Mobility scooter battery issue? - Page 1
Forum section: electronics / beginners

author: hedgewallace
author_rank: Contributor
timestamp: October 13, 2013, 08:11:20 am
content: Hello everyone,One of my mum's friends recently gave me (to fix) a mobility scooter that she couldn't charge up. I plugged it in, and it certainly wasn't charging. I checked the voltage that the 48v charger was putting out, and it was around 55v. I checked the voltage of the battery, and it was less than 5v.When i plugged it in, one thing i did notice was the charger was detecting that the battery was fully charged (trickle charging mode). I checked the voltage of the system while it was on the charger, and it was around 54v. I checked how many amps the charger was putting out, and it was around 100mA. It wasn't wanting to go into bulk charging mode.I opened both the charger and the battery open. There wasn't anything suspicious in the charger. But when i opened the battery, all 4 individual sealed battery's had been expanded around the cells.What do you guy's think is wrong with it? I'm assuming the battery needs replacing.The problem is, a new battery is $300!I wanted everyone's opinion before i go out and buy a $300 battery.

author: SeanB
author_rank: Super Contributor
timestamp: October 13, 2013, 08:29:52 am
content: Battery pack is dead, died and gone out silently. Probably they are over 8 years old, and have died from old age and overcharging for long periods. Replace the batteries, and shop around as they should be cheaper, and if they are 7Ah blocks they are very cheap. What batteries does it use, size, capacity and even a picture helps. If there is room use 4 motorbike batteries as then they are refillable as the water boils off, and will last longer.

author: G7PSK
author_rank: Super Contributor
timestamp: October 13, 2013, 09:23:13 am
content: My wife is in an electric wheelchair, so this is something I see every couple of years, the batteries develop a high resistance so the charger is telling you that the batteries are fully charged but the chair/scooter says the batteries are dead or discharged and goes into shutdown to protect the batteries, this is caused either by sulfation or drying out of one or more cells. The only solution is to buy new batteries these here in the UK average around £85-00 for 20 amp hour deep discharge SLA's and £100-00 for 40 amp hour ones. The good thing is that I have lots of perfectly useable ones as normally only one battery is affected per pack but as you need reliability for the chair (it has to run all day long or get you home if you go out) all the batteries in the pack have to be changed at once.If you try charging each battery in the pack individually you will find the bad one sling that one the rest can be used for projects.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 13, 2013, 09:31:54 am
content: Lead-acid batteries will die if they are left flat for any length of time. Symptom is they won't draw significant charge current.

author: hedgewallace
author_rank: Contributor
timestamp: October 13, 2013, 09:51:09 am
content: Thank-you everyone for your opinion. It seems to be the battery.She bought it very cheap, and has some rust, so i'm assuming it has been left around a long time without any use.I was thinking about replacing the four sealed batteries. Jaycar has a 9 Ah 12v SLA battery for $40. 4*40=$160. A lot cheaper than a new one.

author: Neilm
author_rank: Super Contributor
timestamp: October 13, 2013, 11:08:56 am
content: Mobility scooters use special batteries that can be deeply discharged safely. If you use an ordinary battery it will be damaged when it gets low.

author: amyk
author_rank: Super Contributor
timestamp: October 13, 2013, 11:34:51 am
content: The term you're looking for is "deep-cycle battery".If you're adventurous you could try an NiMH or Li-Ion mod...

author: Rick Law
author_rank: Super Contributor
timestamp: October 13, 2013, 06:55:36 pm
content: Quote from: amyk on October 13, 2013, 11:34:51 amIf you do that, make sure you analyze any safety concerns.I personally would not think such conversion is wise.When it comes to wheelchair and things for disabled persons, safety is important - they cannot get away as quickly as "normal people". If something goes wrong (say excessive heat), they may not be able to get away and left with no option but sit there and burn.I can picture a scenario where a battery was damaged say after hitting a bump and a rock, but the damage is not readily visible. As the battery discharges, a short occur and it starts to get hot. The one on the wheelchair has no option but to get up and walk away from the wheelchair - but getting up and walk away is exactly what the person cannot do thus the need for the wheelchair...