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Voltage Logger data on TM3 12V battery

electrongeek

Metrology Fanboy
Nov 1, 2019
69
75
Maine
I attached a Lascar EL-USB-3 Voltage Data Logger to my Sep 2019 TM3. Over a two week period, with average temperatures around 75F, voltage was logged at one minute intervals with the car in regular use. Minimum voltage seen was 12.50 volts, and maximum was 14.50 Volts, though those appear to be transients. Typically the minimum voltage was 12.75V before a 14.40 Volt top up charge cycle was initiated. Most of this time the vehicle was either in use or plugged into a wall charger. If this is truly a deep cycle battery, and I can't imagine that it isn't, these cycles don't appear to be something that places a great deal of stress on the battery, and I would expect to see a minimum of several years life unless the battery was defective or damaged. This based on my experience with battery banks on liveaboard boats.
TM3_12V battery.jpg
 

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RayK

Active Member
Apr 5, 2016
2,308
2,319
San Jose, CA
Can you provide a zoomed-in view of one (or more) of the 14.4V transients? I'm curious to see if it's an instantaneous switch to the higher charging voltage, or does it ramp smoothly. If you could repeat a couple of these charging cycles at a faster recording interval (like 1 sec) that would be great.
 
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acarney

Active Member
Jul 9, 2019
2,900
1,888
Richland, WA
Did the car always live in a happy range (say 40 to 70% SOC)? These batteries should last YEARS, like 200,000+ miles. It’s when you dip below 10% a lot or constantly charge to 100% that you stress it a lot. Extremely fast charging (supercharger) also puts stress on it. The level 2 speeds is completely find day in and day out though.
 

smatthew

Active Member
Jun 9, 2018
1,300
2,250
CA Bay Area
Did the car always live in a happy range (say 40 to 70% SOC)? These batteries should last YEARS, like 200,000+ miles. It’s when you dip below 10% a lot or constantly charge to 100% that you stress it a lot. Extremely fast charging (supercharger) also puts stress on it. The level 2 speeds is completely find day in and day out though.
Someone didn't read the original post......
 

acarney

Active Member
Jul 9, 2019
2,900
1,888
Richland, WA
The chart that the OP posted is for the 12V battery, not the high voltage battery. Supercharging or L2 charging the car should not have any relationship to this discharge/charge rate.

edit: Like @smatthew said....

Ah, literally the only spot 12V shows up is the post title. I would assume the 12V isn’t that much of a deal, unless it’s stupid hard to replace or something.
 

smatthew

Active Member
Jun 9, 2018
1,300
2,250
CA Bay Area
Ah, literally the only spot 12V shows up is the post title. I would assume the 12V isn’t that much of a deal, unless it’s stupid hard to replace or something.
You're right. All those mentions of 12.5Volts 14.5V, 12.75V, 14.4V in the post body couldn't mean anything.

Here's a hint. If your high voltage battery reads 12.5 volts, it's dead jim.
 
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RayK

Active Member
Apr 5, 2016
2,308
2,319
San Jose, CA
Can you provide a zoomed-in view of one (or more) of the 14.4V transients? I'm curious to see if it's an instantaneous switch to the higher charging voltage, or does it ramp smoothly. If you could repeat a couple of these charging cycles at a faster recording interval (like 1 sec) that would be great.
@electrongeek You may not have to repeat your experiment as I requested. I found a used Omega EL-USB-3 on eBay and it's on the way to my house. I would ask how you connected your logger to the car. Cigarette lighter... errr, sorry - 12V auxiliary power outlet, or directly to the 12V battery.
 

electrongeek

Metrology Fanboy
Nov 1, 2019
69
75
Maine
@electrongeek You may not have to repeat your experiment as I requested. I found a used Omega EL-USB-3 on eBay and it's on the way to my house. I would ask how you connected your logger to the car. Cigarette lighter... errr, sorry - 12V auxiliary power outlet, or directly to the 12V battery.

My logger came with leads ending in alligator clips. I just attached directly to the 12V battery.
 

SageBrush

REJECT Fascism
May 7, 2015
12,902
17,230
New Mexico
Looks like the longest 14 Volt charge session was about 2.5 hours
Thanks. Can you guesstimate average charging Amps ? I think that the OEM 12v is ~ 40Ah capacity but I don't have a chart handy to translate voltages into SoCs

... On second thought, I should just look up that chart since my interest is in estimating charging overhead
 

electrongeek

Metrology Fanboy
Nov 1, 2019
69
75
Maine
Thanks. Can you guesstimate average charging Amps ? I think that the OEM 12v is ~ 40Ah capacity but I don't have a chart handy to translate voltages into SoCs

... On second thought, I should just look up that chart since my interest is in estimating charging overhead

No way I can see to estimate charging amps. There is a rule of thumb to stop an absorption charge on lead-acid batteries when the charging current (at 14.4 V here ) drops to 3% of the amp-hour capacity of the battery, but no idea how Tesla handles all this.
 
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