Problems relocating Inverter

[dave_aber]

OK.

500W inverter - presumably the 500W is the output rating. So, allowing for some inefficiency, you could be drawing 50A on the 12v side. Dreamwarrior mentioned above that he had melted a similar fuse holder using a 750W inverter. I'd be for using 50 or 60A fuses, and be prepared to blow them occasionally rather than melt the wiring / fuses. What will you be powering with the inverter?

A separate earth is definitely a good idea, especially with a device drawing a high current. Remember that the 50A current is drawn around the entire loop - from battery +ve, through the fuse, cable, inverter, and along the earth path back to the battery -ve. So, your earth cable must be the same size as the feed cable. If you use the car body, you must make sure that all the joins along the way can handle 50A, hence the reason that a specific earth cable is a good idea.

You'll never crimp those crimp terminals without the right tool. You would need one of these. Solder them instead. You'll need a blow torch or a really big soldering iron (like a plumber's one) to solder them properly. Don't even think about crimping them with a cheapy crimping tool - if a wire falls out of the back of the crimp, and the end is live, then you'll blow a fuse or have a fire.

That 3mm² flat cable does look like domestic, but it's a stranded cable so it will be OK. You need to fuse it at each source of supply, so for a battery charging circuit which has a charger at one end and a battery at the other end you need 2 fuses. Your PMS3H is feeding both batteries (presumably, one at a time via the car/van switch?), so you will need 4 fuses in total. That cable is 27.5A rated, so to protect it you need a fuse which will blow at a lower figure than 27.5A. 20A would seem sensible.

Yellow crimps are designed for wire sizes from 2.63mm² to 6.64mm², so they will be OK for your 3mm² cable.

For the Leisure battery end of the PMS3H cable, you can in theory use a yellow 5mm ring added to the strip fuse holder. What you need to consider here is that the strip fuse is 50A, so won't protect your 27.5A cable - you'll still need a 20A fuse in this line, as close to the L/B as practical. Also, the cable entry point and the stud in the strip fuse holder doesn't leave much room for a second cable to be spliced in. One option here would be to solder in a section of red 3mm² core along with your 10mm² cable (to the inverter) into the main ring crimp - about 2-3" long, and then add a 20A fuse holder in line, then the flat cable to the PMS3H. As this line will have its own 20A fuse, it can go in either end of the 50A strip fuse.

Either that or buy a one-off large yellow ring crimp from halfrauds etc.

If you are doing a lot of wiring and working with crimps - alarm, central locking, etc, etc, then the cheapo crimping tools can be a really bad idea. They allow you to crimp the terminals down, but only over a narrow area, and can 'miss the spot' leading to crimps that look OK, and conduct OK, but fall off over time. It may be worth the investment to get something like this. The toolbox shop do one in a kit too, with various coloured crimps which isn't a bad price.

[thedogsbollox]

Thankyou very much for taking the time to write that reply. I feel a lot more assured now.

[dreamwarrioruk]

just a point to note on our inverter (1000w) i used 32mm tails from the unit to the lb <1m and these get warm when the inverters on full chatter. I did have a fuse withing the live side leading to the inverter but i couldnt find a non plastic fuse holder that would take 32mm tails. I tried another and that one melted also.So that meant that the fuse protecting the inverter was on the splitcharge circuit. this one melted as the grill took too much for the lb to keep up with. I know its not an ideal situation to be in and we dont use the george grill on the inverter now. it shows how carefull youve got to be.
it depends where your placing the inverter tony to what size cable to use from the lb. like dave said it depends on what your gonna use it for, anything to do with heating will put a severe strain on any cabling you use.

regards to the twin cabling. although it looks to be domestic the picture is deceiving as i have used this company before unless they changed cables they use it is suitable. im assuming tony that this is purely to charge the batteries from the pms unit. as dave said just make sure that you bang enough fuses in to protect the wiring.

deffo get the proper crimping tool. i use one when doing 240v electrics at work, if needed to extend wires into a new fuseboard need to make sure you get a good crimp there.

[thedogsbollox]

Thanks for that. I am not planning on using the inverter for anything. It was fitted to my bongo and I wanted to move it to a more sensible spot and attach it to the LB. Would like to keep it just for emergencies just in case. But if I ever do need it I want the peace of mind that it won't dissolve on first use.

[dave_aber]

I've been having the "do I need an inverter?" debate with myself, and on a post in the forum.

Consensus was that the only practical use was to provide 240v to low-current devices which don't have readily available 12v/car equivalents. Examples are camera battery chargers etc where the 12v version was overly expensive. I may carry one I can use clipped on to the battery for emergencies (whilst stationary!). I'm planning a couple of mains outlets in the back for use when on hook-up for bigger loads, like hairdryers, kettles, george foreman grills, etc.

The good news is that once you have the inverter sorted with whatever wiring you need to keep it safe, the 240v output wiring will be carrying a current about 1/20th of the current on the 12v side, so it all becomes smaller and easier.

[dreamwarrioruk]

i used to have a 2000w one in the transit van which i used on sites where there wasnt electric supplied to run power drills etc, easier than lugging a generator around also was handy for charing up the batteries. mainly use the one in the bongo for charging batteries and running laptop or stuff like that. after the mess with the fuses george is sort of banished until were on hook up.

[thedogsbollox]

The Inverter itself is this one
http://www.halfords.com/webapp/wcs/stor ... 65727#dtab
There is an on off switch next to the plug socket.
Does this unit draw power from the LB all the time, that is when switched off?
Will it draw more power when the switch is on with nothing plugged into it?

[dave_aber]

Difficult to say. If it's the 240v side that's switched, then yes, it will draw a small current in the 12v circuit all the time. from the picture on the website, it's entirely possible that the switch is in the 240v, or 12v, or some internal control circuit (5v?).

Do you have a meter which can measure amps?

[thedogsbollox]

Difficult to say. If it's the 240v side that's switched, then yes, it will draw a small current in the 12v circuit all the time. from the picture on the website, it's entirely possible that the switch is in the 240v, or 12v, or some internal control circuit (5v?).

Do you have a meter which can measure amps?

Yes i do. Is it a case of measuring across the battery terminals?
Switch on the switch and see if it goes up?

[dave_aber]

NNNNNNNNNNNNOOOOOOOOOOOOOO !!!!!!!!!!!!!!!!!!!!!!

[dave_aber]

Voltmeters have a very high resistance - so you can stick them across a battery and they son't explode.

Ammeters have a very low resistance. If you set up for amps and stick the probes across the battery, you'll measure how much current your battery can deliver into a short circuit - and blow up your meter.

Wire it all up, and connect the ammeter in circuit between the L/B +ve terminal and the red cable to the inverter. You'll be limited to 5 or 10 amps through the meter - if you exceed this an internal fuse will blow. Don't plug anything into the inverter, just measure the current with the switch on and off.

[thedogsbollox]

OK so, as i see it now,
get everything wired up as normal but remove the red inverter lead from the LB+ terminal. Use the ammeter to bridge the gap between terminal and lead.
Switch the inverter on and off to see the readings. Dont plug anything in as this will draw too much current and blow the meter.

hows that?

Voltmeters have a very high resistance - so you can stick them across a battery and they son't explode.

Ammeters have a very low resistance. If you set up for amps and stick the probes across the battery, you'll measure how much current your battery can deliver into a short circuit - and blow up your meter.

Wire it all up, and connect the ammeter in circuit between the L/B +ve terminal and the red cable to the inverter. You'll be limited to 5 or 10 amps through the meter - if you exceed this an internal fuse will blow. Don't plug anything into the inverter, just measure the current with the switch on and off.

[dave_aber]

Spot on.

What current rating will your meter read? (Usually written on the meter, next to the connection for the red probe in current mode)

[thedogsbollox]

Had a bit of a tidy up today and all me leccy gear is in a big box. Will dig it out when i start my next job
Thanks for the help Dave.

Spot on.

What current rating will your meter read? (Usually written on the meter, next to the connection for the red probe in current mode)

[thedogsbollox]

Job all finished today. Thankyou all for your help and support.
Used the meter and it only draws power when switched on so that'll be why it killed the main battery when it was hooked up to that.
Tomorrow i start the fuel sender.......