Solar panel just to keep battery topped up

[McLosi]

....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.

Hhmm hadn't thought of this. Suppose just depends how often I'd need change it though..

 

[Buckman]

....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.

Add in the cost and hassle of travelling back and forth to the storage compound makes the solar panel cheap in comparison.

 

[JTQ]

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.

The difference in these technologies is the MPPT system as that designation implies keeps the panel output voltage as near to its "maximum optimum performance voltage" as the light's power can achieve, thus potentially improving the yield, panel rating for panel rating. It's a better system in that, but it is more expensive to make and benefits more with panels also optimised for it. The suggested Morningstar PWM controller is suggested as it is a known product, from one of the world most highly respected makers, albeit their most basic model, but it works and has a very low parasitic drain, important in the required duty with a low Wattage panel. My concerns borne out from a few tests I made are that there are some poor cheapo controllers out there, the best one can say of them is limited to the wording on the label looks impressive.

Checking what drains are there, and what current a panel can provide is interesting and constructive in decision making, if not essential.
THIS little cheapo gizmo is brilliant at finding these real-life values out, it plugs into the blade fuse that should be fitted in the batteries positive feed cable, the fuse being then refitted into its probe. Then switched on or not it completes the circuit, but if switched on also measure the current flowing and indicates whether it is flowing in or out. It can live there or be usefully put in your tool bag for any automotive 12 volt powering issues that you might need to investigate.

 

[Guzzilazz]

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.

Solar panels generate in daylight, and don't actually need sun. It probably indicates that your battery is on the way out...

 

[Guzzilazz]

The difference in these technologies is the MPPT system as that designation implies keeps the panel output voltage as near to its "maximum optimum performance voltage" as the light's power can achieve, thus potentially improving the yield, panel rating for panel rating. It's a better system in that, but it is more expensive to make and benefits more with panels also optimised for it. The suggested Morningstar PWM controller is suggested as it is a known product, from one of the world most highly respected makers, albeit their most basic model, but it works and has a very low parasitic drain, important in the required duty with a low Wattage panel. My concerns borne out from a few tests I made are that there are some poor cheapo controllers out there, the best one can say of them is limited to the wording on the label looks impressive.

Checking what drains are there, and what current a panel can provide is interesting and constructive in decision making, if not essential.
THIS little cheapo gizmo is brilliant at finding these real-life values out, it plugs into the blade fuse that should be fitted in the batteries positive feed cable, the fuse being then refitted into its probe. Then switched on or not it completes the circuit, but if switched on also measure the current flowing and indicates whether it is flowing in or out. It can live there or be usefully put in your tool bag for any automotive 12 volt powering issues that you might need to investigate.

MPPT is best with multiple solar panels, which are best connected in series to the MPPT Controller, then you get up to about 44V out of the panels, and the controller will operate as a smart battery charger...

 

[Buckman]

Solar panels generate in daylight, and don't actually need sun. It probably indicates that your battery is on the way out...

There is that possibility however caravan was under cover for about a week before we collected it. We have had the battery down as low as 6v and it has recovered quite well. but this was about 3 years ago. Yesterday at 1744 it was down to 12.1v.

We are going to the caravan on Saturday so will check if perhaps we left the 12v switched on as done that in the past.

 

[JTQ]

MPPT is best with multiple solar panels, which are best connected in series to the MPPT Controller, then you get up to about 44V out of the panels, and the controller will operate as a smart battery charger...

Agreed but here targeting only just a system "to keep the battery topped up", assumed in storage, I had not envisaged the OP was thinking of getting into a multi panel system.

 

[JTQ]

Solar panels generate in daylight, and don't actually need sun. It probably indicates that your battery is on the way out...

The specifics of what wavelength exploited depend on the panel, but direct radiation from the sun is always going to be better than reflected off the clouds etc.

 

[Gafferbill]

Add in the cost and hassle of travelling back and forth to the storage compound makes the solar panel cheap in comparison.

.....I assumed, perhaps wrongly, that people check their caravan (i.e. large investment) on a regular basis, so swapping batteries wouldn't be an extra cost. I also pointed out storage would probably need to be local.
I store at home at no cost, with caravan on ehu so I can check it every day.

 

[Buckman]

.....I assumed, perhaps wrongly, that people check their caravan (i.e. large investment) on a regular basis, so swapping batteries wouldn't be an extra cost. I also pointed out storage would probably need to be local.
I store at home at no cost, with caravan on ehu so I can check it every day.

We have a tracker on our caravan so can observe it from home although storage is 10 miles away.

 

[Hutch]

We have a tracker on our caravan so can observe it from home although storage is 10 miles away.

I thought you stored your van at the dealers getting repaired. 🤔

 

[Buckman]

I thought you stored your van at the dealers getting repaired. 🤔

LOL! It was only there for a few weeks. Over the past 6 years in total about 3 months on two occasions at the dealer. Most of those 3 months waiting for parts and winter so no real issue for us.

 

[McLosi]

The difference in these technologies is the MPPT system as that designation implies keeps the panel output voltage as near to its "maximum optimum performance voltage" as the light's power can achieve, thus potentially improving the yield, panel rating for panel rating. It's a better system in that, but it is more expensive to make and benefits more with panels also optimised for it. The suggested Morningstar PWM controller is suggested as it is a known product, from one of the world most highly respected makers, albeit their most basic model, but it works and has a very low parasitic drain, important in the required duty with a low Wattage panel. My concerns borne out from a few tests I made are that there are some poor cheapo controllers out there, the best one can say of them is limited to the wording on the label looks impressive.

Checking what drains are there, and what current a panel can provide is interesting and constructive in decision making, if not essential.
THIS little cheapo gizmo is brilliant at finding these real-life values out, it plugs into the blade fuse that should be fitted in the batteries positive feed cable, the fuse being then refitted into its probe. Then switched on or not it completes the circuit, but if switched on also measure the current flowing and indicates whether it is flowing in or out. It can live there or be usefully put in your tool bag for any automotive 12 volt powering issues that you might need to investigate.

Awesome. Bought one of those gadgets and I'll see what the actual draw is and then head off with your suggestions I think. Thanks for all your help.

 

[Mandarin]

.........

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.

Maybe, I simply speak from practical experience of three years of using a 10w panel in a caravan and 10 years in a boat. The van was a S2 valencia with alarm running.

The panel did include a diode to stop reverse draw but no controller and did no more than maintain a charge with only the alarm on.

Of course anything bigger than a 10w panel should have a controller, but we found the cheap and cheerful 10w panel adequate.

It's up to each to get what they feel is right.

 

[Guzzilazz]

Agreed but here targeting only just a system "to keep the battery topped up", assumed in storage, I had not envisaged the OP was thinking of getting into a multi panel system.

Exactly what I assumed, the MPPT reference was just general background solar info...