Re: Problems relocating Inverter
Posted: Mon Apr 19, 2010 8:28 am
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.
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.