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Clean up a battery pack from RAV4 EV

By Nikolay Shishkov • October 08, 2018

batteryravrav4 ev

The following post is trying to document and describe how I clean my RAV4 EV battery packs when I get isolation error.

Dirty pack

Dirty battery module and a tooth brush

So the cleaning is very simple. I use a boric acid solution in water.

A bought boric acid in a white powder form from the local paint shop. The solution used in the cleaning needs to be saturated - you should see some of the boric acid powder not dissolved in the water.
I put the solution in a spray bottle... and then I shake the bottle well before spraying some of the acid on the module.

Then I use the brush to work the solution on the dirt. Then I use paper towels to dry the solution of dirt and acid from the surface of the battery. Very important to really wipe the stuff dry. When boric acid dries out it produces a conductive layer... and this is the thing we want to avoid.

I initially test to see if there is any voltage between a battery module pole and some random points on its surface. If there is, this module needs cleaning.

0.17v between negative module pole and the surface of battery

Using old toothbrush to work the boric acid solution on all corners

Wiping all the acid and dirt is very important since the dry acid produces a conductive layer.

Drying the boric acid solution - helping with a screw driver... but very gently

Measuring again voltage from the pole to the surface to make sure the cleaning was a success. If I see voltage again I repeat the cleaning until there is no voltage.

Testing to confirm that the cleaning was succesful

Now when the modules are clean, dry and tested it is time to clean up the battery pack tray.
First vaccum...
Then using the same spray bottle I spray some wipe and then wipe with clean wet paper towel. Important to use new towels so not transferring dirt or acid from one place to the other.

Battery trey with lots of dirt that can conduct electricity when wet.

Another view of the dirt

After cleaning some of it

Clean pack

Very clean pack

Really clean pack

The fan assembly 3.18kg.

Mounting stuff back

A schematic showing the order of disonnecting and connecting stuff

Battery modules are in

Another view of the pack and the modules in it

This is not exactly OK... using nordlock washer is probably not ok, but is better than the previous one

Let's not forget the cables for the emergency disconnect

Pack ready for mounting

Pack ready for mounting

A screw on a leash ... helping to guide the pack under the car

All done!
In and out in 4 days.
It is not complicated, but required a lot of work.

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