The system currently has a Magnum mini-panel, Magnum 4K inverter, Classic 150 and 24 volt battery pack (Rolls). The owner of the solar system was asking about adding another 24 volt battery pack for increased performance. The batteries used in the original system are no longer available.
What is the best method to add a second 24 volt pack? Would it entail adding a second Classic 150? How difficult is it to add a second Classic 150 to a system? The space in the Magnum mini-panel is very cramped and extremely difficult to work in -- what about some kind of break-out box?
Sure would appreciate your advice.
I am curious what kind of increased performance they are talking about ?
To be able to run longer during cloudy periods or on short winter days ?
You can't add more batteries because it is not good to mix batteries of different age. You would have to replace the batteries with larger pack . And if you did that then you want to have the PV capacity to be able to charge it up.
If the present Classic is maxed out on how much PV it can handle -- then you could add another Classic and more PV on it. Just get another box to mount the new classic on - Midnite has a number of them - I use the Midnite MiniDC box - but you wouldn't need the inverter breaker that comes with it. I like that box because it has the place to install shunt, and easy to follow schematic on wiring it up - has a place for the breakers from PV and Bat to Classic which I install on top of the box and the knock outs line up with the holes in bottom of the Classic.
http://www.solar-electric.com/residential/installation-supplies/ac-dc-disconnects.html?manufacturer=MidNite+Solar
You would wire the second Classic into the existing battery and connect the two Classics up in Follow Me mode. That would give the existing system more current to use when the sun is shining and the batteries are full. It would also charge the batteries more during low light times.
But not sure if that is what owner is thinking - need clarification on what they mean by increased performance ?
Larry
Quote from: ClassicCrazy on July 20, 2016, 10:00:07 PM
I am curious what kind of increased performance they are talking about ?
To be able to run longer during cloudy periods or on short winter days ?
Please excuse my poor communication skills.
This hardware was bought as a package by a relative a few years ago and languished in a warehouse until a few months ago. I was "drafted" to help install the system (ex-military communications maintenance). I know very little about PV solar. The system is up and running but battery capacity is down due to sulfated batteries. We are actively working that issue and SG's are almost in the normal range. The system has 2000+ watt of PV mounted on non-tracking poles. Battery capacity is (4) 6V Rolls 400 AH wired for 24 volts. These batteries were about $360 each.
Latest test several weeks ago gave us ~4 hours of 3000 watt load until the batteries reached (preselected) 50% life remaining and the inverter shut down. The owner wants more time. But the problem is, we will never match the characteristics of these batteries. So ...... is the solution another battery bank, another Classic 150 and split off half the PV? The system owner has expressed an interest in adding another 24 volt pack of the Rolls S550 to add capacity.
I'm flying blind and guessing. Is there any place to look at schematics of various systems?
Quote from: ClassicCrazy on July 20, 2016, 10:00:07 PM
You can't add more batteries because it is not good to mix batteries of different age. You would have to replace the batteries with larger pack . And if you did that then you want to have the PV capacity to be able to charge it up.
If the present Classic is maxed out on how much PV it can handle -- then you could add another Classic and more PV on it. Just get another box to mount the new classic on - Midnite has a number of them - I use the Midnite MiniDC box - but you wouldn't need the inverter breaker that comes with it. I like that box because it has the place to install shunt, and easy to follow schematic on wiring it up - has a place for the breakers from PV and Bat to Classic which I install on top of the box and the knock outs line up with the holes in bottom of the Classic.
http://www.solar-electric.com/residential/installation-supplies/ac-dc-disconnects.html?manufacturer=MidNite+Solar
You would wire the second Classic into the existing battery and connect the two Classics up in Follow Me mode. That would give the existing system more current to use when the sun is shining and the batteries are full. It would also charge the batteries more during low light times.
But not sure if that is what owner is thinking - need clarification on what they mean by increased performance ?
Larry
Thanks for the info ...... I'll definitely look over that box. Original system designer said the PV should be able to charge these batteries in ~ 3 hours. The costs of a bigger battery pack is prohibitive at this time.
Any other ideas or thoughts would be very much appreciated.
you could look at 6V 200ah golf cart batteries, about $100 or so each. 8 would get you 24v @ 400ah @ $800
and have only 2 parallel strings
If your battery pack was good then you would have around 9600 watts capacity , though you don't want to use more than 3/4 or half for battery longevity .
You said you ran the 3000 watt inverter for 4 hours - but what was the load ? It couldn't have been full capacity of the inverter or that would have been 12,000 watts.
I guess you need to do a load test with known load to determine how good the batteries still are. If they have been sitting around for years with no charge and are as sulfated up as you said - it is probably time to get new ones. What was the battery voltage when you started out ?
The original dealer probably stretched the truth on how fast you can recharge the batteries. With lead acid batteries you can't dump everything in all at once . When the batteries get up to their absorb voltage setting then the controller tapers down the current . So it all depends on how much energy was used the night before. It takes awhile to get them fully charged no matter how large the PV system is. With lithium cells you can dump a lot of power in all at once, but there are a lot of other intricacies with maintaining lithium batteries correctly.
Larry
Quote from: BAndrews on July 20, 2016, 11:13:56 PM
Quote from: ClassicCrazy on July 20, 2016, 10:00:07 PM
I am curious what kind of increased performance they are talking about ?
To be able to run longer during cloudy periods or on short winter days ?
Please excuse my poor communication skills.
This hardware was bought as a package by a relative a few years ago and languished in a warehouse until a few months ago. I was "drafted" to help install the system (ex-military communications maintenance). I know very little about PV solar. The system is up and running but battery capacity is down due to sulfated batteries. We are actively working that issue and SG's are almost in the normal range. The system has 2000+ watt of PV mounted on non-tracking poles. Battery capacity is (4) 6V Rolls 400 AH wired for 24 volts. These batteries were about $360 each.
Latest test several weeks ago gave us ~4 hours of 3000 watt load until the batteries reached (preselected) 50% life remaining and the inverter shut down. The owner wants more time. But the problem is, we will never match the characteristics of these batteries. So ...... is the solution another battery bank, another Classic 150 and split off half the PV? The system owner has expressed an interest in adding another 24 volt pack of the Rolls S550 to add capacity.
I'm flying blind and guessing. Is there any place to look at schematics of various systems?
Quote from: ClassicCrazy on July 20, 2016, 10:00:07 PM
Thanks for the info ...... I'll definitely look over that box. Original system designer said the PV should be able to charge these batteries in ~ 3 hours. The costs of a bigger battery pack is prohibitive at this time.
Any other ideas or thoughts would be very much appreciated.
Quote from: mike90045 on July 21, 2016, 03:16:25 AM
you could look at 6V 200ah golf cart batteries, about $100 or so each. 8 would get you 24v @ 400ah @ $800
and have only 2 parallel strings
The numbers look good to me and I'll pass that on. The immediate problem for me right now is how to add a second pack with different charging specs (float, bulk absorb, etc) and ensure both packs get their full charge for long life.
Quote from: ClassicCrazy on July 21, 2016, 06:14:13 PM
If your battery pack was good then you would have around 9600 watts capacity , though you don't want to use more than 3/4 or half for battery longevity .
You said you ran the 3000 watt inverter for 4 hours - but what was the load ? It couldn't have been full capacity of the inverter or that would have been 12,000 watts.
The inverter is a 4000 watt model (MS4024PAE). During the test, we put a 1500 watt resistive load across each leg of the 220 output. We ran this 3000 watt load for about 4 hours before the inverter cut off at the 50% remaining setting. The solar panels were taken offline during the test to simulate night. I don't understand how that's possible with a 9600 watt battery pack. Clearly there is a mistake here somewhere. I'll have to pay more attention with the next test.
Quote from: ClassicCrazy on July 21, 2016, 06:14:13 PM
I guess you need to do a load test with known load to determine how good the batteries still are. If they have been sitting around for years with no charge and are as sulfated up as you said - it is probably time to get new ones. What was the battery voltage when you started out ?
The original dealer probably stretched the truth on how fast you can recharge the batteries. With lead acid batteries you can't dump everything in all at once . When the batteries get up to their absorb voltage setting then the controller tapers down the current . So it all depends on how much energy was used the night before. It takes awhile to get them fully charged no matter how large the PV system is. With lithium cells you can dump a lot of power in all at once, but there are a lot of other intricacies with maintaining lithium batteries correctly.
Larry
The batteries sat for a little more than 2 years. I don't remember the starting voltage but one battery had a SG reading on all cells that was not even on the scale of the specific gravity meter. We are working the batteries with a desulfator charger at night and the process appears to be slowly working. The SG's are slowly rising and we've now hit ~1.25 for most cells. Rolls says 1.265 is fully charged. We've got our finger crossed.
We try another test soon and pay more attention to the details. I appreciate the info.
Does your system have a shunt and software that determines SOC - state of charge ?
Larry
Quote from: ClassicCrazy on July 22, 2016, 02:22:30 AM
Does your system have a shunt and software that determines SOC - state of charge ?
Larry
I believe it has two shunts (if thats the right term). One got disconnected from the battery pack several weeks ago in a move -- and I reinstalled it today after reading your post. There is a shunt in the mini-panel too. The only software currently running is the ROM's in the Classic 150 and the magnum control panel interface.
I was checking out the menu entry for SOC in the magnum panel interface a few weeks back but did not come to any conclusions. Thought I would get back to it.
Sounds important?
If you get SOC working you can monitor exactly how many amps go in and out of the battery. So for your 400 ah battery you could set it to 200 ah capacity as a benchmark , let it get full to 100% , and from then on you will see for example you took out 40% and next day only filled up 30% it would show you SOC 90% .
Midnite has an inexpensive add on that will do that - it is called the Whizbang . Look it up and you will want to get one I am sure. One thing to note on your shunt - you should only have one side of it connected to the battery negative - everything else is connected to the other side of the shunt so it can tell everything going in and out of the battery. You may want to see what size shunt you have in there but more than likely with a large system like you have it is 500 amp shunt . Even if there are other things connected to the shunt you can still hook up the whizbang and the existing stuff .
This is what I am talking about for shunt
http://www.solar-electric.com/mkb-500-50.html
It is also going to show you the real time amps going in and out of the battery .
Larry
Quote from: BAndrews on July 21, 2016, 07:40:48 PM
The batteries sat for a little more than 2 years. I don't remember the starting voltage but one battery had a SG reading on all cells that was not even on the scale of the specific gravity meter. We are working the batteries with a desulfator charger at night and the process appears to be slowly working. The SG's are slowly rising and we've now hit ~1.25 for most cells. Rolls says 1.265 is fully charged. We've got our finger crossed.
We try another test soon and pay more attention to the details. I appreciate the info.
Tonite, the specific gravity test shows all cells reporting at 2.65 or higher. Several cells report 2.70. That's worrisome.
I'm still searching for the holy grail of adding a second power pack with different specs and ensuring all packs get the needed treatment (bulk, absorption, equalization, etc) for long life. I'd pay for a professional consult from an acknowledged expert. Anyone?
Quote from: BAndrews on August 01, 2016, 09:05:37 PM
Tonite, the specific gravity test shows all cells reporting at 2.65 or higher. Several cells report 2.70. That's worrisome.
I'm still searching for the holy grail of adding a second power pack with different specs and ensuring all packs get the needed treatment (bulk, absorption, equalization, etc) for long life. I'd pay for a professional consult from an acknowledged expert. Anyone?
Hi Bandrews,
In the quote above, what is worrisome about 1.265 or 1.270 SG readings ? Is it the 1.270 ?? There is a reasonable tolerance on Hydrometers, and reasonable variation in SGs among cells, especially as batteries age. As you cycle batteries they would normally stabilize. But total variations across all cells of a battery bank of 20 points or so is not uncommon.
There is a relatively small temperature compensation factor when compensating SG s for temperatures above or below 77 F (25 C). This is probably not the reason that there are small variations between cells in a battery bank.
If you have questions about Surrette batteries, send them an e-mail or call them. They do a great job of supporting their customers, and DO know their products.
FWIW, Vic
Quote from: Vic on August 01, 2016, 09:40:11 PM
Quote from: BAndrews on August 01, 2016, 09:05:37 PM
Tonite, the specific gravity test shows all cells reporting at 2.65 or higher. Several cells report 2.70. That's worrisome.
Hi Bandrews,
In the quote above, what is worrisome about 1.265 or 1.270 SG readings ? Is it the 1.270 ?? There is a reasonable tolerance on Hydrometers, and reasonable variation in SGs among cells, especially as batteries age. As you cycle batteries they would normally stabilize. But total variations across all cells of a battery bank of 20 points or so is not uncommon.
There is a relatively small temperature compensation factor when compensating SG s for temperatures above or below 77 F (25 C). This is probably not the reason that there are small variations between cells in a battery bank.
If you have questions about Surrette batteries, send them an e-mail or call them. They do a great job of supporting their customers, and DO know their products.
FWIW, Vic
Thanks Vic -- I appreciate the info. The 1.270 values were indeed what was giving me pause since Rolls said 1.265 was full charge. Both of the hydrometers we use are temperature compensated so I think we are ok there.
These Surette batteries have a high quality feel to them, no doubt the company is at the top of their game. Also, picked up some Flow-Systems battery caps and they appear to be working a treat -- no more "misting" under heavy charge.
Wish I knew a lot more about this tech -- rocket science has nothing on solar. :-)
Quote from: BAndrews on July 21, 2016, 07:40:48 PM
The inverter is a 4000 watt model (MS4024PAE). During the test, we put a 1500 watt resistive load across each leg of the 220 output. We ran this 3000 watt load for about 4 hours before the inverter cut off at the 50% remaining setting. The solar panels were taken offline during the test to simulate night. I don't understand how that's possible with a 9600 watt battery pack. Clearly there is a mistake here somewhere. I'll have to pay more attention with the next test.
Battery capacity is (4) 6V Rolls 400 AH wired for 24 volts
So 3000 watts load on a 4 hour time is being supplied from 24Vdc 400ah battery pack is quite a hard load test.
That is without losses , we don't get all math to balance out 100% (we call that loss of inefficiency ) every change , wire distance (voltage drop ) all adds up . FLA's cells are close or around 85-95 % depends on age and abuse etc.
As posted before The classic on a Whizbang JrWhizbang Jrhttp://www.midnitesolar.com/productPhoto.php?product_ID=519&productCatName=Charge%20Controllers%20-%20Classics&productCat_ID=21&sortOrder=9&act=p] http://www.midnitesolar.com/productPhoto.php?product_ID=519&productCatName=Charge%20Controllers%20-%20Classics&productCat_ID=21&sortOrder=9&act=p]Whizbang Jrhttp://www.midnitesolar.com/productPhoto.php?product_ID=519&productCatName=Charge%20Controllers%20-%20Classics&productCat_ID=21&sortOrder=9&act=p (http://www.midnitesolar.com/productPhoto.php?product_ID=519&productCatName=Charge%20Controllers%20-%20Classics&productCat_ID=21&sortOrder=9&act=p) with the shunt will let you know the amps in & out as work out the required battery charging voltages & times ..
VT
Got a Whizbang on order and should receive it next week. Will get some before and after install shots. Prior to setup of this system, I've never worked on equipment this crowded, I might have to relocate the shunt/Whizbang outside the Magnum mini-panel.
Also, have built a 1 foot extension cord with the hot wire showing and have a clamp-style ammeter to determine load. Perhaps in a week or 10 days I can post the results......
Great & now the Amps will make math Sense , and then many can help the math equation much easier