M116A3 Build

[bdosborn]

I was wondering the other day if you'd put your trailer in the winter configuration. Looks like you did, those are nice results.

Bruce
P.S. I'm running my annual 80% discharge test on the trailer LiFePo4 battery now, I'll post the results....

[lfhoward]

I was wondering the other day if you'd put your trailer in the winter configuration. Looks like you did, those are nice results.

Bruce
P.S. I'm running my annual 80% discharge test on the trailer LiFePo4 battery now, I'll post the results....

The 80% discharge test results will be interesting. Are you doing it out of curiosity, or is it good for the battery chemistry to get a good discharge and charge-up at least once a year?

The winter configuration works well enough to keep the Raspberry Pi computers running 24/7 as long as it’s facing south and has good access to the sky. My wife and I have decided that we need to double the solar on the trailer roof to be able to be self sufficient for winter camping though. There is room for two more 100 watt panels up there as long as we lose the 10” tall rain cover for the fantastic fan. It casts pretty big shadows that would hobble a larger system.

I’ve been working on prepping the trailer for its second battery, and so I disconnected the serial cable from the first battery’s BMS and plugged its Bluetooth dongle back in. I figured out how to get the Overkill Solar (Llt-Jbd) BMS to talk to to my Victron system wirelessly and report to the VRM. I have a Bluetooth dongle for the second BMS (same style) and plan to get that one connected wirelessly to the VRM too. That way I can look to the BMV-712 Battery monitor for the overall power picture, or pull up statistics on either battery separately via the individual BMS’s. In the way I have the wiring configured in my head, I will be able to turn off either battery independently without cutting power to the whole system. This will be helpful if I ever have to pull one of them to work on it, or to top balance it again.



Tonight I’m top balancing the 90 amp hour battery again, while I’m making new bus bars for it out of copper I had left over from the first 156 amp hour battery project.


I also installed the beehive heating pad in its wooden battery box.


I am hoping to get this second battery installed and wired up in the trailer sometime over winter break.

[featherliteCT1]

Lfhoward,

Very cool second battery build! I love the parallel redundancy you are building into your system.

I just recently figured out how to make my Rpi 4 to run like a Cerbo GX and was able to figure out how to add the soft shutdown feature to the Venus software. Now, I can drive my truck with my iPhone and/or MacBook laptop inside the cab and wirelessly monitor my batteries inside the trailer while I drive down the road. It works great.

Do you know if it is possible to make a backup copy of the SD card running the Venus software in a Rpi 4?

I want a backup SD card in case my original SD card gets corrupted or otherwise fails.

Thank you for posting your progress!

[lfhoward]

Hi Featherlite!

I agree, having a backup will save all our hard work down the line. Since SD cards are flash memory, they are bound to fail at some point.

The method I have been using comes from here:
https://beebom.com/how-clone-raspberry-pi-sd-card-windows-linux-macos/

In that method, you can take the SD card out of the pi, plug it into an adapter, and then into your home computer. The article walks you through the terminal commands to type to create a disk image file on your computer’s hard drive. Going the other direction, re-imaging an SD card with your saved copy, is easy with Balena Etcher.

I am interested in being able to make copies directly from the Pi onto another SD card without having to unplug anything and without needing a separate computer. This software package works great on Ubuntu and I’ve used RPi-clone quite a bit with my non-Victron Pi’s:
https://github.com/billw2/rpi-clone

The advantage to the RPi-clone method is that the resulting file/image is only as large as the written portion of the SD card, whereas in the first method if you have a 128 GB card, the file will take up that much room on your hard drive too. It is super easy and much faster as well. I have used the Rpi-clone program to restore my Ubuntu system after a bad install, and it worked flawlessly.

The biggest potential issue is that the Venus OS doesn’t natively support the Git command to download RPi-clone. I have gotten as far as downloading Git (I didn’t save the link and instructions, shoot… but I think it may have been from here: https://community.victronenergy.com/questions/240905/how-can-i-install-git-in-venus-os-large.html) and installing Git on the Venus Pi. I also was able to download RPi-clone on the Venus Pi, but needed to create a couple of missing folders that it was expecting to see in a regular OS to install without errors.I have not yet tried to make a clone of my Venus SD card using RPi-clone, because I need a second card to put it on. Just need to pick one up. (I do have a backup on my home computer though.). A usb thumb drive can work as well for the backup copy, if you have one.

When you update the Venus OS to the next version, all of your changes (installing Git and RPi-clone) will be overwritten, but you will still have your backup image you made on another SD card, which you can swap in and it will run without having to do anything else.

Hope this helps!

[bdosborn]

The 80% discharge test results will be interesting. Are you doing it out of curiosity, or is it good for the battery chemistry to get a good discharge and charge-up at least once a year?

I do the 80% discharge test to track my battery health, I don't know if its good or bad for the battery chemistry. The trailer battery is plugged into shore power 24/7 at 100% SOC and floated at ~13.5V. It has been for three years now. According to the "internet experts" my battery should be trashed from being floated continuously but I don't see any difference in the SOC vs voltage curve for the test this week and the first test I ran. So I'm going to continue to leave my trailer plugged in and not worry about the battery being in float. At least till next year when I'll test it again...

Bruce

[featherliteCT1]

Lfhoward,

Thank you for taking all the time to post all of that valuable information about how to clone an SD card.

The cloning article you provided says when inputting terminal commands:

“Be careful, … entering the wrong parameters here can … destroy the data on your drives.”

Scary stuff to a Rpi noob like me! LOL!

[lfhoward]

I saw that warning too, and you’d better believe I checked the syntax at least 3 times before hitting the Enter button!!

Today I finished top balancing the new battery again (for longer this time, hoping for better results). Then I got it assembled in its near final form.



I got my copper bus bars fabricated, and improved the contacts.



The batteries came with anemic little screws and thin bus bars. I replaced those with 5/16 studs that thread into the original holes. My copper bus bars are 1/8” thick.



The new battery studs still have to be treated with care, but I think they will work much better than the screws and will protect the threads in the terminals from getting stripped out.



The delta between cells is really good now. It was 0.011 at 3.65 volts per cell (14.6 V), 0.005 at 3.45 volts per cell (13.8 V, my charge voltage), and 0.002 at 3.35 volts per cell (13.4 V, my float voltage). That is comparable to my first battery.



Quick question for those who have built one of these. Do you loc-tite your battery studs into the terminals or no? I am finding conflicting opinions online about whether this is necessary or advisable.

[Tom&Shelly]

Quick question for those who have built one of these. Do you loc-tite your battery studs into the terminals or no? I am finding conflicting opinions online about whether this is necessary or advisable.

I haven't built one of course, but this raises the question for me: Is there a conductive Loctite? Maybe that doesn't matter?

Tom

[lfhoward]

Quick question for those who have built one of these. Do you loc-tite your battery studs into the terminals or no? I am finding conflicting opinions online about whether this is necessary or advisable.

I haven't built one of course, but this raises the question for me: Is there a conductive Loctite? Maybe that doesn't matter?

Tom

I would think that would be helpful, but the nut on the stud is holding the bus bar against the flat upper surface of the battery terminal, so... I don't know how much of a difference that makes. It probably does to some degree.

I haven't gone ahead and used any thread locker yet because of this exact question. The other side of it is, will the vibration of going down the road loosen the battery studs over time. I am thinking not likely with the serrated flange nuts I chose.

[featherliteCT1]

My Lifepo4 cells are the LF280K type, with the double holes on each post, with extra-long stainless steel studs. The studs have an Allen head on top so I can hold the stud with an Allen wrench while turning the stainless nut.

I used blue Loctite on the studs in case I ever needed to remove the studs. I also first applied Loctite primer to increase the effectiveness. I did not use Loctite on the nuts because the nuts are removed periodically. I used stainless split, lock washers under the nuts.

Periodically, I check the studs and nuts and none have loosened. It could be catastrophic if any wires come loose. I was concerned about both the studs and the nuts coming loose. Consequently, the serrated nuts would not affect whether the studs themselves come loose.

I researched the question about whether Loctite would impair conductivity and determined that there is no concern. Tests show that very little current passes through the stud itself. Rather, the current passes directly from the wire lug to the flat mating surface of the clamping area of the cell post. My understanding is that the key to minimizing resistance is clamping force and a clean, smooth surface with no oxidation.

You battery build looks so clean and tidy. I love it!

[bdosborn]

Periodically, I check the studs and nuts and none have loosened. It could be catastrophic if any wires come loose. I was concerned about both the studs and the nuts coming loose. Consequently, the serrated nuts would not affect whether the studs themselves come loose.

That's a good tip, I checked all the bolts in my electrical system after about 6 months of use and found more loose ones than I liked. I use lock washers on everything (as a result of owning an old jeep) and they still loosened up. Checking studs and nuts is now on my spring wake up list.
Bruce

[lfhoward]

I think you have both convinced me to use blue (medium strength) thread locker on the battery studs where they screw into the terminals. I also want to check on the tightness of all the bolts on my other battery! It uses serrated flange bolts. I could potentially convert to studs and flange nuts at some point, which is less likely to damage the threads of the terminals as the battery cables get disconnected and reconnected.

[foxontherun]

Re: M116A3 Build
Postby lfhoward » Sun Dec 17, 2023 8:04 pm

The batteries came with anemic little screws and thin bus bars. I replaced those with 5/16 studs that thread into the original holes.

Good evening,
I have never seen bolts like these before, what are they called? Looks like they would be useful for my batteries I am getting ready to install.

Thanks,
Harry

[lfhoward]

I found a deal on Facebook Marketplace I couldn’t pass up!



They are the older 18.6 volt 100 watt Renogy panels, but they will work great in series-parallel configuration with my two 17.6 volt 100 watt Renogy suitcase solar panels.

The rigid panels:


The folding suitcase panels:


This Victron MPPT charge controller will do the job nicely:



Rigid panels in series:
Vmp 37.2 volts (doubled)
Imp 5.38 amps (same)

Suitcase panels in series:
Vmp 35.2 volts (doubled)
Imp 6.10 amps (same)

Then both sets in parallel:
Vmp 35.2 volts (lowest common denominator)
Imp 11.48 amps (added together)

35.2 x 11.48 = 404 watts. Nice!
I will need to fabricate some legs for those rigid panels to prop them up at a good angle while camping.

[lfhoward]

Re: M116A3 Build
Postby lfhoward » Sun Dec 17, 2023 8:04 pm

The batteries came with anemic little screws and thin bus bars. I replaced those with 5/16 studs that thread into the original holes.

Good evening,
I have never seen bolts like these before, what are they called? Looks like they would be useful for my batteries I am getting ready to install.

Thanks,
Harry

Hi Harry, here is the link to where I found those battery stud adapters:

PATIKIL M4x0.7 to M8x1.25 Double End Threaded Stud Screw Bolt, 10 Pack 304 Stainless Steel Rod Bolts Thread Reducer Adapter for Furniture Hardware, 16mm Long
https://a.co/d/fvSbwxx

Cheers,
Lauren