Adding panels and picking controller

Bluedog225

Texas
Joined
Nov 18, 2019
Messages
971
I’d appreciate a second opinion to verify my understanding.

I’ve got three 100w Renogy panels (identical but different ages) and two Battle Born Batteries (12v). The batteries will be wired in parallel.

Entire load is 12 volt man cave stuff (lights, TV, 12 volt tool charger).

Battle recommends 200 to 250 watts per battery.

I’d like to bump up my capacity to 500 watts. Therefore moving to 5 panels at 100w. (I’m going to disregard the issues related to different panel ages.). I’ll try to get similar 100W panels with open circuit voltage (22.5V) and short circuit current (5.75A).

1. If I get a Victron 150/35, can (or should) I run the panels in series for a open-circuit voltage of 112.5 and something like 4.4 amps? Or is different series or parallel arrangement preferred? I can cut it back to 4 panels and go 90V, or two in series at 45v. I don’t understand the considerations here, partucularly with regard to safety.

2. Am I right in thinking this controller can take high voltage input from the panels (up to 150V and still charge to 12 volt batteries?

3. And finally, where do I check the cold temperature volts t0 make sure I don’t exceed 150?

Any thoughts appreciated.

Thanks
 

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Rocketman

Solar Addict
Joined
Sep 27, 2020
Messages
698
1. Yes a 150/35 should work. You have 20% to spare until the voltage max, but if you want to know for sure there is a temp label on the panel that says .30%/C - what is the all time cold temp for your area? Your panels get .30% more efficient for every degree C they drop from standard temp. (I messed the calculations up last time - so I will let someone else do that math).

2. Yes

3. In the Victron connect app when you set the charge voltages for bulk, etc. there is a field for Low Temp Cuttoff. You can set it however you wish - mine is set to 42F.

3a. Will your SCC be near your battery? The mppt has an internal temp sensor, so if the mppt is the same temp as the batteries- you are good. If the mppt and batteries are in different temperature places, get a Smartshunt- it will pass the temperature and voltage and current to the mppt. (I would recommend getting the Smartshunt anyways - that way you know the status of the batteries. (How full/empty they are - what is happening right now, etc).

One really cool thing with the Victron app, is you can see all the settings for a particular device(even before you buy it). To access that - download / open the app. Find the “Demo library”. (Under the three horizontal bars). Then select the device mppt 150/35 and you can see all the screens.

1a. I would not spend any more on those cheap panels. See if you can find used panels or call and talk to solar installers in your area - many time they have orphaned panels they will see cheap (see suntan solar for used).
 

Bluedog225

Texas
Joined
Nov 18, 2019
Messages
971
Got it. Thanks!

Do I care (or should I) about what voltage I end up at from the panels (within limits)? E.g.: 112v versus 48 v? Or is coming under 150/35 all that matters?

Time to let go of the old panels. Ok. Sorry to see them go.
 
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