Monday 28 April 2008

Greensaver batteries on order

I have ordered some sample Greensaver batteries. A 20AH, a 27Ah and a 12 volt charger.

I have also ordered 4 x 1 ohm 200w resistors for building a battery analyser. I am workon on the Bascom AVR code at the moment to check their capacity at different loads. The Peukert fact er of 1.09 for the 20Ah unit seems a little too good to be true but if it tests out after many cycles then they are great value for a bit over USD20.

Wednesday 23 April 2008


I have been browsing the workshop manual for a 93 Hilux / Tacoma and checked the vehicle and it has an electronic speedo. This is brilliant because I wont have to retrofit one.

The speedo just requires a 4 pulse per revolution input from the shaft.

There is a pulse output from the Danfoss VFD that is programmable. I will also be able to adjust the VFD output to compensate for the change in differential ratio.

This setup will require that I use closed loop control to have an accurate speedo.

Monday 21 April 2008

Vehicle Purchased!

I have finally purchased a vehicle for the conversion.

It is a '92 Extra Cab Toyota Hilux ute (Tacoma Pickup for our American viewers). Model is a RN90R.

The good:
The right price for Sydney. These vehicles are about $2000 more expensive in Sydney. I payed $4k for it. The body is straight apart for a ding on one guard.

The interior is in good condition apart from the drivers seat that will need replacing.

The Bad:
It looks like it is from Mad Max as it has been painted black and has very dark tinted windows
The tray has no sides
The black respray is peeling off in places.
It has done 330,000km so I can not really sell the motor

To Do:
Replace drivers seat and various trim pieces inside.
Remove interior for cleaning. (I did this on the weekend. I just need to wash the carpet.
Investigate re-paining the body white or touching up bad paint job.

I took it to the local tip to put on the scales. The kerb weight (no driver or fuel) is 1250kg. A little more than I expected as it has an aluminium tray back rather than a well side. The GVM is 2050 allowing 800kg of load.

The rear axle has 41% of the weight. I will mount the motor as far forward as practical in order to maintain the balance.

I would still prefer to remove the gearbox. There is a 5.29 ratio differential available (existing is 4.1) from an early Hiace. This would give a final drive ratio a little high than third which may be acceptable. The top speed would be about 80km/h which is adequate for me.

Saturday 5 April 2008

Battery Balancer

I have been thinking about how best to balance my chain of batteries, all 50 of them.

As there are 50 units the price could be quite significant.

Ideally a microprocessor based system would be implemented with isolated sensors on each battery however at this time it is cost and time prohibitive.

There are 2 alternatives I have seen the first would place 15V Zener Diode in series with a light bulb or suitable resistor across the battery. When a battery exceeds 15 volts, the Zener and lamp would bypass current proportional to the over voltage. This would be the simplest to implement.

Another alternative is a more aggressive voltage clamp described here.

The clamp voltage will have to be above the maximum charge voltage from the chargers and the regenerative braking.

Under regen this is 15 volts. Under charge this is about 15 volts but will need to be measured on the charger.

Obviously this solution will only work under charge but should be sufficient for now.
I will test it on my self balancing scooter first.

Thursday 3 April 2008

Greensaver Silicon batteries

I have just been reading about these batteries.

They seem to cope better than Lead Acid on high discharge. Here are the specs of the 2 models I am interested in.

27 Ah

20 Ah