The lithium installation was both difficult and confusing for an apprentice level electrical guy. We thought we were purchasing an established product but turned out to be the first of our type. Goodwill on both sides and curiosity made for a much better end result than might have been possible if they had been working with an experienced client.
I purchased AM Solar's Essential system with two 200Ah Victron Batteries. Lithium Battery Banks (http://amsolar.com/rv-solar-panel-kit/lithium-battery-banks) . When we purchased the kit we expected to have an installation manual. It had not been finished. We were also the first to have the boost circuit and the possible ground issues with starting the generator. Many of the issues we worked through are now incorporated into the installation guide for the system. For examples of the schematics you would be working with go to this page 320Ah Essential Lithium Battery Bank (http://amsolar.com/rv-lithium-battery-banks/40s-vt-320-ess)
Note the heart of the system is the BMS 200. If you go this route, study its capabilities closely. When we purchased the system in September, the understood limit of the draw was 200A period and later the 10 second surge for 400 was discovered. This is important if you want to continue to use a 400A system as a starting bank for the gen set. My 8k Powertech draws 300-400 initially and drops to 90.
Also note the capabilities of the Orion DC. Again at the time of purchase the information available was the boost would be limited to the 30A output of the Orion. The new schematic cited above opens that up considerably.
Where to locate the system?
Unsure of what this would turn out to be I elected to use the existing battery bay. We removed the old batteries and found considerable corrosion etc from being in a caustic environment. We then cut a ½ plywood piece to fit the rear bulkhead and made it the primary location for the solar controller, inverter path, shunt and switching. We arranged the components on the sheet and began the process of wiring. Early on it was obvious we needed to install bus bars and not lugs.
Keep in mind when you look at the pictures there are only two lithium specific components. The BMS 200 and the Orion DC. However it is unimaginable that you would purchase this system without also purchasing the BV 702 with shunt. I will cover this more in the panel discussion.
Work a rounds with initial instructions some of which are no longer necessary depending on your use.
Caveat Emptor! Please be aware I am a novice and so some of the things I/we came up with may not have been necessary in the end or you may take issue with. I am all ears if you see something that should be changed for the health of the system.
Gen set start up. I decided for multiple uses to run a 2/0 cable from the engine bank to a lug for the generator existing positive. Initially I was concerned with drawing higher amps from the BMS 200. We also placed a three way switch in the electrical compartment to allow both generator starting from the engine bank and the 8.3 starting from the lithium if necessary. The 400A set can surge to 800 and of course if we add the third to 1200. Or engage all for starting either. The side by side switch on the back wall crates a ground that does not flow through the BMS and therefore is capable of higher amperage. I do not think this will be necessary but it is available. My thoughts are that this creates a much larger boost circuit not limited to the 100amps currently used.
Compartment Environmental Issues
Lithium needs to be kept above 32f while charging. And should be kept below 110. At first this seems to dictate placing them inside the coach if possible. I disagree. The operative word for low temperatures is charging. During the last month we tested the temperatures in the coach. (see the temp monitor at the back between the switches) We ran the coach on propane heat at 65 and measured the compartment. The lowest we had was 45 in 25 degree weather. I installed a 110 box in the compartment for this and other reasons and attached a tempcube with a 200w personal heater as a back up. We have never been close to freezing. Further, and perhaps most importantly, we will not be charging at night in the boondocks unless the gen set is on or in a campground not hooked up. No source to charge from with the exception of watching solar in the AM with an unheated coach.
That leaves heat. I am concerned with the heat from asphalt. Again we will monitor the ranges we experience and have several ideas on how to keep it cool. If the temperature range cannot be controlled with fans etc. I plan on cutting a hole under the sofa and drawing cool air into the compartment. I do not agree with giving up space inside the coach.
The batteries fit nicely into the existing tray. Plenty of room for two more but I cant imagine that much usage. We used the foam from the packaging to keep them in place as they are three inches shorter.
Finally, I wanted the compartment to also have a small bus bar which is installed just above the other bus bars. New circuits have been added here and will be used in the future.
NOTE: The new installation guide will walk a person through the integration of the entire system. I can not find that link but will post when I do.
George (c)
Great work. Was not aware of the li-ion battery needing to be over 32 degrees to accept charge.
And the top limit of 110 degrees. Do you know if those numbers are normal numbers for all li-ion batteries of all types and all manufacturers?
The 32 is an engineering standard. They will accept the charge but damage themselves in the process. I will check the second number against the literature. That is one I interpolated and don't want to exceed.
Keeping the temp below 110 would be tough down here. In Texas in the summertime it is easy for the pavement to be 140 degrees, with 100+ degree air temps. I think I have checked the white side of the RV in the sun and have see 120
I suspected that would be the case and probably will go with an AC duct from under the sofa with a fan to draw from inside.
How about some peltier junction coolers in the battery compartment? That and supplemental insulation would probably mitigate temps. Sounds like you've got plenty of surplus 12v capacity. Pretty inexpensive and available from Digikey.
They would work, but how would you get the their heat, out of the battery compartment?
It might be helpful also to get some thin polished stainless steel sheetmetal to put on the underside of the battery compartment to reflect some of the radiant heat from the asphalt.
Don
Don,
I have some of that. How would you attach it?
Trent
Attaching it wouldn't be a problem, 3M VHB double stick would easily be up to it, providing that the bottom skin hasn't delaminated. There is steel framing that outlines the battery compartment underneath as well as the battery support frame so screws could also be used. I would probably use screws just to be sure that the bottom skin wasn't going to start sagging. Also, I would use the thinnest gauge I could get in the polished, though even brushed finish would have have some benefit. Care needs to be taken when using a hole saw to make the holes for the vents (assuming you aren't covering them). Stainless can be very tricky to get a clean hole with a large hole saw. Best to clamp it to some plywood and go slow with a fresh hole saw. Before committing to having that mounted, I would be tempted to experiment on a hot day to see how much of a difference it would make in the temperature in the compartment... say using some gorilla tape to stick it on (when parked of course!) and take readings with and without the radiant barrier.
Don
Nice work. Thanks for sharing. I plan on:
1. Blocking the lower vent holes with insulation and aluminum tape.
2. Installing an insulated bulkhead between the fuel tank and the lithium pack, creating an insulated compartment.
3. Installing a fan to force main cabin air into the newly-insulated house battery compartment, under the couch.
4. Cutting a return air hole under the couch.
5. Install a smoke detector.
My system will have a 48VDC lithium pack, but will require the careful design that you have done.
Good idea Don this is very doable with the tape you mentioned.
The compartment lends itself to several variations of this approach. The bottom of the compartment can easily have insulation added under the tray and with 2 3/4 inches of clearance on the tank side the insulation and extention of the bulkhead would be easy to do. Don had mentioned in his battery addition creating shelves in front of the tank for storage of additives etc. Battery Upgrade Project Teaser... (http://www.foreforums.com/index.php?topic=25846.msg205543#msg205543) That would be doable with an extention. Wish I had the skill sets to bring out the bulkhead in the manner he did as that would be an ideal division.
My other concern in this area is the venting of fuel fumes should I fail to put the cap back on after refueling if it is not separated from the fueling area. I had purchased a small 3inch marine engine compartment blower. The fitting is available to go over one of the upper vents supplies and then leave one of the lowers open. It is small enough to be unobtrusive on the bulkhead. Amazon.com : Attwood Blower H20 Resist (White, 3-Inch) : Boat Blowers :... (http://www.amazon.com/Attwood-Blower-Resist-White-3-Inch/dp/B001O0DE9E/ref=pd_sim_200_4?_encoding=UTF8&psc=1&refRID=1JJJ8C3YDTZGEHDPPZRW) I also purchased a thermostatic switch that comes on at 100 and off at 85.
If we go with AC in and return from coach, I will build the bulkhead of plywood and close off the lower ventilation holes with the caps pictured below and available at Lowe's etc. They have a rubber seal and will fit nicely over the vents from the inside with small screws.
My U270 fuel tank has two big plastic vent pipes jutting out into the coach battery bay. Not a smart design. I will reroute these vent pipes.
Tim, on my U320 those two black vent pipes cross above the fuel tank. They run from the battery compartment forward into the wheel well. In the wheel well they have deflectors to keep splashed water out of the vents. They therefore provide outside air from the wheel well area, hopefully at a slightly positive pressure, into the upper part of the battery compartment which then presumably exits through the two vent holes in the floor of the battery compartment. Actually a pretty good design.
Richard
Thanks I really appreciate knowing where they come out. I was ready to pull the covers off the tank. But with that space I could move the draw from under the sofa area out of the compartment and use within it for return.
George,
As a matter of fact I just pulled the cover off the tank in order to replace my generator fuel lines. That is when I discovered the details of these vents.
Richard