Casita SD17 Lithium Battery Install - Fiberglass RV
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Old 01-04-2021, 07:12 AM   #1
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Name: Bob
Trailer: Casita - 2019 SD17
Idaho
Posts: 93
Casita SD17 Lithium Battery Install

One of the projects for my new 2019 Casita Spirit Deluxe 17 foot RV was to replace the factory intalled 100 AH AGM battery with lithium batteries.

I read and listened to many people on the subject and gleaned what I could from each individual. Like any solution to the problem, there are pro's and con's. There are really only two big negatives about my lithium battery installation. The biggest negative is the cost of the lithium batteries. Sticker price is generally about $1000 for a 100 AH battery. I was fortunte and was able to get two batteries for $1400. Still a big investment. My batteries are rated at 105 AH each.

The second negative of my installation is that it utilizes internal storage space. Casita's battery compartment is not large enough to contain more than one battery. The old battery compartment is now an external storage space for wheel chocks and leveling blocks.

I think my particular solution is the best so far that I am aware of. Once I finally figured out the solution and executed it, it turned out to be quite simple. I spent more time researching the project and figuring out various solutions to problems I encountered. I think you will understand when you see how it went.

I disconnected and removed the factory installed 100 AH deep cycle AGM marine battery from the battery compartment. The negative battery lead was then connected to the positive battery lead by a bolt. Electrical tape was used to insulate everything. (Note: before you have a heart attack, read on) I then covered the terminal with a quart zip-lock bag to further protect it from the elements. All of the wiring in the battery compartment was pushed to one side and out of the way. This action turned the POSITIVE battery lead into a NEGATIVE battery lead for my lithium batteries.

I purchased 10 feet each of 8 guage stranded wire in black and white as 8 guage is what Casita was using for the AGM battery. Black is POSITIVE and white is NEGATIVE/neutral/ground. Approximately 1 foot of each color was cut off the end of the 8 guage wire. Terminal lugs were then fastened on both ends of the 1 foot pieces and the remaining sections of wire. The one foot sections are the jumpers that connect the two batteries in parallel.

The new pair of wires were fed from the wheel well compartment of the side dinette following the trailer's wiring harness back to the battery compartment. This went smoothly.

I removed the POSITIVE (now NEGATIVE) battery lead from the automatic battery reset current circuit breaker mounted inside the trailer on the side of the battery compartment. (See photo.) The POSITIVE (now NEGATIVE) battery lead from the battery compartment was then connected to the NEGATIVE (white) wire coming from the wheel well compartment. The black POSITIVE wire from the wheel well compartment was connected to the automatic battery reset current circuit breaker where the AGM POSITIVE lead had previously been connected.

NOTE: I was unable to find any neutral or ground connections readily available and close to the battery compartment inside the trailer. I would have used the converter/fuse box, however, it can not be removed and reinstalled once it is removed without a lot of effort. It would require removing the hot water heater and more in order to access the mounting bolts. I also made a rule that unless absolutely necessary, I will not drill any new holes to penetrate the shell of the trailer and thus add more potential points where the integrity of the trailer would be compromised. By connecting the positive lead to the negative lead in the battery compartment, I had my new neutral/ground through existing wiring. I hope I don't have you confused. Trust me, it does work out in the end.

The battery tray is made out of Baltic birch plywood in which to secure the two lithium batteries in the side dinnete wheel well storage compartment. Rubber matting was cut to fit the bottom of each battery section in the tray. The rubber matting serves to keep the lithium batteries from sliding around and provides some cushioning from road vibration. The batteries are secured in place with Velcro straps. The compartment floor was cleaned with 91 percent alcohol to remove grit and grease.The new battery tray is fastened to the floor with a industrial strength double stick tape. The photo shows the exact type of tape used.The cable tie in the wheel well area which held all of the wiring and water lines together had to be removed to allow the new battery tray to fit in place.

Wiring completed, batteries installed. Smoke test time. Everything worked as planned. The photos provide a good overview of the installation.

Advantages: Two (2) Lithium batteries weight a total 42 pounds (add 3 pounds for the new battery tray and wiring) vs 71 pounds for the old AGM battery. Available power is approximately 190 amp hours with the two (2) lithium batteries vs 50 amp hours maximum with the AGM battery. The installation allows easy installation and removal of the lithium batteries. Lithium batteries have an 8 to 10 year life or 3 to 5 thousand charge cycles. The AGM battery has approximately a 3 year life and can only be discharged a maximum of 50 percent. The life span helps to even up the cost factor when deciding between the two battery types. Operating temperatures are also a huge advantage to lithium batteries.They have to be above 32 degrees to charge, but can be used to -4 degrees Farienheit and to 115 degrees.

Some final notes. I am using a Zamp 230 watt solar suitcase panel to charge my lithium batteries. I am new with solar and it may be that I will need to add a battery monitor and controller to the system. So far though, this system works like a champ.

I like that my solution was clean and unobtrusive. I swapped internal storage for an almost equivalent external storage area, which to me is quite welcome. I also reduced the dry weight of the trailer in the process while quadrupling battery capacity. The trailer can be easily returned to the factory configuration with little effort.
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Old 01-04-2021, 10:31 AM   #2
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Nice Installation! If you plan on charging from the TV you will need to add a DC-DC isolated power supply.
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Old 01-04-2021, 12:58 PM   #3
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Name: Bob
Trailer: Casita - 2019 SD17
Idaho
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TV charging of Lithium Batteries

Quote:
Originally Posted by CarlD View Post
If you plan on charging from the TV you will need to add a DC-DC isolated power supply.
Carl, would you explain further? According to the documentation that came with the batteries, I theoretically am able to use any normal 12 VDC charging system. The only caveat was that both batteries need to be initially fully charged before being used in parallel.
If I do go for the DC-DC isolated power supply, do you have any recommendations?
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Old 01-04-2021, 01:49 PM   #4
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Name: Bob
Trailer: Casita - 2019 SD17
Idaho
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DC-DC isolated power supply

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Originally Posted by CarlD View Post
I can speak to a Lithium Iron Phosphate (LFP) battery which has a higher voltage than the lead acid battery and will not charge if it is just connected to the house battery, in fact it may discharge into the house battery. A LFP requires about 14.2-14.4 volts to fully charge. To do what you propose you would need a DC-DC isolated power supply to raise the TV or house battery voltage to the proper charge level. Implementing this configuration is not as simple as it sounds, and requires careful selection of wire and connector size from the TV alternator to the Jackery. In a nutshell, I wouldn't do what you are trying to do.
Carl, I quoted you from your post to a different member's lithium battery installation/questions of the same date as mine.
I assume your response to my last post would be similar.

My Zamp solar controller has a setting for lithium batteries. Primarily, I would be using solar to charge. However, considering how the TV/RV are wired through the 7-pin connector, I would expect the TV to be trying to charge the RV batteries while in transit or any time the TV engine is running. I am driving an 2015 GMC Arcadia as the TV. The battery indicator on the TV shows voltages between 8 and 18 VDC. The graduations have little or no relationship to these numbers, but the mid range number is 13. I ASSUME that the charging system of the TV has the capacity to provide the voltage necessary to charge all of the batteries. While the indicator is red lined at the low end and high end, I guess my only concern would be if the TV charging system exceeded the high voltage charge point for the lithium batteries which I believe is 14.5 VDC. In which case some kind of battery monitor/controller would needed to be in the system to prevent excessive voltages to the batteries.
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Old 01-04-2021, 05:05 PM   #5
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Trailer: LiL Hauley
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You can charge the LFP batteries from a lead acid charger, however it will be slower. The LFP batteries can handle .5C charge rate without issues. Your batteries are 105 Ah so you could charge at 105 amps. Charging from the vehicle is an issue because you are essentially paralleling lead acid batteries with the LFP batteries, which have different charge and operating voltages and the long wire run from the alternator will cause an unacceptable voltage to the LFP batteries and many modern alternators drop the voltage after the battery is charged which would probably too low to charge the LFP batteries, and I have run out of ands.

Turning serious again, I have a victron DC-DC isolated converter. It works with input voltages between 8 and 17 VDC. The output is adjustable from 10-15 VDC. Output current is 9 amps. I made a rather lengthy technical description of design considerations in a recent post. Basically, The device can output 14 VDC to your battery at 9 amps. The input can be as low as 8 VDC. Assuming 90% efficiency, if the output is 14X9 watts(126 watts), the input will be 126/.9 watts (140). If the input voltage drops to 8 VDC the input current will be 140/8 amps (17.5). I recommend a 10 awg wire from the engine compartment to the rear of the TV to a dedicated plug and continue with 10 awg to the DC-DC converter. Set the converter to the required output voltage per the battery manufacturers recommendation, (probably 14.2-14.4 VDC). Fuse the wire at the engine compartment at 30 amps. I had a loose connection on my converter which failed after 30,000 miles. I was running it thru the 7 pin connector, which I think did not make a good connection the last time I plugged it in, which caused the voltage to drop and consequently increased the input current, causing the overload and heating at the DC-DC converter input terminal. I am adding a waterproof connector at the rear of the TV. I hope to have all the parts this week.

Link to the DC-DC converter issue
https://www.fiberglassrv.com/forums/...ons-94544.html

DC-DC converter link

https://shop.pkys.com/Victron-Energy...waAj17EALw_wcB
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Old 01-04-2021, 08:46 PM   #6
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Name: Dick
Trailer: '15 17' LD Casita and '17 Tahoe LT
Texas
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I know absolutely nothing about large Lipo batteries but with RC car lipo batteries, they warn you to keep them in a fireproof container because they have been known to burst into flames or explode.
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Old 01-05-2021, 10:14 AM   #7
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Trailer: 1979 Boler B1300
New Hampshire
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Quote:
Originally Posted by dmad1 View Post
I know absolutely nothing about large Lipo batteries but with RC car lipo batteries, they warn you to keep them in a fireproof container because they have been known to burst into flames or explode.
Different chemistries. The RV batteries are Lithium Iron Phosphate. They do not burst into flames or explode. In addition, there are some new RC Lipo batteries coming to market that you can literally drive a spike through and they don't burst into flames unlike the more common RC Lipo batteries. Just very expensive.
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Old 01-09-2021, 09:12 AM   #8
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To elaborate on what Carl said, other folks who have done the conversion have tested the current flow from the TV to the RV while driving and posted the data. This is from my memory but gets the point across: At startup, the TV alternator ran over 14V and simultaneously charged the Li battery in the RV. As the TV starter battery charged up, the alternator voltage dropped. After a few minutes, the alternator output voltage dropped below the Li battery voltage and the RV battery started discharging to the TV battery.

I have not run this experiment myself. But I did what Carl did and installed the Victron DC/DC converter. I set mine to 14.2 volts per the LiFePO4 battery manufacturer. It works great and routinely charges the RV batteries at the rated 9 amps.

As an aside - nice installation and I really like the battery tray. I love it when something is functional and beautiful at the same time.
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Old 01-09-2021, 09:32 AM   #9
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Quote:
Originally Posted by Air Doug View Post
To elaborate on what Carl said, other folks who have done the conversion have tested the current flow from the TV to the RV while driving and posted the data. This is from my memory but gets the point across: At startup, the TV alternator ran over 14V and simultaneously charged the Li battery in the RV. As the TV starter battery charged up, the alternator voltage dropped. After a few minutes, the alternator output voltage dropped below the Li battery voltage and the RV battery started discharging to the TV battery.

I have not run this experiment myself. But I did what Carl did and installed the Victron DC/DC converter. I set mine to 14.2 volts per the LiFePO4 battery manufacturer. It works great and routinely charges the RV batteries at the rated 9 amps.

As an aside - nice installation and I really like the battery tray. I love it when something is functional and beautiful at the same time.
I did the same with my lithium conversion. One point. Since the DC to DC converter is a one way device, be sure you still have power to the breakaway switch, or add the additional wiring that will be necessary to get power to it from the trailer battery.
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Old 01-09-2021, 11:14 AM   #10
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Name: Bob
Trailer: Casita - 2019 SD17
Idaho
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Other options TV charging of Lithium Batteries

A lot of good responses to my post and a lot of food for thought. Thank you.

My own take on the subject after reading everything is as follows:

We all have our own agendas and those drive how we approach different problems based on our specific needs.

In my case, I am very happy with the charging capability of my solar system. I see solar as my number 1 method of charging the house batteries. I have been seriously considering a Honda EU 2200 generator as a backup for overcast days and additional power when needed.

I am not sure charging from the TV is an absolutely necessary option. Particularly if the charging is only going to last for a short period until the main TV battery is fully charged.

With that premise in mind, why not install a simple house battery disconnect when the TV is connected to the RV. I realize this is not an option for those who do not have other means of charging the house batteries in their RV. So they would need to have the DC-DC converter and the break-away switch alternate power.

One question here since the subject of power to the break-away switch was mentioned, what about the RV's electric brakes. Would they not also be affected?

Does activation of the break-away switch assume that all power from the TV is severed as well? With that assumption, then my solution would not work. What happens with the DC-DC converter system in such a scenario? What is the primary power to the RV's braking system? With the DC-DC converter installed, where does the RV's braking system get power? From the RV's house batteries or the TV 12 VDC system? Based on my questions, you will quickly grasp my lack of knowledge how all of this works. I am constantly reminded that I all to frequently ASSUME.

If I understand correctly, control of the RV's exterior road lights and the electric brakes comes from the TV's brake light signal and power. Without the DC-DC converter installed, the power for the lights and brakes are shared with the RV's house batteries. When the DC-DC converter is installed, where exactly is it installed in the system and how does this impact everything? Maybe I am making it more complicated than it need be. Lack of knowledge and understanding on my own part is quite obvious.
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Old 01-09-2021, 11:27 AM   #11
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Quote:
Originally Posted by Bob Penn View Post
A lot of good responses to my post and a lot of food for thought.

My own take on the subject after reading everything is as follows:

We all have our own agendas and those drive how we approach different problems based on our specific needs.

In my case, I am very happy with the charging capability of my solar system. I see solar as my number 1 method of charging the house batteries. I have been seriously considering a Honda EU 2200 generator as a backup for overcast days and additional power when needed.

I am not sure charging from the TV is an absolutely necessary option. Particularly if the charging is only going to last for a short period until the main TV battery is fully charged.

With that premise in mind, why not install a simple house battery disconnect when the TV is connected to the RV. I realize this is not an option for those who do not have other means of charging the house batteries in their RV. So they would need to have the DC-DC converter and the break-away switch alternate power.

One question here since the subject of power to the break-away switch was mentioned, what about the RV's electric brakes. Would they not also be affected?

Does activation of the break-away switch assume that all power from the TV is severed as well? With that assumption, then my solution would not work. What happens with the DC-DC converter system in such a scenario? What is the primary power to the RV's braking system? With the DC-DC converter installed, where does the RV's braking system get power? From the RV's house batteries or the TV 12 VDC system? Based on my questions, you will quickly grasp my lack of knowledge how all of this works. I am constantly reminded that I all to frequently ASSUME.

If I understand correctly, control of the RV's exterior road lights and the electric brakes comes from the TV's brake light signal and power. Without the DC-DC converter installed, the power for the lights and brakes are shared with the RV's house batteries. When the DC-DC converter is installed, where exactly is it installed in the system and how does this impact everything? Maybe I am making it more complicated than it need be. Lack of knowledge and understanding on my own part is quite obvious.
Unless you have a wireless brake controller, the power to the brakes comes from the tow vehicle's brake controller (through pin 2 of your 7 pin connector) under normal driving conditions. When the breakaway switch is activated (ie closed), full power is applied to the brakes from the trailer battery. This is so you will have braking even if the 7 pin connector is removed by the trailer becoming disconnected from the tow vehicle.

Again, the problem arises that the DC to DC converter only allows current from the tow vehicle to the trailer, not the other direction. While this is a desired situation to keep from the lithium batteries attempting to charge the tow vehicle battery, and to prevent drawing too much current for the tow vehicle alternator, if the DC to DC converter is placed on the battery side of the breakaway switch connection, the switch will not be powered by the trailer since it is usually powered by the tow vehicle charge line (pin 4 of the 7 pin connector).

A new connection between the trailer battery & the breakaway switch (and power tongue jack if you have one) is necessary.
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Old 01-09-2021, 11:35 AM   #12
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Trailer: LiL Hauley
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Your break away circuit is activate by a switch connected to a cable, connected to the TV. When a break away occurs the cable pulls out, the switch closes and the trailer house battery will activate the brakes. Some trailers have a dedicated battery for the break away function.

The trailer stop/tail/turn lights have nothing to do with the trailer electrical system and are powered by the corresponding function in the TV.

The DC-DC converter I use has six connections, 2 for an enable function, 2 for power directly from the TV and 2 that connect to the trailer 12 VDC system. The input and output circuits are completely isolated, but become common when you install it because the negative terminals get connected to the chassis.

It is not difficult to install. The 2 input terminals should be wired directly from the TV using dedicated wires. The enable wires are shorted together, and the output connected to the load side of your DC shunt if you have one.
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Old 01-09-2021, 01:19 PM   #13
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Thanks for the detailed write up of the installation of your two LifePo4 batteries. I have a '07 SD 17' and have been thinking of changing out the single SLA battery and installing two LifePo4 batteries with the one being in the original battery compartment and the other in the wheel well storage area. Currently I have the solar charge controller mounted on the divider between the front dinette and the bed area with easy access to wiring, a single 100W solar panel mounted on the roof and a separate plug to run a portable solar panel. The solar charge controller is capable of charging LifePo4 batteries by changing the settings, and had plan to place the second battery in the wheel well storage area. Reading the other comments about DC-to-DC charging seems like a good idea as we tend to move every few days from campsite to campsite and using the tow vehicle to charge the batteries makes sense. I thought if I upgraded to the LifePo4 batteries that I would need to change the power converter since it is not equipped to output the necessary higher voltage for the battery absorption period. Wondering if I can get away with leaving the existing power converter and just add the DC-to-DC converter in the same storage compartment as the second battery and runing a separate power wire from my tow vehicle for charging while driving. When not traveling and the Casita parked at my home I can use a separate portable charger specifically for LifePO4 batteries to keep them charged.
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Old 01-09-2021, 05:30 PM   #14
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Depending on where you live and camp, I think the idea of keeping the Li batteries maintained by solar with generator backup is completely reasonable as you describe your setup. (I won't weigh in on the trailer brake situation as the Lil Snoozy has surge brakes - well, most of them.) If you use the batteries mainly for lighting, not for refrigeration, then that should work fine. You can top balance your Li batteries with solar on a sunny day.

If you have a 12V fridge, like a Truckfridge, I think it would be more of a problem to rely only on solar, but with the generator, you would be fine.

Maybe I missed it and please set me straight if I did, but what is the RV battery charger? Like Carl said, you can charge your Li batteries at .5C if you have a Li compatible charger and have upgraded the wires from the charger to the batteries. The advantage of this is that you can run the generator for much shorter periods of time. For example, in my trailer, I ran 6 gauge wire from the charger to the battery so I can charge at 60 amps. You can't do that with the stock 12 gauge wiring. This is one of the many advantages of Li batteries.
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