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How to understand battery condition when going off grid?


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Well I've ordered a current tester so will pop back up to the storage yard later this week when it arrives & do some further tests. If  nothing else, at least I will have some stats to show the dealer when the van goes in for it's service in September. Hopefully the reading will be heading in the right direction. Very much appreciate all the advice you guys have provided. 

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Well (I think) I’ve sorted it thanks to the help from fellow forum members. I bought an automotive current tester (thanks John for suggestion) and headed off to the storage yard today. Still reading 13.3v on the caravan voltage panel so a bit disheartened. Thanks to forum member ‘Lost in the wilderness’ I found a couple of fuses in the wiring loom in a the locker near the motor mover control box. There was a 15A fuse which I checked with the automotive tester & all ok (the radio came on when I flicked the 12v switch, don’t know why) but still reading 13.3v at the voltage panel. I then tried the other 20A fuse with the tester, switched the 12v supply on and the voltage display started reading 14.5v. Took the 20A fuse out and the voltage display dropped again to 13.3v. Both the 15A & 20A fuses had not blown. So it’s definitely something to do with the 20A fuse in the wiring loom (presumably the fuse between the Truma Solar Control panel and the leisure battery?) - probably like ‘Lost in the wilderness’ suggested, his fuse was loose and maybe mine was as well. So taking out the 20A fuse to use in the automotive current tester & reinserting it might have solved the problem. Both fuses were exposed in the locker area, so probably prone to being knocked by all the kit that gets chucked in there - surprised that Bailey/dealer didn’t fit fuse holders in some sort of protective case to avoid this happening. So fingers crossed it’s sorted, but will get dealership to check this when in for a service. Thanks to everyone who gave me advice. :Thankyou:

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But what current did the tester read, when in that 20 amp fuse holder, whilst the voltage read out was 14.5 volts?

As said earlier, knowing the amp [current] figure is the only real indication of what "amount" is actually going into the battery; albeit just at that moment of time. The volts only tells us how hard in has to "push" to get it in, not what it is achieving to push in. That's what current tells us and why it is important.

 

Then, if you multiply the 14.5 volts with the amps from the reader, we will know what Watts the panel was achieving.

 

Anyway, great to hear you have seen 14.5 volts, so we know at least the battery is being charged

 

 

 

 

Edited by JTQ
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Re the fuses, if they are in the locker they are definitely exposed to  the elements,  water vapour, which can settle as tiny drops of water on electrical surfaces over long periods of time as the temperature swings from hot to cold and back again.

On coachman vans  they are in the van, under the seating so less likely to get corrosion on them.

There are two types of automotive  of the standard size ( there are miniature and truck sized ones as well) 

ATO and ATC  , the O is for open  where the  actual link   is not covered with plastic  and  C is covered  i.e. encased in plastic  and hence harder to see if its OK.

For ones in the front locker I would recommend ATC type,  and a good method to stop corrosion setting in is to spray the fuse and fuse holders with silicone spray , this wont reduce the connectivity.

"Quicksilver corrosion guard" can also be used- its used on outboard motors electrics to prevent water damage and ingress on the electrical wiring, it dries to a non-sticky finish unlike WD40 which just attracts dust and dirt overtime.

It is expensive though,  Ambersil silicone spray is what I use on non-marine electrical connections  - at a pinch  I have even used tent proofing spray-mainly on old seven pin  tow hitch connectors when onsite .

The action of removing the fuse from its holder helps to clean the contact surfaces  by  a wiping action and this seems to have cured your problem.

The corrosion looks like small white deposits ( tin oxide) on the blade of the fuse.

  it can  be cleaned with a non abrasive pad such as a pencil eraser, don't use emery cloth as you may remove the protective tin plating.

Also, a fuse which shows physical damage -i.e  the plastic holder changing shape due to heating up- should be changed  as this is a  sure sign of high resistance of the fuse /fuse holder connections.

Hope this info helps

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On 29/07/2021 at 16:23, JTQ said:

But what current did the tester read, when in that 20 amp fuse holder, whilst the voltage read out was 14.5 volts?

As said earlier, knowing the amp [current] figure is the only real indication of what "amount" is actually going into the battery; albeit just at that moment of time. The volts only tells us how hard in has to "push" to get it in, not what it is achieving to push in. That's what current tells us and why it is important.

 

Then, if you multiply the 14.5 volts with the amps from the reader, we will know what Watts the panel was achieving.

 

Anyway, great to hear you have seen 14.5 volts, so we know at least the battery is being charged

 

 

 

 

OK, so I've popped  up to the storage yard this morning to do some jobs and state of play is as follows. Readings taken at 8:20am (very dull/overcast) - Caravan display 13.7v. Truma control panel (incoming from solar) 19v on multimeter. Truma control panel (to battery) 13.8v on miltimeter. Reading from Automotive Current Tester on the Truma Solar Control main fuse was 0.76A. So by my calculation it's producing 10.4 Watts (ie 13.7v x 0.76A).  I'm hoping this is reasonable for a cloudy day  early morning? Hopefully the cleaning of the solar panel, refitting the loose main fuse & changing the incorrect battery setting on the Truma controller will all have  helped. I'll keep an eye on it & take some readings on sunnier days, but hopefully the issue is now resolved. Thanks for all the help & advice. 

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That is all looking about as would be expected, the system is clearly functioning and your understanding is right, there is presently a 10.4 Watts of power.

As the sun rises in elevation this should improve, becoming far better during periods where the sunlight, rather than being diffused and reflected light off the clouds, is getting directly to the panel.

That little Current tester really does unlock seeing what is actually happening.

Glad to be of help. John

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