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Ohmmu Battery & 2020.28.6 update
- Thread starter lUtriaNt
- Start date
It doesn't report a voltage, there is a voltage out of the battery and it comes from the 4 LiFePO4 cell voltages summed together. A BMS can't fudge that unless it implemented a massive (>100A) DC-DC converter which is big, expensive and inefficient and complicated to also allow charging, Bottom line, they didn't fudge the voltage.
What a BMS can do is turn off the battery if the voltage drops too far or cut off charging when the battery reaches a set voltage.
Of those two things, the only one that could accomplish anything is letting the battery charge to a higher voltage. Tesla's 12V charging circuit is set up for a lead acid battery and would expect that after thinking the battery was fully charged that it would drop to a certain rest voltage when charging ceased. If the rest voltage was too low, because the battery cut off charging at to low a level, the system might consider the battery to be defective.
Why would Ohmmu set the cut off voltage lower than a regular lead acid battery would output would either be they didn't realize it or they picked a lower voltage so battery life would be better. It isn't like Tesla publishes specs for what their charger circuit does and there is also the possibility that Tesla deliberately set out to spank Ohmmu.
just to follow up in case others are on the fence about purchasing/watching for updates,
ive had the new Rev 2 battery in the car for a little over 3 weeks now and no 12V error. looks like ohmmu got the issue resolved.
ive had the new Rev 2 battery in the car for a little over 3 weeks now and no 12V error. looks like ohmmu got the issue resolved.
Appreciate the update. I was going to ask how the Rev1 worked out through last winter however I see you’re in L.A. so it’s moot. I keep reading (though probably misinformation) about possible issues in sub cold/zero temps......I’m sure unfounded.
Ski
Just what I needed to hear. How long do you think the OEM would last on a tender if I kept it as a backup? Or would that even be necessary? I somehow trust the Ohmmu more, nevertheless. Or just recycle it? Have NO idea the life left in it.
Ski
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EfficientWatts
Member
Can someone measure the voltage at the terminals for the updated rev 2 ohmmu batteries? I'm curious to see if it matches the voltage of the lead acid batteries which does seem to be the case. I saw someone do it earlier in this thread for the rev1 and the lead acid but not the rev2.
PSA: Rev1 is actually more robust than Rev2... so at 90-100% SoC I would expect to see a lower voltage read at the terminals from a Rev2. But if it takes the revised design to prevent errors for more recent Model 3/Y builds - more power to it.
android04
Active Member
I don't know if the Rev 2 batteries that people in this thread received are the same (I'm sure they are), but Ohmmu updated them to make them lighter as well. They are now 8.5 lbs vs 11.5 lbs previously. They might have reduced the capacity some to better line up with the OEM battery.
SageBrush
REJECT Fascism
Sorry to hear that. I have this notion that my high-ish vampire drain is related to the small capacity 12v that Tesla supplies with the car.
Any capacity LiFePO4 has a far faaar flatter discharge curve than a lead-acid (any chemistry and tech) plus a significantly better charge/discharge cycles stat vs. even deep-cycle or marine conventionals.
After 2+ years with an Ohmmu, I can still atest to (as I posted many times in the past) a. lower vampire drain b. improved Premium audio speaker response c. potentially less frequent or shorter recharge cycles.
No impirical evidence for any of the above. All butt dyno spec. I leave the data acquisition and analysis to the younger whipper snappers on and off here. Those who might have time and care for that kind of thing. I used to decades ago, not anymore.
After 2+ years with an Ohmmu, I can still atest to (as I posted many times in the past) a. lower vampire drain b. improved Premium audio speaker response c. potentially less frequent or shorter recharge cycles.
No impirical evidence for any of the above. All butt dyno spec. I leave the data acquisition and analysis to the younger whipper snappers on and off here. Those who might have time and care for that kind of thing. I used to decades ago, not anymore.
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