Small packs or big packs.

[Simon.O.]

I hope I can descibe this one as I see it.
My bigger twin cat has a pair of outrunners 1600kv and 1500W capable, as of now I am sure that I do not use all of that avaiable power because after a 2 min wot run they are warm but not hot.
They are fed with 100 mystery type aircooled esc's that get warm but not hot so I am guessing I am in the 80A range.

I currently use 5S made up from 3S+2S 4500mAh 30C to give me 135A available.
IF I am up to about 80A with the power system (each side) then I think it is best to upgrade my packs even though they are warm but not hot or swelled after a good blast on the pond.

Here is where the question kicks in.
I can go with a single 5S pack that can provide 200A or go with two smaller packs at 100A each to give me a combined 200A feed.
I have chosen 200A total as I am happy to feed 100A to each esc. btw these are about to be swapped out for a pair of 150A units as the boats they were robbed from are begging to get wet again.

Now if I choose to go with a total of 200A and say 4500 mAh+ can I make this up from any type of combination, example.
5S 5000 mAh 40C single
5S 2500 mAh 40C 2P

I am concerned that the smaller packs, even though the numbers stack up, do not have the physical size to do the job.

What I need is 5S feed to two motors. 100A per side will be enough for this hull.
I want to run 6 to 8 passes (100m or 330' per pass) about 2 mins is plenty.

Now how to I configure my packs. ? Weight will become an issue above 800g or 28oz.

I said at the start that this may not be too clear.

[m4a1usr]

I said at the start that this may not be too clear.

Makes sense to me. Here is the bottom line on lipos and you know it as well as any of us. When adding capacity by increasing the number of packs, you add wire resistance due to design. So circuit resistance has increased. As well, all lipos suffer voltage depression as amperage or current gets used. Most lipos dont start seeing any major voltage drop until they get below 50-60% capacity. But the curve starts degrading faster in that last 10 or 20% available. So thats the "danger" zone to try and keep out of.

With packs that have a larger capacity the logic is the cells are matched (hopefully!). The cell to cell connections are about as short as you can get, so the ohms law numbers are at the minimum they can be. Bottom line, you will be in a more eff configuration using one pack over 2 unless pack location effects other aspects of your setup.

John

[ozzie-crawl]

why not just run 1 pack per side,5s 3000 etc
less wire

[Simon.O.]

I have now nailed down three options
2S+3S 5000mAh 40C 200A weighs in at 715g 25.2oz $74

2 x 5S 3300mAh 30C 99A each 920g 32.5oz $80
2 x 5S 3000mAh 40C 120A each 900g 31.8oz $90

The 2+3 option will fit in there easily and the 2x5 option will be a royal squeeze and some big weight.
I can see a possible benefit of the additional mAh, the coin cost is not an issue but the weight may be.
I am looking at 200g 7oz