Battery voltage and solar charge

Jan 10, 2009
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This has probably been asked in many guises, but I can't seem to find quite what I was looking for.

A couple of days ago I got a low battery alert from my van.

When I checked, the level was showing 9.6 volts, the solar charger was not adding anything to this.

I brought the battery home and put it on charge, albeit on a smallish charger, but on the fast 5.5A setting. After about 6 hours the voltage measured at the battery was 12.86v. After disconnecting the charger, this rapidly dropped to about 12.5v.

The van is fairly new and has an alarm, I was worried that I would need to keep the battery on the van to ensure the alarm worked (although having just read the manual it appears that the alarm has it's own back up battery)

I put the battery back on the van and the voltage dropped to 12v overnight. Today the solar panel has varied between nothing and 0.6A, it has been quite bright sunshine but I cannot vouch for how much has been hitting the solar panel.(I cleared the snow off, but there was a bit of ice left on the panel)

The battery has since dropped to 11.8v.

Now for the geeky bit;
The battery has been showing a daily voltage of 12.8v, peaking to 15v during the day(according to the data) this daily cycle happened throughout December.
On New Years Eve there was no voltage spike and very slowly over the course of the last 3 weeks the voltage has reduced until I received the alarm last week.

So, my questions are,

Is the battery beyond help?

The current off the solar panel seems low (max 0.6A today), is that what one would expect on a bright winters day?

Could it be that the poorly battery limits what it can accept off the solar panel?

Thanks in advance for anyone who understands this !
 
Mar 14, 2005
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Clearly something is discharging the battery, and it seems you need to find out what it is and why.

I know that some solar panels can discharge a battery if there is no solar charge controller fitted. The solar charge controller will prevent that, and it will ensure the power transfer from the panel to the battery will always be optimised when ever the panel has enough light falling on it.

It might be worth fully recharging the battery on mains, then leaving it disconnected for a day or two and then checking the terminal voltage., it should be about 12.8V. If its much below this then it suggests the battery has been damaged.

You could take the battery to a specialist who should be able to give you a fuller answer.
 
Sep 26, 2018
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81
1,735
This has probably been asked in many guises, but I can't seem to find quite what I was looking for.

A couple of days ago I got a low battery alert from my van.

When I checked, the level was showing 9.6 volts, the solar charger was not adding anything to this.

I brought the battery home and put it on charge, albeit on a smallish charger, but on the fast 5.5A setting. After about 6 hours the voltage measured at the battery was 12.86v. After disconnecting the charger, this rapidly dropped to about 12.5v.

The van is fairly new and has an alarm, I was worried that I would need to keep the battery on the van to ensure the alarm worked (although having just read the manual it appears that the alarm has it's own back up battery)

I put the battery back on the van and the voltage dropped to 12v overnight. Today the solar panel has varied between nothing and 0.6A, it has been quite bright sunshine but I cannot vouch for how much has been hitting the solar panel.(I cleared the snow off, but there was a bit of ice left on the panel)

The battery has since dropped to 11.8v.

Now for the geeky bit;
The battery has been showing a daily voltage of 12.8v, peaking to 15v during the day(according to the data) this daily cycle happened throughout December.
On New Years Eve there was no voltage spike and very slowly over the course of the last 3 weeks the voltage has reduced until I received the alarm last week.

So, my questions are,

Is the battery beyond help?

The current off the solar panel seems low (max 0.6A today), is that what one would expect on a bright winters day?

Could it be that the poorly battery limits what it can accept off the solar panel?

Thanks in advance for anyone who understands this !
Let's analyse what you've said...

1. Something changed on 31st December
2. Your solar panel is still producing a peak current of 0.6A. My experience of solar in multiple cases (boat and caravan) is that reading is good, and you have to remember that the angle of incidence between the panel and the sun at its peak now is about 30 degrees so 0.6A is fine. I have NEVER mains charged my boat domestic batteries in winter since I installed panels 10 years ago...
3. The change recorded to me looks like a battery developing a fault (if a flooded LA battery is it topped up) rather than a sudden change in current draw

As the Prof said getting a drop test done by a battery specialist is the best way to confirm
 
Jan 10, 2009
18
4
18,515
Thanks for the replies.
The van is only 6 months old, the solar panel has a controller which stops it draining the battery and does some clever stuff to charge the battery 😀.
What concerned me slightly was seeing a peak voltage of over 15v, I don’t think I have ever seen that before. (Not sure how accurate the monitoring instrument is)
Anyway, battery is down to 9.4v today

it is a sealed for life type with the o of stir window which supposed tells you if it’s good, needs charging or ready for the bin.

0.6 A,interesting what you say about the angle of the sun.Yesterday was really sunny but very low in the sky, I didn’t realise what affect that would have.

In a way, I hope it is just the battery that has given up, it’s about 6 years old, others I have had have lasted 8 years.

might see if I can get it on charge for a few days. (As mentioned before, I was nervous about taking it off the van for prolonged periods because if the alarm, but now I know that’s not an issue)

thanks for responding, I’ll keep you informed just out of interest
 
Jan 10, 2009
18
4
18,515
I think have have pretty much accepted that the battery is only ever going to be good as a big doorstop from now on.

just doing a bit of digging though, found the instructions for the solar battery charger and there are different settings for different types of battery.
I am wondering if it is set to the wrong type and that could have lead to the 15volt peaks that I have seen.
Only problem is I Can’t find the charger! I need to have another look, unless anybody can help, the van is a Superb Quattro (8ft wide so even more space to hide the damn thing😀)
 
Mar 14, 2005
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Good to read you have a charge controller, and unless the controller has gone faulty it does more strongly suggest the battery may be at fault.

Guzzilazz is correct to point out how the elevation of the sun which is much lower at this time of year will adversely affect the output current from a solar panel, and the shorter hours of daylight reduce the total power the panel produces each day. And depending on where the solar panel is located, if any obstruction casts a shadow across part of the panel the power out put will also be reduced roughly in proportion to the area of the shadow vs total area.

Basically anything that restricts or prevents light reaching active layer in the panel will reduce the panels effectivness

However without knowing the size (watts) of the panel you have I couldn't tell you if 0.6A output is reasonable of not given the factors mentioned above.


Battery life has so many factors its very difficult to give a good/bad answer without actual tests being carried out. The different battery constructions will also affect life expectancy and at 6 years old its certainly got an increased chance of being the cause of your symptoms.
 
Jan 10, 2009
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Going to order a new battery, find the solar magic box, make sure it’s on the right setting and the download the battery voltages after a few days and see if anything looks untoward. Also not sure what capacity the solar controller is, I have a 110 ah battery, just hoping my controller is the larger model
 
Oct 8, 2006
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It would help if the OP told us make, model, and year of his caravan. We have a Unicorn all S4 models of which come with a 100W solar panel as standard (but note NOT included in the Miro!)
We came back from a one-week trip at October half term and I didn't put mains on the van expecting the solar to keep it topped up. Sadly it didn't - modern panels should work in any level of daylight , sun angle etc doesn't come into it - but it seems there was too much residual drain to keep it up - it was down to 3.8 volts! The irony in the tale is that the solar control needs volts on the battery to keep it going, and if the battery gets low.......? I found out a few weeks ago, took the battery out, and recharged it the old fashioned way with a bulb in series from a 13.6V supply. It took about three days but it got up to aroun 11.8V at which point I put the smart charger on it which brought it up to full in about 36 hours and its been OK ever since - its a Varta 90Ah low profile.
In respect of the solar panel voltage, mine also shows as much as 15.6V on a sunny day but it is nothing to worry about as it depends upon the current available from the panel controller which may be negligible. Of course there is no way of knowing where the voltmeter sits in the circuit either. Next time I see such a voltage I shall whip the cover off the battery box and check it with a DVM!
 

JTQ

May 7, 2005
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modern panels should work in any level of daylight , sun angle etc doesn't come into it
Sun angle very much does come into it.
By far the greatest yield will come from direct sunlight striking the panel.
Solar farms spend money on the elevation and azimuth of their panels, for that very reason.
The greatest elevation the sun rose to in London today was only 20 degrees to the horizon.
Our horizontally roof mounted solar panels will gain some of the little they can this time of the year, from reflected and refracted light off clouds. How well various panel types cope at this can differ,
 
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Jan 10, 2009
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Sorry not specifically said what my van was, although it is in text as Superb Quattro, it should have said Swift Super Quattro Celebrate (Glossop caravans special) as mentioned previously it’s only 6 months old.
 
Mar 10, 2006
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Swift use a 80watt solar which in practice will maintain the battery year round.
But you need to ensure the black power button is off.
My 90Ah Varta never drops below 12.5v over night, and typically show around 13.5v during the day.

Also even when covered in snow for a couple of days the battery still holds up.
The controller is usually located in a top cupboard near the panel or above the battery.
 

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