Basic solar panel

[Irmscher2007]

Hello. New member, what a great forum

I'm after some advice and pointers if anyone can chip in.

The van was converted about 8 years ago.

It has an electric hookup up, PMS3, leisure battery (nothing fancy)

It runs a domestic chest fridge, LED spots, a few plugs and has the 12v cigarette charger type connector in the middle of the plugs.

Most of the time we are on hookup so can use all the electrics.

I am doing the annual trip to Le Man's 24 hours motor race in June. Usually we have a hookup as we get there early and can power all the van, and external fridge in the van, a Vango cook grill etc using a splitter.

Unfortunately the site we are on this year has no electric so will have to run off the leisure battery. I cannot see the battery being able to run for 6 nights powering the fridge, charging phones and speakers.

Solar wise, to keep the leisure battery topped up I was looking into purchasing a portable foldout Renology solar kit.

I have spotted the one below on eBay for £80.

Would this do the job to keep the battery topped up? It has a controller built in on the back of the panel so is it as simple as connecting the wiring to battery terminals?

Which blue tooth device would be good to monitor the solar power being produced? Thanks

 

[Lumbo2]

You're right that you will not get 6 days out of the battery with the fridge running. I can't see the wattage of that panel you show in the picture. I have a 100w renogy folding panel like that that is ok for keeping the leisure battery topped up but really needs a good sunny day to do so well.

 

[roadtripper]

Renogy is a well regarded brand around these parts but not sure that size will be enough.

A compressor fridge will draw something like 5 amps when running (you can check your manual for specific details) and it's probably reasonable to estimate that it will run about 1/4 the time.

That means your fridge will consume ( 5 x 24 ) / 4 = 30aH a day. Given that a lead acid battery (FLA or AGM) which I assume you have shouldn't be discharged under around 50% to prevent damage if you have the regular 100aH capacity that gives you about 2 days run time.

For a solar panel to keep up with that you need it to replace 30aH during daylight hours. No panel achieves it's ideal condition rating so probably work on getting out an average of 2/3 it's rating. So assuming a summer's day and 12 hours of useful sunshine 30aH / 2 = 15 amps charge current. 15 amps * 12 volts = 180 watts

Very rough estimates in terms of numbers but that suggests at least looking at 200w panels. To get the most out of them don't use the simple PWM controllers they come with get something like the Victron MPPT ones as they are better at running the panels at the maximum power point.

See correction below as I dropped a 1 in this calculation, thanks for spotting @EAN

Basic solar panel

Hello. New member, what a great forum I'm after some advice and pointers if anyone can chip in. The van was converted about 8 years ago. It has an electric hookup up, PMS3, leisure battery (nothing fancy) It runs a domestic chest fridge, LED spots, a few plugs and has the 12v cigarette...

www.t6forum.com

Also there are some tips I put on this thread for ways to get the most out of your fridge in other ways than just bigger batteries:

Camping Ideas and Tips

NEWS FLASH…… If you’ve not got the must have of the season….. Tesco’s Have It …. Only £68……. just love big fat wheels :rofl:

www.t6forum.com

 

[EAN]

@roadtripper Something doesn’t look right with your sums to me.
If you assume you have a 100W panel operating at 100% efficiency, that’s 8.3A being generated per daylight / sun hr.
Operating at 2/3rds efficiency that’s 5.5A being generated per daylight / sun hr.
Using your figures: in the 12hrs of sun period, the battery would get 66Ah of solar charge, but would discharge 15Ah running the fridge at an average of 1.25A/h (25% duty cycle 5A); giving a surplus of 51Ah. During the following 12hrs of no solar charge the battery would discharge another 15Ah.
Assuming a fully charged battery from the start, it would stay fully charged during sunlight hrs, lose 15Ah overnight, then recharge fully during the day and run the fridge: So self sustaining ignoring any other loads.

I found a formula online somewhere that I tend to use for my calculations and that is based upon solar generating a max 0.7Ah/W/day in summer decreasing to a low of 0.05Ah/W/day in winter.

I really hope I’m not wrong in my understanding, otherwise the 200W solar panel that I recently purchased isn’t going to do anything in replacing the loads I intend to draw. Have yet to start experimenting with it.

 

[Sackmycook]

On my old van, I had a Vevor compressor fridge and leisure battery. I could run the fridge in hot French summer temps for about 1.5 days before it threw a low voltage error. I had a Jackery 500 solar set up, so could plug the solar panel during daytime to give the leisure battery a helping hand and at night, plug the Jackery unit into the fridge to run it. Worked fine

 

[Irmscher2007]

Thanks for you input.

That 100w solar panel has now sold on eBay so looking at others on the Renogy eBay site as they don't seem to do the portable ones on their main site, along with a separate charge controller rather than inbuilt, so I'll look into the MPPT ones.

I was thinking I could attach some quick connects to the leads going to battery as it's under the rear bench so hard to get to, and attach the charge controlled to the under there aswell.

 

[jimc91]

Thanks for you input.

That 100w solar panel has now sold on eBay so looking at others on the Renogy eBay site as they don't seem to do the portable ones on their main site, along with a separate charge controller rather than inbuilt, so I'll look into the MPPT ones.

I was thinking I could attach some quick connects to the leads going to battery as it's under the rear bench so hard to get to, and attach the charge controlled to the under there aswell.

have a look at Lensun Solar,

 

[Howzat]

Thanks for you input.

That 100w solar panel has now sold on eBay so looking at others on the Renogy eBay site as they don't seem to do the portable ones on their main site, along with a separate charge controller rather than inbuilt, so I'll look into the MPPT ones.

I was thinking I could attach some quick connects to the leads going to battery as it's under the rear bench so hard to get to, and attach the charge controlled to the under there aswell.

That suitcase controller is fine. Uses pulse technology same as modern chargers. I've got one and it can easily add 5amp per hour on a sunny day, so say 5 hours per day = at least 25 amp back into your battery. It might not fully top up the battery each time depending on your usage but it should be enough to stop the battery running down to empty over the 6 days but that depends on your battery type and size which you don't state.

And they have the suitcase on their site?
Some users here also offer a 6% discount on the web price, like @Dellmassive. Look for one of his posts and you'll find the link in the signature.

100 Watt 12 Volt Foldable Portable Solar Suitcase Monocrystalline with Waterproof Charge Controller (G2 Version)

Renogy 12V 100W Portable Solar Panel is an entire solar power system incorporated into a single, compact package with a waterproof charge controller.

uk.renogy.com

 

[PaulR83]

Can you just wire a mppt to a 12v cigarette lead and into one of those if it's connected to the LB?
Thinking of doing that if I don't want it in all the time and fully integrated?

 

[Howzat]

You can, but anderson connectors are much better as there's less chance of a short.

 

[PaulR83]

You can, but anderson connectors are much better as there's less chance of a short.

Thanks, guess can wire one onto the battery then tuck it away when not in use.

 

[Howzat]

Yeah, or go full posh and flush mount it on the seat base.

 

[roadtripper]

@roadtripper Something doesn’t look right with your sums to me.

Yep, good catch, never do sums while stuck in a work conference call.

I accidentally dropped a 1 when dividing the charge capacity to replace so 30aH / 2 when it should have been 30aH / 12 to get the average charge current per hour.

That leads to average charge of 2.5 amps or 30watts.

Apply the 2/3 factor (which I didn't in the original example) gives 45watts of panel.

This is why I always show my working, it helps explain but also means others can spot howlers!

I'll see if I can edit the original to save future readers confusion.

Given that lower number I'd also agree with @Howzat that going MPPT Vs PWM is less important, just make sure it's a decent quality controller and I'd definitely second using Andersons for anything beyond a quick trial. It's probably a good idea to size and fuse the one connected to the battery for heavier loads (maybe 30amp) as once you have a general purpose power connector you may find other uses for it.

 

[Irmscher2007]

Yep, good catch, never do sums while stuck in a work conference call.

I accidentally dropped a 1 when dividing the charge capacity to replace so 30aH / 2 when it should have been 30aH / 12 to get the average charge current per hour.

That leads to average charge of 2.5 amps or 30watts.

Apply the 2/3 factor (which I didn't in the original example) gives 45watts of panel.

This is why I always show my working, it helps explain but also means others can spot howlers!

I'll see if I can edit the original to save future readers confusion.

Given that lower number I'd also agree with @Howzat that going MPPT Vs PWM is less important, just make sure it's a decent quality controller and I'd definitely second using Andersons for anything beyond a quick trial. It's probably a good idea to size and fuse the one connected to the battery for heavier loads (maybe 30amp) as once you have a general purpose power connector you may find other uses for it.

So would these new workings out suggest 100w should be ok to keep the battery topped up for 6 nights without EHU, but ideally 200w if possible

 

[EAN]

So would these new workings out suggest 100w should be ok to keep the battery topped up for 6 nights without EHU, but ideally 200w if possible

100W in Summer is fine provided the sun comes out. Of course a bigger panel gives you more margin but there’s always a trade off on size, weight etc.. etc… especially with portable panels. I’ve just purchased one of the following to play with, but haven’t managed to even get it out yet with the weather being so crap: And it needs an external controller.

Renogy 200W Portable Solar Panel

Trust Renogy for all your off-grid solar panel system needs. Simply add the Rigid Solar Panels, Foldable Solar Suitcases, curated Solar Kits, Charge Controllers and the Mounts to cart to save!

uk.renogy.com

 

[roadtripper]

It's hard to give you a direct answer as you've not really provided any details as to your current battery and which fridge you have, but hopefully the corrected figures will let you run your own numbers.

What may matter more than absolute panel size is how are you going to use them. A 100w with 12 hours of good sunshine is likely to work but if you are at LeMans if you have a portable panel is someone going to stay with the van for 12 hours to keep moving the panel around to face the sun and stop it getting nicked?

If you are only going to deploy the panels when you are at your van, and you're only going to be there half the day then maybe a larger panel might be needed.

The folks around here who mostly run off solar tend to have at least 100w permanent mounted on the roof so it's always available, even if not well aligned to the sun, and then top up with portable panels when at/near the van.

 

[Irmscher2007]

The fridge is a Dometic top loading compressor fridge,Rated input power (DC) 45 W

The battery is bog standard a 110ah Numax lead acid.

it does worry me that someone could pinch the panel if we were away from the van which we would be for most of the day whilst its out in the sun.

The Renogy suitcase has a small handle which looks like it could take a bike cable through it and the legs which could be attached to an allow wheel.

Not perfect but a deterrent.

I really don't want to be drilling holes into the pop top roof for a week or so of solar usage a year as we have EHU for pretty much every trip.

I'm just wondering if the flexible panels could be attached to the roof on arrival and they could be moved to windscreen once the sun moves around.

 

[Irmscher2007]

100W in Summer is fine provided the sun comes out. Of course a bigger panel gives you more margin but there’s always a trade off on size, weight etc.. etc… especially with portable panels. I’ve just purchased one of the following to play with, but haven’t managed to even get it out yet with the weather being so crap: And it needs an external controller.

Renogy 200W Portable Solar Panel

Trust Renogy for all your off-grid solar panel system needs. Simply add the Rigid Solar Panels, Foldable Solar Suitcases, curated Solar Kits, Charge Controllers and the Mounts to cart to save!

uk.renogy.com

I did see those ones aswell but the description seemed to suggest they are for charging power stations. Does it have all the same connections as the other panels so it can charge a leisure battery?

 

[AdL]

I have a 200W cheapo panel from Ebay - https://www.ebay.co.uk/itm/334791196734 Then put an XT60 connected through the 240V socket flap to the solar and straight to the leisure battery charger terminal (effectively to the battery terminals direct). Works a treat! Never run out of juice on a camping trip yet. Longish cable on the solar panel so it can be positioned away from the van if that is better solar.

BTW - yes I know the screws a rusty - on my list to replace with stainless this summer.

 

[EAN]

I did see those ones aswell but the description seemed to suggest they are for charging power stations. Does it have all the same connections as the other panels so it can charge a leisure battery?

It’s just a panel with MC4 connectors, so requires an additional controller between it and the battery.