Battery Condition Indicators

[Drascomber]

I have a popular make of switch panel that incorporates a little vertical meter which is supposed to indicate the condition of each of my batteries when I throw the provided switch to either 1 or 2.

Whenever I use this the needle always goes in the green direction to full deflection. Usually this is what I expect as my battery usage is normally very low. However, I recently used the tiller pilot for days without running the engine - until the device stopped working because of low voltage. I took the batteries home and measured 11.5 volts i.e. both batteries totally flat. (BTW I don't have electric engine start and on this occasion running both batteries together)

But the Battery condition meter on the panel still went fully to the green end for each battery.

It is possible I have wired the thing up wrongly or is it a bum meter?

 

[Rick]

Meter is just a simple/cheap volt meter - it isn't a 6 volt one per chance?

 

[SvenglishTommy]

There might be an adjustable sensitivity controller in it that is set too low? I think there is only one way to wire them up, I was messing about with the wiring on mine and it melted when it was wired up incorrectly. I could never get the thing to give reliable readings so I took out the swtch and attached to a volt meter.

 

[Guest]

Simple moving coil meter .... some good some bad .... luck of the draw really.

My intention is to attach and mount a failed analogue multi-meter instead. Its a fag-packet size meter with small rotary switch on front for different tests. Dismantle meter .... remove switch part and solder wires to the contacts with external 1 - 0ff - 2 switch from the panel .... mount the meter display part where required set into nice face plate. Now you have a good meter indicator.

But note that checking straight after charging has been stopped or still oin - will show high result. Let batts settle for a while off charge will give better result.

IMHO - the average panel available over the counter looks nice - but is garbage ! The fuse holders - especially those with the little square red cap are disgraceful ..... half of mine don't stay in anymore ... and are wedged as the small clip has broke of.

 

[rob2]

I have one of these switch panels in my caravan. I know when the meter is indicating less than 100% - it's too bloody dark to find the panel! The 100% voltage is set somewhere around 11.5v. They're absolutely useless.

 

[Guest]

I had a Zig Panel in my last Caravan ..... excellent panel and also had a secret side-effect.

If you placed towels or anything in the cupboard above it - it warmed them very nicely ! The panel charge unit used to run quite warm ..... I actually went to the dealer and asked about it .... answer - quite normal and as long as vent grill is not blocked - no problem.

But the silly black panels that chandlers / boat jumbles sell - are a joke IMHO.

 

[blackbeard]

Indeed, as you say, bum meter. I had one which did the same. Confused me too.
Don't see how you can measure battery volts accurately enough with a moving coil meter. Digital one better, and, as has been said, useful only after battery has rested a while. And, even if reading looks OK, it doesn't necessarily follow that the battery is good.
Incidentally, the way my meter was originally set up (not by me), there was a live unfused wire leading from each battery to the switch on the meter, by-passing the main battery switch. A wire with insulation worn through could have started a fire. (If you go through the main switch the meter could not distinguish batteries 1 and 2.) Check that you haven't got the same set-up.

 

[William_H]

You should be able to see some change of position of the meter needle between fully chared and partially discharged if it is working correctly however the actual movement may be very tiny.
The problem is that if 15 volts is set as the max deflection for the meter 100% then a change of 1 volt about 6.6% and you need to see about .5 volt change. It is very difficult to determine 3.3% of the needle movement. especially on a tiny meter.
The simpole answer to buy a digital meter to fit in the panel or always rely on a digital multimeter.
There is another trick which involves fitting a 9volt zener diode in series with the meter. Thhe meter shunt is reduced in value to 1/3 of what it was. This makes the meter read actually only 5 volts from zero to 100% however the zener diode reduces or subtracts 9volts from the incoming voltage. The meter does not move until batter is above 9 volts then 20% of movement is 10 volts, 40% is 11V, 60& is 12v, 80% is 13V 100% is 14V.
This gives an expanded scale.
If you don't charge the battery them on the boat then the scale can be changed by reducing the resistor to make it 13V at full scale.
If you got a 11V zener or combination of zeners to give 11 volts then you could set up a scale for 11 to 13 volts which would be well expanded and readable.
A zener is a tiny silicon diode (a few pence at RS or Maplin) which shows typical .7 volt drop in the forward direction but in the reverse direction breaks down and conducts when the zener voltage is reached in a farly steep curve.(and stops conducting below the zener voltage) It is not perfectly accurate but good enough for these purposes. good luck olewill

 

[oldharry]

A good cheap alternative is an LED battery charge indicator usually around a tenner. I use one regularly in my caravan. Green light OK, Yellow light= get it charged tomorrow, Red light = charge it now. No light = no lights! Like all battery comndition indicators the readings are only true when the batery is off load, and has stood for at least 20 minutes. the better ones have five or six LEDs and give an indication whether the alternator is charging properly.

OK not as accurate as a DVM, but a whole lot more useful than those rubbish meters: and it has the advantage of being intelligible to the non techie mind: SWMBO soon tells me if the light is showing a different colour!

 

[Guest]

LED Alt / Batt checker ...

I have one - ex Halfords £9.99 ..... soon told me when alternator was shagged ! Excellent simple and works.

They have them via Maplins now at about £4.99 .... so cheap investment.

Others here advise digital meters .... ok - they indicate decimal volts etc. - but my understanding is that you may have volts - but no "guts" or "oomph" left in battery ... digital is so easily driven - that it shows nive voltage. But battery could be duff. An analogue meter is not quite so easily driven..... ok no real load there either .... but I'm told be leckies that a good analogue meter is worth a multitude of digitals without load checking !

Yep my alt / batt LED checker is my tool of preference for quick check on batt state.

My previous post about mounting an analogue meter was based on auto-leckies advice ..... he knows more about it than I do !!

 

[Drascomber]

Thanks Guys,

I didn't think it could be wired up wrong but I just couldn't beleive that it could be that wrong - well the consensus seems to be that it could!

I have already done two mods to this panel. a) replaced the '1, off, 2' switch with a 'sprung return to center off' one and b) replaced the cigar lighter socket with a marineco one when the original automotive one rusted in very short order.

These panels really are cr** aren't they. Still I really couldn't justify anything more expensive on my little boat.

BTW when the fuse holders break (as they do) you can get spares via Alladins Cave. Oder several while you are about it.