Small 24v Victron setup

[SunDave]

Hi. On an off-grid cabin I have 800 watts of solar, and a solar charge controller that doesn't work too well. I am new to Victron gear, and was hoping someone could take a look at these items and let me know if they would be decent.

The solar comes in at about 95 volts open circuit, so it works according to the spec sheets. Is there tolerance for cold weather, etc. required or is that figured in to Victron specs? The spec sheets don't have much info. Like it is meant to be simple. Other than that, it's just a 200amp hour 24 volt AGM battery bank that rarely gets used. I have a generator and 24v charger to top the batteries up when needed. Thanks all!

 

[rodrick]

That controller will only handle 100 volts max, your 95 volt present setup would go over at low temperatures can you wire the array differently

 

[rodrick]

What type of panels do you have, can you get a pic of of the specs on the back of the panel

 

[sunshine_eggo]

The 30A is sufficient for the 800W array.

If the panels are 2S, you could reconfigure with all in parallel and still fully utilize the charger.

 

[SunDave]

That controller will only handle 100 volts max, your 95 volt present setup would go over at low temperatures can you wire the array differently

Good to know. Thanks.

What type of panels do you have, can you get a pic of of the specs on the back of the panel

I don't have that handy since they have been up for 10 years or more, but I can find it when I go there next.

The 30A is sufficient for the 800W array.

If the panels are 2S, you could reconfigure with all in parallel and still fully utilize the charger.

They are indeed 2S. Good thinking. I believe they are approx 24v VOC, so I couldn't go all parallel and get the 5v over 24 volt like Victron manual states.

The solar charger can be used with a PV configuration that satisfies both these two conditions:

• The maximum open circuit PV voltage can not exceed 100V.
• The nominal PV voltage should be at least 5V higher than the battery voltage.

But we are getting close. Instead of two strings in series, then paralleled (sorry, not up on the S/P lingo), could I do something like paralleling 4 panels, then putting two groups of those in series. Been a long day, so if it could be the wrong idea all together, but I am trying to think of a way to work with the controller limits.

If this works it could be approx 40 volts and 20 amps using running voltage instead of SOC.

 

[rodrick]

How many panels are there in your system and what size

 

[SunDave]

removed the drawing. Apparently I'm too tired to work on this now! I just need a way ideally to wire all 8 so that I'm around 50 volts and under 30 amps to use the 100/30 victron. Seems doable.

How many panels are there in your system and what size

8 panels, 100 watt. approx 24v open circuit voltage. Don't have the exact specs where I am at.

Thanks to both of you for helping me think through this.

Victron panel calculator seems to work out in this config:

 

[rodrick]

You could run 2 strings of 3 with a branch connector no problem and also use a 75/15 scc with 2s configuration

 

[JanisD]

I would suggest 2S4P ( = make 4 strings of 2 panels each, than all 4 strings in parallel ) as in Victron configuration sheet. In this setup the 100/30 MPPT alone will be happy with voltage and current below limits.

 

[sunshine_eggo]

Good to know. Thanks.

I don't have that handy since they have been up for 10 years or more, but I can find it when I go there next.

They are indeed 2S. Good thinking. I believe they are approx 24v VOC, so I couldn't go all parallel and get the 5v over 24 volt like Victron manual states.

They can't be 2S @ 24Voc and yield 90-95Voc.

Sounds like they're 4S2P

2S4P would work fine.

The solar charger can be used with a PV configuration that satisfies both these two conditions:

• The maximum open circuit PV voltage can not exceed 100V.
• The nominal PV voltage should be at least 5V higher than the battery voltage.

But we are getting close. Instead of two strings in series, then paralleled (sorry, not up on the S/P lingo), could I do something like paralleling 4 panels, then putting two groups of those in series. Been a long day, so if it could be the wrong idea all together, but I am trying to think of a way to work with the controller limits.

2S4P =

String 1: two panels in series
String 2: two panels in series
String 3: two panels in series
String 4: two panels in series

The 4 strings in parallel.

You'll either need a combiner box, or 4X MC4 fuses - one per string.

If this works it could be approx 40 volts and 20 amps using running voltage instead of SOC.

Huh?

 

[rodrick]

I would suggest 2S4P ( = make 4 strings of 2 panels each, than all 4 strings in parallel ) as in Victron configuration sheet. In this setup the 100/30 MPPT alone will be happy with voltage and current below limits.

Then he needs a combiner box to do it correctly and a good box is more money than the victron 75/15 the only thing is possible wire costs

 

[SunDave]

Thanks all. I have a combiner box and DC breakers now. A couple more breakers or fuses and I'm all set. I mis-stated some things like calling VOC, SOC above. And you are correct eggo, there are 4 in series, then paralleled now.

I think with the 100/30 victron and the 2S4P as suggested, that could work out great.

 

[SunDave]

I decided to make my life one step easier and order the slightly more expensive victron 150/35 solar charge controller. That way there is no re-wiring required. When I was first looking at options, I thought some of the small charge controllers were for 48v batteries only. Turns out they often work with 12, 24, 48, and sometimes even 36 volt.

 

[Brucey]

I decided to make my life one step easier and order the slightly more expensive victron 150/35 solar charge controller. That way there is no re-wiring required. When I was first looking at options, I thought some of the small charge controllers were for 48v batteries only. Turns out they often work with 12, 24, 48, and sometimes even 36 volt.

Yes the 150s will work on all and autodetect on first power up except 36V which you would have to use victron connect for.

Just the rs450s that are 48V only.