100W solar panel

Geek said:
Connecting them was no trouble. They just didn't work!
As I said, no idea why not.
It didn't matter which order I connected them, when the second one was connected, the first one stopped charging within a few seconds. Seemed very odd to me.
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run = works. I certainly have run multiple controllers, as have countless others.
I would not put off anyone doing the same.
 
No, I doubt it was that, because the battery wasn't very full and it's voltage wasn't so high.

I suspected that it was unexpected variability in the voltage from the solar panel: neither controller able to make sense of how the voltage varied at different current draws. At least that's my best guess. But it is only a guess.
 
Geek said:
No, I doubt it was that, because the battery wasn't very full and it's voltage wasn't so high.
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What I meant was that the controller sensed the voltage being applied to the battery by the other and read that as the battery itself being at that voltage.

But one gathers from the interweb that, aa Wildebus says, that multiple chargers should work so I stand corrected.
 
Markd said:
What I meant was that the controller sensed the voltage being applied to the battery by the other and read that as the battery itself being at that voltage
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In this particular setup, there is one 65watt panel and one 200 watt panel. Whichever is connected first works just fine until a few seconds after the other controller is connected. The "added" controller never reports giving any charge at all.
Your suggestion would make a lot of sense if it happened when adding the 65w one to the already-connected 200w one, but it's just the same the other way round.
I really ought to retry the experiment using a different MPPT controller, and see whether different combinations works any better ..
 
I don't think the wattage is a relevant fact in my hypothesis - it's just the voltage present at the battery terminals.
The only problem is that it shouldn't be happening!!
 
Geek said:
Connecting them was no trouble. They just didn't work!
As I said, no idea why not.
It didn't matter which order I connected them, when the second one was connected, the first one stopped charging within a few seconds. Seemed very odd to me.
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That is strange, what makes of solar controller did you try this with? I have been running a Votronic Duo and Victron (both MPPT) to the same battery bank for a while now with no problem
 
Molly 3 said:
Are you connecting the 2 controllers the the battery first then adding solar panels last. As this is the correct way .
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It may indeed be the "correct" way, but in reality it doesn't matter.

If the controller can operate with 12v or 24v batteries, officially it should get the battery connection first to know what voltage to run at. You'd need something like 30v from the panels and a very high internal resistance in the batteries to fool it. In fact, I suspect that if the controller could be fooled, the batteries are shot already.

Just another of the "reverse polarity" scare story issues that make no difference at all except in a very few edge cases that you should never meet.

But because I was puzzled, I did try connecting the second controller before connecting its panel. As expected, it was the same.
 
Geek said:
It may indeed be the "correct" way, but in reality it doesn't matter.

If the controller can operate with 12v or 24v batteries, officially it should get the battery connection first to know what voltage to run at. You'd need something like 30v from the panels and a very high internal resistance in the batteries to fool it. In fact, I suspect that if the controller could be fooled, the batteries are shot already.

Just another of the "reverse polarity" scare story issues that make no difference at all except in a very few edge cases that you should never meet.

But because I was puzzled, I did try connecting the second controller before connecting its panel. As expected, it was the same.
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It absolutely DOES matter.

Apart from having a repeating problem that no one else seems to ever have, you are now giving very poor advice on how to connect up a product that in your hands doesn't work like it should. I wonder if the two could be connected? :unsure:
 
wildebus said:
It absolutely DOES matter.

Apart from having a repeating problem that no one else seems to ever have, you are now giving very poor advice on how to connect up a product that in your hands doesn't work like it should. I wonder if the two could be connected? :unsure:
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I connected the battery first and it didn't work.

I'm not giving advice that you shouldn't connect the battery first, but I am saying that in my experience it doesn't make a jot of difference.

What difference do you find that it makes?
 
Geek said:
I connected the battery first and it didn't work.

I'm not giving advice that you shouldn't connect the battery first, but I am saying that in my experience it doesn't make a jot of difference.

What difference do you find that it makes?
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It configures the controller to know what battery voltage it is running on, as has been said, but you said is unimportant for some reason. I am not going to explain futher other than to say RTFM - suffice to say that you think it unimportant to do the basics correctly, and for some reason unknown to you or anyone else you cannot make two solar controllers work on the same battery at the same time despite no one else having that issue (so TBH, your apparent experience of setting up Solar Controllers is hardly stellar), so try doing things in the right order and you might get somewhere?
 
I asked you whether you have found that connecting the battery first makes any difference. You seem to have overlooked that question.
 
I have three mppt's charging the same batteries, with the option to add a fourth. Works just fine. You have to connect the battery first, how else will it know what charge mode to go into?
 
That's a whole different can of worms. If you have more than one charger (of any sort) connected, there isn't any way that they can assess the state of charge.
 
Geek said:
I asked you whether you have found that connecting the battery first makes any difference. You seem to have overlooked that question.
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makes a difference compared to doing it the other way round? wouldn't know as I only do it the right way round ;)
 
Geek said:
So you are happy to tell me I'm wrong but you haven't tried it.
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Why on earth would I do something wrong deliberately? Life is too short. But if you are happy not having things working right, good for you :D

PS. this conversation is boring and pointless, so leave me out of it from now on. I won't be replying to your comments on it as you clearly know just what you are doing ;)
 
That is the point. It works perfectly well even if I connect the solar panels first. That makes no difference. I speak from real world experience.

The fact that adding a second controller won't work for me is indeed puzzling. It definitely isn't related to connecting the panel first, because I didn't.

I must find time to try two different controllers: I have four different ones of various makes and three lots of panels, so there are lots of possible combinations to try.
 
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