Problem with large resistive loads or appliances on Solar inverter & storage batteries

Solar Questions and Comments
1

Generally it is discouraged to use resitive load appliances in solar system having inverter /storage batteries.

Can some one explain the reason and a solution or way-around to use these appliances (Electric water geasers,microwave,Electric ovens ,electric heaters etc .

2

Hi there

Not really my area, but I believe it’s because they require a large amount of power in a short space of time. I think it’s the surge rating. You can have a system designed that allows you to use these things, it will just cost a lot more. It’s actually quite surprising how much power a toaster and electric kettle need to run.

To be clear, this is only an issue with an off grid system. With a grid tied system you can still just pull power from the grid as required of course.

Cheers
Marty

1 Like
3

Large resistive loads are not a problem during normal use. I think what you are confused about is the ‘backup power rating’ of regular batteries and hybrid inverters. During normal use (no blackout), the system can be used to power most appliances (resistive or inductive) and the grid is simply used if the load is too high.

For example, a 4.5kW hot water system can draw 3kW from a hybrid inverter & battery and 1.5kW from the grid. However, when there is a blackout most hybrid inverters can only BACKUP essential loads like lighting and one or two power circuits. See the grey column in the chart below.

Only larger off-grid inverters have the ability to power large resistive or inductive loads all the time.

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4

Thanks Marty.

Your point of starting surge in short span of time may be the reason.Especially it can be bad for the battery to have a big surge.

This link i found on the net can be useful

5

Got some info on surge

  • Surge: All off grid solar inverters have a continuous rating and a surge rating. The surge rating is usually specified at so many watts for so many seconds. This means that the inverter will handle an overload of that many watts for a short period of time. This surge capacity will vary considerably between inverters, and different types of inverters, and even within the same brand. It may range from as little as 20% to as much s 300%. Generally, a 3 to 15-second surge rating is enough to cover 99% of all appliances – the motor in a pump may actually surge for only 1/2 second or so.