Vehicle Battery Charging when only on solar. (1 Viewer)

[Sheddy]

Our cab battery is not charging sufficiently when we are on our long term pitch here in Benidorm.
We are not on hookup.
We have 2 x 125ah new leisure batteries charged by a 175w solar panel.
Our CBE 12v System is designed to charge the cab battery when the leisure batteries exceed 13.6v, however it seems that during the normal day not enough is getting to the vehicle battery and it slowly loses its charge over several weeks.
I run the engine for 30 minutes once a month which helps a bit, but I don't want to run it just to maintain the vehicle battery charge.
The cab battery runs the alarm system and the cab door foot well light which comes on and off when the hab door opens.
I have removed the halogen bulb from the door light to reduce the draw to a minimum, but I need to have the alarm system working .
Can I run a temporary fused cable from the positive of the nearby leisure batteries to the positive of the cab battery to maintain the charge? and if so what are the likely effects to the remainder of the 12v system.
Cheers
Ed

 

[Robert Clark]

How about a battery master ?
@Jim sells them in his shop

 

[TerryL]

Ordinarily I would have expected your CBE system to cope with it, but 13.6v seems a tad high for the cab battery charge to cut in especially as I would agree that your solar panel would struggle to get above that (mine never gets above 13.7v). Looks like it may be set to only cut in on hookup, though I'm no expert at these systems - just a laymans observations.

Would guess Robert Clark suggestion is a good idea - mine cuts in a lot lower than 13.6v.
Other suggestions bound to follow.

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[Lenny HB]

At this time of year you are not getting enough solar power the charge your leisure batteries. The reason for the 13.6v threshold is so you don't flatten the leisure batteries charging the engine battery.
You either need to fit much more solar or use a EHU occasionally, also not charging the leisure batteries fully will shorten their life. As a tempory measure you could fit a changeover switch to switch the solar charge between the leisure batteries and the engine battery.

 

[Robert Clark]

Would guess Robert Clark suggestion is a good idea - mine cuts in a lot lower than 13.6v.
Other suggestions bound to follow.

From memory I think my battery master cuts in when the engine battery is 1v lower than the leisure batteries, irrespective of what the actual voltages are.

 

[Lenny HB]

How about a battery master ?
@Jim sells them in his shop

He already has a similar system fitted hence the ref to the 13.6v trigger.

Ordinarily I would have expected your CBE system to cope with it, but 13.6v seems a tad high for the cab battery charge to cut in especially as I would agree that your solar panel would struggle to get above that (mine never gets above 13.7v). Looks like it may be set to only cut in on hookup, though I'm no expert at these systems - just a laymans observations.

Would guess Robert Clark suggestion is a good idea - mine cuts in a lot lower than 13.6v.
Other suggestions bound to follow.

I use a CBE split charge relay with my Elektroblock which diverts charge to the engine battery when leisure batteries are above 13.6 volts works a treat. The 13.6 threshold is so you don't start charging the starter battery until the leisure batteries have a reasonable charge, it kicks in at 13.6v but doesn't drop out until down to 12.6v.

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[Hymie]

How about a battery master ?
@Jim sells them in his shop

Great bit of kit, sorted out my cab battery problems after losing 2 to the dreaded bleed.

Hymie

 

[Jaws]

To answer the question put by the OP, yes you could do as you suggest..

 

[BreweryDave]

Why not just add a cheapo engine battery solar charger like this ? Plenty on eBay etc, am sure someone can bring one over for you if you can't find in Spain !

https://www.ebay.co.uk/itm/332025209978

Simple and job done. Just hang it out of the bonnet.

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[PhilandMena]

I Like the recommendation above but you will need a lot more than 1.5W. If you want a long term solution this is probably the cheapest way to go and simple to install yourself. However, another option is to go on hook up once a fortnight for 24 hours and fully charge your cab battery. I'm not sure what the drain is on your Cab battery so you may need to adjust the charging interval accordingly.

 

[Lenny HB]

Why not just add a cheapo engine battery solar charger like this ? Plenty on eBay etc, am sure someone can bring one over for you if you can't find in Spain !

https://www.ebay.co.uk/itm/332025209978

Simple and job done. Just hang it out of the bonnet.

1.5 watts won't do anything this time of year even in Spain would need at least 20 watts.

 

[daveandsan]

@Sheddy, could your cab battery be on the way out. I have two CBEs coming off my leisure battery, one charging the cab battery and the other charging the auxiliary battery. Works fine in the middle of winter with just 140 watts of solar.

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[hilldweller]

Can I run a temporary fused cable from the positive of the nearby leisure batteries to the positive of the cab battery to maintain the charge? and if so what are the likely effects to the remainder of the 12v system.
Cheers
Ed

If you put a 12V headlamp bulb in this battery to battery link you have a self limiting system. A 12V 55W bulb will pass a max of 4A between batteries but it also has a very low resistance at very low currents ( when both are well charged ) so eventually both sets of batteries are fully charged if you have enough sun.

Do your leisure batteries ever get to 13.6V ? As others have said, if they are not they are never being charged properly. Out solar keeps kicking the batteries up to 14.2V for the odd second or two. Is the solar charger faulty ?

 

[Sheddy]

To answer the question put by the OP, yes you could do as you suggest..

Thanks for all your response and suggestions, it is just reassuring to ask a question a get knowledgeable advise.
Thanks Guys
Cheers
Ed

 

[Lenny HB]

From memory I think my battery master cuts in when the engine battery is 1v lower than the leisure batteries, irrespective of what the actual voltages are.

I thought you had a BtoB not a Batterymaster?

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[Robert Clark]

I thought you had a BtoB not a Batterymaster?

Had one fitted due to dealer incompetence after attempting to resolve a minor electrical fault which took out the D+ circuit (issue with split charge relay).

Its a loooooooooooooooong story Lenny, one which if I told you, would only encourage you to gloat !

 

[SUGGY]

i would fit more solar ,170 is not a lot for constant winter use ,
i had 260w 0n the Fendt and had no problems with charging both sets of batteries ,
i am putting 300w on the next van then it will run the 3 way fridge during solar charging hours ,
i fitted a 100 amp battery isolator switch between the leisure battery and the engine battery so that the solar charge can be linked to both batteries .

 

[Jaws]

Lads.. The motorhome in question IS in Benidorm, so not sure why folk are going on about winter use and solar panels.. We found there is more than enough sun to keep everything running when we are down there

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[hilldweller]

We found there is more than enough sun to keep everything running when we are down there

Well he has 175W, how much do you have ? What are his electricity needs compared to yours ?

 

[Jaws]

Well he has 175W, how much do you have ? What are his electricity needs compared to yours ?

We are current hungry.. The telly ( 22" Cello ) is on for a few hours every morning and most nights from 6 until gone midnight..
Nowadays we have 300w of panels but originally only 180, so very comparable

 

[eddie]

He already has a similar system fitted hence the ref to the 13.6v trigger.

I use a CBE split charge relay with my Elektroblock which diverts charge to the engine battery when leisure batteries are above 13.6 volts works a treat. The 13.6 threshold is so you don't start charging the starter battery until the leisure batteries have a reasonable charge, it kicks in at 13.6v but doesn't drop out until down to 12.6v.

Different thing. Battery Master starts to work when the leisure battery(s) are 0.75 VDC above the engine battery

Or when the engine battery drops below 0.75VDC the leisure battery

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[Taran_Las]

Why hasn't anyone offered Eddie the most obvious solution?

Don't go to Benidorm.

Stay at home and enjoy the glorious winter weather Wales has to offer


​

 

[Lenny HB]

Why hasn't anyone offered Eddie the most obvious solution?

Don't go to Benidorm.

Stay at home and enjoy the glorious winter weather Wales has to offer


​

A poor misguided fool

 

[WSandME]

I'm not really conversant with solar panel performance, but I'd like to suggest something for the assembled sages to critique:
As you are on a long-term pitch, is it at all possible to re-orient your existing solar panel so as to face the sun more squarely for the lit part of the day?
I wonder wether that may make sufficient difference to solve your problem

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[hilldweller]

is it at all possible to re-orient your existing solar panel so as to face the sun more squarely for the lit part of the day?

"Tracking", yes indeed and a good increase in power is obtainable. But it is difficult and expensive so throwing on another flat panel is the simple solution, space permitting.

One crazy solution out there is a solar panel on the back of a satellite dish. This will track the sun for maximum performance, just a pity if you want to watch TV during the day.

 

[Doctor Dave]

I'm not really conversant with solar panel performance, but I'd like to suggest something for the assembled sages to critique:
As you are on a long-term pitch, is it at all possible to re-orient your existing solar panel so as to face the sun more squarely for the lit part of the day?
I wonder wether that may make sufficient difference to solve your problem

Yes, it will make a big difference. When I had my narrowboat I had the solar panels on a turntable with a tilt mechanism. Much much better to have the panels pointing to the sun than flat.

I don't see a practical way of doing this on a motorhome though. On my boat it was a push button job cos my auto align system gave up really before it started. The best thing, in summer, was to turn the panels to face east before going to bed, and put them vertical, they then charged the batteries before we got up - assuming it was a sunny summers day!


Dave

 

[Kevan]

Am sure you will get there Edd just keep at mate, wish i was there having the same problem, it's freezing in Herne Bay

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[aandncaravan]

We agree with Lenny, that your habitation batteries are taking all the charge so none left for the Starter battery.

Is that because the Habitation batteries have gone past their best and just wasting the Solar charge?
Each time a battery is discharged and charged it degrades slightly so by the time a battery is 1 year old it will be down on efficiencey, even if it is holding a charge.
If yours are being charged and discharged every day, then many batteries with a 400 cycle life will be approaching retirement by a years 365 cycles?

When a battery gets to this state, it takes more energy to charge it up and you get less back.

For example when a 100Ah battery is new it might take 110 amps to charge up and give back a real 100amps.
By the time it is a year old it may be taking 125 amps to charge and giving back just 90 amps
By the time it is 2 years old it may be taking 135 amps to charge and giving back 80 amps.
By the time it is 3 years old it may be taking 150 amps to charge and giving back 70 amps.
In this state, so long as no major Plate material has detached causing 'shorts' the battery may be holding it's charge and appear 'normal'.

It's more complex than that but shows the process.


More than any other type of charging, Solar is the one that really requires a perfect, efficient battery if you are going to maximise every precious amp.

It's like the difference between you having a Water tank that is perfect versus one that has holes in that get bigger each time you fill it up so it is constantly leaking out.
But worse than that, imagine your hose pipe you use to fill it also has holes in it that are getting bigger each time, so spills a quantity of water which never even gets into the tank.
You end up using twice as much water to fill the tank, but end up only being able to use half of it.

That would explain why the batteries are not getting fully charged and why the Starter battery isn't getting a look in?
We would suggest you look at how old the batteries are, what cyclic rating they had, etc.

I know the post states new batteries, but we have people talk about 'new' batteries that are 'only 2 years old'.
If this is the cause the batteries may be close to sudden total failure, so suggest fairly prompt action?
Suggest you don't try and take any power from the habitation batteries for the Starter battery, by whatever means until you are sure the habitation batteries are perfect, as it might 'tip things over the edge'?

If the batteries really are less than a month old, is there an extra load being placed on the habitation batteries that wasn't there previously? Maybe a bigger TV, or extra lights being used, etc.


.

 

[pappajohn]

Why not just add a cheapo engine battery solar charger like this ? Plenty on eBay etc, am sure someone can bring one over for you if you can't find in Spain !

https://www.ebay.co.uk/itm/332025209978

Simple and job done. Just hang it out of the bonnet.

1.5 Watts = 125ma @ 12v(theoretically)....in winter 15 to 20milliamps.
Won't even keep your phone battery charged.
That type of panel needs to be at least 50watts to be effective.