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Home > Technichal info > How to test mobility scooter batteries
How to test mobility scooter batteries

How to test mobility scooter batteries

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We now offer a replacement battery service by post. Call us for more info.

Mobility Scooter Battery Testing Service

Call us for details of how we can help you replace the batteries in your Mobility Scooter or Powered Wheelchair.

The batteries fitted to most Mobility Scooters and Powered Wheelchairs are a very special kind of battery.

There similarity to car batteries is in shape alone. A car mechanic or electrical engineer will have very little knowledge of how an SLA AGM battery actually works.

A mobility scooter battery cannot be tested accurately on a load tester.

The correct way to test a SLA AGM or Gell battery is by measuring the length of time it takes to discharge.

Unlike a car battery an SLA/AGM battery requires a very long slow charge in order that it can hold its charge for long periods of time.

A car battery only needs its power to start the car and after that everything is powered by the cars alternator.

Mobility scooters do not have the luxury of a built in charging system so they need to hold charge for long periods of time.

All mobility scooters and powered wheelchairs are powered by 2 x 12 volt batteries ie they all have 24 volt motors. The range or distance is rated in amp/hours for example a 12 volt 18 amp/hour Battery will travel further than a 12 volt 12 amp/hour battery.

The chart below will give approximate distances/ranges that can be expected of batteries in normal use.

Battery size


Charger required

12 volt 12 amp/hour

6 to 8 miles

2 amp

12 volt 18 amp/hour

12 to 14 miles

2 amp

12 volt 34 amp/hour

15 to 25 miles

4 amp

12 volt 45 amp/hour

20 to 25 miles

5 amp

12 volt 70 amp/hour

30 to 35 miles

8 amp

12 volt 100 amp/hour

30 to 40 miles

8 to 12 amp

The tester we use is known as a capacity tester.

The testing process

First of all we charge the batteries up fully and then we set the tester to the required settings to match the battery being tested. The tester will discharge the battery at a slow rate until the battery has only 9.5 volts left in it. After that the tester will convert the length of time the discharge process took and the size of the battery on test and produces a percentage figure. A new battery usually test out at 120%. A battery testing at 65% is normally classed as a fail as although the batteries will still power a machine up they would have no range.

Mobility scooters and powered wheelchairs will not operate at a voltage lower than 18 volts.

So it is important to realise that although a pair of batteries can have 24.5 volts in them when not under load they will very quickly drop down to 18 volts when the machine is put into action.

Generally a battery that has 12.25 volts in it at standing position is deemed as being flat.

A fully charged SLA/AGM 12 volt battery will have as much as 13.6 volts in it when fully charged.

Replacement Batteries

When purchasing batteries it is important to buy top quality.

I am sure that everyone has tried using cheap batteries in a torch or other device that have been bought from poundland or other similar budget supermarkets but at the end of the day you always return to Duracell when you need a battery for a product you depend on.

The same goes for mobility batteries. Some are very good some are very poor.

We use MK batteries only and have done for the past 6 years. Before that we tried many different brands but always returned to MK for certain reliability.


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