Why are my EV batteries losing charge and amps?

[U4edot]

My dad and I made an EV (electric vehicle), the problem is that the batteries are not holding a charge as long as they used to. When you have your foot on the accelerator the car's the voltage drops, and when you let off of the accelerator the voltage pops right back up. the problem is that even after the voltage starts to come back up we start loosing amps. we drop from 500A to 150-100A. we had this problem once before, but after charging it all the way and letting it sit overnight, we observed that the voltage had dropped some. so we charged it completely again. we did this about 4-5 times each time the change in voltage was less and less. Then it ran great. but that does not seem to be working this time, and none of the batteries are that old.

Anyone have any Ideas, if you need any more info don't hesitate to ask.
Thanks

 

[mathman]

In general rechargable batteries deteriorate over time due to internal chemical changes that are not reversable.

 

[U4edot]

this happened once before and was fixed by depleting the pack and recharging them. and the batteries are only a month or two old. We haven't been driving the car that much, so I don't think that they should already be dieing.

But yes, I have considered that.
Can you think of anything else that might cause this.

 

[mathman]

You could have some sort of an electrical leak or short.

 

[U4edot]

We did not buy all of the batteries at once, we bought them over a period of a couple months. So is it possible that they are self discharging. I also noticed that after the EV runs down, we can pull into a parking lot, let it sit for a wile, then some of the juice comes back. So I am thinking that the rate at which we are drawing power is grater than the rate that the batteries chemical reaction is occurring.