Battery Monitor and/or Multiple temperature sensors

DickyDck · June 2019

Hiyas everyone! As I am adding more batteries to my existing setup (thanks Dave and Dave

) I noticed there is only one battery temp sensor on my existing string of 8 x 6v 220ah batteries on battery #2. All my gear is Schneider, and I'm planning to keep everything uniform for the inter-operability benefits that Schneider/Conext has built into their software. I have a XW6848+ hybrid converter, and 2 MPPT 60-150s. Would it make any sense to get additional battery temp sensors to hook up to the Charge Controllers, or is the one going to the Inverter good enough? Some guys on the other group I post to mentioned I should consider the Schneider Batter Monitor, which looking it over it does offer a lot of neat things like SOC, true charge readings, how many times full Charge has been done thought I'm not sure how it would know that if added to an old existing battery bank. A couple of battery temp sensors is relatively cheap, 25 each, and can plug right into the charge controllers, but I'm not sure if telling the charge controller the temps would benefit the system in any meaningful fashion. I assume it is just getting the reading from the inverters temp sensor. Just wondering your thoughts since next week 8 more heavy ass batteries are getting dropped off. Thanks in advance!

mcgivor · June 2019

When multiple battery banks are used, each controller must have its own RTS, if a single bank is charged by multiple controllers only one is required as information is shared via Xanbus, if multiple RTS's are used the one with the highest reading will be used to control the voltage.

DickyDck · June 2019

So RTS=Temp sensor correct? I don't know all the acronyms yet used in solar so please forgive me. And I am keeping it as one battery bank, just adding 8 more batteries to increase the AH from 220 to 440. So in this scenario, I'm still going to only have one batter bank, and the single temp sensor which is going to the Inverter and being used by the Xanbus should suffice, if I understand what you told me correctly, if not please correct me! thanks!

BB. · June 2019

RTS= Remote Temperature Sensor (aka, the sensor that goes from the solar charge controller to somewhere on the battery bank--lug, side, etc.).

Having good air circulation helps keep all batteries the same temperature. Use an IR Thermometer to do a quick check--You are looking for "differences"--If you find differences, then you need to investigate.

A few folks here are experimenting with water baths, and even active cooling via refrigeration pump to keep the batteries at ~75F/25C or less... 10C or 18F higher temperature, causes batteries to age ~2x faster (20C higher than 25C, even 2x2=4x faster aging).

-Bill

DickyDck · June 2019

so <= 25c is good/better, got it! I'm rigging up a new enclosure for my batteries so this is good info!

mcgivor · June 2019

DickyDck said:

So RTS=Temp sensor correct? I don't know all the acronyms yet used in solar so please forgive me. And I am keeping it as one battery bank, just adding 8 more batteries to increase the AH from 220 to 440. So in this scenario, I'm still going to only have one batter bank, and the single temp sensor which is going to the Inverter and being used by the Xanbus should suffice, if I understand what you told me correctly, if not please correct me! thanks!

According to the manual one should be all that's required, the only advantage I can think of having more than one RTS would be greater coverage of the bank, though it's not significant enough to warrant the expense. Didn't each device come with a sensor? Usually they are included.

DickyDck · June 2019

mcgivor said:

DickyDck said:

So RTS=Temp sensor correct? I don't know all the acronyms yet used in solar so please forgive me. And I am keeping it as one battery bank, just adding 8 more batteries to increase the AH from 220 to 440. So in this scenario, I'm still going to only have one batter bank, and the single temp sensor which is going to the Inverter and being used by the Xanbus should suffice, if I understand what you told me correctly, if not please correct me! thanks!

According to the manual one should be all that's required, the only advantage I can think of having more than one RTS would be greater coverage of the bank, though it's not significant enough to warrant the expense. Didn't each device come with a sensor? Usually they are included.

So "IF" each device came with a temp sensor, the company that installed it kept the other 2 for the Charge Controllers. As I don't see anything anywhere in any of the boxes that were left. 1 RTS seems to be sufficient for my setup so I'll leave well enough as is!

Dave Angelini · June 2019

"when in doubt read the manual" It is in there to use only one sensor for a reason. If you think you are more in the know than the people who designed the system do it.
There has to be some sanity here, right?
You are doing the right thing Dicky!

mcgivor · June 2019

Dave Angelini said:

"when in doubt read the manual" It is in there to use only one sensor for a reason. If you think you are more in the know than the people who designed the system do it.
There has to be some sanity here, right?
You are doing the right thing Dicky!

Dave strikes again with yet another vieled condescending comment, a common trait it seems

The purpose of a discussion is to discuss, the manual was consulted, if it had said use one and only one remote temperature sensor, then that would be blatantly clear, perhaps my manual is different from others, this is what my manual states.

Image: https://us.v-cdn.net/6024911/uploads/editor/zj/6bgyw4z4m4nm.jpg

DickyDck · June 2019

There seems to be a few online versions of the manual, I have like 3 or 4 and there are subtle variations in each section. In all honesty, I’m that guy that just likes seeing all the readings lol, since I only saw the temp in the inverter readings, and in each charge controller battery temperature reads “unavailable” I thought to come here and ask if there was any real good reason to spend 50 bucks just to satisfy my desire to see “all the things”

but logic eventually, sometimes, takes over and since you guys who are obviously (not being sarcastic) much more knowledged than I am, I listen to my betters advice. I truly don’t mind if someone is subtly talking down to me, as long as I get the point and come out more knowledged I am perfectly happy! I really appreciate everyone’s input here! You guys don’t have to help anyone like me out but you take time out of your day to do so, and that is great in a world where the majority of people just look the other direction.

WaterWheel · June 2019

As others have said there is no advantage to using more than one tempature sensor per battery bank when using Schneider equipment. Correct placement of that sensor is more important and there are several good locations such as a battery lug.

All battery meters tend to drift out of calibration as far as State Of Charge (SOC) is concerned but I'm glad I added a Conext Battery Meter when I set up my system. It's the 1st thing I look at most mornings when monitoring the system. But if you have Lead Acid (LA) batteries it's smart to verify any battery meter using a hydrometer. Using a hydrometer occasionally also helps you adjust the charging parameters as the seasons change.

Image: https://us.v-cdn.net/6024911/uploads/editor/zx/gtuqbxu15a40.jpg

You can see where I mounted my battery meter but it puts the plastic monitor case back almost touching the POS battery terminal connection under the inverter. If I were ever to do it again I'd mount the battery meter 3/4" lower.

BB. · June 2019

The problem is that batteries consist of a bunch of 2 volt cells... In series and, many times, parallel. If the batteries are all over the place temperature wise, there is no way that a single charge controller can "adjust" its output based on individual temperatures. (hot batteries have higher self discharge, lower charging voltage, greater usable capacity).

You get the "bulk" temperature of the bank, and watch for outliers (those cells/batteries that are "too hot") and figure out why that is.

In general, with "relatively matched" cells, they should all be at the same temperature. If you have (say 1/2 in a closet, and the other 1/2 in an open/well ventilated area)--The better fix is to get all cells in the same room with good airflow so that they are all close to the same temperature.

-Bill

Dave Angelini · June 2019

mcgivor said:

Dave Angelini said:

"when in doubt read the manual" It is in there to use only one sensor for a reason. If you think you are more in the know than the people who designed the system do it.
There has to be some sanity here, right?
You are doing the right thing Dicky!

Dave strikes again with yet another vieled condescending comment, a common trait it seems

The purpose of a discussion is to discuss, the manual was consulted, if it had said use one and only one remote temperature sensor, then that would be blatantly clear, perhaps my manual is different from others, this is what my manual states.

Get over it, just because I say something in my way, I have just as much right to that as you have to be sensitive. Report me to Bill

There are also problems over the 15 years of XW and hundreds of installations I have seen that are caused by multiple sensors.

DickyDck · June 2019

BB. said:

The problem is that batteries consist of a bunch of 2 volt cells... In series and, many times, parallel. If the batteries are all over the place temperature wise, there is no way that a single charge controller can "adjust" its output based on individual temperatures. (hot batteries have higher self discharge, lower charging voltage, greater usable capacity).

You get the "bulk" temperature of the bank, and watch for outliers (those cells/batteries that are "too hot") and figure out why that is.

In general, with "relatively matched" cells, they should all be at the same temperature. If you have (say 1/2 in a closet, and the other 1/2 in an open/well ventilated area)--The better fix is to get all cells in the same room with good airflow so that they are all close to the same temperature.

-Bill

When building an enclosure, since I’m getting another 8 batts making a total of 16, should I plan to have space between each battery? When the guys initially set it up they did 2 things that really pissed me off. First they put all the batteries strain on the concrete floor of my garage, second the put them all in a row touching. I used to work in automotive and one of the things I was taught very early in that career was never put batteries on the cold concrete for prolonged periods of time. So I am making a new setup, getting the batteries off the concrete, and thinking about adding a gap between the first row of 8 and that same with the second row of eight. To allow for more airflow and keep the batteries from sharing heat. Thoughts?

BB. · June 2019

It is pretty much accepted (from what I have read) that putting modern batteries on a concrete floor does not hurt the batteries.

From what I remember in years pasts, there was a belief that FLA batteries on a concrete floor would self discharge much faster than on wood/other materials. While it is possible that old battery cases (asphalt and rubber/etc.) may have had some issues on concrete (I guess a bit of leaking electrolyte through the rubber case can dissolve the concrete and get on the battery/terminals and cause problems)--That is long ago.

Not to say that placing FLA batteries on concrete is the best material... Batteries do leak and overflow (filled to near top of cell with distilled water, heat and gassing from charging/equalization), and sometimes battery cases do get cracked/damaged/freeze damage (AGM and GEL batteries are not supposed to lose electrolyte when their cases crack). Placing batteries in a tub, box with membrane lining, sacrificial materials such as wood (easy/cheap to replace if damaged) can reduce the chances of more expensive repairs down the road and having to clean up sulfuric acid electrolyte/and other damage...

https://www.snopes.com/fact-check/battery-park/

As the above article states, in theory, if the concrete floor is cooler than other storage locations (warm shelf in a garage), the cooler floor will help the battery last longer (ever 10C reduction in battery temperature is a 2x longer expected life--from aging)

-Bill

BB. · June 2019

I have never gotten into the details of large industrial battery bank design... But in general, the batteries in the center of a tightly packed bank are going to be warmer than those towards the edges... (assuming the batteries are warm and the air is cool).

If you are going to space batteries to allow convection for airflow--Convection does not occur (circulating air currents) when the gaps are 1-3 cm or less... And really starts when gaps are 5-7 cm or more (based on double pane window spacing):

https://physics.stackexchange.com/questions/368346/how-large-does-an-air-gap-have-to-be-to-allow-for-heat-transfer-by-convection#368395

Or in Imperial units, less than ~1", poor air circulation... >2", improved air circulation/convection currents.

-Bill

Estragon · June 2019

In terms of load on the floor, 16 x L16s would be something like 2000lbs., or about the same as a compact car. I suspect the small car load rolling in and out would be harder on the slab than the dead load of the bank.

WaterWheel · June 2019

Yes, You want at least a 1" air gap between batteries.    This helps the batteries to cool.    Sitting directly on concrete won't hurt the batteries and the concrete may act as a bit of a heat sink slightly cooling the batteries.    The battery box vent fan will help move the air between the batteries.

If using LA batteries keep in mind that you will need to water them occasionally. Having a huge block of batteries with 48+ cells makes it difficult to reach over and water them and check the cables.    You may not mind it at first but as the years go by you will get tired of leaning and reaching way out to see in each cell as you water it.

Since the new string will rapidly age to match the old string you may be better off surviving on the old single string of 220 amp/hr batteries until they die and then replace them with a set of 400 amp/hr L-16s.    This would make your battery bank easier to service.

just my 2 cents.

DickyDck · June 2019

So being on the concrete might actually be a good thing, and these guys when they set it up, they made the shortest possible cables there or when putting the batteries in series so I’m not sure if I can get an inch between them because there’s no slack, but I can always just replace those cables. Thanks for all the advice guys!

DickyDck · June 2019

WaterWheel said:

Yes, You want at least a 1" air gap between batteries.    This helps the batteries to cool.    Sitting directly on concrete won't hurt the batteries and the concrete may act as a bit of a heat sink slightly cooling the batteries.    The battery box vent fan will help move the air between the batteries.

If using LA batteries keep in mind that you will need to water them occasionally. Having a huge block of batteries with 48+ cells makes it difficult to reach over and water them and check the cables.    You may not mind it at first but as the years go by you will get tired of leaning and reaching way out to see in each cell as you water it.

Since the new string will rapidly age to match the old string you may be better off surviving on the old single string of 220 amp/hr batteries until they die and then replace them with a set of 400 amp/hr L-16s.    This would make your battery bank easier to service.

just my 2 cents.

My original string is less than a year old, think it will kill the new string that bad?

Estragon · June 2019

It depends on the "real" age of the old string. A string that's been worked hard for a year could be "older" than a string that's spent a year mostly floating with the odd deeper cycle.

Don't know what your old string is, but using GC2 as an example, 3-5 years is a decent estimated life. Worked hard, it may be more like 2-3 years, and many of us make mistakes as we learn and adapt charging regimes to our use patterns, weather, etc. So if the old string has a couple of years left, is it better to add a new string that may age with the old string and replace the lot a couple years from now, or keep working the old bank hard, and plan for a higher capacity bank?

A set of 8 GC2s might be ~$800-900 (plus wiring). Assuming the new set ages out a couple years early by being paralleled, you could think of it as losing a few hundred $ worth of age. Lots of assumptions though, and different people have different priorities.

Personally, if the old string was worked hard and especially if it's showing signs of capacity loss, I'd work the existing until it dies and plan on an all new larger bank. If the old bank is still fine and was well maintained, I'd probably risk the couple hundred and add a string.

BB. · June 2019

To put numbers (my guesses) to your questions... I like the risk+reward method.... say your bank is good for 5 years (typical mid-range golf cart batteries).

Your bank is a year old, and adding a send set of golf cart batteries that last ~4+ years... Vs using the existing bank and replace after 2-3 more years, vs a new L16 bank that should last closer to 6-7 years.

And the issue of having to debug replace 1/2 (older batteries) of the battery bank in 2-4 years.

-Bill

Dave Angelini · June 2019

Well, he has to do something because XW will not work right with that small of a battery. It may not be enough capacity to work right with another string of GC's, but for 7 or 8 hundred it is worth a try. There could be other things in configuration that are not right also.

The installer should be involved as they are the ones who have a damaged reputation. They may not care....

DickyDck · June 2019

really quick... GC=Golf Cart?

and so I don't make another thread for something, "Clipping", is that an official term, and what does it mean? Try googling "Clipping" and you can imagine the nonsense I get for search results

someone over at solarpanel talk worked out a good calculation and said at best I was clipping with my battery bank being as small as it is, but I never thought about what it meant until now..... I know, I phail...

Estragon · June 2019

Yes, GC = Golf Cart.

BB. · June 2019

GC generally means 6 volt @ 200-230 AH Golf Cart deep cycle batteries. Typically less expensive because of the high volume.

Clipping is a limitations of your hardware (such as a charge controller) that limits (for example) charging current to XX Amps--Even though there may be more solar power available.

Clipping is also a common term for the output of any electric device that hits "hard limits" of output voltage/current when fed too much input (example, feeding to high of audio input to an amplifier--Clipping is a form of distortion).

For solar power systems... It is not uncommon to place a larger array on the input to a solar charger because the output of a solar array in warm/hot weather under full sun is actually less than the "marketing" numbers (panels are spec'ed at ~room temperature and Vmp falls to almost 80% of Vmp -- voltage maximum power -- as the sun heats the panels).

Generally, a good compromise is to assume solar panels+charge controller losses to be around 75-77% of "marketing numbers". As an example a 60 Amp MPPT charge controller on a 24 volt battery bank:

60 amps * 24 volts = 1,440 Watt "spec" array
60 amps * 29.0 volts charging * 1/0.77 panel+controller losses = 2,260 Watt array

A good quality MPPT controller will always "clip" its output to 60 amp maximum (in this example)--But in a moderate to warm climate, this does not happen often (in cool/clear weather around solar noon--Not too many days a year for not much time a day)--So does not really affect your overall "optimum" harvest.

Downside is heat is an enemy to electronics (and, frankly, batteries too)... Running a charge controller at 100% of rated output needs good cooling and air circulation around the controller.

Some people do decide to run at less than rated maximum current to keep the controller(s) cooler (longer life, less fan noise--if fans are installed).

-Bill

DickyDck · June 2019

Another question after re reading this thread, where are you guys finding these really cheap golf cart batteries? My crown Agm batteries were 200 a piece, maybe because they are AGM the cost goes up? I haven’t looked at FLA batteries as of yet.

littleharbor2 · June 2019

Costco, Sam's Club, less than $90.00 each. FLA, not AGM.

DickyDck · June 2019

Oh, I think those are very low amp hours aren’t they? My current string is 220Ah, but for experimental sake if they came in similar amp hour ratings I would have gone to Costco and picked up a bunch!

littleharbor2 · June 2019

Not sure of the current Ah. rating . Likely 210 - 220Ah. @ 6 volts.

DickyDck · June 2019

Well crap! Too late now since I just dropped 1600 on new agms, but for the same cost I could have gotten 16 new batts fresh to test this on. Oh well, I’ll know for next round!

Battery Monitor and/or Multiple temperature sensors

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