The long awaited 20Ah Greensaver Test Results

Greensaver 20Ah Battery Testing

Apparatus:

Microprocessor controlled battery discharger and charger.

4 x 1 Ohm 200 watt resistors. Hard wire configurable.

Relay to switch between 2 discharge currents

Microprocessor calculates V, I, Temp, Ah, Wh and Peukert Factor.

Readings are taken every second and logged to the serial port of a computer for graphing.

After discharge, the battery is automatically charged.

The discharge cutoff voltage is programmable.

The negative figures in the LCD indicate that the battery is being charged.

I know, it looks like a weapon of mass destruction :)

Goal:

To determine the Peukert effect of the 20Ah and 27Ah Greensaver battery.

The reason for perform the test is because the specifications state a low Peukert factor fro these batteries and I wanted to verify this before purchasing a pack of 50 batteries.

Results:

Discharge curves. (note glitch in V5 between seconds 3 and 12. As this is only a 9 second occurrence, it does not affect the overall result.

Peukert Effect:

Conclusion:

The average Peukert factor of 1.105 is low compared to other batteries that are usually greater than 1.13 for batteries of similar capacity. The calculated Peukert factor from the 20Ah specification sheet is 1.07. My tester is probably not that accurate but is sufficient to confirm that the battery performs close to specification.

Given this result, if Lead acid batteries are used, they should have superior performance under load and give a long service life.

Original discharge data is available in an Excel sheet upon request.

Next steps:

I also have a 27Ah battery that will be tested next.

The high current wiring will be upgraded to allow testing at 40A

The discharger will also be reprogrammed to continuously charge and discharge a battery to determine de rating over time.

Charging:

The charge curve for the 20Ah battery is below.

Update - Batteries - Tester - Diff - Steering - VFD - Tray

It has been a few weeks since my last post so an update is in order. photos to follow.

1. I received the Greensaver batteries (20ah and 27ah - 2 hr rate). The port chargers were unbelievable! These would have to be the 2 most expensive batteries in Australia! Lesson learned about sea-freighting goods

2. I have built a micro controller based charger / discharger. It will measureand log to a PC the following aprameters during discharge and charge Volts, Amps, Watts, Ah, Wh, temperature and the all important Peukert factor. It uses 4 x 1 ohm resistors. The resistors can be wired differently to vary the test current. I am waiting an LCD from Futurelec and a charger from ebay's ecrazyman.

3. I have bought a diff from pick'n'payless . It is a 5.125 ratio from a Hiace van. All going well I will install it this weekend. This gives a theoretical top speed of 94km/hr at 4000RPM

4. I also bought a manual steering box from pick'n'payless for installing this weekend.

5. Better VFD. I bought a better Danfoss 5042 VFD off ebay. So, if anyone wants a Danfoss 6042VFD in an IP54 case I have one looking for a home. I have removed all the AC components from the cabinet to minimise losses and will feed it DC directly to the soft charge circuit.

6. The ute has a tray back which was way too wide for the body. To tidy up the looks I have narrowed the tray to be the same as the body (100mm off each side) and shortened the back. If I need sides I can get them from the manufacturer which is encouraging.

At the moment the carport looks like a car wreckers yard, but things should start coming together in the next few weeks. I am still waiting to borrow an engine hoist from my neighbours.