ORIGINAL: hendrix
You mean the ECU right?
If it is about the ECU pack then a ~3000 mah 2 cell lipo or a 6 cell pack NiMh high amperage pack of about 3000 mah
will do the job just fine.
I always prefer the 2 cell lipo but if you have balancing problems then a NiMh pack (i always prefer the GP brand which i think
are the best cells) is good.
My personal opinion is that if you can use a light pack (due to CG problems) then even a 2100 20C 2S1P lipo pack will work just fine
and it will last for at least 2 flights with capacity left.
Usually the pump needs 2,5 ~ 3 A and the starter will use about 15A max but this is needed only at startup.
Many use a 7 cell pack but i don't agree as this will wear down the pump and starter motor very quickly.
Chris
Hey Ted,
I'm currently using a 6 cell 7.2v NiMh 4600mah pack for my JJ1800 test bed and I couldn't be happier, the thing lasts for ages and will run my 1800 for 20 mins with no probs at all, on average my pump is pulling 1.1-1.8 amps during normal running from idle and mid range rpms, and up to ~2.6amps @ max rpm (115,000rpm), I don't know what amps the starter is pulling as I haven't checked as yet. I can do this twice before I really need to recharge, so I'm getting the best part of 40mins out of it, I haven't run it untill I get rpm degradation from dropping voltage as yet so it may well run for longer...... I'm impressed.
Chris,
I don't see that using a 7 cell would be a major problem as the ECU will limit the current and/or voltage going to the pump to obtain the required engine rpm etc...likewise with the starter, the ECU will only run the starter up to the rpms set in the parameters, I have run my engines with a 7 cell 8.4volt 1800mah NiCd pack with no ill effects at all. However, as usual, I stand corrected and will accept thoughts and ideas from those more learned than myself!
Cheers,
Smithy.