How many watts can I power from the 12v cigarette lighter socket in my car please?

expeditionist · Nov 7, 2011

Re: How many watts can I power from the 12v cigarette lighter socket in my car please

OK, thanks guys, you've been very helpful.

I've been told that my local scrapyard removes batteries from cars before they're scrapped and they sell the ones that they test as good for a tenner and it'd be easy to buy a much bigger battery, so I'm looking at upgrading the van's battery maybe as well, or perhaps fitting a second battery in the van somehow, but either way, I need to source a decent pure sine inverter over 500W/600W now, off eBay I guess, and then get it hard wired by persuading a mate to help me.

Leave it with me then, thanks again for all your advice, regards, expeditionist

benji · Nov 7, 2011

Re: How many watts can I power from the 12v cigarette lighter socket in my car please

mines got a plastic cover on it and its states 55w max

Deleted member 26818 · Nov 7, 2011

Re: How many watts can I power from the 12v cigarette lighter socket in my car please

I wouldn't be too bothered about obtaining a larger Amp hour battery, unless you intend using the inverter without the engine running.
I have even on the odd occasion found that having a too powerful battery, causes problems with starting. The starter moter spins too quickly for it to engage with the fly wheel.
What I would suggest, is that you search for a camper van forum, and ask their advice.
I'm fairly certain that there are set ups which will allow the charging system to charge two batteries, the second battery being charged only when the main is full.
These set us can also be arranged so that the main battery will not be discharged when using ancillary equipment, so there is always enough to start the engine.
You may even obtain advice on places that will make adaptions to your vehicle at a reasonable cost.

steve-the-hat · Nov 7, 2011

Re: How many watts can I power from the 12v cigarette lighter socket in my car please

spinlondon said:
I'm fairly certain that there are set ups which will allow the charging system to charge two batteries, the second battery being charged only when the main is full.
These set us can also be arranged so that the main battery will not be discharged when using ancillary equipment, so there is always enough to start the engine.
You may even obtain advice on places that will make adaptions to your vehicle at a reasonable cost.

This is good advice.

There are essentially two ways of charging a second battery: an automatic split charge relay or a diode splitter. Caravans, motorhomes, horseboxes and canal boats use these, so a quick search should find you a local firm to install one for you.

If you do fit a second battery then secure it in a proper battery box. There is a lot of stored energy, weight and acid in a battery - you don't want it to move when you brake hard!

expeditionist · Jan 30, 2013

Re: How many watts can I power from the 12v cigarette lighter socket in my car please

Bump...

Hi guys

Sorry to revive this post after so long but I'd appreciate some further advice please as I have a new problem with my install.

I had an auto electrician hard wire a 600w soft start inverter to my van's battery and I bought a new battery because the old one was failing and I've been using that inverter to run my mobility scooter's charger every time I start the van for over a year with no problems.

Today I've had the power cutting out on the inverter and the inverter's alarm going off for about 10 seconds every 2 minutes or so. The inverter's manual says that's either due to low input voltage or overload but I'm completely confused. I have however tested some other stuff powered off the inverter. It'll run something rated at 120 watts without problem, but the problem occurs with 3 different products between 270 watts and 522 watts so it's not what I'm running that's faulty.

I'd like to know whether or not to buy a new inverter or moan at the guys who sold me the new battery?

Any ideas please? Thanks.

telectrix · Jan 30, 2013

Re: How many watts can I power from the 12v cigarette lighter socket in my car please

first get the battery tested at somewhere like hi-Q. it could be an alternator fault, not charging the battery fully. or, as you say, could be that the inverter is goosed,

expeditionist · Jan 31, 2013

Re: How many watts can I power from the 12v cigarette lighter socket in my car please

Thanks telectrix, I went to the garage who last serviced my van and they were kind enough to give me some free time checking out both the battery and the inverter with a volt meter under various loads, the tests pointed to the inverter cutting out while the voltage entering it was good and it was only powering 270 watts and it was then discovered that the inverter is overheating because the fan isn't spinning.

Glad I took you're advice rather than going and moaning at the guys who sold me the battery but it's so annoying that the inverter should pack in after 13 months and just out of warranty!

KFH · Jan 31, 2013

Re: How many watts can I power from the 12v cigarette lighter socket in my car please

Have a look at some consumer advice web sites. I am sure that under EU regulations and UK law retailers/suppliers have to give a 2 year g'tee on stuff.

Robotstar5 · Jan 31, 2013

Re: How many watts can I power from the 12v cigarette lighter socket in my car please

As the inverter is out of warranty, might as well take it apart to find out if the fan has failed, if so a look round ebay etc will probably find a replacement. If the fan is OK, you could wire it direct to a 12 volt supply (assuming fan is 12 volt!) via a switch and fuse, just have to remember to turn it on and off.

expeditionist · Feb 1, 2013

Re: How many watts can I power from the 12v cigarette lighter socket in my car please

Thanks, I'm not having much luck getting a response from the seller as yet, nor from Mercury, the manufacturer.

I looked up that 2 year minimum warranty rule, it's not that simple unfortunately, see here: Martin Lewis' Blog? | The EU ?goods must last a minimum two years? rule is a myth

The inverter I bought is on sale for 2 and a half times the price of similar inverters - see here: http://www.amazon.co.uk/Soft-Start-...4W/ref=sr_1_10?ie=UTF8&qid=1359648099&sr=8-10
but I wonder now what the point was in buying from the supposed market leader when similar ones are on sale for £30-£40.

I may take it apart and have a fiddle with it, but if no luck I'll just buy one from Maypole next time, I have some of their other products and they seem to work well.

telectrix · Feb 1, 2013

Re: How many watts can I power from the 12v cigarette lighter socket in my car please

maplins sometimes have offers on. i bought a 600watt inverter for £19.99 on offer.