December 16, 2014

TT #83 Is it Time for Lithium-Ion Batteries in RV’s? (Part 2)

By: Rob Lowe



In the TechTip #82, I covered the process I went through in making the decision to replace our Coach Batteries with a Lithium-Ion one. We left off with a picture of the crated battery as it was delivered to me. What follows is the installation, upgrading and other considerations together with my answer to the question above.


Making the Change:


There are two streams to follow when making a conversion to a Lithium-Ion Battery: The physical preparation and conversion, and the system changes and potential upgrades. I’ll cover both.

Before beginning the disassembly I turned off all the Battery Disconnects and made sure there was no other power source (i.e. 120Volt power) connected. The compartment space with the original AGM batteries is limited as you can see from the photo. On my coach disconnecting the negative cable always causes a small spark from the terminal (from the charge still left in the Inverter/Charger). With the negative terminal disconnected, I removed all of the interconnecting cables after taking pictures of the connections – just in case. There are a lot of them!


Once all were removed, the remaining longer cables from the ground bus and the "Big Boy” Disconnect relay were carefully tied up out of the way allowing the formed metal battery hold-down plate to be removed by taking out the long bolts through the compartment floor. At this point, the batteries could be lifted out one at a time.

These batteries sat on a fiberglass tray that had four drain holes cut into it and the coach compartment floor (see photo). I sealed the holes both from the top in the floor and underneath using pieces of plastic held in place with caulking.


The Lithium-Ion Battery was uncrated and set on the child’s wagon and brought beside the coach.  The battery was lifted into place. As you can see there is more room. We needed to find a method to tie it down, (not that it could go far!) and decided to use a ratcheting nylon strap hooked to two eyebolts placed through the floor on either side of the battery. This method was simple, secure and safe since there was no exposed metal near the terminals.

There were a number of cables to be attached to each terminal and on this battery the connection is not a post but a recessed into a nut recessed into the battery top. It required a stainless (metric) bolt to be inserted into the nut and tightened to ensure a good electrical connection. Trying to wrestle all of the cables so that the lugs lined up and allow the bolt to be properly inserted was a challenge that in our case required two people to tackle. I determined that a longer bolt would be required and purchased one exactly the length required, since the recessed nut has a closed end. I discovered, after the installation, that there is an accessory post available that could be mounted onto the battery to allow conventional battery connections. In an ideal world, a wall mounted junction block would be installed and a single, large diameter battery cable would link from that block to the battery.


With the installation complete, I turned on the battery disconnect switches and went to look at the monitor panel. Initially the inverter panel was blank. Turning on and off the disconnect switch brought it to life and a reading of 13.2Volts. WOW! Fully charged and then some, I thought.  (I’ve since learned that fully charged is 13.5V to 13.7V and that 13.2V is quite low.) I left the system charging using the existing inverter settings (AGM2) overnight and the next day we went to a planned family gathering where I had expected to be dry camping. I noticed while driving that the dash voltmeter was quickly up to the operating range and the one hour trip brought the battery up to full charge (13.7V). As it turned out we had 30 amp service, so the coach was plugged in for that weekend. Checking the Inverter control panel frequently, it always showed the message "Full Charge”.


Inverter Upgrade:


After that trip and as agreed with the Smart Battery’s Tech support, I called and we made changes to the Inverter settings. I learned that my panel and control board could not provide the custom settings that the newer inverter models could. A call to Magnum Tech Support revealed that the software could be upgraded and should be, in order to gain maximum efficiency from the battery and the inverter. The new coaches already have this "software” included. I also learned that older inverters contain the same basic components as the newer ones, the difference is the "software” which is included on an updated circuit board. In addition to the standard settings (Wet, AGM1, AGM2, etc.) which are pre-programmed battery management profiles, there is a custom setting that can be programmed to suit the battery maker’s specifications. It is noteworthy that this battery is a "Smart” Battery with an electronic control board that optimizes the charging specifically for this battery. It manages the charging, discharging and overall battery management to optimize charging and eliminate damage. Since voltage does not drop off significantly during use, the battery can be charged faster at higher voltage and current levels using a far more sophisticated algorithm than the Inverter Manufacturer can provide.  


I purchased and installed a new Inverter Circuit board and a new Remote panel, upgrading the inverter to the current technology. Both components are Plug ‘N Play, fitting exactly into the locations of the original components. A benefit of the updated components is that more information is visible on the screen (the Inverter status as well as the actual current draw from the coach batteries at that point in time). The inverter can also provide assistance if the power from the line cord drops but does not fail, providing a boost from the inverter (using the coach battery) to supplement the 120V power need for brief periods.


How Does the Lithium-Ion Battery Perform?


In a word: Great!  The system is running close to one volt higher than the original AGM lead-acid batteries, allowing all electrical equipment to be more efficient, using less current. All of the 12 Volt appliances (our fridge, gas furnaces and water heater function well (better). Blower fans run steady, gas operation starts well, even the shower and taps have more pressure when using the onboard water pump. If I had retained the old halogen lights, I am sure they would have been consistently bright, not changing in brightness as the battery voltage changed. So far, dry camping has been trouble and worry free with lots of capacity.


Check out the next Technical Tip as we conclude this series with some other upgrades and some thoughts on this technology and its effects going forward.



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