What makes an MPPT 'take a break'?

[solarstuff]

This weekend my Renogy Rover Li 30a MPPT decided it no longer accepted solar charge from my panels.

When I swapped it with the Rover Li on my other array of panels (both 3x100watt), it still wouldn't work.
I figured I'd blown something inside or it had otherwise malfunctioned...but today I plugged it back in to troubleshoot and...it just works.

Same-ish temperature and sunlight as before, so...what happened? I thought if I'd blown a fuse I'd have to tear the MPPT down and repair a fuse.
Similarly I thought if some charge protection had kicked in it would reset itself or stay broken.

I've checked online, no idea why it needed a couple days to rest and suddenly work again!
Any advice about how to test, or if I should or shouldn't worry about it's capacity, would be much appreciated.

 

[John Frum]

If you have a dvom please take some voltage measurements.
What is the voltage on the pv side of the solar charge controller?
What is the voltage on the system side of the solar charge controller?
What battery chemistry do you have?
Do you have a shunt based battery monitor?

 

[solarstuff]

If you have a dvom please take some voltage measurements.
What is the voltage on the pv side of the solar charge controller?
What is the voltage on the system side of the solar charge controller?
What battery chemistry do you have?
Do you have a shunt based battery monitor?

15.8 in to controller from solar
13.5 out to battery (under load, we're making yogurt

No shunt-based battery monitor attached (I bought an Ai-li but they sent the wiring for the wrong model, and I haven't bought a new one yet).

EDIT: battery chemistry is AGM (4x100Ah)
Max Solar Input Voltage: 100VDC according to mfg

 

[John Frum]

15.8 in to controller from solar
13.5 out to battery (under load, we're making yogurt

No shunt-based battery monitor attached (I bought an Ai-li but they sent the wiring for the wrong model, and I haven't bought a new one yet).

EDIT: battery chemistry is AGM (4x100Ah)
Max Solar Input Voltage: 100VDC according to mfg

I'm guessing things are currently working.
A wild guess is that there is nothing wrong with the solar charge controller as you swapped it out and the problem persisted.
Another wild guess is that perhaps the battery was charged therefore no potential difference existed so no current could flow.

 

[solarstuff]

I'm guessing things are currently working.
A wild guess is that there is nothing wrong with the solar charge controller as you swapped it out and the problem persisted.
Another wild guess is that perhaps the battery was charged therefore no potential difference existed so no current could flow.

You're probably right about your wild guess (grin)...but I have two mppt's on this battery, each fed by two different arrays of 3x100w.

One read as charging (at 11 am) and one read as full. When I pulled the OTHER mppt off, this read not charging. When I pulled THIS mppt off, the other read 'charging'. Or at least that's what the pics I took made me think.

I know I'm up against my limit here knowledge wise, so I try to listen to you experts...and whatever the problem, it's not happening anymore (and there's 4 months left on the warranty, so (I have breathing room).

Thanks!

 

[Mike Jordan]

One bank of panels partially shaded so they could not make power above batt voltage?

 

[solarstuff]

Maybe! There's not much to shade them but they are on different angles.

I've got the heavier mppt (40a vs 30a) attached to the panels that caused the problem/read as overcharged...best I can think until there's another symptom/problem.

 

[John Frum]

You're probably right about your wild guess (grin)...but I have two mppt's on this battery, each fed by two different arrays of 3x100w.

One read as charging (at 11 am) and one read as full. When I pulled the OTHER mppt off, this read not charging. When I pulled THIS mppt off, the other read 'charging'. Or at least that's what the pics I took made me think.

I know I'm up against my limit here knowledge wise, so I try to listen to you experts...and whatever the problem, it's not happening anymore (and there's 4 months left on the warranty, so (I have breathing room).

Thanks!

Do the same voltage checks if/when the problem returns.
Make sure the charge controllers are using identical charge profiles.

 

[JMH1783]

A couple of things come to mind that might help. First are your panels in series or parallel? If in parallel you might not have enough voltage for the mppt controller. If you can remove both charging and load from the batteries, give them a half hour and take a voltage reading. Are they full? It is difficult to get a good idea of charge while the current is flowing in or out.

 

[solarstuff]

A couple of things come to mind that might help. First are your panels in series or parallel? If in parallel you might not have enough voltage for the mppt controller. If you can remove both charging and load from the batteries, give them a half hour and take a voltage reading. Are they full? It is difficult to get a good idea of charge while the current is flowing in or out.

I'll try that tonight, for sure.