Author Topic: Unattended system for 5 months  (Read 289 times)

Dgrblu

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Unattended system for 5 months
« on: October 21, 2020, 02:11:35 PM »
New member. I purchase a cabin with a off grid system. 4.4 kw, six strings of three pv panels (825w/strg), Midnite combiner, Classic 150 CC, Magnum PAE sine inverter,  Magnum exspandable distribution panel, eight Crown CR435 six volt flooded wired in series 48v. 

My question is this, I snowbird in the winter and will be away from the cabin for 5 months. Do I just shut everything down and let the batteries sit for this amount of time. I have been told that the bank can sit idle for several months without them self discharging to zero in that time frame. I'm not liking this option for fear of a big freeze.

I was thinking of leaving the system intact except that I would turn the inverter output ac circuit breaker off and let the panels and classic do it's thing charging the batteries. Should I do this method,  should I do the following parameter changes;
EQ setting to 365 days(Not letting them EQ while away)
Bulk setting to 51 volts
Absorb setting to 51 volts
Float setting to 50 volts
Wanting to use the system to maintain the batteries only without boiling the water off during the 5 months away.

Any suggestions on how to 'winterize' my system without putting a big hurt on things.

TIA
Retired HVAC Tech.
4.4 Kw Off Grid system
6 strings of 3 panels (825w/string)
Midnite combiner
Classic 150
Magnum PAE sine inverter
Magnum distribution panel, expandable.

boB

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Re: Unattended system for 5 months
« Reply #1 on: October 21, 2020, 04:50:47 PM »
Welcome !

The others here will hopefully chime in here but I would vote for leaving the system on except for loads if you don't need any on.

If you can leave the inverter off, that's good too.

I guess the question is, will there be snow on the panels possibly for an extended time ?  If so, then that might require a bit of thought.  My reasoning there is that the Classic draws a little bit of power even at night.  Not much, maybe 3 or 4 watts but if there is no sun shining on the panels, then the batteries MIGHT drop down until the sun comes out.

I am guessing that the batteries are 12V ?   The Classic will run down to about 5 volts on the battery but there isn't any (if much) energy in the batteries at that level.

K7IQ

mike90045

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Re: Unattended system for 5 months
« Reply #2 on: October 21, 2020, 04:54:59 PM »
See if you can find a STANDBY float charge setting for your batteries, and use that, or maybe 0.1V higher.   Your charge controllers will consume a bit of power at night and you need to replace that usage.

Fully charged batteries will not freeze below the arctic circle (usually)
http://tinyurl.com/LMR-Solar

Classic 200| 2Kw PV, 160Voc | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph )| Listeroid 6/1, st5 gen head | XW6048 inverter/chgr | midnight ePanel & 4 SPDs | 48V, 800A NiFe battery bank | MS-TS-MPPT60 w/3Kw PV

boB

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Re: Unattended system for 5 months
« Reply #3 on: October 21, 2020, 05:40:40 PM »

One thing I worry about when leaving batteries unattended for long periods is that they can sulfate without an absorb charge once in a while.

For lead acid batteries of course.

Maybe Bulk Skip Days might be in order here, like, maybe once per week ??

Just a suggestion.

K7IQ

ClassicCrazy

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Re: Unattended system for 5 months
« Reply #4 on: October 21, 2020, 09:25:59 PM »
You might set up skip days , and set the equalize for every 10 days but set it to an absorb voltage and longer absorb time ( like an  hour or two ) so it does what Bob suggested - gets the electrolyte stirred up good to prevent stratification and sulphating .
I would turn the inverter off if not  using it.

I would just use normal float and absorb voltages , and as I said set the equalize to absorb voltage too every 10 days.  The thing is that with no loads the batteries are going to go quickly  to float every day - so that is why you also use skip days so that it will skip some days of trying to fully charge , but then you know every 10 days it will go to absorb for an hour or two and get the batteries topped up well and electrolyte mixed .

Larry
system one
Classic 150 , 5s4p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , 16s Calb 100AH LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batterie

Resthome

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Re: Unattended system for 5 months
« Reply #5 on: October 23, 2020, 12:41:00 AM »
You might set up skip days , and set the equalize for every 10 days but set it to an absorb voltage and longer absorb time ( like an  hour or two ) so it does what Bob suggested - gets the electrolyte stirred up good to prevent stratification and sulphating .
I would turn the inverter off if not  using it.

I would just use normal float and absorb voltages , and as I said set the equalize to absorb voltage too every 10 days.  The thing is that with no loads the batteries are going to go quickly  to float every day - so that is why you also use skip days so that it will skip some days of trying to fully charge , but then you know every 10 days it will go to absorb for an hour or two and get the batteries topped up well and electrolyte mixed .

Larry

Larry, I am curious why you would set the Classic up to Equalize at all. Especially at the Absorb voltage. If you set Skip Days to 9 days it will float for 9 days an on the 10th day it will do an charge to Absorb set point and terminate after the Absorb time ends if End Amps is turned off. Then it goes back to Float for 9 more days. Am I missing something?
John

10 x Kyocera KC140, Classic 150 w/WBJr, Link10 Battery Monitor, 850 AH @ 12v Solar One 2v cells, Xantrex PROwatt SW2000
Off Grid on Houseboat Lake Don Pedro, CA

boB

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Re: Unattended system for 5 months
« Reply #6 on: October 23, 2020, 01:19:33 AM »
You might set up skip days , and set the equalize for every 10 days but set it to an absorb voltage and longer absorb time ( like an  hour or two ) so it does what Bob suggested - gets the electrolyte stirred up good to prevent stratification and sulphating .
I would turn the inverter off if not  using it.

I would just use normal float and absorb voltages , and as I said set the equalize to absorb voltage too every 10 days.  The thing is that with no loads the batteries are going to go quickly  to float every day - so that is why you also use skip days so that it will skip some days of trying to fully charge , but then you know every 10 days it will go to absorb for an hour or two and get the batteries topped up well and electrolyte mixed .

Larry

Larry, I am curious why you would set the Classic up to Equalize at all. Especially at the Absorb voltage. If you set Skip Days to 9 days it will float for 9 days an on the 10th day it will do an charge to Absorb set point and terminate after the Absorb time ends if End Amps is turned off. Then it goes back to Float for 9 more days. Am I missing something?


And after the seventh day, it went to resting.

K7IQ

ralph day

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Re: Unattended system for 5 months
« Reply #7 on: October 23, 2020, 08:01:13 AM »
What a lot of cabin system owners do here in the cold, snowy north is, put a panel (or 2) on a vertical wall dedicated to the batteries.  No charge controller, just wired directly.  Not enough amps to damage things, but enough to keep from complete discharge.  No experience myself, just what I've heard over the years on forums.

ClassicCrazy

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Re: Unattended system for 5 months
« Reply #8 on: October 23, 2020, 11:10:14 AM »
You might set up skip days , and set the equalize for every 10 days but set it to an absorb voltage and longer absorb time ( like an  hour or two ) so it does what Bob suggested - gets the electrolyte stirred up good to prevent stratification and sulphating .
I would turn the inverter off if not  using it.

I would just use normal float and absorb voltages , and as I said set the equalize to absorb voltage too every 10 days.  The thing is that with no loads the batteries are going to go quickly  to float every day - so that is why you also use skip days so that it will skip some days of trying to fully charge , but then you know every 10 days it will go to absorb for an hour or two and get the batteries topped up well and electrolyte mixed .

Larry

Larry, I am curious why you would set the Classic up to Equalize at all. Especially at the Absorb voltage. If you set Skip Days to 9 days it will float for 9 days an on the 10th day it will do an charge to Absorb set point and terminate after the Absorb time ends if End Amps is turned off. Then it goes back to Float for 9 more days. Am I missing something?

What you say is a good idea  - I guess I was thinking there still might be some kind of small loads on the system and less skip days .

Larry

system one
Classic 150 , 5s4p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , 16s Calb 100AH LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batterie

mcsarge

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Re: Unattended system for 5 months
« Reply #9 on: October 29, 2020, 08:27:07 AM »
In the system I manage in Canada we do the following:

We disable the invertor so that only the charge controllers and my cellular coms gear and Raspberry Pis are powered (very low power requirements). We added what I can the "Winter Panels" which are a set of panels mounted on the wall of the cabin facing south-southeast under the eaves. They are wired to a separate charge controller to the battery pack. We get significant snow and it is not uncommon for the roof panels to be covered for a month at a time so we needed a way to replace the small amount of energy that the com system uses and keep the batteries charged when the main panels are covered. I have not programmed skip days, but I think I will. We had to get a person in Canada to go and top off the water in the batteries since the pandemic no one has been on the island for a year.

Matt
Off Grid Island in Ontario Canada (Beaverstone Bay)
Primary: Classic 150 + wbjr; 3s2p HES 270watt
Winter: SolarBoost 50 MPPT (into wbjr); 2 x Sharp NE-80EJEA 80watt
Pack: 4s4p US2200 FLA 6V for 24V pack
Inverter/Charger: Trace DR2424
Call Sign: KG4EUF

FNG

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Re: Unattended system for 5 months
« Reply #10 on: November 05, 2020, 09:26:00 AM »
What a lot of cabin system owners do here in the cold, snowy north is, put a panel (or 2) on a vertical wall dedicated to the batteries.  No charge controller, just wired directly.  Not enough amps to damage things, but enough to keep from complete discharge.  No experience myself, just what I've heard over the years on forums.

I would caution on this myself, A full battery will not take much current to raise its voltage to a dangerous area. I would use a simple PWM style controller just as a safety net myself