[EV- Technician]

@TechnicallyJeff

I have tried in the past sending them multiple emails about technical questions and I have received crickets in return from engineering Ohmmu department.

Since you have better contact with Ohmmu.
I would ask you to send them inquiry about LFP chemistry data sheet, BMS data sheet, set calibration values that BMS is watching ( cells voltages, when warmer is turning on)
How they manage cells imbalance if only discharge is allowed ( this is just not possible to run balancing and have battery getting discharged).
Did they run adequate tests to see how onboard ICCU is affected when is delivering high current to low DC side and Ohmmu BMS suddenly cuts of charging side of Ohmmu battery.
I have plenty of other questions, but let's see if you can obtain from them thus information.

If they don't incorporate on BMS side discharging getting turned off.
How they deal with scenarios where warmer is not capable to bring cells to the safe operating temperatures to accept any charging or how they deal in cold weather conditions where LFP chemistry can only take charging in mA, but onboard ICCU can deliver over 200A ( do they have ability on BMS to throttle current, I'm quite positive that they don't).

 

[wd1]

I have to add my 2 cents to this discussion. From a non-technical nerd type. I have had this Ohmmu battery in 2 cars now. I have updated the BMS to use the EV6 BMS profile and it seems to work flawlessly. I have bluetooth but no heater. I had one time where the battery shut down when the current got too low in my garage from a device drawing off the USB and OBD. That time the battery shut down both sides Charging / discharging and isolated itself from the car. I just had to restore the toggles in the App and charge the car with my level 2 charger to restore the battery from 25% to 100% charge. That is the only issue I have had with this battery for 2 1/2 years. The dealer has never said anything when I have had it in for service. Although, I guess when I do the ICCU recall I will swap in the original battery (which I trickle charge to 100% every 6 months).

So, so far I am a happy camper with this battery. All my electronics run great and since I just added Comma 3x I need the extra amperage and I like the 11 Lb. weight which makes it a breeze for at 71 yro guy to change.

 

[EV- Technician]

I have to add my 2 cents to this discussion. From a non-technical nerd type. I have had this Ohmmu battery in 2 cars now. I have updated the BMS to use the EV6 BMS profile and it seems to work flawlessly. I have bluetooth but no heater. I had one time where the battery shut down when the current got too low in my garage from a device drawing off the USB and OBD. That time the battery shut down both sides Charging / discharging and isolated itself from the car. I just had to restore the toggles in the App and charge the car with my level 2 charger to restore the battery from 25% to 100% charge. That is the only issue I have had with this battery for 2 1/2 years. The dealer has never said anything when I have had it in for service. Although, I guess when I do the ICCU recall I will swap in the original battery (which I trickle charge to 100% every 6 months).

So, so far I am a happy camper with this battery. All my electronics run great and since I just added Comma 3x I need the extra amperage and I like the 11 Lb. weight which makes it a breeze for at 71 yro guy to change.

For the price of one Ohmmu battery you can buy 3 lead-acid batteries and exceed any cycle life from Ohmmu battery that they advertise ( and this has to be laboratory conditions that are just not possible on EV or any ICE vehicle that incorporates dynamic voltage profile).

 

[wd1]

For the price of one Ohmmu battery you can buy 3 lead-acid batteries and exceed any cycle life from Ohmmu battery that they advertise ( and this has to be laboratory conditions that are just not possible on EV or any ICE vehicle that incorporates dynamic voltage profile).

Since I already have it I can't change my choice now. I'll just stick with it until I have a reason to need to replace it. I appreciate your input. Thanks.

 

[bjmsam]

I had one time where the battery shut down when the current got too low in my garage from a device drawing off the USB and OBD. That time the battery shut down both sides Charging / discharging and isolated itself from the car. I just had to restore the toggles in the App and charge the car with my level 2 charger to restore the battery from 25% to 100% charge.

Could that have been due to this?

LFP chemistry and number of cells they use are far above nominal voltage of AGM battery.
LFP chemistry cells voltage at 3.540V at 95%SOC will be at resting voltage 14.160V vs AGM battery resting voltage 12.7.

When the Ohmmu battery reaches a voltage of 12.6V, it has less than 16% State of Charge (SOC) remaining. At this low SOC level, the onboard DC-DC converter will not initiate charging until the battery voltage drops further.

Could it have happened while driving?

Ohmmu BMS has settings to turn off charging or discharging, irrelevant to the vehicle being in motion .
In this scenarios there are possibilities of onboard ICCU to go to limp mode if Ohmmu switch off under heavy load on low DC side. This alone is extremely dangerous that can cause loss vehicle control and possibly accident on the road.

 

[wd1]

Could that have been due to this?


Could it have happened while driving?

Never has. Never heard it happening to anyone.

 

[BoogieWoogieWoogie]

I don't understand what people aren't getting. Ohmmu has a BMS that is attempting to trick our car into thinking that it's a lead acid battery. You are putting ALL your faith that a battery with a BMS designed by one or two people in a garage in the middle of nowhere in Arizona (look up their address - it's really in the middle of nowhere) are as smart and have the same resources as HMG. Even Tesla when they switched their low voltage battery three years ago changed their entire electrical architecture to accommodate this change. With Ohmmu, you are relying on their BMS to mimic EXACTLY the characteristics of a lead acid battery to the way a lead acid battery interacts with our car and how the EV6 was designed. It's insanity if you think that is a great idea. Ohmmu is banking on the "oooh, shiny, latest thing!" mentality so prevalent in our society.

 

[bjmsam]

I don't understand what people aren't getting.

I believe people "get" the point you continue making (other than the "middle of nowhere" bit, which historically has not been a barrier to innovation in the U.S. of A.) but remain interested in exploring specifics that could influence development, optimization, and certification of Lithium FerroPhosphate (LFP) or other "modern" alternatives to "100+ year old technology" Flooded Lead Acid (FLA) and Absorbent Glass Mat (AGM) batteries for our "21st century high tech car." Meanwhile, this sounds sensible and prudent:

I guess when I do the ICCU recall I will swap in the original battery

 

[BoogieWoogieWoogie]

I believe people "get" the point you continue making (other than the "middle of nowhere" bit, which historically has not been a barrier to innovation in the U.S. of A.) but remain interested in exploring specifics that could influence development, optimization, and certification of Lithium FerroPhosphate (LFP) or other "modern" alternatives to "100+ year old technology" Flooded Lead Acid (FLA) and Absorbent Glass Mat (AGM) batteries for our "21st century high tech car." Meanwhile, this sounds sensible and prudent:

I swear people don't read what I wrote. Again: Tesla reworked their entire electrical architecture to accommodate their new lithium "12v" battery. Ohmmu slaps on a BMS and calls it a day. As the EV engineer posted multiple times, there is a disconnect between the draw and voltage reading regardless of the BMS on the Ohmmu. I feel like the only people defending Ohmmu are the ones who fell for their poorly constructed battery and are running it in their cars. And yes, you can VOID your warranty by running an Ohmmu battery if it's determined that running a janky lithium battery like Ohmmu caused the electrical failure of a component.

 

[wd1]

Again. Thanks for sharing. But, we are here to share not force our opinion on anyone else. I have been driving and working on cars for 50 years and totally understand your point. But it’s my decision and it works for me. And I do read every word of your reply’s. In fact I’ll let you know the first time OHMMU leaves me stranded!

 

[BoogieWoogieWoogie]

Again. Thanks for sharing. But, we are here to share not force our opinion on anyone else. I have been driving and working on cars for 50 years and totally understand your point. But it’s my decision and it works for me. And I do read every word of your reply’s. In fact I’ll let you know the first time OHMMU leaves me stranded!

Fair enough. Just remember
market cap dictates research money allocated. Market cap of the following companies:
Tesla: 550 billion
Hyundai: 60 billion
Kia: 50 billion
Ohmmu: "Market cap? Huh? Jethro, I got me an Arizona Diamondback baseball cap...is that what you mean?"

That's all I have to say about this subject.

 

[TechnicallyJeff]

Lots of comments to go through. I'll see what additional info I can get from Ohmmu (and go through what I already received over a year ago) and share anything new.

Also, I've seen a few people comment that Tesla reworked their electrical system to accommodate their change to lithium batteries. That was because they switched to 16v batteries. That's different (significantly higher) than what we're discussing here and not related, other than general benefits associated with lithium batteries.

 

[bjmsam]

I'll see what additional info I can get from Ohmmu (and go through what I already received over a year ago) and share anything new.

Excellent - thank you!

Also, I've seen a few people comment that Tesla reworked their electrical system to accommodate their change to lithium batteries. That was because they switched to 16v batteries. That's different (significantly higher) than what we're discussing here and not related, other than general benefits associated with lithium batteries.

The aforementioned video summarizes the significant changes Tesla made to shift responsibility from the new 12V Li-ion battery (with only 6.9Ah and 99Wh) to the high voltage battery (which is engaged any time the vehicle is not asleep).

 

[TechnicallyJeff]

Excellent - thank you!

The aforementioned video summarizes the significant changes Tesla made to shift responsibility from the new 12V Li-ion battery (with only 6.9Ah and 99Wh) to the high voltage battery (which is engaged any time the vehicle is not asleep).

Yeah it's very interesting the changes they made there.

 

[TechnicallyJeff]

FWIW I'm watching that video again (it's been a while). I want to reiterate, that design is definitely not current lol. And he said no thermal monitoring - again not current. They've had thermal monitoring for a while. Anyone with an Ohmmu battery in the last 1-2 years can easily see this as you can see it's temperature in the app. And anyone within the last 6 months has self-heating built-in.

And again, he's saying it has switches which disconnect it from the bus. It's disabling charge so the voltage doesn't get too high, but it's not disconnecting it from the system. I'm not sure if he got weird readings from the older BMS indicating something like that or what, but that's not how it works, at least according to Ohmmu. And again they changed their BMS in the last few years since that battery was made.

 

[Wes]

One detail I just digested from that video is that Tesla's low voltage battery is Li-ion NMC chemistry. That IS NOT the same as LiFePO4. So when everyone says "well Tesla switched to Lithium" that's not the same chemistry as the LiFePO4 (lithium iron phosphate). So the whole logic of Lithium iron phosphate already being adopted by some automakers seems to be a bit stretched and flawed due to the confusion between Li-ion and LiFePO4. I'm neutral on this subject but that's one important detail I just noticed... am I right about what I'm interpreting?

 

[TechnicallyJeff]

One detail I just digested from that video is that Tesla's low voltage battery is Li-ion NMC chemistry. That IS NOT the same as LiFePO4. So when everyone says "well Tesla switched to Lithium" that's not the same chemistry as the LiFePO4 (lithium iron phosphate). So the whole logic of Lithium iron phosphate already being adopted by some automakers seems to be a bit stretched and flawed due to the confusion between Li-ion and LiFePO4. I'm neutral on this subject but that's one important detail I just noticed... am I right about what I'm interpreting?

Yes that's a significant component that I was referring to. Nominal voltage for Lithium NMC is 14.8v vs 12.8v for LiFePO4. Hence why I was saying you can't argue Tesla had to rework their electrical system to accommodate their change so why does Ohmmu think it just needs a BMS. Going from 12v to 12.8v on a 12v system that easily sees 14v+, even in ICE vehicles with normal lead acid batteries, isn't nearly as significant as going from 12v to nearly 15v nominal with the system easily seeing 15.5v-16v.

 

[EV- Technician]

Yeah it's very interesting the changes they made there.

And one very important thing that Tesla did when rework the onboard DC-DC converter and use of LFP chemistry is using LIN bus to make Tesla LFP battery BMS as slave to the onboard DC-DC converter ( this is very important for this chemistry).
Also it took extra redesigned to deal with electric noise ( when Tesla LFP chemistry disconnect completely from low DC side).
As much this type of approach is little better, it is not without sacrifices, like more frequent switching of HV DC main contactors and more losses on conversion each time it needs to charge small Ah LFP battery.
It also needs to pick up entirely on low DC current demand for stationary and in motion current draw.
What Tesla did is made more cutting measures by introducing Tesla 16V chemistry to save on cost producing vehicles.
On opposite side owners are hit with more energy being used with this approach and higher energy use whenever onboard DC-DC converter has to preform stationary 16V battery maintenance or constantly keeping eye on current demand when vehicle is in motion ( because small Ah 16V battery alone is not able to deal with it).

 

[EV- Technician]

I can provide further details on the recent Tesla modifications and the challenges faced by Tesla owners due to these changes. (I must admit, I am not particularly impressed.)

If you are interested, we can discuss this further in a separate thread.

 

[EV- Technician]

I would like to clarify that my intention is not to pass judgment or cause any distress. Rather, I am here to share my expertise in professional discourse and present factual information that is often concealed by certain aftermarket solutions. It is important to address misconceptions, such as the notion that a partially developed design like Ohmmu can serve as a complete replacement for a lead-acid 12V battery.

Therefore, before becoming agitated or expressing uninformed opinions on the subject of discussion, I encourage you to be more transparent and ask questions about topics you may not be familiar with.

I have been the subject of criticism in my private chat by some members who have accused me of being stubborn or unwilling to accept their way of misleading information they have been filled in.