Should my MPPT controller drop to 0 amps coming in, from solar panels only, for a few seconds before building back up to 16 amps or so, depending on the sun, stay there for a minute or so & then drop back to 0 amps for a few seconds again & repeat this cycle?

Is this normal behaviour?

I have a 60A Mppt Controller; 550W Solar Panels; 780Ah (6 x 130A) batteries.

I only started watching what happens because I'm not getting fully charged batteries recently. The batteries have always been fully charged when running fridge & freezer 24/7 until recently. I have disconnected the freezer last week & fridge today to try & isolate the fault.

I'm pretty sure it's not the controller as I just bought a new one because the previous Mppt controller did the same but worse - it was 40A & not big enough.

I've pulled all the batteries out to check individually & they all have exactly the same voltage.

I'll be checking what amps the fridge is drawing next week & checking if something is remaining "on" that shouldn't.

It's got me beat!!

TIA
Larry

Sounds like you may have a battery in the bank not playing ball. If you can isolate 5 of the batteries from the bank and only run on one battery and see what happens then. I would also have all the batteries individually load tested. I also have six batteries in my house bank with individual isolators on each battery. Several times a year each batteries is individually charged by a multi stage charger so as each battery is bought up to fully charge without the influence of another battery which could have a different internal resistance which does change as the battery get older.

Hi Lazzz,
A DC Clamp meter is invaluable for measuring DC currents. With a clamp meter, you simply close the clamp around a wire to read what current is flowing in it - no need to disconnect wires as with other types of current measuring meters.
Here's an example http://www.jaycar.com.au/400a-ac-dc-clampmeter/p/QM1563.







regards,
Allan

Another possibility is it could be a bad connection somewhere. The suspect connection might be good enough to give the MPPT a voltage reading but goes high resistance under load (high current). The MPPT wouldn't think it connected to a battery then and shut down.

I have also seen batteries with higher internal impedance than they should have do something similar to chargers. When the battery is sitting there with no current going through it it looks fine. Once you start to charge the battery, it results in a higher terminal voltage due the higher internal impedance. (V=IR) and the charger sees this as a charged battery and reduces the charge current.

good luck.

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Crusoe said..
Another possibility is it could be a bad connection somewhere. The suspect connection might be good enough to give the MPPT a voltage reading but goes high resistance under load (high current). The MPPT wouldn't think it connected to a battery then and shut down.

This crossed my mind - I actually have a new fuse holder on it's way because I don't like the look of the old one.
The batteries are only 3 years old, they say I should get at least 10, so I'm hoping it's not them.

Thanks for the ideas fellas, I'll know more after Wednesday when I do some testing.

I'll definitely try it with one battery Jode5 & see what happens. It is a major operation to charge each battery with a charger because I'm on a swing mooring but I think I'll give it a go.

I'll see how I go first Allen before parting with my hard earned!! I have a volt/amp meter connected using this type of connection.

Cheers,
Larry

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Lazzz said..

Crusoe said..
Another possibility is it could be a bad connection somewhere. The suspect connection might be good enough to give the MPPT a voltage reading but goes high resistance under load (high current). The MPPT wouldn't think it connected to a battery then and shut down.

This crossed my mind - I actually have a new fuse holder on it's way because I don't like the look of the old one.
The batteries are only 3 years old, they say I should get at least 10, so I'm hoping it's not them.

Thanks for the ideas fellas, I'll know more after Wednesday when I do some testing.

I'll definitely try it with one battery Jode5 & see what happens. It is a major operation to charge each battery with a charger because I'm on a swing mooring but I think I'll give it a go.

I'll see how I go first Allen before parting with my hard earned!! I have a volt/amp meter connected using this type of connection.

Cheers,
Larry

With 6 batteries in parallel and never been on a charger or even individually fully charged from the motor you will be lucky to get better than 3 years before you start to have problems. My boat was originally set up with all six batteries in parallel and all just connected to the individual regulators from the motor, solar and charger. Two batteries died in eighteen month. The boat was reconfigured and all six batteries were replaced under the boats warranty, not just the 2 faulty batteries as it is important to have matched batteries in big banks.
lets just hope that this is not the problem with your solar, but when you run on one battery (provided your don't pick the faulty one) you will soon see what is happening.
good luck.
ps. If you are still having problems after you try one battery, PM me with your phone number and I will give you a call as there are quite a number of options depending on what is happening.
John

Dropping the charging current to 0 and measuring the float voltage is common for charging NiMH batteries, but not Lead Acid as far as I know. Which model MPPT controller is it?

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nebbian said..
Dropping the charging current to 0 and measuring the float voltage is common for charging NiMH batteries, but not Lead Acid as far as I know. Which model MPPT controller is it?

Good thinking Nebbian.....the 'symptoms' may be by design.
I have a feeling my Jaycar MMPT does the same thing - didn't give it much thought....
regards,
Allan

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nebbian said..
Dropping the charging current to 0 and measuring the float voltage is common for charging NiMH batteries, but not Lead Acid as far as I know. Which model MPPT controller is it?

I now have a 60A MPPT eSmart3 Solar Charge Controller - I like that this one has a cooling fan.


I was previously running a 40A Epever with MT50 & it would drop back to zero amps but for a lot longer before climbing back up - the sun would turn to a moon :(







Prior to this I had a 80A PWM





Thanks for your generous offer Jode5 - I'll see what develops.

Its not necessarily faulty at all!

MPPT chargers need to find the point at which they get the most power out of a solar panel at a given time by varying the load.

Its common to use a PWM internal regulator that repeatedly loads the panel lightly (feeding its power output to the battery) then ramps the load up until the power being taken out from the panel starts to dip (ie past the MPPT point) then set the load at that level for a period of time at that.

(Example - if a solar panel is putting out 30V with a 4A load on it (120W) when you increase the load to 5A the output voltage might not dip (now up to 150W). ie. Panel can handle it. But increase the load to 6A might make the panel voltage collapse down to 15V. Too much. Power is now only 90W, we are past the MPPT point so use the software to go back and find the load that gets us 150W which is the maximum power point in this case.)

The designs of all solar regulators are different like boats. The big criteria is are the batteries charged and staying charged.

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Trek said..
Its not necessarily faulty at all!

MPPT chargers need to find the point at which they get the most power out of a solar panel at a given time by varying the load.

The big criteria is are the batteries charged and staying charged.

I think this is the case.

I thought the fridge might have been playing up & drawing more current but after checking today it's not the fridge - or anything else drawing current.
With everything turned off I'm only drawing 13mA (radio etc) & with my Pi3, which runs 24/7, it only draws 0.7A.

After turning all but the Pi3 off on Saturday I went to the boat today & found the battery bank still at 12.5V - half charged instead of fully charged.

I took Jode5's advice & isolated the batteries & had only one hooked up to the system. The MPPT controller still did the same thing but the single battery was fully charged up to 14.2V in a few hours on solar alone on a rainy, cloudy day. I'll do the same for the other 5 each visit to the boat & hope they do the same & I don't find a bad one!!
John, or others, is it worth topping up each battery with a 40 or 50A charger (both are onboard) or will the solar charging individual batteries be enough.

On another tangent, my fridge, Danfoss BD50, with the water pump, are only drawing 1.5A, even on start up, which doesn't seem high enough from what I've read. Would it draw less amps if it was low on gas???
At the moment, after it has been up & running for a while, it is runs for 6.5hrs straight & then is off for 18.5hrs & repeats exactly. Does this seem normal - I've never monitored it before when all was good but, from memory (which isn't that crash hot these days), I think it used to cycle more frequently. It might be where it is set at the moment tho - I've been wiggling/tweaking everything lately.

Thanks for all the help, there is a wealth of information here on Seabreeze without all the BS & arguing like on some other forums!!

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Lazzz said..

Trek said..
Its not necessarily faulty at all!

MPPT chargers need to find the point at which they get the most power out of a solar panel at a given time by varying the load.

The big criteria is are the batteries charged and staying charged.

I think this is the case.

I thought the fridge might have been playing up & drawing more current but after checking today it's not the fridge - or anything else drawing current.
With everything turned off I'm only drawing 13mA (radio etc) & with my Pi3, which runs 24/7, it only draws 0.7A.

After turning all but the Pi3 off on Saturday I went to the boat today & found the battery bank still at 12.5V - half charged instead of fully charged.

I took Jode5's advice & isolated the batteries & had only one hooked up to the system. The MPPT controller still did the same thing but the single battery was fully charged up to 14.2V in a few hours on solar alone on a rainy, cloudy day. I'll do the same for the other 5 each visit to the boat & hope they do the same & I don't find a bad one!!
John, or others, is it worth topping up each battery with a 40 or 50A charger (both are onboard) or will the solar charging individual batteries be enough.

On another tangent, my fridge, Danfoss BD50, with the water pump, are only drawing 1.5A, even on start up, which doesn't seem high enough from what I've read. Would it draw less amps if it was low on gas???
At the moment, after it has been up & running for a while, it is runs for 6.5hrs straight & then is off for 18.5hrs & repeats exactly. Does this seem normal - I've never monitored it before when all was good but, from memory (which isn't that crash hot these days), I think it used to cycle more frequently. It might be where it is set at the moment tho - I've been wiggling/tweaking everything lately.

Thanks for all the help, there is a wealth of information here on Seabreeze without all the BS & arguing like on some other forums!!

Hi Lazzz,
That's a good result. I would rather use the charger as it will give the batteries a good kick, but if that's a real problem use the solar. Maybe the batteries just all need an individual charge which is something you should do a couple of times a year or you could still find a faulty battery. Let's hope they all just need a good charge. Also what Trek said is also true and the regular may be ok and just doing its thing. The fact that it bought one battery up is a good sign.
John.

Quick update:
I took all the batteries home to charge them separately.

I bit the bullet & bought a new Ozcharge 9 stage battery charger - www.ozcharge.com.au/collections/12-volt-battery-chargers/products/12-volt-12-amp-pro-series-battery-charger-and-maintainer - great bit of gear & good insurance for the batteries!!

This charger has a setting to "rejuvinate" the batteries which I hit all 6 batteries with & it worked well. It also has an equalisation setting as well which I didn't need at this stage.

All batteries came up great & are back in the boat & staying fully charged with the fridge etc running 24/7.
The controller still goes back to 0 amps very briefly, to check, & then climbs back up to whatever the sun is supplying.

Thanks for your help :)

I have the exact same problem with the same esmart3 charge controller. I certainly do not think this is normal at all. I have 1000W panels on a 600Ah bank (150ah/12 x 4 - Series/parallel combo). You are wasting half of the energy as the controller dips down to 0A then back up on about a 50% duty cycle. Pulling my hair out with this!

My Chinese-cheapie Tracer MPPT does this zero thing occasionally. The first time I saw it got fussed and disconnected/reconnected it, and it went back to normal but now I ignore it. For over 6 years it has done a sterling job (no pun intended) of keeping the house battery charged.

Every now and one of the too-cheap-to-be-any-good eBay buys turns out to be a bargain, and this was one of those. Sort of makes up for all the other pos's.

Cheers, Graeme