The car is really fun. But because the car is used and the batteries are old, the capacity of the batteries do not last long. I needed to recharge often. I thought about buying a new battery pack. The thing is that the battery pack is very special. I got a shock seeing the prices, around 29,-$. I took a look at the batteries and found out that these things are poor nicad types. The capacity is rather low and nicad batteries are likely to have the memory effect. Then I took a look at the charger ... oh no, it was one of those cheap and simple constant current chargers. These beasts kill the batteries!
So I decided to buy some nimh batteries with mre than 2500mAh capacity. More as twice the capacity of the original ones. To keep the batteries in good shape I also bought a charger that works with delta voltage charging. Using this charger it is possible to charge the batteries in short time without destroying them.
- soldering iron
- proxxon (or dremel)
BTW. the "Reading Man" is one of my greatest supporters! He always knows how to do things and he tells me .. ;-)
Step 1: Removing the old cells
Cut the case along the side and cut deep enough so that you can see the cells inside. Do only cut the main plastic case not the cut the hinges. Because you can not cut the case complete the rest has to be done by putting a screwdriver in the slit and break the case. Be careful but steady ;-)
Take out the batteries and remove the wires.
Step 2: Preparing the new battery pack
All batteries need to be put in series. We like to get 7.2 V out of six batteries with 1.2 V each.
Put attention to the polarity of the batteries and the connectors. On the plastic case you can see a small + and a small -.
The new batteries fit exactly into the case. I used AA size batteries, NIMH with 2700 mAh capacity and 1.2 V cell voltage.
After putting everything back into the case, close it. Pay attention to the small guiding slids!
Fix it with glue.
Step 3: Modifying the charger
To be shure that no one ever puts the charger into the power socket ... I cut of the pins. Now I can lay it on a table beside of the new charger.
I removed the cheap charging parts and soldered some wires on the contacts to connect the new charger.
The new charger is connected via a small power plug. On the picture you can see a test setup. I did not have a power plug by hand ...
After charging I put the new battery pack into the car and ... whow ... more power than ever!