Double Checking My Work

Re: Double Checking My Work

Welcome to the forum.

Four 225 Amp hour 6 Volt batteries will give you 450 Amp hours @ 12 Volts, not 550 Amp hours.

You have quite a large equipment list, with no run times. That makes it impossible to determine how much battery capacity you actually need. Except that the first item on the list, the 550 Watt A/C unit, will take all the battery capacity you have. Your batteries can supply about 2.2 kW hours AC at 50% DOD. That would run that A/C for 4 hours continuous. The duty cycle will lengthen that a bit, but it basically would give you a total run time of 12 hours or so before the batteries are dead. And that is with nothing else turned on.

300 Watts of panel is not sufficient to recharge that battery bank either. You really need around 700 Watts. I do not see any charge controller listed.

Why two inverters? Between the two there will probably be no tare savings, and the 1kW unit is unlikely to start the A/C unit anyway. You will be using the generator a lot.

Is this the proper setup?

Solar Panel --> Charge Controller -->
Battery Bank --> Electrical Panel
Generator --> IOTA -->

Yes, with the Iota going to the battery bank as well of course.

Question 2:

Can I run the generator and the solar panels at the same time? They should both be "smart" enough to regulate themselves.

2a:

Even if I "can", would it be better to run the generator in the morning while not under full sun and at lowest battery capacity?

Yes and yes. Multiple charge sources are usually not a problem so long as the combined current of both does not exceed the maximum for the batteries. Running the gen to Bulk in the morning is the most economical use of gen power.

Question 3:

I plan on running the 2 inverters directly off the batteries; the 1000w for the AC unit, and the 400w for Exhaust Fan. So coming off my battery bank would be: IOTA (input), Charge Controller (input), Electrical Panel (Output), Inverter1 (Output), and Inverter2 (Output) - Does that seem right?

Think separate circuits. The charge controller's output goes to the batteries. The batteries' output goes to inverter #1 and inverter #2 through separate wires and fuse/breaker each. The Iota's output goes to the batteries as the charge controller would. Considering the number of connections you're proposing this would be bus bar territory.

3b:

Would I be better served using the panel and running my inverters into the panel and fusing them with a breaker there? Both inverters have an on/off switch.

You would be better served to buy a single inverter-charger that will do the whole job on its own. Preferably 24 Volts. Avoid 12 Volts if at all possible. That includes 12 Volt loads. Also if these proposed inverters are MSW type don't expect them to run any motors or at least not well.

Question 4:

Grounding... what needs to be grounded? Most of my 12v equipment doesn't contain grounding wires. The inverters don't seem to have it either. Thoughts? Advice?

Grounding is one of the most complex subjects there is to electricity. We have numerous arguments, er, discussions about it on the forum. All devices with metal cases will have electrical safety ground, including panel frames and mounts. DC negative is usually grounded (although not under the new NEC DC GFCI rules). AC Neutral is grounded unless it is an MSW inverter that can not have that N-G bond.

I'd suggest two big changes: one being to go with a single pure sine 24 Volt inverter and forget the 12 Volt stuff entirely. If you must have 12 Volts for something use a DC to DC converter. Two would be buy a Kill-A-Watt and measure the actual power consumption of items you intend to use or at least similar ones. That way you'll have a realistic idea of how many Watt hours you need to supply. My guess is it will be a lot more than you expect, necessitating a large increase in system size or a severe curtailment of devices.

Re: Double Checking My Work

SolarBurner wrote: »

I have a 30amp Controller. When you say 300 watts is not sufficient to recharge that battery bank, you mean at all, or assuming a 50% DOD each day? This is more of an educational experience for me than anything else. My first goal would be to see what I can run each day/night and recoup with the 300w panels.

I mean it won't charge that much battery at all. It could maintain it, but it would never supply enough power to recharge.

Your three 100 Watt panels probably put out around 5 Amps each. So that would be 15 Amps all together. That's a 3% charge rate on 450 Amp hours. Even at 25% DOD (approximately 112 Amp hours) it would take longer than there would be sun to supply the current. Plus the rate will not be sufficient to cause much activity within the batteries.

Don't expect your long daylight hours to help much. We have 16 hours of it up here in Summer but since that isn't direct sunlight on the panels the equivalent good sun hours is still less than 6.

Second to that, would be what can I run each day supplementing recharging the battery bank with the generator for 2-3 hours a day.

That would depend on how much you can run off the generator while charging the battery. There you run into a little problem called Power Factor; the power drawn by the Iota charger will actually be higher than the power it delivers to the battery. So to get 'X' Watts at the battery the gen will have to supply 'PFX' Watts. Whatever is leftover can go to loads which may or may not have the same PF problem. A 1600 Watt gen like the EU2000i can suddenly seem very small.

For example the 450 Amp hours being charged at full current of 45 Amps looks like (45 * 12) 540 Watts but will actually demand more like 630 Watts. Now you have less than 1000 Watts left for loads.

What the batteries would supply all on their own is about 1.2 kW hours at 25% DOD. To recharge them fully from solar would require 788 Watts on a PWM type controller or 700 Watts on an MPPT type controller (more efficient = more expensive) or with no loads and minimum charge rate 350 Watts and an MPPT controller.

Now the good news is I have a similar size system, only with 232 Amp hours @ 24 Volts and 700 Watts of panels. I can actually squeeze 2.4 kW hours out of it per day in Summer through careful load management. I have an advantage in higher elevation which increases insolation, but you could have similar results. Not enough for an A/C but it does run a refrigerator, water pumps, satellite Internet & computers, as well as lights and even an occasional microwave zap.