Author Topic: Solar Chargers  (Read 702 times)


  • Guest
Solar Chargers
« on: November 26, 2018, 04:15:45 PM »
I have been reading a lot about solar panels and chargers (thanks Glort) so I thought I would look on  a well known auction site for a brand name charger. Sealey is quite a big name in tools in Ireland UK


Note that this isn't waterproof!


  • Hero Member
  • *****
  • Posts: 2783
    • View Profile
Re: Solar Chargers
« Reply #1 on: November 26, 2018, 04:33:48 PM »
Sealy no doubt is just labeling products from China.  I would not be afraid of the simple, inexpensive on/off type charge regulators from China.  Basic designs, and totally adequate for the job.  I still use one for my engine shed 12V system, in service for 10 years, still going despite a lightning strike which fried some other electronics.


  • Guest
Re: Solar Chargers
« Reply #2 on: November 26, 2018, 04:41:21 PM »
I would have thought that being able to be outside in all weathers was a prerequisite for a solar panel  :-\


  • Mendocino Metro
  • Hero Member
  • *****
  • Posts: 1467
  • Mmmm BBQ
    • View Profile
    • Mikes Solar PV page
Re: Solar Chargers
« Reply #3 on: November 26, 2018, 07:01:22 PM »
In America, there's an ongoing market for dashboard panels used to keep car batteries charged while being shipped overseas for delivery to dealers.  VW uses many of them.   Since they sit inside the car on the dashboard, they are not waterproof


  • Hero Member
  • *****
  • Posts: 3354
    • View Profile
Re: Solar Chargers
« Reply #4 on: November 26, 2018, 11:36:05 PM »

What do you actualy want to do with this Paul?

I have seen these things before and wondered about them... as in wondered if they can actually work at all?

If you look at the specs, they are nominal at 1.5W. I reckon that would be best case scenario but taking it at face value, I't think that is going to probably be struggling against the internal resistance and self Discharge of a car size lead acid battery. It may be able to possibly maintain the battery ( with NO loads) but it sure as heck isn't going to charge anything.

I have also wondered about these as a battery maintainer in a vehicle. A lot of them you plug into the cigarette lighter. Unless the ignition is on which would most likley cause more drain on the battery even if everything was off, the power can't go back tot he battery. far as I can see all that could possibly happen is the thing may offset the parasitic loads like the clock and the computer backup.  A car ( least anything in the last 20 years) is never completely off, there will always be some draw like from the stereo memory, computer and other things and the combined Ma they pull would be a LOT more than these things put out.  Far as I can see they would at best slow the battery drain but would not maintain the charge indefinitely.

Add to the low output and the time they wont charge at night.... Definately a devise to slow discharge rather than prevent it in my book. If you put one on a modern car, the parasitic loads they pull is quite high, I was reading about 100Ma on a benz a while back. No way in hell it will stop one of those going flat or extend the time it does very much.

I have a few different solar controllers for hooking up to panels. Mainly cheapies but when I was playing with a battery/ inverter setup and running a fridge and kettle off it a couple of years ago as my first solar learning, they worked very well.  Some better than others with the features but in a pinch, all quite OK.
To me, one would be far better off buying one of those, even the $10 ones and a 20W solar panel.  That would certainly have the grunt to maintain a car battery and overcome any loads the vehicle was drawing.

With the better cheap chargers, you can set all the parameters on the things like the float voltage of the battery which is important. I found the real cheap controllers with no settings tended to be a bit everywhere with the float outputs. Obviously factory set and subject to manufacturing tolerances. Some have a trimpot you can adjust if you pull the things apart, some don't.

The 30A controller I had that had all the settable functions was a ripper and worked well for about 9 months I was using it.  I pretty much hammered that thing too. I had a heap of panels on it capeable of well over 30A and when I boiled the kettle the inverter was pulling over 200A so the little controller was maxxed out but it took it... many times a day.

There are a STACK of solar controllers on fleabay and elsewhere labeled MPPT ( Max power point Tracking) which is the ideal / best architecture for a controller.  What this means is if you are only getting say 8V@ 2A, the controller will ramp the voltage up to the level required by the battery but at lower amps so it is still charging. If the voltage is below the battery level, you could have 10V@1000A and your battery would still be flat.

The cheaper chargers are not so flexible and basicaly chop the excess power and if the voltage is low, then tough, it does not charge.  They still work real well, just not as efficent.
Because MPPT is the desired type ( and also a lot more expensive to make) a lot of PWM controllers are labeled MPPT as per normal Chinese BS marketing with everything.

The cheapest Proper MPPT when I last looked was about $60. They may have come down a bit but you can be guaranteed no $10-40 controller will be MPPT no matter what the writing/ description says. I only have the PWM types and they are more than adequate if you have a decent input like the Domestic 200W / 30V panels I was driving mine with.

The only issue I had with the cheaper PWM's ( and I don't know if the MPPT's are the same)  is that you can't connect a 30V domestic panel to a controller driving a 12V battery.  They work in ranges so you  would have to have a 14-18V input for a 12V battery but a 30V input ( to 40V I think) on a 24V setup is fine which was what I had being my 2Kw inverter was 24 not 12V.
There are ways around that. I got a voltage converter that did 150W and could put that between the panel and the controller so the input was lower and I could run a 12V battery and the other thing I did was  get into the diodes on the back of the solar Panel and bridge off 2 of the 2 Diodes to get a lower voltage that way. Depending on the  panel Voltage, you might be able to jump off each pair giving a lower voltage but a x3 the amps.  Not a lot of panels I have come across go above 48V but some older ones do 60 and some of the real early types did 90 which even divided by 30 would be too high again. Hard to find those ancient ones now though

Even a small domestic Panel of 175W would give you infinitely more power than one of these car chargers thats for sure and even with the additional cost of the controller, would still be way ahead on cost per watt  produced.  If you actually wanted to power something, even the smallest ligh bulb, unless it was LED you couldn't have a chance with these dashboard things.

I did a couple of " maintainers" for my Father.  One is a solar that does the mower shed. It's a panel into a 200W I think it is reducer that I have set to  15.5V or so.  It has 4 take offs so can do the mowers, chipper and something else I now forget all at once. So they aren't all connected, I have a couple of Diodes in each output which drops the 15.5v back to a more correct float voltage of around 14.8 and isolated each piece of equipment so they aren't all acting like one big battery. 
This thing has the capacity to charge not just float and so far has worked perfectly.

The other one I did was for the tractor and is a rectified halogen light transformer. I think that is around 4A output at 16V and is on a buck and boost controller set to 14.5V or so. Dad was paying about $80 for these " Battery Fighter" Maintainers and they only lasted a couple of years.  I think I screwed this one together for under $10 and it's been going about 3 years so far with no probs. Actually had a dead alternator on the tractor for many months and didn't know. Saw the light, thing was working fine and kept forgetting to investigate. Obviously the tractor pulls little current other than starting and the charger was keeping the thing topped  up so no problem. Wasn't till I pointed it out  he discovered the problem.  New Iseki 35A alt, over $400.  Used Subaru 80 A alt lying round in a big pile, 5 min to change the pulley which was incredibly the same size shaft and bolted right up with just some packing washers for precise belt alignment. 

If you are looking at one of these "Trickle" ( more like a very slow drip) chargers for battery maintence, I'd say they may be OK for a Mower battery or a motorbike but to really keep a car battery charged, I think they would be really questionable and something with at least an amp output would be a lot more in the ballpark especially knowing the difference between the rating of solar panels and the typical real world outputs.


  • Guest
Re: Solar Chargers
« Reply #5 on: November 27, 2018, 09:41:02 AM »
Hi Glort  thanks for the info! I have what used to be a coal shed it's not wired for power. We keep logs and stuff in it and it's damp so I don't want to put 230v into it. I thought a car battery and a 12v PIR light would be the easiest way to light it. Obviously the charger I linked to would be useless I really didn't think it would do I was just wondering why Sealey would even add their name to what is basically a toy solar panel. I know you can get a solar shed light that comes with a little panel you mount outside but I imagine its pretty pathetic in terms of the light it produces but of course  I could be wrong. I have a little cree torch which seems to be left lens down and in the on position whenever anyone uses it, Grrrr. There is a small hand squeezed dynamo torch in the shed it seems to be too much trouble for modern people to use all that squeezing really takes it out of you apparently!
So in order to maintain and maybe top up a battery what size charger would I need? Would it require a charge controller. The battery I have is 36 amp small car battery


  • Hero Member
  • *****
  • Posts: 3354
    • View Profile
Re: Solar Chargers
« Reply #6 on: November 27, 2018, 11:58:03 AM »

There are a variety of controllers you could use Paul that would all do the job.  Your requirements are very basic but like me I think you will get interested with this and want to play around and do more with it once you have the capability.

A basic controller would be like this:


I bought a few of them and they work well. I used one for a battery maintainer and was going to use the others on Dads setup but then thought they were overkill.

The one I really like that can be programmed is this one:

I have it in the 30 A version and found the thing to be really good.  Like a lot of electronic things that measure voltage, I found the display was out a volt odd on my multimeter so I wrote the correction factor on the front to remind myself and off set it accordingly. Once you have them set to where you want you don't have to change again anyway. I'ts always good to check these things with a multi because I have found they are out more times than not and 1.2V on battery floating DOES make a difference.

I see you can get them in 10A as well which would suit your current purpose but if you ever want to expand to a bigger panel and input.... the 30A would be handy.

For a panel, As I suggested, 20W would be adequate unless you are going to run a stack of lights for hours.  You could also go to a used House type panel but I don't know the availability of them where you are. Here you could pick up used 195W panels for $30 all day long.

Something like this would fill your stated requirement:

You wire the panel to the input on the controller. There is a connection that goes to the battery and there is another that goes to your light. the controller can turn the light on at certain times, at certain inervals or you can turn it on manually. Or you can just wire the light through a switch from the battery.

As for lights, stack of LED type you can get now from Indoor 12V versions to car lightbars to floods, You name it.

One thing Immediately comes to mind with this from what you said. You keep logs in the shed and it's damp. Not what you want.
I have a couple of broken panels on my shed roof and they are wired to a set of car radiator fans. They sit in the window and blow in a good gale to keep the shed surprisingly cool in summer and in winter  drive an LED light bar for my seed germination in an old fridge.

If you got hold of an old house solar panel, you could get a car or cheap marine Bilge blower fan and duct that into your woodshed.  This would circulate the air, drive off the moisture and make your wood burn MUCH better.  Just having a positive air change would dry the shed out well and with a home solar panel, You would have plenty of power left over for battery charging. I'd be stacking the shed full  for summer and with split  stacked wood and the fan, it would dry out and be ready for the next winter easily.  Forced air dries timber exponentially faster than still air.

 One of the features of the controller I was talking about is it will also switch loads at a pre set Voltage.  In other words, you set the fan to run 0.5 of a volt above your  batterys float level where it is fully charged.  The battery will get priority and then the fan will kick in using the excess power that would otherwise go no where once the battery is up to and kept to float level. 

This is the kind of expansion you can do with these setups.
As you will have a battery in there, you can also get a small 240V inverter and have power to run some tools or a TV, radio etc so you can transform the shed into a comfortable man cave! :0)

You can see the early version of my solar stuffing around on this vid.


Wow, 2 years ago I did that.  I added to that a WHOLE lot. In the end that panel I made up was covered with breakers, meters, other controllers and suffed full of wiring. I was running a 2Kw inverter and that UPS.  Added a kettle I had on a PWM controller so it kept the water just off the boil and when I wanted a cuppa, I turned it on full and in 15 Sec the water was on a rolling boil.  Even the mrs liked that.

Now I have almost 20Kw of panels, 4 inverters running atm and make more power than I need for the entire house.
Careful you don't get carried away like I did!  I'll say this though, it's an interest that has more than paid for itself. The mrs doesn't bat an eye with me buying solar stuff now because she knows how far in front we are with it.