Longer term Ohmmu experiences?

[Flybyglass]

It's down at the bottom under the advanced tab where you see load and send configuration.

OK that must be the Android version. Nothing in the IOS version.

 

[Silver Ghost]

In Texas at least, both regular lead acid and Li ion battery’s last about 2 years before needing replacement.
so back to regular lead acid for me. I am assuming our hi temperatures may have something to do with this but not sure. Ohmmu has terrible customer service so that also contributed to my decision to go back to lead acid.

 

[dfwatt]

In Texas at least, both regular lead acid and Li ion battery’s last about 2 years before needing replacement.
so back to regular lead acid for me. I am assuming our hi temperatures may have something to do with this but not sure. Ohmmu has terrible customer service so that also contributed to my decision to go back to lead acid.

If lithium iron phosphate which has a deep cycle count significantly exceeding lithium ternary batteries is only lasting 2 years something is seriously wrong with either the battery management system or there is a mismatch between Battery Management systems and 12 volt sub system in the car. It's actually cold weather that's the bigger problem for lithium iron phosphate chemistries in these cars. You probably don't have that problem too much of the year but anytime it gets below 45°, this increases the chances of the car seeing the battery as deficient and then suiciding it. In any case no argument on ohmmu's problematic customer service.

 

[mstatkus]

Friend just had his Lead Acid fail in FL but he’s in a lease at the 2 year mark.
I’ll probably run mine a bit longer but by Oct 25th or so it tends to frost here and I don’t think I’ll be able to keep it in.

Yoke gets in today so I’ll be disconnecting the battery - I’m getting so good at it

 

[Flybyglass]

It's now 2 weeks with the V4+ and no issues. Behaviors noticed are upon a normal wakeup, the car will draw a few amps from the battery then recharge to full. Ince very few days the car appears to do a test of battery integrity. It will charge to 100%. Then start applying an amp draw (could be as high as 25 amps) but eventually slows the draw down when the voltage is about 13.04v. In once case it dropped to 12.9v and I was ready to remove but then it reversed and charged back to 100%. The Ohmmu discharge behavior was like the graph on their website. Voltage dropped to around 13.2 to 13.04 and just stayed there while discharging for what seems like a couple hours. In every case the car reverses then charges back to 100%. Sometimes the car will charge to 100%, then discharge to bring it to 99-98% (about 13.8v buy could be as low as 13.4) and stop discharging for the sleep cycle. No warnings in Notifications and no messages in service mode. If this continues I intend to install the newer V4+ with heating element for New England winters. BTW I notice several lithium battery manufacturers now adding internal heating in lower temps. Also had one software update from 2023.7.20 to 2023.7.30 with no issues.

 

[gearchruncher]

If lithium iron phosphate which has a deep cycle count significantly exceeding lithium ternary batteries is only lasting 2 years something is seriously wrong with either the battery management system or there is a mismatch between Battery Management systems and 12 volt sub system in the car.

Dfwatt has me blocked because he doesn't know how a Tesla motor and inverter works, but here I go:

Assume the hotel load on the car is 20W. This is reasonable as with a 400W lead acid the car wakes up every 12 hours or so to charge.

20W * 24 hours * 365 days * 2 years is 350kWh.

Lithium batteries in constant use care about total power through the battery, not years. This is often expressed as cycles, and 1000 cycles is standard to get to about 50% capacity. For a Tesla, this would be 300K miles for the main battery (1 cycle being 300 miles). It doesn't really matter if you do this 50 miles at a time or 300.

So, how many cycles is this on the Ohmmu? Well, they refuse to tell you the electrical capacity of the battery (always a good sign). But it's 9lbs/4Kg. LiFEPo4 tends to be ~100 wh/Kg, so it's 400Wh (same as stock lead acid).

Ok, so we need 350kW of total energy flow, and we have a 400Wh battery. That's 875 equivalent cycles.

Suspiciously close to 1000.

Weirdly, lots of people can get 4 years out of a lead acid, so it appears to be able to go 1,000+ cycles also, despite supposedly being a much worse chemistry.

 

[mstatkus]

Cycle count for my year old is at 8 via the app. It went thru 3 load sheds before the firmware patch. Used now roughly 3 months and self drained by me 2 times to sub 60-80% for storage. If I extrapolate that out I’m not getting a super high cycle count per year. But to your point some of it is hidden from us. Original battery was like 40Ah. And they dropped capacity with this one to solve the monitoring issues.

I’m using my original battery which is weekly charged full by the sun, and depleted to 56% to charge a TOPENS gate opener 1000ft from my house. I have no way of tracking a cycle on that battery.
Life (in cycles) = (Capacity x 100) / (Discharge rate x Depth of discharge) I’d have to get a bit of monitoring hardware to sort that.

 

[gearchruncher]

Cycle count for my year old is at 8 via the app

This should immediately make you suspicious.

3,200wh over a year. 8,800 hours in a year.

That's 0.36w on average. That's less than a modern smart phone draws while the screen is off.

It's only 30ma at 12v. Yet if you put a current clamp on the wire to the battery you will see loads at least 10x that when the car is fully asleep and way more when it's awake.

It's an impossible number and should immediately make you call Ohmmu and ask them how it's calculated and why it's so wrong.

How do people determine/measure power usage while awake topping of 12V battery?

Several months ago I measured the 12V DC power usage while the car was sleeping with an ammeter connected in line and found the power usage to be about 7 to 8 watts. This measurement could have also been performed using a shunt. Many sources say the power usage while the car is awake (normally...

teslamotorsclub.com

 

[mstatkus]

This should immediately make you suspicious.

3,200wh over a year. 8,800 hours in a year.

That's 0.36w on average. That's less than a modern smart phone draws while the screen is off.

It's only 30ma at 12v. Yet if you put a current clamp on the wire to the battery you will see loads at least 10x that when the car is fully asleep and way more when it's awake.

It's an impossible number and should immediately make you call Ohmmu and ask them how it's calculated and why it's so wrong.

How do people determine/measure power usage while awake topping of 12V battery?

Several months ago I measured the 12V DC power usage while the car was sleeping with an ammeter connected in line and found the power usage to be about 7 to 8 watts. This measurement could have also been performed using a shunt. Many sources say the power usage while the car is awake (normally...

teslamotorsclub.com

Mine was on a shelf at 60% from late Oct -May or so when we got the firmware update ability. So it didn’t see any action for ~7 of the 12 mo.
I do not have the heater element.
From what I understand the 2023 15V is around 9Ah. I suspect ours is around 30Ah. Also based on it having about 1-1.5hrs of capacity during a 30A load shed.
I have not seen any exhibited behaviors of it needing to supply more than that yet. But I’ll keep an eye on it.
I will keep an eye on the cycle count. That’s not to say the math isn’t wrong. It’s a BMS and I’ve yet to trust one completely yet.

Someone needs to put the string/parallel chemistry of the cells /pouch on the battery as a way to make all this easier in the long term.

 

[gearchruncher]

Someone needs to put the string/parallel chemistry of the cells /pouch on the battery as a way to make all this easier in the long term.

There are plenty of videos of Ohmmu's disassembled out there.

But none of this is unknown. These are LiFEPo4 batteries- they are advertised as that, so there's your chemistry. These are used because LiFe has a nominal voltage of 3.2V, with a peak of 3.65 and empty at 2.5V. So a string of 4 is 10V discharged and fully charged at 14.6V. This lines up very well with "12V" lead acid batteries, making them a virtual drop in for many applications that use simple fixed voltage chargers like an alternator.

All the videos show this. It's just 4 pouch cells in series. Like all the "Lithium" 12V batteries you can buy for powersports and all sorts of other stuff to replace the stock lead acid. There is nothing special here except some firmware that attempts to work around Tesla's Lead Acid health monitoring logic.

Watch this if you want to be informed as to what is inside there:

Ohmmu literally refused to tell Ingineerix the capacity of the battery, so he tested it himself, and got about 40Ah, but the BMS allowed the battery to be overcharged. Like has been discussed in this thread before, probably to increase compatibility with the Tesla PCS, which wants to go to 14.8V sometimes, which is above the max LiFe voltage.

 

[Dysan911]

So after watching that video. I'm wondering if my V4+ is stressing out my PCS as he mentioned. Kind of a scary thought.

FWIW. My current V4+ has been pretty good. I did experience those Black screen situations 4 or so months back. Maybe longer and thought it was related to the V4+ but a few Tesla software updates came through and the issue went away.

My V4+ has 96 cycles and is over a year old. Is anyone else dumping their battery and going back to LA for fear of harming the PCS?

Also I did NOT update or change my Firmware. It's still on the same as the day I got it.

 

[brkaus]

And in the time of this thread, I finally had to replace my lead acid battery in my 2018 m3. It gave me a warning and Tesla was out to change it for $125. Could have done myself, but would have taken time to pickup the battery so I consider the extra $40 a delivery fee.

And if I have to replace it in another 4 years I’ll still be ahead.

 

[Flybyglass]

So after watching that video. I'm wondering if my V4+ is stressing out my PCS as he mentioned. Kind of a scary thought.

FWIW. My current V4+ has been pretty good. I did experience those Black screen situations 4 or so months back. Maybe longer and thought it was related to the V4+ but a few Tesla software updates came through and the issue went away.

My V4+ has 96 cycles and is over a year old. Is anyone else dumping their battery and going back to LA for fear of harming the PCS?

View attachment 971983View attachment 971984

Also I did NOT update or change my Firmware. It's still on the same as the day I got it.

I have the V4+ back in for the last 3 weeks. What I see is after a normal start the PCS will charge the V4+ back to just over 14V like you have, then apply a few amps draw to bring it down into the 13.8 range. Sometimes more or less. Observing the PCS in Service Mode while the battery is drawing down the PCS output is reduced still showing green like intentional. I see it as giving the PCS a rest. I also note about once a week what I call a "Battery Integrity check." This can be misinterpreted as "suicide mode". It will draw 25 amps (meaning the PCS is only putting out maybe 5 amps still showing green) and as the voltage approaches 13.3 it slows. Around 13.04 the draw is maybe 5 amps and it will sit there for a couple hours. Once reaching 12.99 amps the draw is lowered to about 1 amp. Once at about 12.9 it stops drawing (battery showing 19-20%. Then sits a bit then charges back up to 100%, takes a little off say 97% and stops. Never a warning in Notifications or Service mode. Not sure if Tesla updates the software to accept Lithiums or if Ohmmu improved the BMS software. While using IOS there is no version numbering for the software but if an update is done it always pulls the most recent from the server. For me this whole battery check process took about 5 hours. I keep waiting for a warning message but nothing. I keep a couple 12 volt batteries on the shelf in case and when reading 19% I was ready to extract but didn't need to.

 

[mstatkus]

I’ve not seen it do much in the way of amp draw driving. Very small fractional pulses of < 1A discharges.
I’ve seen it take over when charging with a larger 8-10A draw but it cycles back and forth.
Lowest I’ve ever seen the app state is 32%, then charges back up.

I did see my screen go black after backing out of my garage, parking and as I got out it went black, then came back on.
Yanked the Ohmmu, put in the lead acid. Few days later same thing happened on it so I wrote that off.

The comments on 100A draw from accessories like power steering etc in the video; I’ve seen no evidence of this directly. That load would seem excessive for the tiny battery they put in these cars. These aren’t made to do much more than 360-480w. Any thing bigger and you’ll be down to minutes of battery life.

 

[gearchruncher]

These aren’t made to do much more than 360-480w. Any thing bigger and you’ll be down to minutes of battery life.

You're claiming that a 40ah,12v battery can't handle more than a 40A load? And that a 40A load on a 40ah battery would only last a few minutes?

How does a 40ah normal car battery do 600cca (7000w)?

The whole point of the video was very short bursts of 100A. Not running power steering by itself. And not that power steering can draw that for more than a moment either.

 

[mstatkus]

You're claiming that a 40ah,12v battery can't handle more than a 40A load? And that a 40A load on a 40ah battery would only last a few minutes?

How does a 40ah normal car battery do 600cca (7000w)?

The whole point of the video was very short bursts of 100A. Not running power steering by itself. And not that power steering can draw that for more than a moment either.

12V X 30A = 360w
There isn’t enough Amp hours in these batteries to support a large load for any sustained period of time.
Even during the 30A load shed the estimated run time was 1hr roughly before it was at a state the BMS would shut off and protect the cells.
Want to run 1000w, just prepare for it to drain the battery in 15 mins or so.

 

[gearchruncher]

12V X 30A = 360w
There isn’t enough Amp hours in these batteries to support a large load for any sustained period of time.

You literally said "a few minutes" when the stock battery can sustain 360W for 80 minutes. That's not what most people would call a "few."

But I'm not sure what your point is or if you watched the video. Ingineerix is saying that the issue with the Ohmmu is that it GOES AWAY sometimes because the BMS shuts it off. As in literally the same as you removing it from the car. Now the PCS is required to source all 12V loads in the car, even millisecond peak loads. It's not designed for this except in emergencies. It's designed for average loads, since the system is designed with a 12V battery of large capacity to be on the bus to take up any momentary loads.

There is zero discussion about the 12V trying to run the car for 1 minute by itself, much less 80 minutes. But you do realize that even a 100A load on a 45AH battery would still last 25 minutes, which is a LOT longer than a "few" minutes?

Nobody is saying the 12V battery supports all the 12V loads either. That's the PCS's job on average. The PCS is 1,500W. So yeah, you'll never see 100A from the 12V battery on any time frame that a simple ammeter can measure. But like Ingineerx showed with an oscilloscope, they are there at much shorter time periods. You do realize there is a PCS and the car doesn't "run" off the 12V battery while you are driving, right? In fact on average the PCS is charging the battery when the car is on, just like an alternator does in an ICE car?

FYI, The 85B24LS in the Model 3 is rated at 45AH, 650CCA. This means for the duration of a CCA test, it can maintain 650A. That's 650A for 30 seconds at 0 degrees F. So cold that even charging a lithium will destroy it. Yet you claim the battery can only do 1/15th that power for a few minutes. You claim the battery "isn't designed for more than 480W" yet the manufacturer specifically specs it for 6,500W.

 

[mstatkus]

This one w/ bluetooth is sub 40Ah. I’d put it in the neighborhood of ~30Ah (this is a ballpark) or so but again it’s based on witnessed load shed and estimated runtime at 30A. Its physically lighter than the original w/o bluetooth.

I don’t know where a ‘few minutes’ comes from if I said it .. I think I said ‘15 min’. It’s just math I’m not doing anything other than ball-parking outcomes if you throw a much heavier load on a small capacity battery. The reference I heard was they implied things like power steering were drawing 100A. Then proceeded to trash the batteries design. I’ve taken apart power stations, these things all look like this on the inside so none of that was a shock.

The new one has been running decent. There was a firmware update from Ohmmu v4+.

Sean let me keep mine, it charges a 518Wh power station once a week. its been in service for 29 weeks now. More than enough capacity to charge 60w for 4hrs.

 

[gearchruncher]

I don’t know where a ‘few minutes’ comes from if I said it .. I think I said ‘15 min’.

It's two posts up:

The comments on 100A draw from accessories like power steering etc in the video; I’ve seen no evidence of this directly. That load would seem excessive for the tiny battery they put in these cars. These aren’t made to do much more than 360-480w. Any thing bigger and you’ll be down to minutes of battery life.

Yeah, I guess you didn't say "few." I still think most people would interpret that as under 10 minutes. How many people say "you only have minutes left" when they mean 59 minutes? Or even 15?

And why are you talking about the Ohmmu battery capacity suddenly? You specifically said you were discussing the capability of the "tiny battery they put in these cars". Despite the fact that it's larger than the Ohmmu, and the same size as a lot of ICE cars. It's 45AH and 650CCA. There's not a lot that is tiny about that, and it for sure isn't limited to 480W.

Then proceeded to trash the batteries design. I’ve taken apart power stations, these things all look like this on the inside so none of that was a shock.

The "trash" was that the whole design was inappropriate FOR A TESLA. A Tesla is not a power station. It is not OK if the BMS takes the battery offline because it decides the voltage is too high, or the battery is too cold, or the voltage is too low. The lead acid never does this. The system was not designed with a LiFe with a BMS. It's flat out incompatible.

The trash is because Ohmmu sells this as specifically for Teslas, and superior to the stock battery. When it's actually completely incompatible with the car's designed electrical system, the interior construction is also a bit questionable for the known very harsh environment for an automotive application, and the lack of temperature sensing is unforgivable for the automotive environment. As you say, its a battery designed to sit on a shelf in a thermally controlled environment as a UPS, not as a car battery.

but again it’s based on witnessed load shed and estimated runtime at 30A.

Can you please explain this "witnessed load shed?" You're saying you've seen the PCS in your car go out, and then seen the Tesla start shedding 12V loads and somehow in that process you ended up with a capacity estimation? And that this was 30A? And that this left 15 minutes of time? But you estimated 30AH, despite 15 minutes at 30A being 7.5AH?

Sean let me keep mine, it charges a 518Wh power station once a week. its been in service for 29 weeks now. More than enough capacity to charge 60w for 4hrs.

None of these numbers make sense or have any relevance to the Tesla. You have a 518Wh power station, that is somehow recharged with 240Wh of power, which is plenty, so the battery must be great for how a Tesla uses it?

 

[mstatkus]

I've got 75 - 100Ah batteries; I choose to use the word "small" also in respect to its physical size. It's a shade larger than one I have in my lawn mower.
Edit: Load shed comment - Pre-firmware patch due to cars LA monitoring and putting a load shed on the LV battery. This was the original issue post a Tesla Software patch.

Is this all solved? I doubt it. Firmware patches leave some room for adjustment. Can the BMS cope? Sounds like you're a no. I'm a leaning no as I just don't see a path past the internal monitoring to your point a Lead Acid != LifePo4. And you'll be in a never ending battle with software patches.

Even simple things like animated lights if you opt to buy them can be completely wiped out by a software update that changes the blinker intervals.
And a software update can render so many other things like a auto-frunk less useful - like not letting you hit "open" in the app anymore to close the frunk.

It's going to be fun times deviating with anything in a Tesla

Its all right in front of me: