Has anyone replaced their 12V battery yet?

[Salted]

Snake oil

You guys need larger pictures. /s

Seriously though, can you explain why not? I've yet to see the idea debunked beyond similar outright dismissal. I'd be fine if someone who knows the Tesla systems pointed out clear reasons using "a larger capacitor" to improve bass demands won't work. Maybe the sub amp runs off the traction battery? :shrug:

 

[dmurphy]

You guys need larger pictures. /s

Seriously though, can you explain why not? I've yet to see the idea debunked beyond similar outright dismissal. I'd be fine if someone who knows the Tesla systems pointed out clear reasons using "a larger capacitor" to improve bass demands won't work. Maybe the sub amp runs off the traction battery? :shrug:

It’s a digital amp. On, off. 1s and 0s. You’re not going to make the 1s “stronger” because the input battery is lithium vs AGM.

If you’re replacing the amps, that’s one thing. But if you’re just talking about leaving it all alone, and just changing the battery, it’s not really affecting a thing.

good detailed link: Tesla Model 3 Stereo - Part 9: Summary and Lessons Learned

 

[Salted]

It’s a digital amp. On, off. 1s and 0s. You’re not going to make the 1s “stronger” because the input battery is lithium vs AGM.

These are still analog speakers? The amps convert the bits to analog which drives the speaker cones. Enough power must be available or we get clipping and distortion.

If you’re replacing the amps, that’s one thing. But if you’re just talking about leaving it all alone, and just changing the battery, it’s not really affecting a thing.

That's an excellent writeup, thanks. And it's good to read his results. If true for all our premium systems then the stock amp has all the juice it needs to drive the subs we have at any volume, and I must concede a bigger battery should not make any difference vs. a good OEM battery.

Might be interesting to blind test those who could hear a difference with lithium and if they can tell it apart from a new OEM battery. I recall hearing there were a slew of 3s delivered with nearly failing 12V AGMs.

 

[Jedi2155]

These are still analog speakers? The amps convert the bits to analog which drives the speaker cones. Enough power must be available or we get clipping and distortion.


That's an excellent writeup, thanks. And it's good to read his results. If true for all our premium systems then the stock amp has all the juice it needs to drive the subs we have at any volume, and I must concede a bigger battery should not make any difference vs. a good OEM battery.

Might be interesting to blind test those who could hear a difference with lithium and if they can tell it apart from a new OEM battery. I recall hearing there were a slew of 3s delivered with nearly failing 12V AGMs.

Lithium vs. Lead Acid are both DC power sources. There won't be a difference here. Lead actually has more power capacity than Lithium in many cases....

 

[neurocutie]

It’s a digital amp. On, off. 1s and 0s. You’re not going to make the 1s “stronger” because the input battery is lithium vs AGM.

gonna have to disagree with that statement. That it is a "digital amp" is almost irrelevant. You certainly don't want actual '1's and '0's going into your speakers -- will sound terrible. Anyways, yes it all will be analog in the end, even if the amp is class D and is using PWM. But supposing it were dumping '1's, you certain CAN make the 1s "stronger" -- the pulses can be 0.1watt, or 1watt or 10watts or 100watts (divide by E or I if you want I or E).

In this case, since car audio amps are designed to run off of 12V, it is I that matters (current). A powerful car audio amp can draw quite a bit of power, and given 12V, therefore current, upwards of 50A or more. So it matters whether the 12V power system can supply the currents needed. If the lithium battery has greater capacity, it will certain make for louder music, especially the bass notes. Capacitors can help by delivering added current for short intervals (smoothing out voltage spikes by supplying current).

In high powered ICE car audio systems, the alternator often determines the max power (current since its all 12V) available and folks install higher capacity alternators just to have more power available for their sound systems. Of course if the sound system is only a measely 10-20 watts, its not going to make any difference...

 

[smatthew]

gonna have to disagree with that statement. That it is a "digital amp" is almost irrelevant. You certainly don't want actual '1's and '0's going into your speakers -- will sound terrible. Anyways, yes it all will be analog in the end, even if the amp is class D and is using PWM. But supposing it were dumping '1's, you certain CAN make the 1s "stronger" -- the pulses can be 0.1watt, or 1watt or 10watts or 100watts (divide by E or I if you want I or E).

In this case, since car audio amps are designed to run off of 12V, it is I that matters (current). A powerful car audio amp can draw quite a bit of power, and given 12V, therefore current, upwards of 50A or more. So it matters whether the 12V power system can supply the currents needed. If the lithium battery has greater capacity, it will certain make for louder music, especially the bass notes. Capacitors can help by delivering added current for short intervals (smoothing out voltage spikes by supplying current).

In high powered ICE car audio systems, the alternator often determines the max power (current since its all 12V) available and folks install higher capacity alternators just to have more power available for their sound systems. Of course if the sound system is only a measely 10-20 watts, its not going to make any difference...

But don't forget - not only do you have a 12V AGM as a 12V power source in the car, you also have the Power Conversion System, which puts out 2.5kW of 12Vish power.

 

[neurocutie]

But don't forget - not only do you have a 12V AGM as a 12V power source in the car, you also have the Power Conversion System, which puts out 2.5kW of 12Vish power.

these two are not, of course, bussed together. If the audio system is powered by the DC-DC converter (in retrospect, it probably is), then of course the 12V battery, whatever it is, is completely irrelevant.

 

[smatthew]

Yes they are bussed together. The electronics in the car are powered by the 12V rail. The 12V rail is supplied by a) the 12V AGM battery, and b) when the car is on, or the battery gets low, the DC-DC converter (Also known as PCS) is generating 12v to supply the battery and the electronics.

 

[Salted]

Yes they are bussed together. The electronics in the car are powered by the 12V rail. The 12V rail is supplied by a) the 12V AGM battery, and b) when the car is on, or the battery gets low, the DC-DC converter (Also known as PCS) is generating 12v to supply the battery and the electronics.

Honest question: Is that accurate EE usage of "buss"? My amateur knowledge thought of it as meaning a direct physical linkage uninterrupted by other circuits, certainly by other decision making activity which would delay any response and be of little use for real-time audio reproduction needs. But, I'm wrong quite often.

 

[Jedi2155]

Lithium vs. Lead Acid are both DC power sources. There won't be a difference here. Lead actually has more power capacity than Lithium in many cases....

Wondering why there are 2 disagree's on my comment @t00shay & @lUtriaNt. Lithium-ion has its pro's & con's but lead acid still have specific scenarios where it can be a better use than lithium. Tesla focuses on the best solution and there are very good reasons they didn't put a lithium ion battery as the 12v pack.

 

[Adam3]

Better bass response has been mentioned by several people on the forum as well as amazon reviews. One forum member estimated 25% improvement. I like Ohmmu's lithium 12V replacement but I worry about it's built-in BMS that can fail.

 

[smatthew]

Honest question: Is that accurate EE usage of "buss"? My amateur knowledge thought of it as meaning a direct physical linkage uninterrupted by other circuits, certainly by other decision making activity which would delay any response and be of little use for real-time audio reproduction needs. But, I'm wrong quite often.

Let me explain how it's connected and you tell me. The only + connection to the battery is to vcfront. The only + connection to the PCS is to vcfront. Both connections enter, go through a mosfet switch, then a current shunt, then they both connect and feed to the rest of the car. The combination of mosfets and current shunt(s) is what allows the model 3 to not use fuses. There's a little circuit that measures the current and if too much power is being transferred it shuts the connection off, like blowing a fuse - except the efuses can be reset according to certain parameters.

The connection for the battery goes through 4 mosfets, and 1 current shunt. There's also a much smaller sleep mode bypass e-fuse that only activates under 500ma current draw (i.e. when car is sleeping).
The connection to the PCS (which is providing up to ~200 Amps) has 8 mosfets and 2 current shunts. Tesla specifically mentions that the largest e-fuse in the car is 193A, which must be the PCS efuse.

And according to the power state truth table, the status of the Battery and PCS connection is always the same - of course unless something goes wrong. Based upon the circuit board, and how power works, Tesla expects all of the power used by the car when it is not sleeping to come from the PCS, with the 12V battery basically acting as a buffer.
So the PCS and Battery are directly connected, notwithstanding the 2 efuse assemblies.

 

[smatthew]

Better bass response has been mentioned by several people on the forum as well as amazon reviews. One forum member estimated 25% improvement. I like Ohmmu's lithium 12V replacement but I worry about it's built-in BMS that can fail.

I would love to see a test where someone compared using a lithium 12v battery to adding a big-honking car stereo capacitor. Since the battery is just functioning to smooth the power.

 

[gtmotor]

Mine just stranded me. It popped the warning yesterday and I setup a service appointment but it's still 2 weeks out. No local places seem to stock this battery and my closest service center is almost 3 hours away.

Car jumped just fine with my mobile jump pack that my wife brought me.

Car has 26k miles, is driven regularly, and ALWAYS garaged. I wonder if they'll cover it under warranty... going to suck to be without the car for 2 weeks due to this issue.

 

[Atari2600]

Better bass response has been mentioned by several people on the forum as well as amazon reviews. One forum member estimated 25% improvement. I like Ohmmu's lithium 12V replacement but I worry about it's built-in BMS that can fail.

Did they do a before and after SPL meter test using the exact same source? 20% improvement of what?

I don't trust anything that's not scientific.

Car has 26k miles, is driven regularly, and ALWAYS garaged. I wonder if they'll cover it under warranty... going to suck to be without the car for 2 weeks due to this issue.

Why would it not be covered under your 4 year/50k mile portion of the warranty?
https://www.tesla.com/sites/default/files/downloads/tesla-new-vehicle-limited-warranty-en-us.pdf

 

[dmurphy]

Did they do a before and after SPL meter test using the exact same source? 20% improvement of what?

I don't trust anything that's not scientific.

Entirely my point. The only actual data we've seen (see the link I posted above) shows a full response right through the entirety of the digital amplifier's capabilities. Perfectly smooth, no clipping, no dropouts, no issues whatsoever - with the AGM battery.

Adding a lithium battery - or even a capacitor - will have zero impact on that curve. None, nada, zip, zilch, nothing.

Anyone who says it performs "25% better" with a lithium battery is experiencing bias effect, and nothing more.

And FYI - @Jedi2155 - the reason we got "disagree" votes here is because the actual DATA is proving out that folks have wasted their money on snake oil here.

 

[dmurphy]

gonna have to disagree with that statement. That it is a "digital amp" is almost irrelevant. You certainly don't want actual '1's and '0's going into your speakers -- will sound terrible. Anyways, yes it all will be analog in the end, even if the amp is class D and is using PWM.

Of course, the *output* is analog. But the analog signal is of course downstream of the MOSFET, having been re-generated. There's essentially a "break" between the input and output voltage. I still don't see where a lithium battery would add any value here since the MOSFET itself is really smoothing the power itself. No direct connection between the amp's input sine wave and output. I admit I'm not a daytime EE but have some knowledge ...

Now, on a traditional amp, 100% agreed - garbage in, garbage out.

Here's a good writeup of the internals on a Class D amplifier: http://www.irf.com/product-info/audio/classdtutorial.pdf

 

[neurocutie]

Let me explain how it's connected and you tell me.

Nice description.... not bussed though... (a buss/bus is a passive interconnect). They can't be bussed if the DC-DC converter is also going to charge the 12V battery -- there has to be switching (and regulating) elements in between, I presume the MOSFETS that you describe. There also has to be an appreciable voltage drop between the two to charge the 12V battery.

Anyways my main points were: 1) its irrelevant whether the audio amp is "digital" or not (its all analog in the end anyways), 2) the current capacity of the power source to the audio amp does matter, i.e. contribute to the quality of the sound output, 3) if the audio amp is being powered by the DC-DC converter system, which it sounds it is, then the type of 12V battery obviously doesn't matter.

 

[smatthew]

Nice description.... not bussed though... (a buss/bus is a passive interconnect). They can't be bussed if the DC-DC converter is also going to charge the 12V battery -- there has to be switching (and regulating) elements in between, I presume the MOSFETS that you describe. There also has to be an appreciable voltage drop between the two to charge the 12V battery.

Anyways my main points were: 1) its irrelevant whether the audio amp is "digital" or not (its all analog in the end anyways), 2) the current capacity of the power source to the audio amp does matter, i.e. contribute to the quality of the sound output, 3) if the audio amp is being powered by the DC-DC converter system, which it sounds it is, then the type of 12V battery obviously doesn't matter.

1) Everything is powered by the PCS. But the 12V battery serves to smooth out the power.
2) The PCS functions as a CV (Constant Voltage) power supply. It attempts to output a constant voltage, as long as the load is under 193 amps. The voltage is outputs varies from as low as 13.5 to as high as 14.5 depending on what part of the 12V battery charging regime the car is in. Don't worry - when someone says 12V in an automotive context they usually mean voltages from 10.5 to 15, but that range can vary.
3) The switching elements in the PCS are between the High Voltage battery, and the 12V output. That's how 300-400V is converted to 12-14.5V. The car does no modulation of that input at the VCFront. E-Fuses are strictly on-off.

 

[neurocutie]

Of course, the *output* is analog. But the analog signal is of course downstream of the MOSFET, having been re-generated. There's essentially a "break" between the input and output voltage. I still don't see where a lithium battery would add any value here since the MOSFET itself is really smoothing the power itself.

Not going to argue about AGM vs Lithium -- need more details to weigh in on that. The only point I wished to make is that the power source of the audio amp, whether Class A, AB, B or D can matter -- in fact it usually does. A Class D "digital" amp doesn't allow you to escape having a decent power supply. Consider the difference between a 16ohm load, 8, 4 and 1 ohm load (speaker) -- yes I have (fantastic) 1 ohm speakers. An audio amp is supposed to be have a particular VOLTAGE gain, regardless of load -- it is designed to be a voltage amplifier.

Consider an amp with a 28X gain. That means that, e.g. if you put in a 1V p-p audio signal, it may be expected to output a 28V output. And if it is rated at 100w into 8ohms, that would be 3.5A, 100watts = 28V * 3.5A (into 8ohms). Now instead of 8ohm speakers, connect 4ohm speakers, the same amp is now expected to deliver 7A while maintaining the 28V output, (and yes that means it is outputting 200w). Now connect up 1ohm speakers, the same setup is suppose to deliver 28A into the 1ohm loads to yield the 28V output, yielding 800watts. The point is that it really matters that not only is the amp up to delivering that kind of current, but the power supply (battery?) has to deliver high currents also. And it doesn't matter if the amp is "digital" or not. Those output MOSFETs still have to dump that kind of current into the loads while maintaining the specified voltage. The lower the frequency, the longer the MOSFETs have to keep dumping the current into the load. Amplifier class is about the conduction behavior of the output stage, the amplification required for proper output signals remain.

Whether some AGM is better than some lithium battery, it depends, but it certainly *can* matter. Many bad audio amps are bad because of their power supply. In this case, the audio amp being powered by the DC-DC converter, it shouldn't matter what the 12V battery is.