M1G Low battery at 12.8V

[TriLife]

Greetings,

I'm doing some tests on my system autonomy during AC failure, sending an email when AC failure occurs and then again when Low Battery occurs.

The manual says it will trigger a low battery at 11.2V and shut down the system at 10.2V.

One hour into the test, I received the low battery email, with the battery reading 12.8V. I'm measuring the voltage at the battery terminals, two different testers indicating the same voltage...

That seems rather high.

Any idea, what could be the cause?

Cheers.

 

[RAL]

Are you measuring the 12.8V after the M1 has shutdown? 
 
What capacity battery are you using, and how old is it?
 
As the battery voltage drops under load, the M1 will shutdown and disconnect the load from the battery.  Once the load is disconnected, the battery voltage will typically bounce back to a higher voltage.  But 12.8V seems too high for a rebound voltage, as it would indicate that there is still substantial capacity left in the battery.
 
If you can, I would recharge the battery and run another test and check the battery voltage every 5 minutes or so to try and get a better idea of what the voltage is at the time it sends the low battery warning and at the time it shuts down.   When the voltage drops to the point where it hits the knee of the discharge curve, it can drop pretty quickly after that as it goes over the cliff.
 
If it is shutting down too early, one possible cause could be a poor connection between the battery and the M1 board.  So measuring the voltage at the VAUX terminals of the M1 would be a good idea, too.  That will give you an idea of what the M1 is actually seeing as its voltage.

 

[TriLife]

Hi RAL,

Measuring while AC is off, and the system is running.

3*8Ah in parallel, all batteries less than 4 months old, replaced at the same time.

System has been running on battery for the last 6hrs+ now, without a problem.

Voltage readings as I'm writing this:

Battery electrodes: 12.34V
M1 entrance: 12.34V
Vaux: 11.34V
Saux: 10.89V


All seems to be working as normal, with the exception of the "Low Battery" message I received.

 

[RAL]

Hi RAL,

Measuring while AC is off, and the system is running.

3*8Ah in parallel, all batteries less than 4 months old, replaced at the same time.

System has been running on battery for the last 6hrs+ now, without a problem.

Voltage readings as I'm writing this:

Battery electrodes: 12.34V
M1 entrance: 12.34V
Vaux: 11.34V
Saux: 10.89V


All seems to be working as normal, with the exception of the "Low Battery" message I received.

I unplugged my system and let it run on battery. 
 
Battery terminals:  13.5V  (a minute after removing AC power).
VAUX:   13.4V
SAUX:  13.4V
 
 
A drop of 0.1V is about what I would expect, just due to wire and terminal resistance.  I don't have much of a load on SAUX or VAUX, though.  But I'm surprised by the SAUX and VAUX values you see on your system.   They shouldn't be that low.

 

[TriLife]

Thanks for doing that test, RAL.

Vaux ist loaded with some temp sensors, the RF module and the XEP. Saux has the router on it... I'm guessing it's probably close to it's rated limit on both.

BTW, I got another Low Battery message about 9hrs into my test, this time about in line with an actual low voltage.

I read in the manual that the system does a battery test every 24hrs. I wonder, if that first low battery warning was triggered by that automated test...

 

[RAL]

Thanks for doing that test, RAL.

Vaux ist loaded with some temp sensors, the RF module and the XEP. Saux has the router on it... I'm guessing it's probably close to it's rated limit on both.

BTW, I got another Low Battery message about 9hrs into my test, this time about in line with an actual low voltage.

I read in the manual that the system does a battery test every 24hrs. I wonder, if that first low battery warning was triggered by that automated test...

 
Yes, I think it's possible that the battery test might have caused the low battery condition.

According to the manual, the M1 runs a low battery test for 30 seconds.  If the battery voltage drops too low during that time, it creates a low battery trouble condition.  It's not clear to me if that low voltage level is the same as the 11.2V level that causes the low battery condition during a power outage.  I suspect it is - but that bothers me because if the battery gets to that level after just 30 seconds, the battery is really shot.   I would prefer more advance warning than that, but I guess it's better than nothing.  So that's a good reason to replace the batteries every 3 to 5 years, even if you haven't received a trouble condition.
 
Going back to the voltages you measured, if you had 11.34V on VAUX, and assuming that's the same internal voltage that the battery circuit is seeing, then it didn't have  to drop very far to result in the trouble condition.
 
If you use the keypad and go to the system diagnostics menu (8-6-2), what voltage and current does it show when on battery ?  How does that compare to the VAUX voltage using a multimeter?

 

[TriLife]

Hi RAL,

The V/A reading (no AC) from the keypad shows 11.8V/1.54A, or 1.0V higher than the Battery and the same as VAUX.

With AC it shows 13.3V/1.9A. Battery shows 12.8V, still charging from yesterday's test...

At least I know, where I'm at with this.

I interrupted the test after 9hrs yesterday, when I got the Low Battery warning. I need to repeat and run the batteries down to self shut-off, to see, if the router resets to factory...

 

[RAL]

Hi RAL,

The V/A reading (no AC) from the keypad shows 11.8V/1.54A, or 1.0V higher than the Battery and the same as VAUX.

 

I'm not sure I follow what you see.   The keypad shows a voltage that is higher than the voltage you measured at the battery?  Or did you mean lower?
 
On my system, the voltage at measured at VAUX is about 0.1V lower than at the battery.  When I check the keypad, that's maybe another 0.1V lower.  But it's possible that it's not really lower, but just that the voltage of the battery had dropped another 0.1V by the time I run up the stairs and to the door where the keypad is.
 
If the keypad and VAUX voltages agree, that's good.  But I don't think you should see a 1.0V difference between those voltages and the battery itself.     A simple thing to try would be to remove and reattach the battery wires at the M1 battery screw terminals and make sure they are good and tight.   Also re-seat the push on terminals on the battery itself and make sure they are tight.
 

 

[RAL]

One additional question:  Once your batteries are fully recharged, what voltage do you see at the batteries?  It should be about 13.5V.

 

[TriLife]

The 3*8Ah have been charging for 45hrs now, since I got the Low Battery message. It currently reads 13.2V.

When I disconnected the AC to test the autonomy, they were reading 13.8V and dropped quickly to 13.5V.