Model Boat Mayhem

Technical, Techniques, Hints, and Tips => Batteries & Chargers => Topic started by: sigfortunata on November 22, 2015, 05:07:48 pm

Title: Which LiPo???
Post by: sigfortunata on November 22, 2015, 05:07:48 pm

I'm running 2 x 480 brushed 8.4 rated motors from 2 x 7.2v NiMH 4200mah batteries.


I get quite a good run time but they are heavy and slowing me down, hull needs virtually full power to plane


Would size/spec LiPo battery would be the best direct replacement or improvement without changing any other running gear


(so please don't suggest getting brushless too, yes I know they may well be better but at the moment they are a cost to far!!)


Steve

Title: Re: Which LiPo???
Post by: inertia on November 22, 2015, 05:41:04 pm

Steve
Your NiMH packs weigh around 825g together. Two 2S 4000maH LiPo packs would weigh 430g and two 5000maH packs 550g. Reducing the weight by almost 50% would yield not only extra speed but longer duration as your batteries are not wasting as much power just shoving themselves around. I think it's called a no-brainer..  8)
You'll need a balance charger and a couple of low-voltage alarms but no other changes.
You can check out other possibilities on Component Shop's website. http://www.componentshop.co.uk/ (http://www.componentshop.co.uk/)
DM

Title: Re: Which LiPo???
Post by: sigfortunata on November 22, 2015, 06:02:33 pm

Hi Inertia


thanks for your reply, you're right, weight reduction in the first instance is the way forward however I pick your brain some more?


At the moment I run 4200mAH NiMH but if I change to 3000mAH LiPo  in your opinion will the weight reduction and increased power offset the reduction in stored charge etc.  I'm looking to get about 30mins plus run time?


Just that as with everything upgrades cost and 3000 lipos are nearly half the price of 4200.....or should I just bite the bullet and sell one of my offspring?


Steve

Title: Re: Which LiPo???
Post by: Subculture on November 22, 2015, 07:40:30 pm

In my experience NiMh give poor duration when pushed hard, whereas lipo deal with it effortlessly unless they're really lousy batteries.

3Ah lipo should be able give you 30 minutes+ running time, especially if you're not gunning it the whole time.

Title: Re: Which LiPo???
Post by: inertia on November 22, 2015, 11:18:50 pm

Hi Inertia
thanks for your reply, you're right, weight reduction in the first instance is the way forward however I pick your brain some more?
At the moment I run 4200mAH NiMH but if I change to 3000mAH LiPo  in your opinion will the weight reduction and increased power offset the reduction in stored charge etc.  I'm looking to get about 30mins plus run time?
Just that as with everything upgrades cost and 3000 lipos are nearly half the price of 4200.....or should I just bite the bullet and sell one of my offspring?
Steve

SubC has it about right, and I can't advise you either way. There are too many variables involved, but you will certainly get more duration from the bigger pack.
Children are not fetching a good price at the moment... Grandchildren even less.
DM