Fitting solar at Techenders

Discussion in 'Mech Tech' started by scrooge95, Mar 17, 2018.

  1. Cool. Thanks
  2. There are different mixtures of metal in the plates of the batteries and different construction. You can design a battery to start a big engine - high current but low capacity so recharges quickly once a day.
    Different design for stop/start engines where the start happens 10's of times a day.
    Design a battery for deep discharge but low current and high capacity.
    Design for deep discharge and many charge cycles and lower capacity.

    In general the higher a a capacity quoted for a battery of a given size the fewer charge cycles it will survive and the fewer total discharge events it will survive.
    And the lighter a battery of a given capacity is the less time it will serve.
    Thin plates give high capacity but fall apart.
    Batteries without empty space below the plates for plate fragments to collect will short out sooner. (The empty space lowers capacity for the same size of case)

    With 200 watts of solar panels you can pick up useful charge on even dull days so the battery can be more oriented to deep discharge and many charge cycles, but never left flat for a long time.
    If it were not for their different charge characteristics.. like they wont charge properly off an alternator split charge if the starter battery is classic wet cell lead-acid , the AGM battery is a good choice with a solar cell.. or Lithium Ion...

    I currently use an old 096 starter battery as a leisure battery with 200 watt solar cells and a split charger. I trashed several leisure wet cell batteries before fitting solar.

    Now I keep fresh food in the fridge and drive to work and use it for lunch. Over weekends I leave the fridge on and the leisure battery is still at 12.5 volts on Monday morning..

    I dont bother with the 10 amp maintenance charger built into the inverter unless I want 240v in the bus for other reasons and I have hookup available.
  3. I will fitting a split charge system that can take solar panels, at tech Enders, so I will be super interested to see how you guys get on.... watching with interest.
    scrooge95 likes this.
  4. So what you're saying is I can go for a lower capacity battery because it will be constantly topped up by the solar panel, and that the lower capacity ones are more robust than the higher capacity ones? Cool, thanks Mike.
    The spare I've got will do for a bit, certainly good enough to get the solar sorted at TE, and you never know - Andy's ctek might be able to revive the newer dead one (vague hope!)
  5. He is saying he likes fresh food for lunch :)
    scrooge95 likes this.
  6. If you ask ahead, as well as a good price on gas bottles, Eddie does a good price on a couple of sizes of leisure batteries.
    The big one wont fit in a bus if I remember right when @Lord Congi tried one in his bay he was using before his palatial T5.
    scrooge95 likes this.
  7. We have 4x80watt solar panels on the T4 (which will probably be transplanted to the T2). Currently they’re all set up in parallel (so voltage same(20v) and current multiplied 4x5 amps).
    Thinking of putting them on in 2 lots of 2, so 40v but only 10amps.
    Reason for this thinking is winter charging. I think with lower light levels it’ll get above 13.5 volts sooner in the day and put something back into the battery on the greyest of days. Also, higher voltage means less cable loss, but the runs aren’t that long and the cable fat enough for me to think that’s not too significant.
    Someone check my thinking please?
    Using a Victron 75/15 mppt controller.

    Sent from my iPhone using Tapatalk Pro
  8. Yes so i can keep packs of ham and cheese ad make sanwiches.

    And having solar cells alters alters the electrical "profit and loss" towards smaller deep cycle batteries.
  9. Basically get the heaviest battery you can fit in the space
    Iain McAvoy likes this.
  10. Seems like a plan. Make sure the series panels have diodes in parallel so if one is shadowed the other one can still deliver current through the diode. Some panels have these builtin - mine have two diodes so even partial shade does not kill the output of a single panel.
    On an installation with 8 panels in 2 chains of 4, the built in diodes started getting too hot and failed and sea water and 80 volts fizzed the wires off the end of the panel. So they skipped the panels and I scroinged two.
    Weasel likes this.
  11. If you're at Techenders I might have to draw that on a scrap of paper to understand it! I'm certain there's one diode on each of the panels but I just thought that was there to stop them "going backwards" at night time! I've not got my head around how shading or partial shading affects an array of panels. And whether that happens at each 6" square cell or each 3' panel.

    Thanks for all the information
  12. If a single cell is shadowed it stops producing power. Even the shadow of a rope or a twig is enough. The shadowed cell becomes a high resistance and the whole stack of 38 or 40 cells in a panel basically stop producing power. Sketch808129.png
    If you put in parallel diodes aranged to conduct if the voltage across the panel or part of the panel is reversed the current from the still working cells manages to reach the terminations of the panel or the end of the stack and you still get power.
    In an ideal world, every cell would have a diode but this is expensive and hard to assemble. So like on my panels there is a diode across the first 20 and the second 20 cells.. if its shadowed it still makes 9 volts.

    The reverse blocking diode you mention is needed for installations where your controller is not able to isolate the panel from the battery at night.

    A Victron MPPT is a quality product so you dont need that diode.
    And with 4 panels the chance of at least one getting clear sunlight is high..
    Merlin Cat, snotty, Valveandy and 3 others like this.
  13. So I thought I'd use this thread rather than starting another, to ask a couple of questions about the MPPT controller for the solar panel....
    Needless to say, the solar install didn't go quite to plan at Techenders, owing to the pis...... sisting rain, but @mikedjames helped me tackle the wiring side of things before we left on Sunday, so that I at least had the cables in place from the top of the pop-top down into the wardrobe ready for the controller.
    The rest of the installation I finished off myself this bank holiday weekend.
    Lo! It works.
    Cables from solar panel to controller, via a fuse in the + , then from the controller to the leisure battery in the engine bay, again fused in the + cable.
    Nothing connected to the 'LOAD' terminals as everything will be powered by the leisure battery, and this will be topped up by the solar panel. I think this is fairly standard in a van set up, with the load option mostly being used in a household or garden installation for running low energy lighting etc.
    Anyhow, according to the instructions, the 'Enter' button on my controller will turn off the load option. But every morning when the sun comes up and the controller wakes up - it turns the load option on again.
    If I turn the Load option off, it goes to bed looking like this:
    controller without load.jpg

    But in the morning it's back to this:
    controller with load.jpg

    Does it matter?
    Or is there something I'm supposed to do in a menu somewhere? I found the instruction booklet quite technical and hard to follow with all its parameters and stuff, so at the moment it's all on the default setting.
    Anyone with this kind of controller, what does yours do? @1973daisey @Razzyh @pkrboo @theBusmonkey
  14. Oh I’ve not done anything with mine. I wouldn’t worry to much as there is nothing connected to it so won’t drain the juice.

    I think the only setting I looked at was the battery type gel/acid/???

    Maybe I should get the book out and have a read
    scrooge95 likes this.
  15. Basically, no don't worry. Load is normally set to come on at sunset and off again when the solar panel starts producing power.

    It's so that a solar panel can charge a battery up during the day and then the controller auto switches on a light (like a security light)

    There may be a way to set I to be off all the time
    1973daisey and scrooge95 like this.
  16. Has anyone pointed out that we only have sunshine in this country for three days a year?
    art b likes this.
  17. Yes but that’s when we use our vans so it’s all good :)
    scrooge95 likes this.
  18. Okay that's good, nothing to worry about, thanks :thumbsup:
    1973daisey likes this.
  19. You don’t need sunshine for solar to work
    pkrboo likes this.
  20. I have no idea as our controller is different but as the guys said above, the load function is for feeding a live-out to power a light or something from the panel.
    I have wired a 12v socket into the spare terminals on the controller that feed the load, which we run the shower off for example…:) On our controller I can turn the load on and off.
    scrooge95 likes this.

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