Strange happenings with my solar setup?

gypo

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I ve got 2x 100w panels and 2x110ah batteries.
All has been well until recently on a moderately sunny day I see on my controller I get 20v coming in from the panels until recently, I've noticed now that as soon as I put the load switch on at the controller unit the solar input reduces to 15v-16.5v?
If I disconnect the panels from the unit and reconnect them it goes back up to 20v?
I've tested each panel separately on the. multi meter and both show 20v
Anyone have any ideas what it could be?
Thanks
G
 
My Solar panel regulator allows the output from the panels to go direct to the batteries after being regulated by the regulator, there is a separate terminal on the regulator for LOAD, and this can be time varied, this load facility is to run something DIRECT from the solar panels and is not wired in, but a red light shows on the regulator when the selected time slot is reached showing that power is available at the terminals. clear as mud I know but that is how it is,? So if this was connected to something the read out would obviously show a voltage drop as the juice would be shared elsewhere, so what have you got connected to LOAD?
 
I've got a relay that controls my solar water heater, so at the load the voltage out is minimal, the relay kicks in the heavy stuff at the batteries, basically the load out goes to a relay is turned on/off when the voltage is between 12.6v and 14.4v at the battery.
All the relay does is kick in the load that is connected direct to the batteries, the load is a 12v water heater element moded into my truma water heate.
This was all working fine up until a couple of days ago?
G
 
gypo said:
I ve got 2x 100w panels and 2x110ah batteries.
All has been well until recently on a moderately sunny day I see on my controller I get 20v coming in from the panels until recently, I've noticed now that as soon as I put the load switch on at the controller unit the solar input reduces to 15v-16.5v?
If I disconnect the panels from the unit and reconnect them it goes back up to 20v?
I've tested each panel separately on the. multi meter and both show 20v
Anyone have any ideas what it could be?
Thanks
G
Click to expand...

All dc batteries / sources will show an open circuit voltage that is higher when there is no load and lower when there is a load.

Looks like your situation is initial voltage=high with no load and when the charge controller kicks in the voltage is reduced as the batteries draw their charging current.

Open circuit = max voltage, zero current draw.
Load connected = some of the voltage is converted to current plus some minor loss from the inefficiencies of electrical gear which converts some of the input voltage to heat.

James
 
Sorry if this sounds thick:)
The voltage drop is showing at the panels in so instead of the panels showing they are producing 20v as they should be at the moment, btw we are in the south of France atm they are only showing 15-17v.
If I disconnect the wire at the controller for the panels in then reconnect and don't put the load on they show 20v
Cheers
G
 
gypo said:
Sorry if this sounds thick:)
The voltage drop is showing at the panels in so instead of the panels showing they are producing 20v as they should be at the moment, btw we are in the south of France atm they are only showing 15-17v.
If I disconnect the wire at the controller for the panels in then reconnect and don't put the load on they show 20v
Cheers
G
Click to expand...

Let me try putting it another way.

"If I disconnect the wire at the controller for the panels in then reconnect and don't put the load on they show 20v"
This is an open circuit voltage (open circuit is no load) of 15-17v. This itself will vary up and down with the amount of light falling onto the panels. eg at night there should be zero to low voltage and in bright sunlight you see the maximum panel voltage.

The charge controller is the first load that the panels will see, followed by the main load of the battery charge current.

Unless I am missing something, the system seems to be working as it should.

What is your concern ? are the batteries charging OK or not ?

James
 
They seem to be charging ok, what in trying to say is that if the panels are getting enough sun that at the display they show they are producing 20v of power and my batteries are sitting at let's say 14v. When I put the load on shouldn't they still be producing 20v of power and the batteries?
They used to up until recently if the load is pulling let's say 13v( the 12v water heater element) and the panels are producing 20v then it should hold its own, it used to up until recently
Thanks
G
 
gypo said:
They seem to be charging ok, what in trying to say is that if the panels are getting enough sun that at the display they show they are producing 20v of power and my batteries are sitting at let's say 14v. When I put the load on shouldn't they still be producing 20v of power and the batteries?
They used to up until recently if the load is pulling let's say 13v( the 12v water heater element) and the panels are producing 20v then it should hold its own, it used to up until recently
Thanks
G
Click to expand...
Are you seeing an issue such as flat batteries or poor charging performance or is it that you are seeing values (volts and amps) that you don't understand ?

Have you looked at the water heater element to see if it is calcified.
Do the batteries charge up.

Most solar charge controllers have a second set of output terminals that switch in once the batteries are fully charged.
So the primary output charges the battery and once they are charged the controller switches to the second set of terminals.
Some installations use the second set of terminals to heat water, others use it to charge another battery.

The whole system is changing all of the time.
The output voltage from the panels varies up/down depending on the light levels.
The output current from the controller will vary up and down depending upon the load.
A depleted battery will draw maximum current which goes down as the battery becomes charged.
When the second set of terminals kick in (on the charge controller) the current will again vary depending upon the temperature of the water (if it used on a water heater). Colder water=max current.

"20v of power and my batteries are sitting at let's say 14v"
That looks like max voltage at open circuit, that is to say the batteries are fully charged and there is no charging current (no load) therefore the voltage is no load/open circuit.

I think the confusion might be your understanding of "putting a load on"
Electical fittings, lights and appliances are not a load that the controller sees, these are a load that the battery sees.
The panels see the controller as their load, the controller sees the batteries (or aux terminals) as it's load and the batteries see the consumer appliances as their load.

They are all chained together and their relationship is dynamic - the values will always go up/down depending on the factors previously mentioned.

Still seems that the system is operating correctly if the batteries are charging normally.

James
 
Thanks James, you obviously now more than I do about it:)
But to sum up for me two weeks ago Eilat wild camping in Wales my panels were showing that they were producing 20v (in) and I could put the water heater on and as long as I had no cloud cover the panels stayed at 20v and the load was pulling a max of 14ish volts, this meant that at no time did the batteries drop below 12.6v and knock the circuit off.
Now in full south of France sun shine soon as I put the water heater on the panels show they are only producing 15-17v and the batteries can't hold there own before it drops below 12.6v and knocks its self off.
Sorry if I'm coming over a bit thick :)
Thanks
G
 
gypo said:
Thanks James, you obviously now more than I do about it:)
But to sum up for me two weeks ago Eilat wild camping in Wales my panels were showing that they were producing 20v (in) and I could put the water heater on and as long as I had no cloud cover the panels stayed at 20v and the load was pulling a max of 14ish volts, this meant that at no time did the batteries drop below 12.6v and knock the circuit off.
Now in full south of France sun shine soon as I put the water heater on the panels show they are only producing 15-17v and the batteries can't hold there own before it drops below 12.6v and knocks its self off.
Sorry if I'm coming over a bit thick :)
Thanks
G
Click to expand...

Sounds like a fault has occurred, IF this is not what you were seeing previously.

What is the water heater connected to ?
Is it connected directly to the battery or is it connected to the terminals of the charge controller?
If the water heater is taken out of the picture (switched off or disconnected) do the batteries charge as per normal?

From what you have said, the charge controller (CC) is not managing to keep the batteries charged when the water heater is in use.
Looks like the water heater is connected directly to the batteries.
If so, it's looking like the water heater element or it's thermostat is faulty.

Rather not try to do problem determination over the phone.

James
 
The water heater is connected directly to the batteries, the relay is connected to the load out on the solar charge controller, the charge controller switches the load on at the batteries, so the 12v element is connected direct to the batteries controlled by the relay. If I don't put the heater on then the input at the panels (not the battery reading) shows 20v.
I haven't tried disconnecting the relay from the load yet and then switching on then switching on the load to see if it still drops, I'll try that tomrw.
Something is not right tho and can't work out why the load would affect the solar input.
I hope this this makes sense?
Surely the input is the input and if the sun is producing 20v then putting a load on the batteries is not going to change the amount of input from the sun?
Thanks
G
 
gypo said:
The water heater is connected directly to the batteries, the relay is connected to the load out on the solar charge controller, the charge controller switches the load on at the batteries, so the 12v element is connected direct to the batteries controlled by the relay. If I don't put the heater on then the input at the panels (not the battery reading) shows 20v.
I haven't tried disconnecting the relay from the load yet and then switching on then switching on the load to see if it still drops, I'll try that tomrw.
Something is not right tho and can't work out why the load would affect the solar input.
I hope this this makes sense?
Surely the input is the input and if the sun is producing 20v then putting a load on the batteries is not going to change the amount of input from the sun?
Thanks
G
Click to expand...

The 20v is an open circuit voltage. If it stays at 20v and the batteries are not charging, then there is a failure somewhere.
(Incidentally, 20v is your system max value, my old system produced 36v)
It means that a relay is staying open and not connecting a load ( a connected load would drop the voltage to your 15-17v).

2 possible relays -
A) is inside the charge controller or
B) the water heater switching relay.
This results in the batteries not getting any charge current and the batteries lose voltage as the consumer loads depletes them.
Consumer load is whatever you are running off the battery.

A new charge controller for a basic system is cheap enough to replace and/or keep for a spare.

James
 
Thanks James,
I've got the tracer charge control unit, it was about £150 so not cheap.
I'll try a few more tests when we got home before I go buying another.
Thank for your help
G
 
gypo said:
Thanks James,
I've got the tracer charge control unit, it was about £150 so not cheap.
I'll try a few more tests when we got home before I go buying another.
Thank for your help
G
Click to expand...

tracerMPPT.jpg

Looks like your system has a design flaw, insomuch as you appear to have a 12v water heating element connected directly to the batteries.

In a solar system, the charge controller has a main function of charging batteries.
Once the batteries are charged the controller switches it's output to the auxiliary terminals - The tracker CC calls this pair of terminals LOAD (see 2 above). This simply provides excess or spare current to the LOAD terminals once the main batteries are fully charged.

The LOAD terminals are usually connected to another battery, could be the engine battery. Some folks connect this to a heating element inside the water tank.
In caravans and motorhomes, water heating is usually LPG and/or 220v.(the 12v supply is for the control circuit board)

If your water tank has a 12v heating element (possibly a 300w unit) This will deplete your batteries fast if you connect it directly to the batteries. Unless your solar panels are 300w plus, then the heater element will deplete the batteries faster than the CC can charge them up.

As you have 200w (giving you varying outputs of 0-200w depending on light levels) you need to ensure that you have a max of 150w heating element.

Using the water heater at any time of darkness or lower than maximum sunlight will simply draw from the battery in the configuration that you seem to have.

I'm not sure that your design/installation is correct.

James
 
hairydog said:
That's not how any of the ones I've seen are meant to work. The load circuit is simply a software-controlled output. The power from the load terminals comes from the battery, not from the panel.

You can choose to have the load switch on when the sun stops shining (for a street light, for example) or to come on when the sun is shining (for a cooling fan, for example). You can have it set to switch the load off if the battery voltage falls below a set amount, such as 11.2v, to protect it from over-discharge.

I can't see how you could set it to switch on when the battery was fully charged, becasue as soon as it went on, the battery would no longer be fully charged.

If your controller could power the load from the panel, not the battery, it would be the first I've heard of with this ability, and I'm not sure it would be sensible. The voltage would be rather unpredictable.
Click to expand...

"The load circuit is simply a software-controlled output."
Exactly, the charge controller switches from charging the battery to directing the current TO the load terminals, it works in a similar way to a split-charge relay.

"The power from the load terminals comes from the battery, not from the panel."
You directly contradict yourself in one sentence - the LOAD terminals are an OUTPUT - which outputs the solar voltage to an alternative load.
Click on the picture that I provided - its clearly shows what the LOAD terminals do.

The rest of your post is based upon incorrect understanding of what the load terminals actually do.

In your scenario, the lights and appliances would all go out when the controller sensed that the batteries needed a charge.

In all mobile installations that I have seen, the vehicle electrical devices (lights, fans, 12v sockets etc) are all supplied by a 12v fuse board.
The fuse board is connected directly to the leisure batteries.
The leisure batteries can have multiple charging methods,
a) from the engine alternator,
b) from a genny
c) from a solar panel(s)
or whatever.
Its not unusual for a motorhome to have multiple charging methods, connected simultaneously. eg the engine running and a solar panel, both delivering charging current as needed and both having a capability to reduce and then cut off the charging current, depending upon the charge state.

The solar charge controller offers an alternative pair of terminals that can be used to feed non essential loads such as a water heater, another battery, in the case of a water heater, this solar power is no good as the only source of current, it is meant to pre-heat the tank as a supplement to the usual heating method (on a van its usually LPG).

Solar charging goes directly from the charge controller to the leisure batteries.

When the batteries are fully charged, the solar panels output is then available for other uses, the original question suggests that it is used to heat water, although I am still unclear as to how it is wired up. The present wiring configuration seems to be a flawed design

Peace

James
 
Last edited by a moderator:
hairydog said:
I very much doubt that you are correct. I've seen dozens of these things and never seen one that works the way you describe.

The output is simply power taken from the battery, switched on or off by the controller. Your description is clearly nonsensical for a system that can used to switch on street lights when it gets dark. There would be no panel output to power them.

The wiring diagram does NOT show that the output is powered from the panel. Admittedly it doesn't say that it isn't either, but I can assure you that you are misreading what is describes.

I think you started out with a misunderstanding and have misread the docs to "confirm" your incorrect view. But I'm not prepared to get into an argument with you about it. Perhaps the makers specially made a unique design of solar controller and sold it to you as a one-off.
Click to expand...

I guess that we agree to disagree

James
 
I'm using mine as a dump load.
Basically the load out of the charge controller is set to be on if the voltage is between 14.4v and if it drops below 12.6v the load switches off until the batteries recharge to 14.v again and so on.
All the load out does is switch a relay on so the direct current is then taken from the batteries.
When it was first installed and I had 20v showing coming in at the panels it would hold its own and heat the water. Then in approx 50mins the thermostat on the boiler would kick it off regardless of the voltage. Now as soon as I put the load on( bear in mind I'm in the south of France at the mo) the voltage "COMING IN" at the panels drops to approx 15-17v.
As said before this did t happen a few weeks ago back in sunny Wales?
G
 
I'm using mine as a dump load.
Basically the load out of the charge controller is set to be on if the voltage is between 14.4v and if it drops below 12.6v the load switches off until the batteries recharge to 14.v again and so on.
All the load out does is switch a relay on so the direct current is then taken from the batteries.
When it was first installed and I had 20v showing coming in at the panels it would hold its own and heat the water. Then in approx 50mins the thermostat on the boiler would kick it off regardless of the voltage. Now as soon as I put the load on( bear in mind I'm in the south of France at the mo) the voltage "COMING IN" at the panels drops to approx 15-17v.
As said before this did t happen a few weeks ago back in sunny Wales?
G
 
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