According to the weather forecast, today was supposed to be every bit as crappy as the past 3-4 days, and maybe the afternoon will be. But I awoke to mostly-sunny skies which have allowed the solar panels to pump some power into the batteries. I was very interested to see how that went.
If you’ve dealt with automobile batteries at all, you know something about how lead/acid batteries behave. You can tell a lot about their real state of charge by how the indicated voltage behaves while they’re being charged. In previous overcast spells when I wasn’t careful about usage, I could run the battery charge down so low the inverter switched off in less than two days. This time I was very careful but far from abstinent. I used the laptop, which is by far my largest continuous draw, only briefly to check messages and touch bases with the blog. I never left unused lights on. I avoided even looking at a power tool. I switched the whole system off at night, and once during the day to avoid parasitic draw when I didn’t need juice anyway.
On the other hand I didn’t stint on lights at night. I charged phone and ecig batteries daily. When I wanted coffee, I used the grinder to my heart’s content. (If I can’t have fresh-ground coffee, I don’t want to be part of your revolution.)
The result? The batteries are actually in very fine shape. I checked them first thing this morning and found them not badly discharged at all, and immediately responsive to a push from the panels as soon as the sun cleared the ridge. It’s 11 AM as I type this, and even having switched the ‘pooter on to type this I expect to hit float by noon minimum, sun permitting.
Understand, for those of you who are just tuning in: This is a very small, almost rudimentary solar electric system. Two 170-watt panels, two 186 amp/hour 6-volt batteries and a 4000-watt inverter out of an old RV. The whole thing cost about $350. But ’tis enough. ‘Twill serve.
I’m still wondering about your system; you’ve said adding batteries would do little good unless there was a commensurate increase in panel output, meaning more panels. But when if there were more batteries to accept existing panel output when the primary battery bank reaches full charge? On marginal days there would not be sufficient output to charge the second bank, but on non-marginal days, especially if the primary bank was close to full charge, you could wind up with 2X capacity in “storage.”
What am I not understanding about how the system works?
Added: I’m assuming two independent battery banks with some sort of switchover to connect the independent banks one at a time to panel output.
Nothing stops you from doing that, I suppose. But consider: If I had enough excess panel capacity to charge twice the batteries I had in a bank year-round, I’d just double the size of the bank and be done with with it. If there isn’t enough excess to do that year-round, you’re flirting with the premature destruction of some expensive batteries.
Isn’t a manual coffee grinder sort of a requisite for an off-the-grid coffee drinker?
Had one once. Have you ever really tried to use one of those? My next one clamps down or I’m not buying it.