How to join 3 solar panels? (Might be a stupid question)

[PaulC70]

OK, so I have my 3rd ecoworthy panel, couldn't resist, they sent me a 15 quid off so got it for only 65 quid.

Now, as you can see on the first picture, this is my intended layout on the motorhome roof, I've measured, there's enough room so Im happy.

My query (and it may be a stupid one) is how to join them all together? I don't mean red to red etc I already know I need x 2 triple to single mc4 connectors like these

However, as you can see in the picture below there's no way the current cables attached to the actual panels will reach.

So, back to my probably stupid question, how to join?

My thought is that I need to buy a kit like this and some panel wire and extend the ones already attached to the 3 way?

Am I on the right track?

 

[RogerIvy]

Extending is ok as long as you use UV-stabilised cabple (like solar cable)
Easier to buy solar cables with female on one end and male on the other (like an extension).

 

[Sheddy]

If you use 2 way connectors twice you may not need to extend the cables, worth a look.

 

[gus-lopez]

don't mean red to red etc I already know I need x 2 triple to single mc4 connectors like these

That is only correct if you wish to jpoin them in parrallel.All positives together & all negatives together.This gives a better performance if you get shade on a panel.
Whereas you can also join them in series . negaitive to positive,negative to positive then all you have are one positive on one end panel & a negative on the other end panel
If in parallel then it is the Imp solar current that has to be below the max for the MPPT but as near to it as possible
I.e if Imp =12A then x 3 panels =36A
If in series then it is the open circuit voltage (VOC) that determines the maximum for the MPPT & it must be less than the Vmax on the mppt.
I .e voc is 23v then x 3panels = 69V Vmax has to be above this on the mppt
Problem with in series is if you shade even part of one panel it drops the performance substantially.
Raul might offer better adviceor Lenny HB

 

[PaulC70]

That is only correct if you wish to jpoin them in parrallel.All positives together & all negatives together.This gives a better performance if you get shade on a panel.
Whereas you can also join them in series . negaitive to positive,negative to positive then all you have are one positive on one end panel & a negative on the other end panel
If in parallel then it is the Imp solar current that has to be below the max for the MPPT but as near to it as possible
I.e if Imp =12A then x 3 panels =36A
If in series then it is the open circuit voltage (VOC) that determines the maximum for the MPPT & it must be less than the Vmax on the mppt.
I .e voc is 23v then x 3panels = 69V Vmax has to be above this on the mppt
Problem with in series is if you shade even part of one panel it drops the performance substantially.
Raul might offer better adviceor Lenny HB

OK, bear with me.
So the Imp is the max power current which on these panels is 9.85a therefore 3 panels in parallel is 9.85a x 3 = 29.55a

As I have a victron 100/20 solar controller, the 20 signifying 20a being the rated charge current and therefore looks like I need to upgrade to the 100/30 ?

 

[Dannco75]

OK, bear with me.
So the Imp is the max power current which on these panels is 9.85a therefore 3 panels in parallel is 9.85a x 3 = 29.55a

As I have a victron 100/20 solar controller, the 20 signifying 20a being the rated charge current and therefore looks like I need to upgrade to the 100/30 ?

You'd be limited to 20a. An upgrade would be ideal if possible.
I just got the 100/30 for 70 quid on ebay

 

[autorouter]

As I have a victron 100/20 solar controller, the 20 signifying 20a being the rated charge current and therefore looks like I need to upgrade to the 100/30 ?

Be careful here. The '20' in the 100/20 tells you the maximum output amps of the controller to the battery, not the input amps to the controller from the panels. If the panels are outputting 20A at 28V, the controller will convert that to about 40A at 14V, and send it out for charging the batteries. In your case it probably won't be as bad as that, it won't be double the amps, but it certainly will be above 30A.

To do the calculation, multiply the Vmp and Imp, it should give you the panel power rating in watts. To find the likely output amps of the solar controller, divide the power rating in watts by the battery charging voltage, about 14.5V. That will give you the maximum output amps into the battery.

As an alternative strategy, if you are going to have to buy another solar controller anyway, you could see if two of the panels would be OK through a Victron 100/30. You haven't said what power the panels are, I'm guessing 200W to 250W. Then put the third panel through the existing 100/20 controller, and connect both controllers to the battery. An advantage of this is it gives you some extra redundancy in case one of the controllers fails.

 

[PaulC70]

Be careful here. The '20' in the 100/20 tells you the maximum output amps of the controller to the battery, not the input amps to the controller from the panels. If the panels are outputting 20A at 28V, the controller will convert that to about 40A at 14V, and send it out for charging the batteries. In your case it probably won't be as bad as that, it won't be double the amps, but it certainly will be above 30A.

To do the calculation, multiply the Vmp and Imp, it should give you the panel power rating in watts. To find the likely output amps of the solar controller, divide the power rating in watts by the battery charging voltage, about 14.5V. That will give you the maximum output amps into the battery.

As an alternative strategy, if you are going to have to buy another solar controller anyway, you could see if two of the panels would be OK through a Victron 100/30. You haven't said what power the panels are, I'm guessing 200W to 250W. Then put the third panel through the existing 100/20 controller, and connect both controllers to the battery. An advantage of this is it gives you some extra redundancy in case one of the controllers fails.

Ah ok, thank god I asked.
So this is the spec for the ecoworthy bifacial panels from their site, 195w each

So looking at victron specs of the 100/30 it appears it can only handle up to 440w whereas the 100/50 can handle up to 700w, so as I've got nearly 600w surely the latter is the one to go for?

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[herald_400rl]

Ah ok, thank god I asked.
So this is the spec for the ecoworthy bifacial panels from their site, 195w each

View attachment 1202563

So looking at victron specs of the 100/30 it appears it can only handle up to 440w whereas the 100/50 can handle up to 700w, so as I've got nearly 600w surely the latter is the one to go for?

Victron recommend the 100/50 for that with panels in series, 42a max charging capacity.

As already said, a 2nd mppt 100/30 and a 100/20 you have existing would do the job.

 

[autorouter]

440W is 30A at 14.7V, so it appears they are using 14.7V as the charging voltage for their wattage calculation. Using that 14.7V figure, your 195W panel will produce 195 / 14.7 = 13.3A. So for two and three panels that's 26.5A and 39.8A.

So as you say, a 100/50 could handle all three at once. Or if you already have a 100/20 that would be fine for one panel, plus a 100/30 for the other two panels.

The other consideration is the solar panel connections, series or parallel. That makes a difference to the wire thickness required between the panels and the controller. 3 panels in parallel will send 3 x 9.85 = 29.6A, so the cable will need to cope with that. Using two separate controllers as suggested means the amps will be 9.85A and 19.7A for one and two panels.

 

[PaulC70]

Thanks again for the input everyone.
I was thinking of using a single victron solar controller for all three panels to be honest, in parallel.
2 reasons.
1. simplicity ie one controller for the triple solar array and one pair of wires (which I need to figure out what size to use)
2. As I have a single 100w flat bonded to the roof truma also on the roof, I was going to repurpose that and the current 100/20 for keeping the vehicle battery charged.

So, if I continue down the parallel route and a victron 100/50 does anyone know what size mc4 wires I need to order?

 

[herald_400rl]

Thanks again for the input everyone.
I was thinking of using a single victron solar controller for all three panels to be honest, in parallel.
2 reasons.
1. simplicity ie one controller for the triple solar array and one pair of wires (which I need to figure out what size to use)
2. As I have a single 100w flat bonded to the roof truma also on the roof, I was going to repurpose that and the current 100/20 for keeping the vehicle battery charged.

So, if I continue down the parallel route and a victron 100/50 does anyone know what size mc4 wires I need to order?

Depending on length of run, but probably 6mm

 

[starquake]

So, if I continue down the parallel route and a victron 100/50 does anyone know what size mc4 wires I need to order?

YOu may want to reconsider. Running mutliple controllers is a bonus when partial shading occurs (ie, you can get production from the unshaded panels).

If you go parallel all must have sun at same time to produce. This reason is why most sailboat and motorhome systems often run a controller per panel (or per pair). As you want if you get tree shade over the van to still produce if only say one panel is shaded.

 

[PaulC70]

YOu may want to reconsider. Running mutliple controllers is a bonus when partial shading occurs (ie, you can get production from the unshaded panels).

If you go parallel all must have sun at same time to produce. This reason is why most sailboat and motorhome systems often run a controller per panel (or per pair). As you want if you get tree shade over the van to still produce if only say one panel is shaded.

I don't, like I said, I need to keep it as simple as possible and parallel is better than series for partial shade.
I'll be using the old 100/20 for the cab battery as it can be powered by the single 100w truma left over on the roof. If I follow what you are asking me to consider I will end up with 3 solar controllers in total and that's just not going to happen.

 

[bigtwin]

If you go parallel all must have sun at same time to produce.

Erm, I think that you mean in series.

Parallel is preferable if you wish to minimise the impact of shading.

Ian

 

[autorouter]

So, if I continue down the parallel route and a victron 100/50 does anyone know what size mc4 wires I need to order?

It depends on the length of the wires. You could use a voltage drop calculator such as this one:

Voltage Drop Calculator | 12 Volt Planet Cable Calculator

Use our Voltage Drop Calculator to select the correct Cable for your campervan, motorhome or boat wiring application. Cable Calculator for Auto and Marine Electrical Components from 12 Volt Planet - Cable Size Calculator

www.12voltplanet.co.uk

Put in the length, system voltage (12V), and current draw (30A) and choose a wire size such as 6mm². For a 2m length it gives you 3.14%, which is just about acceptable. That's 2m positive and 2m negative.

The idea is to keep the voltage drop to 3% or less. If you need 3m lengths, then the next one up, 10mm², is required, which gives a voltage drop of 2.71%. With this calculator you can work it out for yourself.

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