11.1v lipos for 1/8 buggy

[Niall Cromie]

Hi, I need some good advise, I am in the middle of converting my Eight 2.0 to lipo. I do not wish to add unwanted battery weight ie 14.8v lipos with crazy output which will defininately stress diffs etc and hope to keep the weight very similiar to my original car ie 3.0kgs. My intention is to go with the Mtronics beast combo 2000kv motor and 11.1v flightmax lipos 3s 5800mah 40c cells. Before i order these pieces can someone please help guide me especially with run times and power output by the way we have a tight supercross style grass track with lots of height changes!

Thanks N

[kennyrc]

Usefull tool in link below.

http://scriptasylum.com/rc_speed/_top_speed.html

As a rule its better to use a higher voltage battery with low capacity, than low voltage battery with high capacity. Higher voltage is cheaper, lighter & puts less strain on the electronics. Doing some simple maths you can work out what battery size you will need for the race duration you are running the car.

I use a small capacity pack for qualifying & a large pack for the finals.

My car will just do 20 mins using 2200KV motor, 4S 5000mAh battery. The power of the battery is (P=V*I) 74W, 3.7W per minute of run time.

Hope that helps, a bit.

[Niall Cromie]

Thanks for the advise, can I ask what cells you are running? also no one has mentioned the weight saving in using 11.1v lipos vrs the 14.8s is there an advantage in using lighter cells as there is not so much load applied to them in acceleration etc? huge differnce in weight maybe as much 140gms per pack of a typical 5800mah pack Another question what charge rates are you applying to your cells?

Thanks N

[jasonwipf]

Niall,

You are not saving weight really when going 3s. See chart on this thread.

http://www.oople.com/forums/showthread.php?t=37230

When you go lower voltage you get worse mileage so you must now have a higher capacity or mah pack to compensate thus nullifying your weight savings of that extra cell. Go 4s in my opinion with a lower C rating (especially if your concerned about crazy power) such as 25c. It will be cheaper, lighter than 40c and your motor and esc will run much much much cooler than a 3s 40c battery set up.

another thing to watch if you are watching the car calories is how much Mah your really need and get the minimum plus 10-15% and the biggest thing that effects your mileage is how you drive. If you drive your car like a gas car with all the bleeping of the throttle they normally do you will get piss poor mileage and if you are too light and use too low of a gear you will have massive Mah sucking wheel spin as well.

[Niall Cromie]

Thanks Jason for the information i will let you know when I have finished losi 8 conversion.

[dodgydiy]

i went 6 cell, i know i havent raced it properly yet but itll stay on the local track for just over 30 mins before voltage cutoff on 4500 6 cell, and for about 10 mins on 2200 6 cell high c packs, and they are definately not heavy!

[jasonwipf]

Yep, 6s is the best for efficiency. a 5000mah 4s is equal to a 3200mah 6s all other attributes the same. To do over I would probably go 6s but i'm so vested in 4s gear I'm stickin with it for now and 4s its pretty universal at the track so if I need to borrow a pack or spare motor its easy.