34V panels Vs 18 to 21V panels? (1 Viewer)

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Apr 6, 2019
3,942
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Eye, Peterborough, UK
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FourWinds Windsport 6.8L V10
I hadn't realised there are different voltage solar panels you could potentially put in the Motorhome roof.
I assumed they were mainly 18 to 22V open volts rating - based on panels I have actually seen.
Just seen a second hand 375watt panel but label says 34V...
I guess they shouldn't be mixed on one controller but is there an advantage to 34V ?
Victron 100/30 appears able to cope with up to 100V?
 
Apr 27, 2016
7,008
8,205
Manchester
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42,762
MH
A class Hymer
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Since the 80s
For a solar controller to function, a panel needs to have a voltage of at least 5V above the system battery voltage. An 18 to 22V panel is OK for 12V systems, but no good for 24V systems. Domestic systems typically have 24V or 48V batteries, so they have higher voltage panels, more like 30 to 40V.

Fitting large domestic panels to motorhomes used to be unusual, but it's getting quite normal now. I think they probably need an MPPT controller, I don't think a PWM type is good for this.

Victron make a large range of solar controllers for anything from small road signs to domestic and industrial solar arrays, so you're sure to find a suitable controller whatever your panel configuration. Other brands like Votronic and Renogy are also suitable.
 
Dec 2, 2019
3,679
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Amersham
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van conversion
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Since 2019
On my van I have two panels in parallel, coupled to a 100/50. Most of the time the voltage is at 45-50v. It wakes up sooner and starts charging, and shuts down later. The 18-22v it’s just bare minimum for a mppt. These are old behaviour from pwm small leisure controllers. Now we have mppt’s that can handle higher voltage, therefore a 34v will be a good choice. Why? Larger industrial panels have to get accreditation’s to comply with grid distribution regs, much higher quality and longevity. Small leisure panels don’t last as long or as efficient, they don’t need to pass any accreditation’s, and they can’t be fitter on a house either, unless the relevant UL, MCS etc is stamped on them with a barcode, so it can be identified, and cross referenced on the certificate from manufacturer.
I always encourage ppl to go for large 60 cell plus panels, if you got the space.
 
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OP
Jev88
Apr 6, 2019
3,942
7,797
Eye, Peterborough, UK
Funster No
59,702
MH
RV
Exp
FourWinds Windsport 6.8L V10
I already have 100/30 Victron Smartsolar controller (MPPT) and two ordinary 80 to 100 watt panels on the roof (unknown age) but tempted to add more and saw an offer on the 34V panel and wanted to check there wasn't some technical reason I couldnt use it. It would probably be simpler for me to remove the two and replace with one 375watt is approximately the same place.
 
Dec 2, 2019
3,679
7,943
Amersham
Funster No
67,145
MH
van conversion
Exp
Since 2019
I already have 100/30 Victron Smartsolar controller (MPPT) and two ordinary 80 to 100 watt panels on the roof (unknown age) but tempted to add more and saw an offer on the 34V panel and wanted to check there wasn't some technical reason I couldnt use it. It would probably be simpler for me to remove the two and replace with one 375watt is approximately the same place.
Yes I would remove the existing and stick the 375w in there. You will get better performance, and with the victron 100/30 it’s a very good match.

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Jul 6, 2009
1,865
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I have four 175 watt panels linked in pairs and produce around 70v and around 700 watts at times this will depend on the state of the batteries 2 x 100 amp Lithium

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