Inverter

[Martin24]

Just pondering what inverter I might need to charge my mobility scooter overnight and return to off grid caravanning.

 

[Sproket]

What wattage is the charger ? Also is the scooter 12v or 24v ?

Some ideas on charging

 

[emmerson]

Just pondering what inverter I might need to charge my mobility scooter overnight and return to off grid caravanning.

I use a 350w inverter hard wired into the car's cigarette lighter circuit, via a fuse.That way, the scooter (24v) is on charge all the time the car is in use.After all, you can't use car and scooter at the same time! It has worked well for us for many years, hard wired because the cheap and nasty plugs burn out quickly.
I think a 12v battery would go flat quite quickly if asked to run the inverter with running the engine.
If I remember right, I bought the inverter from Maplins for about £30.

 

[emmerson]

Of course, I should have said that I plug the scooter CHARGER into the inverter. Sorry!

 

[ProfJohnL]

I had the same problem,
I rejected the inverter method, because most cheap low powered 12v to 230Vac inverters produce a 'modified sine wave output. Modified sine wave outputs are more efficient, (chopped square waves) What you need are the less efficient pure sine wave inverters, which for the same power output are more expensive.

Chopped square waves produce unwanted harmonics on the powerlines which can upset and even damage some electronic systems - best avoided.

I got round the problem when I found a 12 to 24V dc to dc converter.

Here is the same model I found,

Ebay Item number 141436834592

However there are other models available check these out:

Ebay Item number 261840070230

 

[Martin24]

Thank you chaps, I'll do some research from the information given. Sprocket, looked on the charger and even found the charger leaflet and no mention beyond input and output figures.

 

[ProfJohnL]

Although your stated intention is the need to charge a mobility scooter, You might find other uses for a 12Vdc to 230Vac inverter, so if you do decide to get an inverter do go for a pure sine wave output model with enough power capacity to run whatever it is you are considering.

Most inverters monitor the dc input voltage and will either sound a warning or cut turn the inverter off if the voltage falls too low. This is supposed to to leave enough power in the battery to start a car, but that may depend on the car and engine size, so its best to only run an inverter when the engine is running.

I concur with Emmerson about the connection to the 12V system, the traditional cigarette lighter sockets are horrible and unreliable for long term connections. FOr units up to about 100W for longer term connections, you might consider getting an additional 7S or 13pin towing plug and using the cars towing connector, and bring the cable back into the car through the soft seal of the boot or tailgate. With power (300W and up) inverters Direct connection to the battery with short cables is best. even consider mounting the inverter in the engine compartment, and using a domestic 13A mains extension to get the power to where you want it.

Just a heads up, voltage loss along a cable is directly proportional to the current flowing in the cable. So a100W device operating at 12V dc will use about 8A of current , but at mains 230V it will use about .4A. so the losses at mains voltage are much less.

 

[Woodentop]

Just a heads up, voltage loss along a cable is directly proportional to the current flowing in the cable. So a100W device operating at 12V dc will use about 8A of current , but at mains 230V it will use about .4A. so the losses at mains voltage are much less.

I know I shouldn't argue with the Prof but....
An invertor rated 100W does not pull that level of power all the time, only when it is demanded by the load. 100W from a 12V source would actually draw 9A+ as the invertor is nothing like 100% efficient. However draw 25W and the d.c. current will be nearer 3A even if the invertor is capable of 100W.

 

[ProfJohnL]

Just a heads up, voltage loss along a cable is directly proportional to the current flowing in the cable. So a100W device operating at 12V dc will use about 8A of current , but at mains 230V it will use about .4A. so the losses at mains voltage are much less.

I know I shouldn't argue with the Prof but....
An invertor rated 100W does not pull that level of power all the time, only when it is demanded by the load. 100W from a 12V source would actually draw 9A+ as the invertor is nothing like 100% efficient. However draw 25W and the d.c. current will be nearer 3A even if the invertor is capable of 100W.

How dare you argue with me!!!!! :woohoo:

But you are correct, an inverter is in theory a power translator but my point is if you do have a big inverter you may be tempted to use it so its best to ensure the power cable arrangements will cope.

As for the power actually consumed by an inverter, again you are correct the pure sine waved units will draw more power to cover their comparative poorer efficiency compared to the modified sine wave versions.

Pl ease keep me on my toes