Since my last blog on "Building the Ultimate Auxiliary Battery System" was published, it became obvious to me that, although my system was good, there was still some room for improvement!
First, the obvious; my 3,500W inverter was struggling to start some of my drone chargers, and turned out to have a fault in the output stage, so was replaced by a new, pure sine wave inverter, rated at 6,000W (continuous), and 12,000W (peak). Surge currents kill inverters, so when it comes to replacing one, I am always of the opinion that bigger is definitely better!
This inverter had a different type of remote on/off control that used a latching switch, rather than a toggle switch. So, the interface to that had to be re-designed, so that I could continue to use the SoC relay to turn off the inverter in an elegant way, rather than trying to trip a 500A relay!
The Main (flooded lead-acid type) battery was also starting to struggle, so it was also replaced. I decided to go down the path of an Optima Absorbent Glass Mat (AGM)-type battery. The Optima brand also uses spiral cores, which provide excellent CCA, even though the Ah rating is less than with a typical flooded type. This means that the car cranks over at higher revs and so starts much faster. Hence, the idea of a lower Ah rating doesn't matter!
So, no real design changes to this point, as my basic design had served me well. However, I finally came across a limitation to the design, when I was filming the Eastern Districts Footy League finals series, which required flying a drone for the best part of 8 hours on Saturday, then backing up to do it all again the next day, for several consecutive weekends! Near the end of each day, my Lithium battery bank in the Cruiser was discharged to the point that the only way I could keep going was to start the car and use the hand throttle to set it on a fast idle. The problem was that the only way to charge my Lithium battery bank in the Cruiser was either through the alternator, or solar. So the only realistic way I could get my Lithium battery bank charged up again for Sunday, was to go for a long drive on Saturday night! I didn't fancy having to do that after an already long day, so had to come up with a better solution.
The answer lay in using a smart AC charger for the Lithium batteries. But I essentially already had two smart chargers for the Lithium batteries, and one of them had a spare input. So, all I really needed was a DC supply to suit the charger, and voila! Fortunately, I already had an ideal DC supply, as part of my drone battery charging equipment. This supplied a suitable DC input voltage to the charger, and could provide more than enough current, even at full load. And this was enough to charge my Lithium battery bank from 10% capacity to full, in about 6 hours. Perfect!
The last update I needed to do to my system, was better documentation and labelling. Do you realise that there are now over 21 fuses in this design, and they are all scattered throughout different parts of the car? So, finding each fuse isn't always easy, especially if you were out on the trail, in the rain, trying to diagnose other issues. So, I have now given each fuse, switch, LED, relay, charger, and battery, their own unique name and corresponding label! I have also constructed a table that shows each component's name, location, function, use, and reasoning behind the function. I would thoroughly recommend that you do the same in your build. Enjoy!
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