Ted and Karen ran off with our better batteries and the three almost nine year old Lifelines were in need of replacement. Something needed to be done.
Some techno-babble ahead.
“Scotty, we need those dilithium crystals back on line, Now!”
I had many long talks with Alan Ferber at Bay Marine Supply in San Diego. He is a great resource for help and ideas and all of the parts needed for a project like this. I also just like talking with him. I had done most of my homework and was focusing on Battle Born LiFePO4 lithium batteries. They have a built-in battery management system to manage charge and discharge, a very high usable capacity compared to their rated capacity, 3,000 or more lifetime cycles and one of the longest warranties available. Their standard sized battery dimensions allowed only four to fit in the battery bay (with a lot of wasted space.) They make a golf cart sized battery with the same capacity whose dimensions allow six batteries to fit in the battery bay. It is a snug fit but leaves enough room for recommended cooling space.
Alan and I talked about the two issues that everyone faces. Charging in cold weather and charging while driving. The solutions were simple and elegant at the same time.
Charging in Cold Weather. Lithium batteries are resistant to being charged when it is colder than 24°. They will discharge without any problem but they like to be warmer to charge. Alan suggested battery heaters. Battle Born makes some that are $200 per battery. We decided to use aftermarket electric hand warmers for snowmobile grips. They are 12v and have a high and low setting. Best thing they were about $10 per set, one pair per battery.
Battery heaters for snowmobile handgrips.
Charging While Driving. Lithium batteries will take all the charge you can throw at them. If you hook them up to an alternator as you would with conventional lead batteries they will take all of the output of the alternator for a long time and may cause the alternator or maybe even the batteries to fail. As you charge a conventional battery the resistance to charging goes up. The closer to full charge the harder it is to charge. Lithium batteries don’t have the same resistance to charging. The solution I chose was to add a Battery to Battery Charger between the alternator and the lithium batteries. These provide a limited charge to the lithium batteries. More when they need a lot and then less as they start to charge and then a smaller amount as they get close to a full charge. This protects the lithium batteries and the alternator.
Charging While Not Driving. When we are not driving and are connected to a land line (or the generator) the lithium batteries are charged using either the charger half of the inverter/charger or the smaller charger or both. Both ways have the same multi-stage charging method as the battery to battery charger. And there are the solar panels that charge the lithium batteries the same way. The solar works when there is daylight whether we are plugged in or not. Sunny days are better than cloudy days.
All concerns were answered. Time to get busy. Alan was helpful reviewing my plans and making suggestions to improve them. He was also very helpful with price discounts. Another Forum member reviewed my plan as well. I appreciated the help. All of this plus the help that I got from Ted made it a go. In the time we expect to own our coach we will never need to buy house batteries again.
I like to have a plan. It always looks good on paper, makes sure you have all the parts you need and lets others critique your ideas.
Testing the Concept.
The batteries arrived by truck on a pallet. I moved them into the shop and in the same space available as I would have in the battery bay I tried several different arrangements of the batteries, cables, switches and bus bars. There was more than one way to arrange the batteries, cables and the controls. Where the cables connect to the batteries and are routed to the bus bars finally led to the solution above. It is not just on the bench but how it is going to fit when they get installed in the coach.
One of the heaters is attached to the side of a battery here and is covered by an insulated, foil faced pad. The heaters are powered by the batteries themselves.
A new battery rack was built and installed after the Lifeline batteries were removed. Learning how to weld at a summer job back in the 1960s has been a useful skill.
The switches, bus bars and controls were mounted on a panel in the shop and then it was mounted in the bay.
Our all purpose garden cart came in handy.
There was much less room in the bay than there is in the shop. Planing ahead, labeling all the cables and having done it in the shop made this pretty simple. It took less than 2 hours to install the batteries. There are three temperature sensors to monitor battery temperature.
All in and hooked up, a switch for controlling the battery heaters and a digital volt meter. Organized and tidy.
Over on the other side of the coach where the Full River L16 batteries were the Battery to battery charger got installed on the back wall. I made a slatted wooden floor. There is now room for my tool box. Before it was all done I installed our small inverter just above the tool box.
This inverter provides power to the refrigerator, a few outlets in the coach and all of the front end electronics … TV, DVD player, internet access device, routers, computers and the satellite dish.
We removed about 1,100 lbs of conventional batteries and racks. We replace them with about 190 lbs of Lithium batteries and a lighter weight rack. More than a 900 pound savings. That is almost 3% of the total weight of the coach!
And the conventional batteries with 1500 amp hrs using 25% of their capacity gave us about 375 usable amp hrs. The 600 amp hrs of lithium battery capacity can be used to 100%. Using them down to 80% gives many more battery cycles and is 480 amp hrs, almost 30% more usable capacity than the conventional batteries.
80% less weight, at least 30% more battery capacity. And batteries for life. A pretty good result.
More Later, Much Love,
Roger and Susan
PS. Thanks to Susan for editing.