Inverter advice please

[pheasantplucker]

Adrienne's mobility scooter will need charging while we're away and now we have solar on the roof and don't need EHU much, I was wondering how to go about charging the scooter battery on the move.

Charger input is 1.8A at 240v and output is 2A at 24v DC. Will 12v source charge a 24v appliance? I assume that it will be the same as having a mains supply and the thinking is to use the charger while we drive so the van battery or hab battery should be receiving a charge from the alternator. Any thoughts on the wattage I should look for of the inverter please? I assume the calculation is 240 x 1.8 , rather than 24 x 2!

 

Thanks.

[Derek Uzzell]

That sounds a mite odd as a 2A output at 24V = 48W, while a 1.8A input at 240V = 432W.

 

If your charger does require that input, you’d need a 12V-to-240V inverter with, say, a 500W output capability.

 

In principle, you should be able to use a 12V-to-24V transformer (example here)

 

http://www.solwise.co.uk/wireless-sundries-poe-12to24v.htm

 

but that would depend on how your present 24V charger connects to the scooter’s battery.

 

(A 12VDC-to-240AC inverter would probably be more useful in any case.)

[pheasantplucker]

Thanks Stalwart. I guess to just ignore the 24v part of the equation as it really is a 12v to 240v conversion and just need sufficient oomph.

[lennyhb]

Need to establish if you current power supply has the charger circuit built in or is the charger built into the mobility scooter.

 

If the charger is in the power supply then you have no option but to go the inverter route, play safe and get a pure sine wave inverter, cheap modified sine wave inverters can be bad news for some switch mode power supplies (this is the type most commonly used nowdays).

 

If however the charger is in the scooter and the power supply is only supplying 24v Derek's suggestion of using a 12 to 24v converter is more efficient and a cheaper option.

 

Plenty on eBay 12v step up to 24v converter

[Derek Uzzell]

This 2013 thread discusses a similar question, with the mobility-scooter charger (apparently) having the same specification to that quoted above.

 

http://www.smartz.co.uk/archive/index.php/t-19652.html

 

It’s evidently possible to obtain a (not cheap) charger designed for what the Original Poster wants to do

 

http://www.mobilitysmart.cc/12v-to-24v-car-charger-for-mobility-scooters-powerchairs-1824.html

 

However, I think I’d risk using a 500W inverter like this one

 

http://www.amazon.co.uk/Ring-Automotive-500W-Powersource-Inverter/dp/B009QYNIZK

 

wired directly to the leisure-battery.

 

I notice that the issue has been discussed on this forum before

 

http://www.outandaboutlive.co.uk/forums/Motorhomes/Hints-and-Tips/Charging-mobility-scooter/30903/

 

The advantage of the inverter approach (assuming it works OK) is that you acquire a 12V-battery powered UK-norm 240V 3-pin socket into which various thing can be plugged, whereas a 12V-to-24V transformer is unlikely to be useful for anything other than charging the scooter.

[lennyhb]

I wouldn't risk a modified sine wave inverter like the one in Derek's link I would spend a bit more on a pure sine wave one, otherwise it could get expensive if it takes out your charger.

[Derek Uzzell]

Derek Uzzell - 2015-01-17 7:44 AM

 

...In principle, you should be able to use a 12V-to-24V transformer (example here)...

 

 

On reflection I realise this suggestion was a non-starter.

 

A 12V-to-24V transformer would just provide 24 volts to the (discharged) scooter battery. But what’s actually needed is an equipment designed to charge a 24V battery.

 

It seems to be commonplace for mobility scooters to be fitted with a pair of 12V gel (or AGM) batteries and I’m guessing that’s the case in this instance. So the charger may need to provide a specialised charging regimen.

 

I understand Lenny’s reservations about the inverter type, but this advert

 

http://www.careco.co.uk/item-p-ms06033/ms-ms06-mobility-scooter-accessories/in-car-inverter/

 

suggests that a basic modified sine wave inverter should be OK. (The advert’s £54.99 asking-price is exorbitant. This Ring 150W inverter is currently available from Amazon for £18.37 including P&P, and a 500W version for £40.67).

 

As the possibility exists that this type of inverter may be unsuitable for connecting to pheasantplucker’s charger, it would be sensible for him to explore this with the charger’s manufacturer and/or with a mobility-scooter specialist.

[pheasantplucker]

Thanks for the suggestions.

 

The careco inverter states that it will power the 2Amp scooter charger (separate from the scooter and looks like a laptop power supply but with a 3 pin XLR plug attached) from a cigar lighter socket yet its output is only 150W. Apparently this should power a 24v x 2A charger. with a 1.8 A at 240v mains requirement.

Now I'm confused more.

 

Another thought is that we have 2 scooters, both with 24v x 2A smart chargers, but one has a lithium battery. I haven't tried interchanging the chargers at home because I heard that lithium batteries can be hazardous under the wrong charging conditions, so an inverter looks best bet.

 

 

 

 

 

[Derek Uzzell]

I’m going to suggest (kindly) that you need to check what’s best for you with specialists in mobility scooters, rather than rely on well-meaning advice (and that definitely includes mine!) from motorhome forum members.

 

This 2009 American website deals with in-vehicle charging

 

http://www.wheelchairdriver.com/inverters-chargers.htm

 

It highlights that some mobility-scooter battery chargers may not work with an inexpensive modified sine-wave inverter and (as Lenny has warned) such chargers would need a more expensive pure sine-wave inverter instead.

 

The options seem to be

 

1: Use an inexpensive modified sine-wave inverter and hope this will be compatible with your present battery-charger. (Plenty of people appear to do this and get away with it, but the ‘won’t work’ risk is evident.)

 

2: Use a more expensive pure sine-wave inverter.

 

3: Replace your present charger with a charger that’s designed to accept a 12V DC input and produce a 24V DC output. (This is the ‘neatest’ approach unless you can think of useful alternative uses for an inverter).

 

12V-to-24V chargers vary radically in price. This one is pretty cheap

 

http://www.ebay.co.uk/itm/HIGH-QUALITY-IN-CAR-24v-2a-LEAD-ACID-GEL-MOBILITY-SCOOTER-BATTERY-CHARGER-/131099881691

 

It has an XLR plug, but you might well need to extend the cables (6 metres overall length) to power it from a dashboard-socket.

 

On-line received wisdom is that li-ion batteries need special chargers, so I strongly suggest you don’t experiment with interchanging your battery-chargers.

 

If you plan to travel carrying only the scooter with the ‘ordinary’ batteries, using the £30 e-bay charger seems a good bet. If you want the option of carrying either scooter, an inverter would be a better choice and, as you’d then have two different unknown-quantity battery-chargers in the mix, you’d be wise to opt for a pure sine-wave type.

 

As I understand it, it’s the battery-charger’s output that should influence the choice of minimum inverter output. So, as your 2A x 24V ouput = 48W, a 12V-to-240V 150W-rated inverter should be adequate. Obviously, if the charger for the li-ion battery produces a significantly higher ouput, you’d need to choose a more powerful inverter.

[pheasantplucker]

Thanks for all your latest advice Stalwart.

 

Will try the 12 v - 24 v charger. I actually considered that a while ago but found them very expensive, but this one seems good and very reasonably priced.

I'll think about an inverter too, more for when we have the lithium charger model with us.

 

Thanks to all who replied.

[PaulRead]

If however the charger is in the scooter and the power supply is only supplying 24v Derek's suggestion of using a 12 to 24v converter is more efficient and a cheaper option.