Adding new solar to Moho with existing Sargent unit

[iain26]

I am going to add a new 100-150w solar panel to my AutoTrail which has a factory fitted 100w panel with a Sargent controller,

Is it wise to add the new panel, a new controller and connect straight to the batteries and leave the existing arrangement as fitted,
OR disconnect the existing add the new controller sized to suit both panels?

Pros and cons please.

Iain

 

[tonka]

If you have the EC500 this is what Sargent advised...
Leave existing panel as is and set the control panel above door so that solar only charges engine battery.
New solar via new regulator and direct to leisure.
I never went ahead with it, i upgraded the 100w panel to a 120w as thats the max the Sargent unit is rated for. Suited my needs at the time.

Alternative could be to put the 2 panels together, into a dual regulator and take feeds to both leisure and engine batteries.

 

[Lenny HB]

The Sargent solar regulator is just a cheapo PWM unit thrown in the back of the charger/distribution unit. Best to ditch it and fit a decent MPPT regulator like a Votronic or Victron.

 

[iain26]

It seems ditching the Sargent unit would be best because it is the winter charging I am looking for and mttp seems to be much better for that.
Would we still be able to charge both leisure and van batteries (selectable or automatically) using the new MTTP controlller?

 

[Abacist]

VanBitz fitted separate Victron controllers for each of my solar panels. That would suit you best as well if you want the 100 watt panel charging the Cab battery and your new solar panel charging the Hab batteries. In my humble opinion - others may have other advice! This also means that if one panel is in shade the other will still produce full output via its own controller.

In this way both are getting a charge although the Cab battery will also get a charge when being driven and if full, hopefully an overflow to the Hab batteries if you have a split charge relay.

Some might say you want all the solar to your Hab batteries which is where the current draw will be when the vans in use, with an overflow back to the Cab battery to stop it going flat in the winter.

Make sure that the solar is adequate in the winter as the sun, when out, is very low and the panels won't create much of a charge in the UK if flat on the roof.

I keep mine on a hookup during the winter to avoid the risk of the solar being inadequate.

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[Lenny HB]

It seems ditching the Sargent unit would be best because it is the winter charging I am looking for and mttp seems to be much better for that.
Would we still be able to charge both leisure and van batteries (selectable or automatically) using the new MTTP controlller?

The Votronic Duo has a seperate 1 amp output to keep the starter battery topped up.

 

[autorouter]

Usually the cab battery doesn't need very much charging. You arrive at the pitch with the battery fully charged from a long drive, and don't use it until it's time to start the engine when you move on. A small charging current to power alarms, etc is all that is required. If you dedicate 100 watts of solar to that job, you're wasting nearly all that power. 20 watts is enough.

The best solution is what @LennyHB said. Send all the panels through a new Duo controller, and connect the cab battery to the Battery2 output.

You need to find out the voltage and amps of your existing 100 watt panel. To connect another panel in parallel, as is usually done, they need to be the same voltage.

 

[iain26]

Thanks for the suggestions. It looks like we ditch the Sargent controller and get a Victron Duo as we do need a charge to the vehicle battery as it drains a bit and that appears to be the best way.
I had read that wiring in Series was better for low light conditions so what would be the advantages of going in parallel?
How would I find the existing panel rating? There seems to be no labelling on the top and I don’t really want to take it off to see if there is a label underneath.

 

[autorouter]

How would I find the existing panel rating? There seems to be no labelling on the top and I don’t really want to take it off to see if there is a label underneath.

Not so easy, do you have any clue as to the brand name? Is it a 9 x 4 solar cell layout? That's quite popular for 100W panels. Can you get your phone underneath and take a picture of the label? Can you get a voltmeter on the panel wires going into the controller?

 

[Lenny HB]

I had read that wiring in Series was better for low light conditions so what would be the advantages of going in parallel?

Series is slightly more efficient but get some shade on one panel you lose the output from both.
Pararellel is the best option for a Motohome.

How would I find the existing panel rating? There seems to be no labelling on the top and I don’t really want to take it off to see if there is a label underneath.

Measure it, a 100 watt Monocrystalline panel will be something like 1200 x 540 mm or 920 x 670 mm approx 0.63 m3 Polycrystalline panels are about 10% bigger. Monocrystalline panel are the most efficient and the type to go for.

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[autorouter]

I had read that wiring in Series was better for low light conditions so what would be the advantages of going in parallel?

I think that's more true for PWM controllers. MPPT controllers are better for low light conditions. The advantage of parallel is that shade on one panel doesn't stop the unshaded panel from producing. In series, a bit of shade stops the whole string. Series/parallel decisions are more important for house rooftop arrays with a dozen panels or more, with perhaps long wire lengths to the controller. Usually on a MH with two or three panels they are wired in parallel.

By the way, don't get mixed up by the three companies Victron, Votronic and Voltronic.

 

[PhilandMena]

I am going to add a new 100-150w solar panel to my AutoTrail which has a factory fitted 100w panel with a Sargent controller,

Is it wise to add the new panel, a new controller and connect straight to the batteries and leave the existing arrangement as fitted,
OR disconnect the existing add the new controller sized to suit both panels?

Pros and cons please.

Iain

The Sargent solar regulator is rated at 10 Amps. I have dome exactly what your proposing (1 x 120 into Sargent regulator & 1 x 125 into separate regulator and connected directly to hab batteries) and it works a treat with both sets of batteries being maintained and when needed the hab batteries will be charged by both panels at the same time. The Sargent control panel also shows what is going into and out of the batteries.

 

[PhilandMena]

The Sargent solar regulator is just a cheapo PWM unit thrown in the back of the charger/distribution unit. Best to ditch it and fit a decent MPPT regulator like a Votronic or Victron.

Agreed, but it works and is connected to the overhead door display so user's can see what is happening.

 

[iain26]

Series is slightly more efficient but get some shade on one panel you lose the output from both.
Pararellel is the best option for a Motohome.


Measure it, a 100 watt Monocrystalline panel will be something like 1200 x 540 mm or 920 x 670 mm approx 0.63 m3 Polycrystalline panels are about 10% bigger. Monocrystalline panel are the most efficient and the type to go for.

Just been on the roof and it is 1200x550 with 9x4 cells so looks to be Monocrystalline.
There is what looks like a serial no sticker which shows GCQ100M so I assume that is right.

 

[PhilandMena]

This is the current Sargent Regulator. Rated to 150 W

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[iain26]

Agreed, but it works and is connected to the overhead door display so user's can see what is happening.

Yes, I like the display but I am getting so little out of it it is hardly worth having. Currently in Spain, in the sun and have seen 2.5amp from it just once in the last month and that was just for a few minutes. Shaded at the moment and getting 0.1amp according to the panel.

 

[PhilandMena]

Yes, I like the display but I am getting so little out of it it is hardly worth having. Currently in Spain, in the sun and have seen 2.5amp from it just once in the last month and that was just for a few minutes. Shaded at the moment and getting 0.1amp according to the panel.

Understood. I'm somewhat surprised you only get up 2.5 Amps. I get up to 5 Amps with my 125 going through the Sargent regulator and this automatically switches to maintain the cab battery with the other panel I get above 8 Amps (combined) but not often required as the batteries are almost full all the time and only require a few amps to top up. Make sure both batteries are catered for if you bypass the Sargent system.

 

[iain26]

Understood. I'm somewhat surprised you only get up 2.5 Amps. I get up to 5 Amps with my 125 going through the Sargent regulator and this automatically switches to maintain the cab battery with the other panel I get above 8 Amps (combined) but not often required as the batteries are almost full all the time and only require a few amps to top up. Make sure both batteries are catered for if you bypass the Sargent system.

I can see we seem to have issues with our existing setup so are more inclined to change the whole lot now. We have never seen more than 2.5amps, even in summer so your 5 amps does sound good.
Noted we need to ensure provision for both sets of batteries thanks.

 

[autorouter]

Just been on the roof and it is 1200x550 with 9x4 cells so looks to be Monocrystalline.
There is what looks like a serial no sticker which shows GCQ100M so I assume that is right.

It will be similar to this one then.

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At max power it's 19.3V, 5.18 amps, and open circuit voltage is 22.9V. You have loads of choice for panels to parallel up with that - just keep the voltage about the same.

 

[PhilandMena]

I can see we seem to have issues with our existing setup so are more inclined to change the whole lot now. We have never seen more than 2.5amps, even in summer so your 5 amps does sound good.
Noted we need to ensure provision for both sets of batteries thanks.

Do it once and do it right! Put a shed load of solar up there !

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[Lenny HB]

Just looked at the Sargent link autorouter put up, looked at their connecting leads for a solar panel, what a joke way undersize. They don't give a size but look like 1 mm sq or 1.5 at the most.

If that's what yours are wired with I would run new cables from the roof at least 4 mm sq.

 

[Pete5996]

I'll post this here as I'm basically in the same situation as the OP, with a 100W panel feeding my EC325 charger. I have two Varta 90Ah hab batteries and a compressor fridge, which has performed excellently so far. Three or four days in partial shade at the French GP last year tested the ability of the panel to keep up, although even then it kept the batteries above 11.5V but it's time to add to the system.

I'm looking to add a 150W panel in parallel with the existing panel, giving me 250W. Both panels are mono, with a Vmp of 18V. The max current (Imp) of the 100w panel is 5.56A and that of the 150W panel 8.29A.

I'll be bypassing the EC325 solar controller and intend fitting a Votronic 1715 Duo 250 wired direct to the hab batteries, with a separate supply to the cab battery from the Votronic. I have a couple of questions about the installation, please.

1) Is the Duo 250 adequate for the 250W of panels? I have no plans to extend the solar any further.

2) In the installation manual for the Duo 250 the circuit diagram has the comment 'Install the solar controller near the main battery!' How near is near? I have two options for mounting the Duo 250. In an overhead locker, which will give a panels to controller distance of c. 1.5m and a controller to hab batteries distance of c. 3m. Alternatively, I can mount it in the floor locker above the battery bay, which will give a panels to controller distance of c. 3.7m and controller to batteries distance of c. 1m. Would either be satisfactory?

3) Cable sizing. Each panel has 4mm2 90cm tails to MC-4 connectors. I was planning use 4mm2 throughout but post #27 in this thread mentions that 4mm2 cable is too thick for the Votronic input terminals. If that is the case, what's best to do? Given the cable lengths involved would 2.5mm2 be adequate?

TIA

 

[PhilandMena]

I'm not competent enough to answer all the questions you raise and would have thought the Votronic manual should answer some of your questions.
There is however, one thing that leaps out to me and that is your battery voltage ? You say it's kept above 11.5 V but not by how much. 12.0 V is a significantly discharged battery and allowing your batteries to fall to or below this level will have a significant impact on your battery capacity which you may not notice until a little further down the line. Fitting a second S.P. will be a great help in preventing this deep discharge and you may want to consider adding more than 250 Watts of S.P. I have 1x125W and 1x120W and not convinced this would run my fridge as there would be quite a drain on my batteries during the night. (My AES fridge from new, has been wired to run off the cab battery when the 12 V mode is selected and the engine is not running ???). Anyway, the Voltronic gear is the best there is and I wish you well with your installation.

 

[Pete5996]

Thanks for your reply. The 11.5V was a bit of an extreme figure, noticed one morning after about 3 days on site, before the sun got to work. Normally they don't drop below 12.6V in daily usage and typical figures in store in the garden are around 13V for the hab and 12.8V for the cab. The fridge draws a max of about 4A when running, which is probably for less than half its working hours, even in warm weather.

Edit: Just had another look at the manual and tucked away on the diagram is the figure of 2m max for the controller to battery distance so that's answered one question - it'll be going in the floor locker

 

[autorouter]

In your case I wouldn't worry too much about the differences in the distances. This whole idea originated from large array installs, where the panel string voltage is often well over 100V. In that case it makes sense to have the longest wires between the panel and controller, because the amps on the battery side is many times higher than on the panel side. Cable power losses depend on the amps rather than the volts.

In your setup, the panel voltage is 18V and the battery charging voltage is about 14V, so there is very little difference.

The 250 watts of panel is about at the limit of what the controller can handle. If the power ever exceeds 250W, the excess will simply be wasted, no damage will be caused. I guess you could live with a problem like that.

I'd be surprised if the 4mm2 wire won't fit in the terminal. For a professional job, you could use bootlace ferrules. Either plain or insulated. You crimp them on the wire end, and it gathers all the strands together, squeezes them to minimise the size, and holds all the strands connected to the screw terminal.

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[Pete5996]

In your case I wouldn't worry too much about the differences in the distances. This whole idea originated from large array installs, where the panel string voltage is often well over 100V. In that case it makes sense to have the longest wires between the panel and controller, because the amps on the battery side is many times higher than on the panel side. Cable power losses depend on the amps rather than the volts.

In your setup, the panel voltage is 18V and the battery charging voltage is about 14V, so there is very little difference.

The 250 watts of panel is about at the limit of what the controller can handle. If the power ever exceeds 250W, the excess will simply be wasted, no damage will be caused. I guess you could live with a problem like that.

I'd be surprised if the 4mm2 wire won't fit in the terminal. For a professional job, you could use bootlace ferrules. Either plain or insulated. You crimp them on the wire end, and it gathers all the strands together, squeezes them to minimise the size, and holds all the strands connected to the screw terminal.
View attachment 355647View attachment 355648

Thanks for that info. I'd certainly prefer to have the controller in the upper locker as it will be a lot easier to see and I wouldn't have the faff of lifting seat cushions every time I want to check it.

I too would be surprised about the terminal, as the manual clearly states that the required cable cross-sections for panel and battery for the Duo 250 are 4-6mm! I like the look of the bootlace ferrules but couldn't justify buying a crimping tool just for the sake of four connections. I've enough 'once in a blue moon' tools in the garage as it is....

Perhaps someone with a Votronic (Lenny HB ?) is able to confirm that the terminals will accommodate a 4mm cable?

 

[Lenny HB]

Perhaps someone with a Votronic (@Lenny HB ?) is able to confirm that the terminals will accommodate a 4mm cable?

6mm cable no problem.
Always best to mount the Regulator as close to the battery as possible. Why do you want to see it, I can't see mine no need to.

 

[Pete5996]

6mm cable no problem.
Always best to mount the Regulator as close to the battery as possible. Why do you want to see it, I can't see mine no need to.

Thanks for the confirmation about the terminals. If I don't need to see the panel, the floor locker will do

 

[Lenny HB]

If you are using the AES output I would advise fitting a mains power relay to switch the signal otherwise you will find the fridge will switch to 12 v when on EHU (stupid Dometic firmware).

 

[Pete5996]

If you are using the AES output I would advise fitting a mains power relay to switch the signal otherwise you will find the fridge will switch to 12 v when on EHU (stupid Dometic firmware).

I binned my Dometic 3-way fridge last year after numerous frustrations and haven't looked back since, so the AES won't be used. Can you confirm that 4mm2 cable will be right for supply both sides of the controller?

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