What Voltage should my control panel be showing? (1 Viewer)

R

Robert Clark

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Hi Guys

Yesterday I decided to test to see how long it would take my solar panels to re-charge my batteries after use.

Got 320ah solar and 360ah gel batteries

At the beginning of the test (early morning) the MH control panel showed the battery voltatge at 13.1v
I ran my air conditioning for 1 hour
After turning off the A/C the battery voltage showed 12.7v
In the middle of the afternoon the battery voltage had only increased to 12.8v (it was a very cloudy day)
The charge indicator neon on my Victron solar controller MPPT 75/15 controller was solid yellow (not flashing) which shows that its on 'float charge'

I was expecting the reading to be higher, so I attached a multi meter to the output of the solar controller, which showed 13.3V

So I'm wondering why the output of the solar controller was higher than the voltage being picked up my the MH control panel?

Why the solar controller was only showing as 'float charge' when I'd been running the A/C for an hour?

Will the solar panels ever return the charge state to 13v, or will they charge to a lower level than the battery charger would, when connected to EHU?

Thanks
Robert
 

DBK

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I've got the same controller as you (but just the one! :)) and my battery voltage reads 13.6 when on float. The sun is shining at the moment and this is what it is showing with a charging current of around 0.1 amp.

Edit: Just checked again and it is showing 13.8 volts, same 0.1 amp charging current.
 
Last edited:
Feb 9, 2008
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I will have a stab at this! I suspect your system is fine and working as it should. When you ran your AC you would have been drawing power from both the solar power bank and Hab battery bank and I suspect little was taken from your batteries. When you place a load on your batteries they will not provide an accurate reading, they need to be at rest with no load on, for a few hours before you can accurately measure them and I suspect this is where the anomaly is coming from.

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Robert Clark

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I've got the same controller as you (but just the one! :)) and my battery voltage reads 13.6 when on float. The sun is shining at the moment and this is what it is showing with a charging current of around 0.1 amp.

Edit: Just checked again and it is showing 13.8 volts, same 0.1 amp charging current.
So after a day or so if sunshine I can expect to see my MH control panel reading 13v?
 
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Robert Clark

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I will have a stab at this! I suspect your system is fine and working as it should. When you ran your AC you would have been drawing power from both the solar power bank and Hab battery bank and I suspect little was taken from your batteries. When you place a load on your batteries they will not provide an accurate reading, they need to be at rest with no load on, for a few hours before you can accurately measure them and I suspect this is where the anomaly is coming from.
It was very cloudy so I'm not sure the panels could have coped with the load.

My suspicion is that there might be a fault between the solar controllers and the batteries. My logic being that voltage at the output of the solar controller does not prove that the batteries are even connected.
 

Jim

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A quick glance at voltage and its easy to think that your bank is charged. However I have a Victron Monitor and use the % to see the actual state of charge.

My three panel in morning sunshine and I'll have a reading of 13+ volts but check the percentage and I might be only 85% charged

ZVICBAM010702200.jpg

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Lenny HB

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As you have Gel batteries, as they charge the voltage should go up to 14.2 /14.4 volts then reduce to a maintance charge of 13.8 volts. To fully charge Gel batteries once the reach 14.2/14.4 volts they need to be held at that voltage for 8 hours. It not holding at the higher voltage for sevel hours your charger may not be set to Gel. I would check the voltages with a multimeter as CBE panels tend to read high (on the ones I've seen).

Got 320ah solar
Blimey how did you get 5,760 watts of solar on the roof.:)
 

Jim

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To fully charge Gel batteries once the reach 14.2/14.4 volts they need to be held at that voltage for 8 hours.

Thats the mistake I used to make. I'd see 13.4 or so on the panel and I'd tell people "My solar panels are fantastic, my Batteries were charged by 8am" The truth is as you say, just because they show that voltage they are not yet charged. My massive battery bank might be fully charged but only if the panels have kept it at that voltage all day :)
 
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Robert Clark

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A quick glance at voltage and its easy to think that your bank is charged. However I have a Victron Monitor and use the % to see the actual state of charge.

My three panel in morning sunshine and I'll have a reading of 13+ volts but check the percentage and I might be only 85% charged

ZVICBAM010702200.jpg
How / where is this connected to Jim

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Robert Clark

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As you have Gel batteries, as they charge the voltage should go up to 14.2 /14.4 volts then reduce to a maintance charge of 13.8 volts. To fully charge Gel batteries once the reach 14.2/14.4 volts they need to be held at that voltage for 8 hours. It not holding at the higher voltage for sevel hours your charger may not be set to Gel. I would check the voltages with a multimeter as CBE panels tend to read high (on the ones I've seen).


Blimey how did you get 5,760 watts of solar on the roof.:)
Hi Lenny
My concern though is that after a cloudy day the voltage hadn't increased - it was only showing as 12.8 on the MH control panel. As if the solar had not charged at all
 

Lenny HB

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Hi Lenny
My concern though is that after a cloudy day the voltage hadn't increased - it was only showing as 12.8 on the MH control panel. As if the solar had not charged at all
To answer your question you need to know how much power you have taken out of the batteries (how many amps for how long), the solar was probably just keeping up with your usage. On a cloudy day in the UK you are probably only getting 25% of your panels output about 5.5 amps.

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Robert Clark

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I think I've found the issue!!!!

My motorhome is pre wired with a cable from the ceiling to the battery (old battery position, as mine were moved to the garage)

There is a fuse where the cable attaches to the old battery connector
There are also two connectors near the ceiling, where the solar panels connect to the pre installed cable which leads to the battery.

I removed the fuse in the battery compartment and tested it - looks fine
I tested the voltage at one end of the fuse holder (the end nearest the battery) and it read 12v+
However the voltage at the other end of the fuse holder, leading from the solar panels read 0V

I then checked the voltage at the connectors which connect the solar panels to the pre wired solar cable - and it read 13+v at the solar side, but 0V at the battery side, which suggests that the pre installed cable leading from the ceiling, where the solar regulators are, to the battery compartment is faulty.

Would you agree?
 

Lenny HB

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I then checked the voltage at the connectors which connect the solar panels to the pre wired solar cable - and it read 13+v at the solar side, but 0V at the battery side, which suggests that the pre installed cable leading from the ceiling, where the solar regulators are, to the battery compartment is faulty.

Would you agree?
Common practice for dealers to by-pass the built in wiring if you had the panels installed by your supplying dealer god help you. My mate had his done by them, certainly rates as one of the biggest bodges I've ever seen.

Need to follow the wiring all the way through may be a red herring.
 

DBK

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I've just remembered, when we were away our solar stopped charging, fortunately so did the TV. Fortunate, because my MH manual told me which fuse to check for the TV which I found was blown. When I replaced it both the TV and the solar panel started working.

I hadn't realised the solar controller was connected to the batteries through a 10A fuse but it was - I had simply reused the existing connections when I fitted the Victron controller in place of the previous unit.

The point of this rambling account is before I replaced the fuse the controller was showing a steady yellow light, which I think is what you have. So a steady light may indicate there is no connection between the controller and your batteries.

As it was fitted by Eddie VB I am sure they would have installed it properly and there will be a fuse somewhere in the feed to the batteries. Either a standalone fuse or one of the connections in the fuse box.

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Jul 5, 2013
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How / where is this connected to Jim
Robert, I have the same controller. It measures net input or output (in Amps and volts) to or from the batteries and from whatever source at any one time and tots it all up to report the state of the batteries. It is connected directly to the battery bank and my display is above the hab door next to the crappy Hymer control panel. Easy enough to fit - the only difficult bit is routing it to where you want the display unit. The dealer fitted mine (including the difficult bit), but I had to re-fit it when I subsequently put in the inverter.

Pop over and look at it if you like
 
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Robert Clark

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I've just remembered, when we were away our solar stopped charging, fortunately so did the TV. Fortunate, because my MH manual told me which fuse to check for the TV which I found was blown. When I replaced it both the TV and the solar panel started working.

I hadn't realised the solar controller was connected to the batteries through a 10A fuse but it was - I had simply reused the existing connections when I fitted the Victron controller in place of the previous unit.

The point of this rambling account is before I replaced the fuse the controller was showing a steady yellow light, which I think is what you have. So a steady light may indicate there is no connection between the controller and your batteries.

As it was fitted by Eddie VB I am sure they would have installed it properly and there will be a fuse somewhere in the feed to the batteries. Either a standalone fuse or one of the connections in the fuse box.
Thanks for that
Like you I assumed that yellow solid meant batteries full
I've ordered a new cable and will run a new feed to the battery tomorrow
I'm not blaming Eddie for this as he connected to a cable supplied by Carthago.
I'd just like to prove my theory and start charging my batteries
Would seem strange that I've had solar for a year, but with no benefit !
 
2

2657

Deleted User
Thanks for that
Like you I assumed that yellow solid meant batteries full
I've ordered a new cable and will run a new feed to the battery tomorrow
I'm not blaming Eddie for this as he connected to a cable supplied by Carthago.
I'd just like to prove my theory and start charging my batteries
Would seem strange that I've had solar for a year, but with no benefit !

I know absolutely nothing about solar but following your recent blogs you seem to move on every day which i would assume recharges your batteries.

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Robert Clark

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I know absolutely nothing about solar but following your recent blogs you seem to move on every day which i would assume recharges your batteries.
That's exactly what's been happening
On our last trip, the batteries never went above 12.8v, unless we'd been driving, even though it had been a very sunny day
 

Lenny HB

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If Eddie installed it shouldn't be any problem with the wiring. Carthago use 6mm solar cable I find it hard to beleive there is a problem with it, as it is a double insulated heavy cable unless it has been chaffing against a sharp edge somewhere. Could it be a faulty crimped connector at one end or on the fuseholder?
 

Lenny HB

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Oct 18, 2007
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That's exactly what's been happening
On our last trip, the batteries never went above 12.8v, unless we'd been driving, even though it had been a very sunny day
So you have just fitted more solar panels because you didn't know your existing panels weren't working.:Grin::Grin::Grin:

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Robert Clark

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If Eddie installed it shouldn't be any problem with the wiring. Carthago use 6mm solar cable I find it hard to beleive there is a problem with it, as it is a double insulated heavy cable unless it has been chaffing against a sharp edge somewhere. Could it be a faulty crimped connector at one end or on the fuseholder?
That's a thought I'll go and check
 
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Robert Clark

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@Lenny HB
I checked both ends of the cable by cutting back a tiny piece of cable insulation
It's dead at the bottom end and live at the top end, suggesting that power from the panels is entering the cable, and that there is a break in the cable somewhere between the top and the bottom.
I can't expose much of the cable route as its in ducting behind the fridge and clamped to the inside wall

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Lenny HB

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@Lenny HB
I checked both ends of the cable by cutting back a tiny piece of cable insulation
It's dead at the bottom end and live at the top end, suggesting that power from the panels is entering the cable, and that there is a break in the cable somewhere between the top and the bottom.
I can't expose much of the cable route as its in ducting behind the fridge and clamped to the inside wall
Sounds like Carthago have trapped the cable somewhere and it's broken under vibration unless there is a join in the cable that has come apart.
 
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@Robert Clark
Assuming you prove your suspicions & the controller is not connected to the batteries, you need to consider the order in which you reconnect everything.

Your controller relies on having a feed from the battery before being connected to the panel so that it can work out whether it is connected to a 12 or 24V system. So you will need to disconnect the +ve feed from the panel, then make good the connection from the controller to the batteries & finally re-connect the panel +ve to the controller.

While checking fuses, remember that there is one in the controller itself.
 
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Robert Clark

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@Robert Clark
Assuming you prove your suspicions & the controller is not connected to the batteries, you need to consider the order in which you reconnect everything.

Your controller relies on having a feed from the battery before being connected to the panel so that it can work out whether it is connected to a 12 or 24V system. So you will need to disconnect the +ve feed from the panel, then make good the connection from the controller to the batteries & finally re-connect the panel +ve to the controller.

While checking fuses, remember that there is one in the controller itself.
Thanks for that
Will certainly do that
I'm assuming that the Controller fuse is ok as there is power in the first section of cable leaving it

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Sep 23, 2013
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I'm assuming that the Controller fuse is ok as there is power in the first section of cable leaving it
Good point.

It may also be the case that the controller is still well aware of what voltage system it is (supposed to be) connected to, especially if it is showing voltages in the 12-14V region on the output side. I'm not sure I'd want to take the risk though!
 

Lenny HB

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@Lenny HB
I checked both ends of the cable by cutting back a tiny piece of cable insulation
It's dead at the bottom end and live at the top end, suggesting that power from the panels is entering the cable, and that there is a break in the cable somewhere between the top and the bottom.
I can't expose much of the cable route as its in ducting behind the fridge and clamped to the inside wall
I thought you had 2 panels with separate feed to 2 separate controllers so you should be getting power from one panel unless there is a common negative cable.
 
Oct 30, 2010
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We have almost the same set up in almost the same van as @Robert Clark except we don't have such a large battery bank.
Our control panel shows 13.8 volts most of the time when the solar panels are doing their job.
However, we did have a similar problem when we first had the panels fitted by the dealer, before we picked the van up.
After a couple of days I didn't think the panels were charging and the led's on the solar regulator showed that to be the case.
When the dealer investigated they thought, like Robert, that the fault must be in the cable from the roof to the regulator which ran down behind the fridge.
A lengthy booking was made to investigate which might have meant removing the fridge but within half an hour it was sorted.
Apparently there was a connection right up at the front, in the locker beside the passenger seat in our LHD van, that had to be connected and 'hey presto' it has worked ever since.

All that waffle was to say, look under the cup holder at the RHS of the dash Robert.
Why there should be a solar connection there is a mystery to me but no doubt Carthago have a good reason.

Richard.

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