How to wire solar panels?

[Aeolus]

Based on various discussions on this forum, I've almost decided to buy a Victron 75/10 MPPT controller and two Lensun 20W solar panels.

I have 2 x 110Ah batteries for domestics and a single 70Ah battery for the engine, these can be charged by mains or by alternator via a VSR. I also have a Victron 602S battery monitor installed that mainly monitors the domestic bank but also reports voltage on the engine battery. I don't need the solar panels to charge the engine battery - only the domestic bank.

The boat is on a swinging mooring in Chichester Harbour and spends most of the time on an east-to-west or west-to east axis.

I'm thinking of having one solar panel on each side of the boat, either side-by-side almost horizontally on the cabin roof (each slightly angled towards the respective side of the boat) in which case the sun-side panel may catch some shade from the shrouds and the other panel will catch quite a lot of shade from the boom, mast and shrouds, or mounted vertically on the outside of the guard-wires in which case the sun-facing panel will be totally unshaded but the other one will be entirely in the shade. Either way, one panel will get much more sun light than the other.

My questions:

1) Should I wire the panels in parallel or in series?
2) Should I connect the output from the MPPT controller directly to the batteries?
3) Can the battery monitor report on the charge going into the battery and do I need to wire things differently to enable this?
4) Do I need to connect anything to the 'Load' output from the controller or is that not necessary?

I apologise for the depths of ignorance probably demonstrated by my questions.

Thanks

 

[RichardS]

Based on various discussions on this forum, I've almost decided to buy a Victron 75/10 MPPT controller and two Lensun 20W solar panels.

I have 2 x 110Ah batteries for domestics and a single 70Ah battery for the engine, these can be charged by mains or by alternator via a VSR. I also have a Victron 602S battery monitor installed that mainly monitors the domestic bank but also reports voltage on the engine battery. I don't need the solar panels to charge the engine battery - only the domestic bank.

The boat is on a swinging mooring in Chichester Harbour and spends most of the time on an east-to-west or west-to east axis.

I'm thinking of having one solar panel on each side of the boat, either side-by-side almost horizontally on the cabin roof (each slightly angled towards the respective side of the boat) in which case the sun-side panel may catch some shade from the shrouds and the other panel will catch quite a lot of shade from the boom, mast and shrouds, or mounted vertically on the outside of the guard-wires in which case the sun-facing panel will be totally unshaded but the other one will be entirely in the shade. Either way, one panel will get much more sun light than the other.

My questions:

1) Should I wire the panels in parallel or in series?
2) Should I connect the output from the MPPT controller directly to the batteries?
3) Can the battery monitor report on the charge going into the battery and do I need to wire things differently to enable this?
4) Do I need to connect anything to the 'Load' output from the controller or is that not necessary?

I apologise for the depths of ignorance probably demonstrated by my questions.

Thanks

Identical panels so probably best in series.

Connect to battery or busbars on battery side of any main switch but make sure good cabling to battery.

Don't know about monitor.

No need to use load connector.

Richard

 

[VicS]

Based on various discussions on this forum, I've almost decided to buy a Victron 75/10 MPPT controller and two Lensun 20W solar panels.



My questions:

1) Should I wire the panels in parallel or in series?
2) Should I connect the output from the MPPT controller directly to the batteries?
3) Can the battery monitor report on the charge going into the battery and do I need to wire things differently to enable this?
4) Do I need to connect anything to the 'Load' output from the controller or is that not necessary?

• Lying flat side by side is probably the optimum positioning for a boat on a swinging mooring.
• I think I would wire them in series.
• Connect the positive output terminal of the controller to the positive terminal of the domestic battery bank ( or the positive busbar) via a fuse located as close as practical to the battery/ busbar connection.
• Connect the negative output terminal to the opposite end of the monitor shunt to the house battery negative. That is to the the same terminal that has what is labelled "system ground" in the monitor installation instructions connected. See https://www.victronenergy.com/upload/documents/Quick-install-guide-BMV602-website-EN.pdf
• The battery monitor will then monitor the solar input to the house battery along with other inputs and loads
• No there is no need to connect anything to the load terminals .
• whether or not the solar panels will also charge the starter battery once the house battery is charged depends on the type of VSR ( ie single or bidirectional) and on which battery is wired as the priority battery

 

[Redfox226]

• Lying flat side by side is probably the optimum positioning for a boat on a swinging mooring.
• I think I would wire them in series.
• Connect the positive output terminal of the controller to the positive terminal of the domestic battery bank ( or the positive busbar) via a fuse located as close as practical to the battery/ busbar connection.
• Connect the negative output terminal to the opposite end of the monitor shunt to the house battery negative. That is to the the same terminal that has what is labelled "system ground" in the monitor installation instructions connected. See https://www.victronenergy.com/upload/documents/Quick-install-guide-BMV602-website-EN.pdf
• The battery monitor will then monitor the solar input to the house battery along with other inputs and loads
• No there is no need to connect anything to the load terminals .
• whether or not the solar panels will also charge the starter battery once the house battery is charged depends on the type of VSR ( ie single or bidirectional) and on which battery is wired as the priority battery

+1
I have replaced a single 80W with 2x40W in series through a Victron 75/15. Remarkable improvement in low sunshine level charging!

 

[ghostlymoron]

I had a Lensum 20w on my last boat and it worked well.
As you proposal will probably shade one or other of the panels, I would connect them in parallel to avoid the shady one pulling down the other.
With smallish panels, I don't think that it's worth the expense of an MPPT controller. I'd just go for a PMW.

 

[gregcope]

I have the same regulator. Same location although mine spends more time N/S.

I have two panels. One one each side of the coach roof. Usually one in Sun, the other parial shade. Been really impressed with the output, in on overcast days. Wonder what I will get on a good summers day.

I went parallel. Works well, and I found this is what the panel and regulator instructions suggested. I made a custom box to parallel the panels, and added a plug for another (parralel) panel to be used in moorings to keep up with cooling the wine (aka run fridge). One set of 6mm wires run to regulator.

I would connect the regulator to the battery monitor shunt and other connection to the battery like the rest of the loads are connected so that it can report in/out, otherwise it will not see the panel output. Fuse near battery +ve.

 

[dunedin]

We were advised parallel to handle the one in shade issue.

If at all possible go bigger than 20W would be my suggestion

 

[gregcope]

We were advised parallel to handle the one in shade issue.

If at all possible go bigger than 20W would be my suggestion

I think that depends on the use case of the OP. If this is to top up from lightish weekend use, it should be not far off. If this is for light daily power usage without a fridge, I would still think it not far off (although the batteries would never get to 100%). If it is for daily use with Fridge I would agree.

 

[Aeolus]

Thanks very much to everyone who has replied, esp VicS with the very detailed wiring instructions. I note the comments about the size of the panels - there isn't much space for them on the boat and I think that 20W is the largest that will fit. It is to cover light weekend-style use so hopefully 2 x 20W will at least delay the need to run the engine/visit marinas.

Thanks again......Jonathan

 

[gregcope]

Thanks very much to everyone who has replied, esp VicS with the very detailed wiring instructions. I note the comments about the size of the panels - there isn't much space for them on the boat and I think that 20W is the largest that will fit. It is to cover light weekend-style use so hopefully 2 x 20W will at least delay the need to run the engine/visit marinas.

Thanks again......Jonathan

Do you have a sprayhood or lazyjacks? reason I ask is that you can string another 80W or so on those. My 100W panel will rest in the jackstays or on the sprayhood, and I intend to use this when stopped / marina / anchor / mooring to topup the fridge, over and above my 2x36W panels (same regulator)

 

[ghostlymoron]

I once had a Mirage 28 which I used mostly at weekends as still a wage slave. I found that the single 20w panel kept the batteries nicely topped up (no fridge though). It was a pleasure to check the lights on the controller when I got to the boat and find it reassuringly green.
In my opinion, rigging temporary panels when at anchor is an unnecessary chore - best to have them permanently deployed during the most productive part of the day.

 

[gregcope]

I once had a Mirage 28 which I used mostly at weekends as still a wage slave. I found that the single 20w panel kept the batteries nicely topped up (no fridge though). It was a pleasure to check the lights on the controller when I got to the boat and find it reassuringly green.
In my opinion, rigging temporary panels when at anchor is an unnecessary chore - best to have them permanently deployed during the most productive part of the day.

I agree that permeant is better. However my use case is similar to others in that I need something to trickle charge over the week (30W?), whilst during weekend or summer hols usage I need allot more to keep up with the fridge (150W+) and other use. However having 150W seems hard to mount, and overkill for the regulator to dump load.

 

[RichardS]

I agree that permeant is better. However my use case is similar to others in that I need something to trickle charge over the week (30W?), whilst during weekend or summer hols usage I need allot more to keep up with the fridge (150W+) and other use. However having 150W seems hard to mount, and overkill for the regulator to dump load.

Does your regulator have large heatsinks to dissipate the load or does it just disconnect the panels from the batteries? My controller has no heatsinks and does not get warm but perhaps there are other designs?

I'm thinking of getting a better controller but would prefer one that does not generate heat when I'm not on the boat, if there is a choice.

Richard

 

[gregcope]

Does your regulator have large heatsinks to dissipate the load or does it just disconnect the panels from the batteries? My controller has no heatsinks and does not get warm but perhaps there are other designs?

I'm thinking of getting a better controller but would prefer one that does not generate heat when I'm not on the boat, if there is a choice.

Richard

I has a metal "base" but I would not describe it as a heatsink.

 

[RichardS]

I has a metal "base" but I would not describe it as a heatsink.

If it's the base that's metal it's deffo not a heatsink. I guess that you controller does not dump the load but just disconnects the panel input when the batteries are fully charged like mine, which I think is a good design.

Richard

 

[VicS]

If it's the base that's metal it's deffo not a heatsink. I guess that you controller does not dump the load but just disconnects the panel input when the batteries are fully charged like mine, which I think is a good design.

Richard

The simplest controllers just disconnect when the battery volts reach a certain value (14.4 ??) and reconnect again when the volts fall to some lower value.

PWM regulators control the charging by breaking the charge current into pules of diminishing duration as the battery becomes fully charged. They maintain the battery in a high state of charge rather than allowing it to cycle between fully charged and some slightly lower state of charge.

MPPT controllers I believe may dump the excess current into a heat sink

 

[RichardS]

MPPT controllers I believe may dump the excess current into a heat sink

You might well be right.

I'm intending to upgrade to more powerful panels and use one of these Victron MPPT controllers as my Victron mains charger seems to be good quality:

https://www.victronenergy.com/uploa...-Blue-Solar-Charge-Controller-overview-EN.pdf

This is a general spec sheet for all their models and although I can't see any evidence of heat sinks in the photo of the model featured on the sheet, it does say that they all achieve "intelligent battery management by load shedding" ..... which sounds like some kind of load dumping.

Richard

 

[noelex]

MPPT controllers I believe may dump the excess current into a heat sink

The difference with MPPT controllers is in the voltage conversion to keep the panels at the optimum Vmp. The battery regulation uses PWM the same as the simpler PWM regulators. Although many MPPT regulators stop tracking Vmp when PWM modulation is employed. There is no point optimising power if it not going to be used.

MPPT regulators do not use a dump load although some can be programmed to use an external dump load (rather than PWM) if you want to use the regulator with a wind generator, or if you want to do something like heat water.

Think of a MPPT controller as a amalgamation of clever voltage conversion that is then connected to a PWM regulator. The voltage conversion optimises the panel output and the PWM part prevents the battery overcharging. Battery regulation is essentially the same in MPPT and non MPPT regulators (providing the non MPPT regulator is not one of the very simple on/off models)