Solar panel just to keep battery topped up

[McLosi]

So I'm moving our van from an area that has power to a stores with no power.
The alarm would be set, bit nothing else will be running. What is a simple solar panel that I can get just to set up when not in use to keep the battery charged please?

 

[Jcloughie]

A cheap 8-10 watt panel connected directly to the battery is, I am told, fine without a regulator and will not overcharge, especially in the winter.

It could go in a roof light. Or on the roof but would need some fixing in case the wind gets up.

Google my suggestion to check first.

John

 

[Mandarin]

A cheap 8-10 watt panel connected directly to the battery is, I am told, fine without a regulator and will not overcharge, especially in the winter.

It could go in a roof light. Or on the roof but would need some fixing in case the wind gets up.

Google my suggestion to check first.

John

Exactly what we used in the past before we got a fixed solar panel. 10 watts just kept the battery topped up nicely without the need for a regulator.

We had it loose in the front window which just happened to be south facing.

 

[McLosi]

Exactly what we used in the past before we got a fixed solar panel. 10 watts just kept the battery topped up nicely without the need for a regulator.

We had it loose in the front window which just happened to be south facing.

Something like this?
ECO-WORTHY 10Watts Solar Panel Module for 18 Volts Battery Charger for Camp and off-grid Ligthing Applications L02P10-N-1 https://amzn.eu/d/5QaMp29

Literally just straight to the pos and neg of the battery?

 

[Mandarin]

Something like this?
ECO-WORTHY 10Watts Solar Panel Module for 18 Volts Battery Charger for Camp and off-grid Ligthing Applications L02P10-N-1 https://amzn.eu/d/5QaMp29

Literally just straight to the pos and neg of the battery?

Yes, thats what we used. Just make sure it's aimed at the midday sun at a good angle.

 

[JTQ]

Yes, thats what we used. Just make sure it's aimed at the midday sun at a good angle.

Which in the winter, the angle is way nearer vertical than horizontal, thankfully as the plastic windows are then that bit less energy attenuating.

My own views though has to be something bigger than 10Watts, with a good low parasitic loss controller, that overcomes any risk of overcharging but gives a better chance of adequately charging.

 

[Guzzilazz]

I agree bigger than 10W, and needs AT LEAST to have a diode to stop "parasitic drain" - where the battery would discharges through the panel when it stops charging.
Better to put in a 40W panel with a PWM controller (which obviates properly and drain problems)

 

[McLosi]

VOBOR 40W Solar Panel Kit - 40W 18V Monocrystalline Silicon Solar Panel with Charge Controller 20A Charge Controller + Connection Line+Suction Cup for Motorhome RV Boat Shed Camping https://amzn.eu/d/hBDAG9I

So something like this? Or is there something better that won't break the bank? Happy to spend the money as long as it's what I need
Thanks for all the replies btw.

 

[JTQ]

For panels located inside our van window going much bigger than 40Watts inevitably introduces the risk of the mouldings within the plastic window or the window frame throwing shading onto the panel. This potentially can drastically diminish the "performance" of the panel.

In respect to the suggested Vobor panel I see no specification on the included controller so its "parasitic" losses, ie its self powering drains working and resting, these vary, usually with quality and that tends to relate to its purchase price.
I have over the years tested some only to find they as said vary, one drained more than over 24 hours than the panel achieved even on a good day!
Buying "blind" you take a risk, that might pan out well or otherwise; I buy panels and controllers separately having studied their specifications, not buy blind.

A decent quatlty but budget controller this having just 6mA self drain.

Spec sheet

 

[Raywood]

We have a 20 watt panel which works for us. If you have an alarm fitted which draws power from the battery you might need a bigger one.

 

[McLosi]

For panels located inside our van window going much bigger than 40Watts inevitably introduces the risk of the mouldings within the plastic window or the window frame throwing shading onto the panel. This potentially can drastically diminish the "performance" of the panel.

In respect to the suggested Vobor panel I see no specification on the included controller so its "parasitic" losses, ie its self powering drains working and resting, these vary, usually with quality and that tends to relate to its purchase price.
I have over the years tested some only to find they as said vary, one drained more than over 24 hours than the panel achieved even on a good day!
Buying "blind" you take a risk, that might pan out well or otherwise; I buy panels and controllers separately having studied their specifications, not buy blind.

A decent quatlty but budget controller this having just 6mA self drain.

Spec sheet

Thank you for this. So with that controller, could I use pretty much any panel?

 

[JTQ]

Thank you for this. So with that controller, could I use pretty much any panel?

Not quite, but effectively "yes" if that's not too contradictory!

What it must be is one designed for PWM charging 12 volt systems, this means that its "Maximum power voltage" needs to be around 18 to 22 volts. That is not one of the higher voltage ones "optimised" for use with MPPT technology controllers, and or higher voltage battery systems.

Though not a recommendation as its not a panel I personally know, the following, say their 30Watt version of this mono crystalline panel, has the right characteristics.
LINK

PWM being Pulse width modulation, the technology of the suggested breed of controller.
MPPT, Maximum power point tracking, a technology if done well that potentially can yield a bit better performance of panels optimised for use with them. An asset in weak lighting particularly, but doing with similar levels of quality componentry, is more expensive.

Edit: The controller identified, at a push, would cope with an upto 50Watt panel, but then the panel size would likely be getting too large to use internally without shadows, and things therefore get counterproductive. No such issue if outside free of shadows.

 

[McLosi]

Not quite, but effectively "yes" if that's not too contradictory!

What it must be is one designed for PWM charging 12 volt systems, this means that its "Maximum power voltage" needs to be around 18 to 22 volts. That is not one of the higher voltage ones "optimised" for use with MPPT technology controllers, and or higher voltage battery systems.

Though not a recommendation as its not a panel I personally know, the following, say their 30Watt version of this mono crystalline panel, has the right characteristics.
LINK

PWM being Pulse width modulation, the technology of the suggested breed of controller.
MPPT, Maximum power point tracking, a technology if done well that potentially can yield a bit better performance of panels optimised for use with them. An asset in weak lighting particularly, but doing with similar levels of quality componentry, is more expensive.

Haha ok I understand. Think I know what to do as well. Thank you for all your help.

 

[trevormonty]

For solar panel to produce its rated output has to facing sun directly and clear skies. Winter sun has lower output as its lower angle means it travels through more atmosphere which tends to be a bit more hazy in winter due to smoke particles.

 

[Anseo]

McLosi,

Can I suggest you look at something else that I am sure that you can have confidence in buying and using.
I have purchased solar energy related equipment from the supplier I link to and I have trust in the quality of products they have on offer, they are not my sole supplier so I think it fair to say I can make comparisons on fitness for purpose.


For a charge controller, here is a true MPPT, it's origin is Epever, a quality brand that will stand you in good stead should you wish to expand your solar array in the future.
Check it out here:

For solar panel (Victron - highly regarded) here is a 20 watt panel, they have 40 watt option also.
Click on this link:

 

[McLosi]

McLosi,

Can I suggest you look at something else that I am sure that you can have confidence in buying and using.
I have purchased solar energy related equipment from the supplier I link to and I have trust in the quality of products they have on offer, they are not my sole supplier so I think it fair to say I can make comparisons on fitness for purpose.


For a charge controller, here is a true MPPT, it's origin is Epever, a quality brand that will stand you in good stead should you wish to expand your solar array in the future.
Check it out here:

For solar panel (Victron - highly regarded) here is a 20 watt panel, they have 40 watt option also.
Click on this link:

Thank you, looks good. Will keep in mind when I purchase next month.

 

[JTQ]

For solar panel to produce its rated output has to facing sun directly and clear skies. Winter sun has lower output as its lower angle means it travels through more atmosphere which tends to be a bit more hazy in winter due to smoke particles.

Whilst much of that is correct and winter here tends to have
more overcast conditions, the yield on those very cold crystal-clear days can be remarkably high. The technology works better the colder it is, plus, if cold enough moisture related haze is irradicated by the dryness of the atmosphere, hence the clarity mentioned.
Though here at least in my southern part of the UK experience with camping related PV solar for much other than the minimum requirement being sort by the OP is disappointing unreliable with practically sized panels.

 

[Guzzilazz]

My experience with solar is marine based where my boat was on a swinging mooring (therefore no mains available). I had a 330 AH AGM Battery bank (3x110AH). The first installation was 2x 45W Panels, through a PWM controller, and this kept that battery bank very happy ALL YEAR ROUND without resorting to a mains charger. I did upgrade in 2016 two 2x150W panels through an MPPT Controller, and that was enough to run a compressor coolbox 24/7 April - October... In general the panels were pretty close to horizontal and with the waay the boat lay only one panel was facing south at any one time.

Summary? If you divide the panel total wattage by 3 for the average caravan leisure battery that will give you sufficent to cope . So 30 will do, 100W will enable you to run stuff.

 

[Buckman]

We have a 100w panel on our caravan, but with the weather since the 8th Dec the battery level has been declining. It was 12.6v on the 8th and has declined down to 12.2v yesterday. We have hardly seen any sun in the past week or two.

 

[JTQ]

That paints the picture of a system with some significant battery drain, Alarm?

 

[Buckman]

That paints the picture of a system with some significant battery drain, Alarm?

We do have a tracker and the alarm switched on. Battery is over 6 years old, but is an AGM battery so hopefully will recover. I think it is a Yuasa 100ah battery?

 

[trevormonty]

McLosi,

Can I suggest you look at something else that I am sure that you can have confidence in buying and using.
I have purchased solar energy related equipment from the supplier I link to and I have trust in the quality of products they have on offer, they are not my sole supplier so I think it fair to say I can make comparisons on fitness for purpose.


For a charge controller, here is a true MPPT, it's origin is Epever, a quality brand that will stand you in good stead should you wish to expand your solar array in the future.
Check it out here:

For solar panel (Victron - highly regarded) here is a 20 watt panel, they have 40 watt option also.
Click on this link:

While MPPT are more efficient than PWM for price difference (£39 vs £5) be better offer spending difference on larger panels especially for installations <200W.

 

[JTQ]

The focus here as the thread title is "Solar panel just to keep battery topped up"; getting up to a 200Watts system is rather an overkill IMO and experience, but will I concede probably achieve it.

Should it be envisaged here as an internal arrangement that could have its own challenges.

 

[McLosi]

The focus here as the thread title is "Solar panel just to keep battery topped up"; getting up to a 200Watts system is rather an overkill IMO and experience, but will I concede probably achieve it.

Should it be envisaged here as an internal arrangement that could have its own challenges.

I don't really understand the difference between the PWM etc.. is what you suggested still a good idea? Minimum on I would imagine is the alarm. Max would be alarm and a rodent deterrent which I think, minimum draw but can find the box to get the exact amount.

 

[Gafferbill]

....bear in mind if your caravan storage is local to your home then a second battery could be a solution to keeping an alarm tracker working. You can buy a new 12volt battery for £40 .
You could charge a battery at home and swop as often as necessary.