Model 3 low voltage battery warning

JeffKeryk

JeffKeryk

Joined
Jan 9, 2010
Messages
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Location
Los Gatos, CA
Tesla Model 3 uses a low voltage battery, a 51R like in a Honda 4 banger, to operate the locks, windows, lights and probably some other functions. After about 2022 they switched to a higher voltage Lithium Ion I believe.
These can go out, like any other battery. I got the warning message to schedule battery replacement service. The car runs fine but if the battery fails completely the vehicle is bricked; that's my understanding. It is suggested to get the work done within 2 weeks; more warnings will be displayed if necessary.
Some owners believe the battery still has a lot of life and just reset the warning message. I won't follow their advice...

I could go to Costco and get a Interstate lead acid battery for about $90 or an AGM for $170 and swap it myself. The stocker is a lead acid; nothing special. Tesla sells the battery for about $85 with no core necessary.
Tesla will come out this Friday and swap it out; I am past the 4 year warranty so the charge is $120 all in. Battery + Tax + Install Labor. They will also perform a rear seat belt recall of some kind.

The battery replacement involves opening all the doors, turning off the car system, removing frunk cowl for battery access, remove negative terminal, pull up rear seat and remove high voltage battery connection, remove positive terminal and swap battery. Reverse the process to finish up. 15 minute job once you have the replacement battery.

This is my 2nd battery replacement in a month! An AGM for the RX and now the Tesla.
Question: Can I use an AGM in place of the lead acid? Might be doing this again in 5 years, who knows?
 
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I think that AGMs want a bit higher charging voltage than the lead acid. If it's not possible to up the charging voltage to the AGM from Tesla I'd probably just go with the lead acid even if I would prefer the AGM. I know VW has a setting that can be set by dealers for battery type because of this.
 
thastinger said:
It's a 2018 car, so if you get the AGM and it lasts 5 years, you'll need to replace it at the same time as the main battery pack. I would get the AGM.
Click to expand...
Do you understand my question? It has nothing to do with the high voltage battery. That lasts 200K to 300K miles.
 
dogememe said:
LOL! He's probably not going to need to replace the main battery anytime soon…
Click to expand...
Probably best to just one liner the trolls and move on unless you want to argue and waste your time for 3 pages like I tend to do when I get bored. 😂
JeffKeryk said:
Do you understand my question? It has nothing to do with the high voltage battery. That lasts 200K to 300K miles.
Click to expand...
He’s looking to get a rise out of someone. He doesn’t know squat about batteries most likely. I dealt with automotive electrical low voltage systems for 15 years. I’ve installed 12V equipment in Tesla Model Ss before but I don’t know what the charging voltage is for the 12V system is in a Tesla when the ignition is on. It really has no reason to really juice the battery but if it’s under 14V ignition on it’ll be too low voltage for an AGM and you’ll risk it wearing out sooner.

For context newer ICE vehicles running flooded lead acid batteries tend to drop alternator output to charge in the 12.5 to 12.8V to reduce heat and strain on the battery. Before these battery monitoring systems became common 13.8-14.4V engine running was the usual charging output. That’s what you’ll want to keep an AGM battery happy and why monitored charging systems should be set for the associated battery.

If you have access to a multimeter you can check the voltage at the battery. I’d just leave your phone or whatever you use for the key in the vehicle, switch to drive and check what voltage you have. I thought they used AGMs now but I never looked at mine. If mine was in fact AGM and I checked the voltage it probably wouldn’t help if they changed battery programming when that happened.
 
Torrid said:
Probably best to just one liner the trolls and move on unless you want to argue and waste your time for 3 pages like I tend to do when I get bored. 😂

He’s looking to get a rise out of someone. He doesn’t know squat about batteries most likely. I dealt with automotive electrical low voltage systems for 15 years. I’ve installed 12V equipment in Tesla Model Ss before but I don’t know what the charging voltage is for the 12V system is in a Tesla when the ignition is on. It really has no reason to really juice the battery but if it’s under 14V ignition on it’ll be too low voltage for an AGM and you’ll risk it wearing out sooner.

For context newer ICE vehicles running flooded lead acid batteries tend to drop alternator output to charge in the 12.5 to 12.8V to reduce heat and strain on the battery. Before these battery monitoring systems became common 13.8-14.4V engine running was the usual charging output. That’s what you’ll want to keep an AGM battery happy and why monitored charging systems should be set for the associated battery.

If you have access to a multimeter you can check the voltage at the battery. I’d just leave your phone or whatever you use for the key in the vehicle, switch to drive and check what voltage you have. I thought they used AGMs now but I never looked at mine. If mine was in fact AGM and I checked the voltage it probably wouldn’t help if they changed battery programming when that happened.
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Yours is the Lithium Ion 16V, a completely different setup, voltage, everything. You will not have this problem.
1691536906302.png

Here's the lead acid battery in mine:
1691537045980.png
 
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JeffKeryk said:
Yours is the Lithium Ion 16V, a completely different setup, voltage, everything. You will not have this problem.
View attachment 171634
Here's the lead acid battery in mine:
View attachment 171635
Click to expand...
That's what I thought. I never looked to see what the voltage was though, I didn't realize they went to 16V, charging must be 18V+ then. AGMs like a good dose more power than their nominal resting voltage when charging.
 
JeffKeryk said:
Tesla will come out this Friday and swap it out; I am past the 4 year warranty so the charge is $120 all in. Battery + Tax + Install Labor. They will also perform a rear seat belt recall of some kind.
Click to expand...
Tesla will COME OUT & replace it for $120?? In addition to performing a recall repair? That has to be the best deal I've ever heard of!
 
bullwinkle said:
Tesla will COME OUT & replace it for $120?? In addition to performing a recall repair? That has to be the best deal I've ever heard of!
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Tesla service comes to you. Roadside is free; the install is the same as if I brought the car in. Free if it went bad within 4 years. I am at 4 years 8 months.
Of course there are a lot of Teslas around here; if you were in another area it roadside not be so fast.
 
bullwinkle said:
Tesla will COME OUT & replace it for $120?? In addition to performing a recall repair? That has to be the best deal I've ever heard of!
Click to expand...
I missed this part when reading somehow. I'd do that in a heartbeat. The battery for my GTI was $260 when I just looked at my last receipt. $120 is a steal and the OEM lasted me 5 years as well.
 
Torrid said:
That's what I thought. I never looked to see what the voltage was though, I didn't realize they went to 16V, charging must be 18V+ then. AGMs like a good dose more power than their nominal resting voltage when charging.
Click to expand...
Good to know. If and when I do it again, I will not go AGM. That was actually my main question.
 
Torrid said:
I missed this part when reading somehow. I'd do that in a heartbeat. The battery for my GTI was $260 when I just looked at my last receipt. $120 is a steal and the OEM lasted me 5 years as well.
Click to expand...
It would be $85 + tax if I went to the service center and bought it myself, a few miles away.
 
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