Solar panels in series - what dc to dc charger? (1 Viewer)

[Martynovo]

Solar panels in series - what dc to dc charger?
Hello from a club newbee of 50 years motorhome experience . Latest vehicle is a hymer on 316cdi 2017. Original dealer installed 4 panel vision plus solar system in series with pwm charger total output 170w. Plus Vanbitz. The panels are glued on and cover all connections so there is no access to change to make them parallel. I see virtually all dc to dc chargers with solar MPPT(for lithium) have limited voltage input as low as 23v (CTEK, Renogy etc) and Im way above that but no idea of maximum as Im waiting for a good sunny day! Have I got to use a voltage limiter or buy a very expensive victron solar controller as well as dc to dc charger? Any ideas? Thanks. Martyn
I wish I had found this club 25 years ago........

 

[DBK]

You might have caused a bit of confusion by mentioning a DC to DC charger which is a term usually reserved for a different thing altogether, specifically a B2B or battery to battery charger.

What I think you mean is a solar controller and I'm sure one can be found to suit.

If you can post a photo of the panels, just one if they are all the same, we should be able to work out the voltage. Dimensions too if possible.

Alternatively, disconnect one wire from your existing PWM controller and around midday when the sun is trying to shine measure the voltage.

But the answer will still be Victron!

And welcome!

 

[Martynovo]

Thanks, I had read so much a bit of confusion and I thought the two terms were synominous. It is of course a B2B charger . The vision plus website is down at the moment but I know for my model it is 3 x40 watt including master panel and one 50 watt so I wait for the sun!

 

[autorouter]

The Victron MPPT range have input voltages from 75V up to hundreds of volts. The larger ones are used on house installations with strings of panels in series. The voltage is shown in the label. For example a SmartSolar 75/15 has a maximum input voltage of 75V and a maximum current output of 15A. I would guess that a 100/20 would be suitable, but better to measure the midday voltage and/or count the cells in the panel as DBK says.

The output of the solar controller is designed to be a proper battery charger, with 3-stage intelligent charging, and can be connected directly to the batteries.

 

[Lenny HB]

On a Motorhome it is better to have them in parallel although the brackets will be fixed with adhesive how are the panels fixed to the brackets?
Often pop riveted so easy to drill out the rivets.

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[Reallyretired]

I prefer panels in parallel, however 4 panels in series could give your solar regulator an input voltage of nearly 100v so you need a regulator that can accept that voltage. Probably a 30A output would be adequate if the panels are around 100w each as they will never produce their rated output.

 

[Martynovo]

Thanks every one for your thoughts. What a good idea Lenny, so I immediately climbed on the roof and found the mounting brackets are part of the panel itself so no go there. What I really wanted is the all in one solar controller, B2B charger and mains EHU charger but I read Victron dont do one, so having a Victron solar controller then a second unit will be very expensive. I must be one of the last Merc Hymers without its own B2B just the EBL 30 plus vanblitz battery manager. The existing PWM is not wired in to the ELB systems solar input, it feeds in via its own fuse block. A B2B it obviously needs a feed from starter battery. Can I just split the feed with a fuse thats already there for ELB which is easy or will I need dedicated feed because of overloading existing cable? Hymer at the October show said just use the existing on board charger and vanblitz manager and only replace the PWM with MPPT but that must be very inefficient. Sorry about so many questions. I am still waiting for the sun in a clear sky
Martyn

 

[Lenny HB]

. What I really wanted is the all in one solar controller, B2B charger and mains EHU charger but I read Victron dont do one,

Votronic do one but do you really want all your eggs in one basket, I wouldn't.

 

[Raul]

Yes votronic trio, expensive kit, good, but quite low voltage for the mppt, and requires your panels in parallel. I would fit best mppt for solar like a victron 100/30 or 150/35 for solar, a battery master for starter battery and a sterling B2B. Job done, and it’s reliable for years to come, not expensive in the long run, comparing to what’s the van’ worth.
I never understood ppl that spend tens of thousands on a van, then chip out on a 10 dollar useless solar controller, might as well leave the panels at home.

 

[autorouter]

A B2B it obviously needs a feed from starter battery. Can I just split the feed with a fuse thats already there for ELB which is easy or will I need dedicated feed because of overloading existing cable?

There are two wires from the starter battery to the EBL, a 20A fused one for the fridge element supply and a 50A fused one for the split charge relay supply. The 20A one goes in one of the front connectors, the 50A one goes to the rear connector which is a terminal block.

If you are fitting a B2B, ie a DC-DC charger that charges the leisure batteries from the starter battery/alternator, then it depends on the amps spec of the B2B, some are 30A, some are 60A or more.

A 30A B2B can use the existing 50A fused wire as the starter battery input. You can then send the output directly to the leisure battery (with a fuse of course). Since this bypasses the EBL internal shunt, the State Of Charge (SOC) percentage reading will no longer be valid

Alternatively you could feed the output into the unused starter battery input at the back of the EBL, and it will go through the split charge relay as before. There is no need to disable the split charge relay in this case. There's not much benefit doing it this way, but the SOC percentage reading will still be OK.

A 60A B2B will need a new wire from the starter batter and the leisure battery, and a suitable fuse too.

Other starter battery functions like the fridge element and the battery voltage reading go through the other (20A) wire, so will not be affected by this change.

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[Martynovo]

Thank you, Im reading all the advice but still puzzled. So if I go down the 30 amp B2B route which makes sense, as I will have only one 100 AH battery , then I end up with no connection of the starter battery to the EBL with no split charge relay using instead the B2B. So do I need the vanblitz battery manager at all.? I will need a more accurate state of charge meter as well. Using separate units the new MPPT solar controller which I may be forced to buy Victron is then virtually a swop?

 

[autorouter]

So if I go down the 30 amp B2B route which makes sense, as I will have only one 100 AH battery , then I end up with no connection of the starter battery to the EBL with no split charge relay using instead the B2B.

Yes, sort of. The 50A fused wire only connects to the split charge relay that is inside the EBL. So you can remove the 50A fuse and the split charge relay will be disabled. It will still click on and off, but with no input it will have no effect. Or if it is convenient you can disconnect the 50A wire from the back of the EBL and use that wire to feed the B2B input. That will also ensure the split charge relay doesn't do anything.

The other EBL functions like the fridge 12V element, the starter battery voltage sensing and the starter battery trickle-charging when on mains hookup will still work, through the other wire with the 20A fuse on it.

So do I need the vanblitz battery manager at all.?

If the solar controller is not a dual output type, then it won't trickle-charge the starter battery while parked up. You may need a battery maintainer like the VanBitz BatteryMaster to keep it topped up from solar. The starter battery will be trickle-charged from mains hookup and of course when the engine is running, so depending on your pattern of usage you may not need it.

Which solar controller is fitted at present? Are you 100% sure the panels are wired in series, it's not very common?

 

[Martynovo]

Yes, sort of. The 50A fused wire only connects to the split charge relay that is inside the EBL. So you can remove the 50A fuse and the split charge relay will be disabled. It will still click on and off, but with no input it will have no effect. Or if it is convenient you can disconnect the 50A wire from the back of the EBL and use that wire to feed the B2B input. That will also ensure the split charge relay doesn't do anything.

The other EBL functions like the fridge 12V element, the starter battery voltage sensing and the starter battery trickle-charging when on mains hookup will still work, through the other wire with the 20A fuse on it.

If the solar controller is not a dual output type, then it won't trickle-charge the starter battery while parked up. You may need a battery maintainer like the VanBitz BatteryMaster to keep it topped up from solar. The starter battery will be trickle-charged from mains hookup and of course when the engine is running, so depending on your pattern of usage you may not need it.

Which solar controller is fitted at present? Are you 100% sure the panels are wired in series, it's not very common?

Thanks again everyone, what an amazing group. I'm almost there now and ready when weather permits. As I have the VanBitz battery master then I might as well fit it. Originaly it bridged the three input wires to the EBL so do I wire it in on the input terminal (from starter battery) of the B2B and input terminal of EBL (leisure battery) effectively as it was before. Just doesnt seem correct as that gives a feed to the split charger as well, so it has to go on the to the B2B - one to common, one to input from starter and one to output for leisure but that bridges the B2B - hence my confusion. Or is the Manager more sophisticated than I thought and take care of that? I'll leave you in peace then!

 

[autorouter]

The split charge relay is simply a big relay that is on when the engine is running, and off when the engine stops. Originally, there is a 50A fused wire from the starter batter to one terminal, and a 50A fused wire from the leisure battery to the other terminal. When the engine is running, they are connected together, and the connection is broken when the engine stops. Those wires are fed via a heavy duty terminal block at the back of the EBL, because the terminals at the front are only good for about 15A.

The 50A Leisure battery wire is used for all kinds of functions as well as charging the leisure battery, so it's best to keep that as it is. The 50A Starter battery wire is only used for power for charging from the starter battery/alternator. A 30A B2B is low enough power to still use the existing wiring, so there are two possible ways to wire it in.

Both ways start off the same. Disconnect the 50A starter battery wire at the EBL end, and connect that wire to the B2B Starter battery input. The B2B negative can go to any negative point, for example the common negative at the back of the EBL.

Now you have a choice of how to connect the B2B leisure battery output. The preferred way is to connect it directly to the leisure battery through a new wire with a new fuse. Or you could connect it to the leisure battery terminal at the back of the EBL, if that's more convenient than running a new wire. The split charge relay is bypassed, it still clicks on and off but it doesn't do anything.

The other possibility is to connect the leisure battery output of the B2B to the starter battery input at the back of the EBL. What happens then is, when the engine is running, the split charge relay passes the output of the B2B through the split charge relay to the leisure battery. So the split charge relay is acting simply as a convenient way to connect the B2B output to the leisure battery. It's actually quite a convenient way to wire in a B2B.

Some people don't like the second method, because they say the contacts of the split charge relay can develop some resistance if it's a bit old, but the method works well enough in most cases.

The BatteryMaster wiring can stay the same for two of the connections - the leisure battery and the common negative. But the starter battery wire needs to be connected to the B2B starter battery input. That avoids the B2B blocking the BatteryMaster's access to the starter battery.

 

[Martynovo]

Thanks again, just what I needed. Out of interest I see you are A class hymer as I am. I went to the show thinking of changing but shocked by price, the fact everything I have is now extra on a basic vehicle, and what I had not expected was Im 3.5 tonnes but you can no longer have my spec and all extras under 3.5 tonnes and as Im well over 70 I let my heavy vehicle, minibus etc sections go and only have a up to 3.5 tonne licence but still tow. Hence upgrading old vehicle rather than change.

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[Lenny HB]

Thanks again, just what I needed. Out of interest I see you are A class hymer as I am. I went to the show thinking of changing but shocked by price, the fact everything I have is now extra on a basic vehicle, and what I had not expected was Im 3.5 tonnes but you can no longer have my spec and all extras under 3.5 tonnes and as Im well over 70 I let my heavy vehicle, minibus etc sections go and only have a up to 3.5 tonne licence but still tow. Hence upgrading old vehicle rather than change.

I think you would be very pushed to run your MLI at 3500 kg legally.
Have you weighed it fully laden for a trip?

 

[Martynovo]

I think you would be very pushed to run your MLI at 3500 kg legally.
Have you weighed it fully laden for a trip?

The family trips with trailer, sailing and cycling gear are now behind us but in those days we must have been over. I fitted rear air suspension at new and fabricated my own aluminium rear bar. I was always very careful about the amount of water and waste carried but now with only two of us I dont think its an issue and we do like the luxury of space to move around in. Even so I pack very carefully spreading the load between axles using the between floor storage areas. We used to get flashed regularly by the local French speed cameras on motorways and dual carriageways but it never came to anything. This summer touring Scandinavia in several countries all vehicles were limited to 50 which led to easy driving. Handling whatever the load even in the mountains has never been a problem with the MLI, a different world to Fiat. I gather the automatic box is one of the issues in new vehicles being so heavy. However driving a previous manual 316 CDI in Switzerland I was stopped and checked but we were well under. Ive often wondered about people that hang 2 electric bikes on the back. Ive never quite understood how on Mercedes when you buy a van you can have it plated at different levels without apparently any modification. Nothing changes the fact that in the "family days" I should have had it check weighed.

 

[dawsey]

Renogy 25/50A Solar/MPPT. All in one. Add a 50A ideal diode between battery terminal and the 30A fused lead feeding the existing 12V controller to retain all functions. Like other MPPT will take your series wired solar input.
Put an appropriate isolater switch on the feed from the panels and you can switch the B2B output from 25 to 50A when no sunshine.

 

[Clive Mott]

Firstly if you have glued on flexable panels then check they work. There is a high mortality of flexable panels after 5 years. You will need to measure each panels output with a multimeter. If you can do that and they are good then CONNECT THEM IN PARALLEL.

 

[autorouter]

Renogy 25/50A Solar/MPPT. All in one. Add a 50A ideal diode between battery terminal and the 30A fused lead feeding the existing 12V controller to retain all functions. Like other MPPT will take your series wired solar input.

As the OP says in post#1, the Renogy 25/50A solar/MPPT is limited to 25V input voltage on the solar input. Even two panels wired in series will exceed this, and the OP has four in series.

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[dawsey]

As the OP says in post#1, the Renogy 25/50A solar/MPPT is limited to 25V input voltage on the solar input. Even two panels wired in series will exceed this, and the OP has four in series.

It’s true. I stand humbly corrected. Note to self, check before stating stuff. OP will need to connect in parallel.

 

[autorouter]

as Im well over 70 I let my heavy vehicle, minibus etc sections go and only have a up to 3.5 tonne licence

You can get the over 3.5t entitlement back if you want, you have to apply using the D4 medical form and have a D4 medical. If you don't have a medical issue that stops you driving it should be possible to get back the full licence. I use D4Drivers, they specialise in driver medical certification so they know all the issues.

 

[Martynovo]

You can get the over 3.5t entitlement back if you want, you have to apply using the D4 medical form and have a D4 medical. If you don't have a medical issue that stops you driving it should be possible to get back the full licence. I use Driver's, they specialise in driver medical certification so they know all the issues.

Lenny, I've searched many times to see if that's possible, should have asked the Club.. thanks

 

[Stans Van]

Solar panels in series - what dc to dc charger?
Hello from a club newbee of 50 years motorhome experience . Latest vehicle is a hymer on 316cdi 2017. Original dealer installed 4 panel vision plus solar system in series with pwm charger total output 170w. Plus Vanbitz. The panels are glued on and cover all connections so there is no access to change to make them parallel. I see virtually all dc to dc chargers with solar MPPT(for lithium) have limited voltage input as low as 23v (CTEK, Renogy etc) and Im way above that but no idea of maximum as Im waiting for a good sunny day! Have I got to use a voltage limiter or buy a very expensive victron solar controller as well as dc to dc charger? Any ideas? Thanks. Martyn
I wish I had found this club 25 years ago........

Good afternoon. I would speak to Vanbitz .