Seeking Solar Panel Advice

[tuko]

This coming summer I'm taking my Series Hybrid on a 7500km trip through northern Scandinavia. I want to have a portable solar panel that I could place on the bonnet or the roof when I'm wild camping or parked up. What I have in my head is something that I can place in the back of the hybrid when we are driving around then plug into the battery connector that I have on the seat box so that it helps with a trickle charge into the battery for starting of course, running the cooler and charging our cell phones/camera. etc.

I'm unsure what size is best and what is involved with equipment required. I've been looking at 50~60 watt panels that I think have solar charge controller in built. Would that be all that a person would need or more?? What are people using here today for their vehicles when camping?

Suggestions/tips are greatly appreciated.

Todd.

[Eightpot]

Depends how much sun there will be, but a 60w panel will go a good way towards topping up a battery, especially as a fridge won't be running its legs off in Scandinavia.

Anything bigger than that gets a bit cumbersome unless it's permanently mounted. You may well get away with 40w, but better to have the extra.

[tuko]

I'll be spending 10~12 days above the artic circle where it will be nearly 24 hours sun. Even further south in Trondheim we had no more that 1½ hours of darkness a few ago. I'm assuming that I will need a solar charge controller, how big should it be, 10A, 20A or higher?

[Guest wunntenn]

I put a 150w slim (3mm thick) solar panel on my 110. I used a 30amp charge controller in case I ever need to upgrade the panel or add more panels. There's a long run of wiring and several connections so I think I have some voltage drop but in bright sun I'm getting a steady 4 amps output - enough to run an Engel fridge (around 2.5amps under start load and a little less than that when cycling) and charge the auxiliary battery, both at the same time.

It's now midwinter and the weak sunlight yesterday was enough to put .6amps into the charging circuit. So well worth having.

The charge controller is a really important thing as it regulates current and the one I got (£50 off ebay) is a Morningstar 30 amp one. Its clever because you wire it to panel, wire it to battery, and connect fridge to it. The controller then handles the charging of the battery and the delivery of fridge current, prioritising the fridge when solar power is available and sufficient, and when it gets dark it 'hands over' current supply to the battery which continues to feed the fridge until the low-voltage cut-off level is reached at which point the controller shuts down supply to the firdge to prevent battery damage and alerts you that its done it.

I thought a cheap and cheerful charge controller would be ok but once I'd read up about how important they are I changed my mind. I was lucky to get the one I did as they are usually almost 4 times that price.

There's some pictures here - half way down the page: http://forums.lr4x4.com/index.php?showtopic=85932&page=9

[Eightpot]

I've been using a £15 charge controller for five years now, it's been spot on. Got another on my 110 in Africa and again it's worked faultlessly.

If I was controlling a panel array on a house I would get something beefier, but for running a small panel & beer cooler for a few hours..

[tuko]

Today I'm going to order a 80 watt solar panel and a 30 Amp controller. This combination should be all that I need to give us the added power that we will need for accessories when we have parked the hybrid for day long hiking trips or wild camping in remote areas.

[Tobias]

Hej, Tuko!

Have a look at the Ctek 250s!

Mppt solar charger and split charge in one unit.

You'd want a separate battery for the fridge so that the starter battery never is Compromised.

Connect starter battery to one post on the ctek. Solar panel to one and aux battery to one. Engine charges borh batteries when running and solar panel takes over when engine stops. It eveb tops the starter battery from the solar.

The ctek is a bit pricey but they are top quality and this unit just solves all the things you want on one box. Fit and forget solution.

Tobias

[Tobias]

And if you haven't already found out, SeaSea in Sweden currently have the best prices for 80w and ctek 250s

[tuko]

Hej Tobias,

Tack!

Didn't think of SeaSea and with them so near in Växjö I'm going to call them tomorrow, they have the 80W panel in stock. Already ordered today a 30 Amp control which will exceed my requirements.

[tuko]

A question for those who know, can the solar panel charge controller be permanent connected in the vehicle? I mean when I'm driving the landy, do I have to disconnect the current from the solar panel so that there is no conflict with the vehicles own electrical system?

Todd.

[qwakers]

as long as the charge controller is wired up right there will be no problem, most have a diode in the curcuit to stop the panel draining the batterys at night, this has the side effect of stopping conflict

[Peaklander]

Just reviving this thread...

I'm starting to look at fitting a solar panel to my vehicle as I have had lots of problems with using a split charge system centred on a Durite voltage sensing relay that doesn't properly charge my aux battery. I think that the weakness in that sort of set-up is that the two batteries, once connected in parallel, do not receive a suitable personalised recharge as they are in different states of discharge. This is especially true of the aux which is fairly deeply cycled once we park-up for a few days. Recovering that to a 100% charge doesn't seem to happen.

Reading about solar controllers and also about the weakness of that charging regime I'm currently using, I have come across this thread and I wonder if anyone else has had experience of the Ctek D250S. It really does look as though it is a good solution. What is attracting me is that it is a charger that handles a DC source from two inputs, namely the vehicle (Starter / Alt) and a connected solar panel. It will provide the controlled charge current for the Aux from whichever of those two inputs is most suitable at the time.

In addition it acts as an MPPT controller for the solar panel and so nothing else is needed there, just a bare panel connected to the unit.

I like that it is intelligent and controls the charge current to the aux battery in the same way that the AC/mains ones do. If I can connect a solar panel to it too with no other wizardry required then I think it's a winner.

The one "drawback" is that it won't charge the vehicle battery. In my case that doesn't seem to be a problem as there's very little drain when standing over four or five days and the alternator seems able to maintain the condition of that battery when we set off again. To provide direct charge of the vehicle battery I'd need to connect the Ctek Smartpass conditioning unit in parallel and this looks to be too much of an overkill in this situation.

I wonder what experiences others have, particularly of the Ctek unit?

 

[Tobias]

I've had the D250s installed since June. A 80w solar panel on the roof rack.

The Defender sits unused for long times (Months) sometimes. I disconnect both batteries with main switches when it sits, but the Ctek is connected to the batteries and the solar panel even when the main switches are switched off.

It works brilliantly!

According to Ctek tech support it pulses a small charge to the starter battery but it doesn't 'charge' it per se, just keeps it from discharging.

It really is just as simple as you think!

[Peaklander]

55 minutes ago, Tobias said:

According to Ctek tech support it pulses a small charge to the starter battery but it doesn't 'charge' it per se, just keeps it from discharging.

That's an interesting additional feature that I haven't noticed.

What sort of loads are you using the second battery for? It's the ability to recharge this battery properly once it has been discharged and the ability of a solar panel to provide the energy to do this that I'm particularly interested in. 

[Tobias]

I have used it for a low-efficiency, high-draw cooler box (peltier type, not compressor) and LED-lighting when camping. This cooler box more or less empties the battery between camping up and leaving the next day. I haven't stayed long enough with enough sun to actually see the solar panel ability to keep up with the cooler box, but it has never been my intention for the solar panel to be able to do that. In time I will invest in a proper compressor fridge and that ts what I hope to be able to keep up with. The engine alternator has seemed to top up the battery fine while driving and the solar panel has topped up and then held the battery in a good enough state to work well, when not using the car. 

[FridgeFreezer]

Those CTEKs are quite spendy aren't they?

On t'ambulance we ended up with a Bosch ~250W panel plus ~30A MPPT eBay chinese controller and totally ignored the design wiring due to the existing (factory) leisure battery setup. Whole thing cost less than a CTEK charger (as far as I could find!).

Worth noting both solar controllers I've opened have been POSITIVE earth which means it's dead easy to wire the thing in in such a way as to be doing absolutely nothing! They also want control of the load (as in, the power from the panel and the battery must pass through them) which in our case wasn't feasible without running yards of heavy wiring all over the place and having to buy a very over-rated solar controller just to handle the full load of the "house" side (ambulance has house lights, fridge, water pump, Eberspacher, stereo, etc. all powered off the 2nd battery).

We wired the panel and battery connections to the controller and called it good. The controller seems happy enough when the split-charge kicks in and manages to keep up with the full use of the camper even in cloudy conditions - our "worst" one was LeMans last year where it rained lots and we were parked under some trees, unable to drive anywhere for ~5 days. Kept the lights on, the beers cold, and the stereo on for the whole time from our old 100Ah battery.

Peltier (or worse, caravan) fridges and coolers are very heavy on electric, you're better off trading up to a more efficient compressor fridge and resulting in a smaller/cheaper solar setup (or not needing one at all). We went from a caravan fridge (almost constant 7A draw on 12v) to a Waeco CRX65 (~0.7A draw average), spendy but oh so nice and it's like a tardis.

[Peaklander]

Hi guys, thanks for the replies, they are really useful and interesting. Yes I too have a Peltier cooler and my, how it draws current. I think it's about 4A although I'm not at home at the moment to check. We have had it for years, it's a Waeco Tropicool and we bought that one as it's very efficient in that it can pull-down the space temperature close to the 20 deg below ambient that I believe is the theoretical maximum. Over the years I've replaced both fans and also worn out both electrical connector plug/sockets.

I do keep gazing at compressor fridge/freezers but SWMBO isn't too keen on the capital outlay. Fridge, I do see that one might well offset some of the costs of the otherwise more expensive supply system of solar panel / controller and battery charger.

Certainly I must do something about the poor charging of the aux battery and I know that it's the cooler that pulls down the battery in the first place. We've had trips over both of the last two early summers where the air max temperature has been 35 deg although the nights have been mainly <20 deg so the cooler gets a rest from high duty cycle operation.

What's attracted me about the Ctek is that it's an MPPT and intelligent charger wrapped up in one package. I recovered the aux battery from repeated deep discharges using a Ctek 5.0 once back home. All I need to do is select a solar panel and decide on the best way to mount it on the roof then plug in through the Ctek and forget (I hope). it is spendy though, as you say.

One point is that this year's early summer trip is a few weeks in Ireland so high ambient temps are not going to be an issue!

[FridgeFreezer]

My mistake, our panel is 100W not 250W, and the fridge is CRX50 not 65. Can't go back & edit the post but hey... worth noting the Waeco/Dometic CRX... models are about 25% more efficient than the older CR... ones.

Rule of thumb is the overall average you get from a solar panel is 1/10th its rating unless you're in the sahara.

It's not just the current draw but the duty cycle of fridges/coolers. Your peltier drawing 4A most of the time adds up to a lot more juice than a compressor one running at maybe 10% or less duty cycle. The CRX50 draws ~4A but averages 1.1A at 25degC ambient and we found it'd be making some progress towards freezing the milk solid on its default setting, we had to turn it down!

Reducing the power use is like lightening race car, it keeps paying back into making other stuff easier. We switched from a caravan fridge (100W load) and replaced the standard fluorescent tubes (~20W each x4) with LED strips (2.8W each). That meant we needed less power, so a 100W solar panel would keep up with things well enough, even if it was cloudy, to give us 5+ days from the single existing 100Ah leisure battery.

We spent maybe £150 on the solar panel + MPPT controller + aluminium to mount it, re-used our existing single 100Ah leisure battery and a little light wiring.

Compared to trying to squeeze in a 3rd battery and/or a much bigger one, and/or try and get 2 or 3 big solar panels onto the roof, plus all the extra wiring and logistics of split-charging it all... spending similar money on a really nice little fridge that's really efficient seemed much easier than buying a stack of solar gear & batteries to haul about.

For your current situation with a less than perfect system you can do a few things to help it out:

Whenever you're driving, run the cooler flat out. Your alternator has capacity to spare, so make use of the electric while it's free and then turn the thing right down when you stop to minimise battery drain. Keep the cooler packed with things - freezer blocks (or cans of beer) hold onto the cold far better than empty space. Make sure the thing has cool air flowing over it, don't let it get buried, don't leave it in direct sunlight (if there is any), etc. etc.

Although it hurt like hell to spend £500 on a tiny fridge we're actually really pleased with it, the layout means it's surprisingly deep so you can fit more things in the 50L Waeco than a 65L+ caravan fridge where you can't lay a bottle front-to-back.

[Peaklander]

Was just re-reading this as I grab a sandwich and your reply popped-up FF.

Yes I know about the duty cycle - in fact it can be very annoying in the middle of the night when it kicks in and out. A constant drone would be better.

I think that £500 is a lot too for a fridge, however had I known just how long we would have eeked-out this cooler then maybe I'd have invested in a chest version of a compressor driven unit.

When travelling, as we have a 110 CSW we keep our bubble wrap privacy screens in the quarter lights and rear side windows - just leaving the rear door window 'open'. The screen for that is always laid over the top of the cooler and if we park, even for just a few hours, we put up the rest of them - it's amazing how much radiation they reflect.

A little more "on topic", I think that I will try a solar panel; I don't have a lot of time to surf the shops right now but I had thought that panels cost more than you say. I might well go for this Ctek dual unit as I know that my split charge and 65A alternator will not fully charge the aux battery. I've checked everything including having the alternator checked out and short of buying a clamp meter to prove what the charging current into the battery really is, there's not much more I can do. I think it's a lot to expect for an alternator regulator to be able to supply differing charge currents to two batteries of completely differing states, connected in parallel. They really do need some intelligent control.

 

 

[FridgeFreezer]

How can your split charge not charge your battery? I don't follow? surely a basic split-charge is a relay that just ties two batteries together, at which point they both get dragged up together by the alternator. The alt doesn't know any different if it's one battery, two tied together, or whatever... it's just a load. Shouldn't require any great intelligence to make it work properly.

Sounds like your system has issues, I'd try and sort those before adding more things.

[Peaklander]

That's just it, it doesn't fully charge. I have checked things out as I said. I have a good working alternator (took it to be tested at a known auto electrical repair place that's been there since year dot). The relay is a Durite voltage sense and of course it just clicks in. All the cabling was new two years ago with proper crimps or soldered lugs. Oh and both batteries are those stupidly expensive Odyssey ones and they were new too.

I noticed that the aux battery wasn't holding charge  during our first long trip away. To say I was dis-chuffed was an understatement. When we got back I returned it to the supplier and they sent to to Enersys. They recovered its condition through a process of charge / discharge (I have the exact details somewhere) and then I had a conversation with their Engineer. His advice was that it was almost certainly not getting a proper re-charge when on the vehicle.

The explanation for this seems to be that the alternator regulator can't correctly handle two batteries, in parallel, when they are at differing state of charge and it will be reducing output to something lower than the aux requires due to the effect of the well charged starter battery that also in circuit. I have some researched details of this somewhere too.

I think that my high drain peltier cooler is just making things worse because it wipes out the aux battery very quickly in seriously hot weather - as we've already noted above.

This led me to think that I need something to properly split the output at the same time a solar panel would make sense. To find a MPPT controller and the charger in one unit, as per Tobias' and others comments, seems to be a solution. I do share your scepticism though and maybe I can only prove it to myself by measuring the current into the two batteries during mismatched charge states and with the alternator running.

[Bowie69]

Voltage sense relays can exhibit  a 0.7v drop, which would stop it charging fully.

I don't know if that includes the future.

It could also be too thin cabling, or poor connection causing voltage drop. 

Personally a normal relay linked to either oil pressure switch or alternator charge lamp is my preferred choice...

[FridgeFreezer]

When your relay joins the two batteries they will try and equalise, if one is very flat the other will try and pour current into it. The two joined together will look like one bigger battery to the alternator, which is a dumb device that basically just aims for ~13.8v. It's possible that the starter battery drags the voltage of the 2nd battery up a fair bit but it's not actually able to effectively recharge it, and the higher voltage means less current gets poured in from the alternator.

What rating is your split charge? Durite make many relays, some are 20A some are 200A... there doesn't need to be much voltage dropped across the link to cause a fair hit to the charging rate if the battery is proper flat, and again the voltage drop from one side looks like an artificially high voltage on the "good" side.

If you've flattened your 2nd battery below ~60-80% capacity it may well be damaged (backup batteries get scrapped if they undergo a heavy discharge) although the "stupidly expensive" Odyssey ones should be pretty tolerant of this.

Does your cooler have a low-voltage shutoff? If it doesn't, you need to sort something out before it kills a stupidly expensive battery!

[Peaklander]

Ha yes the last sentence made me chuckle FF. In fact I'd said to my better half at the weekend that I need to construct a little black box to shut off the supply at < x volts.

Luckily the Odyssey is tolerant and I totally trust the diagnosis of Enersys and the fact that it was recovered. Now I use a Ctek 5.0 and take it away with us so when there's a mains point available, I can give it a controlled recharge.

Bowie thanks for the advice ref connections. I did work through them all with my Fluke and all the cables are sized correctly. A clamp ammeter would be useful for other stuff and I might use one to get to the bottom of what is an infuriating problem which I have parked twice now during the off season.

 

[Mo Murphy]

You can or used to be able to at least, get a voltage cut off 12v socket. It's a bit like a short 12v extension with a switch on the socket to select at which voltage to cut off. An Ebay search should prove fruitful.

HTH

Mo