrianG]

I'd say the 2s2p pack will probably have less resistance since you are doubling the contact area. But then again, you are doubling the solder joints.

And then the point about balancing is valid too.

Personally, I'd go with the pack that will fit in the space you have with the amp and Ah rating you need/want. If they are both the same size and ratings, go with the cheaper one. :027:

[crazyjr]

So the short answer might be, that the 15c would be better for hv apps., like 4 to 6s and the 20c would be better for hi amp setups, like 2s.

Starscream, we were having a theoretical discussion and vehicle did not enter the discussion, however if i had them, they would be used in my G2R with a mambamax esc and a bk wanderer 9XL, geared to about 30 mph (racer, not basher), I don't think i would hurt either one in my setup.

[sjcrss]

so let me see if im getting this correctly....2 - 2s2p's 8000's = 4s, and the
2 - 2s1p 10000's = 4s1p would be far more effecient than the 2s2p ...right

[starscream]

Originally Posted by crazyjr

So the short answer might be, that the 15c would be better for hv apps., like 4 to 6s and the 20c would be better for hi amp setups, like 2s.

Starscream, we were having a theoretical discussion and vehicle did not enter the discussion, however if i had them, they would be used in my G2R with a mambamax esc and a bk wanderer 9XL, geared to about 30 mph (racer, not basher), I don't think i would hurt either one in my setup.

I think either would be fine for your setup as well. It looks like the price of the 10Ah packs are less as well so it would make sense to go with them unless you have a vehicle that really needs the extra current.