Moogumby

iTrader: (32)

Just to provide some background, Im racing 21.5 spec racing and considering some 130c batteries, I found some that are 5 mm and some that are 4mm .. what kind of effect would it have in 21.5 racing? No FDR limit or locked timing or anything yet. I dont think the firehose effect even matters in this case due to it being 21.5. Any one have any ideas?

Roelof

5mm can handle more current but running 21.5 turns there is no fear to loose voltage with 4mm.

billdelong

iTrader: (33)

5mm will offer less resistance than 4mm however it will be almost insignificant, just pick the connector which is more convenient for you. If you're just getting started and are way off pace with fast guys, then nothing wrong with buying budget batteries that come with 4mm bullets. If you get to a point where you are closing in on position and need just a pinch more punch in order to be competitive, then invest in a high quality pack that comes with 5mm bullets, but there is so much more you can do to improve performance. The pack needs to support up to 8C charge rates so you can charge it at 40A, of course you'll need a charger that can charge at 40A plus a 40A discharger to cycle your LiPo just before the race. This will give your pack the lowest possible resistance (called IR) where a quality charger will give you IR readings to where a proper "IR boost" should get you close to 0.5mΩ ... a quality pack with no boosting will be around 1-2mΩ and a budget pack might be around 3-5mΩ.... the lower the IR, the longer your pack will hold voltage/punch during a race... you won't see this benefit until the last couple of minutes of the race where cars with non boosted budget packs will taper off and the high end boosted packs will still have the same speeds as if they have a fresh charge throughout the entire race.

papagogo

Not sure there is a big difference between 4 and 5mm
....

AHR43

Hey Moogumby,
What are the other guys in the 21.5 Spec Class running for connectors? 4 or 5mm? Might be worth considering compatible connector size if you have to borrow a pack to finish an event.
AC

NewbieRacer01

iTrader: (1)

Late reply, but couldn't op just use 4mm & 5mm type connectors? Then he can plug into either.

NewbieRacer01

iTrader: (1)

Nvm, i misread, op is asking about the difference between the two.

gigaplex

iTrader: (2)

They don't always work, they stick out quite high when plugged into a 4mm pack which can interfere with the top deck on many chassis.

glennhl

iTrader: (16)

No need for 5mm bullets EXCEPT that is all you can get with new batteries, so you are forced to go to 5mm.

Losiracer12

iTrader: (1)

Typically better quality batteries are now 5mm and cheaper oem packs are 4mm