Freelander 1 Solar Chargin of Leisure Battery and more..Anyone done it?

So I've been looking at using solar panels to charge a leisure battery to use when I'm fishing/ camping mainly to power a fridge to keep the beers cold . This was nothing to do with the car, just a stand alone system. It's very doable with plenty of spare capacity (battery never draining more than 50%) for about £ 350 but to power an 85 w fridge (0.9 kW/ 24hr) I'd need two 90 Ah batteries and that takes up a lot of space.

Then I thought maybe just split charging is a better option so I searched this forum and found this post.

https://www.landyzone.co.uk/land-rover/leisure-battery-split-charge-or-towing-electrics.280940/

I have a tow bar with an electric hook up so thought maybe this is the route to go but I figured I'd still only get a maximum of 24 hours out of single 90 Ah battery and really I would still need two batteries. Also, I think it takes about 10 hours to charge a 90 Ah battery off the alternator which means I'd have to go driving (or run the engine) for 10 hours per day to keep the battery topped.

So then I thought how about using both as in the leisure battery charges off the alternator when the engines running but when I'm parked up the solar panels take over and keep the battery topped up. I figured I could then get away with only running the engine for a couple of hours a day to keep things topped up.

Thing is I'm not sure if that's even possible. Has anyone had any experience of this?

Fritz

I have a lot of experience with solar power generation and storage.
I use solar panels to charge a 12V 40Ah (just failed) SLA for my solar powered workshop lighting. I also charge my smart devices via the same battery. I have over 100 Watts of solar panels, split into groups, collecting the sun's energy from East (25watts), South (60 watts) and West(30 watts). This gives me the longest charge period possible throughout the day. I use my own PWM charge controllers, which are very efficient, so as to minimise losses at times when the sun is weak.

To power an 85 Watt fridge from solar, you'll need a several 100watt panels.
For example. In full sun, you could potentially get 600 Watt hours of energy from 1 X 100W panel (in full sun). In the same time span, your fridge will consume over 500 Wh of energy, giving you little extra power to charge the battery for the night when solar power isn't available. This is a best case scenario, which assumes full sun on the panel.

In reality, there's seldom full sun for 6 hours of the day, so to compensate for this, more panels are needed.

You'll also need sufficient reserves of capacity in the batteries to keep the fridge going when the sun isn't strong enough to power the fridge. Regardless of what solar installers say, when it's cloudy, the panel output drops to less then a 20th of the minimal full sun rating.

I'm building an off grid solar charged power station, simply to charge smart devices when camping, but running an electric fridge, is a whole different ball game.

A gas fridge is often better than an off grid electric fridge.

Thanks for the reply Nodge.

It is possible to generate enough to run the fridge 24 hours (I think) but I have conveniently ignored the effect of days with no sun.

Now that's quite a likely scenario for the UK but the fridge I have isn't very energy efficient. I know I can buy one that uses 1/3 of the power than the one I have so that's the eventual aim which then gives me spare capacity.

My solar calcs are below (please feel free to point out any errors as I'm new to all this).

The sun hours are the average UK sun hours from the beginning of July through to the end of September.

No. of Panels 2 no.
Individual Panel Rating 120 W
Total Panel Rating 240 W
Max. Individual Panel Amperage 6.67 A
Sun Hours 5.4 Hours
W per Day 1296 Wh
Losses (30%) 388.8 Wh
Usable per Day 907.2 Wh
Battery Voltage 12 V
Req. Controller Amperage (Min) 13.34 A
Amp hours 75.60 Ah
Max 50% Drain 151.20 Ah
Temp Adjustment (+11%) 167.832 Ah
Inverter Adjustment (95% Efficient) 176.67 Ah
No. of 90 Ah 12 V Batteries 2 no.
Run Time for 37.5 W (0.9 kW/24h) Fridge 24.19 Hours

What I'm hoping is that if I can dual charge (solar and alternator) the leisure battery then it'll give me enough power to use just one 90 Ah battery but I've not even begun to calculate that out yet. In fact I'm not even sure if it's possible.

I'm hoping that it would just be a matter of using a controller that can handle two power inputs. I know they exist for wind and solar (used on boats) so I'm assuming the wind could be replaced with the alternator.

Fritz

watching with interest!!!

I use one to keep me battery topped up when I don't use the car...Surprisingly does the trick...

Fritz said:

It is possible to generate enough to run the fridge 24 hours (I think) but I have conveniently ignored the effect of days with no sun

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You have to allow for non sunny days, and have some form of back up plans.

What battery will you be using? Different technologies have different charge/discharge efficiencies.
It's best to try to eliminate wasting energy by eliminating inverters. For instance it's better to have a 12 Volt 100 watt fridge, over an 85 Watt, 240 Volt fridge powered via an inverter stepping the power up. Remember that a battery Ah rating as measured at various discharge rates. For instance a large 110Ah deep discharge Pb battery could supply 110Ah over a 100Ah period, but only 90Ah if discharged over a 20 hour period. The higher the battery drain, the lower it's Ah rating will be. So running an inverter will drain the battery at a higher Ah rate, reducing its Ah rating considerably. These discharge characteristics are different for different chemistry batteries, LifePO4 being about the most useful to solar power storage and use, although definitely not a budget option.

Which panels you use and how they are situated will make a big difference to the useful power available from them. I like to get the longest period of energy generation from them, so have them facing in different directions, to collect the sun's energy as long as possible.
If you're around in the day, it's very beneficial to move the panels to maximise solar energy collection.

Also which charge controllers you use makes a difference to the system too. I personally prefer a simple PWM charge controller, which is energy efficient to run. You can use expensive MPPT charge controllers, but I'm of the opinion that unless you're pushing high wattages, they're just not worth the effort. It's better IMO to have one small, efficient PWM charge controller per panel.

I use my own as I said. My PWM charge controllers use under 1mA of power from the battery, but will keep the battery fully charged, when sufficient solar energy is available.

If you're serious about living "off grid" for any length of time, you need to minimise energy expenditure, and maximise energy collection and storage.

I've been thinking about replacing the PWM controllers on my dads camper with an MPPT one, on the basis room for solar panels is limited, MPPT will help extract the most out of the available solar estate. It all seems rather complicated

jedi said:

I use one to keep me battery topped up when I don't use the car...Surprisingly does the trick...

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Just a small 5 watt panel will keep a car battery topped up without a problem. I use a 20 Watt panel to do that very thing. I prop the panel on the dash, then run a cable to the battery, with one of my charge controllers in the wire, next to the panel. This keeps the battery at a constant 13.6 Volts, so the car will be ready to start, regardless of how long it's been left unused.

Have you actually worked out the cost?
They do some fantastic coolboxes these days that you can plug into the car while you are driving,(and even the mains in the house prior to going)then when you stop can be run on the small disposal gas canisters. Some even have a small freezer to make ice cubes for your G&T.

We have a very small setup in the stable but it’s only lights.
Fridges are very power hungry when powered by electric.

J

kermit_rr said:

I've been thinking about replacing the PWM controllers on my dads camper with an MPPT one, on the basis room for solar panels is limited, MPPT will help extract the most out of the available solar estate. It all seems rather complicated

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IMO. Unless you've over 200 Watts of panels and over 200Ah of batteries, the gains of the MPPT over an efficient PWM charge controller are so small, it's simply not worth the effort. It's better to use better panels (not flexible), than a more complex MPPT charge controller.

The idea of the MPPT system keeps the panels at their most efficient voltage (normally 17 to 19 Volts), unlike the PWM or more simple switching controller, which pull the panel voltage down to the battery voltage. This in theory allowing the panel to achieve its maximum output power output. However when a panel is pulled down to battery voltage, it outputs slightly more current, offsetting some of the gains of the higher MPPT voltage. Couple this to the larger energy used by the MPPT charge controller while charging and when not charging, any initial charge power gains are simply lost in operational overheads. So for small solar power systems, an efficient PWM charge controller is all that's needed.

marjon said:

They do some fantastic coolboxes these days that you can plug into the car while you are driving,(and even the mains in the house prior to going)then when you stop can be run on the small disposal gas canisters. Some even have a small freezer to make ice cubes for your G&T.

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That's the way I'd go myself, and leave solar power to charge smart devices when away from the mains.

marjon said:

We have a very small setup in the stable but it’s only lights

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The perfect use for small scale solar power.

marjon said:

Fridges are very power hungry when powered by electric

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Indeed they are.

We lived in a mobile home for a couple of years while building our home and for the first year we had no electricity. We ran a caravan type fridge off bottle gas for the whole year. I can't remember how long the bottle lasted but it was probably a month or two. We also ran the cooker and shower off the same bottle.

Hi all
If i use a small panel on the dash to keep my battery topped up will it be ok to plug it into the unswitched 12v socket

@Nodge68 If I was looking for something to run off grid for long periods I would definitely have to factor in no sun days but effectively I'm looking for this to run across weekends so basically a selective 48 hour period. It's not the end of the word if I run out of juice, it just means the lager's going to get warm . However, the point is taken and this is all starting to look like a start up set up that I'm going to need to add to over time.

Cost is important, hence why I was planning in using an existing 240 V fridge (and I already have access to an inverter) but I guess you're right and I really need to start thinking 12 v equipment.

I'm looking at Exide Marine & Leisure for the batteries (about £ 65 each).

Cost wise Solar Panels seem to come in at about 80p to £ 1 per watt so about £ 210 for the panels, £ 130 for the batteries. The PWM controllers are relatively cheap (hence how I got to about £ 350.00) but if I go dual charge I'm probably looking at more like £ 80-£100 for the controller. This is based on flexible panels though (easy to pack in the car) and the suggestion seems to be that they are maybe not the best option.

@marjon Yes, i've looked at several cool box type options ranging from very cheap to very expensive. However, I find the solar route more interesting; cheaper (over time); and of course less damaging to the environment.

@Denboy Nodge can probably advise you better but IMO it will work. However, I think you would be better off with a charge controller in the line as they also give all sorts of protection (under charge, over charge, etc.). You can get a small panel for about £ 25 off Amazon and another £10-£15 for the controller.

Seems I need to do a lot more reading before I plunge into this.

@Nodge68 One other thing...Class A panels or Class B? My understanding is that Class B still work to spec but have visual flaws?

Fritz

Fritz said:

If I was looking for something to run off grid for long periods I would definitely have to factor in no sun days but effectively I'm looking for this to run across weekends so basically a selective 48 hour period. It's not the end of the word if I run out of juice, it just means the lager's going to get warm

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If it's just for the weekend, then a couple of 100Ah deep cycle batteries, supplemented by a couple of 100W 12 volt panels will do the job.

Fritz said:

Cost is important, hence why I was planning in using an existing 240 V fridge (and I already have access to an inverter) but I guess you're right and I really need to start thinking 12 v equipment.

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It's best not to change voltages, as it wastes energy. But you can factor in that the fridge compressor won't run all the time. They cycle on and off, depending on the fridge temperature setting, and how hot the air is around the fridge.

Fritz said:

I'm looking at Exide Marine & Leisure for the batteries (about £ 65 each).

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A decent deep discharge battery can be more expensive initially, but normally has a longer cycle life. If considering On battery technologies, then you'll get 100 to 300 charge / discharge cycles. LifePO4 is the best 12 volt compatible technology, but is considerably more expensive for the initial outlay. However LifePO4 has a huge cycle life, and a virtually flat volts discharge curve, compared to Pb, which doesn't.

Fritz said:

Cost wise Solar Panels seem to come in at about 80p to £ 1 per watt so about £ 210 for the panels, £ 130 for the batteries.

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12 Volt 100 Watt panels can be had for 70 pence per Watt. I've had some good experiences with Hi Tech solar panels, which is what I'm using.

Fritz said:

The PWM controllers are relatively cheap (hence how I got to about £ 350.00) but if I go dual charge I'm probably looking at more like £ 80-£100 for the controller.

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I sell true PWM, 100 Watt solar charge controller kits, starting from £10.

Fritz said:

This is based on flexible panels though (easy to pack in the car) and the suggestion seems to be that they are maybe not the best option

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Avoid flexible panels, as the moment you start flexing them, they begin to break.

A 100 Watt aluminium/glass Hi Tech panel is 1005mm x 668mm x 35mm. This will easily fit across most vehicles, against the back seat. You can even fix a couple of poles to the edges, so it can be propped up and angled towards the sun, and moved round throughout the day for maximum energy collection.