Batterie bank monitoring system plans.

[HoBoPanda]

hello everyone.
This will be my first post on a new project I am staring. Last week in the datacenter at work we had both of our Big 3 phase UPS die. The great this is I got them  both to take apart and play with, But the big score it the batteries in them they just replaced in August 2015. The One UPS had 40 SLA1161 http://www.mrsolar.com/content/pdf/Interstate/SLA1161.pdf and the other had 72 HR-12120W http://www.csb-battery.com/upfiles/dow01461118859.pdf all new in the last 8 months.

Photos of the Batteries and the 2 units will be in this dropbox link
https://www.dropbox.com/sh/c16gdww2x0u7xod/AABBi1WsPnQEtl3Th2ERNUXYa?dl=0


So my plan is to build 28 banks of batteries 4 batteries each at 48V. This will give me 18 banks of the HR-12120W batteries and 10 banks of the SLA1161 batteries. What is am wanting is to monitor voltage and temp of each battery and on a per bank I want voltage and current. With a over all system voltage and current.


I had some ideas on how to do this
First was to run a cat5 cable to each battery bank connect the first 5 wires to the -+ of each batter so I can start at ground and work my up each batter to get voltage of each battery and the entire set over all voltage. then add in a current shut in on the negative and use one more withe to read current. this leaves me 2 wires to send a 5vdc and a one-wire buss and use come ds18b20 sensors on each battery. once having all of this built build out a big mux to read all of these sensors off a pi or arduino.

second idea is cheep arduino board for each bank get all my voltage, current and temp at a bank level and then query each arduino over a i2c buss from a raspberry pi as a master to collect the data and put in some type of database to look at over web.

some other ideas i think would be cool to add to each bank is a on/off mosfet so I can shut off each bank and read voltage under no load or stop charging and other things. this is something simple to add in to the end product for not much extra. I think on my scale this will work out well because pulling 100A 4800W over 28 banks of batteries will pull less then 4A each bank and simple to-220 mosfet or 2  will work well if i use a low RDS sub 20m? to keep loss down.

What I would like to know is there any products/projects out there that does this? or any input on how to make some thing of this scale. I will probably make both ideas above just to get a idea of what it will look like on a 2 or 3 bank system and get the ideas flowing for later revisions.

This new bank of batteries will get added to my other stash of equipment I have been collecting over the years to have a off grid house. I currently have 6 grape solar  GS-S-250-Fab5 panels not installed yet with 2 Morningstar TS-MPPT-60 charge controllers. this will be my solar input to charge and maintain my banks. I have some cheep china gridetie inverts 300W each x4  that I want to use to push power back to grid when I have a excess solar power. I also will have 2 modified APC SUA3000 UPS like what was done in this video series by knurlgnar24 https://www.youtube.com/playlist?list=PLdImEedbzeWSpxQpQpqnFEKa5NKYXXe-V one ups had double transformer and upgraded to 8 FB4710 mosfets on each side of the H bridge.

I will have more photos of things over the next few night as i take them apart and unload them in to the garage.

[HoBoPanda]

Some more photos. been working for the last week charging and topping off the 40 batteries in the second UPS. most of them started off at about 6 to 7v because they say for months with no charge at the office till i got them. I am about half way done getting them charged up and installing my new 10AWG jumpers to connect them.

[Apollyon25_]

One thing leaps to mind.

Put a series resistor at the battery side of the voltage sense wiring.
This is purely to limit the current in the wiring in the event of a short to GND or across any part of the string.
You'll have to pick a resistor value sized appropriately for your sense circuitry/metering.

I have seen what NOT having this looks like. Its not pretty and very dangerous.

[HoBoPanda]

I have been looking at this device for current since for the over all level. http://www.mouser.com/ProductDetail/Ohmite/TGHGCR0005FE/?qs=sGAEpiMZZMtlleCFQhR%2fzdb0trmPSydZDk7AWCyERCw%3d I cant decide if i want to use a package device like this 4 or 5 of them and add up the current to get total or get a cheep current shunt that is 500A 75mv off ebay.

As for the individual banks I it will end up being something low like .01 or even .005 don't want to loose the power lost in the connection. Yes Apollyon25_ the way I have it set up is dangerous but it was just to charge and test the batteries. I have ordered 4 sets of these to cover the post on the batteries. http://www.ebay.com/itm/331257016621 That should make it safer I am also putting in a 50A auto fuse in line with each bank. The final location where I install them they will be covered over the top and away from my DC breaker box. Also each bank will have a 10AWG wire to a breaker box with a 20A breaker for each of the 28 banks. so it will be safer then the big block of batteries I have now. I have played around with batteries to do some stick welding and it is scary the amount of power you can have in just 6 car batteries wired at 36v.

I have been working on the code to monitor each cell on a teensy 3.0 bit over kill but small and can be powered over usb from my laptop. I ended up doing 4 sets of differential op-amps to read each cell and used a 16 way mux 74HC4052. Testing with some 9v batteries on the bench and things seam to be working out well so far. I plan on cleaning up the code and testing on some small Arduino ATmega328s just cheep things off ebay for like $3 each.

[Melt-O-Tronic]

Why did the UPS's die?

I think you should load test each battery.  You may find that their capacities are now way below their ratings, especially after they discharged below 10V.

[edpalmer42]

Why did the UPS's die?

I think you should load test each battery.  You may find that their capacities are now way below their ratings, especially after they discharged below 10V.

+1 for this.

I've played with lots of UPSs over the years.  I've never seen a 12V UPS battery that was usable after the voltage dropped significantly below 12V.  The chemistry determines the voltage and it takes almost nothing to keep the open circuit voltage at 12V.  A lower voltage means something like dried out cells, sulphated cells, overheated cells, etc.  All of these are pretty much fatal.  There are lots of ways to rejuvenate these batteries, but I've never had any success with them.  YMMV

Good luck,

Ed

[HoBoPanda]

So I ended up testing all the batteries like Melt-O-Tronic said and i found 1 bad one out of the 40. I tested them by connecting 4 to make 48v and connected a ups to it with a 20A load on the batteries and checked each battery. I found that all of them sat at about 12.2 to 12.3v each but the one battery at the 20A load was down at about 7v. I think I got lucky that the batteries are good because they sat for probably 9 months if not more since they got installed with no charge and that is why the voltage was low when I got them. the second ups that had the bad batteries still works I can connect up the charges batteries and it works just fine. the reason they got rid of it is because it is old and the other ups got shorted out and they did not want to take a chance with either one so they bought 2 new 30KVA ones to replace them.

I also did a load test on the remaining 36 batteries and it ran a 10A ac load over night for about 6 half hours and the batterie voltage did not fall below 12v. the ups was pulling about 28A out of the batteries for that entire 6+ hours. 36 batteries at 44AH each is about 400AH at 48v and the over night test should have used about 182AH about half of the rated batterie capacity.

I have done more thinking on how I want my monitoring system to work. I have a working bank design working on the bench with 9v batteries. I ended up using a pair of IRFZ24N mosfets to turn on and off the bank from the load so I can monitor the batteries under load and no load. I am monitoring them battery by battery using differential op-amps with resistor dividers on each one to get a full scale 15v to 5v on the microcontroler

[HoBoPanda]

Got my battery boots this morning to cover the positive side of things. they are nicer then i though being they came from china.

[batteksystem]

Got my battery boots this morning to cover the positive side of things. they are nicer then i though being they came from china.

Look like chinese stuff. For quality stuff, you can look to VTE battery boots. Though quite expensive in my opinion.