Controlling the battery charge rate

Lead acid batteries should be kept in a charged condition. In the case of a wind-powered system, you may have to wait for a wind to charge the battery. But be careful not to discharge the battery too deeply, or to keep it too long in a discharged state, or it will be damaged (sulphated) and become useless. Stop using a battery before it is fully discharged. If there is a problem with the wind generator, then charge the battery from another source within two weeks.

Charging the battery too hard will also damage it. At first, when the battery is discharged, it is safe to use a high current, but later the current must be reduced or the battery will overheat and the plates will be damaged. The best way to fully charge a battery is to use a small current for a long time.

Watch the battery voltage. If the battery voltage is below 11.5 volts, then it is being discharged too much. If the voltage is high (over 14 volts) then the battery charging current is too high. Use less current or more current in the loads to correct these problems. If there is no voltmeter available, then the user should watch the brightness of the lights and follow these rules: -

• Dim lights mean low battery. Use less electricity!

• Very bright lights mean too much windpower. Use more electricity!

A good way to use more electricity is too charge more batteries in windy weather, perhaps charging batteries from neighbours' houses.

There are simple electronic circuits designed to regulate the battery voltage automatically. They are called 'low voltage disconnects' and 'shunt regulators'. If the user is not willing to watch the battery voltage, then it is necessary to fit a disconnect and a regulator.

Shunt regulator circuit

The diagram shows a simple 12-volt circuit. It is designed to switch loads on and off ('shunt' or 'dump' loads). It can also be used to disconnect user loads in the event of low battery voltage.

For a 12-volt machine you would need two of these circuits, and 4 @ 10 amp loads to regulate the charge rate.

For a 24-volt system, I suggest you replace the 9-V regulator with a 12-V regulator, and use 18 k instead of 10 k resistors between the capacitor and the positive input.

In some cases it is good to use a larger relay - perhaps an automotive one. The relays I show here do not last as long as I would like.

A good alternative would be to buy a Trace C-40 controller. This has PWM switching on one big load, and it has two battery charging rates.

DIY Battery Repair

DIY Battery Repair

You can now recondition your old batteries at home and bring them back to 100 percent of their working condition. This guide will enable you to revive All NiCd batteries regardless of brand and battery volt. It will give you the required information on how to re-energize and revive your NiCd batteries through the RVD process, charging method and charging guidelines.

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