Another beginner question. Plug in RV shore power cord to inverter wired to battery?

[DouglasPaul]

Probably get a couple sniggers, but can I charge my batteries with my scc and plug the shore power cord into a inverter at the same time? Or will I just get a huge spark and end up having to buy a bunch of new equipment?

2, soon to be 3 12v 100ah LiFePO4 batteries
1 Victron 100/50 mppt
2 255 watt panels

 

[FilterGuy]

Probably get a couple sniggers, but can I charge my batteries with my scc and plug the shore power cord into a inverter at the same time? Or will I just get a huge spark and end up having to buy a bunch of new equipment?

2, soon to be 3 12v 100ah LiFePO4 batteries
1 Victron 100/50 mppt
2 255 watt panels

Probably yes, but what kind of inverter do you have?

 

[DouglasPaul]

I haven't bought one yet, still deciding.

 

[FilterGuy]

I haven't bought one yet, still deciding.

In general, there are no issues with multiple chargers other than too fast of a charge on the batteries.

You will have 300ah batteries, Assuming the BMSs don't put other limits on the charge rate, the ideal charge would be .2C or 60A.

The two 255W panels (510W total) will charge at about 510W/13.4V = 38A. (in real life it will probably be closer to 30A) That means if you set the inverter to charge at 22A it should be just fine. Even 30A from the inverter would probably be fine.

You can charge faster, but I would not go above .5C (150A)

 

[chrisski]

I am set up to do that. You do need to check to make sure the RV converter and solar production don’t exceed the max your batteries take.

My max charge rate for lead acid was 60 amps and I would take the generator out and run that in the shore power getting 10.5 amps and perhpas 10 amps from the panels on a cloudy day, but if the clouds lifted, I could get close to the 60 amp limit.

For me, I also needed to remember to shut the converter off after I was done charging that way.

 

[DouglasPaul]

In general, there are no issues with multiple chargers other than too fast of a charge on the batteries.

You will have 300ah batteries, Assuming the BMSs don't put other limits on the charge rate, the ideal charge would be .2C or 60A.

The two 255W panels (510W total) will charge at about 510W/13.4V = 38A. (in real life it will probably be closer to 30A) That means if you set the inverter to charge at 22A it should be just fine. Even 30A from the inverter would probably be fine.

You can charge faster, but I would not go above .5C (150A)

I have two more of the same panels but am waiting on non cloudy days before I hook them up to make sure I don't go over the limit with them. Pretty sure I can use at least one more.

 

[FilterGuy]

I have two more of the same panels but am waiting on non cloudy days before I hook them up to make sure I don't go over the limit with them.

What is the Voc on the panels? Be sure to factor in cold temp voltage rise.

Adjusting Solar Panel Voc for temperature

When designing you solar panel system, it is important to adjust you solar panel Voc for temperature in order to ensure you do not over-voltage the PV inputs of your solar charge controller. This paper shows how to calculate the Temperature...

diysolarforum.com

 

[DouglasPaul]

What is the Voc on the panels? Be sure to factor in cold temp voltage rise.

Adjusting Solar Panel Voc for temperature

When designing you solar panel system, it is important to adjust you solar panel Voc for temperature in order to ensure you do not over-voltage the PV inputs of your solar charge controller. This paper shows how to calculate the Temperature...

diysolarforum.com

37.4, used panels from San Tan Solar. By the time they start charging the temps around here aren't that low.

 

[DouglasPaul]

Also, I have a Victron battery sense on the way.

 

[FilterGuy]

37.4, used panels from San Tan Solar. By the time they start charging the temps around here aren't that low.

3S would make Voc 37.4 x 3 = 112V. I would not do that at all. Instead, I would do 2S2P



However, this is significantly over-paneling the Victron. The most you will ever get out of the Victron is about 50A x 13.4 = 670W.
This is not necissarily bad.... you will get better production on cloudy days and in the winter.

Note: The spec for the 100/50 calls for an array Isc mac of 60A. Your panel Isc is probably well under 10A so the array Isc would be under 20A, but I thought I would point this out.

 

[DouglasPaul]

3S would make Voc 37.4 x 3 = 112V. I would not do that at all. Instead, I would do 2S2P

View attachment 126645

However, this is significantly over-paneling the Victron. The most you will ever get out of the Victron is about 50A x 13.4 = 670W.
This is not necissarily bad.... you will get better production on cloudy days and in the winter.

Note: The spec for the 100/50 calls for an array Isc mac of 60A. Your panel Isc is probably well under 10A so the array Isc would be under 20A, but I thought I would point this out.

I really appreciate that. I'm going slow because I'm still in the process of learning all this, thank you.

 

[DouglasPaul]

3S would make Voc 37.4 x 3 = 112V. I would not do that at all. Instead, I would do 2S2P

View attachment 126645

However, this is significantly over-paneling the Victron. The most you will ever get out of the Victron is about 50A x 13.4 = 670W.
This is not necissarily bad.... you will get better production on cloudy days and in the winter.

Note: The spec for the 100/50 calls for an array Isc mac of 60A. Your panel Isc is probably well under 10A so the array Isc would be under 20A, but I thought I would point this out.

I made a crude outline of what my actual layout would look like in that configuration, does this look right? T and B refer to top and bottom row of your example.

 

[FilterGuy]

I made a crude outline of what my actual layout would look like in that configuration, does this look right? T and B refer to top and bottom row of your example.View attachment 126839

That works

 

[DouglasPaul]

That works

I did this yesterday morning because it was really cloudy and I thought it would stay that way. It worked well, however it cleared up in the afternoon some so I checked the system to see how it was handling it, I think it was too much for that controller so I shut off the panels and went back to 2 panels. It was bumping up on 50 amps ( or more ) and the controller was pretty warm. I don't think I will use that configuration unless I know it's going to rain all day.

 

[FilterGuy]

It was bumping up on 50 amps ( or more ) and the controller was pretty warm.

That is exactly what I would expect. The Victron will hold the output at about 50 amps. At that point the controller is working at it's max capacity and will run very warm. Victron designs it's equipment to handle that.

The one thing you should be sure to do is properly torque the connections (Particularly the battery side) If you put a thermal imager on the unit, the 50A connection is probably the hottest part of the unit even when the connections are proper. Large currents and bad connections don't play nice together.

 

[DouglasPaul]

That is exactly what I would expect. The Victron will hold the output at about 50 amps. At that point the controller is working at it's max capacity and will run very warm. Victron designs it's equipment to handle that.

The one thing you should be sure to do is properly torque the connections (Particularly the battery side) If you put a thermal imager on the unit, the 50A connection is probably the hottest part of the unit even when the connections are proper. Large currents and bad connections don't play nice together.

Thanks for the advice. I don't need that kind of power as far as I can tell though, so I think I'll stick to only using the extra panels on really crappy days. Everything is nice and tight, Monday I have a ferrule and crimper set coming to improve the connections.