connection order

leaf
leaf Solar Expert Posts: 37 ✭✭✭
in General Solar Power Topics #1
I'm reconnecting up a basic 12V system in a house truck made up of:

solar panel

solar controller

voltage sensitive relay unit

house battery

truck battery

I have a diagram of how to do that (from before I took it apart), but am wondering if there is a correct order to connect all that. I've turned the mains off into the house, but am unsure what to do with the two batteries and the panel which are all live.

(the two batteries are connected via the VSR so that the truck charges the house battery when the engine is running).
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: connection order

    Try to reconnect the batteries when there is little sunlight (or the solar array is turned off/disconnected or charge controller fuse is pulled).

    For the most part, heavy loads/charging current can cause good sized sparks which may "surprise" you (cause you to flinch and short something else out with bad results) or even light off the hydrogen gas inside the battery cells (make sure batteries are well ventilated, wear safety glasses, and some folk like to cover the tops of the batteries where they are not working with something like a thick towel).

    Review the charge controller manual... Most charge controllers have you connect the battery first before connecting solar panels (charge controller resets and sets its voltage to 12 or 24 volt battery bank)... A few have it done the opposite way.

    Also, for your loads, have them connected to the battery bank before the solar panels/charge controller is connected... With some (probably older, cheaper, charge controllers) it is possible for them to "over voltage" if the solar panels are attached and the controller is not connected to the battery bank (i.e., the 17-21 volts of the solar panels exceeds the 15 volt maximum of the loads).

    Also, it is not a bad idea to tape your metal tools that you use to work on the battery bank with electrical tape. If you drop a tool or swing a wrench too far, you don't get an accidental short (your bank is pretty small, but it is not unusual to spot weld tools to battery terminals/wiring--and have things go downhill from there as you try and rip out the spot-welded tool).

    For the most part, if you are just careful that you have the polarities correct--reconnecting is not that bad/dangerous... The above does further reduce the risks of something going wrong.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • leaf
    leaf Solar Expert Posts: 37 ✭✭✭
    #3
    Re: connection order

    Thanks. Sounds like if I take normal precautions, and connect controller, then VSR, then batteries, then the solar panel I should be ok.
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  • leaf
    leaf Solar Expert Posts: 37 ✭✭✭
    #4
    Re: connection order

    Everything is connected up ok, but the controller isn't working properly (it's putting out the same as the panel). When I fitted it, a stray wire end did hit the wrong terminal on the controller and there was a spark. is that enough to wreck it?

    It's a morningstar sunsaver 10, and appears to be a sealed unit (I can get the cover off the old one I am replacing, but inside it's sealed). Does this mean there is no replaceable fuse?

    Is there any way to test a controller without fitting? I bought two, and would like to see if the second one is faulty as well.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #5
    Re: connection order

    I believe that is a PWM charge controller... So if the Battery is at 13.8 volts (and charging), the PWM controller is "on" and the output voltage of the solar panels will also be around 13.8 or 14.0 volts (i.e., the solar panels are directly connected to the battery bank). You should also be seeing current going into the battery bank (maximum current for solar conditions).

    If the panels are reading 17-21 volts or so, and the output of the charge controller is also reading 17-21 volts and the battery is reading 12.x volts--then the connection between the charge controller and the battery bank is not good.

    If you see 12.0-12.6 volts on the battery and 12.x volts on the solar panels (i.e., battery resting voltage), then your panels may not be outputting any current (open somewhere on the solar array side).

    It does get a bit tricky, if your batteries are well discharged, they will not go over 13-14.x volts for awhile--The battery does take time to recharge if it is way discharged at the beginning of the charging cycle.

    Most charge controllers do not seem to include an internal fuse.

    And, for the most part, you have to install the 2nd charge controller to see if it working OK.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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