I have an RC car for my young son which uses a rechargeable lead-acid battery. Battery is 6V, 4.5 Ah/(20Hr) by First Power. This battery powers his car & him until it runs out (complete discharge). Battery size is like a deck of cards only 2X as thick.
No clue what 20 Hr means, battery generally lasts about 30 minutes on a full charge before dying completely. After very few uses I think the battery useful life is decreasing.
I wish to replace/upgrade the power system. I have in my closet 4 Metal Hydride rechargeable D-cells (1.2V 10 Ah) + 4 NiCd D-cells (presumably 1.2V). The car also uses a standard charger which plugs into the car. Taking the battery pack out is too complex for everyday use: I'd like to use the plug & the adaptor, which is probably not a smart charger (I do have one but this requires putting the batteries in it). Thus I can recharge the car without taking the battery pack out.
I have 2 choices: replace the lead acid battery with D-cell or other rechargeables or buy another (much larger) 6-V lead acid battery.
Any recommendations? I've heard that lead acid batteries are killed by deep discharge which is exactly what this car gets. Thus I'm not inclined towards another lead acid. On the other hand metal hydride batteries like deep discharge but I'd need to put 5 or 10 of them together and use a standard 6V charger. Also I've noticed on-line that they sell 7.2V 4.2AH battery packs with a smart charger. It says not to charge the packs together, however, there really isn't any other way. Also if I put 2 packs together I can have 8.4 Ah. The motor may run a bit faster but hopefully things won't burn out at 7.2 V instead of 6.0???
The local RC store (Warricks hobby superstore) blew me off and said "junk like that is not interchangeable: buy a whole new car at toys-R-us, we don't deal with such things: Goodby"
Anyhow any insights would be appreciated. I have a [chemical] engineering degree so I should be able to rewire stuff if needed.
Thanks!!