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How to understand battery condition when going off grid?


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Hello, we have a Bailey Unicorn IV and have started to use it on CL/CS sites without EHU. We are therefore reliant on the leisure battery & our 100W solar panel connected to a Truma Solar Dual Battery Charger for all our electrical needs. I do understand the green light system on the Truma Solar Charger display (ie solid green light charging, green light flashes battery fully charged etc), We also have a CBE display panel fitted to the wall with switches for the 12v system, lights, water pump etc and there is an LCD screen which is presently reading 12.6V. What I don’t really understand is what the CBE panel reading represents. (there is virtually no info in my manual). When is the reading too low & what should it ideally be at the beginning of the (& at the end of the day). I have just turned on my Avtex 12v TV & the reading has dropped from 12.6v to 12.3 v. I suppose what I want to know is how do I know when I need to start conserving electricity in after dusk etc? What does the reading represent. Wouldn’t it be simpler if the CBE panel showed the battery as a % (or am I missing something)? Are there any better displays which are more user friendly for off grid caravanning? Any help gratefully appreciated. Thanks

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I have the same caravan and system.We use off grid CLs most of the time.Just been out to check mine and it’s 13.6v .Is your leisure battery relatively new? If so I think it should be showing more.If you have a multimeter you can check more accurately. Hope this helps.

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Caravan & battery brand new last September. Used on 8 trips of which 3 off grid. Current reading 12.8v so at least it’s going up. Will dig out the multimeter when I get home. 

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We take a separate battery just for the television.Made up a fused wire which connects to the solar charger and charges that battery when main leisure battery is full. Just back from a fortnights holiday,not that sunny had no problems at all.Always keep one multimeter in the van ,cheap enough

 

 

 

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When the battery is being charged, you see the charger supply voltage (as johnsev's 13.6V probably from a 230V charger?)

From a solar panel (even 100W) you will not get more than a trickle charge which will be unable to keep pace with a TV plus normal 12v usage, so the battery will be discharging.

Edited by Ern
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9 minutes ago, Ern said:

When the battery is being charged, you see the charger supply voltage (as johnsev's 13.6V probably from a 230V charger?)

From a solar panel (even 100W) you will not get more than a trickle charge which will be unable to keep pace with a TV plus normal 12v usage, so the battery will be discharging.

Just done 6 days off grid.

Bailey Phoenix with the factory fitted solar panel. 
Watched a couple of hours TV each day.

iPads and phones charged daily.

Meter showed charging rate anything between 12.6 and 13.7

No problems at all.

 

Edited by PR1

2019 Bailey Platinum (640) Phoenix from Chipping Sodbury caravans, towed by our  2017 my Discovery Sport!

 

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5 minutes ago, Ern said:

When the battery is being charged, you see the charger supply voltage (as johnsev's 13.6V probably from a 230V charger?)

From a solar panel (even 100W) you will not get more than a trickle charge which will be unable to keep pace with a TV plus normal 12v usage, so the battery will be discharging.

No Ern.It’s from the solar panel.When we watch the avtec on the leisure battery when it’s sunny it charges more than the television uses .I make sure the panel is clean before going away.

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5 minutes ago, johnsev said:

No Ern.It’s from the solar panel.When we watch the avtec on the leisure battery when it’s sunny it charges more than the television uses .I make sure the panel is clean before going away.

OK I stand corrected. How much difference does cleaning the panel make (typically)?

I would have thought most TV watching happens when the solar panel is delivering nothing much, so the battery would be discharging short term, but that over 24hrs in good weather the panel would replenish the battery.

Edited by Ern
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10 minutes ago, Ern said:

OK I stand corrected. How much difference does cleaning the panel make (typically)?

I would have thought most TV watching happens when the solar panel is delivering nothing much, so the battery would be discharging short term, but that over 24hrs in good weather the panel would replenish the battery.

Never checked the roof panel but on my freestanding ( belt and braces) any shadow even from long grass will lower the solar voltage considerably.Thats why I keep it clean. Sadly I do watch tv in the day,can’t miss my F1

 

 

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Just as a guide, you may find this useful:image.png.1d752f9c2e7749e13e9c83df7138dca4.png

(Found it on the net, sorry no credit.)

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At this time of day, you should be getting at least 13.8v from the solar panel. 
I have a 2021 Bailey U4 Pamplona, and a couple of weeks ago, noticed my battery was at 12.6v in mid afternoon. 
Investigation showed only 6.3v at the battery terminals on solar controller. 
Further investigation found the solar fuse wasn’t fully inserted into the holder. At 12:12 today, I have 14.3v on battery. 
FYI on my van, the fuse is hidden next to the master fuse, alongside all the mover cables, in the tall cupboard next to shower. 

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A simple way to check on your battery will be to measure the battery voltage (with everything turned off) after sunset each day and use Julian's chart.  This will tell you if you are gaining or losing charge over each 24 hour period.

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Probably better if you have a small load on the battery when measuring the voltage.  Gives a more accurate measure of the batteries condition than a simple no load voltage check.

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On 21/07/2021 at 13:10, Julian Bryant said:

Just as a guide, you may find this useful:image.png.1d752f9c2e7749e13e9c83df7138dca4.png

(Found it on the net, sorry no credit.)

 

There are as many say on the net what you have copied as what is shown below:

 

image.png.071a541bd6e3e218d914c8a6ae2ace52.png

I suppose they are not too far apart as makes little difference.

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I run my battery down to 11.0 volts before the system cuts off  things like the tv and radio  and separate cooler box , (not built in fridge),   as the most important thing is the water pump for making brews late at night.

The solar panels boost the battery back up to 13.8V  in  the summer, long before we wake up so it works great.

 note We have 260W  of panels on the roof of our van   and yes I  clean them regularly as dust can cause a a 25% drop in efficiency.

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On 21/07/2021 at 11:43, David350 said:

Caravan & battery brand new last September. Used on 8 trips of which 3 off grid. Current reading 12.8v so at least it’s going up. Will dig out the multimeter when I get home. 

 

Seeing 12.8 volts at 11:40 last Wednesday a very sunny, hot and very high UV day hints that the solar system is not working. Some solar controllers are smart enough to back off supplying current completely once the battery is full, others back to lower currents to minimise battery damage.

It possibly might be that it is not required to work as 12.8 volts is about the figure we get from a fully charged battery under no demand no charge and rested conditions.

 

Under sunny conditions with all but a fully charged battery, in the conditions we had that time last Wednesday we would expect to see battery voltages up at or beyond 13.8, in needs to of that order to be effectively being charged. Indeed, with modern batteries and solar systems we see 14.4 odd volts during a healthy charge.

 

It is far from unknown for solar controllers to fail.

If you check the display panel early in the morning 08:30, after watching TV for an hour or more the preceding evening, if it is not showing anything over 13.4 volts, then there is a very good chance the solar system is not functioning. 

 

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It would be easy to write a small book on the black art of lead acid battery’s but will try and give a few pointers

1. There are multiple types of lead acid battery and volts will differ between say a flooded and an AGM.  

2.  The only place to measure it accurately is at the terminals. That meter on the wall will read lower due to wiring loses and it’s own inaccuracies.

3.  All lead acid battery’s reading will drop as you increase the load, like a TV.  They will jump back up again if you switch it off. 

4.  A 100 amp battery does not give you 100 amp except in very specific lab conditions. In real terms if you take it below 50 amp then you are seriously into damaging it.  

5. New battery. Leave it flat without charging for any period = now duff battery. 

And so it goes on.  

There are simple meters that will tell you exactly how much you have taken out or put in. You have to tell them what size the battery is to start.  Look at the. ‘ Renogy Battery Meter’ for example.   Very simple to wire in. Accurate.  Why don’t manufacturers fit them. God knows I don’t.  Or if you have deeper pockets. Get a good lithium with blue tooth. Eg. K S Energy. Or others.  Twice the power. Half the weight. And tells you exactly what you need to know. Plus will outlast the van probably. 

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Thanks to everybody for posting on this question - some excellent advice & Iots of great learning points. As a relative novice, without the years of experience of fellow forum members, knowing what to expect from a solar panel charging system is challenging. So we went off grid for 4 nights last week during a heatwave & my recollection of the voltage on the caravan display was between 11.8v up to 12.8v (probably averaging low 12v's). I definitely do not recall any volatge readings in the 13's of 14v's. We placed very little demand on the leisure battery, maybe a couple of hours of 12v Avtex TV in the early evening, charging ipads/Mifi, & of course the Whale water pump. We hardly used the 12v lights apart from at bedtime. From what I can glean from these helpful posts, during sunny July weather I should be expecting voltage readings in the 13v & 14v region, so if I'm languishhing in the 12v's then there is likely an issue with the solar system/battery?

 

Given that the van is only 10 months old I have decided to refer this to my Bailey dealer at it's first service in September & have it investigated as a warranty issue. In the meantime I'm going to pop up to the storage yard & thoroughly clean the solar panel, do some basic checks (ie solar control panel fuse,  loose connections, multimeter across the terminals etc). I will then  do some regular voltage readings whilst it is in storage (noting the weather conditions) & present the info to the sevice dept at the dealership. At least then they can properly investigate/advise on the issue. 

With the shoddy build quality of our Bailey Unicorn 4 Vigo it wouldn't surprise me if they forgot to connect the solar to the battery during the assembly last September. 

Again, many thanks to all those who took the time and trouble to post on this thread.

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David,

There is a very easy way to check how a solar system is performing, and adding a very useful bit of kit into your tool box for a small investment.

You can readily buy a little device that fits into a standard flat fuse holder, and with the removed fuse replaced in the "plug" of the device the current flowing can be checked.

With this you can check the current the solar system is pushing at the battery, by fitting it in the fuse holder connecting the solar controller to the battery [ hoping here Bailey put a fuse there as they ought].

You could also put in the main feed from the battery to the van, and see the drain or gains you get, with various things on and off.

Once the device is in place the circuit works just as before, it is not dependant on the current checker device being switch on, switching on only gives you a read out, it does no switch the system it is fitted into. Leaving it switched off serves to save on its little internal battery, so is good practice when you are not actually reading the current.

 

With this you will be left in no doubt about how the solar system is or is not working, plus it is a very useful tool in many other 12 volt DC checking roles. Armed with the info from this you can tell the dealer if the system is duff. If it uses a Truma branded controller, you will be far from the first who has had a failure with the controller, if indeed it has failed.

 

 

You tube introducing the current checker

 

Current tester

 

Edit: be a little guarded as these devices come in several fuse format types, so buy the one for the fuses you have, most likely the "standard", rather than possibly the "mini". Explore CPC web site for alternative sizes if needed.

Edited by JTQ
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Posted (edited)

Thanks for your help JTQ. Couple of questions - is the solar controller fuse location likely to be amongst the row of other 12v fuses or by itself (solar installed by Bailey at newbuild stage). Also, when I do get a reading on the Current Tester will this be amps or volts, and how do I correlate this in my mind as to whether the solar charger is working properly or not (ie what would be a good reading & what would be a poor reading)? Understanding what figures represent will be really helpful. 

Edited by David350
typo
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I can't help at all on Bailey's fuse configurations; others here might be able to. It would be very poor practice for the solar to battery connection not to be fused so I am pretty confident there will be one.

 

The "current" tester measures Amps, the amount of electricity flowing, and the direction it is flowing in.

Amps is of more relevance here than volts, in simplistic terms here, volts is the pressure to get things done, the amps the amount being done.

The Amps reading will vary greatly reflecting both what the sunlight can provide and what the battery needs and can take, so we can't Talk a specific value.

But if it is a 100 Watt panel there is the potential to see quite a high current. [Watts is power and is the multiple of the volts and amps; so 100/ say 14 volts=7 amps, therefore if the battery needed it, last Wednesday at about mid day, seeing a reading of a charge of 7 amps, would have  been a possibility].

As the sun angle drops, the clouds gather, a fly lands on the panel  or simply the battery in nearing "full" the amps will decay. On a dull day to possibly down to 0.5 amps.

 

But the important thing is the current tester will show if the controller is doing anything, and it is an easy judgement to see if anything it is doing is in the right ball park. eg if the battery is down at 12.6 Volts, the sun is overhead and blazing like last Wednesday, if the current tester was only showing 1 amp, we know the solar system is not working anything like correctly.

Using it past storting out the present potential issue, will quickly allow you to gain an understanding of the systems effectiveness and limitations in poorer light condition, so manage your TV usage etc. Then best shelved to avoid becoming like me, possibly a bit of a technical anorak!

 

 

Edited by JTQ
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JTQ - that's most helpful. Were would we be withouth technical anoraks :D

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Well I popped up to the storage yard today and gave the solar panel a good clean (it was dusty but would't say it was filthy). Weather was very sunny and it was 2pm. The caravan voltage meter was reading 13.3v. I checked the Truma Solar Battery Charger Unit with my multimeter - it showed 20.4v coming from the solar panel connections and 13.3v on the outgoing leisure battery connections. Main fuse on the Truma Control Panel seemed ok. I then checked the leisure battery terminals with the multimeter - 13.4v. I checked the 'battery type' setting on the Truma control panel - the dealer had set this to "Gel" (which was incorrect as they fitted a wet/flooded battery) so I changed it to "Liquid Electrolyte". Not sure if this incorrect setting makes any difference?  I've looked at he Truma Solar Control manual and it refers to voltages of 13.3v on the Bulk Phase, 13.8v on the Float Phase, 14.6v on Absorption Phase and 14.8v on the Equalisation Phase. So at the moment I seem to be maxing out at 13.3v.  Still a bit confused whether things are working as they should do - will check the readings over the next few days. Not getting the 13.8v to 14.4v readings that some of you get so still not sure if control panel or battery are working properly. There is a lot  more to batteries/solar than I first expected. 

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Sure is.   Yes the setting for the panel set at Gel would not help. Each different type of battery needs different volts to fully charge.  From what you are reading I would guess that your battery is in Bulk because it is not fully charged.  As it gets to fully charged the solar will up the volts to take account of the absorption and float to keep it that way without over charging it.   Keep an eye on the electro light if you can because if the battery is faulty it will never reach full charge and can boil which you most certainly do not want.  The volts you are reading is just that volts coming out of the solar charger.  Bit like the temperature of water out of a tap.  How much power you are getting (. i.e. how fast the tap is running). is Amps.  Which you cannot measure with your controller.  On a really good day you might get say 5amp per hour out of your controller so 10 hours would take your battery (100 amp). from 50% to 100 %. except it will not because as a lead acid battery reaches fully charged the amount of charge it will accept tails off.

 

All good fun.  That is why I advocate the fitting of a proper battery meter, preferably also you could change the solar charge controller to a proper job.  The standard truma is IMHO rubbish.  Not because out does not work, it does.  But it does not tell you anything much.  For example a straight swap to a Victron 75/15 with Blue tooth will tell you a mine of information.  Not only is it more efficient in the power it obtains from the sun, it will tell you what the panel is generating, what is going into the battery, what part of the charging cycle and a lot more, including an accurate volts reading (every van I have had the control panel volts read approx 0.2 v low.    It will keep a record of the last 30 days as well so you can get a fair idea of your battery health.  What it will not tell you in the wiring configuration used in the van is how much you have taken out.   The battery meter will tell you exactly what you have taken out and put back in.

Edited by Alan Stanley
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David, the readings might be explained by the battery being so low that the controller is forced into the bulk phase as you suspect. If that is true and the kit is working well, given time and good weather it will climb to 14.4 [according to one of Truma's data sheets for the "wet" setting.]

 

In the bulk phase the current will be as high as the solar panel/controller can supply; there as Alan is saying, and I did, we need to know what the current [amps] is, as that is so informative. The tester I mentioned would give you that.

 

Presently you can only observe how things progress, if all is well the voltage will rise then back off. From Truma's figures to 13.8, once and if it achieves "fully charged".

 

It is slightly concerning that given the recent weather, that things are still down at the more depleted end, so of the bulk charge can't lift the voltage off that low 13.3 value. But if you had hammered your recent usage, that could explain why even with a healthy system, we could be down there. Time or an amp [current] tester, will tell.

 

Your 20 odd volts from the panel, if nothing else proves it has the volts there to drive things, again,  knowing the current in or out of the controller would add so much more informative info.

 

Cheers, John

 

 

Edited by JTQ
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