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OT: Wheelchair batteries

Been asked to look at a friend's wheelchair because they're finding that a full charge only lasts to the shops (a lot less than half a mile) and he has to be manually pushed back. They only recently bought the chair from a friend of a friend of a friend of theirs because the guy who used to own it has now died.

Anyway, the batteries currently fitted are these

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(link goes to Rapid Electronics
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Europa 12V 33Ah ones, connected in series on the chair to give 24V. Tested with a digital multimeter each battery is reading 12.8V off load and when connected together for use on the chair, total voltage is 25.6V off load. The charger is an electronic type and has LEDs to indicate the state of charge and when connected, the output of the charger measured across the battery terminals is 28.8 to 29.1V.

Unfortunately, I can't measure the current output of the charger (rating plate says it gives out 5A) because it connects to the control box (steering joystick-type thingy) of the chair by some sort of 3-pin DIN-type connector - and even while I'm typing this I've just realised I could measure it at the battery end rather than output of the charger end. What a bleedin' plonker I am eh?

Anyway, the batteries are sealed and, even if they weren't, there's apparently no liquid electrolyte to draw up into a hydrometer to test each individual cell - the acid is in gel form, I believe. There are labels on the batteries stating "19 June 03" so they are four and a half years old.

For this reason alone, I'm suspecting the batteries as being the problem rather than anything else, but I'm also concious of the fact that 118 quid for new batteries is not an inconsiderable sum for my mate to pay out - especially if I'm wrong and he still has to pay to get the fault fixed so can anyone give any pointers to anything else, or confirm my not brilliant diagnosis that it's the batteries?

Cheers,

John

Reply to
John
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Burgerman on uk.rec.cars.modifications will probably have a good idea. He'll probably also tell you how to make it do 20mph and pop wheelies ;).

Reply to
Doki

Almost certainly the batteries. When they're in series it only needs one cell to die.

You could try charging the batteries individually using a motorbike (or similar) charger if you have access to one.

I'd try measuring the voltage when they're on load - you could always put a headlight bulb on and see how long to discharge.

Last time I needed something similar (for a lawnmower) I found that there are battery specialists out there who give pretty good prices - half the price of the lawnmower outlets.

Reply to
TTT

These do all kinds of batteries, including mobility scooters. Will give you an idea of prices to compare.

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Reply to
Redwood

Thanks Doki - just posted over there.

Reply to
John

Good idea about the headlight bulb TTT, I'll give it a try. Thanks mate.

John

Reply to
John

Thanks Redwood, I'll have a look there.

John

Reply to
John

No probs. Copied from the site;

There are many different brands of mobility scooter battery and wheelchair batteries. At Tayna we offer six brands to help cater for people buying on a budget to people looking for the best of the best. All of our mobility batteries are either sealed lead acid or gel. To choose the correct battery for your application you need to check the capacity (Ah) of the battery already on the scooter or wheelchair. Some mobility scooters/wheelchairs have room for larger batteries than the manufacturer has fitted which will give a greater journey range and longer time in between recharging.

A mobility scooter battery is classed by it's Ah value in the following manner: 7Ah Mobility Batteries, 12Ah Mobility Batteries, 15Ah - 22Ah Mobility Batteries, 24Ah - 26Ah Mobility Batteries, 31Ah - 34Ah Mobility Batteries, 40Ah - 44Ah Mobility Batteries, 50Ah Mobility Batteries and 70Ah Mobility Batteries. These are the main values which differentiate the physical size of mobility scooter batteries. All of these sizes can be found on our website manufactured by Yuasa, Numax, MK, Sonnenschein, Power Batteries and Budget.

Most Mobility scooters and wheelchairs are fitted with two 12 Volt batteries wired in series to create a 24 Volt system. These two batetries are usually charged using an automatic 24V batetry charger. There are many types of mobility scooter charger depending on battery size and manufacturers unique plug system. The most popular is the three pin (3-pin) plug which inserts directly into the scooters battery system. If this is not the case a normal

24V automatic charger with crocodile clips can be used.

If you cannot decide on which battery you need, you can use our Mobility Scooter and Wheelchair Battery fitment guide or call us on 08452 261860 for assistance.

Reply to
Redwood

£118.00 is reasonable for two batteries , rs components charge £62.00 each plus vat

It does sound as though the batteries are duff , best way to check is charge them up then leave the chair for 24hours then measure the voltage accross the battery both off and on load wit the charger disconnected

At 5 years old the batteries should be replaced anyway

Reply to
steve robinson

You need to do a high discharge test to check the condition of lead acid batteries - voltage alone doesn't really tell you much. A battery specialist should have a decent electronic tester that gives chapter and verse on their condition. IIRC, even Halfords have them. Not sure they'll have anyone who knows how to read it properly, though. ;-)

However, 5 years is a good life for batteries used under these conditions.

Reply to
Dave Plowman (News)

They're gel batteries and you need to make sure you only use the correct charger. Marked as suitable for SLA types.

Reply to
Dave Plowman (News)

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