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

[electruck4x4]

Whether you are running additional accessories on your truck, live in a cold climate, or just want some added peace of mind, replacing your Rivian's stock lead acid battery with a pair of Lithium Iron Phosphate batteries from Ohmmu is a great choice. These batteries are lighter and more energy dense than the stock units, plus they have built-in thermal management and Bluetooth remote monitoring (how cool is that?). Best yet, they come with a 4-year warranty from Ohmmu. Check them out in the new electronics section of electruck4x4.com. Buy now and get free shipping to the lower 48 states!

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[Visket]

Questions: Why the "Tie Down Spacers"? What are they made of? How thick are they? Where are they installed (top / sides / front / rear?

 

[Visket]

Oh - another question: Am I reading that these batteries have built-in heating systems that will not allow them to get below minimum charging temperature? The way the verbiage is worded, one could interpret it as simply saying "these batteries heat up while being charged", which is a totally different scenario. Thanks!

 

[Aag12]

Can you provide details on testing with a rivian and how they work?

Last thing I would want is more 12v issues but rivian denying claims since these are 3rd party batteries.

 

[electruck4x4]

Questions: Why the "Tie Down Spacers"? What are they made of? How thick are they? Where are they installed (top / sides / front / rear?

The spacers go under the battery tie-down, which is on the top. I'm not sure how thick they are, but they are made of plastic, rubber, or something of the like.

They are self-heating in that they warm themselves when charging in low-temperature conditions.

@Aag12 I'll have to ask about testing. Is there specific test info/results you are looking for?

I do know several members on here and other forums/groups who have them and like them. (This is what prompted us to start carrying them). I know there were some issues with Tesla applications, but that's also not a 12v battery. So, it's not exactly comparing apples to apples. Regardless, Rivian could only deny your warranty if the battery itself had caused the issue.

 

[Aag12]

The spacers go under the battery tie-down, which is on the top. I'm not sure how thick they are, but they are made of plastic, rubber, or something of the like.

They are self-heating in that they warm themselves when charging in low-temperature conditions.

@Aag12 I'll have to ask about testing. Is there specific test info/results you are looking for?

I do know several members on here and other forums/groups who have them and like them. (This is what prompted us to start carrying them). I know there were some issues with Tesla applications, but that's also not a 12v battery. So, it's not exactly comparing apples to apples. Regardless, Rivian could only deny your warranty if the battery itself had caused the issue.

Only testing is just to make sure a few users have tested them and that they're durable. That's all!

 

[Visket]

They are self-heating in that they warm themselves when charging in low-temperature conditions.

I don't mean to belabor this point, but this is a "make-or-break" topic for me.

LiFePo4 will not charge at (or below) freezing temperatures. At least they *shouldn't*, because they can explode, or at least murmur unspeakable expletives. LiFePo4 batteries will provide voltage well below freezing, but not accept it.

That's why the good ones have Battery Management Systems (BMS) with temperature sensors that prevent the battery from being charged if the temperature (internal, where the sensor is located) is too high or too low.

My question: Do these batteries have active heaters that will prevent the battery from reaching "below freezing", and therefore be able to start charging in the first place?

And if not, what will the Rivian do when it tries to charge the battery, and the battery won't accept the charge? This scenario probably happens anyway with the lead-acid batteries, so I don't think this is as much of an issue.

Thanks -

Mike

 

[NY_Rob]

These have a built in BMS correct?

 

[shrink]

The video in the 1st post has a teardown of an Ohmmu battery. They may have updated it since then.

Perhaps contact Ohmmu directly with technical questions rather than the reseller?

https://teslamotorsclub.com/tmc/thr...nce-over-the-years-on-ohmmu-batteries.302131/

 

[E-lectric]

The video in the 1st post has a teardown of an Ohmmu battery. They may have updated it since then.

Perhaps contact Ohmmu directly with technical questions rather than the reseller?

https://teslamotorsclub.com/tmc/thr...nce-over-the-years-on-ohmmu-batteries.302131/

I agree with your comments and would like to see what develops from this. I am not inclined to purchase these after viewing the teardown of their battery on the video above. I watched their how to install their batteries in a Rivian R1T and was impressed with it, until viewing above...

 

[electruck4x4]

I agree with your comments and would like to see what develops from this. I am not inclined to purchase these after viewing the teardown of their battery on the video above. I watched their how to install their batteries in a Rivian R1T and was impressed with it, until viewing above...

I'd definitely suggest pinging their support team. They are very responsive and highly knowledgeable.

 

[electruck4x4]

These have a built in BMS correct?

Correct

 

[electruck4x4]

I don't mean to belabor this point, but this is a "make-or-break" topic for me.

LiFePo4 will not charge at (or below) freezing temperatures. At least they *shouldn't*, because they can explode, or at least murmur unspeakable expletives. LiFePo4 batteries will provide voltage well below freezing, but not accept it.

That's why the good ones have Battery Management Systems (BMS) with temperature sensors that prevent the battery from being charged if the temperature (internal, where the sensor is located) is too high or too low.

My question: Do these batteries have active heaters that will prevent the battery from reaching "below freezing", and therefore be able to start charging in the first place?

And if not, what will the Rivian do when it tries to charge the battery, and the battery won't accept the charge? This scenario probably happens anyway with the lead-acid batteries, so I don't think this is as much of an issue.

Thanks -

Mike

Hey @Visket , no worries. There are actually silicon warming pads between the cells which kick in at a set low temp point, but only when charging is active.

 

[Visket]

I've never seen that video, but it bring up many good points, one being freezing temps. Another being that he did not find a temperature sensor inside the battery.

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. The Tesla apparently "thought" the battery disappeared, because, for all intents and purposes, it did. Why the LiFePo4 battery (in the Tesla video) stopped providing juice while still within it's operating parameters, is puzzling.

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. Let's say the charging system is programmed to initiate a charge at 12.2 volts. LiFePo4 batteries keep pushing output voltage above 12.4 volts (or so) until they are "spent", and will then rapidly drop voltage until they die a few moments later. A lead-acid battery will drop slowly from fully charged down to 12.2 volts over a span of time, When it reaches 12.2 volts, it will still have a long time span of sub-12.2 volt usage - maybe something the charging system is counting on. Meanwhile, you may have LiFePo4 batteries that are at 15% capacity, but the charging system doesn't know that because the LiFePo4 batteries are still providing 12.4 volts.

Don't forget that LiFePo4 batteries will likely absorb more current (amps) during a charging cycle than the DC charger was designed to output (due to the internal resistance of lead-acid batteries), thereby maxing out the charger's capability for a span of time. So your DC charger had better be designed to push maximum amperage for a period of time.

I could go on and on.

All-in-all, a Rivian is not a Tesla. And it all depends on the software and DC-to-DC charger driving the charging voltage/amperage, etc..

None of which we have answers for.

With that said, ElecTruck4x4 is saying that they have several members of this, and other forums that like the batteries. Maybe those running the LiFePo4 batteries would care to share their experience?

I would think twice if I lived in a cold climate, though. No temperature sensor = Bad Thing.

And I, personally, will wait and see. I know from personal experience that replacing a lead-acid battery with a LiFePo4 or Liion is not a "drop in" affair. At least in the several applications in which I have performed the swap, including RV house batteries (had to buy a new LiFePo4-compatible converter), handicap scooter (charger and charging wiring had to be upgraded), and a 24 volt electric trolling motor powered pontoon boat (charger, again).

Perhaps an email to our respective Guides and/or Service Centers will put this topic on the table for the engineers - as a software enhancement, if need be?

Anyway, I'm done. Waiting and seeing....

 

[Visket]

Hey @Visket , no worries. There are actually silicon warming pads between the cells which kick in at a set low temp point, but only when charging is active.

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!

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