• Have you tried out dark mode?! Scroll to the bottom of any page to find a sun or moon icon to turn dark mode on or off!

diy solar

diy solar

Created a third system today!

WorldwideDave

Solar Addict
Joined
Mar 5, 2024
Messages
2,100
Location
90266
Long read, so I put questions in bold. Thank you in advance for reading - ignore if you don't care :-)
Equipment:
  • Costco 12V AGM 95Ah battery to test the build with. Free! Damn heavy. About 18 months old. Got it to float on charger yesterday, added to system today. Awesome!
  • Brass marine terminal screw adapters
  • Victron kill switch left over from prior build
  • Victron 500Ah non waterproof/older shunt left over from a project a year ago
  • Victron battery temp sensor left over from project 4 months ago.
  • AWG 1 left over from prior 2 projects.
  • Blue Sea bus bars left over from prior project. One is 1/4" lug (will swap out) and the other is 5/16 lugs.
  • Victron SmartSolar 100/20 MPPT Solar Charge Controller left over from prior build I upgraded dramatically
  • BP Solar 200W solar panels in parallel
  • PV disconnect left over from prior build
  • DC breakers left over from prior build
  • 15A inline fuse left over from first build
  • Victron Cerbo GX MK2 left over from prior project
  • Victron Phoenix 12V 250VA inverter bought today from OfferUp for $30 from guy who got a 3000VA multiplus instead (jealous)
A few things I have learned building my 3rd fully functioning off-grid system today:

1.) The time it took to build the system was 9 hours. That was probably 3 hours faster than my last build. Going back and forth across the property to the tool box and supplies like wires, lugs, crimpers, Y cables and more added probably 90 minutes, but no way to fit it all inside my small shed while designing and building it at the same time. Just could not. I also didn't have a lot of space to work with. System is 15" wide and 36" long. It would take just as long to build a 48V system I believe, or a system with a larger single battery, or a larger Solar charge controller, as the wire gauges would just be larger. If there were more batteries in parallel, then it would have taken longer. I think that even for this small system budgeting 2 work days is reasonable.

2.) Installation is 8' high in the air directly above my shop bench. I can't emphasize how difficult it is to carry an AGM battery up that high and then have to extend my arms to put it there. That was crazy painful. I will use a hoist next time or at least have some method like a stool on top of my bench to bring it up/down in increments. The roof of shop is at 15' so don't worry about air gap.

3.) Being able to turn on and off the inverter remotely in VRM is awesome. Not life changing, but close :-)

4.) What I did not expect at all: The Phoenix inverter has no way to connect to it via Bluetooth. Did not expect that. Glad I had both the VE.Direct to USB dongle that I did not need/use, and already had a Cerbo. Other than upgrading the firmware, haven't done anything to the inverter. Is this correct, or did I get a bad phoenix?

5.) I reset and set the SmartSolar 100/20 battery section to be AGM Spiral Cell, but have NO idea what this is - was looking for an AGM preset. Cleared the history. Any recommendations on how to configure the 'battery' section for this AGM I have?

6.) I reset and set the SmartShunt 500a to be 95Ah...not much else to do there. Cleared the history.

7.) I left the inverter settings to their defaults. Not sure I need to do anything there. Should I be tweaking any settings on the inverter?

8.) On the Cerbo/VRM, I configured DVCC to ensure only 20A go to the battery, so all systems will now talk to each other I believe. Also ensured the shunt was selected, and the temperature was being shared across devices. Anything else I should do in Cerbo GX, or good to go?

9.) The idle consumption on the victron setup is 4W. On my giandel setup is 21W. Victron is awesome. With this little 95Ah AGM, it says battery will be dead in 10 days (9 days 23 hours). With my giandel setup with lifepo4 and it being 200Ah, it says 4 days and 15 hours I'll be dead. That's idle consumption right there.

10.) I built the system with wires big enough to support a larger inverter in the future, and it would be easy to put my DIY 200Ah LiFePO4 battery in the place of this AGM - they are the same size, but 200Ah vs 95Ah. I am likely to do this swap soon.

11.) I am happy I didn't need to install a relay to turn on/off the victron inverter. It has a switch option on it I see, which I believe is for a vehicle ignition or for a button like in an RV so you don't have to go to the phone or have a cerbo GX or a touch display or bluetooth, etc. Any other benefit/purpose for that remote port on the phoenix?

Any tests you have to do to a shake down of this new environment, let me know.
I'm thinking of running a 200W load to see if the battery dies. That should take 4 hours and 45 minutes I believe, but not sure if with AGM it would only be half that (2 hours 22 minutes max).
 
"Hello. My name is Dave, and I'm a solarholic."
Got the bug bad. I have so many alerts set up for 'lifepo4' or 'solar' or 'inverter' or 'mppt' or 'victron' its ridiculous how many alerts I get from offer up and craigslist every day. I browse ebay 5 days a week looking for 'accepts offers' and 'auction' too. Everyone needs a hobby.
 
4.) What I did not expect at all: The Phoenix inverter has no way to connect to it via Bluetooth. Did not expect that. Glad I had both the VE.Direct to USB dongle that I did not need/use, and already had a Cerbo. Other than upgrading the firmware, haven't done anything to the inverter. Is this correct, or did I get a bad phoenix?

No BT on Phoenix.

5.) I reset and set the SmartSolar 100/20 battery section to be AGM Spiral Cell, but have NO idea what this is - was looking for an AGM preset. Cleared the history. Any recommendations on how to configure the 'battery' section for this AGM I have?

Set to battery manufacturer specs.

7.) I left the inverter settings to their defaults. Not sure I need to do anything there. Should I be tweaking any settings on the inverter?

Not really. The defaults work well enough in most cases.

8.) On the Cerbo/VRM, I configured DVCC to ensure only 20A go to the battery, so all systems will now talk to each other I believe. Also ensured the shunt was selected, and the temperature was being shared across devices. Anything else I should do in Cerbo GX, or good to go?

Probably good to go. DVCC can only control chargers interfaced with the GX device, and it's not perfect. Load fluctuation can cause you to exceed limit briefly.

11.) I am happy I didn't need to install a relay to turn on/off the victron inverter. It has a switch option on it I see, which I believe is for a vehicle ignition or for a button like in an RV so you don't have to go to the phone or have a cerbo GX or a touch display or bluetooth, etc. Any other benefit/purpose for that remote port on the phoenix?

The remote port is for signalling on/off.

Any tests you have to do to a shake down of this new environment, let me know. I'm thinking of running a 200W load to see if the battery dies. That should take 4 hours and 45 minutes I believe, but not sure if with AGM it would only be half that (2 hours 22 minutes max).

My favorite way to test lead acid is Reserve Capacity. That's the number of minutes a battery can deliver 25A. For any battery smaller than 500Ah, you aren't going to completely drain it thus minimizing the possibility of damage.
 
Got the bug bad. I have so many alerts set up for 'lifepo4' or 'solar' or 'inverter' or 'mppt' or 'victron' its ridiculous how many alerts I get from offer up and craigslist every day. I browse ebay 5 days a week looking for 'accepts offers' and 'auction' too. Everyone needs a hobby.
Holy crap now I don't feel as bad. I thought I was the only one that has these alerts set up. I came to this forum 6 months ago knowing nothing about electrical/solar stuffs. This forum is a treasure, and its members are infinitely appreciated! Though you'd probably get a different opinion from my wife. I had spent literally over $20,000 (probably closer to $30K) since then on this "hobby" (so I told her) and no sign of stopping any time :(
 
Damn dude. At
Holy crap now I don't feel as bad. I thought I was the only one that has these alerts set up. I came to this forum 6 months ago knowing nothing about electrical/solar stuffs. This forum is a treasure, and its members are infinitely appreciated! Though you'd probably get a different opinion from my wife. I had spent literally over $20,000 (probably closer to $30K) since then on this "hobby" (so I told her) and no sign of stopping any time :(
damn I’m maybe at 4k and it seems like too
Much. I have a huge box of solar only tools, a huge box of solar conductors and lugs, a huge box of romex and 120/240 supplies, and a stack of 15 more panels I’m not even using yet.
 
Got the bug bad. I have so many alerts set up for 'lifepo4' or 'solar' or 'inverter' or 'mppt' or 'victron' its ridiculous how many alerts I get from offer up and craigslist every day. I browse ebay 5 days a week looking for 'accepts offers' and 'auction' too. Everyone needs a hobby.


Put down the crack pipe and step back slowly ... Once you are bitten by the solar bug it is hard to taper off except by going cold turkey on buying stuff.... It starts with deleting your CC# out of ebay and all other websites so you have to put the numbers in again.... Then give the card to your wife so she can go shopping... no, wait,,, that doesn't work either...

OK, turn off all the alerts, if you don't know about it you won't be tempted to buy something ... and the frequency of the alerts should be an indicator that there are always more parts for sale and you might miss todays deal, but you will have more money to spend tomorrow.
 
Put down the crack pipe and step back slowly ... Once you are bitten by the solar bug it is hard to taper off except by going cold turkey on buying stuff.... It starts with deleting your CC# out of ebay and all other websites so you have to put the numbers in again.... Then give the card to your wife so she can go shopping... no, wait,,, that doesn't work either...

OK, turn off all the alerts, if you don't know about it you won't be tempted to buy something ... and the frequency of the alerts should be an indicator that there are always more parts for sale and you might miss todays deal, but you will have more money to spend tomorrow.
Wise advise! Except the crackheads all know they're addicted and should quit, the problem is getting themselves there :fp2While giving the cc to my wife might sound like a good idea (or not), I know I'd just steal it back from her when she's sound asleep :cry:
 
I secretly delete the credit card and log out my wife's ebay account out so I have some relief for a day or so... same with Macy's, overstock, landsend, and at least a dozen other websites.
 
Last edited:
Now that THAT is out of the way...thanks for helping me with my solar addiction @robbob2112 and @sunshine_eggo
I'm doing a shakedown of this third system. Reminder I'm using an AGM battery that I got for free. Here's what I've done:
1.) Charged battery to full float.
2.) Connected to the shunt and set zero current
3.) Left the system with PV off overnight.
4.) Checked readings in the morning, turned on PV disconnect, and let it charge
5.) Not much change, so connected loads
6.) Ran small load of LED bulbs for 8 hours. No issues.
7.) With sun out/PV on, system charged back to high state of charge.
8.) After sun went down completely, ran heavier load at night. Said I had about 90 minutes.
9.) It cut off the Victron inverter several times, due to low battery voltage alarm. I wasn't watching it in real time, but due to reports in VRM, I can see that this is what happened.
10.) Finally, the voltage must have been too low to come back on (or maybe the Victron phoenix inverter has an 'after 10 times, stop trying' or similar setting.
Sun is out and I'm waiting for it to charge.
But I noticed that the shunt's reported state of charge is at or above 60%, and yet, the battery low voltage alarm is still on, presumably due to voltage of 12.47 (12.68 currently).

My guess is that the shunt or the MPPT or the inverter thinks that this 95Ah battery is larger. Or maybe because it is AGM. Or maybe because something is wrong somewhere.

If it is a 200W load, at 12V or so, how long until an AGM 95Ah battery would be at a low SOC/not usable/low voltage?

Could be the settings are bad. Could be the AGM is bad.

Discuss. Fire away questions.

Posted settings below so you can tell me what I'm doing wrong with AGM.


1744653297241.png

1744655920445.png

1744655958003.png
1744656003153.png
1744656098411.png
1744656130200.png
1744656147205.png
1744656232353.png
1744656260086.png

from MPPT

1744656369688.png

expert mode:
1744656409779.png

from shunt:

1744656457503.png

Inverter:

1744656540847.png

So my guess is inverter hit 10V, and is waiting until back at 14V to kick back on? I'm just not sure.

It may be based on what I see above that at 9.3V it gave up completely, but in VRM I don't see that it went that low. I could see 10V.

10.9V restart and alarm? I would think the inverter would be on right now. It is at 12.76.

Charge detect at 14V? I really don't know what that means - it is charging right now at about 4 Amps.
 
Now that THAT is out of the way...thanks for helping me with my solar addiction @robbob2112 and @sunshine_eggo
I'm doing a shakedown of this third system. Reminder I'm using an AGM battery that I got for free. Here's what I've done:
1.) Charged battery to full float.
2.) Connected to the shunt and set zero current
3.) Left the system with PV off overnight.
4.) Checked readings in the morning, turned on PV disconnect, and let it charge
5.) Not much change, so connected loads
6.) Ran small load of LED bulbs for 8 hours. No issues.
7.) With sun out/PV on, system charged back to high state of charge.
8.) After sun went down completely, ran heavier load at night. Said I had about 90 minutes.
9.) It cut off the Victron inverter several times, due to low battery voltage alarm. I wasn't watching it in real time, but due to reports in VRM, I can see that this is what happened.
10.) Finally, the voltage must have been too low to come back on (or maybe the Victron phoenix inverter has an 'after 10 times, stop trying' or similar setting.
Sun is out and I'm waiting for it to charge.
But I noticed that the shunt's reported state of charge is at or above 60%, and yet, the battery low voltage alarm is still on, presumably due to voltage of 12.47 (12.68 currently).

My guess is that the shunt or the MPPT or the inverter thinks that this 95Ah battery is larger. Or maybe because it is AGM. Or maybe because something is wrong somewhere.

If it is a 200W load, at 12V or so, how long until an AGM 95Ah battery would be at a low SOC/not usable/low voltage?

Could be the settings are bad. Could be the AGM is bad.

Discuss. Fire away questions.

Posted settings below so you can tell me what I'm doing wrong with AGM.


View attachment 292231

View attachment 292236

View attachment 292237
View attachment 292238
View attachment 292239
View attachment 292240
View attachment 292241
View attachment 292242
View attachment 292243

from MPPT

View attachment 292245

expert mode:
View attachment 292246

from shunt:

View attachment 292247

Inverter:

View attachment 292248

So my guess is inverter hit 10V, and is waiting until back at 14V to kick back on? I'm just not sure.

It may be based on what I see above that at 9.3V it gave up completely, but in VRM I don't see that it went that low. I could see 10V.

10.9V restart and alarm? I would think the inverter would be on right now. It is at 12.76.

Charge detect at 14V? I really don't know what that means - it is charging right now at about 4 Amps.
Its in the manual:

Screenshot_20250414_150102_Chrome.jpg
 
OK, so I think what you’re saying is is that because it turned on and off three times, I have to manually go out there and turn it off and then turn it back on. I’m OK with that.

But doesn’t the VRM report screenshot that I shared above indicate that it did this maybe 10 times and not three?
 
OK, so I think what you’re saying is is that because it turned on and off three times, I have to manually go out there and turn it off and then turn it back on. I’m OK with that.

But doesn’t the VRM report screenshot that I shared above indicate that it did this maybe 10 times and not three?
It will continue to shutdown and restart until voltage is low enough that it doesnt recover within 30 seconds. It will do three of those cycles then go into a quasi hibernate mode

At that point you need to manually switch it off and on, or let the battery voltage reach the "Charge detect" threshold for 30 seconds at which point it will turn on by itself.
 
It will continue to shutdown and restart until voltage is low enough that it doesnt recover within 30 seconds. It will do three of those cycles then go into a quasi hibernate mode

At that point you need to manually switch it off and on, or let the battery voltage reach the "Charge detect" threshold for 30 seconds at which point it will turn on by itself.
Thank you for explaining this question I had so well.

As you can see from the pictures, the sun came out today and charged it up. It must’ve hit 14 V for 30 seconds because the inverter just turned back on. That is somewhat unexpected behavior. I think that if it shuts all the way down like that, I should have the ability to start it remotely without flipping the switch off and on, correct? I’m not reading what is above and interpreting it that way. Sounds like it must become fully charged. And by fully charged, I guess that means 14 V.

What do you think of all the other questions in settings above?
 

Attachments

  • IMG_6343.png
    IMG_6343.png
    72.6 KB · Views: 0
  • IMG_6344.png
    IMG_6344.png
    162.2 KB · Views: 0
I’ve never seen the Victron low-voltage cutoff abused so well. :)

It’s good to see the VRM charts in action there, thanks for doing that.
 
Well you can drop that down from 14V, it's a setting.

I don't have any experience with lead acid so cant help you with the rest.
I did expect the inverter to cut off. That's fine.
I didn't expect it to come back on and off a dozen times.
Like you, I'm not familiar with lead acid either. But hey...FREE BATTERY :-)
 
I’ve never seen the Victron low-voltage cutoff abused so well. :)

It’s good to see the VRM charts in action there, thanks for doing that.
You're welcome - doing my part :-) Only 100W load or less.
Yeah the victron crew seems to like me posting those charts and settings.
 
The one thing I'm seeing that maybe there's an easy fix (@sunshine_eggo?) is that when looking at the two environments I see that one says 100% SOC at 14.8 volts (AGM), other seems to be full at 13.5 volts (LiFePO4). I say full because there's a ton of sun out right now, but it isn't trying to charge the lifepo4 battery with any amps, and went into its float stage. The AGM one (top) is in absorption and will likely stay there for 6 hours (!) before going to float I think - settings up top. With AGM looks like the discharge floor is 50%, so I will never get more than half the rated capacity (95Ah, so 45 Ah max? Right now it says the discharge was 34.8 last time when I drained the battery and inverter shut off.

1744753511216.png
 
The one thing I'm seeing that maybe there's an easy fix (@sunshine_eggo?) is that when looking at the two environments I see that one says 100% SOC at 14.8 volts (AGM), other seems to be full at 13.5 volts (LiFePO4). I say full because there's a ton of sun out right now, but it isn't trying to charge the lifepo4 battery with any amps, and went into its float stage.

You should be able to observe the LFP charge history and see it attained absorption and dropped to float. If it doesn't need charging, it won't charge it.

What you describe above is very expected, so I'm not sure what the issue is.

The AGM one (top) is in absorption and will likely stay there for 6 hours (!) before going to float I think - settings up top.

You've chosen the adaptive algorithm, so it will select the absorption period based on depth of discharge. If you just lightly discharge it, it might only absorb for an hour or less. 6 hours is the max, and the 1A tail current will also end it.

With AGM looks like the discharge floor is 50%, so I will never get more than half the rated capacity (95Ah, so 45 Ah max? Right now it says the discharge was 34.8 last time when I drained the battery and inverter shut off.

No. discharge floor has no bearing on what you get out of it. It is the value used to compute the "time to go" reported by the shunt, basically: "your battery will last X long before hitting 50% based on your recent usage over the last 3 min."

Your shunt is configured for a system that doesn't use PV charging - only AC charging.
 
You should be able to observe the LFP charge history and see it attained absorption and dropped to float. If it doesn't need charging, it won't charge it.
The LFP did, thanks.
1744779990289.png
The AGM never hit it today.
1744779935393.png

What you describe above is very expected, so I'm not sure what the issue is.
Lost track sorry.
You've chosen the adaptive algorithm, so it will select the absorption period based on depth of discharge. If you just lightly discharge it, it might only absorb for an hour or less. 6 hours is the max, and the 1A tail current will also end it.
Is there something else in the AGM I should be chosing?
No. discharge floor has no bearing on what you get out of it. It is the value used to compute the "time to go" reported by the shunt, basically: "your battery will last X long before hitting 50% based on your recent usage over the last 3 min."
That's right thanks.
Your shunt is configured for a system that doesn't use PV charging - only AC charging.
In the AGM side? What did I do wrong?
Please advise; here's those settings again:
1744780229718.png
 
The LFP did, thanks.
View attachment 292603
The AGM never hit it today.
View attachment 292602


Lost track sorry.

Is there something else in the AGM I should be chosing?

That's right thanks.

In the AGM side? What did I do wrong?
Please advise; here's those settings again:
View attachment 292604

Solar is not as reliable as AC charging. Sporadic solar conditions could result in you meeting the voltage and tail current criteria (> 13.2V, < 4A for 3 minutes) and trigger a premature sync to 100%. When charging with solar, it is best to specify charged current at 0.2V below absorption. You would set it to 14.5V since MPPT is set to 14.7V.
 

diy solar

diy solar
Back
Top