Just wanted to provide a brief report of actual field usage experience as it pertains to my installation of two 100 amp hour Battleborn Lithium batteries, two additional 100 watt solar panels for a total of 520 watts, Victron 100/30 solar controller, and a Victron smart shunt battery monitoring system. This battery/solar system was described in earlier posts in this thread.
I just returned to Virginia following a two and a half month visit to the Montana/Wyoming area. As expressed in the earlier posts my goals were to minimize generator usage, not rely on shore power, and have adequate power such that I was never in a position of running the batteries down below acceptable state of charge (15%), all of which to increase the ability to select sites without electrical hookup.
After the Lithium battery and additional solar panel installation the only time I had to run my generator was once a month for about 30 minutes to prevent carburetor fowling. Also on a couple occasions for about 10 minutes I ran it in order to run the microwave. With the lower humidity and lower higher elevation temperatures air conditioning was not needed thus no generator usage. The three roof vent fans and a portable 110 volt fan did a reasonable job of maintaining comfortable conditions. Actually running the furnace for awhile in the morning before getting up felt pretty good. The TV, DVD, surround sound system, charging various appliances and electronic gadgets required inverter battery power. The use of shore 110v power was not required at any point. State of charge in the Lithium batteries did not fall below about 75%.
I camped in campsites that had partial to full tree shading over part or most of the day. The maximum power from the 4 solar panels topped out at about 300 Watts. I attributed the depressed power output to various factors. These include tree shading, frequent moderate to heavy smoke due to forest fires, cloud cover, etc. Various solar technical resources suggest that manufacture rated output is highly optimistic and are taken using standard laboratory conditions. Some resources stated a more realistic panel output is about 75 to 80% of the panel rating. Using these derate factors the output could be expected to go to 390 to 416 watts. Given the ambient environmental conditions, the fact that because of the curvature of the PC roof each panel incident light angle is different, and that each panel has a small but notable output energy curve difference a further multi panel system derate is expected. I do believe while some of these factors reduce the peak output they may work in favor of extending the period which power is produced. I mention this should another contemplate adding multiple panels this may be useful in the design phase.
It is worthwhile to mention that prior to installing the Lithium batteries I considered adding more panels but decided they would provide little benefit in charging the lead acid golf cart batteries. Frequently the internal resistance of the lead acid batteries throttled the output of original panels. This throttling was expected and was later shown to only occur briefly when the Lithium units were at or very near 100% state of charge thus accepting essentially all the power from the expanded array system.
As mentioned in my earlier post I elected to use the PC supplied alternator charging system while driving. Looking at energy going into the coach batteries while driving it varies but typically is about 10 amps. I have seen it as high as 17 amps. My battery monitor shunt nets out demand and charge current, so I expect the alternator was providing about 20 amps or less to the coach batteries. This seems to be reasonable and at this time I do not have any plans to install a DC to DC converter. Because of differences in PC wiring for the various models I would suggest getting a good estimate of alternator current to the Lithium batteries to prevent damage to the chassis electrical system.
In summary the installation of the Lithium batteries primarily and to a lesser extent the addition of two 100 watt solar panels allowed me to achieve my electrical goals. Being able to Boondock with minimal dependence on the PC onboard generator and being able to use all the power I needed without fear of running out of battery power along with anticipated longer battery life has made this a worthwhile mod for me. The enjoyment derived from the added flexibility of allowing me to stay in camp sites without hookups and not having to run the obnoxiously loud generator added positively to the overall camping experience.
