Old Box Trailer security

[ASmarterHome]

Hey All, Thanks in advance!

I've installed a small system to power 3 security lights, 3 IP cameras, network switch and access point into an old box trailer. One item we had to work around is the battery selection. We have batteries from school buses as our storage, they're free and can have as many as we need. I didn't know how to calculate storage capacity on these so I designed the system with 6 guessing that would be overkill and thought it could run the system for 3 days without sun. The panels are 175w x 6 in a 3x2 array wired to a Victron 150/70 MPPT charger. The network and IP cameras run 24/7 and the security lights 210w are dusk till dawn. Installed April 2020. Everything has been well except for the last week, the inverter shuts down at 2am, everyday. It stays off for an hour or so and comes back on for 10 min, off hour, on 10 min, etc until dawn. Then it stays on. I haven't been on site at that time and I don't have remote monitoring set up yet. By the time I get there at 10 am the battery voltage is at 12.4-12.6. One thing I do know, the panels are flat on the roof and it's in a very dirty environment. Looking for some basic input as to system design and expected capacity/run time.

Example of batteries

 

[gnubie]

What sort of condition are those batteries in, ie why did they get removed from the buses? They may be nice big heavy batteries but their capacity may have fallen to a 10th of what the size would otherwise suggest. Remember, cranking batteries are not storage batteries. They are great for repeated short high current whacks to turn an engine over. They die if you place a continuous load on them and draw them down.

It really sounds like your battery is discharging down to the inverter cut off, then when the inverter cuts the battery voltage floats back up which is normal, then the inverter turns back on, and pulls the voltage down again. Rinse and repeat as necessary.

You have a Victron charger there. It can monitor the battery voltage for you. If it's a bluetooth model you can connect to it with the victron app and a smartphone. You may be able to see a graph of the battery voltage at the time the inverter is turning off / on and that would confirm if the battery voltage is falling too low.

 

[chrisski]

I am designing my first system, so take what I have with a grain of salt.

I think you may not be charging the batteries enough, but it’s important you get a spec of the battery.

I have 440 AH of batteries at 12 volts, which appears to be the size of two of your batteries. It takes 44 amps to charge those and my charge controller should give me 40 amps, so close enough. I have 600 watts of panels to deliver this and you’ve got about 1000 watts of panels which probably can provide you with 70 amps. If I’m correct on the battery size, it may take 120 amps to charge them.

The days are also getting shorter, but not April short.

The third and most likely thing as mentioned above, your bus batteries are Made of Thinner lead plates to giv bursts of energy and are not designed to be continously depleted, so this has damaged the cells enough they can’t charge as much.

For around $10, you can go to an auto parts store and get a hydrometer and measure each of those cells in each battery. Not only are you looking to make sure each cell is charged, but that cells are reasonably close to eachother. THe hydrometer is the most accurate way to measure battery health, but is time consuming. If the cells are not equal, you can equalize them.

Honestly though, Not sure how you’d do that. Another site talks about equalizing for up to 24 hours, but the sun does not cooperate with that. I thought it was as simple as getting a battery charger, but after purchasing two battery chargers, each had its own pre-programmed algorithm Which I had no control over. My battery manufacturer lists an equalization voltage, but of course the pre-programmed algorithm won’t use that or automatically turns it on. A charge controller can be programmed, but them again, you need to have sun to equalize, and there may not be enough production hours in the day for that. A serious equalization can mean going out with a hydrometer every hour until its done. How people keep a charger in equlizatin mode until Complete without the charger going back to its automatic algorithm, I don’t know. I’m not sure what charger to use, but would like to see a 110 VAC 40 amp manual battery charger, but could not find it.

With the Bluetooth, not all VIctron’s come with bluetooth, and I think the “SMART” ones have it, and the others have it available with an add on module. This should give you a pretty steady data day by day.

I’d also be curious what The wires size and amperage would look like going though a DC calculator.

What is the black box? Looks like a busbar and somehow connects your batteries in parallel.

My inverter has instructions to not mount vertically with the fan straight up or straight down. The instructions mentions this prevent something from going in the vents on the front or going through the fan in the rear.

 

[ASmarterHome]

Hydrometer is a great idea, I do have one and I’ll test all cells. This afternoon we shut down the lights and I’ll see if it shuts down tonight.

My monitoring at this point is just the connectivity of the switch and cameras. I do have other cameras that point to this location and can see the lights on or off with a time stamp.
The charger is a blue solar model without Bluetooth but that’s ok as now I’m forced to go either raspberry pi or the IOT module. I’m leaning towards pi as I could simply use 1 more battery with a small simple solar panel to keep that on its own power source. The question I have is, will the pi keep logs of all monitored parameters if it loses internet connection?

 

[gnubie]

You are going to load Victron's Venus OS onto the pi? It will store data on the pi's SD card or a USB stick for as long as you want AFAIK.