nick 30

i want to use my 2x3s, 3800mah, 20C batts in my 29" mono

180a esc
feigao 8XL motor
38mm - 42mm prop

discharge rate = 46a
constant discharge rate = 61a
runtime = 5 minutes


please help

cheers
nick

guver

My Feedback: (325)

If you put them in parallel:

They'll be 3s x 7600 mah pack with 20C

The discharge rate will determine the time regardless of application and the batery may or may not be up to the task.

10C is 6 minutes
20C is 3 minutes

Doing the math on your parallel pack is 20 x 7600 = 152 amps

guver

My Feedback: (325)

If the rates you listed are actual measured rates and the packs are in series then pulling 46 amps from the pack will theoretically give you 5 minutes if pack is depleted. I'm not sure where you got the 61 amps from.

nick 30

the motor can pull a max of 83a and i'm wondering what amps the batt's will give

i run my 25" mono on 3s in parallel, do you think 3s in parallel in 29" mono will be upto it, just wanted peoples opinions before i wreck eveything, i may just go with 4s instead, i know my batts can take that, thankyou for the replies

guver

My Feedback: (325)

If we trusted the ratings on the pack then a pair of them in parallel would do the trick. Many times I have to cut the rating in half and without knowing the specific pack we don't know how it performs. My guess is that it will die quickly if 83 amps (over 10C) are pulled on this parallel set-up.

Using 4S without propping down will make it even worse. Here's a couple of ideas since I know very little about boats. If you had 4 packs then try them in parallel. Will you peg 83 amps only during acceleration or is it possible to use 83 amps all the time? It will make a big difference.

nick 30

4s in my 32" cat with a 42mm prop works better than a prop size below or above, all i ahve to do is a 1 minute run with different props to see which is best

83a is the max my motor can take before it gets destroyed, i think the simple answer is to try both 3s and 4s and see what comes out better

NobodyFamous

1 3s 3800mah 20c pack will deliver 76 amps continuously. (if rated properly as was stated)

nick 30

ok nobody famous

simple questions -

will it work on 6s with 40mm prop ???
will i fry everything ???
series or parallel ???

2084kv x 11.1v = 23k rpm's (crap)
2084kv x 22.2v = 46k rpm's (better)

2084kv x 14.8v = 30k rpm's

brodjack

The 29" when i had it ran on 3S with a CC60 air Esc converted to water cooling,with a Mega 22/20/2 which is a 2875kv motor.Speed was good,sensible but obviously not ballistic.
Runtimes were about 7 mins. on a 6000 mah lipo.
Everything came back reasonable temps,that CC60 is still running today in another hull i built for and sold to my brother,same motor and lipos.

Your motor on 3S is a bit lowkv and too much on 6S i'm afraid Nick

nick 30

cheers brod, 4s or 5s it is then mate, i'll order a 5s but use 4s for now, its almost done now, just need to add plumbing

nick 30

can i put a 3s, 5000mah, 35c and 2s, 5000mah, 35c together in series to make a 5s pack ?????

brodjack

Yes,providing the packs are of similar age and usage.What charger do you have Nick?
It might be simpler though to just get a 540 6XL 2,871 RPM motor and run both 3S packs in parrallel.

nick 30

thats not a bad idea, new motor, i'll check with astec and see if he has a 6XL

i have a Imax B6 charger, with charge, balance etc on it, i can hook it upto a 12v car batt and use that for charging, i have it hooked up to the mains here

astec don't have any at the moment, what would be a cheap equivalent motor ???

brodjack

Just been looking for some similar cheap motors,mostly the KV that you are looking for seem out of stock,must be a popular size.
Nearest cheapo i found is this Blackmantis,touch high kV for 3S but very cheap.
http://www.giantcod.co.uk/black-mant...-p-403774.html
List your sizes of lipo packs you have Nick,might be able to help a bit more.

nick 30

the only spare ones i have (the rest are dedicated to all the boats) are 2x 2s, 2800mah, 30c and 2x 3s, 2200mah, 30c batts, shame there not all the same, i could have used all 4 in parallel for longer runtime 

was looking at giantcod aswell, i want around 2200kv for 35k rpm's, the 8XL's fine and i'll run it on 4s, i'm going to stick with what i have for now and think about upgrade's later

brodjack

Have you got a 8XL?

nick 30

yeah, i have them in my cat and the mono you sent me, i run 4s in the 32" cat, so 4s in a 29" mono should be good

brodjack

Sounds good,4s would be ideal for the 29" hull.
I just remembered i have a Feigao 540 XL 7 doin' nowt,just needs new bearings,do you want it Nick?

nick 30

how much for it mate ??? i got loads of bearings, BOCA one's

brodjack

Like i said,doin' nowt.We run mainly petrol now so it might as well get some use.
If you want it i'll try and post it over tomorrow.Dont want owt for it.

nick 30

ok mate, done, thankyou, i can give it a good home in one of my boats, do you need my address again

brodjack

yes pm if you will.It has 4mm bullets which i'll leave on.
It would probaly be very good on 3S,nice gentle amps

nick 30

cool, i'll stick 5mm bullets on it as that what i use

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