I'm 80% completed on converting my 2016 Keystone Cougar 21RBSWE from lead acid to lithium batteries. It has been an adventure! I intend to post pictures of some of the work here and describe what I've done and why. I guarantee many of you will think I'm crazy - this turned out way bigger than I had imagined at the start!

Why did I do this? Well, I've always wanted to improve my battery capacity from the 2 x 100Ah flooded lead acid batteries I have, for longer duration and to add solar capacity beyond the 90W I currently (still) have. Then, last fall, we were out dry camping and our batteries wouldn't run the furnace overnight, or hold a charge long enough to run the lights for more than 30 minutes (LED)! We fired up the Honda generator and charged for an hour, and it still wouldn't keep us warm (temp dropped to 4C that night). Time to put my plans into action! I started designing the system and purchasing components. More on that later.

FULL CONFESSION: prior to getting the new batteries I needed to get some work done (moving a propane line for the water heater to make space for my plans). So, I pulled the old batteries and figured I would try out my smart charger on them and see if I could get enough capacity back to at least run the tongue jack. This is when I discovered why my batteries weren't working - I had never added water to them! They were completely dry to the bottom of the plates. Big forehead smack! And it's not like I don't know this - it's just that I've had "no maintenance" batteries on my vehicles for so long it never occurred to me that my trailer would use the "old" tech batteries, and even though I looked at them several times I failed to connect the presence of removal caps to the need to maintain them... Long story short, I filled them with distilled water, put them on the charger for 3 days, and they seem to have enough capacity to run the tongue jack and who knows how much else. I have no idea how healthy they are now, but at this point I had ordered the lithium batteries and was committed.

The story will continue in further posts.

Original flooded lead acid batteries.

 

I decided on the following: I wanted enough battery to run my coffee maker, and other appliances including microwave, hair dryer/curling iron, toaster through an inverter, but not A/C, water heater, or refrigerator. I won't detail my agonizing calculations, but I settled on 200Ah of lithium battery (which I understand is about double the capacity of 200Ah lead acid since you can run lithium batteries down to a much lower level, around 10%). I selected:

• Renogy LiFePO4 batteries (2 x 100Ah) with internal heaters and BMS, and their bluetooth module
• Renogy 2000W inverter/charger
• Renogy 40A MPPT solar controller and bluetooth module

In the end, I had some other preferred vendors for individual components, but I sacrificed a small amount of cost/size/weight/functionality to get a single integrated system that I can monitor with a single iPhone app. I also decided to defer the solar panel upgrade until all the other stuff was installed.

At this point I also made a (fateful?) decision - I figured that with the layout of my trailer which has the majority of storage ahead of the axles, and the heavy hitch weights I've already been dealing with, I should move the batteries to the rear of the trailer. I had a fairly empty compartment under the closet by the door (photo after I cut out the floor of the boot shelf):

Original compartment below closet and boot shelf.

I planned to get the propane line for the water heater moved to the back of the compartment (where the steel propane pipes ended anyway!), re-plumb everything to save space and make it easier to bypass in winter (and fix an annoying water heater issue - that's for another post), and clean up the wiring to make room for the batteries, inverter, and MPPT. Note: Only lithium batteries could be put inside since they don't generate gas when they are charging - this would not be possible with lead acid batteries.

 

I didn't want to mess with the propane connections, so I took it in to Wild Mountain RV in Calgary and they did a great job moving it behind the water heater. They also added a block under the water heater to level it - turns out that was missed by the manufacturer and caused the front panel to have a bad seal at the top! Thankful we caught that at this point in the project.

Spent a weekend to completely rebuild the water piping behind the water heater. I had planned to move the hot/cold water pipes that enter the basement to make space for the batteries but that didn't happen because every spot was blocked by the black water tank, floor joists, and other structure below the floor. So I changed the angle to minimize the height.

At this point I received the inverter and hit my first real snag. It was a lot bigger than I had planned for! How did that happen? Well, I switched from another vendor's inverter at the last minute and assumed because the box looked similar that it was a similar size. Instead it was probably 25% bigger and 50% heavier! This thing weighs 50 lbs. Switching to LiFePO4 batteries saved me 50 lbs over the lead acid ones, and I just blew that advantage... But back to the size - that meant the inverter no longer fit behind the original breaker panel because the converter section stuck out about 4 " behind the panel (you can see it below the AC wiring in the photo above).

I searched long and hard for smaller AC/DC breaker panels, and in the end I settled on panels by Blue Sea Systems which are usually intended for marine use. These could be installed and use up only about 1.5" of the compartment which worked out in the end.

Designing the breaker panel, I decided that I wanted to separate the "shore power only" AC circuits from the "inverter" AC circuits - I dreaded trying to train family and friends not to turn on the AC or water heater, and remember to make sure the refrigerator was on gas only when we weren't plugged in! I wasn't even sure I could remember that every time... I ended up buying 2 AC panels and 1 DC panel. This is the point where the costs spiralled since these panels ended up costing about $1700.

Spent several weekends and weeknights building:

• a removable panel for the bottom of the boot shelf that I had cut out.
• a battery tray (couldn't find a suitable one online! Needed to be a tight fit to these batteries and they are slightly smaller than the original lead acids). The tray is raised 2" to clear the water lines and provide for cabling underneath, which still leaves several inches on top.
• a mount for the inverter - raised up 2" so I could run all the AC and DC wires underneath it for a cleaner install
• disconnected and removed the original breaker panel
• terminating all the AC & DC wires on terminal strips on the floor so I could run stranded wires to the breakers.
• made a mounting panel for the breaker panels, stained it, then started wiring it up. Wow that's a lot of connections! Also, these breakers use screws and lock washers, so I put ring terminals on every wire. Because with vibration these could loosen up, I made sure to secure every one to an aluminum bracket on the "hinge" side of the panel. Another hiccup - I overtightened one screw on a 30A dual breaker late one night and busted it. Took a week to order a replacement on Amazon. Of course it had to be the most expensive one too.
• did the battery wiring - wow those are @#$%^@#$^ big cables! I needed 2/0 AWG from the batteries to the inverter since it could draw up to 165A/12VDC at 2kW AC load! I bought welding cables (super flexible) and a hammer crimper, carefully measured lengths, and put heat shrink on all of them to minimize exposed metal. 200A breaker next to the battery, cutoff switch, another 60A breaker to the DC panel (6AWG wire - more hammer crimping).

I had to take 3 afternoons off from work, because we had a family camping trip planned and I wasn't going to finish just in evenings! I also did all the work in the RV storage lot we rent out, so I was hauling a generator, all my tools, and gear out there every day. I was out there making the final connections when a big rainstorm came in - I did the first powerup in the rain! Luckily I did everything right since it worked just fine. With only 1 day left I did my cleanup, which was easier because now I could use the AC in the trailer instead of the generator to run the vacuum, heat gun, lights, etc.

Water heater top left, batteries in front of it, inverter on the right. Pretty tight.

Breaker panel from the front at first powerup.

Wiring at the back of the breaker panel. Easily accessible for maintenance by removal of 4 screws.

 

At this point I paused - we were going to be on shore power for the family camping trip (Red Lodge Provincial Park, Alberta) so I wasn't worried that the PWM solar controller (which doesn't support Lithium profiles) wasn't going to provide meaningful charge, and without using the inverter I didn't have to worry about the heat buildup in that compartment. Or so I thought.
We brought the trailer home and plugged it in while we loaded it up. I turned on the inverter/charger to top up the batteries and blew the circuit breaker at my house. Uh oh! By turning everything else off besides the charger I determined that it was charging the batteries at 60A which was a) adding just enough AC current to my extension cord to trip the breaker, and b) heating up the charger quite a bit. I reprogrammed the inverter to max at 30A and everything calmed down. Just over an hour to get the batteries from 80% to 100% and then it was business as usual.
As an aside, I had already recognized the potential problem of heat buildup in the compartment - the install manual for the inverter asked for 6" on all sides in a well-ventilated area! I planned to add ventilation on the right side up inside the wall into the bathroom or closet.

Didn't really exercise the system this trip - ran everything off of shore power. I left the inverter/charger turned off the entire time and we only used about 20% of the battery (for the DC stuff).

On the way back, I found that I could monitor the battery from the truck using the app - pretty good bluetooth range! I was getting about 2.5A to 3A charging from the truck itself, which I wasn't expecting. I had read that modern vehicles often disable their alternators to save fuel and avoid continuously charging the batteries, but that didn't seem to happen while towing.

Once home, I started phase II...

 

To deal with the heat, I cut three 3" holes in the bathroom wall near the ceiling, opening into the same sections of the wall between the joists that I had cut into on the right side of the battery compartment. I figured that the hot air would rise by convection in the wall and exit into the bathroom. And, if I need more cooling, I can turn on the bathroom Fantastic Fan and close the door! I tried this and it pulls a lot of air through those wall vents...

I'm still playing with the fabric covering on the panel next to the breaker panel - I want to block visibility into the battery compartment while letting as much cool air through as possible. I currently have 2 layers of landscaping fabric in there which seems to be blocking the air a bit too much.

I had noticed on our first trip that the breaker switches were too exposed in the entrance - at one point a shoe was jostled and turned off the interior lights! :-) I constructed a plexiglass door to cover the panel. Also, my wife hates how the stain looks on the breaker panel mount, and this covers up quite a bit of it. :-)

Another trip coming up, this time dry camping at Johnston Canyon in Banff National Park for 3 days! I needed to get the MPPT controller working, and I didn't have enough time to put it where I thought it should go. As a hack, I decided to mount the controller in the old battery box, since all the connections were right there! I bypassed the old PWM controller so the solar panels were wired straight to the old battery box, and hooked it up there. Worked well! And, that bluetooth is also viewable from the truck. While driving back from camping this time, I had 5A from the MPPT charging the battery...

And that's where I'm at. Things left to do:

• Move the MPPT indoors - I've selected the closet as the mounting place. The heat sink on the back of the MPPT will be in the same wall cavity that vents the inverter, and it will be out of the way. This is quite difficult to do though - I need to run lots of wire through the basement and up into the battery compartment, and figure out a mounting system that doesn't look awful.
• I figured out that the emergency trailer brakes are now powered somewhat less directly than before - they had a single fuse between the battery and the breakaway switch, but now it runs through my new 200A breaker, the cutoff switch, the 50A DC breaker, and the old cutoff switch! If any of those are intentionally or unintentionally disconnected, no emergency brakes... not acceptable! I will run a positive wire with its own 15A fuse straight from the battery to the front of the trailer.
• I want to add some kind of lightweight plastic shield over the back of the breaker panel since there's 120V exposed if you open it up.
• Next year: upgrade the solar to 400W approximately

I'll update the thread when significant progress has been made. Thanks for reading this far!

Door covering the breakers.

 

Looks great!

 

That 12V panel is very pretty.

 

99% of the gain would have happened by simply replacing the factory batteries with Lithium phosphate ones. I did that with my RV using two 125 Ah rated LiFePO4 ones. The two 100Ah factory batteries provided me with a usable 100 Ah of capacity as I could only take them down to 50% SOD without damage. The two 125Ah LiFePO4 provided me with 250Ah or 2.5 times as much. They also charged much faster so less run time on the generator. The only downside is poorer performance in temperatures below 10 degrees and most have a safety cut-off feature to prevent charging at those temperatures.

 

Yes you are correct - until you add the 2kW inverter. That requires 2/0 cables which are very heavy and expensive so you need to have it right next to the batteries... I've always struggled to reduce hitch weight on this trailer (seems like all storage is in front of the axles) which is why I wanted to move the batteries to the back. And so the long story began.

In retrospect I should have just left it all in the front and moved something else to the back.

 

Nice, we love our LiFePO4's!