Since we owned our Serenity, I have wanted to upgrade the electrical system to allow us to go off grid for at least a week without the worry of our batteries running out. We get along with our current arrangement, but after more than two days, we need to be thinking about recharging.
To do this I need to go to Lithium batteries which changes everything in the electrical system.
How much battery capacity is enough? I initially set my target at 300Ah. Based on what I have read, the average RVer will use between 50 and 100Ah per day. 300Ah should allow for 3 to 6 days of boondocking. If you have solar, and are willing to park in the sun, this can be extended. Most of the time, after 3 or 4 days our tanks are full, we need to dump and that becomes the limiting factor for how long we can stay out. So my target was set at 300Ah minimum, if I can fit more, I will take it, but it is just moving the problem to septic management :-).
I plan to upgrade my inverter from 1200W to 3000W, invert all outlets in the RV and add a second battery charger, (DC to DC) that charges directly off the Alternator. There is no question that this is a complete rip up and redo of the 12V electrical system and it could have been done by just adding Lithium batteries with minor changes in the charger that would extend the useful Ah significantly, but it would not take full advantage of the Lithium capacity, I have the time this winter and it is a fun project.
For the last few weeks I have been getting better educated on RV electrical systems. The internet is full of information but it can be overwhelming. After lots of looking I have found that two sources of information are the most useful for me, the Explorist Life and Sandra Johnson. The Explorist Life (https://explorist.life/) teaches people how to build DIY Campers. Sandra Johnson puts out lots of youtube videos and howtos that are specific to the Leisure Travel Van product line. Sandra posts links to her videos and PDFs in the Leisure Travel Vans Enthusiasts group in FaceBook (https://www.facebook.com/groups/ltvrv). I am also shameless about asking anyone I know for help if I think they have knowledge about doing this that is helpful.
With the help of these resources, I have drawn and redrawn electrical diagrams, sometimes getting more confusion than clarity. Unfortunately, my RV is built so I need to work within the confines of what is there, which makes if very challenging. I started by just listing what I wanted and pricing out the components, but quickly realized that you can't always afford what you want. Just the battery for the system I wanted was $5k, I think not at this time. I am trying to plan for future improvements, for example I am planning for a pretty big battery footprint so if I did want to upgrade batteries later, there is a good chance I could fit them. I am also not touching my solar at this time. I only have 200W of suboptimum panels on the roof, but I am upgrading my solar controller to handle more in the future.
Many of my friends have heard me express my opinion that solar is over rated since I seldom park in the sun. I do find it useful for keeping things topped off when we have to leave your RV parked and are not using it, say in a friend's driveway, which we sometimes do. I also recognize that if you can get enough solar, it can help when you are driving. With 600W (which is my future goal) of solar you could be adding 40 to 50 Amps of additional charge to your batteries while driving. This is more than many DC to DC chargers, so it would essentially 1/2 your driving charge time. For example if you had 300Ah battery that was 2/3 discharged, with just the a 30A DC-DC charger it would take over 6 hrs of driving to fully recharge (200Ah/30A). A 600W solar array would cut this in half. For the Serenity, I don't see an easy path to 600W today, so I am waiting for future solar panel innovation before I upgrade the solar.
After many starts, stops, and changes in course, which I will skip, I think I have settled on a design that I can implement. It is Version 5 but hopefully it is 90% correct now.
This is a schematic, Link to Schematic PDF
I have the components listed and priced, there will be lots of other stuff to be added like wire, connectors etc. When I finish the project, I will tally up the total expense, there is no way to tally up the hours, I am already over budget on time :-).
The batteries are Epoch brand, I believe I can get two of these into the storage compartment behind the drivers seat.
I removed the partition and the old Inverter to make more room. I am losing storage but I plan to convert the old battery compartment to useful storage.
The compartment is an odd shape, one Epoch will go in easy, two will take some modification of the battery. The battery is only 13.6" in length at the bottom but 15.4" at the top due to the handles. The compartment narrows from just over 15" to a bit over 14" at the end near the driver's seat. I think I can shave the handles off with a mini grinder and make one of the batteries slide into that space.
I called Epoch and talked to them about this and they confirmed that the handles are just plastic and could be removed to fit in a tighter space. That is my plan.
The plan is to remove the handles (circled in red) on one of the batteries.
I looked at several 3000W inverters. I built cardboard boxes in the shape of the Kisae and the Xantrex inverters. I briefly looked at the Victron 3000W inverter, but it is just too large. I have settled on the Xantrex because it is the most compact, has a good reputation and is recommend by other LTV owners. I believe it will fit in the same compartment with the batteries. This is a ventilated compartment, but will required some modifications to improve the ventilation.
This is the arrangement in the Battery/Inverter Compartment. This is a top down view.
Looking from outside into the compartment. The battery to the left will have the handles shaved and is out of view when looking into the compartment.
This compartment is below the dinette seat where many of the other electrical components are located.
I hope to be able rearrange this compartment and locate some of the other components in here. Others have used this by moving the components down and adding a false floor.
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