While boondocking at Quartzite in January realized my two six-year-old 8D Interstate lead acid batteries had lost their juice. Decided now was the time to upgrade to lithium and to upsize capacity to allow for a future residential or 12 volt compressor fridge as mine is starting to physically fall apart even though it performs well.
I ordered from Amazon two Ampere Time 12V 300 Ah LiFePo4 batteries in the 8D form factor. These batteries have been reviewed by Will Prowse in a tear down YouTube video and the cells, workmanship, connections and BMS, are good quality. However, they lack cold weather charging protection. He has another video showing a work around for the lack of cold weather charging protection that I followed in my installation. I have a Victron 100/70 solar charge controller, BM 712, and 900 watts of solar panels along with a Xantrex Freedom 458 2000 watt inverter/charger (manufactured 2010.)
My upgrade path to accommodate the lithium batteries was as follows:
1) Ordered Victron Orion non isolated B2B charger to replace original battery isolator. The non-isolated Orion assumes the house and start batteries are both grounded through the same chassis. It is a little smaller and less expensive than the isolated version that has a separate ground wire for the house batteries. That installation saga was documented recently in another post. It was complicated by a mis-wired DUVAC alternator, which I eventually resolved. My original isolator was mounted behind and above the start batteries, this is where I mounted the B2B. Following Roger's recommendation, I removed the isolator, installed a single post 5/16" battery connection post to relocate the alternator output lead from the center post of the original battery isolator. From that post I constructed a new 2-gauge battery cable directly to the start battery positive post. Then I ran a 6-gauge wire from the new post directly to the new Orion B2B input lug. Ran a 6-gauge ground wire from Orion to a nearby 3/8" ground stud that the start battery connects to. The Orion output charge line for the new lithium house battery bank went to the house side of the boost solenoid. These connections were very short, all under 12 inches.
2) Ordered two Facon 12x18 inch RV 12volt thermatically controlled holding tank heating pads. These are wired to the house battery bank in parallel with separately 10 amp fused connections to the supplied two 12 volt on off switches which were mounted to a plastic outlet box with a blank cover drilled out to the accept the switches. The heating pads are mounted to the original fiberglass battery box liner that sat underneath the house batteries in the factory rack. Will Prowse recommended attaching the pads to a piece of sheet metal, but the pads had a warning not to mount them to a conductive surface. Hmm, I used the fiberglass and put a piece of luan plywood underneath the fiberglass with two holes for the power wires to exit underneath the battery box. The pads are isolated from conductive surfaces. There was some overlapping of the heating pads, don't know if that will be a problem or not.
3) Installed a Victron temperature sensor, called a "Smart Battery Sense." It has a positive and negative lead attached to the house batteries and physically is mounted via sticky tape to the top of the battery. Once connected you can create a Victron Bluetooth network, and then connect via the network the solar charger and Smart Battery Sense so that the solar charger will not charge if the batteries are below a set temperature reading from the Smart Battery Sense. The set points are user configurable. I went with 5C. This was part of the Will Prowse video on cold temperature protection for the Ampere Time batteries and their ilk. I've also connected my BMV 712 to this network. Ampere Time is now selling an internally heated battery.
4) My Xantrex Freedom 458 has a Gel2 setting that comes very close to the charge parameters for the new house batteries. That has been programmed. It is not possible to create a custom program, but I believe this will do.
5) I ordered from Windy Nation two 4/0 gauge battery cables (one red and one black) with 5/16" connections to parallel the two new house batteries. The original + and – house battery cables were used to tie the new batteries into the coach electrical system. I did find it necessary to make some new 8mm 1.25 pitch battery studs to accommodate some of the connections, as the supplied battery bolts were too short. 8mm and 5/16 are very close in size, so 5/16 cable ends work well. The home-made studs, bolts with the head cut off, were a pain in the rear. Stainless is hard, and I didn't have a metric die to chase the threads. I did the old (leave a nut attached trick) and tried to chase the threads once the head was cut off. That worked just barely on two of the four. Used original bolts on the two outside connections. Get yourself a pre-made stud or have a die handy to clean up the threads.
6) Trik L Start. I've used a Trik L Start for over five years with great results. Was watching a YouTube video by the "Fit RV" on his lithium upgrade of a new Winnebago Ekko motorhome and he was installing an Amp L Start. He mentioned that the Trik L Start is not recommended with lithium house batteries. Sure enough, went to the LSI industries website and they have an updated model of the Amp L Start with a remote ignition switch sensor for lithium house batteries and a B2B charger. Got one on order.
7) I plan to primarily use solar and the B2B to charge my new house batteries. I will use the Xantrex when needed and I can assure that there is not the possibility of charging the new bats when they are below 5C. I added some foam board insulation around the sides of the new batteries and put some insulation on the floor of the battery bay which has two 3-inch vent holes in the bottom. I'm monitoring the battery bay temperature with a remote temperature sensor on the floor of the bay in addition to the new Smart Sense Temperature reading from the battery.
After a couple days use it looks like everything is working. I've got a 30-amp shore power connection for the next two weeks, but I'm leaving my Xantrex charger offline to see how quickly the solar charges my new batteries. I've got several nights coming up below 32F with lots of propane furnace runtime during the night. This should help me evaluate the new system. At Q a couple of coaches were using an Ampere Time battery or planning to order some. Hope this helps others considering their options. Obviously, Battle Born is a more elegant pathway and the SOK is also great. But with Ampere Time you can get a 200/300/400 Ah battery in the 8D format for a very good price point with a quick delivery via Amazon. They were well packaged. Ampere Time offers self-heating batteries in 100 and 200 Ah capacity.
I am not an electrical engineer or certified RV tech. This is what I pieced together from information on the forum, manufacturing websites, online reviews, and YouTube University. I considered building my own batteries, but the price point for Ampere Time and the tear down review by Prowse led me to this path. The 8D form factor is very elegant for many of the Foretravel coaches. I went from 280 pounds of battery to 140 pounds, no monthly maintenance, three times the useable capacity, more stable voltage under use, and quicker recharge. I also opened up new opportunities for a refrigerator.
Good job, Patrick. I think you will find that you will very rarely need the heating pads. Monitor the temperature of the batteries in the bay, that is what matters not the outside air temp. If you are actively using the batteries, charging, or discharging, the batteries will stay warm on their own.
I have 1200 watts of solar but find that most driving days with my B2B charger turned OFF, solar alone is sufficient to arrive at my destination fully charged. Do some experimenting, you will find the right balance.
Some of these projects seem complex and daunting to many. Reading, learning, asking for some help, and careful planning makes the project easier to get done right the first time. Be sure to document your changes for your use and maybe the next owner's use too. I know you will now get to see, as many of us have, just how big a change switching to Lithium batteries makes in your coach life. Thanks for posting.
Sounds like a win, win, win, win, and a win! :thumbsup: Thanx for the detailed report.