Inverter beeping when using high draw item - warm cable.

[VXman]

I have a 1500W (3000W peak) inverter. I use it for charging E bike and electric motorbike batteries, the wife uses a hair dryer on lower setting and we charge lap top using it. It has worked fine doing this for a couple of years.

I have just got a 1000 watt kettle and while it works the inverter beeps and shows a very low battery voltage when being used. Also the negative cable is quite warm at either end.

Could it be that the cable is not big enough or the connections not solid enough? The negative is maybe a little over 1 metre long. The positive is 1/2 metre. I have 3 90AH batteries.

 

[Figaro]

I think you're pushing it to the limit.
Can't you boil the kettle on gas ? much more efficient and won't destroy your battery

 

[jumar]

Ours bleeps when it doesn't like the load...

 

[VXman]

I think you're pushing it to the limit.
Can't you boil the kettle on gas ? much more efficient and won't destroy your battery

Yes - but 270ah and 350 watts of solar should cope with 1000 watts for a few minutes occasionally. I want to use my free electric.

 

[Just smiffy]

what gauge is the cables

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[Kannon Fodda]

So the negative cable between inverter and battery is 1/2 metre longer than the positive. There will be a greater voltage drop over the longer length assuming that the cables are the same size. So the negative cable gets warmer due to it's added load.

Are you happy the cables are adequately sized? you should have at least 35mm2 for the 1500W load, and bigger if it was running at peak.

But how good condition are your batteries, can they actually supply a combination of over 100A for your kettle load? How are they connected so power is being drawn equally from all? In theory you may have plenty of total capacity, but if the batteries are aging they may only supply a lower amperage continuously rather than serving that higher peak load. Remember too that to produce 1000W at 240V the inverter is probably drawing 1100W+ at 12V to deal with inefficiency of conversion.

 

[VXman]

So the negative cable between inverter and battery is 1/2 metre longer than the positive. There will be a greater voltage drop over the longer length assuming that the cables are the same size. So the negative cable gets warmer due to it's added load.

Are you happy the cables are adequately sized? you should have at least 35mm2 for the 1500W load, and bigger if it was running at peak.

But how good condition are your batteries, can they actually supply a combination of over 100A for your kettle load? How are they connected so power is being drawn equally from all? In theory you may have plenty of total capacity, but if the batteries are aging they may only supply a lower amperage continuously rather than serving that higher peak load. Remember too that to produce 1000W at 240V the inverter is probably drawing 1100W+ at 12V to deal with inefficiency of conversion.

3 batteries are all the same power, spec/make. Connected in parallel and under 3 years old. Seem to be ok. Yes the cable is longer for negative as one battery is under the driver's seat and the other 2 behind it. Positive and negative connected at either end of the bank so all set up correctly as far as my knowledge is correct.

As for cable size I am wondering. I used some battery cable that I had - it is chuncky and I think has 240 amp printed on it but I am not totally sure it is 35mm2. I believe that should be a diameter of 11.8mm. I perhaps should check that.

Should I have equal lengths of positive and negative even it it means one side is excessive to the required distance?

 

[Kannon Fodda]

Cables to and from the inverter don't need to be equal length, but they should be sized based on the longest cable and max load. With the bigger loads you also want to be sure you have a good standard of crimping so the current is moving equally around all of the fitting and wire. Cheap and poor crimps could be a problem creating resistance and heat.

 

[TheBig1]

As batteries age, they will have higher voltage drop under load. |The beeping is a low voltage warning. Warm cables under load indicates that they are under size or have a resistance in their connectors

 

[Just smiffy]

I have a Renogy 1000w inverter powered from two exide 85ah gels and boil my 800w kettle with no problems..

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[oldiesontour]

The Big1 has it 100% heat shows resistance...new oversized cables50mm2,new properly crimped or soldered fittings thoroughly clean connection points

 

[autorouter]

I have just got a 1000 watt kettle and while it works the inverter beeps and shows a very low battery voltage when being used. Also the negative cable is quite warm at either end.

As others have noted, heat shows resistance. But if the cable is warm at either end then that sounds like the connections are not 100%. Are they solid crimped connections, properly bolted down? If it's only warm at the ends then probably the cable itself is adequate.

Also if it's the inverter display showing very low voltage, it's worth checking the battery voltage with a meter at the same time. It may be that voltage drop in the cable contact resistances is causing the voltage drop at the inverter. Maybe re-making the connections will improve matters. I think a 1000W kettle ought to run fine on a 1500W inverter with three batteries in parallel.

 

[Lenny HB]

35mm sq will be fine for that load & cable length as autorouter says check your connections and crimps.

What type of fuse do you have inline with the inverter?

 

[oldiesontour]

Although 35mm cable will be ok for your present inverter ,for the small additional cost I would use 50mm to enable a larger inverter in the future if required the input fuse can easily be changed as required.

 

[Howard B]

Cables that came with my 1500w inverter did not look up to the job. Changed them for 35mm ones from a reputable supplier.

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[Raul]

I think you did well for so long, with loads exceeding 0.3C on lead, way to much for their intended purpose. Now they just developed a very high resistance and voltage drops it’s so much that amps increase to compensate, and taking that negative cable over the limit. Your batteries should have a C rate next to their stated capacity. If it’s 90ah at C/20, then any higher than C/20 load, they not 90ah anymore. You used a load of C/3 for over 2 years, that’s amazing, most top lead batteries are to be used at C/10, with occasional short bursts of C/5.

 

[jezport]

Try and get the black cable length down.