12v to 240a/c inverter

jab160 · Senior Member

12v to 240a/c inverter

Mamil · Senior Member

First, I would never use alligator clips to connect a 3000W inverter to batteries. It can be drawing up to 300 Amps at 12V and alligator clips just aren't a good enough connection at that current. For a quick 1 second burst jump starting a car in an emergency - ok, but for a constant draw of an inverter - no way! Please use properly sized cable, crimped on lugs bolted to terminals, and appropriate fuses on positive and negative circuits.

Secondly, are we talking car, campervan, or caravan here? Although all cars and most campervans use the chassis as a negative return, caravans often run an 'isolated' system where all circuits have their own negative return wire, and the DC is not connected to the chassis at all. You'd have to check if yours is a negatively earthed system or an isolated system before you use the chassis as a return path, and if so that the size of "earth strap" connection from battery negative to chassis is capable of carrying 300A safely.

Whenarewethere · Guru

I have Utilux 200 amp continuous load rating clamps on my jumper leads, they are seriously solid.

As already pointed out a 3000 watt inverter requires serious amps. A couple of times I have seen smoke coming off jumper leads. A fire & 2 cars waiting to incinerate.

You need the connectors to have enough cross sectional area of contact & the cable to have enough cross sectional area for the length of cable (resistance is the total length of both + & - ).

Mamil · Senior Member

Whenarewethere wrote:
I have Utilux 200 amp continuous load rating clamps on my jumper leads, they are seriously solid.

Hi Whenarewethere,

Apologies if I've misunderstood your post, but I've not been able to find any reference to the 200A rating of the Utilux booster clips being "continuous" and would conclude that they are only rated up to 200A for their stated application of "battery booster clips" which is by nature both temporary and of short duration. Although they are undoubtedly at the top end of battery booster clips, I still wouldn't be using them in a continuous application like connecting an inverter, for the very reasons you stated yourself of cross-sectional area of contact, as well as safety because of exposed metal surfaces and the chance of dislodging one while operating.

Whenarewethere · Guru

It was stated when I bought them 3 decades ago. I also did use them for welding, with actual welding cable.

Whenarewethere · Guru

The narrowest cross sectional area of the clamp, at the clamp end, is 58mm² per half of the clamp. I have an additional cable for better electrical connection of both halves, 116mm². Clamp pressure is 15 to 20kg.

The handle minimum cross sectional area is 78mm² per half.

The cross sectional area of a 175amp Anderson lug is 58mm²

To get the full rating you do need to use the maximum size cable which is used to dissipate heat from the actual contract area which is quite small.

Mamil · Senior Member

Whenarewethere wrote:
The narrowest cross sectional area of the clamp, at the clamp end, is 58mm² per half of the clamp. I have an additional cable for better electrical connection of both halves, 116mm². Clamp pressure is 15 to 20kg.

The handle minimum cross sectional area is 78mm² per half.

The cross sectional area of a 175amp Anderson lug is 58mm²

To get the full rating you do need to use the maximum size cable which is used to dissipate heat from the actual contract area which is quite small.

So, if I understand you correctly, what you're saying is that the wire, your Anderson plug, and clamp itself are sized correctly to carry 200A continuous current but you are suggesting to upsize the wire to act as a heat sink because you know the contact area between the teeth of the clamp and the battery terminal is too small to carry that current without creating a hot spot?

jab160 · Senior Member

So.good Anderson plugs will be the go.yes ??

jab160 · Senior Member

Shortish leads ( 500mm ) perm mounted to battery, other end Anderson plug ( lead tucked away in compartment pulled out when needed ) and Anderson plug on inverter..yes ???

-- Edited by jab160 on Saturday 18th of February 2023 07:23:55 PM

Mamil · Senior Member

jab160 wrote:
Shortish leads ( 500mm ) perm mounted to battery, other end Anderson plug ( lead tucked away in compartment pulled out when needed ) and Anderson plug on inverter..yes ???

-- Edited by jab160 on Saturday 18th of February 2023 07:23:55 PM

Yes, that would be far preferable to alligator clips, but we're talking Anderson SB350, not the little SB50, and don't disconnect the Anderson while the inverter is running or you'll get a nice DC arc flash! And you still need a fuse in there somewhere, preferably as close to the battery as possible or even on it like these MRBF fuses.

-- Edited by Mamil on Saturday 18th of February 2023 07:36:56 PM

Whenarewethere · Guru

The Anderson data the lug has a small contact area & does produce heat. The lug is derated if you use a smaller gauge wire as a smaller wire can't dissipate as much heat.

One may only have a very short run, but you still need a decent gauge for heat dissipation.

The same will apply for clamps.

Whenarewethere · Guru

Anderson SB350 data sheet:

https://www.andersonpower.com/content/dam/app/ecommerce/product-pdfs/SB350/ds-sb350.pdf

Rusty W · Veteran Member

A lot of lithium batteries would not be able to discharge that much current , will yours ? Most only discharge 100/150 amps constantly.

Cuppa · Guru

I may be missing the point here, in the debate about the continuous current capacity of clamps, but I would have thought the primary safety issue has more to do with the fact that with clamps being used in a mobile situation subject to movement & vibration, rendering them unsuitable for a a permanent connection.

As for the potential current which can pass through the cables connected to any battery (not just lithiums) it can be far higher than the 'rated' current in a short circuit situation.

-- Edited by Cuppa on Sunday 19th of February 2023 08:55:20 AM

Whenarewethere · Guru

Clamps would only be a temporary setup while stationary. A bit like if you were doing a welding job.

Whenarewethere · Guru

I can crimp or solder Anderson plugs, personally my preference is soldering. Use lead/tin solder, not tin only as it can be a pain & causes hair/whisker growth. For these seriously heavy cables you will need a gas torch or a heat gun. My Bosch heat gun goes up to 630°C, plenty enough to solder welding cable. My two 120 watt soldering irons just don't have enough heat.

Anderson 175 amp lug:

IMG_20200817_155859116 (1).jpg

TimTim · Senior Member

jab160 wrote:
Shortish leads ( 500mm ) perm mounted to battery, other end Anderson plug ( lead tucked away in compartment pulled out when needed ) and Anderson plug on inverter..yes ???

-- Edited by jab160 on Saturday 18th of February 2023 07:23:55 PM

Ok so you have a 3000W inverter. What is the wattage of the largest appliance that you are going to run off the inverter? Many people think that because you have a 3000W inverter that you are going to run it to maximum.

Personally I prefer running both + and - cables and as you could be dealing with large currents, no alligator clips and no Anderson connectors. Again there is lots of debate about alligator clips and because of the surface are of the contacts.

The issue with just plugging in an inverter is that they should also be precharged so as to avoid inrush current and sparking. There have been many an inverter and BMS destroyed by connecting large inverters up without doing this.

The size of your cables will be based on the highest current that you will draw plus a bit extra and the length from the battery to the inverter. You can use 2 x positive cables and 2 x negative cables instead of one thicker cable as the thicker they are then they are less flexible.

Your fuse, yes you need fuses, in both of your positive cables if you use and two need to be a higher rating than the highest current you plan to draw but lower than the rating of your cables. The fuse is there to protect your cables. ANL type fuses are good.

You cable lugs need to match the size of the threads of your battery connections So that you get maximum contact to the terminals.

If you have very little room like I do, then busbars are a good method for multiple connections to your batteries.

I have a 3000W inverter and have set up to run a maximum of 2400W appliances but will rarely ever draw that power.

So you need to know you maximum wattage and length of cable.

If you do need to use and anderson connector then do not use the cheap Ebay ones.

https://andersonconnect.com.au/store/index.php?main_page=index&cPath=36_39&zenid=m3hs9tj681khq9di94cl1gebp1

Like WAWT i prefer to solder mine.

Good luck

Tim

-- Edited by TimTim on Sunday 19th of February 2023 10:13:06 PM

Whenarewethere · Guru

& whether you crimp or solder add a couple of layers of heatshrink tube to stiffen up the cable out of the lug. A bit more defence against flexing the copper wire.

TimTim · Senior Member

The glue type heat shrink smile .

jegog · Senior Member

When I joined the PMG in 1957 I was taught that for a correct joint it needs to be mechanically secured and electrically connected therefore I both crimp and solder 50A Anderson plugs, soldering with my soldering iron.

Then wrap with gaffer tape. Plastic electricians and duct tapes come loose when the adhesive goes almost liquid.

jegog · Senior Member

Mamil wrote:
Whenarewethere wrote:
I have Utilux 200 amp continuous load rating clamps on my jumper leads, they are seriously solid.

Hi Whenarewethere,
Apologies if I've misunderstood your post, but I've not been able to find any reference to the 200A rating of the Utilux booster clips being "continuous" and would conclude that they are only rated up to 200A for their stated application of "battery booster clips" which is by nature both temporary and of short duration. Although they are undoubtedly at the top end of battery booster clips, I still wouldn't be using them in a continuous application like connecting an inverter, for the very reasons you stated yourself of cross-sectional area of contact, as well as safety because of exposed metal surfaces and the chance of dislodging one while operating.

Potentially half of the current will be flowing through the hinge pin or the overlap around the pin.

Of course you could loop the cable and attach it to both arms and as there is provision to do so it may be required for maximum current.

Mike Harding · Guru

jegog wrote:
When I joined the PMG in 1957 I was taught that for a correct joint it needs to be mechanically secured and electrically connected therefore I both crimp and solder 50A Anderson plugs, soldering with my soldering iron.

That is the wrong way to make a connection; either crimp or solder, not both.

If you solder the cable the crimp tool will not be able to splay the strands in order to maximise surface area contact for both electrical and mechanical integrity, also a weak point is created at the junction where the soldered and unsoldered portion of the cable meet and will make the cable likely to break at this junction.

jegog · Senior Member

Mike Harding wrote:
jegog wrote:
When I joined the PMG in 1957 I was taught that for a correct joint it needs to be mechanically secured and electrically connected therefore I both crimp and solder 50A Anderson plugs, soldering with my soldering iron.
That is the wrong way to make a connection; either crimp or solder, not both.
If you solder the cable the crimp tool will not be able to splay the strands in order to maximise surface area contact for both electrical and mechanical integrity, also a weak point is created at the junction where the soldered and unsoldered portion of the cable meet and will make the cable likely to break at this junction.

Crimp first - mechanical integrity - and then solder - electrical integrity.

Mike Harding · Guru

jegog wrote:
Mike Harding wrote:
jegog wrote:
I both crimp and solder 50A Anderson plugs, soldering with my soldering iron.
That is the wrong way to make a connection; either crimp or solder, not both.
Crimp first - mechanical integrity - and then solder - electrical integrity.

No.

A crimped joint does not need further electrical assistance.

If you crimp and then flow solder into the crimp you have no idea how well that solder has mated, it may have done next to nothing.

You now need, because of the lug mass, to apply much more heat to the joint which may well have a detrimental effect upon the cable insulation.

You have created a weak point in the cable because it can no longer flex against the crimp but rather has a very abrupt point of structural difference where the free cable meets the solder.

Crimping is the more reliable option but if that is not possible soldering is acceptable with lugs which are not subject to regular cable movement.

Crimping and soldering is simply wrong.

Bobdown · Guru

When I was at Telecom, we used to twist and solder........that was single strand copper, not sure about multi strand, but would think it would work.

That method progressed to the scotch lok connector, which was used with a crimping tool and they were grease filled to keep moisture out.

Cheers Bob

Pam_Chris · Veteran Member

A slight divergence on the subject. Have a 1500w Kings inverter (new black model) and just received from 4wd store a remote switch for Kings inverters. However, it does not work and have since found out from the net the remotes only work on the blue inverters but have been unable to find a solution. Does any one else had this problem and how did you solve it? I apologise in advance if this has been covered elsewhere.

Whenarewethere · Guru

It will be a bit difficult to make a worthwhile comment until we know your system as a whole.

Pam_Chris · Veteran Member

130amp lithium battery , 1500w Kings inverter in caravan. Mainly for charging cameras and running small 3way fridge in an emergency. All within easy capability of the set up. None of this including the coffee machine causes the unit to shut done or activate the units fans.

Mike Harding · Guru

Whenarewethere wrote:
I can crimp or solder Anderson plugs, personally my preference is soldering. Use lead/tin solder, not tin only as it can be a pain & causes hair/whisker growth. For these seriously heavy cables you will need a gas torch or a heat gun. My Bosch heat gun goes up to 630°C, plenty enough to solder welding cable. My two 120 watt soldering irons just don't have enough heat
-----

How do you find the heat gun for soldering? I've never used one for that purpose. Is it possible to heat the cable to tin it without burning the insulation and the like?

Whenarewethere · Guru

If you use welding cable.

Insulation won't melt quickly. Also the wire is so fine it heats up & cools very quickly at the exposed end.

Years ago I got 12 metres from a scrap metal merchant for $10.

The cable looks a bit rough, but the copper cross sectional area is the important bit.

(Have reconfigured with 175 amp Anderson plugs since. Can do up to 2 x 6m & also use for portable solar when needing extra distance). A bit of multitasking!