Electrics worry- things behaving unusually

[Witchword]

Normally, when on shoreline, my battery monitor tells me that the batteries are full (it displays 104%, usually). Today it registered 90% and now 85%. Something somewhere is using battery power instead of shore line, is it? Or is the Numax battery charger ("plug in and forget about it") not working properly? Or something else?

[Paul C]

What kind of battery monitor is it?

[Witchword]

Digital, that's about all I know. It has various settings including volts/amps, and %age/ time to discharge.

[Chewbacka]

Do you have a DC clamp meter? If so stick it on a battery cable and see if power is going in or out of the batteries when the charger is on.

You said the battery meter can display amps. Select amps, does it show charging or discharging? If discharging, turn the charger on and off and see by how much the current changes.

[Tony Brooks]

Have you checked that the shorelione is actually supplying? If you have an inverter that syncs to the mains turned on and the shoreline has failed then the inverter might be feeding the charger from the batteries.

 

Next thought - could a battery cell be shorting?

Edited June 3, 2016 by Tony Brooks

[Rob-M]

Have you got any credit in your shore power...?

[Witchword]

Yes there is credit in there. When I ran out, the fridge went off.

 

The batteries are new. What does it mean if one is shorting?

 

It is back up to 90% or 12.8V now. I just don't like things changing for no apparent reason, it makes me nervous!

Edited June 3, 2016 by Witchword

[Paul C]

I was hoping for more detail eg a make/model. To see if its either one of these battery monitors which simply "convert" a scale of voltage into battery condition (which is only really indicitave); an amp-hour counter (slightly better but not much, and likely to be just as misleading) or something else eg Smartgauge.

 

But anyway, it doesn't really matter because all battery monitors which attempt to show battery state of charge as a % have some or other kind of flaw, its a difficult thing to "simply" show. The voltage readings are much more useful. Without getting too complicated, it does sound like the shoreline tripped out for a period but is now back. The battery voltage will clearly show if the batteries are being charged; on float charge; or are discharging (supplying the electrical loads). In addition, there should be some kind of indicator light showing the shoreline is connected and supplying electricity; and an indication light or two on the battery charger showing what's going on there.

[Witchword]

It's a Numax charger and it's showing a red light. It used to whir if I used the strip lights but now it doesn't. I don't have the full manual for it. On the cut at the moment so it'll be interesting to see what happens when I plug back in. Usually it puts green and orange lights on. I haven't seen a red one before...