7.2 volt options
 

I have an old T-maxx I run for a stress relief. It has a 7.2vdc NIMH battery for the electric start. I want to convert this to a lipo or Life battery Just not sure what I should use??? 2s life or 2s lipo?


Pass you soon...

LiPo has a little higher nominal voltage (7.4V compared to 7.2V), while LiFe is quite a bit under (6.6V), on the other hand, LiFe aren't as delicate as LiPos (they're not known for turning into a fireball when handled wrongly, as LiPos certainly are.) Your choice, basically.

If it were me I'd use the LiPo. .2 volts is a minimal difference for an electric motor. Your only concern would be overheating but since a starter isn't going to run for long you shouldn't have any concerns there either.

Thanks for the replies...

Pass you soon...

The voltage difference between LiPo and NiMH is not the problem though. Fully charging a LiPo and then only using a fraction of it at the track then after a while, not wanting to discharge it to storage level each time any more - that's the "danger" with LiPos in this type of application.

Good point!


Pass you soon..

There is no danger in leaving a lipo battery charged. You may shorten its life but it will not blow up just sitting around charged.

Leaving lipos fully charged will cause them to swell. you'll see.

If one doesn't want to leave the LiPo at full voltage (4.2V/cell), then just charge it to something safe like 3.7V/cell or thereabouts. It'll be safe to leave it at that voltage level indefinitely, and there is more than enough energy and power available to turn over a starter. No need to overthink this stuff.

No, it will not suddenly blow up just sitting around, but it'll get damaged over time, so it might blow up on your charger one day. Or it might just die quietly and you'll be left needing a replacement battery unnecessarily soon. Just for being lazy... nah.

In which case you could also just use a LiFe battery (since you give away the LiPo's advantage of higher voltage anyway), with which you don't have to worry about charging it only half way each time (and keeping half of its capacity unused). Wouldn't call that overthinking - just thinking (which has never hurt anyone, by the way;)).

Never said it was good for them, only that it wasn't dangerous.

Noticed the quotes around the word danger I used in post #5? ;)

Nope. :)

A fine solution, if one has a spare 2s LiFe pack sitting around, but I don't think I'd buy a new pack just for this application.

I do more than enough thinking at my day job and as a parent of two young boys to realize that it does indeed hurt (some days more than others).