Solar power charging problem.

Discussion in 'General Science & Technology' started by Blindman, Jul 1, 2010.

Thread Status:
Not open for further replies.
  1. Blindman Valued Senior Member

    Messages:
    1,425
    I have a 12V 80Watt solar panel to charge a 12V lead acid battery. But with trial i have found that I dont get the amp hours I need from the battery. As I understand it when the battery charges the controller slows the power into the battery so that around midday the most of the power from the solar panel is waisted.

    I want to know if I hook up a second battery in parallel will this soak up more power from the solar panel?

    Any in the know please let me know as I am heading of in 18hours and will only have intermittent net access via my mobile.
     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. greenfroguser5 Registered Member

    Messages:
    5
    yes if you put another battery in parallel it will generate more power. but will it be cost effective? plz think before doing. and also contact any mechanic before doing this.
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. hypewaders Save Changes Registered Senior Member

    Messages:
    12,061
    I would check out the battery, and make sure your charge controller is the right fit for the job (it sounds like you may already know where your trouble is). Consider eliminating the charge controller, at least for troubleshooting, and depending on what you're doing with the setup. It could be that you have a decent CC but are simply taking more out of the system than you're actually getting in- that you are depleting your battery by using more power than the panel can keep up with over time. There are some variables in installation and wiring that sometimes yield less power than expected.

    A quick test of your panel is in order, by disconnecting its leads and putting a volt meter on them. It should put out something like 16v (it should say on the data label what the nominal unloaded voltage should be).

    If there is any doubt about the battery (if it is not new or has seen neglect or abuse) then I would start there: If it isn't a sealed battery, make sure the water levels are OK and that the plates don't look warped or salted up (forgive me if you already know/have done this). To actually test the battery you will need to give it a full charge somehow. If you have a separate automotive-style utility-grid powered "peak" charger (a charger that drops to "float" amperage when battery resistance rises) handy, then give it a full charge. To see how much capacity the battery now has, you will need to apply a fixed load and time it, or at least make a reasonable estimate of the amp-hours you're getting out of it with your 12v devices by their ratings.

    The more computerized battery chargers found in many commercial automotive garages automate charging, and I think it's worthwhile to give that battery one good sure charging to see if it's OK. If you don't have much gadgetry at hand, the best way to check out your battery may be just to call a friendly auto shop and ask if they'll check it out and charge it up for you.

    I would make sure that your charge controller is suited and set up for your array and battery. It should be rated for about 1/10 of the battery's amp-hours. It should be of a design that will always hold "float" voltage, and not be of the kind that waits until battery voltage drops below some threshold to allow charging (some solar chargers are still like this, and these will sit there NOT not topping off your battery whenever the sun shines, if you haven't drained them down enough.

    If you post make/model of the controller and your panel, I'll look them up and make sure it's suitable, and see if there is any special setup required for that controller.

    Sometimes it is not harmful to just eliminate the charge controller. If I were in a remote situation without access to other parts, I would make a direct shunt around the controller and put a switch on it (or just grab jumper cables from the car) to try it out. You do have to be a little careful here, because you could possibly damage diodes in the solar panel if you do a lot of arcing and sparking. I don't mean to insult you with real basic common sense, but also- Don't zap yourself working on your panel in the sunlight: It's much more dangerous with arrays than a single panel, but it's a good time to learn good habits here at the dawn of the PV age.

    The voltage from one panel that size can't possibly hurt a sizeable (30Ah or more) lead-acid battery needing charge. Well, at least not right away. Your battery will have no problem taking some charge from that panel for a while without any controller, although I wouldn't necessarily advise fully charging it unsupervised, or just leaving it hooked up all the time. There are applications where things go fine without a charge controller, but because decent CCs have gotten more affordable there's not much justification for that.

    If you go direct as part of your troubleshooting, and if you have a long sunny day, at some point your battery will start to boil: The slow production of hydrogen and oxygen will start to accelerate, and battery temperature will rise. The best small DC charge controllers ramp up the charging of lead-acid batteries to all they or the array can handle, and then drop down to float charge as the batteries start to change resistance and/or heat up at full charge. There are other specs and sales pitches about peaks and cycles, tracking, sulfation, etc. in more expensive controllers but I don't go for all that (especially not in a simple system like yours). The worst charge controllers may out of sync with their owners and the sun, and don't do their job so well. If that's what you have, you can either supplement your charging methods to fully top your battery now and then, or get another controller.

    Summarizing the first steps (assuming you have a meter) check your panel output, check your charger output, and inspect and charge the battery. Post some specifics on the panel and the charger, and I'll let you know if I think any changes are in order (I'm a solar installer BTW).
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. Blindman Valued Senior Member

    Messages:
    1,425
    Thanks Hypewaders.

    I have just returned from a month up north (Western Australia). I have been working from a single 80W panel and two 35Ah batteries. It worked just fine. The charge controller would switch to float charge and then I would switch batteries. I got all the lighting I needed and could use my computer most of the night. I could also get some day time usage from the panel when the batteries where charged.

    I also had a 800W generator but only needed to use it twice. Once when there was no sunlight and a second time when I drained my batteries when I fell asleep with everything on and a overcast day the next day.

    I did have to keep an eye on the panel and move it every few hours to get the max power. Facing the sun I could get a max of 4.8amps at around 13-14V most of the day but if I neglected it after few hours it would drop to about 2amps.

    Next time I go north ill leave the generator at home.

    I did find that I should keep my laptop batteries charged as charging and using the laptop would drain my 12volts batteries very quickly.
     
  8. phlogistician Banned Banned

    Messages:
    10,342
    Are you running the 12v batteries into an inverter, and then plugging the laptop Power supply into that, or using a 12v adapter for your laptop? I'd suggest the latter for increased efficiency.

    I trickle charge our 85Ah caravan battery with a 2w/13.8v panel. Have considered getting bigger panels now we have a camper too. Looking at a single 25Ah battery and 13W solar panel as space is an issue, just for lighting.
     
  9. hypewaders Save Changes Registered Senior Member

    Messages:
    12,061
    Glad to hear it's working out for you, Blindman. How do you like living off-grid?
     
  10. Blindman Valued Senior Member

    Messages:
    1,425
    It was an interesting experiment. I did become very energy conscious. I did not have the power to run the fridge and had to rely on gas for that. I am thinking of getting a second panel and a large 80Ah battery to run the fridge. This would make me totally off-grid (LPG I still consider as being on the grid)

    The computer power log showed that I used approx 2kWh of energy over the 4 weeks for the laptop.

    It would also be nice to have an electric car. Have 4 panels to charge the car for a few days and then get around 100-200km from a charge. With a backup generator for emergency power I could travel around Australia with minimal energy cost. But I dont know that much about electric cars and performance especially if towing a caravan.
    Im using an inverter. I have a app on the laptop that monitors the energy usage. In low power "Green" mode it will average about 40W, in normal mode 60-70W. But when charging the laptop battery at the same time as using the laptop my 150W inverter would cut of. I got the next step up, a 300W inverter to run the laptop.

    I will look into a 12V power supply, but the laptop input power is 19V DC, so I dont know if they supply a 12V adapter. Its a Toshiba Satellite Notebook.

    As for lighting I went totally LED with all the lights on im only using just over 5W and minimum reading or cooking light is less then a 1W.
     
  11. phlogistician Banned Banned

    Messages:
    10,342
    OK, well, something like this;

    http://www.maplin.co.uk/module.aspx?TabID=1&criteria=usb&ModuleNo=223912&C=SO&U=Strat15

    is rated at 100w max, and should run and charge your laptop. I'll pick one up for our camper, and let you know how it goes. Hopefully, it'll be more efficient that converting DC to AC and stepping it down again.
     
  12. Blindman Valued Senior Member

    Messages:
    1,425
    Thanks. The 100W version does not have the power for my laptop. I need 19V and 6.32amps max. They have a 150W version so ill buy one of them. Nice and cheap to.. Thanks Phlogistician. Im heading south for a while and anticipate very little sunshine. Im going to get a second panel. As I understand it that should be wired in parallel with the first to the charge controller.

    Im also thinking of wiring up a LED 12V lighting system for the house. No point having the solar panels sitting in the shed when at home. But this brings in the problem of loss of power when transmitting 12V over distance because of resistance. Would anyone know of low resistance wiring or other solutions.
     
  13. Spud Emperor solanaceous common tater Registered Senior Member

    Messages:
    3,899
    Blindman,
    to derail the thread momentarily, where abouts in the West were/are you?

    Towing a caravan with an electric car, sounds like a tall order buuuut...it leads me to an idea. Cover the whole bloody caravan with solar panels, you'd go a thousand miles an hour, well maybe 50. When you're not towing you could power half of Hall's Creek, well maybe a fridge and a telly and one of those things to burn off your solar keratoses.

    Imagine all the grey nomads with big arsed solar caravans putting around for free at 53kmh, wouldn't the truckies love 'em??
     
  14. phlogistician Banned Banned

    Messages:
    10,342
    You can create DC voltage boosters quite easily;

    http://www.reuk.co.uk/DC-Voltage-Multiplier-Circuit-Plans.htm

    But then of course you'd have to wiggle your lighting circuit to use the increased voltage.

    I guess we're looking at \( I^2R\) loss due to heating, so increasing voltage is the best way to decrease loss, but you could always just wire up your panels using 30A cooker circuit wire, nice solid copper wire to lower impedance. Or both.
     
  15. Blindman Valued Senior Member

    Messages:
    1,425
    Im in Perth at the moment. Traveled up to Port Hedland and then back along the inland route. Lots of sunlight

    Please Register or Log in to view the hidden image!

    The solar car is a bit of a stretch but ive been stuck behind some road trains doing 80kmh for 100k plus.
     
  16. elvinatom Registered Member

    Messages:
    36
    The only way is to go for thick gage wires or if you can afford it transform the voltage up. That's what's done on the grid: high voltage for long distance - then transformed down locally. At higher voltages the resistance of the wire becomes less of an issue.
     
  17. Blindman Valued Senior Member

    Messages:
    1,425
    There is near 35m from where I want the solar arrays (as the block has a line of trees on the north side). I will run the 35m direct from the PV panels to the charge controller. It will always maintain a higher voltage on the PV side.

    This distance is a significant power cost 4-6% (reasonable wire) but I think I can get 30% more sunlight.. So now to crawl in the roof space and put in some wiring. This should give me grid free lighting. Pitty its not cost free.

    Is there a battery that lasts forever (a very long time)???
     
  18. phlogistician Banned Banned

    Messages:
    10,342
    Yeah, the Holy Grail uses it as a display stand

    Please Register or Log in to view the hidden image!



    As you know, Lead/Acid need to be kept topped up and frost free. Some of the new LiPo batts like the new breed of electric vehicle use might be getting close to what you want. Haven't looked into price as I'm a light user, but as these things are ultimately consumables, in deep cycle applications the price will come down. Prob another five to ten years realistically though.
     
  19. Captain Kremmen All aboard, me Hearties! Valued Senior Member

    Messages:
    12,738

    In Australia, it's a wonder they aren't in use already.
    Imagine the power generated by a road train covered in panels.
    Cover the rocks in panels too. Stupid rocks.

    Please Register or Log in to view the hidden image!




    @Blindman.
    I have already predicted on this site that the person(s) who revolutionise battery technology will become the world's first trillionaires.

    Are you actually blind or partially sighted by the way?


    As regards solar power.
    Even in cloudy old Britain, they may become a feature of the landscape.
    Householders may be able to enter into a contract whereby a solar panel can be obtained from power companies in a contract similar to the way we pay for water.
    The panel should last for 25 years, conservative estimate, and pay for itself far sooner because excess power is fed into the grid at a premium rate.
    This also curbs excessive profiteering by the power companies.
     
    Last edited: Aug 7, 2010
  20. Spud Emperor solanaceous common tater Registered Senior Member

    Messages:
    3,899
    No, he's a fucking travelling awning salesman
     
  21. Captain Kremmen All aboard, me Hearties! Valued Senior Member

    Messages:
    12,738
    Well, if he's yawning, he should change his job.
    I hate bored salesmen.
    He might be selling walking sticks for geographically challenged white hamsters.
     
  22. Spud Emperor solanaceous common tater Registered Senior Member

    Messages:
    3,899
    Blindman,
    Port Hedland would have been fun.
    Kremmen, I reckon a solar rail line is the way to go. Put panels on all the freight cars and some auxillary ones along the track as required ( for hills and shit) they'd run up and down the track for decades with no emissions. How hard can it be?
     
  23. Blindman Valued Senior Member

    Messages:
    1,425
    Captain Kremmen I am not vision impaired. I just drink to much

    Please Register or Log in to view the hidden image!



    Spud Emperor, Port Hedland was great. I stayed about 50Km east as all the caravan parks where full. The desert was nice and green from recent rains.

    When you see the trains out there, 40000Tonnes, 3km long, seven locomotives. You would need a lot of solar power to move that lot safely.
     
Thread Status:
Not open for further replies.

Share This Page