Using old and new battery together, thoughts please.

[ericmark]

I have a mobility scooter, was my late mothers, wife has problem with knees, so would be nice to use some times, realised some thing wrong with batteries, so opened to see what was fitted, so 35 Ah VRLA (AGM) part no UB12350 cheapest I can find £37.92 unless I collect, so not super expensive, but not cheap either.

There was a major problem with the batteries, in they could only be charged on the scooter, however I so no real problem drilling a small hole in the battery outer case, i.e. not the battery, just case that goes around it, and fitting a plug or socket so I can charge as a 12 volt instead of both together as 24 volt.

One battery clearly faulty, casing blown up, other one at the moment on charge, may recover, or may have been damaged when other one failed. But if it does recover can I really use it?

My thoughts are if charged as 12 volt and only used as 24 volt, then maybe, but can't really charge as 24 volt as one battery will end up under charged and other over charged. I have even considered fitting 2 x 7 Ah instead of the blown 35 Ah but since as yet not charged, can't measure current, less than 40 amp as fitted with 40 amp trip.

 

[mattylad]

Chances are that the 2nd older battery is also knackered but it doesnt know it yet.
By using it with your new one you are likely going to be at reduced efficiency and it will bring your new one down quicker as it is working harder.
As hard as it is, it would IMO be better to replace them as a pair.

As for charge, if they are SLA them they need a 14v charger not a 12v one.
If your drilling the case, does this suggest that the batteries are still on the scooter, in which case just charge them using the scooter charger (which will have the correct voltage and monitoring for those batteries).

If you do them one at a time then your going to take twice as long, yet when done as a pair they will both be charged at approx the same amount together so you can use the scooter when they are at say 3/4 full but if done singly one will be full and the other flat.

 

[ericmark]

On the scooter it is charged on the tiller using a stage charger which is fast, however that means bringing the whole scooter into the house, however the scooter is designed to come to manageable bits, motor unit with rear wheels, foot board and tiller, 2 batteries, 2 arm rests, a seat, and front basket.

So sensible idea is just bring the battery packs into the house, leaving rest either in back of car or shed. However then you can't use the supplied charger as the batteries have no socket that the charger can be plugged into, so some thing like this

would be what I would be looking for, polarised caravan 12 volt socket so I can fit a plug instead of croc clips on the smart charger to charge them, and also use anything designed to be used in a caravan on the scooter, and they can easy be charged in the house or with patch lead in the caravan, can even use the batteries to keep caravan running if can't get hook up, charge from car cig lighter etc.

 

[DetlefSchmitz]

Instead of bringing the scooter into the house, had you thought that you might be able to get the electricity to the scooter? Say, an extension cable?

On the other question of one battery or two. unequal batteries will result in you reaching the same problem later when the old one dies.

I would just replace both unless totally financially not viable.

 

[ericmark]

The shed has no power, as can be seen that battery has without question had it, the scooter is a big lump to have in house, so at moment one battery being charged.

Big question is will the scooter get up the Welsh hills? It may be it simply does not have enough power, so don't want to spend too much until sure it will work on 1 in 6 hill, car has enough of a problem in high ratio, and can't even ride electric bike up the hill, I take the bike for a walk. It's easy enough to push a bike, but the mobility scooter is a big unwieldy lump to push, and I have the thought in back of mind, that it will end up unused.

The case has some spare room, and if I can use the batteries for other uses, be it power my radio, or work an inverter, then it will not be wasted, but can't really use as 24 volt, needs to be used as 12 volt for everything other than scooter, so would need to charge as 12 volt, so just thinking if using and charging as 12 volt except on scooter, do I really need two batteries? At least to test is scooter can do the hill.

 

[jj4091]

"Big question is will the scooter get up the Welsh hills? It may be it simply does not have enough power, so don't want to spend too much until sure it will work on 1 in 6 hill, car has enough of a problem in high ratio, and can't even ride electric bike up the hill, I take the bike for a walk. It's easy enough to push a bike, but the mobility scooter is a big unwieldy lump to push, and I have the thought in back of mind, that it will end up unused."

Did your late mother have trouble with it on Welsh hills perhaps if the batteries were having to be recharged more often than usual then that is why they have failed. On the other hand if it was ok for her then you probably just need new batteries

 

[ericmark]

With my late mother we lived in Shotton right on the English/Welsh border, hills were not a problem, now in Llanfair Caereinion where the hills are far steeper, however it seems there is no option, it will need to be a pair of batteries, as the one battery not showing physical damage does not seem to be recharging.

But the charging of the battery off the scooter is still under consideration, I want a method to either use the scooters own charger or a smart 12 volt charger to charge the battery off the scooter, I see no point in unloading a mobility scooter from the car just to charge the battery, all I need is to take the batteries into the house to charge.

The two batteries will connect to each other on the floor, but there is no way to plug anything in to the pair to charge them.

 

[bernardgreen]

Definately charge them as two separate batteries. Provided the supplies from the two chargers are isolated from each other ( mains to ELV by means of two isolated ELV secondary windings ) then the batteries can remain linked as a 24 volt batteries and a three pin connector used to connect the two charges to the two 12 volt batteries.

My option would be to have two constant voltage chargers set to 14.6 volts

I have 15 7.5 Ah batteries which are on continuous charge at 13.7 volts as standby power sources for various uses. The oldest of these batteries was bought in 2009 and at its last use it ran a 10 watt ( circa 1 Amp ) lamp for over 5 hours before any significant voltage drop occured.

Another one that was flattened when the lamp was left on overnight did recover after a long period ( days ) of 13.7 volt charging.

 

[conny]

My wife's scooter didn't manage the hills in Colchester zoo about 2 years ago. Don't know the gradient but it was stiff enough for the rest of us to walk up never mind the scooter! It was near the Aardvark pen, in case you know the zoo. Scooter was only 3 months old and fully charged before we went. Halfway up a hill it just died.
Checked the charging lights and there were non. Long story but I ended up pushing it back to the car and the day was cut short. Tried re-charging but nothing was happening so phoned the mobility company, (TAG I think it was), and it turns out you have to strip the battery compartment down to get to a 30A fuse located inside. A long thin cross-head screwdriver was required to take the compartment apart and I didn't have one, nor a 30A blade fuse suitable, so it was laid up for 3 days till we got it sorted. Now we carry spare fuses and the long thin screwdriver.

 

[ericmark]

There is a 120 amp fuse and 40 amp cutout so I would hope the trip would go before the fuse would blow.
It is a Sterling Saphire 2 at the time it was bought it was the largest scooter that dismantled so could be loaded into a standard car.

 

[mattylad]

Are the batteries in a removable tray when in the scooter?
It looks like they are, so if you can easily remove them then yes you can take them inside, but unless you have a separate charger it may be easier to get a socket for the existing one and (assuming they have flying leads with connectors one) a connector so you can join them both to a little knocked up circuit with overloads in and charge them using the existing charger.

 

[ericmark]

Yes the batteries remove easy, and yes have 12 volt smart charger, but the plugs on the batteries

don't help the one at bottom connects to the other battery, and plugs on right connect to scooter, meaning there is no way as it stands to connect a 12 volt charger to the battery, other than as it is at moment with case taken apart, you can see here

how the batteries fit under the seat, what it needs is some method of using a charger when off the scooter, the handles have two bolts holding them in place, was considering connecting each bolt one pos and one neg so the connection is still hidden in the bolt recess, these are 3.5 mm

want same idea but 5 mm so I can connect to battery, or some other way to make connection but not so some thing can short against the battery while being carried in car. Even a simple bolt through casing with a cover like these

but all I find is USA etc. Just basic having a senior moment trying to thing what I can use to make contact when in the house, but not cause a danger when carried in car.

 

[RF Lighting]

What about banana sockets?

 

[ericmark]

I think the banana socket could well be the answer,

these may well fit inside the handles.

 

[SimonH2]

In terms of charging off the scooter, you can connect them in parallel and charge at 12V - double the current. Whether you do 12 or 24V, you must use the correct charger or be prepared to carefully manage charging manually. Unlike wet batteries, these do not tolerate overcharging - doing so gasses off the electrolyte of which there is a very small amount and which can't be topped up. The "VR" stands for Valve Regulated - they are nominally sealed, but there is a valve which will vent gasses if cell pressure builds up. The internal chemistry is designed to promote re-combination of oxygen and hydrogen, but that can only work to a certain point.
A correctly sized multi-stage charger will bulk charge rapidly, top off at a reduced rate, and then switch to float mode to maintain full charge. Any other type of charger will either fail to fully charge, or will overcharge and destroy the batteries if you leave it on too long.

Looking at the photos it's not clear how the batteries are wired. Can you sketch the connections (showing what connectors are where in the wiring) and post photos of the connectors (there might be something off the shelf that will connect to them) ?