Hello,
I am working on building a battery bank system for my house to run just the essential systems. However, given the winter that we are currently experiencing, I'm wondering if there is a way to set up a back up charger for extended periods of no sun.
I know that the Classic has a Low Bat Disc mode on Aux 1. When the battery voltage hits the low setpoint, it seems like that could be set up to trip a relay that turns on a standard AC battery charger in order to bring it the voltage back up to a "safe" level. As I understand, leaving the batteries at below 2.10V/cell for an extended period of time can cause sulfation damage.
The problem I see with this may be related to my understanding of the way the battery bank voltage is measured. If, for example, a 12V battery bank voltage has depleted to 12.6V (2.10V x 6cells) and that was the setpoint trigger for Aux 1, then the Classic would turn off Aux 1. If that was hooked up to a normally closed relay that turned the power on for a (for sake of example) Schumacher battery charger, it could then begin using mains power to bring the bank back up. However, I would assume that the AC charger would apply a voltage around 14.4V to the terminals of the battery bank. Would the Classic detect this 14.4V and think that the battery bank is now charged and therefore turn Aux 1 back on? Or is it able to distinguish between a voltage from the battery bank and a voltage being applied by an external charger?
If it cannot distinguish, then I considered setting the delay time to something like an hour so that, after an hour, it would turn the external charger back off, measure the voltage of the bank, and then trigger Aux 1 one way or the other depending on the voltage level of the battery bank.
Am I off track on this? How do people keep their battery banks from depleting to damaging levels outside of disconnecting everything and going without power?
Your question is not clear.
Are you asking about what happens when your Mains power is down or when it is up?
What PV panels do you have? Number?
From what you describe , if you don't have panels you are in trouble if it is a long outage...
What inverter do you have?
Yes, you can certainly do this with Aux 1.
I was thinking the same thing about having Aux 1 stay on for about an hour after the voltage
on the battery rose above 14.x volts, also.
Yep, not a bad idea. You ~could~ even have it start a generator if wanted. However, without
feedback from the generator, the system would not know if the generator started and might
keep trying to start it and might not be good for some generators.
boB
PS, I wrote that before seeing Westbranch's posting.
I don't have a fully built system yet. Still working on purchasing the components. So far, I have 6 245W panels. I discovered yesterday that the inverter I have won't work; I need 240VAC and it won't do it.
I want to basically have two electrical systems, one for essential systems and one for non-essential systems. I plan on starting small with the essentials systems; probably just the well pump to start. (I know, not really a "small" load, but it's probably the most critical system I have) Then, depending on battery bank capacity, I'll see which systems get moved from one to the other. Probably the furnace fan next. There are a lot of devices that I never plan on migrating. For example, I'll never run a washer, dryer, air conditioner, entertainment system, etc on a battery bank system. For all of those, if I don't have grid power, I'll have to do without.
So, the desire is for the essential systems to run off-grid as much as possible. However, having 6*245W worth of potential solar power isn't worth anything if the sun doesn't shine for a week and my batteries are depleted. I'll need a secondary way, other than solar, to charge the battery bank. So, the thought was, assuming the grid is available, why not use that in a pinch? Hopefully, though, the sun will come back and, at that point, the AC charger would need to step out of the way and let the Classic take control of the battery bank.
you should investigate a low cost 240v generator to run all your heavy loads, otherwise this emergency system is going to cost you a lot... for charging in extended outages a smaller inverter type generator (~2000W) will run all day charging and only use ~ 1.5 gal or so of gas.
Lots of options but the best way to start is to write out a plan based on the measured loads you want to run off solar. That way you have a target to achieve rather than an idea...
Quote from: Weston on March 17, 2014, 03:10:01 PM
I don't have a fully built system yet. Still working on purchasing the components. So far, I have 6 245W panels. I discovered yesterday that the inverter I have won't work; I need 240VAC and it won't do it.
Stop and rethink... You are going to need an inverter for your critical loads. Why not buy a grid-interactive inverter? They are designed to provide backup, maintain a battery from grid (if needed), and will get along with your solar controller. They also have built in transfer switches.
But actually, I'm not sure what you are trying to do....
Rereading your posts, it looks like you intend to cycle these batteries every day to run your loads, even when the grid is available... If so, why? In the long run it will cost you much more than just running the loads off the grid. If this is your goal, I suggest that a generator may be a more cost effective way to deal with occasional grid outages.
--vtMaps
I have to confirm this officially, but the word is that in my area the power company does not allow grid-tied systems. It could be that I've gotten some misinformation and I would have to contact them directly about it. That said, I'm not entirely comfortable with the power company being a stakeholder in what I do. If I'm not connected to them, they have less ability to dictate what I do.
We live in an low population density area where there is not a lot of infrastructure. There is basic rural electric and landline, but no city-type services like natural gas, sewer, internet (we have satellite), etc. We've experienced power outages during the cold months this past year and it's something I want to eliminate.
Sure, I could go the generator route, and I do have one, but this past Christmas there were people in a neighboring county that were out of power for 4-5 days. Thankfully, we were not out that long. That's a significant amount of fuel to maintain.
When I see people building solar systems, I keep seeing three typical systems:
1) Battery bank for backup only - I don't quite understand this. Why go through the expense of building the system only to have it sit there unused 99.9% of the time. And, since you're not using it on a daily basis, you won't know that when the power does go out, the bank is undersized and will only last a couple hours.
2) Whole hog - Put everything in the house on solar, no grid at all. This seems like overkill. These are the people that are are trying to get their air conditioner on their solar system. I'm mainly interested in being off-grid for the systems that need to be off-grid.
3) Grid tied - I know there are more expensive models that can maintain a battery bank, but the typical grid-tied inverter is useless when the power goes out.
I'm looking for somewhere in the middle between backup-only and whole-hog. I would like to size the system so that it's large enough to not drain the bank on a daily basis. However, I think that's going to take some experimentation to get the variables right.
For example, I had the county office pull the records on my well pump yesterday and it's a 3/4 HP, 230V pump. Google tells me that 3/4hp is roughly equivalent to 560W. Theoretically, my 6 245W panels could put out 1470W. Of course, that's purely theoretical; in actuality, I know it will likely be somewhere significantly lower. Predicting that, I feel, is very much like trying to predicting the weather; I figure it's going to be easier to estimate the right numbers, build it, and then scale up or down based on actual measured results. Similar to the sun's unpredictability, while I know the theoretical power draw of my well pump, that's only when it's running; it doesn't run all day long.
I'm basically looking for a safety net such that, if I put my well pump on a battery bank system and I've underestimated the inputs and outputs, I would like a little breathing room, perhaps provided by a grid charger, while I work on scaling things up. When funds allow, I have considered getting a wind turbine and a second Classic, because here, when the sun isn't shining, the wind is usually blowing. The goal, though, isn't to cycle the batteries from full to depleted all the time; that would be hard on them. If that's happening a lot, then it indicates to me that the system isn't keeping up and something needs to be done.
If it goes the other way, and I have way more than I need to run the pump, then the next step is to add another critical system and see if the system can handle it without needing an auxiliary power source.
As far as the inverter goes, I thought I had a 110V pump and then found out otherwise.
Weston, are you using one of those Co-Op utility companies ?
Nope, just Consumer's Energy in Michigan. It's possible that the information that we got was bogus. The person said that we couldn't do grid-tied because we were in the vicinity of a hydroelectric dam. But they were not an employee of Consumer's.
I'm curious though, what is it about my scenario that's leading people to recommend a grid-tied solution? I mean, the MidNite Classic is designed to charge a battery bank; if I do grid-tied, I don't need a charge controller.
Well, for straight grid tie without batteries (backup power) you certainly would not need a Classic or any "charge controller" for that matter...
You would most likely need a PV combiner though. Maybe that's why they were recommending MidNite ?
I found this web page about your utility...
http://www.consumersenergy.com/content.aspx?id=1800
It ~may~ be that you can only offset your own power usage but I did not read the entire page.
You can also check out net metering info state by state here which is where I started from...
http://www.dsireusa.org/
Not sure about the proximity to a dam but I wouldn't think that would matter, really. But I'm not positive.
boB
Quote from: Weston on March 17, 2014, 09:36:55 PM
I'm curious though, what is it about my scenario that's leading people to recommend a grid-tied solution?
I did not suggest a grid-tied solution (although if it's available you should consider it). I suggested a grid-interactive inverter. That means it can use the grid to charge your batteries. That doesn't necessarily mean that you can sell to the grid.
I still don't understand why you want to have, and cycle, a large battery system. The power you produce through your batteries and inverter will be MUCH more expensive than grid power, even if you recharge the batteries for 'free' with solar panels.
Perhaps a small battery system plus a generator would be more cost effective. Run the generator a few hours per day for well pump, refrigeration, etc, and then use the batteries for 'quiet time'... lights, computer, tv and other small items that don't need the power of your generator.
--vtMaps
Ah, I see the disconnect. While a cost efficient system is certainly desireable, it is not the primary motivating factor for me; independence is the primary goal here. Right now, I am dependent on the power company to live my life. That means that if I am unable (or unwilling) to pay my monthly power bill, I will soon experience a crisis. Right now, I have a good job and the electric bill is an acceptable amount, but that may not be true tomorrow; I could lose my job or the price of electricity could go through the roof. I want to adjust the balance to where having a connection to the grid is a convenience, but not an absolute necessity. In fact, I'm very tempted to label the 2 electrical systems, "want" and "need".
Several years ago, at our previous house, we discovered that the power company had been reading the wrong meter for the last 4 years; we were actually paying our neighbor's bill and they were paying ours. My wife figured it out because she had been try to lower the bill by turning down the heat, keeping lights off, etc, but no matter what we did, the bill kept increasing. Meanwhile, our neighbors found that they could use whatever power they wanted and the bill kept going down. After we convinced them that there really was something wrong, it took the power company 6 months to correct the error in their billing system, and in the interim they told us, "We don't really know what you owe us; so just guess and send it in". Then, once the error was resolved, they told us, "Oops, our bad. Yup, you overpaid, but it's going to take too much work to figure out how much we owe you, so we're not going to do that. Have a nice day!" My wife estimates that the amount we overpaid over the 4 years was at least a couple thousand dollars. So, you can see why I'm not too excited about the idea of selling power back to the power company.
From my perspective, when you generate elecricity from solar or wind, the resulting current is too inconsistent and spiky, so you need to dump it into "reservoir" to gain some consistency in output. That reservoir can generally either be a battery bank or the grid and you generally only draw power from one of those sources at a time. I would assume that a "grid-interactive" inverter is mostly the same as a "grid-tie" inverter; you're feeding power and drawing power from the grid and the battery bank only comes into play when the grid goes down. Or, in other words, where a regular grid-tie inverter's anti-islanding ciruitry would shut everything down, the grid-interactive system would start drawing power from the battery bank. The problem I see with that idea is that, since the battery bank is only there for the proverbial "rainy day", it is likely to be undersized and get depleted very quickly. To use my example above, if I lose my job and can't pay the power bill for 4 months, it doesn't feel like I'm going to be able to rely on a system like that.
Quote from: Weston on March 18, 2014, 08:56:51 AM
Right now, I am dependent on the power company to live my life. That means that if I am unable (or unwilling) to pay my monthly power bill, I will soon experience a crisis. Right now, I have a good job and the electric bill is an acceptable amount, but that may not be true tomorrow; I could lose my job or the price of electricity could go through the roof.
While you still have a job you should endow a fund to buy yourself replacement batteries and equipment. Or alternatively, endow a somewhat smaller fund to pay your electric bill in the future. Try to enjoy being dependent on the battery company to live your life. (and the oil company for your generator). Pray that a single lightning strike doesn't take out all your electronics at once.
--vtMaps
Since this discussion seems to have devolved into people picking apart my motives for building a battery bank (I thought that of all places, people here would understand), let me attempt to get back to my original question.
If I apply a charge to the battery bank terminals from a charger source other than the Classic, it seems that the Classic will detect that as voltage coming from the battery bank itself and clear the Low Bat Disconnect condition. Assuming the external charger is controlled by the state of Low Bat Disc, unless I add a delay, this would cause it to toggle like the following:
- battery hits V Low setpoint
- Low Bat Disc -> Aux 1 off
- NC relay turns on external charger
- external charger begins charging, bank terminals read above V High setpoint
- Low Bat Disc -> Aux 1 on
- NC relay turns off external charger
- battery has not charged enough, still below V Low setpoint
- GOTO 2
Adding a V High delay, it seems like it would cycle like this:
- battery hits V Low setpoint
- Low Bat Disc -> Aux 1 off
- NC relay turns on external charger
- external charger begins charging, bank terminals read above V High setpoint
- delay for an hour (or so)
- Low Bat Disc -> Aux 1 on
- NC relay turns off external charger
- if battery has not charged enough, still below V Low setpoint, GOTO 2
- otherwise, resume normal operations
Weston,
I know what your asking and why. I just received a KID for my off grid project and have many questions but hesitate to ask for the very reason stated above.
Have you called tech support? I would hope a engineer should be able to address this.
Mark
Hello Weston
I get it. Build what you want and enjoy it.
Here is my probably incorrect idea, shoot holes in it at will, use a standard off grid inverter and treat the grid as your generator input.
Use the inverters automatic generator start (AGS) to close a relay, when the inverter sees power on the AC side it will charge just like it would from a generator and stop/open the relay when charged.
Have fun
Wade
Weston, sorry for the unhelpful comments... you were quite vague in your requirements for equipment and motivations for solar. Solar can be very disappointing if your expectations are not realistic, and I was probing to find out just what you expected from a system, and why.
Quote from: toothy on March 19, 2014, 02:11:48 AM
Use the inverters automatic generator start (AGS) to close a relay, when the inverter sees power on the AC side it will charge just like it would from a generator and stop/open the relay when charged.
I think this makes sense to accomplish your goals. Buy a full featured off-grid inverter (magnum, outback, schneider) and use the AGS and the built-in transfer switch.
--vtMaps
I did call, actually. Unfortunately, my cell phone dropped the call and cut the discussion short. I decided that, since the engineers were busy people and my question is not urgent, it might be better to ask my question in message form, so that they might respond at their convenience, rather than tie up a phone line.
That's an interesting idea, I will probably look for that feature when I'm researching inverters.
The way I see it, there are 4 points at which you can feed external power to a battery bank that's not getting enough solar input to match demand:
1. Input to the charge controller
This is wildly theoretical, but, with a bridge rectifier, you could take 110VAC from the grid and make it look like a 110VDC source. Switching would be controlled by the Classic's Low Bat Disc
- pro: The Classic stays in control of the charging
- con: This would likely mess with the MPP tracking
2. Input to the battery bank
This is the scenario I described above, with an external AC charger that is turned on by the Classic's Low Bat Disc
- con: Have to use a delay to prevent it from toggling on and off due to voltage readings on the bank bank terminals
- con: External charger may not charge as efficiently as a Classic
3. Input to the inverter
The scenario proposed by toothy and vtmaps, using the AGS to feed power from the grid into the inverter as if it were a generator.
- pro: More efficient, because the electricity is not being converted from AC to DC and back.
- pro: Does not draw power from the bank, allowing all incoming solar power to be put towards bringing the battery bank back up to an acceptable voltage.
- con: Does not charge the battery bank. I am assuming that, in this scenario, the Classic is still responsible for charging the bank and the inverter does not have charging features. Until the sun comes back out, the bank will stay in a low charge state. I don't know how long it can stay that way before sulfation starts becoming permanent. Perhaps it's long enough that it's not a concern?
- con: Requires a more expensive inverter with more features
4. Input to the electrical panel
An automated transfer switch is triggered by the Classic's Low Bat Disc condition, switching the electrical panel temporarily to grid power.
- pro: More efficient, because the electricity is not being converted from AC to DC and back.
- pro: Does not draw power from the bank, allowing all incoming solar power to be put towards bringing the battery bank back up to an acceptable voltage.
- con: Does not charge the battery bank. Until the sun comes back out, the bank will stay in a low charge state. I don't know how long it can stay that way before sulfation starts becoming permanent. Perhaps it's long enough that it's not a concern?
- con: There would probably be a momentary interruption in power when the transfer switch flips. Might be an issue for electronics (blinking 12:00)
With a hybrid inverter/charger you can use the inverters AC input to charge the batterys via the internal charger function.
But you are right , its always more efficient to use the AC direct, rather than charge batterys.
Quote from: Weston on March 21, 2014, 10:46:45 AM
3. Input to the inverter
The scenario proposed by toothy and vtmaps, using the AGS to feed power from the grid into the inverter as if it were a generator.
- pro: More efficient, because the electricity is not being converted from AC to DC and back.
- pro: Does not draw power from the bank, allowing all incoming solar power to be put towards bringing the battery bank back up to an acceptable voltage.
- con: Does not charge the battery bank. I am assuming that, in this scenario, the Classic is still responsible for charging the bank and the inverter does not have charging features. Until the sun comes back out, the bank will stay in a low charge state. I don't know how long it can stay that way before sulfation starts becoming permanent. Perhaps it's long enough that it's not a concern?
- con: Requires a more expensive inverter with more features
Wrong assumption. Both Toothy and I mentioned previously that it does require an inverter/charger. The inverter/chargers also have a built-in transfer switch. You can program an inverter/charger to NOT charge the batteries if you wish, but it will still transfer the AC to the loads.
As for the inverter/charger being more expensive, I thought you made it clear that this system is about independence, not cost-effectiveness.
--vtMaps
QuoteWrong assumption. Both Toothy and I mentioned previously that it does require an inverter/charger. The inverter/chargers also have a built-in transfer switch. You can program an inverter/charger to NOT charge the batteries if you wish, but it will still transfer the AC to the loads.
I assumed, given that this is a MidNite Solar forum, that their product should be included in the design. Otherwise, tell me why you are hanging out on this forum attempting to persuade people to buy products that MidNite does not offer?
I know there are devices out there that are all-in-one charger/inverter/grid-tie/transfer-switch/slice/dice/make-julienne-fries kind of devices. I happen to like what I see in the Classic 150. I like the features and I like what I've seen so far of the company that makes it. I'm guessing that there are many people who have built successful battery banks with the Classic in just the scenarios I described.
The other things is that I don't know how those all-in-one devices scale. If I have a separate inverter and charge controller, and I want to add a wind turbine to an existing solar system, I'm pretty sure I know what to do: I can just buy another Classic 150, set them up to talk to each other, and leave the inverter as is. I don't know how this works with the systems you're describing.
QuoteAs for the inverter/charger being more expensive, I thought you made it clear that this system is about independence, not cost-effectiveness.
You're being deliberately obtuse. Please stop; it's not constructive to the discussion. If you go back an read what I said, I said that cost-effectiveness is not my primary motivating factor; I did not say that it was not a factor at all. If money were no object, I certainly wouldn't be visiting this forum and trying to figure it out on my own; I'd find a professional, tell him what I wanted, and pay him to figure it out.
Of course cost should be included as a factor when comparing solutions. If you've got two systems that both meet the requirements equally and one is more expensive that the other, why would you choose the more expensive one?
This thread is getting out of hand. Please understand that we are trying to help.
If you want to use a battery with the grid, the best way is a purpose built hybrid grid interactive backup inverter. They are expensive.
If you want to use a classic with the grid you have two options:
- classic plus iota type ac charger, using aux1
- classic plus ordinary inverter/charger, using AC in.
Either will work. In the former, the hold and delay settings on aux1 can be used to take care of the contention / chatter etc.
With the later the hybrid inverter, has various settings to determine how the grid support is used and provides its own independent charging system.
There is a thrid way but its not that recomended, get two classics, and feed the iota into the pv terminals on one of them (via a big power resister), and that way you would be able to use followme coordination. But you dont need coordination in the followme sense because both sources are not being used during the later charge stages only one at a time.
Good luck. You may also like to check out the NAWs forum.
VT and ZB, from the beginning, the OP has a concept that he is unable or unwilling to state as we have questioned his 'plan'...
IMHO he has now flamed us while we have patiently tried to discuss various options for him to achieve his goal....
Nuff Said!
Sorry to drift off topic, folks, but. Lets work the problem.
We all know it is hard to clearly describe some things even if you are well versed in the technology. Doubly so if it involves those who are not.
Might need to back this train up and get a fresh perspective on exactly what the thread opener wishes to achieve.
Frustrating on all sides but lets not get sidetracked on conjecture, please.
Anyway, its pretty clear (to me) that turn key options exist and I happen to have one myself but off the shelf solutions do not fit every need. More information is better than less and a clear goal definitely helps.
Thanks.
Tom
I appreciate your responses, zoneblue and TomW, they gave me some hope. I'll give it another shot at explaining my question better.
Here's the scenario: Imagine that you have
- 6 solar panels
- a Classic 150 charge controller
- an inverter (I have a Whistler 2500W inverter (http://www.amazon.com/Whistler-Pro-2500W-Watt-Power-Inverter/dp/B003R7LQDI/ref=sr_1_1?ie=UTF8&qid=1395750899&sr=8-1&keywords=2500w+inverter), but it won't do 220VAC, so it won't work. I haven't figured out what one to buy instead)
- and some number of deep cycle batteries (my father-in-law manufactures electric wheelchairs and has offered to give me a bunch of deep cycle batteries).
Those are the basic components to build an off-grid system, right?
So, let's say you hook it all up and it works great; the solar input is keeping up with the demand all summer long. Now, one cold winter day, a snowstorm dumps a foot of ice and snow on your solar panels. You estimate that it's going to take at least a week for you to get it fully cleared off. Over the course of that week, your battery bank starts slowly depleting, because your panels aren't generating any current. Finally, it hits a low threshold and everything shuts down. You're now sitting in the dark.
Question 1: How long can you let the battery bank sit in that low charge state before the sulfation starts to become permanent damage?
Going further, you realize that you've got an 110 VAC source available to you. Whether that's a generator, a grid hookup, or even a big long extension cord that goes over to the neighbor's house, let's just assume that it's 110 VAC and the available wattage can handle the load. For purposes of this discussion, I'll call it "generator".
One solution to getting yourself out of the dark would be to install a transfer switch and manually switch the electrical panel over to the generator source in an emergency like this. But, going back to Question 1, that would just run your house; it wouldn't charge the bank back up, so it would still be sitting at low charge for a while. Now, if I don't need to worry about sulfation for quite a while, then this is probably the simplest solution. Run the house off the generator until the panels start producing current again.
Going one step further from that solution, it occurred to me that I could use that generator power to also charge the battery bank up with some sort of AC charger. That would get the bank back out of the sulfation danger zone.
So far, in this scenario, it's all manual. I would have to keep checking the display on the Classic periodically and see where the levels are at. Once the bank was charged back up, I would then go pull the switch and switch it from generator back to battery bank. If I can't figure this out, at the very least, I'm pretty sure this manual method would work.
However, one thing that is neat about the Classic is that it has the two Aux contacts. So, I thought, what if, instead of doing this all manually, I let the Classic control the process using a relay and Aux 1. And that is the question I posted in my very first message. As I understand it, the state of Aux 1, when using Low Bat Disc, is determined by measuring the voltage of the battery bank.
Question 2: Am I correct in my understanding that, if an outside device, such as an AC charger, is applying voltage to the bank and the Classic attempts to measure the voltage, it will appear to the Classic that the bank is charged?
Now, as has been suggested, I could purchase an inverter that has the ability to perform the role of the AC charger in the above scenario, and charge the bank. However, (assuming the answer to Question 2 is yes) unless they have the ability to communicate, I still have the problem of two devices (Inverter and Classic) attempting to charge the same bank and interfering with each other.
The inverter charger and Classic won't interfere with each other. They will charge to their programmed setpoints. If the inverter charger has charged the battery all the way then the Classic will just go into float soon. If the batteries were only charged about 80% with inverter charger the Classic would finish off the charge. Neither one is going to charge and will go to float once their setpoints are reached.
If you get new batteries all the same date of manufacture you will be okay. If you get used batteries of different dates you may not find very good performance. That being said I have a bunch of used AGM batteries on a 12v system but don't expect them to work to their rated capacity. But they work for the small loads I need . I have had individual batteries go bad though.
Lead acid batteries life span starts ticking as soon as the acid is in the cells no matter how little they have been used along the way.
QuoteThe inverter charger and Classic won't interfere with each other. They will charge to their programmed setpoints. If the inverter charger has charged the battery all the way then the Classic will just go into float soon. If the batteries were only charged about 80% with inverter charger the Classic would finish off the charge. Neither one is going to charge and will go to float once their setpoints are reached.
Ok, that's a piece of information I was missing. So far, I've just been looking at "dumb" inverters and "dumb" chargers, that don't have setpoints. All of the battery chargers that you find in your typical retail store will just keep charging until the battery is 100%. If the battery dips below 100%, they start charging again. With a charger like that on all the time, the Classic would never kick in.
Does anyone have any recommendations of companies that carry lines of inverters that have that capability, that will play nice with a Classic, and aren't 5 times what the Classic costs? I mean, I can get my butt off the couch and monitor the system manually quite a few times for the cost of some of the "Cadillac" inverters.
QuoteIf you get new batteries all the same date of manufacture you will be okay. If you get used batteries of different dates you may not find very good performance. That being said I have a bunch of used AGM batteries on a 12v system but don't expect them to work to their rated capacity. But they work for the small loads I need . I have had individual batteries go bad though.
Lead acid batteries life span starts ticking as soon as the acid is in the cells no matter how little they have been used along the way.
I appreciate for the reminder. I'm aware that used/old batteries will certainly give reduced performance. I would want to replace them as soon as the budget allows. In the meantime, I figure that something is better than nothing.
Darn - I wrote a long reply but it got lost. Basically I said a quality inverter charger that is sine wave and puts out a lot of amps will cost 3 or 4 times as much as the Classic. You could check out Samlex to see if they have a model , they are good quality and usually cost less than Outback, Magnum , or Schneider .
You could look for a used Trace non sinewave inverter charger - should cost a lot less and might do what you need if cost is an issue.