Amp draw?

[Gazzalene 171]

Been looking for cells to fit a XV-01 and got help as usual from the guys here. I did a search on the cells suggested for availability etc. I wont go into the brand BUT the reviews were very mixed. From many charges with no performance drop to puffed after few uses. This was from car users and aircraft, admittedly not the same voltage and capacity BUT same brand. The guys on the AC side were saying that these are great cells BUT need to be treated correct with current draw. To much and they puff very easy.

I am new to the black magic of electrics ,so working the draw is beyond me. Now I realise motor turns and pinion size will effect this a lot but when talking say 12-15t brushed motor and 15t pinions what sort of draw would be going on?

 

[LongRat 616]

Welcome to the world of BS battery specification and labelling!

What you will find is that you will struggle to buy a battery that isn't capable of your needs (lets say, a 12T motor, 2 cell 7.4V in the XV-01), according to label specs.  With that motor you would expect easily 20 minutes worst case runtime on a 6000 mAh pack.  Which equates to an average current draw of 18 amps.  Or, an average of 3C (3 x 6000 mA = 18000 mA).  There are no batteries on the market with a C rating that low.  If it was only a small 3000mAh pack, the same current draw would be a 6C discharge rate - still lower than basically anything being sold.  So on that basis, pretty much anything should work.  The 'burst' or spike rating has no real definition from most battery resellers and certainly no consistency across the RC marketplace, but is probably more important with car use, as these spikes can be big.  Like over 100A, but for fractions of a second only.  Which batteries are better able to handle that is impossible to gauge from labels and only slightly more clear from personal testimonies.

My advice?  Buy a battery of the right size for your car (a major factor for XV-01) with the right number of cells.  Don't worry too much about the junk written on the label.

[Gazzalene 171]

Thanks for the info,did not realise how low the draw was. I think the AC guys had more complaints but I suppose that's due to the higher draw rates some AC might make?

[LongRat 616]

Aircraft can pull higher currents for a greater proportion of the time but don't tend to see such high spikes, as a general rule. Plenty of high performance aircraft run for sub 5 minutes, not the case with cars nowadays.