This one is 300 watts. That's the largest size you can use by plugging into a cigarette lighter socket. Actually its too big! A maximum current that these sockets are supposed to supply is 10 amps. A 300 watt inverter will try to take double that if you actually USE all of its 300 watts and will blow a fuse in your car after a short time.. So a 3 or 4 amp wheelchair charger would be about the biggest sensible practical size to plug into it. Any bigger and you must wire the inverter directly to the car or vans battery. Its not only useful for charging your powerchair though but also for anything else that needs mains power.  12v in and mains voltage but low power power out (about 150 watts maximum is sensible from a cigar lighter socket)

But many modern chargers are "switch mode"  devices. (these are lighter and more efficient) but they will not work unless your new inverter is a "pure sine wave" device.  And whilst available they are very expensive and not common. 

Most cheap inverters are not "pure sine wave" so most modern powerchair chargers wont work like this. This one doesn't work from an inverter. It has no heavy transformer and is small, light and "switch mode"...  If yours is one of these then you are stuck.

This next blue and white charger is an older type, "heavy" charger and it uses a heavy built in transformer. It works fine with the inverter that plugs into the car or vans power socket. Although its very borderline as it tries to draw the absolute maximum from your cars cigarette lighter socket. OK occasionally but I wouldn't keep doing it.  Something will melt or burn out eventually unless your inverter is wired directly to the battery..

A problem with these inverters is that if you buy a typical cheap small one  it may or may not have enough power to run your charger. Most larger 7 amp wheelchair chargers take about 300 watts. That's too much unless connected to the battery (not plugged into the dashboard). Look at the tag on your charger it will tell you. If you need a bigger one then it will mean you either need a smaller wattage wheelchair charger (swap your 7 amp one for a 4 amp one) or a bigger inverter. Mines 290 watts shown here.  A bigger inverter can be used but it will need wiring directly to your cars battery. Better to get a cheap small 3 amp charger from EBay. So this is the untidy and often problematic way to charge your powerchair or scooter on the move as you drive.

Anyway this thing charges at 5 amps and is a multistage pulse charger that works great. It gets stupidly hot though so I fitted a bigger fan in the bottom of the case. It takes about 15 amps from your accessory socket which is actually too much.  So make sure you use GOOD cables and fittings or hard wire it to your cars battery properly. My original chairs charger an 8 amp charger so this takes a little longer to complete but puts the bulk back while you drive! Don't use it without the engine running for long because it will flatten the battery quickly.  This thing can be a life saver! I keep in in my van most of the time.  It does try to melt the plug where it plugs in the dashboard though...

There are also small 2.5 amp units available from many places online like this one  "In Car Mobile Charger 24E" http://www.4-medical-supplies.com/products/MEIMobileCharge24E.html

I just ordered one to test it. I will update this when I see how well it works. 2.5 amp is very slow with a full sized powerchair, especially as I usually use an 8 amp charger overnight and a 30 amp charger (below) for fast charging in 1 hour or so during the day.  Tested. Works great. As long as you have endless hours to wait... Typical powerchair will take 24 hours. Yawn. So almost pointless...

I think these are also available from Pride Mobility now as well. Probably rebadged as a Pride product!

But putting any power back while you drive helps maintain the lowest average daily depth of discharge and so helps keep the batteries fit for use for longer!  Contrary to what you may hear elsewhere from other self proclaimed experts this does NOT harm batteries and is in fact very beneficial for longevity.

LOOK OPPOSITE -- This info is from the 55 ah OPTIMA batteries technical information PDF file. 

It shows that charging at 30 amps is not only harmless but actually far less than they are capable of accepting.  My vans alternator for example charges them quite happily at 100 amps+ if they are pretty well discharged and that too is also acceptable. I post this because many self proclaimed powerchair "experts" will tell you otherwise...  Many other Quality battery manufactures will tell you the same as Optima do.   >>>

I wont guarantee it wont hurt other batteries so you better check with them first. Personally I would also risk it on any decent quality Gel type Deep Cycle batteries as well and do so regularly.

Although if possible it is best to see the manufacturers data first!  For e.g. the excellent Sonnenschein A500 Dryfit batteries as fitted by many manufacturers from new also specify no inrush current limit either and they are also Gel batteries.

The Hawker Odyssey batteries also can be fast charged.  You do need to make sure they don't get above typically 50 degrees centigrade or over about 14.4 volts. (14.7 for AGM) But the charger watches this doesn't happen for you. Mine don't get warm at all. Tested by shoving a probe in between them in the battery box. Yours may be different. Check at least the first time you fast charge them and then forget about it.

A cars alternator will typically charge discharged batteries at 100 amps or so. - as long as 14.4v to 14.7v is not exceeded. That's typical for many modern batteries.

These are actually the same as the ones most powerchair or scooter manufacturers use to connect the batteries under the seat. They are easy to get from caravan or leisure dealers.

Using THIS plug (Anderson plugs and sockets) fitted to my powerchair and connected directly to the battery terminals I fast charge my power wheelchair most days.