P3026 - Block 16.... which modules are these?

It should be evident when you open the case and check the voltages. The most obvious case is when one module is 1.2V less than every other one. Pathological cases are high internal resistance or high resistance at the bus bars. I can't be sure about 2001-2003, but on 2004-2009, the lowest number is furthest from the battery ECU. So #16 would be modules 31 and 32, or the 7th and 8th modules counting from the ECU.

 

It is just the opposite on the 2001-2003. There are module markings at the base case showing 1,5,10,15,20,25,30 & 35.

Vincent

 

Heh...thanks for clearing that up!

 

You can charge up an individual module to achieve the desired voltage but I do not know that it is wise to use a 12V charger for that purpose.

1) the charger may refuse to provide voltage if the recipient battery is only at 7.5V.

2) you do not want to be charging at the rate of 1A for an extended period, that may overheat the module and cause it to explode.

3) make sure the module is compressed before you charge it or the plastic sides will likely expand and explode.

 

In the absence of a proper charger, you are probably better off to bottom balance the two replacement modules. They need to be SoC matched as close as possible. Discharge them to 7.2V, then connect the pair in parallel for about 15 minutes. Now, put them back into the car in slots 37 and 38, and let the battery ECU take care of matching the SoC of the new pair with that of the rest of the pack.

 

In partially discharged NiMH, there is considerable error in measuring SoC based on open circuit voltage. When pairing modules in series, it is best to get the SoC of each module as close to the same as possible, since there is no mechanism for balancing them individually. All the battery ECU can do is estimate the SoC of the pair and try to keep them in balance with the rest of the pack. If, for example, one module was installed with a SoC of 40 and the other with a SoC of 60, then the high module could hit a SoC of 100 when the rest of the pack is at 80. At 7.2V discharged, the SoC for either module is within a few % of zero, so there is little risk of having one of the modules in an overcharged or overdischarged situation.

 

Perfect!