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Made In China Model Y has 15.5 Lithium battery to replace 12V lead-acid

jcanoe

Active Member
Oct 2, 2020
4,361
4,529
Maryland
The current 12V lead-acid battery does not always fail quickly. There are many variables that determine the life of the battery including temperature, vibration and load. Tesla has revised the 12V charging parameters multiple times since the Tesla Model S was first introduced. The latest 12V charging programming may help prolong the life of the current 12V battery by not overcharging the battery. Tesla could have used a larger capacity 12V lead-acid battery that would last longer but at higher cost, space and weight. The LFP battery has the advantage in terms of size and weight. It is unknown how well the LFP 12V battery will perform in cold weather and if the life of the LFP 12V battery will be reduced in hot climates.
 
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Lead-acid 12V batteries in hot climates (leaving a car outside) like FL last up to 3 years. That's when they fail for me and that's the norm from what I've heard from repair shops. Not exactly what I'd call a long lifetime.

Interestingly, VW is replacing the AGM battery with li-ion (or LFP) in the 2022 ID.4 models. I believe they are replacing ones in 2021 models too.
From the list of benefits of the Ohmmu battery... the biggest benefit to a car like the ID.4 is the voltage sag issue.

 

e645824

Member
May 15, 2021
163
217
USA
The current 12V lead-acid battery does not always fail quickly. There are many variables that determine the life of the battery including temperature, vibration and load. Tesla has revised the 12V charging parameters multiple times since the Tesla Model S was first introduced. The latest 12V charging programming may help prolong the life of the current 12V battery by not overcharging the battery. Tesla could have used a larger capacity 12V lead-acid battery that would last longer but at higher cost, space and weight. The LFP battery has the advantage in terms of size and weight. It is unknown how well the LFP 12V battery will perform in cold weather and if the life of the LFP 12V battery will be reduced in hot climates.

I live in the Central Valley of California. I had been replacing my ICE 12V battery every 3 years before it fails. Prior to that lesson-learned, I had gotten stuck numerous times. The temperature here isn't as bad a Phoenix, but it does peak at 118 degrees some years. The Central Valley is actually a desert -- it is just green on the map because of the irrigation from the snow melt. Without that, it would be brown 9 months of the year.

So I am looking forward the new 12V (15.5V) lithium battery. I had planned on getting an Ohmmu next year (since the 12V lead-acid batteries in a Tesla fail more quickly due to the different load profile), but with the recent developments I would like to get a Tesla version instead just to be forward compatible and to get rid of the archaic lead battery terminal post connectors.

I understand that a new cable would be needed and perhaps a different battery management module in the car.

Scott

--

MYLR | Red ext | White int | 19" | 5 seats | tow | no FSD | made/delivered Oct 2021
 
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DonaldBecker

Member
Aug 24, 2020
155
180
95033
Not safely, at least without extra hardware. 15.5V is an overvoltage condition for lead acid batteries. Absolutely do not cable them together.

Car electronics are designed for over-voltage conditions. One of the tests is explicitly targeted at the mostly-obsolete practice of tow trucks using a 24V electrical system and long jump start cables. The voltage drop of the wires isn't a problem when you start with double the voltage.

The modern practice is to use a commercial jump start box, basically a heavy duty version of what you might buy for your glovebox. They often have four cells instead of three and put out 14.4V-16V depending on the charge level.
 

e645824

Member
May 15, 2021
163
217
USA
For the 2022 Model Y, this list shows that retrofitting the new 15.5 Volt battery for we 12V folks might also involve swapping the windshield washer fluid pump.

1639283173162.png

(cite: Ryan Shaw, https://youtu.be/zXwqX1JXtIg )


Scott

--

MYLR | Red ext | White int | 19" | 5 seats | tow | no FSD | made/delivered Oct 2021
 
My early 2018 Model 3 has a 45Ah lead acid battery. Like others have pointed out, not all of that 45Ah is usable. If the battery is a deep cycle, it could possibly use 50% (or 22.5Ah). If not a deep cycle battery, it could possibly use less than 20% (or 9Ah). I installed a shunt to monitor my 12v battery this summer (which is almost 4 years old and over 71,000 miles) and I have never seen it use up more than about 3Ah (about 7% of total capacity). So if I could get a retrofit of the new lithium ion battery my car would go twice as long before having to wake up and recharge it.

*Note that my car only using 7% of it's 12v battery capacity before recharging may need different than others. Tesla may be compensating for the age or some measurable quality of the battery and using less of the capacity as it ages.
 

jcanoe

Active Member
Oct 2, 2020
4,361
4,529
Maryland
My early 2018 Model 3 has a 45Ah lead acid battery. Like others have pointed out, not all of that 45Ah is usable. If the battery is a deep cycle, it could possibly use 50% (or 22.5Ah). If not a deep cycle battery, it could possibly use less than 20% (or 9Ah). I installed a shunt to monitor my 12v battery this summer (which is almost 4 years old and over 71,000 miles) and I have never seen it use up more than about 3Ah (about 7% of total capacity). So if I could get a retrofit of the new lithium ion battery my car would go twice as long before having to wake up and recharge it.

*Note that my car only using 7% of it's 12v battery capacity before recharging may need different than others. Tesla may be compensating for the age or some measurable quality of the battery and using less of the capacity as it ages.
My understanding is that the current Tesla 12V battery is a deep cycle, sealed maintenance free (MF) flooded lead acid battery. I recall reading that the Tesla Model 3 (assume the Model Y is similar) draws 25W when asleep, this power runs the alarm system, BT modem and LTE modem. If true, then 25W/12.6V=~2A load. Others have stated that the Tesla Model 3 will charge the 12V battery every 17 hours, that would mean charging after drawing 2A for 17 hours or ~34Ah (75%) out of 45Ah rated capacity. Maybe that is why the current 12V battery does not last more ~3 years in the Tesla vehicle. Perhaps there is a deep sleep mode that uses less power than 25W.
 
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My understanding is that the current Tesla 12V battery is a deep cycle, sealed maintenance free (MF) flooded lead acid battery. I recall reading that the Tesla Model 3 (assume the Model Y is similar) draws 25W when asleep, this power runs the alarm system, BT modem and LTE modem. If true, then 25W/12.6V=~2A load. Others have stated that the Tesla Model 3 will charge the 12V battery every 17 hours, that would mean charging after drawing 2A for 17 hours or ~34Ah (75%) out of 45Ah rated capacity. Maybe that is why the current 12V battery does not last more ~3 years in the Tesla vehicle. Perhaps there is a deep sleep mode that uses less power than 25W.
Those numbers sound about right. The shunt I installed doesn't have logging capabilities, so I don't know how often my car wakes up to charge the 12v battery. I just know that the hundreds of times I have come up to it (can see the battery monitor's screen through the window) never showed more than 3Ah used from the full capacity. It could be that my car wakes up very, very often to recharge my 12v battery. Or Tesla possibly changed the behavior for all cars to wake up more often and cycle the 12v batteries less deeply. I wish I had data logging capabilities in my battery monitor.
 

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