Battery temperature sensor location

This question has been debated with differing opions, reason and rationale, below is an excerpt from a Schneider manual, so with one word answers, without need for reasons, just state Terminal or Side
I'm taking a pole of opinions, thought it would be interesting what the outcome would be.
REMEMBER ONE WORD
(1) Install the BTS sensor on the battery.
I'm taking a pole of opinions, thought it would be interesting what the outcome would be.
REMEMBER ONE WORD
(1) Install the BTS sensor on the battery.
Method (a) involves mounting the sensor to the
negative battery post which allows the internal
battery temperature to be sensed providing the
most accurate results.
Method (b) attaches the sensor to the side of
the battery using the self-adhesive backing
which also provides good results in most
situations.
1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Comments
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
I know you are not looking for a reason but... The terminal has a direct, very heat-conductive connection to the battery itself, and so will accurately reflect the temperature of the battery. The plastic outside of a battery is not very heat-conductive, so whatever temperature it reads will not reflect as much the temperature of the battery, and will be more influenced by the ambient air.
-Bill
If you are forced to use it on a side, add a layer of thermal insulation like fiberglass or foam to keep the ambient temps from interfering.
KID #51B 4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
West Chilcotin, BC, Canada
ONLY on the side of one battery in the center of the bank, and only under a rigid foam sheet one, or more inches thick. With multiple strings of batteries it becomes a bit problematic, so would get rid of multi strings, and then place BTS under one battery center of the bank, half way down the side, under rigid foam on the single string of batteries.
Also, would place ALL BTS/RTSes on the same battery, under the same foam sheet -- very easy.
Heat rises, and resistance in battery interconnect crimps and between interconnect lugs and battery terminals will cause heating. Both of these can cause errors in the "battery" temperature that the RTS mounted on a battery lug/terminal, reports to chargers.
IMO, Vic
How would that benefit them?
You will need to ask those manufacturers. Vic
You will likely discover that the more actual field experience a person has, the more they lean to toward side mount, sandwiched between batteries - when insulated properly. The reasons have already been described.
Post mounting is quick and easy to install. And in some cases, it can be better - but then.......
Marc
To each his own, that's why there are options. Some people don't have spaces between batteries and they tent to heat up each other faster so a side mount might work if you are short on space.
KID #51B 4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
West Chilcotin, BC, Canada
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
There is not one correct answer if you want optimum results. So a one word answer is worthless. And yes, we have run tests on this in the field.
Marc
A lot depends on the space around the bank too, if it's just slightly larger than the bank itself and lined with wood and vinyl flooring over wood or if it's a large concrete room.
My bank is in the former.
No one answer covers it but If I were to place a sensor, I'd use an LED thermometer at peak usage time around all of the cells and from there determine a location for a sensor. If the cells were enclosed with forced air circulation I'd use a thermal probe and DVM, slow but it may be the best way available without a lab.
Anyway, I would "think" that the terminal would be a less than wonderful sensor location because the cable itself is a heat sink while cell innards have less opportunity to vent heat.
Oh, P.S. without a corrective action plan after determining that there is excessive temperature, knowing the results of testing is useless.
When I set up in a colder environment I tend to use boxes to house banks for better monitoring with less heat loss, in warmer environments I use boxes, but to mitigate heat gain.
I always use enclosures though but for different reasons in different climates.
Batteries that are too hot or too cold are not happy.
Whether I am installing at the north pole or on the equator, I set it up to maintain the battery enclosure at 70 to 74 degrees. Sometimes it's by heating and sometimes by cooling but the battery ambient temperature is always a controlled variable since it is so critical to the system life.