Lipo Para wiring??

[Jeff Wohlt]

How many of you use smaller packs say 4S and 2600 - 20C (example) and para wire them to give you 5200 mah and 40C.

Seems like it would be cheaper and stronger?

Give me some input, please. Seems like a cheaper solution to more more power and cheap. Even 6S smaller packs are much cheaper.

[kookie_guy]

How many of you use smaller packs say 4S and 2600 - 20C (example) and para wire them to give you 5200 mah and 40C.

Seems like it would be cheaper and stronger?

Give me some input, please. Seems like a cheaper solution to more more power and cheap. Even 6S smaller packs are much cheaper.

Would you get 40C? I don't think the discharge rate doubles. Yes, you get double the capacity, but the individual cells can still only discharge at their limit, which would be 20C.

[Jeff Wohlt]

hmmm..not what I understand about C rating. But this is the reason for me asking.

[kookie_guy]

I could be wrong too. Any battery experts care to chime in?

[BondoBrushless]

Weither 2 packs are joined in series or parralle the C-rating stays the same.

Series is double volatge and same Mah

Parralle is double Mah and same voltage

In parralle the amp discharge does rise some due to mah capacity has risen, but not much at all with small packs.

[sailr]

Parallel doubles the mAh
Series doubles the Volts

NOTHING doubles the C rating

[m4a1usr]

NOTHING doubles the C rating

G-freak does! Hah,...gottcha there Jim

John

[sailr]

Well, G-freak seems to do a lot of things that are, uh.....

[chuff]

Parallel doubles the mAh
Series doubles the Volts

NOTHING doubles the C rating

I beg to differ... strictly your answer is correct, but may confuse some viewers.

The C rating of each pack does not change when wired in parallel (as you say, NOTHING can change the pack RATING), but the current draw out of each pack will halve.

A given motor/prop/hull combination will draw a certain current (amps) and power (watts). In a ?S1P setup ALL that current comes out of the 1P pack. That is, ALL the current passes through EVERY cell in the pack. However, in a ?S2P setup made of two ?S1P packs half that current comes out of EACH pack. Such ?S2P layouts therefore do two things: they double the mAhrs, and they HALVE the current draw or "stress" on each cell in the packs. Single ?S2P packs offer similar benefits.

Chris

[Fluid]

... strictly your answer is correct, but may confuse some viewers.

In reality with higher draw setups, paralleling packs does not halve the total draw. By reducing the internal resistance (going 2P) the packs can deliver a higher watt output; this is why you will see a speed increase in a hot setup when going from 1P to 2P.

But to return to the original post: a 4S1P/20C/2600 mAh pack has a "maximum" recommended discharge of 52 amps. A 4S2P/20C/2600 mAh pack has a "max" discharge of 104 amps.



.

[sailr]

So what are you 'differing' about!? Your explanation is also correct but a simple question was asked and a simple answer given. I chose not to explain how to build a watch when somebody asked what time it was!

I beg to differ... strictly your answer is correct, but may confuse some viewers.

The C rating of each pack does not change when wired in parallel (as you say, NOTHING can change the pack RATING), but the current draw out of each pack will halve.

A given motor/prop/hull combination will draw a certain current (amps) and power (watts). In a ?S1P setup ALL that current comes out of the 1P pack. That is, ALL the current passes through EVERY cell in the pack. However, in a ?S2P setup made of two ?S1P packs half that current comes out of EACH pack. Such ?S2P layouts therefore do two things: they double the mAhrs, and they HALVE the current draw or "stress" on each cell in the packs. Single ?S2P packs offer similar benefits.

Chris

[Jeff Wohlt]

Jay....bingo! That was the answer I was looking for. Amps being pulled. Maybe I did not state the question right. So I am right that I can use smaller packs and be able to pull more amps on 2P than 1P? Not that I will want to push them hard but 2P has the ability to let more juice flow if needed.

The reason is I would like to get a couple of 4S 2600 packs at 20 or 25c and be safe to pull 80 amps or so and still have a large "gas tank" if you will. These would be for my cats or smaller rigs.

[FighterCat57]

In reality with higher draw setups, paralleling packs does not halve the total draw. By reducing the internal resistance (going 2P) the packs can deliver a higher watt output; this is why you will see a speed increase in a hot setup when going from 1P to 2P.

But to return to the original post: a 4S1P/20C/2600 mAh pack has a "maximum" recommended discharge of 52 amps. A 4S2P/20C/2600 mAh pack has a "max" discharge of 104 amps.



.

So, it essentially doubles the available C Amps, but not the rating in type.

Perhaps a flaw in the rating setup? Or the opportunity for a new rating? Available C?

Or just a simple calculation we should extrapolate when we see the "2P"... we know to double the "C" for available amps...


I love coffee.

[FighterCat57]

Jay....bingo! That was the answer I was looking for. Amps being pulled. Maybe I did not state the question right. So I am right that I can use smaller packs and be able to pull more amps on 2P than 1P? Not that I will want to push them hard but 2P has the ability to let more juice flow if needed.

The reason is I would like to get a couple of 4S 2600 packs at 20 or 25c and be safe to pull 80 amps or so and still have a large "gas tank" if you will. These would be for my cats or smaller rigs.

Jeff, I've been doing this for some time with some tiny 20c packs in 2p and 4p to get the amps necessary for these big setups before I buy the big expensive packs. So far, it's been working out great. Some times cheaper going 4P, but rarely lighter.

[Jesse J]

Ya, my latest kick (mainly 'cause I'm a poor student still-and they were in stock) is the 3.6 aH Turnigy packs for $20-$30 a pop that are 30-40C and double, triple or even quadruple them up. I built me a 4P adapter out of 5.5mm bullets and have a great long and punchy ride. I spent $150 for a nice suite of identical batts (4x2S, 2x3S, 2x4S and 2x5S) then I can do many configurations in 2-4P.

[ED66677]

2x2600mAh 20C in parallel will give 2x(20x2.6)=104A that's it!

[Jeff Wohlt]

Jess....could you shoot a pic of the para bullet connector you made?

So I am wrong about C rating but it basically does the same thing in the fact it doubles amp output. I thought that was right.

[Jesse J]

here you go. Version one was not soldered... these are V2.

I took 8GA wire, attached the appropriate bullet connector, then inserted into the hole and clamped down (the guys on the right are what I used - don't know their names), then flooded the whole caboodle with flux then solder. Once it cooled, I plasti-dipped to ensure good insulation. I use shrink wrap on the unused plugs - here I was using it as 3P connector.

[FighterCat57]

I did something similar, only used the "solder blob" technique and some safety wire.

Basically stripped the ends of the wires and tied them together and soldered it up like a bundle of sticks. Taking turns, flipping it around making sure each wire get's good solder flow...

It's held up great so far. =) I had some photos of the soldering with the safety wire in a thread somewhere... I'll link to it if I can find it.

[chuff]

In reality with higher draw setups, paralleling packs does not halve the total draw. By reducing the internal resistance (going 2P) the packs can deliver a higher watt output; this is why you will see a speed increase in a hot setup when going from 1P to 2P.

But to return to the original post: a 4S1P/20C/2600 mAh pack has a "maximum" recommended discharge of 52 amps. A 4S2P/20C/2600 mAh pack has a "max" discharge of 104 amps.



.

Sorry, but I beg to differ slightly once again…. Fluid is quite correct , changing from a ?S1P setup to a ?S2P setup does reduce the internal resistance of the battery/wires/ESC/motor circuit and therefore the current draw will increase, but only comparatively slightly. For comparison, going from say 12 gauge wire to 8 or 6 gauge wire will deliver a similar reduction in internal resistance. Nevertheless, the current draw per cell has roughly halved (this is partly why the internal resistance of the circuit has reduced). This halving of the current per cell is a BIG change, and this is the main benefit (particularly from a battery pack life point-of-view). Remember that the ESC & motor still see ALL the increased current, so by going to ?S2P we will have slightly increased the stress on them. Hopefully the slight increase is not the final straw – If the ?S1P setup is already over-stressing the circuit, going to ?S2P will only make things worse….

We should also keep in mind what the C-rating of a cell really means. It is not the max current we can draw from the cell. Clearly with a short we can draw many hundreds of amps, even thousands. No, the C-rating is the current the Manufacturer believes it is safe to draw from the cell (assuming he is telling us the truth, which is another matter…) So far, I have been unable to find any Industry Standard applicable for determining the published C rating on our Lipos. (Someone may be able to advise). I can only presume it is a relationship between time, current, and resulting temperature rise.

In short, parallel set-ups offer significant benefits - either reduced stress on the cells or, on the other hand, giving us a safe way of increasing amp draw, but is is important to understand what we are doing .

and another thing ...
If you buy a single 4S2P/20 C/2600 pack, I would be a little cautious about pulling 40C (104 amps) out of it. If its made out of 20 C cells and this is what the printing on the pack means then OK, but if the manufacturer is being tricky and has made it out of 10 C cells, the pack is only safe to 20 C as he has warned you on the label.....???

[Jesse J]

Remember that the ESC & motor still see ALL the increased current, so by going to ?S2P we will have slightly increased the stress on them. Hopefully the slight increase is not the final straw – If the ?S1P setup is already over-stressing the circuit, going to ?S2P will only make things worse….

This doesn't make sense. If you run same voltage and increase your amp CAPACITY, you will still only draw what you need, right? BUT in the XS2P config, you are drawing less off each individ batt, and therefore the current bouncing around is more dissipated and therefore easier on all the electronics involved.

Correct me if I am wrong - I am not an electrical engineer nor a battery guru, just trying to hone my understanding of the inner workings of the power system.

[ED66677]

It does make sense Jesse J! if you double the capacity of a pack, you will certainly see a smaller voltage drop under load, this will result in a slightly higher voltage at ESC/motor, few tenth of volt may be... higher voltage, higher rpm higher amp draw!

[FighterCat57]

This is when I would leave the room in college and say you "EE" guys are weird and I would go design real systems while they were trying to calculate stuff.

Here's my xS2P harness:


PSA- 4 3s 20c 4k packs is enough to melt EC5 connectors feeding a Turnigy 180 ESC.

[chuff]

This doesn't make sense. If you run same voltage and increase your amp CAPACITY, you will still only draw what you need, right? BUT in the XS2P config, you are drawing less off each individ batt, and therefore the current bouncing around is more dissipated and therefore easier on all the electronics involved.

Correct me if I am wrong - I am not an electrical engineer nor a battery guru, just trying to hone my understanding of the inner workings of the power system.

Hi Jesse
Pleased to see people seeking understanding.

You are mostly right. In a 2P arrangement its only the cells that have an easier time. The full current (actually a little more) must go through the ESC and motor. The motor in particular must see all the current and as much as possible of the voltage - that's were all the useful work gets done. Everywhere else we just get useless heat.

Chris

[Jesse J]

It does make sense Jesse J! if you double the capacity of a pack, you will certainly see a smaller voltage drop under load, this will result in a slightly higher voltage at ESC/motor, few tenth of volt may be... higher voltage, higher rpm higher amp draw!

I see your point. thanks for the clarification.

In a 2P arrangement its only the cells that have an easier time. The full current (actually a little more) must go through the ESC and motor. The motor in particular must see all the current and as much as possible of the voltage - that's were all the useful work gets done. Everywhere else we just get useless heat.

That helps too.

Thanks guys

[tdonnellyem]

Hi Jesse
Pleased to see people seeking understanding.

You are mostly right. In a 2P arrangement its only the cells that have an easier time. The full current (actually a little more) must go through the ESC and motor. The motor in particular must see all the current and as much as possible of the voltage - that's were all the useful work gets done. Everywhere else we just get useless heat.

Chris

im new to the fe stuff so i make examples up to see how it works. say you have a 4s 4000mah 30c battery by itself. the draw would be 120a(30c x 4000/1000=120a). if you took a pair of 4s 2000 mah 30c batteries in parallel (4s2p) you still have the same amp draw (30c 2 2000/1000 x2[batteries]=120a. the difference to me is that you are getting the same draw out of 8 cells rather than 4 cells,thus easier on the cells themselves, and using a lower mah battery. so chris as it right on about a ?s2p setup being easier on a battery pack

[graill]

As folks have touched on here the esc and motor will get what they can in regards to request and available potential.

Your C rating will only release energy at a fixed rate up to its max, over that and fun things happen, that cant be changed until you simply buy a battery with a higher C rating, what you can change is the workload over several packs by paralleling.

One pack will work harder and degrade faster (and possibly burn up if your figuring is wrong) than three of the same pack paralleled in the same setup under the same load, though now your heavier, you decide what you want to do.

[H2OCamel]

Ah now this is cool stuff!! I like paralleling my A123's since I can recarge them quickly. I have first hand experiance with batteries being arc welders......just remember that lightning is 7 times hotter than the surface of the sun! I haven't had the time to check the tempature of a shorting battery!

Thanks for the info!