Batteries & voltage drops.....again.

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Nicholas123

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Just been down to my boat & the battery voltage read at the solar panel controller thing said 11.8 volts.Now that is without anything turned on & it seems to drop about a volt every day or two so does that mean that I have got a short or is that just normal for heavily depleted batteries?
Incidentally,when I took the battery out of the system completely the solar panel thing read 6.8 volts presumably that is not enough to contribute anything to charging?

Thanks for your patience :)
 
I don't want to go over the same information as your previous thread regarding charge vs. Voltage.
http://www.ybw.com/forums/showthread.php?t=342014

It would be worth buying a cheap multimeter and checking battery voltage and if panel does have a diode (highly likely as you have a regulator). You can get a cheap analogue meter from Screwfix for £3.59 but you'd be much btter off getting a digital one somewhere for a tenner. Then you could check each part of the system.

I think it is highly likely that your battery life is being shortened due to severe undercharging. I think that I'm pretty safe making that statement as it is a quite common state of affairs anyway and Voltages you have mentioned don't indicate a healthy system.


You asked if 6.8V from a panel would charge. It would only charge if it is a 6V battery, you need to be a bit above 12.5V to charge. I won't go into detail but even keeping a battery at that Voltage 24x7 wouldn't get it back to 100%.
 
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Nicholas123 said:
I did'nt have the means to test it independently while I was down my boat Nigel but when I got home I tested it with a little Aldi battery & alternator tester & the yellow light lit up indicating 12volts & a 1/3rd empty battery.
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I suggest that before you take a lot of notice of your Aldi tester you compare the voltages at which the various LEDs are suppose to come on with the values, measured with a reliable multimeter, at which they actually come on.

I have one ... there is quite some difference !

If you don't have a multimeter get one. THIS ONE from Maplin will be adequate. If you see them on a BOGOF offer get two!

You dont say what solar panel controller you have but presumably if it has a voltage readout it is not one of the very basic ones and it will almost certainly include a blocking diode in its circuitry. The instructions should confirm.

In the meantime charge your battery properly
 
The reality is acceptable multimeters for everyday use are so cheap these days there is no excuse for not having one everywhere you might need one
 
Nicholas123 said:
Just been down to my boat & the battery voltage read at the solar panel controller thing said 11.8 volts.Now that is without anything turned on & it seems to drop about a volt every day or two so does that mean that I have got a short or is that just normal for heavily depleted batteries?
Incidentally,when I took the battery out of the system completely the solar panel thing read 6.8 volts presumably that is not enough to contribute anything to charging?

Thanks for your patience :)
Click to expand...

The 6.8 volts from the solar is no good for battery charging. Now I don't know how much sun you had at the time and if the panel was facing the sun. If there was sun and the pane facing the sun you should have got more voltage. With no connections to the solar panel you should get around 19 volts coming from the panel.
You can use a multimeter on amps scale to check current delivery. This should be around half an amp for 10w in strong sun. With the multimeter probes from +ve to -ve yes shorting out the panel with the amp meter. Obviously in UK winter at best you will get a lot less current but it may mean that you have a dud controller or panel.
If the panel seems OK then try direct connection panel to battery and measure current into battery with your multimeter on amps scale. If the panel has a diode built in (you can sometimes see the diode in the connection box at the panel) then you can leave it connected to the batteries to get the best charge (best except for mppt type controllers)
However I think your battery needs a charge ASAP to try to save it. good luck olewill
 
Cheapo multi-meters are OK as a very rough guide, but unless you can check it against a properly calibrated meter don't expect to accurately measure voltages any better than within 0.5 v or so. I've even known some to be more than 0.75v out. :)
 
OK OK I shall lash out on a multi-meter :)

The good news is that according to my Aldi thingamee after a 24 hour charge with my trickle charger it now says the voltage is somewhere between 13.2 & 14.5 volts.:eek::confused:
Hopefully now my bloody battery is'nt about to blow up :D
 
Unfortunately a very high % of solar panels (e.g. all the Kyocera range) do not have a fitted diode.

The thinking behind this is that the power loss between panel and battery is greater than the back-loss during darkness from battery to panel.

The 11.8v reading is probably the panel volts.
Given that an overcast day and effective shadowing could reduce the output of an old panel to that sort of level, I would be far more interested in the actual battery volts.
If battery volts are at 11.8 I'd suspect a duff cell in the battery.
But without effective metering it's all hot air.
 
Davegriff said:
Cheapo multi-meters are OK as a very rough guide, but unless you can check it against a properly calibrated meter don't expect to accurately measure voltages any better than within 0.5 v or so. I've even known some to be more than 0.75v out. :)
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Ditto that, I had a good meter left at home and needed to do some checks, bought a £ <5 but rubbish accuracy, proved by later comparison with others.
 
johnphilip said:
Ditto that, I had a good meter left at home and needed to do some checks, bought a £ <5 but rubbish accuracy, proved by later comparison with others.
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I have bought three cheapies from Maplin, two for myself and a third which i gave to my son.

when checked all agreed with each other and with an AVO, at least on the DC voltage ranges
No reason to doubt any of the readings I have seen.
 
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