Seeking advice from the collective for my off grid solar setup. I'm in the process of building my off grid home and am wondering pros/cons of having a separate structure for housing the battery(8-L16 wired to 24v), charge controller(Classic 150), and inverter(MS4024PAE 120/240V). The solar array (rated 1740W) is planned to be ~75ft away from the electrical access to the home.
I would like to store all the equipment under the solar array in a small shed and run 240VAC (75ft run) to the home electrical panel. I am concerned about the lower capacity of the batteries in winter temperatures with the lows -5 to 10F and highs 25 to 35F. Highs the rest of the year is in the 60 to 80F so not to concerned about over heating.
Would it be better to store the batteries in a more temperature controlled environment like the home garage?
Is lower capacity the only negative to keeping the batteries so cold?
What I am trying to avoid is the wire requirement for running DC a long distance and not having to take up space in the garage. My thinking is to keep the DC runs from the module to charge controller and battery to inverter as short as possible and use the 240VAC on the long run to the home.
Comment appreciated
Ray
My thoughts .
Yes it is nice to have all the electronics in it's own building. But it depends on your living space . Mine is small so the inverter and batteries are in the shed - which is unheated in Wisconsin in winter so batteries are cold. They are derated for capacity. Part of the reason I selected my last set of batteries as a type of gel cell called lead crystal type was there better performance at very cold conditions. The jury is still out for their life longevity though it is claimed to be just about as long as flooded lead acid. That is as long as I keep to using only 20% of their capacity. It is nice to not have to mess around with all the watering and dealing with acid samples of flooded.
But I would say that the main reason not to have the electronics inside if they are withing earshot is the noise of fans and electrical humming from controller and inverter. Plus you get a better margin of fire safety having all that stuff out of the main dwelling though that isn't a big worry if the system is installed properly. If I had a basement I would have all the batteries and electronics down there as long as I couldn't hear it .
If you haven't bought batteries yet there was some new type coming on the market - forget what they were called but someone posted info on them on forums here - maybe in off topic section. They were by East Penn Deka . I would check those out for cost performance value.
Regarding the DC - if you wire up the PV for higher voltage then that makes the wire gauge smaller going from PV to controller. Though ideally it is nice to keep PV closer to battery voltage for better controller efficiency . Those are all part of your design considerations. Also if you plan on having your batteries last a long time design your system to only use 20% of their capacity for lead acid ( took me a few sets of batteries to figure that out ).
Yes you don't want to have the batteries too far away from the controller and inverter since the wiring gauge would be expensive and limiting.
You will just have to do some wire loss investigating on placement of your PV to the controller to determine you best scenario.
Larry
These points you brought up is why I would like to house everything in a shed. Plus I think keeping efficiency as high as possible on the DC side will help the most on short cloudy winter days. Right now I have 6awg for the PV to controller for a 25ft run after doing the calculation for the coldest temp and VOC.
Already have Deka 8L16 batteries that are C/20 rated at 370Ah strung in series/parallel for 24v 740Ah @25C. I failed to set the temperature compensation correctly on the Classic 150 at initial set up and realized my mistake when I noticed a difference in % discharged and voltage. I don't think I discharged past 30% for an extended period of cycles so I'll run an equalizing charge and perform a thorough battery check. Still learning as I go along and expect to make some mistakes hopefully not very expensive ones.
Ray
You should have -3 mv for the temp compensation.
Pay particular care to how your parallel wiring is with the two battery sets so they get even charge discharge.
http://www.smartgauge.co.uk/batt_con.html
You will have to tweak the efficiency settings on the SOC to make it match up - and you should confirm with using specific gravity readings.
I am assuming you are using ending amps to terminate the Absorb and go to Float. The Absorb voltage setpoint and the ending amps may need to be tweaked in colder weather - depends some on your loads and charging.
Here is info on how to determine ending amps and other useful info - look under CLASSIC CHARGE CONTROLLER - Features and Programming
http://www.midnitehelp.com/
My advice is to put the maximum amount of PV on your controller as possible - seems like it has room for more . I just added a second Classic to my system and almost doubled the PV and it helps out so much in the winter short days and overcast days . Cuts down on generator run time .
Larry
Thanks for the battery connection information. All my series cables are the same length but looks like I need to move one of the terminal cable to the other bank for better equalization. Right now the +/- cables to the E-panel is hooked to one bank.
The terminating amp from absorb to float I believe is controlled by the Whizbang JR which has a "Battery capacity temperature compensation" setting that I am confused about. This is what I never set at initial setup. It gives me a range of 0%-3% and says typical lead acid batteries are 1% so I set it to that. Do I take the -3mV/cell/C and figure out the % difference from 25C?
I used this chart for setting the voltage for Absorb/Float/Eq.
https://www.mkbattery.com/application/files/7015/3333/2576/Renewable_Energy_Charging_Parameters.pdf
My current setting is: 28.8V Absorb/ 27.6V Float/ 30V Eq. which is the lower voltage in the range given by Deka. Do I need to tweak these for temperature variations or does the controller with the whizbang do it for me?
Thanks for you help
Ray
Ray you are confusing two different temperature settings. One is temperature compensation to automatically change the charging setpoint. The other is used in SOC calculation to estimate SOC by derating the capacity when cold.
The important temp comp setting on MNGP is under Battery Menu T-comp -mv/Deg C/cell and that is where you put in the -3 mv . It is on Config Tech of the Local Status app . The other one I am not finding right now on the MNGP but it is also on the Local Status Tech menu Battery Status menu and I left mine at 1% /deg
And yes that MK battery document would be the correct one - you may need to raise the voltage a bit higher in the range for cold weather if you notice the batteries not filling up - or decrease the ending amps a bit . or maybe some of both . You need to confirm with SG readings of electrolyte to match so that when it says 100% SOC the SG also says full. You may need to raise or lower the battery effiency of the Battery Status menu to match your batteries- look in some other forum posts and see what Vic recommended for flooded lead acid - I don't remember - maybe 88 or 90 %?
Larry
Larry
-3mV is set in T-Comp menu. The WBjr "Battery SOC setup" has 740 as my capacity and 92% as efficiency. and "Battery capacity temp comp" as 25C reference and 1% change/degree. I am confused as how this number is calculated since it is adjustable in 0-3% in .1 increments.
Also the "Limits" menu has a min/max voltage for temperature compensation which is still set as the default min-26.4v max-30.0v. Do I leave these as they are?
Ray
My batteries and inverter live in one shed, my generator lives in another
because of cold, I allowed for higher battery capacity, for when cold takes away capacity.
Quote from: rmak on December 07, 2018, 10:00:39 PM
-3mV is set in T-Comp menu. The WBjr "Battery SOC setup" has 740 as my capacity and 92% as efficiency. and "Battery capacity temp comp" as 25C reference and 1% change/degree. I am confused as how this number is calculated since it is adjustable in 0-3% in .1 increments.
Also the "Limits" menu has a min/max voltage for temperature compensation which is still set as the default min-26.4v max-30.0v. Do I leave these as they are?
Ray
Hi Ray,
Deka may have info on the Capacity-derating verses temperatures below the 25C Reference temperature. This is used in calculating SOC and Remaining Capacity. Have always used 1%, as SOC and remaining capacity are approximations, anyway.
In the Charge>Limits menu, those Min/Max values is where the Classic will Limit its Temperature Compensation of Absorb, Float, and the EQ voltages (if you have opted to compensate Veq. These Limits are probably more useful for AGM, Gel, and Li batteries. IMO, you will want to set the upper voltage Limit a bit above the compensated voltages for the lowest temperature that you would ever expect the battery temperature to be at the battery location. For the lower voltage Limit, similarly, you would want to set this to a voltage that represents the compensation for a battery temperature as high as you would ever expect the batts to experience. Use the -3mV/C and your expected battery temperatures to calculate these. UNLESS there are specific Limits that Deka specifies for your batteries.
Think that Classic Crazy Larry has covered the other questions.
You will want a good Hydrometer, with a float mechanism that is calibrated with numbers for SG readings, NOT one with floating colored balls, or a $6 one with a cheesy plastic pointer.
An Auto Parts store glass Hydro, with a glass float should be OK, or the HydroVolt, which is very easy to read.
ALWAYS, RINSE, RINSE, ... AND RINSE YET AGAIN your Hydrometer, with Distilled Water, after each measuring session. This will help keep your Hydro accurate.
You will probably want a battery Logbook to record SG readings, charge voltage & time settings, EQ time and voltage, etc. It is good to number each battery and (usually) letter each cell of each battery (A, B, C) to keep track of battery health and trends.
Install all Battery Temperature Sensors (BTS) on a single battery in the center of the bank, about half-way down the side of the case. You could place a square of Styrofoam(r) over the BTSes, with a small area hogged-out of the side of the foam that is over the BTSes, to help remove the effects of ambient temperature on those sensors.
FWIW, Vic
... Will add a couple of things ...
In addition to your batteries loosing Capacity in cooler conditions, there could be some chance of the batteries freezing. This can be particularly the case for sites that are not attended during much of the Winter (and therefore you might be unable to increase battery SOC, or to warm them when you are not there).
Also it is common for Lead Acid batteries to need a number of discharge/charge cycles for charge parameters to stabilize -- guessing that your batteries are fairly new.
Vic
Vic Never had my batteries freeze here in Wisconsin. They would have to be really run down to do that - like just about dead before they freeze. If a place was unattended up in the north here it shouldn't have any big loads on it that could cause that to happen if the sun wasn't out for a week.
Larry
So I think I need to get back to the basics of proper battery care as it looks like I did not do my best to learn the basics of setting up the CC.
System as follows:
4-290W modules (initial to present. Adding 2 more)
8-Deka L16 batteries wired to 24V
Classic 150
WBjr
Magnum 4024PAE
Midnite E-panel
Installed 5/18 with these settings when it was 70-80F
Capacity=740 Efficiency=94
Absorb=28.8V Float=27.6V EQ=30V
Absorb time=2hr EQ time=2hr
I think I damaged the batteries because I overlooked setting the endtime and temp compensation. :-[ Now its averaging a high of 32F here with lows around 0F. I started to check the health of the system when the inverter cut out (set @ 24.5V) even though I showed 82% SOC(the reason why I initially asked about cold battery capacity). That day the batteries went to 100% and to float. I checked the water level and evened them all to the bottom of the tube. I set the temp comp and charged the next day checking the SG with the HydroVolt periodically and got up to high readings of 1.220-1.245 before the sun went down. The volts were 25.5v @32F/0C (multimeter) after an hour being at rest. With correction of temp (.003v x 12cells x 25C=.9v) I should see 26.3v at 100% SOC.
So am I correct in that the batteries were never charging fully when the high temps started to drop because I did not set the temp comp (-3mv) correctly and will I ever see full charge 1.260-1.270SG?
How should I proceed with the batteries?
Thanks for any help.
Ray
If you have a generator use that on a sunny day to help get your batteries charged up , then you can let the solar do equalizing charge . Keep equalizing to see if you can get the SG up to recommened value for 100% - or at least get the lower SG cells up more even with the others.
Lead acid batteries are somewhat forgiving if they haven't been left over discharged for too long of a time . You may get them back to good enough service.
Yes the temperature compensation for charging may have been what got you if it wasn't on. That is because cold batteries wouldnt be full even if you thought they were so would keep going lower and lower with the loads on it. The two hour absorb time would not be long enough to recharge the batteries if they were really low and with your limited PV.
You don't have enough PV for the amount of batteries and size inverter you have . If you don't have a generator you need to get one and use is often as needed to fill up your batteries during the winter .
Larry
I've been charging with a portable generator (2000w taxed at 10K altitude) through the inverter at 29.8v. Should I be setting the charger with Eq voltage at 30.9v+.9v (comp for temp)? Not sure if the Magnum charger compensates for temperature. The SG numbers are starting to even out but still below full charge levels. Is it OK to check SG while they are charging?
The PV seemed to do fine for the low power my RV was using during warmer summer and fall months but with the incorrect settings, less sun during the day, colder temperature and running the RV furnace really depleted my battery. I guess the bright side would be I had the inverter set to shutdown at 24.5V to bring the problem to my attention. I will be adding modules as I find a more permanent place for them as soon as the building is built. Final array will be 3 sets of 3 modules which according to the calculator is the max for the classic 150.
Very steep learning curve that I need to set aside some time to digest. Thanks for the help.
Ray
okay -I didn't know you were in RV.
yeah gotta have the heat ! The old camper heaters used to not need any power and just heated the air . But I know the new ones have forced air and igniters and stuff that sucks power.
I don't know Magnum stuff - you will have read up - but if it doesn't have a remote temp sensor that you put on the batteries it won't do the job until you get one. That is why I suggested use the generator to do that bulk and then you can use the Classic to do the equalizing. I am guess you have the temp sensor on the classic installed in the battery box.
Best way to learn is by doing it ! I killed my first battery long long time ago in RV in winter - simple controller and it did not have temperature compensation.
Larry
The blower motor for the propane heater runs off on 12v but being well below freezing over night I don't want the RV batteries (2-12v Interstates) going completely dead since the furnace comes on quite a lot. I don't think the charger in the RV is really efficient either so I'm loosing quite a lot there too.
The Magnum does have a preset Flooded cell setting and a user programmable setting too. It does have a battery temperature sensor but I don't think it compensates while charging because it shows the same voltage I set it at. So I set the custom setting voltage/time on the Magnum to match the setting I was getting off the classic which does have a temperature sensor.
I'll just keep charging until I see consistent SG in all the cells then set the absorb end time/amp properly. I have a little more time now to read through the forum and educate myself better for caring for my system.
I think the Classic is a wonderful controller but you know what they say about making things idiot proof...
Ray
not sure what you mean about the charger on the RV not being efficient ?
Do you mean that you are running AC off the inverter to a dc converter to then run a DC blower motor ?
Yeah that would not be very efficient since your inverter running a small load might loose as much power in the process as it would take to run the motor - and then if it is going into a converter that would be another 20% or more lose .
So best bet is figure out what DC voltage your blower needs and then run it directly off DC . If it is 12v and you have 24v system then you would still need a dc to dc converter to take 24 to 12. Samlex makes some good ones that aren't too expensive - I use a SDC-23 model here - depends on how many amps you need - might need the next size bigger one if 20 amps isn't enough .
So yeah get all your essential loads on DC direct so you can shut that inverter off to save power when you don't need it and you will do a lot better.
Larry
Converting from DC to AC back to DC is probably very inefficient. Haven't thought about a DC/DC converter.
Thanks
Ray
This is the dc to dc converter I have been using - there is a smaller model if you don't need that many amps output . I needed it for my ham radio .
https://www.amazon.com/Samlex-America-SDC-23-Amp-Converter/dp/B0002D6KO0/ref=sr_1_1?ie=UTF8&qid=1544588119&sr=8-1&keywords=samlex+sdc-23
Larry
Ray,
I am using a MagnaSine MS 4024 AE, an early model of the PAE 120/240 volt split phase units. It is tempeture corrected when used with the temperature sensor. You need to use the ARC-50 remote controller to set the correct temp compensation as default is 5 mv/degree .
I use a 24 volt main bank with a Samlex SDC-30 DC-DC converter to provide 12 volts for my travel trailer.
I have given up on forced air heaters as too inefficient and use Camco Wave Heaters which are catalytic and require no electricity and are silent. It doesn't snow here so I don't need much heat. I have two 2800 btu/h heaters in 34 foot fifth wheel travel trailer, one in main lounge and one in bedroom. Maybe 25% as much propane as combustion forced air heater that was standard. (Dometic)
My referigeration is direct DC 24 volt Grape Solar GS-5 referigerator. ( no longer in production )
The AC to DC converter in most modern motorhome are digital switching mode which are quite efficient but older Motorhomes use old school transformers which are very inefficient . If it is built into the bottom of the power control panel those are magnetic transformers. Motorhomes and trailers newer than 1988-1996 use the newer switching mode units. These units are separate from the power control panel. If you have the old school magnetic transformer type it is not too hard to wire in an Iota 40-50 amp charger/power supply to gain some efficiency there.
David
I have a ME ARC remote and the battery temperature sensor for the Magnum but can't seem to find any temperature compensation setting in it or the mention of it in the manual.
Lows are in the single digit to teens so I don't think the ceramic heaters are going to replace the 25k btu heater that I'm using now. I really should put a skirt on the trailer to help retain the heat but I'm having to move the trailer every couple weeks while the build goes on.
Wondering about the absorb end time/amp. I believe I understand this correctly that the end amp can be determined by noting every 10 minutes the WBjr amp reading and seeing when the amps stabilize. That would be the end amp. Deka has "<.1 amp/hr" as the end amp. I suppose it means when the amps change less then .1a in an hour that is the end amp. Now if I set the end amp, what do I do with the absorb time? Does the Classic go to float when it reaches either the time or the end amp?
Ray
Edit: Never mind found it in the manual. :-[