Replace Hybrid / EV battery pack

[ThruSST]

Hi Jozzy

The Battery pack doesn't actually need changing in it's entirety although for longevity it is best to do it that way.
The main issue for these batteries (which may or may not be the case for yours) apart from getting old & losing capacity is that the top packs centre modules get heated more than the rest of the pack and therefore their lifespan is reduced. At some point depending how you drive they will be asked to supply a large amount of current which will drain the Battery and make the voltage on the centre modules drop more rapidly than the outer ones. The ecu picks this up and decides that it's too low compared to the higher voltage modules and switches the Battery out of the system and the car will drive in petrol electric mode where the generators power goes straight to the motor and your fuel consumption increases.
You can see how mine has a few voltages that drop more than the others in the graph at the bottom of this post. This test s built into the Android app Hybrid Assistant & is really easy to carry out.

I managed to get a secondhand HV battery for £300 & stripped it all down to the two sections and connected the modules in parallel so I could charge each pack's modules together at a low voltage and then equalise them to test their capacity. It's not a high precision way of doing it but it works and I could easily do it in the garden with no extra test gear than I already had.
Removed my pack from the car and took it apart and then load tested all of the modules individually and picked the best ones from mine and the "new" pack to make up into a better top pack than the one I'd just removed from the car.

The result is that I have a perfectly functioning Estima which will last a few more years yet with this battery pack.

Last week I had to drive from Southall to Heathrow, down the A30 to the M25 then the M3 & A331 in atrocious traffic and incredulously managed to get just under 64mpg out of the car as the traffic was so heavy.

So anything is fixable it just depends how much time & money you want to put into it.