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Battery power on display.

Hi, I'm not sure if I have a problem or not and will try to explain the best that I can.
My shoreline electric is plugged in and working. On the battery and power info display unit the small AC in and AC out lights are both on as is the charge and inverter bypass lights. The COM light is flashing. Usually no matter what I'm using on the mains power like kettle or washing machine the batteries always show 104% charged and 13.8v. The last few days when boiling the kettle or running the washing machine the power display will drop as low as 90% charged. I have a Powermaster 1500w Pure Sine Wave Inverter/charger and worried I may have a problem. The 3 domestic batteries are 12 months old and always have shown 104% charged and 13.8v has mentioned earlier. More info if you require it, thanks in advance.

Asked by: Trevor Smith  | 6.33pm, Tuesday 14 October


WW says:

It does not sound as though you have a problem; if your shore power connection is restricted it could be that your washing machine/kettle has been using all the available shore power. This would mean that there is not any power left for the battery charger and it has shut down. Thus the 12V loads such as lights etc, have been taking power from the battery and the battery charger only recharges the batteries after the AC load has been removed.
Powermaster inverter battery cable terminals are often the type with screws that squash the cables. If you have these it would be a good idea to check that they are still tight as loose connections create heat and can lead to fire. It would also be a good opportunity to check the electrolyte levels in the batteries and top up if required; a job that is often neglected and will extend the battery life.

Rupert Smedley  | 11.49AM, Wednesday 15 October


Readers say:

A short time after I posted above the LCD display was showing 96% - 14.3v and 2 hours to fully charged. Now a few hours later it shows 104% and fully charged with 14.4v.

Trevor Smith  | 10.21PM, Tuesday 14 October

Thank you Mr Smedley for putting my mind at rest. I've just returned home from work and running the washing machine and the battery LCD info is showing 105% and 14.5 v.

Trevor Smith  | 5.08PM, Wednesday 15 October

The battery voltages look very healthy, but it might be worth checking that the shunt for the current monitor is connected correctly, so that the current to and from the inverter/charger is passing through the shunt and being recorded correctly. When I fitted a battery monitor (the NASA Marine one) I found that the negative return for the inverter was not connected to the same end of the battery bank as the alternator and the other 12V circuits, also the bilge pump return was taken to a third connection point, just because it was nearer! When connecting a current shunt, ALL the battery current must pass through it, otherwise it will give misleading charge percentages. I had to shorten or extend several large cables to get this right.

Robert Wood  | 11.43AM, Wednesday 19 November

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