Replacing NiMh 7.2V 1.1Ah 2/3A with Lipo?

[markz]

I have a remote control RC car for the kids, it doesnt run long at all.
Tons of space for a bigger capacity battery.
I could stick with a 6S NiMh at 7.2V, 5Ah $19 keeping the same charger, or go with a 2S Lipo 5Ah for same price, using my iMax b8+ charger.


Are NiMh's safer then Lipo?
What does Sub-C mean?
I assume whats labelled on the battery itself that came with the RC care, is that 2/3A is the discharge current of the battery. So if HobbyKing lists a discharge for their 5Ah NiMh packs at 10C-cont.(50A)/15C-max(75A), then realistically with their over-exagerated claims I divide everything they say by 1/5 so I am looking at 10A to 15A. Seems like I'd kill the RC machine quickly wouldnt I?

 

[Simonvtr]

Yes if you think about the chemistry used in lipo Nimh is safer.
With that being said all my daughter toys have lipo in them.
From here zoomer dino/dog, to her quadcopter and losi mini-t.
As long as you can keep the pack from bouncing around and keep it balance it should be safe.
You might also want to get a cheap 2s cutoff switch and wired it to the pack to prevent your kids from draining it to low.

 

[markz]

Yeah I might just stick with the NiMh's because from what I've seen they are in cans, not pouches.
Then I dont have to mess around with charging on a seperate charger, just use the slow 0.5A adapter that came with it.

With the space I can keep the 1.1Ah and parallel wire in the 5Ah, should be an hour or so of fun for the kids and not 10-15 minutes as it currently stands. The cars themselves, we have 2, just givver real fast.

I only question now, the label of 2/3A on the stock battery, compared to the 10C/15C of the 5Ah Turnigy cans. So 50A/75A are over exaggerated I know, so take a quarter of it its still 12.5A/19A. I don't wanna fry the kids toys. I have no clue how these toys are setup, I see a very small ESC with 4 FETS sticking up, an on/off switch.

I cant remember if the rc cars turn off from lack of voltage, I remember them getting drastically reduced in power and I tell the kids to stop, time to recharge. So yeah, I guess I do need a cutoff switch for the NiMh.

 

[amberwolf]

Before paralleling any NiXX chemistry you might want to read around on the various threads about that; there's also an ES wiki entry about it. Mostly it's an issue with charging, but I recall something about discharge....

Also, I doubt 5Ah in a sub-C NiMH cell. Sub-C means smaller than a C-size battery. I had D-size that were supposedly 8Ah when new (werent' anywhere near new when I got them so no idea how true the capacity claim really was); the sub-C is a LOT less volume and is unlikely to be able to contain 5/8 the amount of a D.


Also, 2/3A may mean a battery can size; an A battery would have certain dimensions, so a 2/3A would be 2/3 that size.
https://en.wikipedia.org/wiki/List_of_battery_sizes

 

[Simonvtr]

I wouldn't parallel the new battery to the old one if that is your plan.
They do not make sub C batteries like they used to back when I used to race 4wd rc. We can get matched sub-c packs with rated 7200mah.
But now all the pro rc racing has switch to lipo so the best you can find are 5000mah sub-c.
If you check out any rc shop you can find better rated AH battery then the stock one that came with the toy.
The higher the "mah" the longer the run time and takes longer to charge.

http://www.amazon.com/Tenergy-5000m...qid=1453209180&sr=8-19&keywords=sub+c+battery

Just remember to try and keep the voltage the same.
Like if the old battery is 7.4v then don't go 12v replacement battery.

You notice the toy running slower due to the NiMh voltage curve from full to drain.
And I would not worry about draining the battery really low. They are not like lipo and would not be damage due to draining to low.
I used to race 4wd pro rc and we drain them down to almost nothing in 5min rc.