# Solar panels



## 88916 (May 10, 2005)

Hi all
anyone know about or have used a small solar panel that sits on top of the dash, plugs into the cigar lighter & trickle charges your battery whilst the van is layed up in the winter. I find that my alarm system gradually drains my battery after a few weeks.
Im sure I saw one reviewed in MMM some time ago I think it cost about £20



mike. b


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## 88860 (May 9, 2005)

*Solar Panels*

Has anyone got some basic information to new comers about solar panels. What are the pros and cons and how does one instal them. Can any one reccomend a manufacture. Are they really cost effective. Is their use solely limited to summer. ?


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## dodger148 (May 9, 2005)

Have a look at http://www.leisurepower.co.uk/acatalog/Solar_Advice.html

We have had a small 17watt panel for around 15 years and it has done what we ask it, keep the leisure battery topped up after use the previous night. Now it doesnt do it as quick as the 50watt plus panles you see on the top of vans but there again it was under 100GBP and has served us well.

When we tried the vehicle battery top up thing cos of alarm drainage during winter months it blew a fuse in the cigar lighter socket which we found out was due to the panel being "too big" for that purpose. The small ones you mention do work and for the small price they cost are handy.

They work on "Light" not the sun so will work all year round its just they dont work as well in lower light levels than in bright light and yes we use our one all year. I dont like drilling van bodies so kept to the system we had with the caravan, wire a socket accross the leisure battery and plug it in as needed, either sat outside the van or in the window


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## 89425 (May 23, 2005)

My wife is a bit of a greeny and wanted a solar panel for our van. Not being one to waste money if I can help it, I had to explain that it would not be of any benefit to us. And this is where others, perhaps not the above should look at their own personal circumstances. We use our vehicle every day so our batteries should stay charged without the aid of a solar panel. Though we are currently having a problem with poor charging of the leisure battery, that’s a problem associated with vehicle alternators not being capable of charging leisure batteries properly, but I’m addressing that problem. Back to solar panel, if your in the habit of not using your vehicle on a regular basis and leave equipment switched on to drain the batteries, perhaps you do have a need for a solar panel. However if you don't have any thing draining power and leaving your vehicle parked up at home for long periods, why not remove the battery and keep it at home? A lot cheaper.

Now obviously there are cheap solar panel around to plug in to the cigarette lighter, but if your going to pump some serious money into fitting solar panels, you need to know what size to get in order for them to fill your requirements.
To establish what power output you need for ‘topping up’ or replacing the power used the evening before, you'll need to know what your loads/drainage is before hand. You can do that by connecting up a small scale ammeter which is capable of giving a reading +-0.5 Amp at about 5 amps. This will establish your non usage loads like alarms clocks etc. then multiply that by the voltage will give you watts, we’ll call this ‘X’ watts. You then need to know what additional power usage to cater for, like lighting, pumps, TV’s etc. You can simply see what the manufacturers have stamped on them to establish their loads. If none is available, you’ll have to carry out some tests using an ammeter. Do remember alarms and the like consume ‘X’ watts every hour for 24 hours, however lights, pumps and so on may only use ‘Y’ watts for 2 hours or so every 24 hours.

From your investigations you come back with say X watts which is every hour per day. So usage is X times 24 = total power use.
Y watts is limited use, so Y times usage time = total power use.
The above we’ll add together and call it ‘Z’ watts

Lets say you come back with a figure of say an unlikely 10,000 watt (10KW). Which does not mean you need a 10,000 watt solar panel as your load is consuming 10,000 watts over a 24 hour period. 

I’m sure most people are aware solar panels more often than not only produce a small percentage of its rated output this time of year especially in the UK. But lets assume its output is 10 watts (that would be per hour). That 10 watts is ONLY while the sun is out. So lets say it gets 10 hours of good light. In that 10 hours it has to generate enough power to restore 24 hours consumption. Therefore 10 hours times 10 watts = 100 watts which would in this case be far too low. With our Z watts (10,000 watts), this needs to be replaced within (or hopefully less, especially taking in to account clouds and poor light) the 10 hours available sunlight. So 10,000 watts divided by 10 hours light = 1,000 watts. Therefore you’ll need a 1,000 watt solar panel. May I reiterate all the figures are for example, and should not be taken as a sound figure.

As pointed out the figures used are for example only as I haven't got a calculator to hand for the calcs or the rated outputs or efficiencies of the solar panel. I am not saying the way I have worked out the figures are correct for solar panel, but you get the general idea. There may also be glaring errors, so get back to me if there is or you need further clarification or help.
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## autostratus (May 9, 2005)

Sorry to be so bold but aren't we talking about two different things in the same topic ie engine battery and leisure battery.

While charging the vehicle battery from the engine will also usually charge the leisure battery I'm told it doesn't follow that charging the leisure battery will also charge the engine battery.

We are able to keep our van at home and connect up to mains to keep the leisure battery topped up. In order to keep the vehicle battery topped up we have had fitted a 'Battery Master' which transfers power from the leisure battery. It was fitted by VanBitz ( www.vanbitz.com ) when they fitted our alarm system.

Gillian


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## 89425 (May 23, 2005)

Hi Autostratus,

The original heading is Solar Panels, so in that theme of information I have tried to give a fuller picture on the use of solar panels. I have also given examples of how to calculate the power consumption on a vehicle to establish whether the panel you intend to purchase will be large enough for its intended use. Also its worth pointing out that some people don't have a second battery (usually, but not always a ‘leisure’ battery) so the text would still be fully relevant. The information was given in good faith to help people understand their vehicle and the fitment of solar panels without the need to pay somebody else, or at the very least give them enough information so they have a better understanding before they approached someone else. Everything I have mentioned is fully relevant to solar panels, whether it be leisure batteries, vehicle batteries or vehicle alternators.

Further to your comments, whilst the engine does charge the vehicle starter battery, it does also ‘sort of’ charge the leisure battery at the same time, providing the appropriate circuitry has been fitted. Like it or not, normal vehicle alternators or not capable of charging leisure batteries efficiently as a higher voltage is required. What you have been told is correct that normally, by charging the leisure battery doesn’t charge the vehicle battery, however as charging systems are getting increasing complicated in order to cope with a variety of equipment like solar cells, wind generators, mains hook-up supplies, numerous batteries of varying capabilities and capacities, so its inevitable there are systems that does charge the vehicle battery without the aid of the engine.

Solar panels on the dash and plugged into the cigarette lighter (providing the ignition doesn’t have to be switched on) will only charge the vehicle starter battery, unless the leisure battery has been incorrectly wired, or there has been an attempt to use diode for a split charge system. The dash board solar panel system may be wholly satisfactory to the original poster, however I have now given a fuller picture of which he may wish to consider in the long term.

Autostratus, perhaps I should have walked on by and not given such an extensive explanation of solar panels in general. May I kindly ask for a description of your vans electrical installation and the ‘Battery Master’ unit from Vanbitz as I would like to know more. 
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## 89425 (May 23, 2005)

Hi Autostratus, 

Further to your vans system, did VanBitz supply you with a wiring diagram or a circuit diagram of their unit which you could post on the group please as their explanation is a bit too general. I like to know what I getting for my money.
.
.


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## 88860 (May 9, 2005)

*Solar Panels*

Thanks Averywildwildcamper & autostratus God you have both given me something to think about, what do either of you know about invertors any similar guidance please. Thanks


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## 89425 (May 23, 2005)

I know a bit, but it may be best to start a fresh thread so that the topic can be easily found in the directories.

Invertors is, or can be a wide subject, so a bit more info like your intended use, available power(12V and amps).


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## autostratus (May 9, 2005)

Averywildwildcamper said:


> Autostratus, perhaps I should have walked on by..............
> .
> .


Certainly not, Steve and I'm sorry if I gave that impression. It was not intended. Your explanations are welcomed by me and I'm sure by others.

With regard to the our van's electrical installation I'm not sure what information I can give you.
We have a Boxer based motorhome with the standard battery installation and a seperate leisure battery with zig unit.

The Battery Master is wired into the leisure battery and allows it to top up the vehicle battery but prevents the leisure battery from taking power from the vehicle battery.

I haven't a clue how it works only that it does.
Sorry I can't be more helpful.


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## 89425 (May 23, 2005)

*Checks to see what is being charged*

This applies not only to solar panels, but also 'on board' and external/portable battery chargers.

First of all you'll need a test meter. Its now possible to purchase a cheap test meter, usually digital for about £5 - absolutely crazy as I was initially paying ten times that when they first came on the market. Try your local cheapo shop or somewhere like www.maplins.co.uk

IMPORTANT On your meter, there are usually several options for measuring electrical thingies! Voltages (the potential difference of two test points) on vehicles are DC (direct current) which will be indicated by either 'DC' or a short horizontal line over the top of a dashed line. AC (alternating current) is what your house is fed with from the central electricity generating company. Current is Amps (A or mA - milliamps), again there is probably a choice of two options, AC and DC. These are measured by connecting your meter in series with your load and supply. With cheap meters, they are not usually capable of measuring anything more than an Amp or so, so avoid this. By the way, if you connect your meter across the battery terminals whilst the meter is set to measure current it will be fit for the bin after its gone 'POP', unless it the meter has been equipped with a separate terminal. Finally most meters have the option to measure resistance (Ohms) which is normally indicated by an upside down horseshoe symbol (well its upside down to me as the luck runs out of horseshoes if nailed up the wrong way!). The resistance test is how well two items are connected together, therefore the connection between a battery terminal and the lead connected to it should be zero ohms, if it does have a resistance it will generate heat and breakdown, also it will cause a loss in voltage. Again it should be noted that your meter will probably die if you connect it across a voltage whilst set on ohms.

1.	First make a note of the battery voltages with no engine running and no solar panels or chargers running, plus check everything is switched off, small interior lights won't hurt .

2.	To establish whether your batteries are isolated when parked up (the most common and recommended situation), carry out an voltage check first. This is done by having one test meter lead on the + (positive) terminal on one battery and the other test lead on the + terminal of the other battery. Ideally you should have a zero reading (like as if the meter is not connected to anything). providing you have a zero reading, reset your meter to measure resistance/ohms and do the same test again. This time you should have an open circuit reading of maximum ohms (like as if the meter is not connected). If you do have a low resistance, you have got a problem where your house equipment is also going to drain your vehicle starter battery. Its probably worth reversing the test leads to see if you get a different reading, in this case there is probably some electronics involved in the connections between house/leisure and vehicle starter batteries.

3.	Then start your engine and take another set of voltage readings. These should be higher than the first. If not you've got problems! Next stop your engine, and plug in or switch on your solar panel (I'll state the obvious, and say this should be done on a bright day - not at night!), check your battery readings, these again should be higher than your first initial readings, however you may find that the readings are only higher on one battery. This will indicate what is being charged by your solar panel. It is a possibility in some cases that no increase in voltage is detected (especially if your solar panel is connected via the cigarette lighter socket) until the ignition switch is turned on (providing the panel is powerful enough), in this case I recommend a rewire of your circuits. After the test, and before proceeding to the next stage, isolate or turn off your solar panel.

4.	This test is similar to the solar panel test, but using an onboard battery charger. Check your charger/hook-up is connected and switched on, then check the battery readings, which again should be higher than the first initial readings. It will also indicate which batteries are being charged. This test also gives the opportunity to check any switching options for charging on any auxiliary electrical panels in you vehicle so that you understand exactly what they do when you operate the switches. After the test, and before proceeding to the next stage, isolate or turn off your solar panel.

5.	As a final check, I would use a normal battery with flying leads and crocodile clips. Connect the charger up to your vehicle battery and power up the charger. Take the battery readings, in most cases there will be an increase in voltage only on the vehicle starter battery, however if there are special circuits on your vehicle, you may find there is an increase in voltage on your leisure/house battery. I would also try this test again by connecting the battery charger to the leisure/house battery to see if there is any back feed or leakage!

Obviously if you have any strange results from your tests that don't really comply with the above, it would be best to post them here so we can work through them together. By all means email me (especially if your not sure), but do also post your questions here (minus any embarrassing bits) so others benefit from the knowledge/experience. Hopefully all the above makes sense, but as I tell my students if it doesn't make sense or I have made errors, let me know so I can put it right.


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## Anonymous (Nov 10, 2000)

We also had the problem of Cobra alarm draining the engine battery. We also wild park in Scotland, so no hook up. We use van on occaisional weekends through winter so don't want to remove battery. We solved this by having 120watt solar panel fitted on roof (£700) at the Peterborough show (forget firm's name but based near Nottingham). We also put two new leisure batteries on. Because the panel is quite big it produces sufficient power, even in winter, to keep batteries charged. On really grey days when nothing is produced there is still enough stored in the two batteries to see us through.

Like Autostratus, we have a Battery Mate, so the leisure batteries keep the engine battery sufficiently charged, counteracting alarm drain. And it has worked; this winter it has never let us down. In summer, everything is usually re-charged by the time we get out of bed. Probably more power than we need, but it does mean we also get through the lean winter times.


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## dodger148 (May 9, 2005)

I may have missed something in the threads, but when playing with your multi-meters if you check voltage across the solar panels terminals dont be surprised to see a higher voltage than 14v
By the time the flow gets to the battery everything is ok


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## 89425 (May 23, 2005)

dodger148 said:


> if you check voltage across the solar panels terminals dont be surprised to see a higher voltage than 14v


If the open circuit voltage was less, it wouldn't charge your battery. The 'charger' voltage has to be higher, otherwise as I said above, it wouldn't charge your battery.


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## MOTORHOMER (May 9, 2005)

mikethebike said:


> Hi all
> anyone know about or have used a small solar panel that sits on top of the dash, plugs into the cigar lighter & trickle charges your battery whilst the van is layed up in the winter. I find that my alarm system gradually drains my battery after a few weeks.
> Im sure I saw one reviewed in MMM some time ago I think it cost about £20
> 
> mike. b


Hello Mike

I have two of these one in the car & one in the van. Personally I dont think one that size is much good. I am not a techie person but I feel I wasted my money.

Elizabeth


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## 88916 (May 10, 2005)

Hello Elizabeth
Thank you for your reply, I think I will have to get something a bit bigger (and more expensive) this only happens in the winter when the van is laid up so I think the battery is ok.


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## 89555 (May 28, 2005)

*solar panel roof fixing*

Hi, what are the pro and cons of fixing a solar panel to the roof of a motor home,I have the panel and the adhesive, but I am a little wary of doing this job myself,without the advice of others,can anyone advise


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## 89425 (May 23, 2005)

Hi Jack,

I would NOT glue it to your van. What if it breaks? What if you want it for another van? Etc etc. You should be able to get a fixing kit to secure the panel without gluing, but yo will probably have the choice of gluing or screwing the bracket to your van. When screwing it to your van, don't use too small diameter screws, or too long, do use a good dose of non-setting mastic to avoid any ingress of moisture.
____________________________________________________
*Steve 
aka A very wild....wild camper*
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Click here for my van website!
.









_I do like a bit of feed back to my posts please_
____________________________________________________


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## 89555 (May 28, 2005)

*solar panel roof fixing*

Steve many thanks for very sound advice. I can see the reason for not gluing,but this was the advice from the dealer of the solar panel,he even sold me the adhesive!the old story of a fool and his money!!


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