Max MPPT controller for battery charging

[JT Marlin]

Hi, I am looking to better understand solar controller charging. I have searched but maybe I missed it or did not understand. I currently have a 12v Lithium bank with Valence batteries and the specification sheet says the max charge is 70A. So would be I be looking for a MPPT controller that outputs something like 70A or 85A. I was looking at the victron 250/100 but if I can only charge at 70A (or recommended anyway) I guess that would be a waste of money? Thanks

 

[kernel]

Hi, I am looking to better understand solar controller charging. I have searched but maybe I missed it or did not understand. I currently have a 12v Lithium bank with Valence batteries and the specification sheet says the max charge is 70A. So would be I be looking for a MPPT controller that outputs something like 70A or 85A. I was looking at the victron 250/100 but if I can only charge at 70A (or recommended anyway) I guess that would be a waste of money? Thanks

If you want to charge at max rate, you could use a controller as high as 70-100A the victron will have a max charge amps setting.

You otherwise could likely have a 60A controller and it could never exceed max charge current for the battery, same with only giving it so many amps worth of solar.

If there is an eye to expand, i would adopt a controller in excess of your current battery requirement. You could also add a controller later if needed.

Some systems are designed to meet a goal and are finished, so there may be the need to disregard much of this.

 

[kernel]

If your system will not have use for 800+ watts solar and not need the ability to recharge in an hour or two, you can use a smaller controller.

 

[ghostwriter66]

If your system will not have use for 800+ watts solar and not need the ability to recharge in an hour or two, you can use a smaller controller.

Exactly .. if you are NOT going to require a QUICK charge of 70 amps then I would save a ton of money and go with a 40A ...

HOW many amps are you bringing in to the MPPT? (ie Whats the wattage total of your system panels?)

 

[Craig]

The one reason to stick with the 250/100 is you can bring in higher volts from the panels if that is necessary.

 

[JT Marlin]

Thanks for all the input. I am glad I asked because I guess I did not have a full understanding . Yeah, like everbody I want to "GO BIG" but also dont want to waste money. I would like to have a 2000w system. I used the victron excel worksheet and put in the specs for the Rich Solar 200w panels. If I did 6 in series and 2 parallel that would give me 2400w with 157v. The part that prompted my questions was the yellow 100A max current. I saw that and know it means the max of the carger is 100A but was confused / concerned about the batteries charging at 70A. Seems like I am losing 30A of potential charging ability (of course under ideal conditions). Ghostwriter suggested maybe looking into using a smaller MPPT controller so If I got rid of 2 panels I could do the 150/85 MPPT controller for a lower cost!

I would be looking to add to the system when I move from my RV to a house I would like to move and expand the system so an eye to the future is good!

Thanks again everyone!

 

[ghostwriter66]

Thanks for all the input. I am glad I asked because I guess I did not have a full understanding . Yeah, like everbody I want to "GO BIG" but also dont want to waste money. I would like to have a 2000w system. I used the victron excel worksheet and put in the specs for the Rich Solar 200w panels. If I did 6 in series and 2 parallel that would give me 2400w with 157v. The part that prompted my questions was the yellow 100A max current. I saw that and know it means the max of the carger is 100A but was confused / concerned about the batteries charging at 70A. Seems like I am losing 30A of potential charging ability (of course under ideal conditions). Ghostwriter suggested maybe looking into using a smaller MPPT controller so If I got rid of 2 panels I could do the 150/85 MPPT controller for a lower cost!

I would be looking to add to the system when I move from my RV to a house I would like to move and expand the system so an eye to the future is good!

Thanks again everyone!

View attachment 8448

And actually i would not loose the 2 panels just yet ... so hook up the theoretical "maximum" voltage (take the MAX amount thats printed on the panel spec sheets - get as close as you can to the maximum rated voltage of the SCC you can but don't go over... .. then run it for 2 or 3 days of good sunlight to see if you are actually getting near the max of the AMPERAGE allowed ... if you are not ... then see if your current configuration will allow you to slap another panel on (so you may go from a 5 x 1 (5 panels in a string) to a 3 x 2 (3 panels in a string X 2 config) ...

ALLOT of times take a panel that has a rating output of 10A ... you may be lucky to get 8 on a good day ...so we often add amperage to get it to the max ..

NOW voltage is different ... you are going to get the maximum voltage almost the moment the light hits hit ... BUT its the AMPS that charges the battery -- not the volts .. I'm pretty sure i have lost you ... sorry

 

[JT Marlin]

Nope. I get it, I am tracking. That sound like a good plan. I wont be doing this for a few weeks yet but am getting all the resources together and this helps a lot. I will plan for the larger array and put them in a few at a time to see what I get.

Thanks

 

[Steve_S]

I cannot say for Victron, although I am sure they are capable, but with my Midnite Controller, I can program AMP limits for charging. It's better to have more capacity than needed as opposed to needing capacity that you don't have. Dive into the Victron manuals or even email their tech support folks and ask if the AMPS for charging can be managed. Quite possibly some here who use these in particular can answer that as well.

 

[Bob142]

I cannot say for Victron, although I am sure they are capable, but with my Midnite Controller, I can program AMP limits for charging. It's better to have more capacity than needed as opposed to needing capacity that you don't have. Dive into the Victron manuals or even email their tech support folks and ask if the AMPS for charging can be managed. Quite possibly some here who use these in particular can answer that as well.

I just got a Victron 100/20 and yup, you can limit the charge current. From section 4.1 Battery Settings of the VictronConnect manual:

Max charge current
Allows the user to set a lower maximum charge current.

victronconnect:mppt-solarchargers [Victron Energy]

www.victronenergy.com