12v sealed batteries. Am I gonna blow myself up?

[tflnemesis]

Hi all,

My missus has back problems from a motorbike accident we had a few years ago, been advised by the doc not to walk for more than 10 mins. Anyways FIL heard about this and knew a relative that had a couple of mobility scooters sat doing nothing since the relative has been moved to assisted living.
So he bought them, one of them is fine, charges well, holds the charge etc etc.

The second one he wants to sell to recoup some of his outlay. This one had new batteries about 18 months ago, sealed lead acids, but it won't charge and has been stood about 7-8 months. After running a load of tests the charger is only outputting about 2.5v and the batteries are showing a voltage between 5 and 6v.
The charger is a 'smart' charger so I am guessing its not charging because its not detecting the batteries properly. I don't have any other chargers apart from a small 'smart' charger that my neighbour has atm and its probably going to be the same as the supplied charger.

Now, this is the blow myself up part, I have a bench PSU 12v 5A that I am thinking of hooking up to the batteries to possibly get em past the threshold that the proper charger will detect. So, is this possible or am I setting myself up to blow up a couple of batteries? I know its not a good idea but would it work?

 

[brightspark]

5 amp will cook them fast. 500 ma more like look up the spec on the proper charger

 

[gaz1]

have you tried to recondition the batterys at all?

ive seen this doing a recondition on some batterys it works

https://www.ebay.co.uk/itm/blue-poi...294540?hash=item4b309f510c:g:hV4AAOSwI59aMXx2

 

[tflnemesis]

The proper charger has an output of 24v 4A, so 2 batteries in a series circuit. I was going to do them singly using the bench psu.

 

[tflnemesis]

If they're showing 5-6v across the pair, they're probably toast and no magic box will really fix them.

Sorry i wasn't clear, they are showing 5-6v each, I had everything disconnected when running my tests so I could test them singly.

 

[bourbon]

They have probably been stored in a discharged state. even if you manage to get them up to where the smart charger will 'read' them. they won't hold charge for long afterwards. weigh them in.

 

[tflnemesis]

Thanks for the replies everyone, I am going to give it a go. From the replies i figure i haven't got a lot to lose and worse case FIL will have to weigh them in and get a 'new' set.

 

[CompoSimmonite]

My mobility scooter batteries only last just over a year no matter how I use it so if 18 months old then I doubt they will be very good even if you manage to trick them into taking a charge. The worse thing for a mobility scooter user is batteries going flat as you are left stranded so you have to ask yourself if you are happy for missus to take that risk ?

 

[Olderisbetter]

My mobility scooter batteries only last just over a year no matter how I use it so if 18 months old then I doubt they will be very good even if you manage to trick them into taking a charge. The worse thing for a mobility scooter user is batteries going flat as you are left stranded so you have to ask yourself if you are happy for missus to take that risk ?

I've replaced the batteries on a scooter twice in 3 years, The batteries just don't seem to last well at all, after 12 months they seem to start having issues i think modern batteries are just a pain .

 

[CompoSimmonite]

I've been considering trying ex Toyota Prius battery packs as they are basically full of NiMh D cells !

 

[frank horton]

look on flee bay......I just bought 3 mobility scooter batts 12volt x 9 or 12 ah, gell sealed batt's for just under £40........use them on an elctric bike.......charged when performance drops or 1'ce a week.........if I get a year and 1/2 I'll be happy.........
these are a common make available on several sites so not junkers I hope.........hahaha....
good luck ......... Frank

 

[WorkshopChris]

I have had some limited luck getting life into dead SLA batteries enough for the smart chargers to work buy using a fixed 12v supply and limiting the current with a small 12v bulb in series with the battery under charge.
If you can raise the voltage enough for the smart charger to kick in, although once performance drops, whatever you do they will never fully recover and replacement is never far away.

 

[armalites]

Often smart chargers won't touch batteries that are low on voltage. One solution is to parallel them with a charged battery and then stick the charger on. That way the charger will see the right voltage and start charging. I've done this many times and it works well unless the batteries are badgered.

The biggest issue I've had is with a 6v/12v smart charger, it would sense low voltage 12v batteries as 6v volt ones. I've also found that the sealed type batteries can got well below 12v even as low as 3-4v and still charger up fine.

 

[tflnemesis]

After a couple of hours with the bench psu on one of the batteries i got it up to 9.5v but within 10 minutes of standing disconnected it was back down to 5.8v, Didn't even try the other one as it reads at 4.7v. I need to speak to FIL and see what he wants to do.

 

[Exuptoy]

This..,

Often smart chargers won't touch batteries that are low on voltage. One solution is to parallel them with a charged battery and then stick the charger on.

That does work, done it myself.

 

[Farside]

SLAs (and VRLAs) generally have a cycle life of about 300. That's easily reached in a year of mobility use, so they're probably nadgered anyway, even if they weren't left to discharge out of use - which has definitely totally nadgered them.
IF and only if, they were marginal, might it be worth to put a desulphator on them, as it sometimes works. Not worth bothering with most of the time, though.

 

[Kram]

I would sell the working battery and buy a new lifepo4 pack, if your intending to get any significant use from it, worth having decent power.

You will need to buy a proper charger, so not the cheapest option. Chargers are available for 20-30 quid but they will also do any other type.