Technical Inverter issue

[Nenagh52]

Just took delivery of a 2500W pure sine wave inverter to run off my leisure battery.

To test it connected it to a fully charged 20Ah jump start battery power pack.
Input voltage 13.5V: output 50 Hz 235V
Connecting a 1600 watt coffee machine results in the red light and no output.
Connected a 600/1200w/1800w infra red lamp to it and it works at 600W but red light at 1200W
Am puzzled.
Thanks as always

 

[PuntoHowTo]

At 600w you’d be pulling about 50amps at 1200w you’d be pulling near 100amps

As it’s only a little 20Ah battery the internal resistance and the wires you’re using may mean it’s not able to deliver 100amps likely the power draw is dropping the voltage hence the red light coming on

 

[porta]

My 2000w pure sine used to struggle one one leisure battery but coped fine with two batteries…also the stated output is always max for short bursts, have a look at its max continuous output and that will be revealed to be much less. Some cheap inverters can only work continuously at half their maximum

 

[Nenagh52]

Thanks, I do appreciate the prompt and helpful, replies.

Wires came with it, very short.

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The actual leisure battery is an 80Ah so is that going to be the same problem?

 

[porta]

Well if peak is 5000w it should be able to cope with 1600w…maybe the safety is also on ‘draw from source’, ie it detects whether battery can cope.
On my camper, I went from 1 to 2 then four batteries, just to cope with every kitchen gadget, a chiller air blower and the daughters internet/tablet and phone charging, plus I put two solar panels on and wanted to ‘bank power’.

 

[Nenagh52]

Thanks again as always.
I gather to run the coffee machine, I need to cater for say 150 amp from the battery to the inverter. [1600A/12V=134A]
Just looking al the set up under the pax and driver seats, there are in-line 50 amp fuses on the positives, the battery leads to the pax side comes from the battery under the drivers seat and the ones to the driver side battery I haven't traced yet.
So does that mean I need to have fuses and cables capable of supplying 150 Amps from the leisure battery to the inverter?
What about upstream from the leisure battery?

 

[PuntoHowTo]

Thanks again as always.
I gather to run the coffee machine, I need to cater for say 150 amp from the battery to the inverter. [1600A/12V=134A]
Just looking al the set up under the pax and driver seats, there are in-line 50 amp fuses on the positives, the battery leads to the pax side comes from the battery under the drivers seat and the ones to the driver side battery I haven't traced yet.
So does that mean I need to have fuses and cables capable of supplying 150 Amps from the leisure battery to the inverter?
What about upstream from the leisure battery?

So you're going to need some pretty hefty batteries which can cope with 150amp continuous delivery, and you're going to need some pretty hefty wires to match. I'd recommend using multiple batteries to feed the invertor.

Then you are going to need to make sure (if its running a coffee machine) that you have enough battery capacity to make it worth while.

For example if the coffee machine is using 134Amp, and you have a 134Ah battery theoretically you'll only have enough juice to run the battery for an hour, how long are you planning on using the coffee machine, will dictate how much battery capacity you'll need. Really you'll probably need a lot more than 134Ah battery maybe 50% more to account for losses through heat in the wiring, switching losses in the inverter, heat and cold can have an impact on battery performance. (also any other things you are running like lights, or other equipment even a radio, anything running off the battery needs to be accounted for.

you might need quite a big bank of batteries to run such a power hungry coffee machine for any length of time.

 

[Communicator]

In order to achieve the battery life quoted for lead acid batteries, the recommended depth of discharge (DoD) is usually only 50%. This means that effective battery capacity is halved. Upgrading to lithium batteries, which may allow full use of rated capacity would be expensive, and I have seen quoted continuous discharge rates as low as 50A for lithium batteries.

 

[Nenagh52]

Thank you again
so an update
Fitted the 2500w inverter to the leisure battery and plugged in the coffee maker on the 1 cup setting
It pulled 1285 watts for about a minute, voltage on battery went from 14.4 to 10.7 and then the machine reduced power to 850 watts, voltage came back up to 12.2 and made the coffee.
The cables from the leisure battery to the leads on the inverter warmed a bit but at least I now know the 80Amh/ 800 Amp leisure battery will drive the coffee maker and I will upgrade the cables.
It's not coffee all day, 2 cups a day max!
Heading off in the morning for 4 nights.
In terms of the cable sizing, what size do I need to support say 134 Amps, to get from under the driver seat to under the pax seat where i have the inverter fitted for now?
Thanks for the insights re possible low Amperage draw on the Li batteries, which here in Ireland are twice what they are in France.
They might work for recharging the electric bikes.
Much to learn!

 

[PuntoHowTo]

Thank you again
so an update
Fitted the 2500w inverter to the leisure battery and plugged in the coffee maker on the 1 cup setting
It pulled 1285 watts for about a minute, voltage on battery went from 14.4 to 10.7 and then the machine reduced power to 850 watts, voltage came back up to 12.2 and made the coffee.
The cables from the leisure battery to the leads on the inverter warmed a bit but at least I now know the 80Amh/ 800 Amp leisure battery will drive the coffee maker and I will upgrade the cables.
It's not coffee all day, 2 cups a day max!
Heading off in the morning for 4 nights.
In terms of the cable sizing, what size do I need to support say 134 Amps, to get from under the driver seat to under the pax seat where i have the inverter fitted for now?
Thanks for the insights re possible low Amperage draw on the Li batteries, which here in Ireland are twice what they are in France.
They might work for recharging the electric bikes.
Much to learn!

DC Cable Size Calculator | Fabhabs

Easy calculator to size DC cables based on their length, current, and citcuit voltage. Ideal for 12V and 24V systems such as campers, van conversions, and solar projects. Need to know how thick a cable needs to be for a solar panel, fridge, battery, or motor? Use this calculator to find out.

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Fill in all the details and it will spit out what sized cable you should be using. Try and make the cable run as short as possible and the battery to ground cable as well as the inverters ground cable as short as possible and use the body of the van to carry the return current as much as possible.

 

[Nenagh52]

DC Cable Size Calculator | Fabhabs

Easy calculator to size DC cables based on their length, current, and citcuit voltage. Ideal for 12V and 24V systems such as campers, van conversions, and solar projects. Need to know how thick a cable needs to be for a solar panel, fridge, battery, or motor? Use this calculator to find out.

www.fabhabs.com

Fill in all the details and it will spit out what sized cable you should be using. Try and make the cable run as short as possible and the battery to ground cable as well as the inverters ground cable as short as possible and use the body of the van to carry the return current as much as possible.

Thanks, on the subject of grounding, where should I earth the AC side?

 

[PuntoHowTo]

Thanks, on the subject of grounding, where should I earth the AC side?

I'm not sure you do earth the AC side of the inverter? you'd need to see what the instructions say about that?

 

[Nenagh52]

I'm not sure you do earth the AC side of the inverter? you'd need to see what the instructions say about that?

Just read the spec on both inverters, I have a 1500w one as well, neither mention it but they are pretty basic

 

[John Dough]

Just took delivery of a 2500W pure sine wave inverter to run off my leisure battery.

To test it connected it to a fully charged 20Ah jump start battery power pack.
Input voltage 13.5V: output 50 Hz 235V
Connecting a 1600 watt coffee machine results in the red light and no output.
Connected a 600/1200w/1800w infra red lamp to it and it works at 600W but red light at 1200W
Am puzzled.
Thanks as always

You need a inverter 3 times the power you want for 1600watts 3500 to 4000watt inverter.

 

[John Dough]

Just read the spec on both inverters, I have a 1500w one as well, neither mention it but they are pretty basic

There should be a separate earth connection on the inverter body . To use any high power item e.g. microwave 800 watt you need pure sine wave inverter to supply 3 to 4 times the 800 watts x 4 = 3200watts needed. Also don't forget to upgrade the fuse from the leisure batteries to cater for the full load. To avoid damaging lead batteries never discharge below 50% with lithium its 20% or you will destroy them.

 

[John Dough]

You need a inverter 3 times the power you want for 1600watts 3500 to 4000watt inverter.

20 ah battery is useless you need 100 ah at least.

 

[Anthony489]

Hi

An inverter with a constant load on its "mains" output will draw a constant power from its DC supply. Also, the inverter will never be 100% efficient. If you assume typical 95% efficiency and a 1600 watt load it will draw 1684 Watts from the DC (the extra 84 watts is wasted as heat ). The lower the input voltage, the more current must be drawn to maintain the same power. So for the example above that's 117 Amps at 14.4 volts, 135 Amps at 12.5 Volts and a stonking 159 Amps at 10.6 Volts. By then it's game over for the battery if the inverter's under-voltage protection hasn't already tripped.

Even tiny fractions of a volt more on the supply side will help, so short thick cables (both "flow" and "return") with clean tight connections and heavy duty joints to minimise voltage loss are crucial. Aim for no more than about 3% total voltage drop, i.e. 1.5% for flow and 1.5% for return. Although you could use the vehicle body/chassis as part of the return circuit, it introduces two extra joints. For the short distance you have in mind I think you would be better off simply running a return cable directly back to the battery negative terminal. If you fit a fuse in line, ensure it is designed for high currents e.g. 200 Amps.

My feeling is that a fully charged 80Ah leisure battery in good condition should be able to supply enough energy for a 10 minute brew (280 Watt-Hours), but there are too many variables to be certain - you will just have to experiment.

I don't know if this is an option for you, but if you can run the engine to put some charging current into the leisure battery circuit whilst brewing up, it will provide part of the inverter's current needs. This will reduce the current needed from the battery and prolong the time before the voltage dips too low. Think of it as emptying the bath whilst the taps are still on !

Regarding earthing one side of the inverter's mains output, this should be unnecessary as it is an isolated source. Your coffee machine is very likely to be double insulated and does not have or need an earth connection. Mains earthing won't have any bearing on the operation of the DC side.