Battery Temp Limit

[PKsolar]

Can anyone explain why the classics come with a battery limit set at 169 degree C! That would destroy any battery bank. All three of ours was set 169-170C.

[Vic]

Hello PKsolar,

Am several Firmware revisions behind in Classic Firmware on the systems here.

But only know of two similar Limits on Classics;
In the Limits menu,  there is a upper and lower absolute Voltage Limit,  which limits the range of temperature-compensated charge voltage that the Classic delivers to the battery.   But these Limits are in Volts   ...

And there is the Reference Temperature  --  the temperature that centers the range of temperature compensation that is applied to Absorb,  Float,  and when set,  to EQ voltages.

In what menu are you seeing this 169 - 170 C setting,  and if you know,  what is the purpose of this setting?

Thanks,   Vic

[Vic]

PK..,

In looking at the 2056 Version of the Classic manual,  in the Limits menu,  there IS now,  a Battery Temperature Limit.

In a quick scan of the manual,  did not find any description of the function,  but assume that it Defaults OFF.  and 169 170 C,  would definitely disable this function.

So,  it appears that for those that want this function,  it will be up to them to decide just where this Limit should be set.

FWIW,   Vic

[PKsolar]

Thanks Vic!

That is our revision. Here's where this all comes from. My brother's batteries are kept in the basement box nice and cool with a fan so they can charge away when it's 90F and humid in S. WI and the AC is cranking cool air into the old farm house. Well, one day he did a quick check and noticed his battery box cooling  fan had stopped working. It was in Auto equalize mode and trying for hours to get over 55V but couldn't because the batteries were very hot. Talk'n extremely hot (190F + and boiling away taking years off the probable storage capacity). By pure chance he found the new setting and lowered the maximum to 32C and of course made sure it would not equalize on its own again. So it seems it is NOT a default OFF and allows the charger to just keep on charging at a high rate even when the batteries are about to burn up. Are we missing something here?

[Vic]

Hi PK..,

190 F battery temperature,  seems quite incredible!

Think that you are alluding to not ever wanting to do an Auto EQ,  ever again  --  completely agree with that.

Make certain that ALL charge sources use a Battery Temperature Sensor,  that is attached mid-way down the side of one battery,  in the center of the battery bank.

Do not EQ a battery that has not been fully-charged,  or nearly fully-charged.

Be certain to SET a Temperature Compensated EQ voltage.

Carefully monitor the system while doing an EQ.

EDIT:  Also,  set the EQ time to 00:00,  and press Enter.   Set the desired EQ Time, only when you want to do the EQ,  and then monitor the EQ process.  When you are finished with the EQ,  please set the EQ Time back to 00:00,  and press Enter<

AND,  a Charge Controller,  not even a Classic,  can know that much about one's system,  especially the battery bank.   There are a number of settings in CCs which should be done reasonably correctly,  given the nature of the system,  and the desires of the system master.  These include Charge and EQ voltage, duration,  EA value,  Temperature Compensation value,  and so on.

Some human needs to be responsible for the system setup,  monitoring and management.  The  Battery Temperature Limit was requested by several Members here.  There are tens-of-thousands of Classics that have been shipped without the ability to set this temp limit,  until the Firmware is Updated.

Some Default parameters can be damaging to batteries,  if someone does not know enough to set them differently at initial setup,  or,  from monitoring battery health deducing that the Defaults need to be changed.  And,  there are differences of opinion about just what should be the Default values.   Some may believe that Defaulting the battery temp limit to 90 F would be fine,  others  would shoot themselves,  if their batteries ever reached this temperature  ...  cannot see what might be an appropriate Default setting for this limit.

The systems here have done well without any battery temp limit for the past 11 years.  Most other CCs have no battery temp limit.   Am not certain what I would choose for this limit on the systems here.

Seems that MidNite Solar bends over backward,  to try to accommodate suggestions on enhancements on their products,   IMO. Each of these additions can create some costs,  and even some adverse comments ... 

Thermal Runaway of systems,  especially batteries can create a catastrophe.   Please monitor batteries carefully,  especially during EQ,  use BTSes and temperature compensate the EQ voltage.   This needs to be done by a responsible human,  IMO.  AND,  do not EQ a battery that is not fully-charged,  or very close to it.

FWIW,   Vic

[Vic]

Thanks Vic!
   ... So it seems it is NOT a default OFF and allows the charger to just keep on charging at a high rate even when the batteries are about to burn up. Are we missing something here?

PK..,

The Battery Temperature Limit appears to be set to a very,  very high temperature as the Default value.   This IS,  in effect,  shutting OFF this function.  It is as if this function had not been added in the recent FW versions ...   OFF,  as in,  essentially NOT there,  present or active.

The system manager simply needs to decide for the system environment,  usual battery temperature range,  etc,  what this parameter be set to,  if they wish to use it.

PKsolar said,   "   ...   the batteries were very hot. Talk'n extremely hot (190F + and boiling away   ...  ".

How was the battery temperature measured,  during the event noted  above?

Just trying to be clear.   FWIW,    Vic

[PKsolar]

Again, thanks for the extensive explanation Vic!

I'll print this out and pass this on to him. He's an electrician but still getting to understand PV/battery systems. I thought I had set up all the same limits as on my two classics, although I know he's pushing his single classic with a larger PV array than mine. You should see the cooling fins he added to the classic along with extra cooling fan. I had mounted my classics on finned aluminum plates to aid in cooling and it really makes a difference.

He might have mentioned the sensor had fallen off to the bottom of the box. Lots of lessons to be learned. Luckily, batteries are doing fine now. He used my old Point and shoot temperature gauge from when I did home assessments. We do love all our MS products and the great reading on the forum.
Cheers,
PK 

[Vic]

Hi PK,

Thanks for the info.

Regarding the battery temperature,  that 190 F reading is just astonishing,  to me.  The hottest battery that I've ever seen,  under any conditions,  is 90 degrees cooler that the battery you mentioned.   One system that I look in on,  is the Record Holder,  at 100 F ...

Regarding the BTS that had fallen off of a battery,  this can be caused by mounting the sensor on an unclean battery surface.   Cleanliness helps battery longevity,  considerably.

For battery banks here,  mount all BTSes half-way down the side of the same battery,  in the center of the bank.   All of the sensors are taped in place,  using 2" blue tape.   Then a sheet of Styrofoam (r) is placed over the sensors  --  the foam has an area hogged out to keep from mashing the sensors onto the battery,  too much.  The foam is held in place with a ratchet strap,  around the battery that is snugged up,  but gently so.    The sensors will not move,  and the 1.5 - 2" thick foam  helps isolate environmental temperature effects from affecting measured temperature from the BTSes.

Good Luck to you and your friend.  All opinions,  FWIW,    Vic

[PKsolar]

Great Idea and thanks again...

With his old eyes, he said it may have read 140F but he was blown away at the heat wave that hit him when he opened the lid. We'll strap both of them down with some insulation as cushion. He did find that the default value under Equalize temp comp (-5) is set to NO, so he switched that to YES!  That should prevent any problems in the future. Cheers, PK

[boB]

Vic is correct in that this 170 degree C default is "OFF".  The Classic used to NOT have
this function and someone needed it.  So, instead of setting it to something unreasonable,
we set it to this so there would be no issues with it being too low or whatever.
Also, there is no modbus menu for this value.....  Yet...  So this was set to OFF so
that these guys or anyone that could deal with modbus could use it right then and
there.

Sorry.  This will be changed eventually and a real menu added.  Hopefully not too long.

boB