So, I'm not sure how comparable different makes are, but running losi electrics with the 2100kv motor, if I go for 4200 4S cells they should definitely go for longer than 10 minutes yeah?

I'm hopoing to enter a few meetings where finals are 22 mins, I have one 5000mah 4s pack (the losi one which by all accounts is a bit s**t), would that and a 4200 4s see me through 22 mins easily enough?

what is the C rating of the 4200?
my 5000's that have about 4550 left in them can easily do 15 minutes flat out but it depends on gearing e.t.c

As electric says, it depends on the gearing and stuff, but, geared to the same speed as the nitros I get about 12 minutes with 4350mAh 4S so 10 minutes with 4200 should be easily acheivable. Also, as you are already an electric driver, you should be a bit smoother anyway, so you should be able to get more run time than me
(faithful nitro driver originally; throttle on "waaah - waaah - waaah" through the corners:lol: - not good for battery life)

It'd be 40C, the 5000 is 15c I think. Not an ideal balance having 2 such different cells, but on a 2100kv geared sensibly (to nitro pace) should they do 22 mins between them? And should the 4200mah ones manage a 10 min heat?

The capacities should both easily make 10 minutes each (probably about 11-12 minutes).
15C is unlikely to be powerful enough. (5*15 = 75A). Most people reckon that you need about 100A continuous. Also it does depend on the Burst current available. With my Flightpowers I have 50C burst (4.35*50 = 217.5A)

you will probably be better off running 20C's.
burst is only for a few seconds though and for most of the run you won't use very many amps at all. take a 5000mah pack for example if you get 10 minutes runtime out of it (quite short i know but if you really are tearing it around a track possible) you are only using 30A average over the run ;)

However, it's the bursts that kill the lower C packs off. My set-up has bursts of about 150A, which a 15C pack (which is probably only capable of 25-30C burst), even of high capacity, is unlikely to be able to provide, and so will probably puff.

It's ok, I put the wrong figure, it's 25c in reality!

Think for my first meeting I'll just not run the final, tbh I want to be able to make 25 mins on 2 packs of 4s, one of which is 5000mah, and not sure 4200mah in the other pack will give me enough will it? May need to get another 5000, will that give it enough?

I say give the final a shot, you don't know what sort of run time you are going to get until you've tried.

I would have thought that you could get 25 minutes between the two packs, I use 4S 4350 and get 11-12 minutes on a rough track, so probably more like 13-14 on a smooth one. 5000 is 115% of 4350, so you should (hopefully) expect 115% of the run time (12 * 1.15 = 13 minutes 48 seconds - perhaps a bit exact...) but 12 + 13 and a half is 25.5 so should be enough. Just don't do the warm up bit at the start, turn the car on and stick it on the line with 15 seconds to go.

Yeah actually from that they should last (especially considering time lost in pitstop too), what I mean't was I haven't actually bought the 4200 yet! I'm only planning one meeting before mid July, so might just do the first (in May) with just the one 5000 battery then not finish the final, and wait to see what comes available over the next mth or so battery wise, rather than getting a second one right now! Might leave me better set for the meetings I'm doing later in the summer!

Dave

Oh, I see. That's a pretty good idea to be honest. As for the 2nd battery, I would still go with non-hardcased 14.8V as the quality of the packs are generally better than the hardcased 4S packs.

I can get around 30 minutes or more from an 8000mah 3S battery, running a MMM 2200Kv combo on my Xray 808.

Iv got a Castle MMM/2650kv set up, and iv ordered some 22c 5000mah packs, but i really want to try it out! Iv got some newish trakpower 20c 3200mah packs from my b4. I know the C rating is a bit low but do u guys think they will be ok for a few short runs? Anyone had any experience of running them in 1/8th? Im dying to drive it but not at the expensive of puffing lipos :(

cheers,
Ben

I have 25C flight power cells and Max amps cells, 22C Tornado packs and a Flightpower 20C, and to be honest i cant notice the difference so i think you will be fine, especially over short runs, i managed to get 21 mins out of the Flightpower 5000mah on a loose dirt track, obviously if you are on something like grass or astro where you have the grip your run time will reduce a bit.

The Castle Creations Monster Mamba Max states in the instruction manual not to use anything less than 5000mah for a reason! I would not try it with your 3200mah packs as they will have too much current drained from them and are likely to puff up and become useless.

I've got to agreewith AmiSMB with this, 3.2A * 20C is only 64A continuous, which is not going to be enough. Running packs under 5000mAh is fine, but the C rating must make up for it, so you would need 30C packs at least for 3200mAh to be fine. Even then they will be quite pushed 3.2 * 30 = 96A which is about right but they will get quite warm and won't last as long (i.e. as many cycles) as a larger capacity pack that isn't as stretched.

Guys, if running 2x2s will 4mm connectors handle the load ok?

yea that should be fine :thumbsup:

also you should only use a pair of lipos if they have the same amount of use otheriwse you will puff one as i found out the hard way with some 2s lipos :thumbdown:

I've been trtng to ask about this in another thread, is it safe to charge the 2 batteries separately or do you need to try and do them as one?