lbenson
Senior Member
Apologies for a long post with only a bit picaxe-related.
I don't want to hijack SolarMike's "08M2 PV MPPT Charge Controller", but papaof2's post has me wanting followup:
My current 12V battery bank amounts to about 350Ah, but they're all mix and match batteries, so I'm assuming I shouldn't charge them simultaneously, but should disconnect (under picaxe control) them one by one and charge. The very knowledgeable Warpspeed from TheBackShed.com says that for longest life, you shouldn't keep lead acid batteries under continuous maintenance charge, but should let them drop to around 12V2 (self-discharging) and then recharge. That seems to me not to leave enough headroom should mains go out.
We are within a mile of the distribution center for the electricty generated by 5 dams up the Mersey River, so we usually get back pretty quickly after an outage (we were out for 23 and a half hours after a hurricane last fall). If the batteries gave out I can recharge from a 3KW propane generator.
I had figured out and have coded and tested a round-robin system using SSRs under picaxe control where each appliance (sump pump, boiler, well pump, fridge, and freezer) is switched to in turn, but papaof2's setup seems to suggest that my 3kW pure sine wave inverter might be able to handle all at once. I'm sure it could once startup was achieved, but I've feared that if some decided to turn on simultaneously, over-current shutoff could occur.
I don't know the running or start-up draw of the appliances--except for the freezer, all are hard to get to, and boiler and water pump are single-circuit hard-wired. I have wiring run now to the sump pump, but I'd have to figure out how to flood the sump pump well in order to measure it's draw. As far as usage goes, the freezer comes on for 15 minutes about every hour and a half. The well pump runs for less than a minute for about 15 times a day. The boiler is entirely dependent on how cold it is. The sump pump ran nearly continuously until the power gave out in the hurricane last fall, but didn't ever come on when Hurricane Teddy swiped us last weekend. (The house foundation is piled flat rocks and the floor is gravel--there's no way to keep water out in a deluge.) The fridge would have to be moved for me to put the plug-in power meter on it.
I'm sure there's more, but it's a long post. I'd be interested to know what people with experience or ideas think.
I don't want to hijack SolarMike's "08M2 PV MPPT Charge Controller", but papaof2's post has me wanting followup:
For a number of reasons I feel there's no hope for solar for me in Nova Scotia, but I would like to have backup for oil boiler, well pump, sump pump, fridge, and freezer this winter. Normally, we're snowbirds, but covid (<1 active case per 100,000 in NS over the past 4 months vs for Florida, 3,325 total per 100,000 people) and the likelihood that my wife couldn't get travel health insurance means that we'll overwinter here.I've been "dabbling" with solar for several years, primarily as a "Wait until daylight" option for the frequent but usually short grid outages we have and I've tried a number of commercial solar charge controllers - PWM and MPPT - some are much better designs than others. I'm interested in how "real world" usage works for your design over time.
The solar irradiation for Atlanta works as a rule of thumb for 50-100 miles out from there so we basically have 3 useful sun hours in winter and 5 useful hours in summer. The current system is a 12 volt, 420AH battery bank which is kept charged by a single 250 watt panel via an MPPT controller. With a 2000 watt pure sine wave inverter, the system powers fridge, freezer, a few LEDs and the internet for 8-10 hours - long enough for a storm to pass or until daylight and I could then go out to set up a small (1600 watt) inverter generator. The average running load is under 300 watts but you must allow for the surge watts of starting motors (fridge, freezer, etc.) which is typically 5 to 7 times the running watts but can be 10 times the running watts.
My current 12V battery bank amounts to about 350Ah, but they're all mix and match batteries, so I'm assuming I shouldn't charge them simultaneously, but should disconnect (under picaxe control) them one by one and charge. The very knowledgeable Warpspeed from TheBackShed.com says that for longest life, you shouldn't keep lead acid batteries under continuous maintenance charge, but should let them drop to around 12V2 (self-discharging) and then recharge. That seems to me not to leave enough headroom should mains go out.
We are within a mile of the distribution center for the electricty generated by 5 dams up the Mersey River, so we usually get back pretty quickly after an outage (we were out for 23 and a half hours after a hurricane last fall). If the batteries gave out I can recharge from a 3KW propane generator.
I had figured out and have coded and tested a round-robin system using SSRs under picaxe control where each appliance (sump pump, boiler, well pump, fridge, and freezer) is switched to in turn, but papaof2's setup seems to suggest that my 3kW pure sine wave inverter might be able to handle all at once. I'm sure it could once startup was achieved, but I've feared that if some decided to turn on simultaneously, over-current shutoff could occur.
I don't know the running or start-up draw of the appliances--except for the freezer, all are hard to get to, and boiler and water pump are single-circuit hard-wired. I have wiring run now to the sump pump, but I'd have to figure out how to flood the sump pump well in order to measure it's draw. As far as usage goes, the freezer comes on for 15 minutes about every hour and a half. The well pump runs for less than a minute for about 15 times a day. The boiler is entirely dependent on how cold it is. The sump pump ran nearly continuously until the power gave out in the hurricane last fall, but didn't ever come on when Hurricane Teddy swiped us last weekend. (The house foundation is piled flat rocks and the floor is gravel--there's no way to keep water out in a deluge.) The fridge would have to be moved for me to put the plug-in power meter on it.
I'm sure there's more, but it's a long post. I'd be interested to know what people with experience or ideas think.