Battery Project - Part 1

Monday - Now starts the planning process for the battery installation. Since the battery bay is an uninsulated compartment, I will be building an insulated box for them. 

The bottom of the battery bay is sturdy metal and Home Depot has 1” rigid insulation in 2’x2’ pieces. I think that’ll work for the bottom of the box. A piece of 1/2” plywood will distribute the load onto the foam. The box itself will simply be 1/2” plywood with 1/2” insulation inside with the same construction for the top. 

I’ve identified most of the cables shown in the first picture and I want to relocate a couple of them that will be hard to access once the box is in place. The large, cylindrical relay on the right will be removed and replaced with a DC-DC charger. This relay is energized when the engine is running to allow the engine alternator to charge the coach batteries. The alternator is rated at 160amps and the DC-DC charger will limit the current to 40amps. The internal resistance of LiFePO4 batteries is very low and it will max out the alternator (burning it out) and possibly exceed the max charge rate of the batteries (70 amps each). The other purpose of the relay is to “jump” the chassis batteries in case they are dead. 

Wednesday - The batteries arrived already, three days before they promised. I checked the voltage on them and they are both partially charged. The batteries also have Bluetooth built into the BMS (Battery Management System) so I can see the individual cell voltages and the internal temperature. This is an unexpected feature. The next screenshot shows how the battery shows up on the phone screen.

At the top of the screen is the SOC (State of Charge) but it won't reflect reality until after a couple of complete charges. There is a switch for heating but I didn’t get that option. At the bottom are the individual cell voltages. Pretty cool! 

The first task was removing the old batteries and wiring them back up to the RV so we still have 12V functionality. Another RVer here in the park loaned me a set of jumper cables so I could temporarily power the RV off of the old batteries. The battery bay has a lot of rust on the bottom where the flooded lead acid batteries were sitting so I'm going to paint the floor before starting to build the battery box. The rust is just on the surface and the Rustoleum paint that I already have says to just remove the loose rust and clean with soap and water. This afternoon, picked up a drill mounted wire brush and used that do get rid of as much of the surface rust as I can. Tomorrow, paint. 

Another Potential Issue

Friday - An observation that I made yesterday evening after getting an alert from the Victron battery monitor yesterday morning. The alert was for battery voltage dropping below 12VDC on the morning of Nov 24. 

This chart indicates that 12VDC is around 50% charge which is about as low as you want to go when using lead acid batteries. At this point, we had only used about 120AH of the 420AH of capacity. This is the capacity when the batteries were still new. 

I adjusted the battery capacity on the battery monitor to only 210AH, turned off the charging function on the inverter, and we’ll keep an eye on it. The batteries are still working and we do have a generator so it’s not anything critical. Especially since we don’t dry camp a lot.

In the middle of the afternoon, I’m trying to figure out what is drawing 228watts. The refrigerator plus fans are drawing about 80-100watts. The inverter is off and the basement fridge is on shore power. Maybe the two fans are drawing about 80 watts between the pair. All more than I thought. 

Saturday - Early this morning, I checked the SOC (state of charge) and the battery voltage and adjusted the battery bank capacity to match what I was seeing. The battery voltage was still around 12.25VDC so I raised the capacity to 265AH. This raised the SOC to 62% which matches the chart shown above.

I think that our batteries were discharged to almost zero when it was in the shop. Initially, I had the batteries disconnected but the shop needed them on to operate the slides and steps. They were left on for weeks while waiting for parts and when I picked the RV up, the coach batteries were almost completely dead. We may be replacing batteries next month as we won't be able to make it through the night if we need to use the furnace.

A morning project was making this little steering wheel table from wood left over from other projects. The steering wheel is tilted up right now. Some people like driving it the RV with the wheel almost horizontal as it gives them more leverage. I prefer it down at a more familiar angle. 

Sunday - It’s looking like we will be ordering some batteries in the near future. Even without using the propane furnace, our batteries are already dipping down to 60%. 

I’m pretty convinced to get two of the 206AH, 12V SOK batteries without the internal heaters and BT. They are slightly larger and a couple of inches taller than the each of the four existing 6V golf cart batteries. They have a maximum continuous discharge rate of 100amps each so if we upgrade to a 3K inverter, we will need to add a 3rd battery. I am planning to install them in a homemade insulated box in the battery compartment. I can make my own silicone heat pad temperature control with a small WiFi enabled microprocessor. 

I need to also order a DC-DC charger for engine charging. The existing cables are adequate but I’ll need some jumper cables to allow me to remove the existing batteries from the compartment and still have the coach powered up. 

The old Magnum inverter/charger doesn’t have a LiFePO4 charge profile but the solar charge controller does. The Magnum can charge the batteries to ~80% SOC and the solar can top them off if needed. I had originally thought that I needed to change out the inverter/charger first but this should work fine. 

Happy Thanksgiving!

Thursday - Turkey day! I have a turkey breast in the sous vide, dressing in the convection oven, gravy simmering on the stove, whole berry cranberry sauce and a pumpkin pie in the refrigerator. We will be sharing Thanksgiving dinner with Lynne and Jerry in a couple of hours. 

Later - Dinner was wonderful! Everything turned out great and the company was great. After resting from the post-thanksgiving doldrums, I headed to the jacuzzi. It was around 8pm or so. Much later than usual but it felt fantastic with the air temperature in the low 50s (°F).

No RV Projects

Sunday - No RV projects today for a change. This afternoon, we joined Jerry & Lynne, and Kathy & Mike at Borderlands Brewing Company. The live music and the great company made for a great afternoon. 

Monday - I finally started a non-RV project late last night and didn't finish it until this morning. My Macbook Pro is a 2016 model with 16GB of memory and a 1TB internal drive. It is a 3.3GHz dual-core I7 so as far as performance goes, it's more than adequate for what I do. But, it is considered by Apple to be too old to automatically upgrade the operating system. I followed instructions I found online to upgrade it to the latest OS, macOS 13.01 aka Ventura. It took quite a while but finally finished this morning. I could barely read the screen as the default resolution was set so high. The text on the screen was tiny. I found the post-install patches which corrected the screen resolution and all seems to be working properly. Given that I only seem to use the laptop for Zoom, Discord, email, and web browsing, my needs are pretty minimal. 

I led one of the afternoon test sessions. That would be the normal use for the laptop. Even though it's only a 13" screen, it's still better to try to participate using the phone. No problems at all with any of the applications or tethering with the iPhone.

Tuesday - Scattered clouds today during the morning test session. But still nice enough to sit outside. We are testing a full-time RVer currently in Livingston, TX. 

I then walked to Sprouts to pick up some vegetable stock to brine the turkey breast overnight. I cut off the meaty portions and have the rest in a small stock pot for broth for both the dressing and gravy. Tomorrow afternoon, it’ll get vacuum sealed and put in the sous vide. Later today, I'll make the cranberry sauce now that whole cranberries are available. I enjoy cooking for the holidays...

Wednesday - This morning, Kathy took us to Catalina State Park to do a bit of hiking. The first one was a loop trail through a small valley. Lots of saguaro and views of the nearby hills. No wildlife but lots of sand. 

The fall colors are still out here in Arizona. The leaves are still changing and hadn’t fallen yet. There were still lots of burned areas from the 2020 brush fire. 

And, the required selfie from the trail.