Running 6S: 2 x 3S in series OR 2 x lower mAh 6S in parallel?

[IRON-PAWW]

Hey All,

Was hoping someone with much more knowledge than me could assist with this question.

I'm looking at batts for my 36in TFL Ariane 2. Currently has a TP Pro Comp 1690kv motor and a Swordfish 240 in it. S & B M445 at the moment. So I'm running 2 x 3S 5800mAh Entropy Batts (so called 50 -100c) at the moment, which are placed either side of the motor. Now - the batts are getting a shade hot for my liking (no measurements sorry, just going by feel) and I'm getting jack all run time - maybe 3 - 4 mins at most. The boat does need dialing in a bit more as it was running too wet on the last few runs - so that's a factor too, but still.

So I could either go 2 x higher MaH 3S batts or 2 x 6S batts in parallel to get more run time and perhaps cope better with the current draw? to keep the weight down I had the thought I could go lower mAh 6S batts - say 4500 or so.

What is the best way to go on this?

[stu22]

Time to get some numbers, specifically the capacity and C-rating of the various combinations you are thinking of, and start crunching them.

Off the top of my head, I would guess that if you keep the total capacity (mAh) and physical size of the batteries close I don't think there will be much of a difference. The larger individual cells of the 2 3S will probably have a higher C-rating than the smaller ones in a 6S pack but you would be running the 2 6S in parallel so I can see that making up the difference (and possibly be higher.)

Depending on the packs you pick I can see things go either way.

[Chilli]

Go 6S2P. Your packs will be happier and your ESC will be happier (less ripple current). Don't worry about the weight too much. It will help keep you on the water at higher speeds. Do work on your set up however. You'll increase speed while lowering amp draw.

[IRON-PAWW]

First off, thanks guys for your advice

So let me see if I have things right. If you have 2x5800mAh 3S batts in series - that will give you 5800mAh worth of 6S. Then if I did 2x5800mAh 3S in parallel - I'd have 11,600mAh worth of 3S. Is that right?

Series adds the voltage, parallel adds the mAh.

Now I'm hazy on this. If I go series vs parallel - how does that affect the amps I have on tap to draw.

If I went 2 x 3s I was thinking it'd have to be 2 x 7000mAh+ batts.

If I went parallel - was thinking 2 x 4000 - 5000mAh would be enough for ok run times.

[785boats]

Your first two statements are correct.
And because of that, if you still want 6s voltage at the motor, & I'm sure you do, you will have to run two 6s packs in parallel. Not two 3s packs. As Chilli stated in his post. 6s2p.

The current draw will be approximately the same. But it will be shared by two batteries. Half from each, & with less voltage depression under load. That's why it is easier on the batteries. And therefore the ESC.

Two x 5000mah 6s packs are a good way to go.

Bear in mind that if you ever do want to race this boat in Australia, we are not allowed to run parallel packs. Depressing I know. But dems da rules.