The Battery Clinic

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Resources; Trade Me Store; Hybrid Battery FAQ; Remove Error Code

Looking after your Hybrid Battery

1) Do not floor the acclerator for long periods. The less you fully drain your battery the longer it will last.
Treat the battery as if you were changing gears. Step on the acclerator halfway then back off. Do this until you reach your target speed, then cruise. When the load is taken off the battery the voltage recovers. You will be able to give more power to the motor after the voltage recovers. So unlike a gasoline engine flooring the acclerator does not increase the power.

2) As far as possible keep the battery charging while driving.
By holding the acclerator down 1/4 or 1/3 the way even going uphill you can keep the battery charged while maintaining your speed. Fuel economy is also improved driving this way.

3) Every so often you should floor the acclerator for short period so that the battery does not develop a memory.

4) Memory effect is when the battery thinks that it does not have all the capacity because it is not used. Differential capacity within a string compounds this effect.

5) You don't want to fully drain your battery to zero (until the turtle shows up) but at the same time you must remind it on how much capacity it has by stepping on the acclerator for several seconds.

Prius Hybrid Battery - Problems

The Toyota Prius hybrid Nimh battery was designed to last 8 years, which for the manufacturers is the lifetime for the vehicle. So by the time we get their used hybrid import the HEV battery is at the end of it's useful life.

Reconditioning Nimh Battery

There are 40 X 7.2 volt tubes (6 X D nimh cells ) in each series 1 battery. To rebuild battery capacity we first remove dead cells and put the remaining cells on a very slow charge over 3 to 4 days. This rebuilds the cells capacity by cancelling out memory effects built up over time.

Each cell is then discharged and it's capacity calculated. Each cell is rated at 6.5 ah and we reject any cell that has less than 5.8 ah.

We replace rejected cells and recharge the battery to equalise the capacity and voltages. This battery is now as good to go and we expect it to last another 5 years.

As these tubes are not availiable as spare parts, we have started rebuilding our own tubes. Good D cells are taken and repack as a new tube with a spot welder.

Problems With Battery Computer

The battery computer (see photo ) in the battery compartment records a fault code and displays it as a triangle in the dashboard display. This does not affect the operation of the vehicle. The fault code can be cleared. We know of one person in Melbourne and believe that Manawatu Toyota in New Zealand.

A new computer cost $3000, however as this error does not affect the performance of the vehicle, it is best to put up with this minor irritant.

Driving with a low capacity battery

You can still continue to drive the series 1 prius with a low capacity battery. The battery level will go down to yellow and the turtle will appear. The engine will rev faster and there is a loss of power especially on high hill climb.

The battery will recharge to green when you start downhill. You can continue to drive the vehicle in this condition but you must be careful not to over discharge the battery.

When the turtle appears slow down and ease off on the trottle, The battery will charge even going uphill by controlling the acclerator.

Important : If you put your foot down on the accelerator you will force the battery to discharge. If your batteries are low or weak it will discharge until a cell fails. If the battery is weak putting your foot down will not give it any more power! Back off the accelerator to half way and the computer will control the charging and discharging even when going uphill. This will save your battery. Only ever put your foot down on the accelerator in short burst.

Prius Series 2 Hybrid Battery - Problems

The series 2 Hybrid uses prismatic Nimh cells. These cells will swell up due to gas build up on charging. The cells are sandwich between 2 plates.

Reconditioning is essentially the same as in series 1.

Series 2 battery

One major problem with the series 2 battery is that if left unused for several months the battery will be totally dead and not rechargeable. You will have to replace the battery

This is due to crstallisation in the cell and loss of electrolyte. If you are going on holiday for long periods get someone to start the car on a regular basis.

Buying a battery pack from a wrecker

This is seems like a good alternative as a new Nimh battery could cost more than the car is worth. However you do not know the condition of the battery. You will get at most 3 months warranty but as the battery is already 8 years old or more, problems are just around the corner. It is a sure bet that the capacity of the battery is not optimum as memory effects would have set in.

Our reconditioning service gurantees a battery with near to full capacity and we offer 1 year parts and labour warranty.