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  1. #11
    Hmm fair enough...

    Quote Originally Posted by blackburn mark View Post
    this charge controller will take 38v open circuit, i'm sure that's pretty typical for a cheap 250w panel
    But does it accept 38V with a 12V battery on the output, or just with a 24V battery? Looks like you've got this one, but the listing isn't helpful:

    800W Wind Solar Hybrid Mppt Controller (600W Wind + 300W Solar) 12V/24V Auto | eBay

    It looks like at least some support having a lower voltage battery, but I'd want to be sure before connecting it up...
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  2. #12
    yep, it looks identical to that one... mine stated 200W for solar, 38v for 12v charging and 46v for 24v charging... my thinking was seeing a real 250 watts from a 250w panel would be pretty rare in this country and on the occasion that it did it would just be wasted... wouldn't make it to the battery through this charger ?

    I might have bought a lemon with this... it didn't come with any instructions at all and the menu isn't very logical
    you win some and you bin some :)

  3. #13
    Quote Originally Posted by blackburn mark View Post
    46v for 24v charging
    A nominally 24V (72 cell) panel can output close to 46Voc in bright sunlight, so the controller would have to drop the voltage from around that to about(!) 10.5-15V. It depends on how they've designed the converter...

    Quote Originally Posted by blackburn mark View Post
    ... my thinking was seeing a real 250 watts from a 250w panel would be pretty rare in this country and on the occasion that it did it would just be wasted... wouldn't make it to the battery through this charger ?
    The controller will either overheat and cut-out, or if it has a few more brain cells it will regulate the power input to only what it is rated for, so 200W. Solar panels are rated at an irradiance of 1000W/m^2, which is typical in England in the summer.

    Quote Originally Posted by blackburn mark View Post
    you win some and you bin some :)
    Well let me know if you bin it ;)
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  4. #14
    Well let me know if you bin it ;)
    ha!... it'll probably smell of burned Bakelite by then :)

  5. #15
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Current Activity: Viewing Has been a member for 9-10 years. Has a total post count of 1,831. Received thanks 192 times, giving thanks to others 5 times.
    I did just type a big response, but just hit the wrong button, so here's just the summary!

    Running a full split charge system will not cost you much on terms of fuel.
    Even relying on the vehicle to fully charge the Aux batteries from totally flat, and assuming poor engine and alternator efficiency, will only take around a litre of diesel in addition to what you're taking to drive around. If you use the wind/solar to provide a continual charge, then the vehicle will not see that much of an increased load. Even if the batteries add an additional continual 20A load, it's only an additional 100ml of diesel an hour needed.

    As for what split charge system to use, I'd personally build one using a large relay (200A range), and an Arduino.
    Programme it so it monitors the vehicle battery, when it hits a set voltage, it connects the relay, if the vehicle voltage then drops too much, have it drop-out until the vehicle voltage recovers then add an additional time delay (will stop the relay continually switching in a short time frame, and give the alternator a rest instead of hammering it continually), and repeat until voltages stabilise. You could also programme it so it doesn't charge the Aux if the Aux batteries are above a set voltage.
    That way you should get a reliable system, without the issues with conventional relay systems, and without the over-priced 'smart' systems.


    Alsom, if you're van is only putting out 13.5V, then it has issues. It should be above 14V. Is it an old D, or a newer CDI?

  6. #16
    I did just type a big response, but just hit the wrong button, so here's just the summary!
    owch! i hate that

    I am having second thoughts about my tactics (ish)
    its an 08 CDI and I measured through the lighter socket with a cheap meter... ill take my fluke out tomorrow and see what It reads at some heavier terminals

    I have been convinced that I should be pushing 14.8v into my auxiliaries for at least an hour after they stop drawing lots of current... if I can get anywhere near that out of my alternator ill go with a split and maybe boost the voltage a tad somehow....id have to manually isolate it though... and watch an amp meter for it to tail off... why is shit never easy ? LOL

  7. #17
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Current Activity: Viewing Has been a member for 9-10 years. Has a total post count of 1,831. Received thanks 192 times, giving thanks to others 5 times.
    A CDI should get around 14.2V at the battery terminals after being running for a short period. If you're not, it's most likely the main positive loom has got corrosion in it at the starter terminal. Check to see if you're getting over 14.2V at the alternator, then check for volt drop between the battery positive and the alternator main output.
    You can either remove the loom, drill two holes in line with the end of the cables and using a blow lamp/oxy-acy torch run plenty solder through the crimps, or just get a new loom.


    14.8V?
    That's really only needed if you're bulk charging the batteries after they've been run down. And to acheive that voltage on that much capacity, will take a lot of current!
    Provided the solar is doing a good job of reguarly keeping the batteries around 13.2-13.5V, the continual trickle charge should keep them conditioned.


    You're not using AGM batteries are you?
    If you are, then you'll need some way of limiting current when charging, otherwise they'll pull every last bit of power from the vehicle they can when charging. They absorb charge far quicker than conventional lead acid batteries, and the voltage doesn't rise until they've got that charge.
    We maintain some vehicles that have had AGMs fitted on the vehicle, and I've seen a flat one sit pulling 20A from a battery charger for 30minutes before the voltage even creeped above 12V, and if you jump start one, you can hear the load on the alternator and the voltage gradually creeps up.

  8. #18
    morning MC... i wasnt going out in that rain yesterday!!... the battery is showing 12.3v before startup so i think that is on its way out (the little indicator on the battery is confirms this)

    its showing 14.23v when its running, thats stable even if i increase revs, this has me thinking that maybe the van would push it at more like 14.4v and the tired battery is pulling it down ? ill look into this.

    im looking to put standard wet batteries in, they sell as deap cycle 125ah but im guessing they are just re labled as such (ebay...love it)
    iv taken the advice that the cheaper the better... with good charge control should last quite well... nothing like AGM's and the like but they really are a tad pricey

    iv done a bit of research on the voltage issue, an article by a guy who has lived in his van for 8 years (and never used a genny) is charging at the much higher voltages, holding that voltage at least an hour passed the usual current drop (tempriture compensated)

    i think most charge solar/wind controllers and car/van charge systems aire on the safe side (totally understandable...zero maintainence)
    so i really want to hang on to the option to push the volage up should the need arise

    i think the world is split on the issue of charge voltages for standard wet lead... i think having voltage options a hydrometer and a pen and paper might be the way to go :)

  9. #19
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Current Activity: Viewing Has been a member for 9-10 years. Has a total post count of 1,831. Received thanks 192 times, giving thanks to others 5 times.
    14.2V is about as good as you'll get at the battery. I work on sprinters with 150A alternators (standard is 120A), and even after sitting running for a couple hours, they'll still be around 14.2V. Even with a brand new loom, there is always a bit of voltage drop between the alternator and battery.

    A bad battery will not pull the alternator voltage down, unless a cell has gone short circuit, which means it'll get warm very quickly, and gas lots. A bad battery is more likely to go high resistance, which means it's actually easier for the alternator to hold the regulated voltage.

    Deep cycle batteries do have a different internal construction. Normal starting batteries are designed to output high currents, with the trade of being they're not as good at prolonged drains or being run flat for extended periods of time, whereas deep cycle are designed to handle lower currents, and have better recovery from being left discharged.

  10. #20
    I work on sprinters
    splendid :) i know who to hassle if i get stuck... you dont use the star software do you :)

    Deep cycle batteries do have a different internal construction.
    i was assuming the worst with buying from ebay

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