12v power inverter

[davetherave1979]

Hi guys i have just fitted my 12 1000w inverter in my van that I have had for a year need to now what size cable to use to feed the mains input side from the 12v battery to the inverter its a 1kw inverter not sure what to use could I use 10mm single or do i need bigger automobile cable dont want to set fire to the van thanks

 

[telectrix]

I=P/V, therefore I=1000/12 = 83A so 16mm. however. your battery would drain in less than an hour at this rate. it may be a 1000watt inverter, but what actual load will you be drawing. if it's only , say 200watt, then you can use a smaller casble on the input side but fuse accordingly.

 

[davetherave1979]

We will be running battery chargers a 150w halogen lamp and the oad drill if need be it will only be used now and then mostly be using the 150w light when looking in the van for stuff in the dark but not for a long time.

 

[telectrix]

OK, so assume a load of 200watts, then at 12volts I= 200/12 = 16.66A. then you can use anything 2.5mm or over. i suggest using 6mm and fit a fuse 20A. this will give you an output wattage of 240watts. ( assuming the inverter is 100% efficient).

 

[davetherave1979]

Thanks

 

[steve-the-hat]

Hi guys i have just fitted my 12 1000w inverter in my van that I have had for a year need to now what size cable to use to feed the mains input side from the 12v battery to the inverter its a 1kw inverter not sure what to use could I use 10mm single or do i need bigger automobile cable dont want to set fire to the van thanks

OK there are several things to consider here.

The inverter draws about 83.5 A at 12 VDC when producing 1000 W. So 10 mm cable is not suitable.

You should be designing for a volt drop of < 0.5 V, so how far is the inverter from the battery?

16 mm cable is suitable if the circuit length < 5.7m, 25 mm cable will do for up to 8.5 m.

Use multistranded flexible cable as anything else will vibrate loose. You should also fit an isolator switch for the supply in case the magic smoke starts leaking. You may also want to add a split charge relay so the inverter can only be used when the engine is running. You could run the van battery flat in less than an hour on full load.

 

[telectrix]

OK there are several things to consider here.

The inverter draws about 83.5 A at 12 VDC when producing 1000 W. So 10 mm cable is not suitable.

You should be designing for a volt drop of < 0.5 V, so how far is the inverter from the battery?

16 mm cable is suitable if the circuit length < 5.7m, 25 mm cable will do for up to 8.5 m.

Use multistranded flexible cable as anything else will vibrate loose. You should also fit an isolator switch for the supply in case the magic smoke starts leaking. You may also want to add a split charge relay so the inverter can only be used when the engine is running. You could run the van battery flat in less than an hour on full load.

that's basically what i posted. but it seems he only wants to load the inverter at around 200watts.

 

[steve-the-hat]

Quite right telectrix, I suppose I have seen too many of these things badly installed on boats.

Dave only intends to load the inverter to about 200 W at the moment, but IME the loads do tend to get steadily increased. You know how it happens, the second lamp... the drill charger... the hot air gun... the kettle...

It's a bit like people who install a 13 A s/o on a bit of 0.75 mm2 2 core flex, as they only intend to run a table lamp from it.

The inverter can draw 83.5 A (and probably a bit more for a short time) so I would cable it accordingly.

 

[Deleted member 26818]

I would most definately use Tri rated or fine stranded cable for this.

 

[telectrix]

The inverter can draw 83.5 A (and probably a bit more for a short time) so I would cable it accordingly.

that's why i recommended a 20A fuse on the battery side. as it's the op's own van, i would imagine he would not seriously increase the load without considering the loading on the input ( 12v) side.

 

[steve-the-hat]

OK we'll agree to disagree on this one. Your solution does the job. My solution may be a bit over the top in this case.

 

[telectrix]

not disagreeing with you, steve. obviously if the inverter were to be used to it's max. then he would need some serious cable on the 12v side. many don't realise the massive current required at such a low voltage to produce the wattage. on boats, i can see the need for this, kettles, heaters etc., mate of mine installed a 2.7KVA inverter on a canal barge recently, and was surprised to see what cable he needed. fully loaded, that beastie would pull 250A!!! serious number of heavy duty batteries as well.

 

[steve-the-hat]

No problem.

BTW that 2.7 kVA inverter's a baby compared to some of them. I regularly fit 3 kVA and 5 kVA ones, even 8 kVA on occasion. Yes 95 mm2 and 120 mm2 cable and 400A fuses are not unusual.

Wrongly installed, they can also do this to batteries - hence my caution.

 

[telectrix]

ahhhh. all it's little amp-hours have escaped into the sunset.

 

[steve-the-hat]

The call out message for that one said:
"Strange noise coming from the batteries and TV doesn't work. Owner wired boat himself. Slight burning smell."

 

[adamwilliams]

Yeah its very important now that you have installed the inverter now you should change that wiring too.

 

[lsdweb]

An alternative to your 150w flood would be to use LED strips (12v). Cheap as chips from China and pretty effective - here are 3 of them in my box van.