I don't have currently a battery temp compensator in my system. How would I do this on paper and how would I measure the temperature directly into the battery or from temp of air around my battery banks. My reading currently are about 1.28 to 1.30 and that is with air temp around batteries at 0 degree C or 32 degrees F .
Batteries are U.S batteries golf cart ones 232 amp hours in each 6 volt battery with total of 18 6 volt batteries made as 12 volt batteries. set up as 12 volt system
Quote from: fiddlerkelly on June 21, 2014, 09:13:10 AM
I don't have currently a battery temp compensator in my system. How would I do this on paper and how would I measure the temperature directly into the battery or from temp of air around my battery banks. My reading currently are about 1.28 to 1.30 and that is with air temp around batteries at 0 degree C or 32 degrees F .
Batteries are U.S batteries golf cart ones 232 amp hours in each 6 volt battery with total of 18 6 volt batteries made as 12 volt batteries. set up as 12 volt system
One way is to get a hydrometer with a built in thermometer. It will have a scale on it based on the temperature that you need to add or subtract from your readings.
Fiddlerkelly,
Correct temp comp for the batteries is -5mv /deg C / cell. (Temp above 25C)
+5mv / deg C / cell. (Temp below 25C)
So at 0C with nom at 25C and 6 cells Is +5 mv. X 25 (degree diff). X 6 cell = +.75
U.S. battery recommendation: Bulk = 14.4. Adsorb = 15.5. Float = 13.2. Equalize = 15.6
Charge rate = C/10 or 23.2 amps each set or 211.5 amps for 9 sets in parallel
Those are the published recommendations
Now my comments: 9 strings in parallel=====Asking for trouble!!!!
Why are you doing 12 volts========Asking for Trouble!!!!!!
You should be at a higher voltage for that kind of a.h. capability
What kind of charger are you using? Recommended charge rate this setup 211.5 amps hard to do an 12 volts!
Maximum number of strings in parallel recommended by pro's and installers = 2
Read a lot on this subject before going further down this alley!
Read the temp of the electrolyte solution, not the air around the batteries, charging warms them up and t comp will vary with temp.
Just my opinion.....been doin lectrix for 46 years!
td
Edited typo on total t comp number
For Rolls Batteries the S/G correction is
SG of acid is temperature dependent. If the temperature is very cold or very hot this can lead to incorrect readings. To correct for temperature use the following equations the equations or below 70ºF subtract points (0.03 per 10ºF) and above 70ºF add points.
•Correction factor = (0.331 x T/ºF - 23) / 100 or 0.03 pts per 10 ºF
•Correction factor = (0.595 x T/ºF - 12.5) / 100 or 0.03 pts per 5 ºC
IF i am reading your post right i am now concerned about my batteries. I have a 12 volt system as i cheaped out on a power invertor from canadian tire . 1000 watt pure sine wave which had only the option of 12 volt with 250 watts of solar panels. I am in the middle of upgrading to 1100 watts of panels and plan on running them at 48 volts and alos upgrading my invertor to a magnum 120/240 4000 watss pure sine wave . I correct me if I am wrong am going top take apart my battery bank and equalize the system two 6 volt batteries at a time hoping to reverse any possible sulfation that has occured in my system . I need to measure the S.G. when I go up this week to see where it is now that it has warmed up in my part of the country.
Fiddlerkelly,
That is exactly what I would do. 12 volts is a dead end. Separate all batteries. Charge as pairs until you get a specific gravity of 1.250-1.275 across all the cells. Pick your closest matched sets and use them.
Magnum at 48 volts is a real system, now what kind of charger are you proposing? Get one that is totally programmable at the least. Many lower cost units will not properly maintain battery sets. You have a few bucks in those batteries, now is the time to get a good charger for them.
Might I suggest a Classic 150 with the current measuring device "Whizbang jr." This charge controller will protect and maintain your investment better than the others.
The Classic comes with the Whizbang jr. and a battery temp. Sensor " MNBTS" but you will need a current shunt for the Whizbang jr. The correct one is a "Deltec 500 amp/50 mv."
Batteries in parallel is one of the major fail points in solar, the 48 volt route is the best path for a whole house system, at least 24 volt for a small house and system.
td
Actually I am planning for Midnight solar 200 as this was advised to me as to my VOC when all my panels are put to get her will be approximately 160 volts.
Quote from: fiddlerkelly on June 22, 2014, 06:05:36 PM
I am in the middle of upgrading to 1100 watts of panels and plan on running them at 48 volts and also upgrading my inverter to a magnum 120/240
Quote from: fiddlerkelly on June 23, 2014, 01:01:35 AM
Actually I am planning for Midnight solar 200 as this was advised to me as to my VOC when all my panels are put to get her will be approximately 160 volts.
Hold on, there might be a better solution... For the upgrade, how many panels, what are their Voc and Vmp, and how far between the combiner and the classic? Are you planning to keep your existing panels? How many of them and what's their specs?
I'd like to find out if you can configure the system to use a Classic 150, but as you realize, you cannot put all the panels in series on a Classic 150 when the Voc is 160.
I'm guessing that your 1100 watt upgrade is 4 panels, each with a Voc = 40. In which case all 4 in series is the only way to configure on a 48 volt system. But if your old panels can be used, there might be a way to make 2 strings at a lower Voc.
One more question: You mentioned a Magnum inverter, but you did not indicate (clearly) whether it would be 24 or 48 volts... which is it? Especially if it's 24 volts, you should really try to use the Classic 150. With an 1100 watt array, a 24 volt system voltage might be practical, although if your design goal is to use as many of your existing batteries as possible, 48 volts would mean fewer parallel batteries.
--vtMaps
Fiddlerkelly,
What vtmaps is saying is very valid, gather info on all panels and post the specs. There is an optimum voltage to run the panels and controllers. This will depend on distance from panels to charge controller. Generally speaking use p.v. Voltage 1.5 to 2.5 times battery voltage. The controller will work harder converting 160 volts down to 48 than if you use some lower voltage on your panel strings.
When the panels are more than 100-125 feet then the Classic 200 with 4 in series maybe more efficient but at shorter distances the Classic 150 with 2 panels in each string will probably more efficient.
The trade off is more power lost in wiring at the lower voltage vs. more power lost in the controller due to the lower effiency at the higher voltage.
If you have a very long run from solar array > 150 feet then higher voltage works out better.
Give us more info about placement , panel details etc. And the group of users will advise you as to the best configuration.
td
I will attempt to attach photos with info on them. I am going to be mounting my panels on the roof of my cottage so maximum distance from panels to charge controller is 40 feet. I have a #10 multistrand wire to wire panels to combiner box then to charge controller. I chose 48 volt as to keep wire size down.
Specs for 150 watt panels are to very right and the 50 watts towards the left. I already have 5 - 50 watts and would like to use them in my upgrade , 4 of them at least to make 2 -100 watt panels.
Thanks for all of the assistance.
Here is the magnum I was looking at. It is the 120/240 volt 48 volt. I initally chose that one as I planned on connecting my batteries into two lines each totaling 48 volts. To do this I would have to remove two batteries from the system but would I still be able to keep this 2 and have 3 lines of 36 volts. 6 6 volt batteries in series then 3 of those lines in parallel.
Make sense?
Quote from: fiddlerkelly on June 23, 2014, 02:36:57 PM
6 6 volt batteries in series then 3 of those lines in parallel.
Make sense?
No, it does not make sense. You would need 8 in series to make 48 volts. Two strings of those would use 16 batteries.
What I think you should do is calculate your loads and then design the ideal system on paper. Then you can try to figure out what to do, what compromises to make, to utilize as much of your current system as makes sense.
Your batteries are ephemeral... your panels and inverter will long outlast your batteries. I wouldn't necessarily base a lot of decisions on trying to use those batteries. If, for example, you would be better off with a 24 volt system, then do it that way. You would have four strings of batteries (not ideal) but only for a few years.
--vtMaps
Fiddlerkelly,
All of the panels that you have are 36 cell panels with a v@pmax (volts at max power) is 17.2
Most of the 250-300 watt panels are 60 cell about 30 volts......not a good match.....keep looking for your upgrade panels......some builders are making 72 cell panels........now then if you use two 72 cell panels in one string and 4 36 cell panels in another string everything will balance as the 72 cell panels are about 34 volts. This is what I am doing as I have many legacy Siemens 36 cell panels working well with SunTech and EPolly panels.
I use 2 72 cell panels or 4 36 cell panels in each string for a total cell count of 144 and volts about 68.8
Rule of thumb when mixing panel types:
Panels in a series string must have the same current at max power within a few percent
Strings or panels in parallel must have a total string voltage within a few percent.
Manufacturers that do have 72 cell panels include : SunTech , poly cell only, Canaidan Sun , ePolly
The largest bulk of panels are 60 cell but 72 cell can still be found, it is probably a easier way to go.
You really have several options here, use a mix of panels having same voltages
Or use separate charge controllers for 36 cell banks and 60 cell banks.
Best deal I found for non standard grid tie panels are the 72 cell EPolly panels at northern Arizona wind sun.
I have been eyeballing those Magnum units for a while, they just brought out a new model, though not 120/240 it has some compelling features for me.....load sharing with a generator or utility
The MSH 4024 RE for 24 volts, they have not released this one in 48 volts yet...stay tuned
td
Fiddlerkelly,
Vt posted while I was writing but he did catch the 36 volt bit. 36 volt is used but is very rare, 24 volt and 48 volt are the common off grid voltages used. If your needs are small a 24 volt system will have advantages but if you plan a 4 bedroom house with all that you are used to when living on grid then a 48 volt system is called for.
Personally I am using 24 volt as I live in a small space and have a small workshop, it's a good trade off for me. I could have done a 12 volt system but the losses in the lower voltage inverters and wiring made that not feasible and I converted my motorhome to 24 volt right from the start, I separated the original 12 vehicle system and left it as is and added 24 volt system for all the house systems , inverters etc.
It helps that you post all info about what your needs are so everyone does not second guess as to what your desired system is to do.
td
Yes where I currently have 18 6 volt batteries to wire for 48 volts I would have to drop two to 16 with 2 lines of 8 6 volt batteries but if I wanted to utilize all then I was thinking 3 lines of 6 batteries.
Panels are already bought and en route. The guy I am buying off suggested putting two groups on roof comprised of 3 150 watt panels and a 100 watt panel made of two of the 50 watts that I already have. Then running the two groups down to a combiner box and then to controller.
Hi fiddler ..,
36 Volt systems are not common for off-grid power. It will be difficult to find a quality Inverter for a battery bank of that voltage.
As td mentioned, generally, when adding PVs in series, the maximum difference in Imp of two different PVs should be 10%. A 5% or lower variation in Imp would be better.
And when adding different PVs in parallel, the Vmp should be within 10% maximum, with a 5% variation or less being better.
The above are basic rules, but it you try to be at 5% or less variation in either case, you should, generally, be fine.
FWIW, Have Fun, Vic
I have mostly just lights at the cottage 2 12 volt water pumps a 42 inch flat screen with basic receiver but plan on adding a 7 cut fridge with draws 1.5 amps and at times a laptop .Average draw on system will be approximately 4 amps /hour at most 8 hours a days little less in summer . Water pumps only run when needing water.
I heard so much about wiring batteries and got from it the less parallel is better.
Fiddlerkelly,
Please clarify one thing for me. Are all the panels that you plan to use from the same manufacturer?
The ones shown in the chart you uploaded?
If this is true then you have 144 cells in each string? String voltage will be about 68.8 not the 160 volts that you would see with higher cell count panels.
If you do what you suggest, making a series string of different current panels of three 150 watt panels in series with a set of two paralled 50 watt panels , the two 50's will add to only 100 and will throttle down the 150 watt panels to 100 watts so total string watts would be 400 watts , not 550 watts as you might calculate.
Now then if you were to try 3 of the 50 watt panels in parallel in a string of 150 watt panels it would balance.
The more info that you post the better that others will understand what you are trying to accomplish.
td
Here is a formula I found for adjusting ST according to temp. Look right?
Yes from same company and guy told be they can be combined. The difference in VOC is minimal.
Fiddlerkelly,
These panels are all "12" volt 36 cell panels but the current is what matters in a series string. The 50 watt panels are 2.91 amps and the 150 watt panels are 8.72 amps so if you were to put two 50 watt panels in parallel in a string of 150 watt panels you will throttle down the 150 watt panels to 2.91 times two or 5.82 but if you were to use 3 of those 50 watt panels the current would be 8.73 amps and would not limit the 150 watt panels.
Three 150's in series with 2 paralled 50's will produce 400 watts........they all act like 100's
Three 150's in series with 3 paralled 50's will produce 600 watts........they all act like 150's
This is not the way to design a new system but as all the panels are same make, all will be using same cells so this will work......add 1 or 2 more 50 watt panels and balance the strings.
Now that you have described your use a bit more I think definitely I would recommend 24 volt battery set, a Classic 150 with MNBTS and Whizbang jr. and shunt. And use 68.8 volt strings.....144 cell...
The 48 volt comes into play when you have a washer and dryer and a bunch of kids to keep it full,
Small house, getaway cabin, etc. 24 volt will do all you need. 4 strings of batteries is not the ideal but your big ticket items , charge controller , inverter/charger , and your use of system should dictate battery size and voltage.
td
Quote from: fiddlerkelly on June 23, 2014, 03:33:27 PM
The guy I am buying off suggested putting two groups on roof comprised of 3 150 watt panels and a 100 watt panel made of two of the 50 watts that I already have.
Technodave explained why that is a poor idea... the 50's will limit the 150's.
He also explained that you could put 3 of the 50's in parallel, and then put those in series with the 150's.
The problem with both of those schemes is fusing.... I really don't think it will be cost effective to do either of those schemes.
I agree with Technodave that you should be at a system voltage of 24.
Probably the best approach is to buy another controller for the new panels and use your present controller with the old panels. There will be no problem having two arrays, each with its own controller, connected to one battery bank.
--vtMaps
Fiddlerkelly,
Vtmaps said it best! For simplicity, keep it simple, all panels in string should be same for best results.
I am only using legacy 36 cell panels because I get them surplus for .10-.15/watt. If I had it to do over I would use the big standard, the 60 cell type commonly available, but I have 2 kW of "12 volt" panels and I have been doing Lektrix way tooo looong.
To make best use of what you have already ordered use strings of three panels. If you do a 24 volt battery bank this will be enough voltage at 52.2 volts, then if you want to use your 5 50 watt panels add one and make two strings of 3 each. This will work much better. Circuit breakers on each string, 1.25 times the max amps for that string.
td
Yeah I am considering selling the 5-50 watt panels and getting another 2 -150 same type as rest that way everything is identical and I gain an extra 50 watts .
resthome
•Correction factor = (0.595 x T/ºF - 12.5) / 100 or 0.03 pts per 5 ºC
Jut done a quick calculation as spot check on one battery and was getting 1.3 on all 3 cells of 6 volts and ended up with result of 1.264 in each cell. open circuit voltage was 6.3 volts on one battery.
Sound like in good condition ? temp of cell was 65.2 F.
Fiddler,
That is a pretty good idea, have all strings identical, way easier to diagnosis a fail mode and repair.
My system is way too complicated, charge controllers from 3 different companies, panels from 5 manufacturers, 3 panel types.......that said......been an electrician for 46 years, would never do anything like this for a customer! Way too difficult to diagnosis a failure!
td
Fiddler,
I was writing while you posted so I didn't see your post. If that is your specific gravity then you are ok on that battery. Full charge when new should be 1.265-1.275 , but it's important that cells do not vary more than .020 from each other. Check and record readings for all batteries , then pick and choose those that are real close in readings for each string. How are you charging now? Having a charger with a battery temp sensor makes job much easier.
td
These were 4 batteries that I had taken out of the system with plans on charging them with two 6 volts done in series each. When I had got home from cabin with them I just done a spot check on their voltage prior to charging and they were reading 13.3 volts. I suppose it was the shaking up they got on the way out the woods road. So I decided to let them sit for a couple of days to level of their voltages. So when I went out today to get their SP the batteries had leveled off to about 12.65 volts. I bought a digital temp probe used for cooking to measure temp of battery acid.
Hopefully I will be able to get 2 more panels from same company for the price I got on the others. This will give me a few more watts for my system also which is a plus.
So if I go with all same panels is there any reason why I just can't connect these in series for a total of 136 VOC approximately as this would help reduce amps on wires going to charge controller.
Hi fiddler ..,
Am not sure where what you are using for a CC. Know that you were considering a Classic 200, previously.
Normally, if one wanted to use an MPPT CC, that person would use one with a 150 V input capability. And only use a Cl 200 or 250 when the cable run from the PVs to the CC is long, dictating a higher string Vmp to reduce the loss and or copper cost.
Running high string Vmps reduces the efficiency of the CC, causing it to run hotter than it would with lover Vin.
We do not know where you are located, but running a string Voc of 130 V or more usually means that the Voc in Winter can easily exceed 150 V, and will also reduce the efficiency of the CC. Most MPPT CCs will be damaged and/or have any warranty voided when 150 V input is exceeded. Classic and KID CCs have Hyper VOC, which extends this problem point by at least 12 V input.
AND, if you are still considering/using a 12 V battery with this proposed system with 135-ish Voc, then it is even less good than stated above.
Here is the Classic String Sizer - it is very easy to use and look at various scenarios:
http://www.midnitesolar.com/sizingTool/displaySizing.php
Should you need it, here is the String Sizer for the KID:
http://www.midnitesolar.com/sizingTool_kid/index.php
If you are able to come up with two identical or balanced strings, this is often a good way to go, and you will still not need a Combiner with Fuses or Breakers in it. When setting up strings, String Sizing Tools will help avoid strings with too low a voltage for the CC, or ones with excessive string voltages.
Opinions, YMMV, Have fun, Vic
What do you mean by CC. Not familiar with that term.
Hi fiddler, sorry, I should have typed out Charge Controller (CC). Vic
Quote from: fiddlerkelly on June 29, 2014, 04:23:33 PM
What do you mean by CC. Not familiar with that term.
CC= Charge Controller ie Midnite Classic 150
Quote from: fiddlerkelly on June 29, 2014, 04:23:33 PM
What do you mean by CC. Not familiar with that term.
Charge
Controller
And in case you missed it, CC is Charge Controller...... :P
I am located in eastern canada in newfoundland. Where the volts are not far of 150 only approximately 14 away from max the winter with colder temp and reflection from snow may put it over the top of 150. The company selling me the the panels said I may be better off getting a 200 midnite solar. The maximum length of wire from panels to to CC would be 45 feet. I am using #10 multi strand wire approximately 7 strands. So if I end up with all 150 watt panels 8 of them what would be the best configuration for connecting them to the midnite solar and which would I be better off to use.
Quote from: fiddlerkelly on June 29, 2014, 11:45:51 PM
The company selling me the the panels said I may be better off getting a 200 midnite solar. The maximum length of wire from panels to to CC would be 45 feet.
<snip>
So if I end up with all 150 watt panels 8 of them what would be the best configuration for connecting them to the midnite solar and which would I be better off to use.
A classic 200 on a 12 volt system? That's terrible advice. You should not down convert such high voltages to 12 volts. Especially since your array will be pushing the limits of a classic 150, and would exceed the limits of a classic 200.
You have not mentioned the Vmp or Imp of your panels, so I can't give you any meaningful advice on an array configuration. You will certainly need a combiner and circuit breakers.
btw, In my opinion, your system is a disaster and you are about to compound it. You have 9 battery strings in parallel, totaling over 2000 ah. That is wrong for two reasons... 9 parallel strings is unworkable and a system that size should not be a 12 volt system.
Your proposed array (1200 watts) will be inadequate to properly charge a battery bank that size, although in reality there is no way, with any amount of power, to properly charge 9 parallel battery strings. All you need is one shorted cell in one battery and you will have a fire or explosion.
My advice is to determine your loads and design an optimal system on paper. Then, figure out how much of your existing system can be used to build a properly designed system.
--vtMaps
Vt is right, your are playing with fire without your firerproof gloves on.
If you want to install a system of the size you are comtemplating, you either need a professional, or you need to invest some time in learning electrical engineering. One of the two. Theres a reason people use sparkys to wire their houses, and solar is no different. In fact with batterys, as vt said, off grid is actually more dangerous again.
As others have said it comes down to loads. You need a load budget. Take the below, and flesh it out so that each item has a number of Wh/day. Make sure everything is included, everything that you will need in your use case, for say the next 5-10 ten years. Thats about the life of the hardware. See the links in the link in my sig for an example load budget.
Once you have then you can decide what is the best system voltage, and exactly how much battery, controller, and inverter you need. Do anything else and you just guessing, and burning money away.
Quote from: fiddlerkelly on June 23, 2014, 03:43:24 PM
I have mostly just lights at the cottage 2 12 volt water pumps a 42 inch flat screen with basic receiver but plan on adding a 7 cut fridge with draws 1.5 amps and at times a laptop .Average draw on system will be approximately 4 amps /hour at most 8 hours a days little less in summer . Water pumps only run when needing water.
I heard so much about wiring batteries and got from it the less parallel is better.
One other thing, if you want to use dc pumps, then thats one reason to opt for 24V as opposed to 48V. But if your system is or will grow to 3kWp or greater then 48V is a must. For the PV, 45ft is nothing, and the Cl150 is your friend there.
Just ordered another 2 panels with exact same spec as other 6 -150 watt panels that are coming. So I will now have 8 -150 watt panels total and from what I have been reading here should wire them up as 24 volt and that the midnite solar should do fine.
Regarding the DC pumps how will 12 volt pumps work in a 24 volt system.
Re the pumps, 24v pumps are the same price as 12v pumps. 48v pumps dont exisit.
12v is a dead end for a growing system. You could theoretically run your exisiting 12v pumps off a dc converter, but i would not do it. Pumps need surge capability.
Like we were trying to convey, maybe try not to order anything else until youve got a plan :)
I suggest you head on over to the NAWs forum and get Bill and Coot to run over your design with you.
Where do I find the NAWS forum. Thanks also for all advice , greatly appreciated.
Fiddler,
NAWS is Northern Arizona Wind and Sun. On line store and great forum
Forum: forum.solar-electric.com/forum.php
td
Oh yeah I am member of the site just never use the abbreviation. Thanks.
Resthome
Just to get back to temp compensation. I checked all the cells in the batteries I took home, temps were between 79.5 -80.0 F. the SP of all cells in the four 6 volt batteries were between 1.295 -1.30 before calculation. they all look good to me . what do you think. So with these readings does that mean there should be no sulfation in those batteries at present.
fiddlerkelly
fiddler..,
The Specific Gravity (SG) readings on your batteries seem a bit high. I have not run the same brand GC2 as you have, but, would expect that the highest SG that would have been shipped with would be 1.277 - 1.280 (at 25 degrees C). Perhaps, even 1.265.
SO, your batteries may well need some Distilled Water added, given the high SGs, IMHO, given that the temps that your report are very, very close to standard rating temperatures.
FWIW YMMV, Vic
Vic all of the batteries have at least 1/2 inch of battery acid over the tops of lead plates. I had brought the batteries back upto cabin inn truck and roa going in is rough in spots so for sure acid was shaken up but I never checked the batteries till next day , if that makes any difference in SG.
fiddler ..,
OK, then, perhaps your Hydrometer just reads a bit high.
Forget if this has been mentioned, but Hydrometers need to be rinsed, several times with Distilled Water after each measuring session. If not rinsed, the Hydro gets a sticky residue built up inside. This residue can allow air bubbles to stick to the float and inside the tube. These bubbles cause false readings, often high readings.
The plastic Hydros seem to have floats that can be eaten by the electrolyte. This seems to cause ever-increasing readings despite the actual SG of the electrolyte.
All FWIW. Vic
Quote from: Vic on July 08, 2014, 10:37:46 AM
The plastic Hydros seem to have floats that can be eaten by the electrolyte. This seems to cause ever-increasing readings despite the actual SG of the electrolyte.
Does that statement apply to the Hydrovolt that Midnite sells? --vtMaps
vtMaps,
I should have done a better job describing just which "plastic" Hydrometers that seem to have that malady.
Some of the Hydrometers that appear to have this issue are those that have a plastic body, and a plastic float that is also the pointer to the SG scale. Often the SG scale is colored and may not even have any SG numbers on it, just something like "Charged" .. "Discharged", "Good" ... "Low" or similar subjective terms.
On the above type Hydrometers, it appears that the electrolyte can attack the plastic of the pointer, and erode it, causing a permanent change in buoyancy, and therefore a permanent change in accuracy. This problem would probably not exist IF THE HYDROMETER WAS RINSED SEVERAL TIMES AFTER EACH MEASURING SESSION -- This rinsing is very important for any Hydrometer!
These are often $7.00 Auto Store type Hydrometers.
Have NO reason to believe that the HydroVolt Hydrometer has any of these issues. It appears to be very well constructed, easy to read, accurate and generally, repeatable, if the reservoir is fully filled when the reading is taken. The HydroVolt is a very good Hydrometer.
Sorry for the lack of precision in the description of the problematic class of Hydros. Thanks, Vic
Yeah Vic my hydrometer is all glass along with the actual float and shows both the colors from weak to strong and a numerical scale. Bought mine at canadian tire. Just need to do temp com each time as the hydrometer does not have built in temp comp and yeah I do clean mine with distilled water after as just recently I broke the float in one and when I got a new one I notice and dark spot on inside of glass tube at about where the battery acid level would be when measuring SG. Will have to pay more attention to the cleaning.
I finally got tired of all the fooling about with float style hydrometers and got a Robinaire refractory type:
http://www.amazon.com/Robinair-75240-Coolant-Battery-Refractometer/dp/B000HTNODE/ref=sr_1_1?ie=UTF8&qid=1387201098&sr=8-1&keywords=robinair+refractometer (http://www.amazon.com/Robinair-75240-Coolant-Battery-Refractometer/dp/B000HTNODE/ref=sr_1_1?ie=UTF8&qid=1387201098&sr=8-1&keywords=robinair+refractometer)
Looks like this:
(http://ecx.images-amazon.com/images/I/71zNomrtdaL._SX522_.jpg)
It has gone up in price since I got mine but it is great.
No temperature compensation, no sticking floats and only uses a drop of fluid. Easy to calibrate against distilled water. Works for battery fluid or coolant.
Tom
Quote from: TomW on July 09, 2014, 10:32:46 AM
No temperature compensation, no sticking floats and only uses a drop of fluid. Easy to calibrate against distilled water. Works for battery fluid or coolant.
Most installers around here do prefer refractometers to hydrometers.
Most of the ones I've seen have built-in automatic temp compensation... are you sure yours has no temp compensation?
Also, you should calibrate it against battery acid of known concentration... distilled water is too far out of its range to trust for calibration.
--vtMaps
Quote from: vtmaps on July 09, 2014, 12:33:06 PM
Quote from: TomW on July 09, 2014, 10:32:46 AM
No temperature compensation, no sticking floats and only uses a drop of fluid. Easy to calibrate against distilled water. Works for battery fluid or coolant.
Most installers around here do prefer refractometers to hydrometers.
Most of the ones I've seen have built-in automatic temp compensation... are you sure yours has no temp compensation?
Also, you should calibrate it against battery acid of known concentration... distilled water is too far out of its range to trust for calibration.
--vtMaps
I should have said "
no temperature compensation needed". The tiny bit of fluid takes on the temp of the tester so I guess it is "automatic". Or that is my understanding.
You are probably right about the calibration. I just used the method in the instruction manual it came with. Seems OK if you lack a fluid with a known S.G. in the proper range?
I only speak 2 languages. English and Bad English so any confusion is my doing!
Tom
Well actually on the packaging of the hydrometer it doesn't say it does temp comp and at 8 dollars Canadian I assumed it doesn't.
Rather than start another subject I thought I ask this here as already under battery.
Lets say you have a system. 12 volt as example with 12 - 6 volt batteries , 2 a piece in series and then all parallel from there and you have 300 amps of panels on roof. Lets say you use it for 8 hours one evening drawing 2 amps an hour for total of 16 amps that evening. So that night you burned 960 watts of energy. Okay next day it is charging it is sunny but takes two days of sun to fully recharge, would a system with 6 -6volt batteries recharge faster or slower all other things being the same considering that that 960 watts is being consumed from a smaller bank in one case and a bigger in another case.
Feedback appreciated and why or if one is faster than the other.
I can't even read this without fixing it...
Quote from: fiddlerkelly on July 13, 2014, 10:14:16 AM
Lets say you have a system. 12 volt as example with 12 - 6 volt batteries , 2 a piece in series and then all parallel from there and you have 300 amps of panels what does this mean? on roof. Lets say you use it for 8 hours one evening drawing 2 amps an hour I think you mean 2 amps for total of 16 amps I think you mean 16 amphours that evening. So that night you burned 960 watts I think you mean 960 watthours of energy. Okay next day it is charging it is sunny but takes two days of sun to fully recharge, would a system with 6 -6volt batteries recharge faster or slower all other things being the same considering that that 960 watts I think you mean 960 watthours is being consumed from a smaller bank in one case and a bigger in another case.
Feedback appreciated and why or if one is faster than the other.
The answer to your question depends on whether there are limiting factors on the charger or the wiring or the battery.
In either case you are removing 960 watthours of energy from a battery. With the smaller battery bank, the discharge takes you to a lower SOC just because the 960 watthours is a greater percentage of total capacity of the smaller bank. However, the higher currents involved in drawing current from the smaller bank means there will be greater Peukert losses of the battery, and I
2R losses in the wiring. Thus the SOC will be disproportionately lower in the smaller battery bank
Therefore you need to replace more watthours in the smaller bank.
Another factor that is very important is where your SOC is on the charge efficiency curve... charging from 50% to 60% SOC is more efficient and takes less time than charging from 85% to 95%. With a larger bank you may need to spend more time in the slower, less efficient range.
Another issue in the timing of the charge cycle is charger limitations... how many amps of bulk charging current can your panels and controller produce as a function of the battery capacity? It is likely a different number for each different battery bank.
--mapmaker
Thanks vtmaps for picking me up on my errors. 300 amps panels was suppose of course to say 300 watts . Regarding what you are saying about charging from 50-60 SOC is more efficient than from 85-90 % SOC. So are you saying that if your battery bank is discharged to 50-60% that this is better for a battery bank than just to discharge to 85-90% SOC. The reason I ask that question is when first reading about solar power and battery banks that you should only use approximately 20 % of the battery bank capacity as this will maximize the life of the batteries /battery bank. Am I misunderstanding what I had read or am misinformed.
Thanks again for your assistance.
Quote from: fiddlerkelly on July 13, 2014, 05:28:55 PM
The reason I ask that question is when first reading about solar power and battery banks that you should only use approximately 20 % of the battery bank capacity as this will maximize the life of the batteries /battery bank. Am I misunderstanding what I had read or am misinformed.
The shallower the cycle, the more cycles you get. You batteries will last more days with 20% cycles than with 40% cycles... but that is assuming daily cycles. You want to avoid very shallow cycles (less than 10%) because you may get lead dioxide clumping on the positive plate.
Suppose you have 40% daily discharges with a particular battery bank. If you double the bank you would have daily 20% discharges. So with a double sized battery bank you spend twice as much money and it lasts almost twice as long as the single sized bank.
If you have a big battery you can skip charging until you get down to 40% DOD (= 60% SOC). Then you have deeper cycles, but each cycle last two days, so your battery may last twice as long because it has half as many cycles per week or month or year.
There is one other consideration... if you create the big bank by paralleling smaller batteries (rather than using big batteries) you are shortening the life of the bank and reducing its safety (fire, thermal runaway) because of all the issues with parallel banks.
--vtMaps
Vtmaps, right now have my system parralled as is, 2 - in series 6 volt batteries, but am just waiting for new panels to arrive and will be connecting my panels as 24 volts . Plan is to get the midnite as I said before . Even though I connect my new panels in sets for total of 24 volts and join all in a combiner box can I still have the battery bank set up as 48 volt. Is there a feature in the midnite that gives me this option or do I have to stick with arranging my batteries as 24 volt system.
If you have a big battery you can skip charging until you get down to 40% DOD (= 60% SOC). Then you have deeper cycles, but each cycle last two days, so your battery may last twice as long because it has half as many cycles per week or month or year.
so the big battery you refer to can either be as you said one big battery or several connected in series as one, right.?
Thanks
Quote from: fiddlerkelly on July 14, 2014, 09:30:58 AM
Even though I connect my new panels in sets for total of 24 volts and join all in a combiner box can I still have the battery bank set up as 48 volt. Is there a feature in the midnite that gives me this option or do I have to stick with arranging my batteries as 24 volt system.
You must always configure your panels so that the string voltage is higher than the battery voltage. Remember, a 24 volt battery may need to be up at 31 volts at times, and a 48 volt battery may need to be at 62 volts on occasion. This thread is long and I don't remember the specs on whichever panels you are referring to, so I don't recall whether two of your 24 volt panels can charge a 48 volt bank... if it can, you're cutting it pretty close.
If you reconfigure your panels and combiner box so that you have three panels in series, (and the Voc is not too high), you can charge a 48 volt battery.
Quote from: fiddlerkelly on July 14, 2014, 09:30:58 AM
so the big battery you refer to can either be as you said one big battery or several connected in series as one, right.?
Yes, "Big" refers to battery capacity... doesn't matter how many batteries or whether they are series or parallel. Of course there is only one battery configuration that is most optimal, that being a single string of battery cells that are large enough to give you the capacity you need.
--vtMaps