Update April 14 2010:

Humm maybe the above has been a bit harsh on my Powersonic pack. After discussing the drop off in performance (after the first 1500 w-h) from my pack on the http://www.diyelectriccar.com forum, I performed some load tests.

Here are the results:

Run 1 (after full charge and sitting for 24 hrs) and pulling at max of 290 amps on acceleration

Battery No.1 sag to 10.8 v

Battery No.2 sag to 10.6 v

Battery No.3 sag to 10.7 v

Battery No.4 sag to 10.5 v

Battery No.5 sag to 10.8 v

Battery No.6 sag to 10.5 v

Run 2 (after pulling 1000 w-h from pack) and still trying to pull max of 290 amps on acceleration

Battery No.1 sag = 10.8

Battery No.2 sag to 10.6 v

Battery No.3 sag to 10.7 v

Battery No.4 sag to 10.5 v

Battery No.5 sag to 10.8 v

Battery No.6 sag to 9.2 v

Run 3 (after pulling 2000 w-h from pack) and now having trouble pulling 90 amps on acceleration!

Battery No.1 sag = 10.8 v

Battery No.2 sag = 10.5 v

Battery No.3 sag = 10.7 v

Battery No.4 sag = 10.5 v

Battery No.5 sag = 10.8 v

Battery No.6 sag is now down to 7.8 v

____________

So clearly battery No.6 is in sad shape…..

After these tests, I have replaced Battery No.6 with my spare battery and returned the poor performing battery for a warranty claim (hopefully). So MightyboyEV is now back to its old self!

I will now look at cutting back to a 2C maximum discharge setting in my controller. In my case this will mean the maximum current I will be able to pull from the pack will be 225 amps. This should help the projected life of the battery pack as the voltage sag will not be as harsh. How successful this is remains unknown. Will see how the car performs over the next few days….. 

Update April 19 2010:

Ok spare battery replaced and have now had a good play with the controller settings....

The result is... I will leave the setting as they have been! Reducing the maximum controller current settings to 50% (ie max battery draw would then be around 225 amps) reduces the vehicles performance beyond what I could cope with! So I will keep hitting these poor Powersonics harder then designed for and hope to get maybe 500 to 600 cycles life time, As mentioned above, I will review going to Sky Energy (or now CALB) 130 Ah lithium cells (or what ever the flavour of the month is then) at the end of the year . For my use I could never justify spending over $5,000 for a replacement pack with management controller especially as improvements and cost drops are still most likely to occur in the next couple of years. Range is not an issue so much as performance. I will stick with the lower voltage for this very light "kei" class vehicle as the maximum speed is better then needed for urban driving in my city anyway (just under 90km/h). Being able to use the capability of my controller (450 amps) with the 8" ADC motor should give me much better then 10 sec acceleration for 0 to 60 km. And hopefully for the full 35 to 40 km range I use daily. Any extra w-h would be very handy to drive an air-conditioner in the Adelaide summers.