The battery in your automobile is most likely a NiMH or nickel metal hydride. It is believed that unlike NiCd batteries, NiMH batteries don't have a memory effect. This is not true. Although they are much more resistant to this memory effect, they still have it to some degree. Especially when you consider your car charges and discharges your battery hundreds of times.

The two most common failures in a hybrid battery are when one or more cells become weak and/or overheats. This will send a signal to your cars computer that something is wrong. Unfortunately, the computer knows there is a bad cell but doesn't know which one it is. That is the main reason your dealer will simply replace the entire battery pack. The battery would need to be disassembled to actually test each cell individually dealers are not equipped and probably don't want to go to this much trouble.

Your car may only charge the battery pack from 25% up to 75%. The reason for this is that when cells start to wear out, they don't do it all together. When a cell gets weak, it may charge to the full range of voltage but doesn't contain the full power that it should, this is measured in Ampere hours. It will charge and discharge faster than the other cells but since the computer is measuring the battery pack as a whole, these weak cells can become over or under charged. When they are over charged, they will heat up causing an error and when they discharge too much there is a chance it can reverse the polarity of the battery cell. If this happens, that cell will actually be working against the other cells.

​I know this is confusing so if you have any questions about how we can help, just give us a call.