The specifications of the vanadium battery designed for the golf cart are presented below. The actual electrode area of the battery was determined by the mould already developed from a previous project. This was due to severe budget restrictions for this small demonstration project and the electrodes and flowframes had to be fabricated using the same moulds as manufactured for the Solar House battery project.
The size of the flowframes used in the golf cart vanadium battery are for electrodes with an area of 1500 cm2. The resulting battery is thus oversized for the golf cart. The optimum size for a vanadium battery specifically designed for the golf cart would thus be approximately one quarter that used for this initial trial. With the current available vanadium battery technology a one quarter size battery would give superior performance to the current battery on the demonstration golf-cart.
Specifications of the Electric Golf Cart Vanadium Battery.
1. One 30 cell battery stack.
2. 60 L of positive and 60 L of negative electrolyte.
3.The theoretical peak power is 4.1 kW.
4.The theoretical capacity is 3.9 kWh.
The actual power and capacity is very close to the theoretical values.
The 2 pumps used to pump the electrolyte around the vanadium battery system were 240V AC and a battery monitor-inverter was developed and used to power the pumps of the battery system. The pumps through the inverter were found to consume a current of approximately 7A total for both pumps at a battery voltage of 38V with an operating pressure of 45 kPa each.
Preliminary road trials of the vanadium battery powered golf cart have already been undertaken. The golf cart was found to perform exceptionally well carrying two passengers with ease and a total vehicle weight including passengers in excess of 400kgs.
In the first preliminary road trials the battery voltage for the stationary vehicle with the pumps off was 41.4V. The battery voltage for the stationary vehicle with the pumps on was 38.9V and the battery voltage for the moving vehicle on a flat road was 37.6V.
The vehicle can also be run with the pumps off, running simply of the charge available in the battery stack. This will obviously limit the distance that can be travelled however, in this case the battery voltage only decreased from 41.4V for the stationary vehicle to 40.7V when the vehicle was moving.
The pumps can therefore be run intermittently to conserve power with the preferred option being the employment of DC pumps. The AC pumps were employed in the current trials due to suitable DC pumps so far proving difficult to acquire.
The vanadium battery powered golf-cart has been running for over 2 years. In
this time the vehicle has undergone endurance testing, speed testing and
continually been used for demonstration purposes. The maximum speed is governed
at 19 KPH and the vehicle has travelled over 250 km.
The number of battery cycles are over 300 since many cycles were carried out
before the vehicle left the laboratory.
The golf-cart can be fully charged in around 20 minutes by simply connecting a
battery charger to the vehicle. However, one of the main advantages of the
vanadium battery is that it can be instantly recharged by simply replacing the
discharged solutions with recharged solutions. The solutions are never wasted
since they have an indefinite life. They are simply recharged and used again for
an indefinite number of cycles.