Mobility Scooter - Battery?

[twentysix by twentyfive]

My M-i-L's Electric Mobility Scooter is playing up. Help, Ideas please.

Basically the batteries are charged up. After not very far (much less than a mile when the range should be 8 miles) the thing won't take on small slopes which it was well able to do before. Even on the flat the thing grinds to a stop quite soon after that. The charge indicator shows battery "full" when stopped but when power engaged the indicator drops into the red zone (ie - do go away and charge it up again). A bit of rest lets the batteries recover a bit - but not enough.

So far I've tracked all the connectors and cleaned them up. Open circuit, the batteries give 25.7V (rated at 24V) but I'm unable to find a place where I can measure the voltage when under load. My guess is that the batteries need to be replaced but I wonder whether some other component may have reduced in impedance and is drawing the current. What this component might be is one question (there is a speed controller which seems to work OK) and how might I check it? How does the brake work and how can I check that (if it takes current)? Apart from the motor which seems OK(?) what else is there?

I will buy new batteries if that is the problem but I want to be sure that's the problem before I shell out ~£100 (M-i-L isn't made of dosh).

Any experience or (sensible) thoughts welcome

 

[compo]

Pretty well any battery retailer should be able to do a drop test on your batteries.

My ex had to ride a scooter, as did I for a while when I smashed up my back. The symptoms you describe would seem to indicate the battery. When mine failed I fitted leisure batteries for cheapness and they worked OK. The original gell batteries would give about 40 miles range while the leisure batteries only 25-30 miles. How often do you do that distance on a scooter! The only warning I would give if you did choose that route is the risk of leakage if the scooter tips over. On my wife's scooter we only used proper gell ones for warranty reasons, but mine was an old scooter that I was prepared to take a chance.

 

[ufkacbln]

If it is a reputable make then batteries can be sourced fairly cheaply and fitted into the present case

 

[Night Train]

How old is it?
How many charge cycles has it had?
Has it been kept fully charged after use or left flat until next needed?
Have they been run completely flat between charges or used to no more then 50% before recharging?
Has it been used to climb a lot of hills or carry particularly heavy loads?

The batteries will become less able to hold charge as they age. They also have a limited number of recharges during that life.
They should have been kept fully charged and recharged as soon as possible after use. During use they should not have been used beyond 50% of capacity before recharging.
Batteries also have a limited capacity to deliver high currents. For a short period it will be fine but longer periods of high current drain will kill a battery quickly.

I would suggest, given the limited information, that the first port of call is to to check/replace the batteries with good quality ones.

 

[Wobblers]

It does sound like it's the batteries. As batteries age, their capacity fades. The only real way to test them is to do a load test. If you've got a car headlight bulb, you can do that yourself. Connect the lamp up to the battery and measure the voltage. Measure the amount of time it takes for the battery voltage to fall to 10.5 V. A good 12Ah sealed lead acid battery should power a 12 V 60 W headlamp for at least 90 minutes. Assuming the scooter takes two 12 V batteries in series, you'll need to test both batteries in series.

 

[twentysix by twentyfive]

Thanks chaps. That all sounds very helpful.

How old is it?
How many charge cycles has it had?
Has it been kept fully charged after use or left flat until next needed?
Have they been run completely flat between charges or used to no more then 50% before recharging?
Has it been used to climb a lot of hills or carry particularly heavy loads?

The batteries will become less able to hold charge as they age. They also have a limited number of recharges during that life.
They should have been kept fully charged and recharged as soon as possible after use. During use they should not have been used beyond 50% of capacity before recharging.
Batteries also have a limited capacity to deliver high currents. For a short period it will be fine but longer periods of high current drain will kill a battery quickly.

I would suggest, given the limited information, that the first port of call is to to check/replace the batteries with good quality ones.

I can't answer all of your questions NT as we got the scooter second hand. M-i-L always has the thing connected to the charger when she isn't actually using it. She does some occasional hills and does carry heavy shopping. She's probably 12 stone too. Also, getting any relevant information from an 86yr old non technical lady is like trying to get the toothpaste back in the tube.........

It does sound like it's the batteries. As batteries age, their capacity fades. The only real way to test them is to do a load test. If you've got a car headlight bulb, you can do that yourself. Connect the lamp up to the battery and measure the voltage. Measure the amount of time it takes for the battery voltage to fall to 10.5 V. A good 12Ah sealed lead acid battery should power a 12 V 60 W headlamp for at least 90 minutes. Assuming the scooter takes two 12 V batteries in series, you'll need to test both batteries in series.

I was wondering what to use as a dummy load. D'oh - who's the dummy now? Thanks for the excellent suggestion. It is 2x12V in series but that isn't a problem

Pretty well any battery retailer should be able to do a drop test on your batteries.

My ex had to ride a scooter, as did I for a while when I smashed up my back. The symptoms you describe would seem to indicate the battery. When mine failed I fitted leisure batteries for cheapness and they worked OK. The original gell batteries would give about 40 miles range while the leisure batteries only 25-30 miles. How often do you do that distance on a scooter! The only warning I would give if you did choose that route is the risk of leakage if the scooter tips over. On my wife's scooter we only used proper gell ones for warranty reasons, but mine was an old scooter that I was prepared to take a chance.

Drop test Compo? Is that a dummy load test as suggested by McWobble?
M-i-L is a bit "iffy" with her control so I won't take the leakage risk thanks. Probably go for a direct lead acid ->lead acid replacement. Maybe get some with extra AH if they aren't too physically big.

 

[Night Train]

Make sure the replacement batteries are proper scooter batteries, designed for the higher current draw that a vehicle will demand.

Batteries have a C rating. C being the amount of current it is happy to discharge.

A 10 Ah battery with a 1C rate will only be happy discharging at 10A over an hour. 5C will be happy to discharge at 50A, for 1/5 hour. this implies that a 1C battery will really only be used for low consumption loads like an alarm back up where as a higher C battery will be better for a scooter that may draw tens of amps for several minutes at a time getting up hill to the shops.

 

[fossyant]

Deffo batteries - this has happened to my in-laws scooters - once they start playing up, get replaced. Fairly standard lead acid batteries within the casing once you look.

 

[Wobblers]

Make sure the replacement batteries are proper scooter batteries, designed for the higher current draw that a vehicle will demand.

Make sure you get a "deep cycle" battery. Unlike car batteries, or the cheaper leisure batteries, deep cycle batteries are designed to be regularly charged and discharged.

 

[twentysix by twentyfive]

I'm still "working" on this. Things of importance ( ) had to be done

 

[stevede]

Batteries on a mobility scooter generally last between 12 and 18 months dependent on use and the way they are used, charged and stored. Most reputable mobility dealers should be able to test the batteries for you using a discharge tester for a reasonable fee. (drop testing is old hat and only really suitable for car type batteries). A product called Alpha Batt is the most popular and is used by charging the batteries fully (usually on a workshop charger), and then discharging at a set rate & timing it. The system then plots a discharge graph and gives a pass or fail. The comment regarding the bulb is fine, but bear in mind that the capacity (at a 5a/h rate) can vary on the type of scooter from 15a/h right up to 70a/h meaning the time to 10.5v will also vary considerably.

If you drop me a PM with your postcode, I can probably give you the name of a reputable dealer to have this done.

If you need replacements, then buy quality gel type if that's whats is fitted currently (unless it's a very old scooter they will be gel). This is one area where you really do get what you pay for. MK Batteries are well regarded in the mobility world.

Edit: Just re read earlier posts and see that the time relates to a 15a/h battery. However. test the batteries separately and not together. It is quite common for one to be okay and the other US. I would always replace as a pair with the same rating as fitted.

Hope this helps

Regards

Steve

 

[twentysix by twentyfive]

Hope this helps

Regards

Steve

Yes that's a great help Steve - thanks. PM on the way

 

[twentysix by twentyfive]

Well It is the batteries. I put a 55W headlamp bulb across each cell (one at a time). Thanks McWobble The volts dropped to <10V after 15-20 mins. So the capacity of the batteries has dropped from 12Ah to about 1Ah.
Batteries that are in there are YUASA NP12-12. www.yuasaeurope.com

 

[twentysix by twentyfive]

New batteries on the way