Author Topic: Cell monitoring  (Read 11517 times)

Westbranch

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Re: Cell monitoring
« Reply #30 on: December 16, 2013, 10:25:13 PM »
From what I hears on CBC radio today, 3-D printers are about to 'make' the world overnight, again...
http://www.cbc.ca/ideas/episodes/2013/12/06/the-revolution-will-be-extruded/

Very interesting outlook.
KID FW1811 560W >C&D 24V 900Ah AGM
CL150 29032 V.2126-NW2097-GP2133 175A E-Panel WBjr, 3Px4s 140W > 24V 900Ah AGM,
2 Cisco WRT54GL i/c DD-WRT Rtr, NetGr DS104Hub Hughes 1100 Sat. Modem
Cotek ST1500 Inv  want a 24V  ROSIE Inverter
OmniCharge3024  Eu1/2/3000iGens
West Chilcotin 1680+W to come

RossW

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Re: Cell monitoring
« Reply #31 on: December 22, 2013, 12:42:40 AM »
So, I got 8 of these boards connected, finally.
The fact I have a failed cell was the final push - wanted to get some actual data to see what it tells me!

Like many here, I record the battery volts via the classic.
It's useful and told me quite a bit about what was going on.
Looks like this:


Clearly, battery volts died quickly around 12:30am resulting in the generator autorunning.

But wouldn't it have been nice to know just what was happening??

Well! Here it is!


And here's just the (worst) cell, split out to see:
3600W on 6 tracking arrays.
7200W on 2 fixed array.
Midnite Classic 150
Outback Flexmax FM80
16 x LiFePO4 600AH cells
16 x LiFePO4 300AH cells
Selectronics SP-PRO 481 5kW inverter
Fronius 6kW AC coupled inverter
Home-brew 4-cyl propane powered 14kVa genset
2kW wind turbine

Westbranch

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Re: Cell monitoring
« Reply #32 on: December 22, 2013, 01:03:40 AM »
Ross, am I reading things right and see that cell 25 is going bad too? :-[

What happened to cells 8 -24  with min of 0.00?
KID FW1811 560W >C&D 24V 900Ah AGM
CL150 29032 V.2126-NW2097-GP2133 175A E-Panel WBjr, 3Px4s 140W > 24V 900Ah AGM,
2 Cisco WRT54GL i/c DD-WRT Rtr, NetGr DS104Hub Hughes 1100 Sat. Modem
Cotek ST1500 Inv  want a 24V  ROSIE Inverter
OmniCharge3024  Eu1/2/3000iGens
West Chilcotin 1680+W to come

RossW

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Re: Cell monitoring
« Reply #33 on: December 22, 2013, 01:47:50 AM »
Ross, am I reading things right and see that cell 25 is going bad too? :-[

Which is cell 25? (I only have 1-24!)

Quote
What happened to cells 8 -24  with min of 0.00?

I built the first two boards (one with the RS232 interface, one without) to work out the code.
I built up two more boards (4, total) and put them on a real live battery string to make sure they did actually work in the environment. 4 boards, monitored 12 cells.
Of course, I did the "top" and "bottom" 12 cells. (1-6 and 18-24). Then, when more connectors came and I was able to complete the last 4 boards I put them in service.
All of the data has intermittent holes in it from where I've been either playing with stuff, or testing various things.
This is what "prototyping" is about <grin>

I also have only 6 temperature sensors connected (3 sensors on each of two boards). It's exactly the same code in each board, so if one works, they should all work.

I'm still adding some software features, so it'll be a bit on and off for a while, but it's basically a working gizmo.

Don't laugh... but here's a picture of how I've set up these test ones. In real use, they'll have lugs to go under the battery terminals - but I didn't want to disturb my setup just to add wires. Hence the clip-leads.


A possy of 'em!
3600W on 6 tracking arrays.
7200W on 2 fixed array.
Midnite Classic 150
Outback Flexmax FM80
16 x LiFePO4 600AH cells
16 x LiFePO4 300AH cells
Selectronics SP-PRO 481 5kW inverter
Fronius 6kW AC coupled inverter
Home-brew 4-cyl propane powered 14kVa genset
2kW wind turbine

Westbranch

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Re: Cell monitoring
« Reply #34 on: December 22, 2013, 01:06:43 PM »
Damn bumble fingers, SHB  22

In real use, they'll have lugs to go under the battery terminals

Ya, I had thought about that little issue, lots of dis/re-connecting to do...  do they make lugs that will fit larger bolts and small wire?  18ga?
« Last Edit: December 22, 2013, 01:13:22 PM by Westbranch »
KID FW1811 560W >C&D 24V 900Ah AGM
CL150 29032 V.2126-NW2097-GP2133 175A E-Panel WBjr, 3Px4s 140W > 24V 900Ah AGM,
2 Cisco WRT54GL i/c DD-WRT Rtr, NetGr DS104Hub Hughes 1100 Sat. Modem
Cotek ST1500 Inv  want a 24V  ROSIE Inverter
OmniCharge3024  Eu1/2/3000iGens
West Chilcotin 1680+W to come

RossW

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Re: Cell monitoring
« Reply #35 on: December 22, 2013, 02:48:57 PM »
Damn bumble fingers, SHB  22

In real use, they'll have lugs to go under the battery terminals

Ya, I had thought about that little issue, lots of dis/re-connecting to do...  do they make lugs that will fit larger bolts and small wire?  18ga?

My current thought is that I will use a larger lug and actually put the temperature sensor in it, then fill with thermal epoxy. That way, it'll be one wire for temperature sensing and voltage sensing, overcomes several things in one hit.

But I guess it will depend on what people want or need!
3600W on 6 tracking arrays.
7200W on 2 fixed array.
Midnite Classic 150
Outback Flexmax FM80
16 x LiFePO4 600AH cells
16 x LiFePO4 300AH cells
Selectronics SP-PRO 481 5kW inverter
Fronius 6kW AC coupled inverter
Home-brew 4-cyl propane powered 14kVa genset
2kW wind turbine

Westbranch

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Re: Cell monitoring
« Reply #36 on: December 22, 2013, 04:40:52 PM »
great idea!  ;D

will it matter which post it's on  + or -?
KID FW1811 560W >C&D 24V 900Ah AGM
CL150 29032 V.2126-NW2097-GP2133 175A E-Panel WBjr, 3Px4s 140W > 24V 900Ah AGM,
2 Cisco WRT54GL i/c DD-WRT Rtr, NetGr DS104Hub Hughes 1100 Sat. Modem
Cotek ST1500 Inv  want a 24V  ROSIE Inverter
OmniCharge3024  Eu1/2/3000iGens
West Chilcotin 1680+W to come

dgd

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Re: Cell monitoring
« Reply #37 on: December 22, 2013, 05:35:41 PM »
Ross,  I concur with ZB about a flashing light  not getting observed, often, but also concur about it being a stand alone unit as well.

But I also want it to be useful in its own right as a stand-alone system that could just draw your attention to a sick cell.

It probably depends on what level of Data Junky you are!  A Black Belt wants it all! Everywhere!

Personally I would want a remote beeper and light to annoy me when I am hunkered down in the computer den... ::)

Wb,
Hmmm, interesting usage.

I see this monitoring system as just an early warning to prepare for some serious depletion of the bank account. Since there is probably almost nothing one can do to FIX or cure a sick cell no matter how soon you detect its ailing.
Its will die anyway and getting it away from the other cells will hopefully prevent the 'bad apple in a barrel' syndrome.
Leds, lights, bells, whistles, warnings, electric shocks etc not necessary. Happy if it just sent me a soothing email apologising for impending financial poverty.   :)

dgd
« Last Edit: December 23, 2013, 02:49:14 AM by dgd »
Classic 250, 150,  20 140w, 6 250w PVs, 2Kw turbine, MN ac Clipper, Epanel/MNdc, Trace SW3024E (1997), Century 1050Ah 24V FLA (1999). Arduino power monitoring and web server.  Off grid since 4/2000
West Auckland, New Zealand

RossW

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Re: Cell monitoring
« Reply #38 on: December 22, 2013, 05:56:43 PM »
I see this monitoring system as just an early warning to prepare for some serious depletion of the bank account. Since there is probably almost nothing one can do to FIX or cure a sick cell no matter how soon you detect its ailing.
Its will die anyway and getting it away from the other cells will hopefully prevent the 'bad apple is a barrel' syndrome.
Leds, lights, bells, whistles, warnings, electric shocks etc not necessary. Happy if it just sent me a soothing email apologising for impending financial poverty.   :)

I actually disagree. We've been talking this to death in IRC. What it's telling us, what it proves (and disproves) etc.
Since I have AGM cells, the idea of just cooking them hard to equalize like you might FLA isn't an option. But it DOES suggest that a charge-sharing system MIGHT help. Early indications that a cell is getting over (or under) charged - ie, OUT OF BALANCE - means you might be able to give it some remedial attention while it's only "slightly out of balance" before you kill it.
3600W on 6 tracking arrays.
7200W on 2 fixed array.
Midnite Classic 150
Outback Flexmax FM80
16 x LiFePO4 600AH cells
16 x LiFePO4 300AH cells
Selectronics SP-PRO 481 5kW inverter
Fronius 6kW AC coupled inverter
Home-brew 4-cyl propane powered 14kVa genset
2kW wind turbine

dgd

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Re: Cell monitoring
« Reply #39 on: December 22, 2013, 06:13:50 PM »

I actually disagree. We've been talking this to death in IRC. What it's telling us, what it proves (and disproves) etc.
Since I have AGM cells, the idea of just cooking them hard to equalize like you might FLA isn't an option. But it DOES suggest that a charge-sharing system MIGHT help. Early indications that a cell is getting over (or under) charged - ie, OUT OF BALANCE - means you might be able to give it some remedial attention while it's only "slightly out of balance" before you kill it.

Ok, perhaps I'm just too cynical. Having spent too long and been optimistic about recovering 'going bad' cells, just to always be disappointed, I sort of thought that recovery was wishful thinking.
But I defer to your logic as 'out of balance'  and 'remedial attention' before it topples over looks a useful approach to prolonging battery life (in theory!).
And this monitor possibly coupled with a charge sharing system, I assume such as a BMS on LiFePO cells,
looks like a useful tool.
I suppose the trick will be deciding how far the deviation in voltage means starting to need this remedial action.

dgd
Classic 250, 150,  20 140w, 6 250w PVs, 2Kw turbine, MN ac Clipper, Epanel/MNdc, Trace SW3024E (1997), Century 1050Ah 24V FLA (1999). Arduino power monitoring and web server.  Off grid since 4/2000
West Auckland, New Zealand

RossW

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Re: Cell monitoring
« Reply #40 on: December 22, 2013, 06:26:38 PM »
Ok, perhaps I'm just too cynical. Having spent too long and been optimistic about recovering 'going bad' cells, just to always be disappointed, I sort of thought that recovery was wishful thinking.

I agree, once VRLA (SLA, AGM etc) are dead, I don't think you can do anything to bring 'em back.


Quote
But I defer to your logic as 'out of balance'  and 'remedial attention' before it topples over looks a useful approach to prolonging battery life (in theory!).
And this monitor possibly coupled with a charge sharing system, I assume such as a BMS on LiFePO cells,
looks like a useful tool.

That's what we've been talking about (again, in IRC) - ways and means to detect the early signs of imbalance, and then shunt some power around charged cells to give undercharged cells a bit of a lift.

My personal opinion is that LFP (LiFePO4) will explode and catch fire if they're let go too badly out of balance, so everyone uses a BMS because it's mandatory to do so, whereas lead-acid (usually FLA) doesn't do that, and just overcharging (ok, lets give it a funky name 'equalizing') has been the accepted practice. It works well enough, it just became the defacto "standard way to do it". Doesn't mean it's the RIGHT way. But it's largely non-destructive, and certainly cheaper than additional bits.

BUT it doesn't work with sealed cells. I reckon if we payed the same attention to balancing AGM as we are forced to with LFP, then AGM would probably last far far longer and be far less finniky than we're used to.


Quote
I suppose the trick will be deciding how far the deviation in voltage means starting to need this remedial action.

Not enough data (yet) to know, but this project just may be the one to change all that.

Out of curiosity yesterday, I looked at some 16-bit ADC. (that would give around 2mV/cell resolution on a 48V bank).
At over $400 for a 6-channel board, you'd need 4 of them for a 48V bank. Plus a computer. Plus someone to write the software to collect the data and do things with it. I don't see anyone but the real die-hards doing that!

However, if you could monitor every cell in your battery for (lets say) $10/cell, would you? (I reckon lots would)
3600W on 6 tracking arrays.
7200W on 2 fixed array.
Midnite Classic 150
Outback Flexmax FM80
16 x LiFePO4 600AH cells
16 x LiFePO4 300AH cells
Selectronics SP-PRO 481 5kW inverter
Fronius 6kW AC coupled inverter
Home-brew 4-cyl propane powered 14kVa genset
2kW wind turbine

zoneblue

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Re: Cell monitoring
« Reply #41 on: December 23, 2013, 12:47:55 AM »
Cool, great progress Ross. How are you getting the serial data stream out to your network? Or is this still laptop out in shed prototype?
6x300W CSUN, ground mount, CL150Lite, 2V/400AhToyo AGM,  Outback VFX3024E, Steca Solarix PL1100
http://www.zoneblue.org/cms/page.php?view=off-grid-solar

RossW

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Re: Cell monitoring
« Reply #42 on: December 23, 2013, 05:10:20 AM »
Cool, great progress Ross. How are you getting the serial data stream out to your network? Or is this still laptop out in shed prototype?

An old single-port terminal-server. (Argus TS-1). There are thousands of these sorts of things out gathering dust. Lots don't immediately "look" like they're useful, but they are. Even UPS serial interfaces.
3600W on 6 tracking arrays.
7200W on 2 fixed array.
Midnite Classic 150
Outback Flexmax FM80
16 x LiFePO4 600AH cells
16 x LiFePO4 300AH cells
Selectronics SP-PRO 481 5kW inverter
Fronius 6kW AC coupled inverter
Home-brew 4-cyl propane powered 14kVa genset
2kW wind turbine

RossW

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Re: Cell monitoring
« Reply #43 on: December 23, 2013, 05:27:48 AM »
great progress Ross.

Just a quick shot from last night. Ran the genset because we'd had very little sun during the day.
Overnight discharge curve is VERY different... in no small part because I was able to actually see which cell(s) were going to be trouble!

(this is also with now just one, 500AH bank instead of two)
3600W on 6 tracking arrays.
7200W on 2 fixed array.
Midnite Classic 150
Outback Flexmax FM80
16 x LiFePO4 600AH cells
16 x LiFePO4 300AH cells
Selectronics SP-PRO 481 5kW inverter
Fronius 6kW AC coupled inverter
Home-brew 4-cyl propane powered 14kVa genset
2kW wind turbine

Westbranch

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Re: Cell monitoring
« Reply #44 on: December 23, 2013, 02:23:44 PM »
presumably the one with all 12 good cells??  Looks like one could almost identify this set within the other one...
« Last Edit: December 23, 2013, 02:25:57 PM by Westbranch »
KID FW1811 560W >C&D 24V 900Ah AGM
CL150 29032 V.2126-NW2097-GP2133 175A E-Panel WBjr, 3Px4s 140W > 24V 900Ah AGM,
2 Cisco WRT54GL i/c DD-WRT Rtr, NetGr DS104Hub Hughes 1100 Sat. Modem
Cotek ST1500 Inv  want a 24V  ROSIE Inverter
OmniCharge3024  Eu1/2/3000iGens
West Chilcotin 1680+W to come