Ohmmu LiFePO4 12v Batteries Now in Stock - Limited Time Offer: Free Shipping

[electruck4x4]

OK. That's great news!

That would be a good explanation on why the guy in the video didn't find a temperature sensor on the BMS - it didn't need one on the BMS, because it has a active warming system with it's own sensors.

Hold on - but only when charging. So if it is frozen, you must still initiate a "charge" for the heaters to kick in. But until the heater heats the cells, the cells are still frozen.

Question: Does the charging circuit wait for the cells to be heated sufficiently to accept a charge?

Thanks for looking into that last question. I'm sure OHMMU is getting a workout from this thread!

Hmmm... I'm actually not too sure regarding this last one. I'd imagine they heat as a preface to charging. They should be able to provide an answer for you though via email ([email protected]). Shoot them a note. Queenie and Jason over there are great!

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[NY_Rob]

With Liion/LiFePo4 BMS's, in general, shutting down or allowing connections for charging and discharging in an ON/OFF manner - as opposed to a lead-acid battery doing so as resistance dictates over a period of time - my other question is how the host (aka Rivian or Tesla) will handle this.

LiFePo4 batteries will charge up if the input voltage is higher than 12.8 (their nominal voltage) and up to 14.4 (some up to 14.6) volts. Any higher than that, any decent BMS would shut down charging due to "high voltage". So, does the Rivian ever try to charge it's 12v system over 14.6 volts? You tell me. And what will the Rivian do if it feels the battery needs a charge, but the battery shuts the charge down because of over-voltage? You tell me.

100% valid concern regarding the BMS high voltage cutoff!

From what we have seen, Rivian never seems to charge their 12V batts up to 14.6V levels, but that is not well documented or even established. I'd hate to be the one to be experimenting on a BMS with a 14.4V charge cutoff and a vehicle programmed to charge up to 14.6V!

On our boat and Jetski (3 batts total) I have replaced the heavy old 12V lead acid batts with homemade LifePo4 cells made into batteries. This will be my 3rd summer running with the LifePo4 batts. I have programmed the battery BMS high voltage cutoff to match the charging system of the outboard and Jetski which both stop charging at 14.6V. I have also installed a safety device on all three battery circuits which will insert a small resistance from B+ to Ground if it see's any voltage spikes over 16.5V therefore allowing a small current to still flow from the charge device (alternator or stator windings in the case of the outboard and Jetski) saving the charging system from seeing a suddenly open circuit or infinite resistance.

2V - 24V Alternator Surge Protector AP12D [Sterling Power USA]:
https://www.sterling-power-usa.com/SterlingPower12voltalternatorprotectiondevice.aspx

Something like the above unit might work with the Rivian to prevent the voltage from spiking when the battery BMS decides "no more charge"?

 

[CommodoreAmiga]

Something to consider is Rivian seems to be actively tweaking their 12V charging logic with OTA updates. For this reason, I would personally not want to replace the 12V batteries with different chemistry or capacity, at this time. We cannot predict how that will interact or be affected by future OTA updates. You may try to solve a problem, today, that then causes further problems when Rivian addresses the problem in a manner that works for their OE batteries but is incompatible with your aftermarket choice.

 

[Dark-Fx]

This will be my 3rd summer

If you're only using them in the summer time I wouldn't be worried about it either way. LFP batteries really only have critical problems with being actively charged when below freezing. 14.6V is the practical limit but you won't see damage until a little higher. Most lead acid systems don't go over 15V. It's trivial for the BMS to disconnect the cells above whatever limit there is anyway.

I still wouldn't change the 12V out on my Rivian for something untested though. LFP's depth of discharge is wildly different than lead acid is.

 

[Visket]

They should be able to provide an answer for you though via email ([email protected]). Shoot them a note. Queenie and Jason over there are great!

I emailed OHMMU yesterday (6/14) AM. Nudged them today. No reply so far....
********************

Hi Jason / Queenie -

I'd like to update the Rivian Forums thread with some good "cold weather" news.

If you could find some time to reply to my questions, below, I would appreciate it.

Thanks -

Mike

On Jun 14, 2023, at 7:32 AM, XXX wrote:
Greetings -

You might have heard of the discussion on one of the Rivian forums regarding replacing the 12V lead-acid batteries with your OHMMU LiFePo4 (LFP) units:

https://www.rivianforums.com/forum/...stock-limited-time-offer-free-shipping.15947/

ElecTruck4x4 has your LFP batteries for sale to use on Rivians, and have stated that they have several customers that are happy with the conversion.

However, as part of the thread on the topic, a link to a Tesla forum shows a video that is less than favorable to your LFP battery.

I have converted several lead-acid applications to LFP, but not without having to perform upgrades on ancillary components of the system to which they are part of. I therefore have some questions, the latest of which ElecTruck4x4 referred me to you.

To cite a part of that forum thread, ElecTruck4x4 has stated: "There are actually silicon warming pads between the cells which kick in at a set low temp point, but only when charging is active."

So, sticking with the "frozen cells" issue, my questions:

1) Is it true that there are active heaters in the battery?
2) Does the charging circuit wait for the cells to be heated sufficiently before attempting to charge?
3) Can you please send me the data sheet (specs) with all of the normally available data on LFP batteries (max charging, max/constant discharge, etc...)?

With my experience in LA --> LFP conversions, I will personally be waiting for Rivian to respond to me that they certify the charging system is LFP compatible before I take the plunge.

But until then, I don't think it is fair to judge your Rivian sales based on a Tesla video, and will set the record straight - at least where frozen cells are concerned.

Thanks -

*******************

 

[k3g]

Worth also mentioning that the low voltage maintenance system in the Rivian is built with a specific battery's discharge curve in mind. If this replacement battery doesn't match that, there's little chance of the system functioning as engineered.

I wouldn't modify that part of my truck, personally.

 

[Visket]

Forum -

A response from OHMMU. A long read, but if you've come this far in this thread, worth it. I'm not saying I agree or disagree with this, just forwarding to the group for clarity/transparency.

Note that this initial "Hi Sean" is my response to this email from Sean.

************************************************

Hi Sean -

I'll share that in the forum topic.

In the meanwhile, a "spec sheet" will do wonders to understand the "ranges" (max volt, amps, temperature, Watt Hrs, "C" charge/discharge rates, etc...) of the batteries.

Thanks for the explanations - much good info in there.


*************************************************

Hi Mike, I thought we texted together about this? But now I don't see your number so I must be thinking of a different person on this subject.

There are no issues with our batteries for the R1 with relation to how the vehicle charges the battery or cold temperature conditions the vehicle may be subjected to.

One of the easiest ways to confuse people is to make claims on subjects about which most folks know "something" about but not really how it works or the full-picture, one of these seems to be charging batteries. I've seen it hundreds of times where in online forums there are claims made about charging batteries that don't jive with reality. It's easy to say "it's a special algorithm to charge that one vs this one" but that doesn't really say anything. In charging a battery and in discharging a battery there is a chemical reaction occurring inside of the cell, voltage is a measurement of electrical potential energy and what that means is that electricity (electrons) will flow from a higher voltage source to a lower voltage if properly connected to one another through a conductive medium. The process of charging a battery cell is simply providing a higher-voltage source (the charger) to the cell, there is no magical or unique difference about it, there isn't some other factor or variable, it is pure and simple, voltage, that's it. So this means you connect the battery cell to a charger and current (electrons) start to flow, the rate of the flow is dictated by Ohm's Law (V=IR). Chargers monitor the current and adjust the voltage output to reach a particular amperage/current limit.

OK, so now with all that background, charging any battery is a function of "the charging curve" which for the most part is very boring and they are all the same, the only real changes happen at the end points (empty and full). A particular battery chemistry will become fully saturated (de-ionized, reduced, "charged") at a particular voltage and consequently will become (nearly) fully unsaturated (ionized, "depleted") at another voltage. The charged and empty voltages are what makes each chemistry "special" or different not the process of pushing or pulling current from the cell. So the real question when it comes to "is the charging compatible" are:

Does the Max voltage output of the charger (system) fall within the Max voltage range of the battery cell?
Does the Min voltage that the system allows the battery cell to reach before initiating recharge fall within the usable voltage range of the battery cell?
Do the Maximum currents/amperages of charge and discharge fall within the battery cell and BMS capability?

Those questions produce a real understanding of whether a battery can be compatible in a system. The "algorithm" is actually as generic as the above information, what are the max/min voltage set-points of the charger and what are is the max/charging current, there is nothing else special going on.

OK, this is a long email and explanation, I hope that is helpful, this subject is one that I find way too much misinformation online.

Alright to answer the rest of your questions;
Yes there are silicon warming pads in the R1 batteries from Ohmmu and yes they come on during charging to warm the battery above a set-limit. That limit is something we can change through OTA updates as we find necessary but it is designated presently to do the job properly in the conditions of the vehicle in any region of the globe where the R1 are sold/operated (automotive-grade, in other words)
The charging circuit is totally outside of the control of the 12V battery, it has no authority in the vehicle to command the DC/DC output (the charger); what it does is as soon as charging current starts to flow, if the temperature is below a set-point, it warms them up, the warming up process happens very quickly as the heat elements are attached between each cell. There are monuments of misinformation online about cold charging LFP batteries, mostly it is a total misapplication of the danger of charging Lithium-Ion (NMC, LMNO, etc) when cold-soaked (can lead to dendrite/crystals, which ruin cells and make unstable) but it is not the case for our battery cells at all. We don't warm them because it is a requirement to safely charge the battery, but it does lead to longer lifespan.

The video that folks are looking at is of a tear down from an old Model 3/Y battery (relatively old, the vehicles have only been around for 5 years), this battery design was scrapped by us years ago and is not how our batteries are currently built. The cells are different, the BMS is different and the assembly process is different. This is true across all of our batteries (the newest 3/Y are nothing like that old one), but especially so of any of the newer models (H3, H5, R1, etc) that we have only been making for the last year or so. The perspective of that video is a bit misguided as it was a faulty battery design from the get-go and not a representation of what we actually build today.

-Sean

 

[Team Venom Racing]

Discount on these batteries can be had using code RIVIANTECH

So far my Ohmmu batteries have been great!
full story on Rivian Tech’s FB page.

 

[Donald Stanfield]

Forum -

A response from OHMMU. A long read, but if you've come this far in this thread, worth it. I'm not saying I agree or disagree with this, just forwarding to the group for clarity/transparency.

Note that this initial "Hi Sean" is my response to this email from Sean.

************************************************

Hi Sean -

I'll share that in the forum topic.

In the meanwhile, a "spec sheet" will do wonders to understand the "ranges" (max volt, amps, temperature, Watt Hrs, "C" charge/discharge rates, etc...) of the batteries.

Thanks for the explanations - much good info in there.


*************************************************

Hi Mike, I thought we texted together about this? But now I don't see your number so I must be thinking of a different person on this subject.

There are no issues with our batteries for the R1 with relation to how the vehicle charges the battery or cold temperature conditions the vehicle may be subjected to.

One of the easiest ways to confuse people is to make claims on subjects about which most folks know "something" about but not really how it works or the full-picture, one of these seems to be charging batteries. I've seen it hundreds of times where in online forums there are claims made about charging batteries that don't jive with reality. It's easy to say "it's a special algorithm to charge that one vs this one" but that doesn't really say anything. In charging a battery and in discharging a battery there is a chemical reaction occurring inside of the cell, voltage is a measurement of electrical potential energy and what that means is that electricity (electrons) will flow from a higher voltage source to a lower voltage if properly connected to one another through a conductive medium. The process of charging a battery cell is simply providing a higher-voltage source (the charger) to the cell, there is no magical or unique difference about it, there isn't some other factor or variable, it is pure and simple, voltage, that's it. So this means you connect the battery cell to a charger and current (electrons) start to flow, the rate of the flow is dictated by Ohm's Law (V=IR). Chargers monitor the current and adjust the voltage output to reach a particular amperage/current limit.

OK, so now with all that background, charging any battery is a function of "the charging curve" which for the most part is very boring and they are all the same, the only real changes happen at the end points (empty and full). A particular battery chemistry will become fully saturated (de-ionized, reduced, "charged") at a particular voltage and consequently will become (nearly) fully unsaturated (ionized, "depleted") at another voltage. The charged and empty voltages are what makes each chemistry "special" or different not the process of pushing or pulling current from the cell. So the real question when it comes to "is the charging compatible" are:

Does the Max voltage output of the charger (system) fall within the Max voltage range of the battery cell?
Does the Min voltage that the system allows the battery cell to reach before initiating recharge fall within the usable voltage range of the battery cell?
Do the Maximum currents/amperages of charge and discharge fall within the battery cell and BMS capability?

Those questions produce a real understanding of whether a battery can be compatible in a system. The "algorithm" is actually as generic as the above information, what are the max/min voltage set-points of the charger and what are is the max/charging current, there is nothing else special going on.

OK, this is a long email and explanation, I hope that is helpful, this subject is one that I find way too much misinformation online.

Alright to answer the rest of your questions;
Yes there are silicon warming pads in the R1 batteries from Ohmmu and yes they come on during charging to warm the battery above a set-limit. That limit is something we can change through OTA updates as we find necessary but it is designated presently to do the job properly in the conditions of the vehicle in any region of the globe where the R1 are sold/operated (automotive-grade, in other words)
The charging circuit is totally outside of the control of the 12V battery, it has no authority in the vehicle to command the DC/DC output (the charger); what it does is as soon as charging current starts to flow, if the temperature is below a set-point, it warms them up, the warming up process happens very quickly as the heat elements are attached between each cell. There are monuments of misinformation online about cold charging LFP batteries, mostly it is a total misapplication of the danger of charging Lithium-Ion (NMC, LMNO, etc) when cold-soaked (can lead to dendrite/crystals, which ruin cells and make unstable) but it is not the case for our battery cells at all. We don't warm them because it is a requirement to safely charge the battery, but it does lead to longer lifespan.

The video that folks are looking at is of a tear down from an old Model 3/Y battery (relatively old, the vehicles have only been around for 5 years), this battery design was scrapped by us years ago and is not how our batteries are currently built. The cells are different, the BMS is different and the assembly process is different. This is true across all of our batteries (the newest 3/Y are nothing like that old one), but especially so of any of the newer models (H3, H5, R1, etc) that we have only been making for the last year or so. The perspective of that video is a bit misguided as it was a faulty battery design from the get-go and not a representation of what we actually build today.

-Sean

So past the bloviating of this guy the meat of this response is that the warming only comes on when charging starts so it depends on how cold it is outside if I were to trust it. Here in the south where it's at worst a little below freezing that lag should probably be fine but I don't know that some place where it gets to -40 it would be a good call personally.

Also from what I gather the design in the video is an old and obsolete design according to the manufacturer. I could give them the point that they fixed the design but it is a little worrisome that they sold a defective design to begin with. Personally I don't really see the point in changing the batteries of a truck that's still under warranty but YMMV.

 

[Whale Blubber]

Necrotic thread, so forgive me, but any newer intel on this subject from the voltage experts? As part of a potential upgrade to my R1S audio, including an amp with some draw, I'm exploring alternatives to the stock 12V. Curious if any further experience is available a year later on the subjects raised here (cold weather heating / battery design).

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