Connect a battery to the "light bulb" section on a solar controller

Submitted: Monday, Nov 17, 2014 at 15:32
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Can I connect a battery to the "light bulb" section of a solar controller and still regulate the solar charge to my battery safely? I have a basic CMTPO2 controller, but one of the screw down slots on the controller used for the wires that go to the battery is not holding and the wire keeps falling out. I was hoping I could just move the wires up to the next section with the "light bulb" symbol. Could one of the solar techies on here help please. It would be greatly appreciated.
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Reply By: HKB Electronics - Monday, Nov 17, 2014 at 15:53

Monday, Nov 17, 2014 at 15:53
There's a few question marks for this one.

The light bulb terminals are for load, most controllers power these through a low
voltage cutout. Your problem will be the regulator expects to see a battery connected
to the battery terminals and may not start charging, if by some chance it does turn on then connecting the battery to the load terminals might work ok but not the ideal situation.

Have you considered using a bigger screw and re-tapping the thread?

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Leigh

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Follow Up By: Joan K - Monday, Nov 17, 2014 at 19:59

Monday, Nov 17, 2014 at 19:59
I thought something like that might be the case. I can't get the screw out and the little wind down clamp thing inside seems to be stuck open even when I tighten the screw. If I can get it out I will try a bigger screw.
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Follow Up By: Member - Frank P (NSW) - Monday, Nov 17, 2014 at 20:20

Monday, Nov 17, 2014 at 20:20
As an emergency...

Get the old screw out.

Cut a small piece of metal from a food can that will just fit in the terminal above the wire (polish the lacquer off it first so it's shiny bare metal). You can cut a sardine can with scissors.

Put the wire in, place your small bit of metal on top (or maybe make it U-shaped so it fits around end of the wire) and then drive a self-tapper screw to hold it all down. Just make sure all metal is clean and shiny.

Necessity is the mother of invention.

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Follow Up By: Joan K - Monday, Nov 17, 2014 at 20:34

Monday, Nov 17, 2014 at 20:34
Very innovative Frank P. This is easier than soldering lol.....for me anyway. I may not even need a screw. I can see it just jammed tightly in the slot. All ideas well worth a try.
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Follow Up By: Joan K - Monday, Nov 17, 2014 at 20:52

Monday, Nov 17, 2014 at 20:52
Leigh, What are your thoughts please on Ed C's idea of just moving the negative across and leaving the positive where it is. Is it safe to link the different sections? It's a very cheap basic regulator, on the back of a panel from "Bit deals" on Ebay, so feel a little concerned about how well the thing will perform. I'd probably feel more confident if it was a Morning Star.
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Reply By: Member - Ed C (QLD) - Monday, Nov 17, 2014 at 16:50

Monday, Nov 17, 2014 at 16:50
Is it the Positive, or Negative wire that's not holding?

If it's Neg, then moving this wire to an adjacent -ve terminal should work, as I'd assume that all the -ve terminals are bridged anyway.. (they are on my Morningstar)

Not so if it's the Positive terminal though..
As stated above, the controller will need to see a battery connected to the 'Batt' terminal in order to function correctly..

:)










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"He who lie underneath automobile with tool in hand,
....Not necessarily mechanic!!"

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Follow Up By: Joan K - Monday, Nov 17, 2014 at 20:04

Monday, Nov 17, 2014 at 20:04
Yes it's the negative that falls out. If you think it is safe I will move it across and leave the positive where it is to let the controller know I want the battery charged. I'll try this idea first until I can figure out how to fix the broken screw.
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Reply By: Sand Man (SA) - Monday, Nov 17, 2014 at 18:29

Monday, Nov 17, 2014 at 18:29
Joan,

The simplest way would be to solder the wire to the same terminal block location.
Bill


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Follow Up By: Joan K - Monday, Nov 17, 2014 at 20:11

Monday, Nov 17, 2014 at 20:11
Soldering is not my best feature, I'm afraid. LOL I'm likely to melt the whole thing and not have a controller at all. My soldering skills are totally pathetic. But I'll keep it in mind in case someone turns up who can do it for me.
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Reply By: Shaker - Monday, Nov 17, 2014 at 20:28

Monday, Nov 17, 2014 at 20:28
I was under the impression that the "light bulb" terminals were to run a light cell activated dusk to dawn night/security light.

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Reply By: The Bantam - Wednesday, Nov 19, 2014 at 12:06

Wednesday, Nov 19, 2014 at 12:06
before you start getting all excited and start butchering the thing.

You'd be best carefully getting the screw in question out.

It may well be that the screw its self is ringbarked.

If the wires will come out of the terminal....slip one or a couple of small blade screwdrivers under the terminal, and help it as you try and unscrew.

Then take one of the good unused screws from a vacant terminal, screw that in and see if it holds.

I have come across this exact problem many times......the above is not the fix every time.....but it works a lot of times.


OH another non butcherous solution.....in some of these terminal blocks the screws are less than wonderfull.....mostly they are cheap rolled threads and the thread depth and form is not what it should be.
If you work out the correct thread, a good quality machined screw will hold where what came will not.....sometimes the good quality screw has to be pushed thru, because the thread form in the terminal is not wonderfull either....if you have to push the new screw thru....check the treads after...it may be wise to have a second screw on hand and throw the first one away and put a fresh screw.

Most of these terminals are either M3 or M4 standard pitch these days.

If ya gona start soldering and all that sort of thing....best to find someone with the skills and replace the terminal block.....it will most likely be one of the standard forms...you may find a better quality terminal to replace it with.



cheers
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Follow Up By: Joan K - Thursday, Nov 20, 2014 at 07:54

Thursday, Nov 20, 2014 at 07:54
Thanks Bantam, I'll get it out somehow. I may need to buy a better screw driver as the screw and the access to it are so tiny. The screw seems to tighten and loosen OK, but the little clamp that the screw pushes down onto the wire won't budge. Perhaps a new screw/s as suggested will work. The regulator is cheap..it's a CMTPO2 that Ebay sells.
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Follow Up By: Member - Frank P (NSW) - Thursday, Nov 20, 2014 at 09:09

Thursday, Nov 20, 2014 at 09:09
Can you lever that clamp with a small tool after loosening the screw?
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Follow Up By: Joan K - Friday, Nov 21, 2014 at 16:00

Friday, Nov 21, 2014 at 16:00
I'll have to try next week when I get back and let you know.
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Follow Up By: Member - Frank P (NSW) - Friday, Nov 21, 2014 at 16:26

Friday, Nov 21, 2014 at 16:26
Joan,

I just saw the regulator on eBay. 30 amp MPPT regulator for $16 to $20? I don't think so. A reputable and durable 30A MPPT would more likely be priced around $150 to $200.

If I were you I'd chuck it and buy something half decent from a reputable Aussie on-line or shop-front supplier.

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