Leisure Battery

[Landscaperchris]

Hi Folks

Newbe to this forum and looking for some advise

Currently we have a Bailey 625 kept in storage

Thinking of buying a cheap solar panel to place on the dashboard to decrease the occasions the leisure battery needs charging on mains.

Can I just connect the croc clips to the battery or will I need to disconnect the existing cables.

 

 

[sshortcircuit]

You can croc direct on to the leisure battery but doubtful if you would get any reasonable charge out of a dash mounted solar panel. My opinion only, as I have 90 watt panel on roof and have no problems.

[Derek Uzzell]

Welcome to the Out&AbouLive forums, Chris.

 

What you are proposing was discussed in this 2011 forum thread.

 

http://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Dashboard-solar-panels-/22562/

 

and there’s a more recent discussion here

 

https://www.motorhomefun.co.uk/forum/threads/will-a-solar-panel-charge-a-battery-through-a-windscreen.140989/

 

Received wisdom is that small cheap solar panels (example here)

 

https://www.justkampers.com/sol10-111161-ring-dashboard-solar-panel-1-5w.html

 

won’t be adequate and, consequently, won’t provide value for money.

 

A significantly larger panel (say a portable folding panel) will be much more effective, but it will also be significantly more expensive. As sshortcircuit has said, you might be better to opt for a ‘proper’ solar system involving a roof-mounted panel that you can also benefit from when your motorhome is not in storage.

[aandncaravan]

Chris, In the middle of June a 100watt Solar Panel generates about 5amps from 05:00 through to about 20:00 (around a 15 hour Solar Day) so can generate 5amps x 15 hours = 75Ah a day

 

The end of September will see the Solar day shorten down to around 8 hours, giving a harvest of about 40Ah a day

 

In mid Winter the same Solar panel will average about 1amp from 10:00 to 14:00 (around a 4 hour Solar Day) = 1a x 4 hours = a very poor 4Ah a day.

 

Yet the average Motorhome, with good batteries, needs about 8Ah a day to keep both Starter battery and a twin habitation battery setup charged up.

 

 

You can see that a 10watt Solar panel might give a little bit of charge in mid Summer, but not be very useful outside that time.

 

Even a 300watt Solar setup will be lucky to give more than 16Ah a day in mid December.

 

 

Note that the above Solar figures are based on a Sunny day for a vehicle located on the South Coast of Cornwall.

The same set-up in Thurso, NE Scotland will generate about 30% less on a Sunny day.

See - http://www.aandncaravanservices.co.uk/solar-panels.php

 

Obviously overcast skies or Snow will seriously reduce Solar gain still further.

 

 

If you buy one, suggest you wire it through a Wattmeter (about £7 on ebay) which will record the daily Ah figure so you will be able to see exactly what it generates. It will also display Volts and amps, etc.

The Wattmeter may help you point it in the best direction/Location for optimum gain.

 

 

May I suggest that the Starter battery running flat is likely to be a bigger issue than the Leisure battery, especially if the Vehicle Door Alarm/immobiliser is 'Set' when you lock up.

 

 

[spospe]

aandncaravan - 2018-03-13 9:58 AM

 

Chris, In the middle of June a 100watt Solar Panel generates about 5amps from 05:00 through to about 20:00 (around a 15 hour Solar Day) so can generate 5amps x 15 hours = 75Ah a day

 

 

I have never seen anything like this in 10 years of using flat mounted solar panels. A flat mounted 100 watt solar panel will produce circa 5 amps for the hour around midday when it is in full sunlight, much less when in shadow (even partial shadow) and less still when the cloud coves the sun and / or it is raining.

 

My rule of thumb is that with a flat mounted panel you can discount the two hours after sunrise and before sunset, which means in the UK a maximum of 12 hours of useful sunlight in midsummer and only 4 in midwinter (pro-rata between those times).

 

The maximum daily yield in June in the UK, given uninterrupted sun from sunrise to sunset (with a flat mounted 100 watt panel) will only be about a half the figure quoted, say, no more than 40 a/h input to the leisure battery. Given that lead-acid batteries are about 70% efficient, that will translate into about 30 a/h of actual stored energy.

 

My figures are based on what I have personally experienced, it may be possible to exceed then on occasion, but measured over time, they are a good guide to what is actually achievable.

[plwsm2000]

How do you measure how much power you could be generating though? Unless you are drawing ALL of the available power from the panels for the whole day, it seems to me that you cannot know how much the panels are CAPABLE of delivering (you only know what you are actually drawing from them).

 

If your batteries are fully charged and there is no other significant demand on your 12V system, you may only be demanding a few watts from the solar controller. Even on a brilliant sunny day and the panels are capable of providing 100W or more, the controller will only draw enough power from the panels as it needs.

I guess on a cloudy/overcast day you could be using all of the available power, but probably not always on a sunny day.

[spospe]

plwsm2000 - 2018-03-13 6:41 PM

 

How do you measure how much power you could be generating though? Unless you are drawing ALL of the available power from the panels for the whole day, it seems to me that you cannot know how much the panels are CAPABLE of delivering (you only know what you are actually drawing from them).

 

 

Some solar panel controllers, such as the Steca PR series will show how much power is being delivered to the battery. This does depend on how the vehicle is wired and so the facility may not be available to all users. It is perfectly true that on a bright sunny summers day, with the panel in full sun all the time, far more power will be potentially available than can be either used or stored (because the leisure battery is full) and in such circumstances it goes to waste. This is one of the sad things about solar panels, namely that at the time of maximum abundance, demand tends to be quite low, unlike winter use when the opposite applies.

[aandncaravan]

spospe - 2018-03-13 5:05 PM

 

aandncaravan - 2018-03-13 9:58 AM

 

Chris, In the middle of June a 100watt Solar Panel generates about 5amps from 05:00 through to about 20:00 (around a 15 hour Solar Day) so can generate 5amps x 15 hours = 75Ah a day

 

 

I have never seen anything like this in 10 years of using flat mounted solar panels. A flat mounted 100 watt solar panel will produce circa 5 amps for the hour around midday when it is in full sunlight, much less when in shadow (even partial shadow) and less still when the cloud coves the sun and / or it is raining.

 

My rule of thumb is that with a flat mounted panel you can discount the two hours after sunrise and before sunset, which means in the UK a maximum of 12 hours of useful sunlight in midsummer and only 4 in midwinter (pro-rata between those times).

 

The maximum daily yield in June in the UK, given uninterrupted sun from sunrise to sunset (with a flat mounted 100 watt panel) will only be about a half the figure quoted, say, no more than 40 a/h input to the leisure battery. Given that lead-acid batteries are about 70% efficient, that will translate into about 30 a/h of actual stored energy.

 

My figures are based on what I have personally experienced, it may be possible to exceed then on occasion, but measured over time, they are a good guide to what is actually achievable.

 

 

Spospe, As the last responder notes, much of the time your system will not be working flat out.

 

I did write :

 

"Note that the above Solar figures are based on a Sunny day for a vehicle located on the South Coast of Cornwall. The same set-up in Thurso, NE Scotland will generate about 30% less on a Sunny day".

 

 

Clearly trying to show the maximums achievable with a 100w panel so the OP can work out the best a Dash mounted 20w, or whatever is planned, might achieve.

 

With you being based near Manchester that will clearly have a significant impact on your observations, as will the use of the usual Stecca controller.

 

 

 

 

 

 

[bootlucy]

Hi all, I recently bought a 6 watt solar battery maintainer from Halfords with the idea of keeping the leisure battery topped up in my Bailey 635 m/h. I connected it directly to the battery using the crocodile clips

provided and a month later the control panel is showing 12.8 volts which I think is an improvement on before. Hope this helps

[aandncaravan]

Bootlucy, did you check the Control Panel in the night or during the day?

If it was during the day the Control Panel will be displaying the Solar panel charge voltage, which is not usually the battery voltage.

 

The real battery voltage may be much lower.

To demonstrate this, start your engine and watch the 'Alternator charging' raise the habitation battery voltage to 14.4v. Then try and use the display to 'see' the batteries previous 12.8v and you will find you can't.

All you will ever see on the Voltmeters display is the voltage at the battery terminals, which clearly isn't the same as the battery voltage.

 

Also, most batteries will hold an artificially higher voltage than their real one when first taken off charge, so you need to wait a few hours after charging is removed to allow them to settle down to see the batteries real State Of Charge (SOC).

That is why when checking a batteries SOC, it needs to be done several hours after any charging has ended, in your case several hours after sunset.

 

 

Many people make the same mistake, believing the battery is more charged than it actually is because they see the higher charging voltage of the Solar during the day when they are in the vehicle.

Read some of the threads on here from those with Solar panels and you will hear the same, "my 100w Solar is brilliant, because after running the TV all night the battery is up to 12.8v by 10:30 the next day", when the battery probably isn't. They are just seeing the Solar Regulator's voltage at the batteries which is probably still down at a discharged 12.2v.

 

 

A 6 watt Solar Panel might be able to deliver a theoretical maximum 0.5amps on a Sunny day in the middle of June, but behind a Vehicles Windscreen, mid March on a typical Spring day you will probably get less than 0.1 amp?

 

I would suggest that if you check the battery SOC at midnight tonight, it might not be that different to what you saw last year. It will depend on the battery you have and the setup.