Solar battery chargers. (1 Viewer)

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Charlie

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I’m thinking of getting one of those solar battery chargers. The ones that sit on top of the dash that supposedly keep the battery’s charged.

It’s for the starter battery on a Peugeot so a fairly big battery...

It’s the wattage that confuses me. I obviously want one powerful enough to charge the battery but not so big it causes damage ? I’m supposing one to powerful could overcharge or cause problems ? Unsure on that though !!

If these devices are considered worthwhile then recommendations on output and brands most welcome.

I simply keep forgetting to hook up the EHU !

Thanks.
 

Geo

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one of these devices is never going to charge a starter battery
what it will do is help maintain a fully charged healthy battery.
Even then the imput will have to be greater than any parasitic / natural drain.
20 watts should cope without damage anything bigger may need a controller to regulate the charge rate on sunny days
 

Lenny HB

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Total waste of space you need at least a 20 watt panel, even that will do sod all in winter, best to fit an 80 or 100 watt panel on the roof.

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Charlie

Charlie

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one of these devices is never going to charge a starter battery
what it will do is help maintain a fully charged healthy battery.
Even then the imput will have to be greater than any parasitic / natural drain.
20 watts should cope without damage anything bigger may need a controller to regulate the charge rate on sunny days


Sorry I should have said maintain or help maintain.

I think I may have a very slight draw. Even the BM1 must draw something ?
 
Apr 27, 2016
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The size of panel depends on the devices that keep running when the MH is parked. If the battery is totally isolated then even a tiny panel will keep it topped up. I used a 2.5 watt panel, stuck to the inside winscreen with suckers, with the MH pointing more or less south, very little shade. It worked fine for the starter battery, but the alarm was not switched on, and it had no tracker either.

A second 2.5 watt panel for the leisure batteries did not do so well. There are several things like frost protection valve, step, and heater controls that are permanently connected and draw a bit of current. The battery went down more slowly than without the panel, but I would have got a 10 watt panel, except that I'm not working away any more.

So a 20 watt panel as recommended by several funsters will do the job, as long as the panel catches the sun.

However, some MHs seem to draw quite a lot of current, what with super alarms and phone-powered trackers. That's apart from them having aftermarket gadgets that continuously draw power, like built-in USB sockets and some radio/sound systems that never seem to entirely shut down. So don't be surprised if you need a bigger panel than that.

I find that small panels can be left on space in front of the dashboard (I have an A-class), but I turn them face down for driving to avoid sunlight reflections.

As others have said, any panel above about 20 or 30 watts will need a solar regulator to avoid overcharging.
 
Jan 19, 2014
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Total waste of space you need at least a 20 watt panel, even that will do sod all in winter, best to fit an 80 or 100 watt panel on the roof.
Nonsense, my Optimate 2 is only rated at 800ma and it's not on half the time. Don't forget being an unfixed panel it can be pointed south and give near full power in winter. All the above depends on the continuous battery drain you have of course. My advice is based on a normal starter battery with no extra drains (y)
 
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Charlie

Charlie

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That being the case won't you just forget to plug in a dash top one :)

The idea behind those devices is we plug in and forget.......

I would never leave a full on charger permanently switched on. But these portable so called battery solar chargers we leave connected.

I’m just trying to work out if they work and if so which one is best.
 
Apr 27, 2008
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I use a 10w panel, about a foot square to keep my car battery charged up at the caravan storage if I'm away a long time. I just leave it on the roof plugged into the towing socket. I don't think they work so well if behind glass on the dashboard but I have seen them used like that.
 

Silver-Fox

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The idea behind those devices is we plug in and forget.......

I would never leave a full on charger permanently switched on. But these portable so called battery solar chargers we leave connected.

I’m just trying to work out if they work and if so which one is best.

Was just pulling your leg :)

Having said that if you plug in to ehu it won’t over charge the same as a solar plug in :)
 

Jaws

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I’m thinking of getting one of those solar battery chargers. The ones that sit on top of the dash that supposedly keep the battery’s charged.

It’s for the starter battery on a Peugeot so a fairly big battery...

It’s the wattage that confuses me. I obviously want one powerful enough to charge the battery but not so big it causes damage ? I’m supposing one to powerful could overcharge or cause problems ? Unsure on that though !!

If these devices are considered worthwhile then recommendations on output and brands most welcome.

I simply keep forgetting to hook up the EHU !

Thanks.
Most I have seen are really not fit for purpose.. Most produce a few watts at best,, Not even enough to compensate for an alarm
I am keen to know why you do not want a panel on the roof ?
It is really the correct answer to your dilemma
 
Jul 12, 2013
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I did have one of these chargers, it is still gathering dust in my garage, but whether coincidence or not I ended up replacing two engine batteries within a year when they failed so I have little or no faith in them.

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Apr 27, 2016
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I use a 10w panel, about a foot square to keep my car battery charged up at the caravan storage if I'm away a long time. I just leave it on the roof plugged into the towing socket. I don't think they work so well if behind glass on the dashboard but I have seen them used like that.
The glass will reduce the output, but only by 10% or so. Solar cells absorb visible light, and a bit of infra-red. They do not use the ultra-violet part of the spectrum, which is what the glass will block out.

Many solar cell assemblies are covered with a sheet of glass.
 

Geo

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TWO 10 w Panels maintain this motor mover set up nicely took a reading this am and its holding at 12.8
even in these cloudy conditions

20181203_154816.jpg
20181203_154827.jpg


20181203_153957.jpg
 
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Charlie

Charlie

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Most I have seen are really not fit for purpose.. Most produce a few watts at best,, Not even enough to compensate for an alarm
I am keen to know why you do not want a panel on the roof ?
It is really the correct answer to your dilemma

I don’t Need a solar panel on the roof. As I’ve said above we use sites only not Aires or wild camp.

All I need to know please is if these devices that are supposed to maintain the vehicle battery work.

If so a couple of specific questions please.

What size or output do I need for the large vehicle battery.

Is it possible to fit one to big or not. By that I mean IF I was to fit one to powerful would or could it bugger the battery.

I’m more confused than when I asked. Though I do appreciate everyone’s input even if I don’t understand some of it.

Thanks.
 

Lenny HB

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What size or output do I need for the large vehicle battery.

Is it possible to fit one to big or not. By that I mean IF I was to fit one to powerful would or could it bugger the battery.
A 20 watt panel should do the trip still small enough to go on the dash, big enough to keep it topped up in winter but it will need a regulator to stop it over charging in summer, a cheap £5 regulator will do.
 
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Charlie

Charlie

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A 20 watt panel should do the trip still small enough to go on the dash, big enough to keep it topped up in winter but it will need a regulator to stop it over charging in summer, a cheap £5 regulator will do.

Thank you .

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Jaws

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I don’t Need a solar panel on the roof. As I’ve said above we use sites only not Aires or wild camp.

All I need to know please is if these devices that are supposed to maintain the vehicle battery work.

If so a couple of specific questions please.

What size or output do I need for the large vehicle battery.

Is it possible to fit one to big or not. By that I mean IF I was to fit one to powerful would or could it bugger the battery.

I’m more confused than when I asked. Though I do appreciate everyone’s input even if I don’t understand some of it.

Thanks.

Then the answer is still no, as dash mounted panels are not big enough to do anything ( as said in my original answer )
It is not possible to fit a panel too big because:
What ever size is used the output to the battery should be controlled by a separate controller
A controller is not needed on the 'dash mount' panels as the output is about the same as sticking copper nails in a potato !
A panel big enough to do damage will fill the whole windscreen ( so needs to be used with a controller ) :)
 

Ivory55

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We have 80 watt on the roof and a vanbitz alarm on thevan and we still have to plug it in to the mains once a month to top up the batteries while it’s parked on the driveway.
 

TerryL

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I used to use a couple of the briefcase type panels left on the dashboard and facing south whilst the van was in storage. The best they ever put out was 1 amp (I measured it) apiece but they maintained the vehicle battery enough for me to be able to leave it for up to 6 weeks and still be able to start it. I do have a small amount of discharge but I can reduce even this by turning off the habitation control panel. Unfortunately they were no use for the leisure battery which accordingly suffered. Just be aware that you won't be able to connect them via the dashboard cig lighter sockets which are not live with the ignition off, unless you make a small adaption.

Now I have an 80 watt solar panel plus a battery master and never have to worry about the batteries.
 
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Charlie

Charlie

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After listening to the advice here I’ve decided not to bother with one of the devices I asked about..

But it raises a question..... There are literally dozens of said devices of the ilk ranging from ten quid Chinese ones to hundred quid branded ones..... I would imagine most of them get returned if they are as useless as members here say..

Anyway thanks everybody.
 

TerryL

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Don't know about getting returned; I'd guess the majority wouldn't bother and write the cost off to experience. That's probably why you can still buy them!

Mine did what I wanted, but they're now languishing in the garage, along with all the other "essential" junk I've bought over the years!

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Sep 23, 2007
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Good friend of mine has a small boat, with one battery that is used for starter and lights.
He hardly uses the boat and often found the battery wouldn’t start the engine.
Battery of take home and recharge. 3 years ago i bought a 7 watt panel of ebay. sits behind a side window and todate no flat battery.
 

DBK

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After listening to the advice here I’ve decided not to bother with one of the devices I asked about..

But it raises a question..... There are literally dozens of said devices of the ilk ranging from ten quid Chinese ones to hundred quid branded ones..... I would imagine most of them get returned if they are as useless as members here say..

Anyway thanks everybody.
They can and do work but it really depends on whether there is any load on the battery. If there is genuinely no discharge then a typical lead acid battery will self-discharge at a rate of about 5% per month. So as an example, a 100Ah battery would lose the equivalent of 5Ah - but that isn't 5 amps for an hour, it is less than a hundredth of an amp spread over the entire month.

So you can see to keep a battery already in good condition fully charged takes very little power.

The problem is knowing what other drains on power there are in the MH when you think everything is switched off.

I know from personal experience small panels of the sort you described have been used for long term storage of military vehicles stored in buildings with only limited light coming through panels in the building roof. But from memory (it was a few years ago) the vehicles didn't have any sort of clever electrics and there was no drain when they were switched off. The batteries might even have been disconnected from the vehicle systems.
 

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