Controller recommendation.

[Mudd]

I’m working on putting together an off grid solar set up for an RV. So far I’ve bought six panels 270 watts and ordered 8 280ah batteries via Michael’s group buy. I’m expecting The batteries to take a couple months to get here. I am attaching an image of the panels I have so you guys can help me decide on a proper controller. I was thinking about using the inexpensive controller that Will recommends in his 2000 watt budget build. I think my panels are too high voltage for the 40 amp controller but please correct me if I’m wrong.

 

[gnubie]

Voc 44.4, two in series 88.8, for an array configuraton of 2s3p. Depending on the temperature range in your area you could do that with a 105V rated charger so that gives you a lot of options when it comes to SCCs.

If you link to the web page for the particular controller in Will's setup I can tell you if the panels are going to be OK and in what configuration.

Current is going to be your issue. Since you have 8 cells I'm guessing you are building a 24V battery. Your array will have a paper maximum of 1.6kW. At 24V that yields 67.5A. A 40A controller will not be able to deliver full paper array power to the battery. Your array may never reach full power and you may be happy with a bit of clipping during the peak of the day but gain the benefit of a flatter charge curve across the rest of the day so that isn't necessarily a problem.

If the peak current from your array exceeds the maximum current rating on your controller's PV input you should have a fuse between the array and the controller if you are planning on over-panelling.

if you do 3p you should have an appropriate fuse between each 2s string and the common + wire.

 

[Mudd]

Thanks for taking the time to help me! This is the controller I was thinking about. I understand a larger controller would make more sense. The 40a controller I understand will be undersized. I’m thinking this Victron would be more appropriate but it seems kind of pricey. I understand it might make sense just to spend a few more bucks to get a quality scc to begin with.

Amazon.com

Amazon.com: Victron SmartSolar MPPT 150/85-MC4 Solar Charge Controller 150V 85A with Bluetooth : Patio, Lawn & Garden

Buy Victron SmartSolar MPPT 150/85-MC4 Solar Charge Controller 150V 85A with Bluetooth: Energy Controllers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

 

[gnubie]

With that one you could also do 3s2p, less and lighter wiring, no need for fusing between the strings since there are only two, and no electrical need for a fuse between the array and the charger since the max current from 2p would be miles under the charger's PV amp rating. If you use the MC4 variant of the controller each connected is, IIRC, rated at 30A so that's OK too.

 

[dehv]

Thanks for taking the time to help me! This is the controller I was thinking about. I understand a larger controller would make more sense. The 40a controller I understand will be undersized. I’m thinking this Victron would be more appropriate but it seems kind of pricey. I understand it might make sense just to spend a few more bucks to get a quality scc to begin with.

Amazon.com

Amazon.com: Victron SmartSolar MPPT 150/85-MC4 Solar Charge Controller 150V 85A with Bluetooth : Patio, Lawn & Garden

Buy Victron SmartSolar MPPT 150/85-MC4 Solar Charge Controller 150V 85A with Bluetooth: Energy Controllers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

I have used a 40A epever potted model like you linked to, and they are extremely robust - tolerant of over current potential but just limiting to 40A. They'll take up to 150V input i believe, so you could parallel two strings of 3 panels in series, and eat the potential gain getting over 40A in full sun OR

If it was me I'd buy 2 EPEVER 40s and run each series string of 3 into each unit, rather than one more expensive single unit. This also creates a kind of redundency in the unlikely event one gets nuked.

 

[snoobler]

The downside to 3S2P is that since this is an RV roof, shading on ONE of the 3S panels will hurt production on all 3 of those panels. If 2S3P, it only affects the two panels in series. If shading by roof penetrating items is not a concern, then 3S2P is probably the better choice. If these panels are to be used in extreme cold, 2S3P might also be the only option. Use in temps much below freezing will produce a voltage spike that could exceed the 150V rating of the charge controller.

 

[dehv]

I guess it depends if the panels have bypass diodes, which most do.

 

[snoobler]

I guess it depends if the panels have bypass diodes, which most do.

Most do, but that doesn't mean the impact of shading isn't substantial.

 

[Mudd]

I have used a 40A epever potted model like you linked to, and they are extremely robust - tolerant of over current potential but just limiting to 40A. They'll take up to 150V input i believe, so you could parallel two strings of 3 panels in series, and eat the potential gain getting over 40A in full sun OR

If it was me I'd buy 2 EPEVER 40s and run each series string of 3 into each unit, rather than one more expensive single unit. This also creates a kind of redundency in the unlikely event one gets nuked.I was also thinking two Inexpensive controllers would be the way to start out inexpensive controllers would be the way to start out.

 

[Mudd]

I have used a 40A epever potted model like you linked to, and they are extremely robust - tolerant of over current potential but just limiting to 40A. They'll take up to 150V input i believe, so you could parallel two strings of 3 panels in series, and eat the potential gain getting over 40A in full sun OR

If it was me I'd buy 2 EPEVER 40s and run each series string of 3 into each unit, rather than one more expensive single unit. This also creates a kind of redundency in the unlikely event one gets nuked.

I have used a 40A epever potted model like you linked to, and they are extremely robust - tolerant of over current potential but just limiting to 40A. They'll take up to 150V input i believe, so you could parallel two strings of 3 panels in series, and eat the potential gain getting over 40A in full sun OR

If it was me I'd buy 2 EPEVER 40s and run each series string of 3 into each unit, rather than one more expensive single unit. This also creates a kind of redundency in the unlikely event one gets nuked.

Thanks I think this route makes a lot of sense for me.