dumb question

[hammertime]

if im running a 7xl and a hex 120 esc on my catamaran 29" and i start with a x438 how do you know how the batteries will hold up......... i dont understand the first thing about batteries really...... i know if you pull too many amps they will fry...... if im pulling somewhere around 80-90 will i have to build my batts a sertain way to handle that kind of load......thanx guys

[hammertime]

ps i dont know if i will be pulling 80-90 it was just an example it maybe more.....i havnt tried it yet

[Steven Vaccaro]

Just like anything the better you build them, the more reliable they will be.

At 50 or so amps Nimh will be ok. At 90amps, consider lipo packs.

[hammertime]

so would this setup im going to try be too hott

[saleens7]

it depends how many amps you pull....even if the max load amps of a 7XL is 95 amps, it doesent mean you will pull that many...you could pull just 40-50amp, or even less, i dont know if thats how much you do pull though...

[Fluid]

It isn't the amps you draw from a cell that damage it, it is the temperature that results from high amp draw. You can safely draw 300 amps from 4200 cells without damage - done it - if you only do it for a few seconds at a time.

The way to tell if your cells are safe is to run the boat for one minute, bring it in and check the cell temperature. Keep checking every minute. You do not want to bring in cells that are over 145 degrees or you risk permanent cell damage. You will find that either you are limited by the amp draw (and thus speed) or by runtime. FE is all about balance....

BTW there is no "max draw" from a certain motor, it depends on the battery and on the load. You can pull huge amps from about any BL motor.

.

[adreher]

So is that how you guys test amp draw, just by checking the temps?

[saleens7]

would you pull more amps from more cells or less?

[Jeepers]

adding more cells on the same setup will pull more amps.

[Jeepers]

So is that how you guys test amp draw, just by checking the temps?

No, to test amp draw correctly you need a meter. in the absence of such tool, temperature can be very useful. most racers try to keep there temps well under 150.

[saleens7]

i know people use the 8XL in their supervees, what is the average amp draw they pull on thiers with 12 cells?...since ill be using 2 motors and usually a singe 8XL on 12 cells would push the villain fast, two of them should push it no problem, so i probably wont pull too many amps...

[hammertime]

how many amps do you guys think i will pull with the 7xl in my cat on 12 cells with a x438