12V Failure message-plugged in. Switch to Ohmmu Lithium or Stay with Rivian 12v??

[babock]

If you have seen the tear down video of one of those Ohmmu batteries, you would never put one near your auto let alone in it. It's amateur hour how those batteries are cobbled together.

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[ScoobieSteve]

The temperature disadvantage is a huge one for those of us with actual winter climates.

This was a huge concern I had, but the Ohmmu batteries have a feature that pre-heats the battery in cold temperatures during charging to avoid the issue. I am just not sure if this is through the BDU, nor how reliable that is?

 

[IGR]

The temperature disadvantage is a huge one for those of us with actual winter climates.

This can be addressed with different chemistry like LiFeYPO4 which works fine down to -45 deg C. Or with dedicated PTC heaters. The only problem is this makes a more expensive battery.

 

[IGR]

This was a huge concern I had, but the Ohmmu batteries have a feature that pre-heats the battery in cold temperatures during charging to avoid the issue. I am just not sure if this is through the BDU, nor how reliable that is?

I would be skeptical whenever I see words “self heating” usually that means battery is heated due to it accepting a charge but that kinda defeats the purpose if battery is getting charged in cold weather….

 

[Time2Roll]

I would be skeptical whenever I see words “self heating” usually that means battery is heated due to it accepting a charge but that kinda defeats the purpose if battery is getting charged in cold weather….

Self heating is usually small resistance heaters built into the battery and controlled by the BMS. The BMS will stop charging the cells when cold but allow charging voltage to go through to the heaters.

Once heated somewhat above freezing the lithium charges much faster than AGM and no particular reason to reach 100%. AGM not fully charged each time is sulfating and permanently losing capacity toward the early death we read about.

I might be more interested in Ohmmu if I knew the real specs of the BMS and heating system.

Either way I would still stick with OEM until all warranties are gone.

 

[Riviot]

I'm trying to get my hands on that jumper cable, don't have a login for the tools store yet though.

ETA: These are definitely new instructions... They used to say jumper both 12v before reconnecting, or reconnect at the same time. I don't see that referenced anywhere anymore...

 

[Jakeblanton]

The factory battery (and any replacement) has a 2 year parts warranty. If you've had your battery replaced last year, you can probably get it replaced under warranty again now.

I just had mine replaced again today and did not know about them only being 36 month covered until they billed be almost $800. I have called and tried to message them, and have gotten nowhere, and they eventually ended the chat... I went from pretty mad to enraged angry over the customer service today. I was trying to type out the issue when they cut me off with a small speech written because it was not fast enough. I have to say, I am pretty bummed.

 

[babock]

This can be addressed with different chemistry like LiFeYPO4 which works fine down to -45 deg C. Or with dedicated PTC heaters. The only problem is this makes a more expensive battery.

LiFePO4 is usable(discharge) to 0°F but can't charge below 32°F.

If you have seen the teardown videos of the Ohmmu , you won't want them in your car.

 

[SwampNut]

If you have seen the teardown videos of the Ohmmu , you won't want them in your car.

I have, and I do. What’s your objection exactly? I’ve seen far worse.

I’m on my fourth set of batteries. I’m tired of this game. At least I’ve never been charged for them.

 

[babock]

I have, and I do. What’s your objection exactly? I’ve seen far worse.

I’m on my fourth set of batteries. I’m tired of this game. At least I’ve never been charged for them.

The way the wires are soldered onto the BMS. The crappy way they mount the battery cells in the case. The sealant they use to mount the BMS. A quality battery has a fixture inside the case that holds the cells and the BMS.

The car's charging is not setup for LiFePO4 batteries. After a while, the cells will go out of balance because the voltage will never get high enough to allow the battery cells to top balance.

 

[vordo]

does a battery tender fix the cell balence problem?

 

[babock]

does a battery tender fix the cell balence problem?

If it gets above the voltage that the BMS start to balance at which is typically a little above 14V. Most battery tenders just float charge a battery which is a much lower voltage. You need to use a true LiFePO4 battery charger.

 

[SwampNut]

All of these theories are backed by lots of science and documentation. Can't argue them. I've been using these batteries in everything for over ten years. None of this is a problem. They just work. I do nothing special. The only lead-acid batteries in my life are these stupid Rivian batteries. I have used LiFePO4 in motorcycles, boats, RV, generator, everything. They work. No special attention needed.

 

[IGR]

LiFePO4 is usable(discharge) to 0°F but can't charge below 32°F.

If you have seen the teardown videos of the Ohmmu , you won't want them in your car.

LiFePO4 not the same as LiFeYPO4, there is a difference.

 

[jrmbadger]

The Ohmmu seems decently constructed to me - if this Ohmmu video is to be believed: Ohmmu factory tour. The Ohmmu guide acknowledges toward the end of the video that they've made improvements in their construction methods since the days they used to use double sided tape and some other, less than ideal, construction methods.

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