Interim Battery Pack (Mixed Thundersky and Nissan Leaf)

I have been driving MR02EV for about 4 years using a battery pack consisting of 56 Thundersky lithium-ion cells totalling 201.6 Volts and 12kWwh; it has served me pretty well. Initially my driving was in city traffic 0 – 60 kph so performance was not an issue and the 70 kilometre range was more than adequate.

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However, the MES motor and inverter are rated to 400 Volts so an upgrade was always on the agenda and when I started a new job in 2016 the profile of my daily commute changed, so it was time. Whilst the distance was almost identically, the new trip was along urban and flowing roads, generally 60 – 90kph, meaning vehicle performance became an issue and range was impacted.

Since Thundersky's were no longer available it was not a simple case of purchasing more cells, I would have to carefully match them with another brand, or replace the lot.

I chose to replace the Thundersky pack because a friend was able to use the old cells in his home solar battery bank and Nissan Leaf batteries became available. But, due to cash flow considerations I had to purchase the Leaf modules in two batches. So for several months I had 56 Thundersky cells in the car and 14 Leaf modules on the bench, but when a number of the Thundersky cells dramatically lost capacity I started to think …. why not use both, what could possibly go wrong?

Fortunately, both batter types are 60aha and nothing did go wrong when I put 36 Thundersky and 14 Leaf batteries in series. Although the BMS did have a hard time managing the charge cycle, particularly balancing. The mixed pack totalled; 244 Volts and 14.7 kWh.

The Front Pack - Leaf

The Rear Pack - Thundersky

I would not recommend building a pack from dissimilar batteries, but it did work, and was interesting to watch on the BMS display when the pack was under load. The Thundersky cells sagged, whilst the Leaf modules remained pretty stiff.

Interesting graph. Fully charged Leaf Modules, with partly charged Leaf Modules, with the old Thundersky's.