PV too high after install

[Jpg40]

Hello all,

I’ve installed two 200 Watt (corrected, had as amps ?‍) Renogy panels in parallel on a Van. These are tied in to a Renogy DC-DC MPPT charge controller.
Panel voltage should be 22V optimum for both and 27V open circuit.

I am getting 26.1V to the charge controller, from either panel. Confirmed similar voltage at each panel.
It is very sunny but also cold, about 5 Celsius.
By covering both panels about 10%, I was able to get the voltage down to 23V so the PV high alarm on the controller turned off and it would start charging the battery. Threshold for max PV is right around 25V.

Any ideas on what may be causing this issue and thoughts on how to correct it?

 

[sunshine_eggo]

You have purchased panels that are incompatible with the controller.

25Voc limit on the MPPT.
27Voc on the panel.

 

[timselectric]

Get a better SCC, with a higher VOC.

 

[Sky Noris]

Yep as stated you need SCC that has a higher maximum voltage. FYI your panels are 200 watt not 200 amp

 

[Jpg40]

Oh no, rookie mistake ?‍
That makes so much sense, blindly expected the Renogy SCC to be compatible with their panel without checking spec. Thank you both.
Too bad, I really like the Renogy dc-dc mppt combo charger, but I’m not about to replacd the panels. Any recommendations on a replacement? Ideally with built in dc dc charging by alternator

 

[Jpg40]

Yep as stated you need SCC that has a higher maximum voltage. FYI your panels are 200 watt not 200 amp

Thanks, right! Well… 200 amp at 1 volt maybe? ?

 

[Sky Noris]

That's one way to learn about charge controllers. Some burn up if you exceed the voltage limit.

 

[sunshine_eggo]

Oh no, rookie mistake ?‍
That makes so much sense, blindly expected the Renogy SCC to be compatible with their panel without checking spec. Thank you both.
Too bad, I really like the Renogy dc-dc mppt combo charger, but I’m not about to replacd the panels. Any recommendations on a replacement? Ideally with built in dc dc charging by alternator

Unfortunately, there are very very few units that offer both PV and alternator charging. I believe it's also a part of why there's such a low PV limit - common negative ground between house, chassis and PV systems.

Renogy and victron make alternator-only DC-DC chargers. You'll need a separate PV MPPT controller.

Alternatively, Battleborn sells a product that shorts house to chassis system, but it limits the duty cycle to about 50%.

LiFePO4 Battery Isolation Manager (BIM)

LiFePO4 Battery Isolation Manager (also known as the BIM) monitors voltage and connects and disconnects batteries when needed. Click here to read more!

battlebornbatteries.com

 

[chrisski]

I recommend you keep the Renogy for DC ALTERNATOR to DC BATTERY charging and get a separate SCC to charge the panels.

For a 12 volt battery a Victron 100/30 MPPT SCC would work. Your panels MAY be out of specs max voltage input wise to use a cheaper PWM charger. Theres other cheaper MPPT controllers.

 

[Bvillebob]

For a similar setup I'm using a Kisae DMT1250, it's sold under several names. It has MPPT solar charge controller and also a DC/DC converter which is fed from the alternator to charge the lithium batteries when the engine is running. I have 400 watts of solar attached to it and a 280 amp hour 12v lithium house battery. It's been working for about a year for me, doing a great job.

Here's a good source,

DonRowe.com

 

[sunshine_eggo]

For a similar setup I'm using a Kisae DMT1250, it's sold under several names. It has MPPT solar charge controller and also a DC/DC converter which is fed from the alternator to charge the lithium batteries when the engine is running. I have 400 watts of solar attached to it and a 280 amp hour 12v lithium house battery. It's been working for about a year for me, doing a great job.

Here's a good source,

DonRowe.com

Interesting unit. 50A DC-DC and PV input of 30A with 14.5-50Voc. Nice.

https://www.kisaepower.com/wp-content/uploads/2020/04/AbsoCharger_Manual_DMT12V_24V-Series_Rev-D_190612_Print.pdf

 

[meetyg]

One "quick and dirty" solution might be to add some blocking diodes from the panels to the SCC. A standard diode will lower the voltage by around 0.6v. So if you put one diode for each panel and maybe another one after the parallel connection (before the SCC) you might get enough drop in voltage (almost 2v in total).

There are diodes like this integrated into MC4 connectors, so it's easy to do. Just make sure you get ones rated with proper amperage for your panels (say 10-15A each) and for the parallel connection (say 20-30A).

For example:

2.7US $ 45% OFF|1pc DC Diode Solar Plug Connector IP67 Solar Photovoltaic Diode Connectors 1000V 10A/15A/20A for Solar PV System|Connectors| - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

 

[fratermus]

For a similar setup I'm using a Kisae DMT1250

I was going to recommend that if no one else did. The 50V input is the most generous I've found on combo units.

Behaviorally, the biggest difference is the Renogy prefers solar charging and the Kisae by degault prefers the alternator.

 

[sunshine_eggo]

I was going to recommend that if no one else did. The 50V input is the most generous I've found on combo units.

Behaviorally, the biggest difference is the Renogy prefers solar charging and the Kisae by degault prefers the alternator.

I missed that. Looks like it charges exclusively from the alternator when moving or solar when stationary. Never both at once.