First of all, I would check with the manufacturer of the chair. Just because it looks like an automotive style gel battery does not mean it can be treated exactly like one. But "assuming" these are in fact automotive gel batteries you could charge them one at a time, without even removing them from the chair!

To do this simply connect your charger to a single battery directly, and no you would not even have to disconnect anything. If you wanted to, you could pick up a second charger, and charge the second battery simultaneously, once again without disconnecting it. Each battery, and charger would form it's own circuit. The thing that stands out here, and needs to be known is the CCA of the batteries, and the reserve power rating. Plus if they happen to not be automotive batteries, they may be designed to charge at a different voltage than a true automotive battery. Your charger likely puts out a pretty high noise level on it's output. This is AC ripple that floats on the DC voltage, and would be visible with an occiliscope. The manufacturer of the chair will be able to tell you if high AC ripple could be a problem for the controls on your chair. If so, then you may need to open the battery circuit at one of the posts. I do have reservations about whether your charger is strong enough to recharge the batteries in parrallel. IMO yes that would work, but if you have a connection issue, you could accidently charge only one battery.

Important details need to be known when trying this.
What is the current draw of the chair? How many minutes a day does it operate at that level? Example. If the chair draws 10 amps of current, and it runs for 60 minutes (one hour), then you have pulled ten amp/hrs from the batteries and thats what needs to go back in to charge them up. So if your chargers run at 10 amps for ten minutes, and then it drops down to one amp, it would still take some 8 hrs to charge your batteries back up fully. The manufacturer of the chair would have taken this into consideration, and would spec out a charger that will restore the chair close to full charge in a specific amount of time. Trouble can come from both undercharging, or overcharging of a battery. The automotive charger could operate at too high of a voltage, and over time damage the batteries. Or it could be too low and overtime, allow the batteries to run at partial charge, which again isn't good for them, nor the chair motors. So be carefull, and check the specs before you try and work around this system. Thats the best I can do for you with this subject without trying to write an entire class about batteries.... VBG...

A quick search says the Jazzy 1420 uses 2 AGM batteries, available either 55 or 75 AH. 6+ MPH, .. Fast ! 25 mile max range ... Far !

So a regular automotive type charger will work fine, but you need to use the 10 amp setting on your charger. Charge them both about equal time, you want them both to have about as close as possible to the same level of charge.
I certainly would think it should be ok for temporary use.

This would only be temporary use till the service people can come pick up my chair and drop off a loaner.
Without my chair I am almost completely housebound.

My chair normally will charge completely overnight.
And some times I get as much as 2 days on a single charge.
Usually I get one day on a single charge.
Batteries go down faster if I spend more time off the pavement.

I'll call Monday and see about getting my chair fixed.
Last time it took two weeks for them to come pick it up.

I checked all the obvious fuses.
I'll have to look for any hidden ones.
I really hate sending my chair in for service.

Thanks.

Pooh Bear

Charging two gel cell batteries in parallel is an iffy proposition. It may work, and it may not. This issue is plagued with problems. For example, suppose that one of the batreries has a shorted cell; Then it becomes a 10 battery. Connecting a 10 volt battery in parallel with the 12 volt battery will allow the the 12 volt cell discharge into the 10 volt battery until both batteries arrive at the same voltage. The resulting current at the moment of hookup could be bad.

The 10 battery will hold back the 12 volt during charging and the 10 volt one will over charge. Its a mismatch and not good.

Parrallel charing only works when both batteries are reasonably matched in volts.

The best bet is to charge the batteries separately, however, I see your pain in doing this. Also, there's no guarantee that both batteries would arrive at the same state of charge, and during use, one could become discharged before the other one.

Now here's a thought. Some truck systems use 24 volt batteries (or two 12 volt batteries in series). If you could get your hands on a 24 volt battery charger, you could charge both batteries in series.

I assume that gell cells were specified for safety reasons, e.g., to prevent spillage of the electrolyte.

AGM are basically regular wet cell batteries.
Absorbed Glass Matt.
Fluid is sort of held in a sponge mat.

Here is a link that might be useful: BatteryFAQ.org

You do not need a 24 volt charger to charge two 12volt batteries hooked in sucsecion.We have the same set up on tractors and combines.You just hook to one positive and ground it and it charges both batteries.But if you had two chargers it would solve any questionable problems.

Well, this problem seems to be solved.
Called the service place today and
they will be picking up my chair in the morning
and dropping off a loaner to use.
So I want have to mess with charging the batteries myself.

Thanks.

Pooh Bear