Battery charging at well below C/8 rate

[russ]

I removed it - there was the list and the complaining.

[SunEagle]

Or research for somebody that actually wants to understand what they are buying... is that really so rare?

I have no issue with someone trying to understand the pros and cons of solar and even using that information to promote sales. Is is better to have the truth out there then falsehoods.

I was just making a statement that when I did see your post is had a list of topics and now that post was gone. I didn't know if you removed it or it was removed by the Admins.

[kevinc_63366]

What happened to his last post with the list of topics he was looking to get answers for?

Seems like research for a Sales Document to help people to try and understand the pros and cons of an off/on grid solar pv system.

Or research for somebody that actually wants to understand what they are buying... is that really so rare?

[SunEagle]

What happened to his last post with the list of topics he was looking to get answers for?

Seems like research for a Sales Document to help people to try and understand the pros and cons of an off/on grid solar pv system.

[russ]

Kevin - Last chance - either participate and try to learn something without being an all knowing wise ass or you won't be around.

[Naptown]

Kevin
Do you realize that by doing this off grid you are not only adding substantially to the cost of install but also throwing away a potential $2.00 a watt utility rebate? That's over 12K on the system you proposed initially.
Would you like to talk more about hybrid systems that I have been suggesting to you?

[Sunking]

Request for guidance were met with "Pay me $5000 and I'll tell you".

That was tongue-in-cheek humor you missed. If I were to try to sell anything on here I would be booted off. With htat said I am a professional electrical engineer with 33 years of experience. What I have told you so far will save you some $15K.

[russ]

Strange group. I specifically never said why I wanted off-grid, you just assumed.

To quote you from the first post in this thread "Trying to fit all the pieces of an off-grid system into my head. Yeah, its hurting...". Sounds like off grid to me.

When someone shows up playing wise guy they usually have a tough row to hoe.

[kevinc_63366]

Huh is this the same person who said:

You got what you asked for now you complain and pout? You keep changing your story.

First you want to build a community off-grid solar farm to sell to your neighbors having a Green Dream and making a profit.
Second it is your farm you want to build off-grid.
Third, then it is not for you but a friend you are helping out.

Quit the BS Keven. You should be thanking us for saving you a fortune busting your ideological Green Bubble. Off-Grid Solar is the absolute last resort if there are no other options. You have a lot of other much less expensive options. Now that you know and still want to pursue Off-Grid quit the BS, ask intelligent questions, and listen to pros and experts.

Good Luck.

Strange group. I specifically never said why I wanted off-grid, you just assumed. I stated up front that I was building a workshop on my farm, yet somehow you concocted that I was going to try and sell power to my neighbors? I saw, and ignored, the comments about having a stupid client, never claimed I was working for anyone else. You make assumptions and then claim I stated them? Why I want off-grid is not your concern. Request for guidance were met with "Pay me $5000 and I'll tell you". Thought this was what the byline claimed - a Solar Energy Discussion Community, not a sales oriented "We are smarter than you so shut up, listen, and pay us" forum.

Good luck to you too.

[Sunking]

And if this belittling rather than discussion is all I can expect here, I guess I made a mistake joining.

Huh is this the same person who said:

Ok folks, please rip this apart... everything else is fair game.

You got what you asked for now you complain and pout? You keep changing your story.

First you want to build a community off-grid solar farm to sell to your neighbors having a Green Dream and making a profit.
Second it is your farm you want to build off-grid.
Third, then it is not for you but a friend you are helping out.

Quit the BS Keven. You should be thanking us for saving you a fortune busting your ideological Green Bubble. Off-Grid Solar is the absolute last resort if there are no other options. You have a lot of other much less expensive options. Now that you know and still want to pursue Off-Grid quit the BS, ask intelligent questions, and listen to pros and experts.

Good Luck.

[kevinc_63366]

With your poor solar insolation in Missery winter, your panel wattage will be way above minimum C/12 and below the max of C/8. For 8 Kwh in winter you need a 48 volt 820 AH battery. To generate 8 Kwh on Xmas day will take a 3.75 Kw solar panel. That 3.75 Kw panel at 48 volt battery will generate 80 amps of current.

80 amps of current on a 820 AH battery is C/10 which is the sweet spot perfect range. You owe me $5000. I have now saved you $15,000.

And if this belittling rather than discussion is all I can expect here, I guess I made a mistake joining.

Good night. Good bye.

[Sunking]

With your poor solar insolation in Missery winter, your panel wattage will be way above minimum C/12 and below the max of C/8. For 8 Kwh in winter you need a 48 volt 820 AH battery. To generate 8 Kwh on Xmas day will take a 3.75 Kw solar panel. That 3.75 Kw panel at 48 volt battery will generate 80 amps of current.

80 amps of current on a 820 AH battery is C/10 which is the sweet spot perfect range. You owe me $5000. I have now saved you $15,000.

[kevinc_63366]

Hi all -

Trying to fit all the pieces of an off-grid system into my head. Yeah, its hurting...

Current problem is batteries. No issue figuring out required capacity for 5 days run time or anything like that. Recharging them after 5 days of run time is a problem though. Obviously the PV array isn't going to magically come up with 5X extra power to recharge them in a day or would the normal charge controller be able to handle the current to do so.

So in comes a backup generator to help out - probably starting whenever the bank dropped below 75% or so (day 2 or 3 of an outage, or day 20 of on-again, off-again sunlight that has just slowly depleted the batteries). Nice thing about generators, they can run 7x24 if rigged to fuel, like the propane tank I would be heating from. For sake of conversation, lets presume I have 4800W array, charging away at 48V, with concurrent usage (e.g. almost zero) such that the charger can actually charge at 80amps. At C/8 charging rates, that means I could fully charge 640amp hrs of battery from dead, double that capacity if they were 50% charged - using VERY simple, I know inaccurate, math. That would take about 2 days to actually happen via the PV array, since it would only be charging about 4 hours a day.

Question 1: Do the batteries care, long term, that they would get a charge current for 4 hours, then a small drain, then another charge current vs. being fully charged all at once? I know lead-acid doesn't suffer from any form of memory (beyond that associated with damage from deep discharges).

Question 2: Do the batteries care if they are charged at C/16 or C/32 instead of C/8? e.g. Instead of using a 4800W array, could I use a 1200W generator and just run it 7x24, effectively providing a shorter overall charging period but at a lower rate?

Question 3: How do most charge controllers feel about being starved for charging power? I'm guessing they would consider that normal business since 20 hours/day they don't have it anyhow.

Question 4: My current inverter choice has a charge controller powered by either a generator and/or grid. Is that charge effort going to conflict with the normal PV supplied charge controller when I power up the generator?

Thanks in advance.