DeepBlue3
Member
Do you know what the actual usage is between charge cycles? Whether in Ah or Watt/hours. Would like to know how much power is consumed from 14.15v to 12.6 or when the charge cycle restarts.
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Longer term Ohmmu experiences?
- Thread starter Durzel
- Start date
All I know is the owners manual in specifications shows 33Ah. The factory AtlasBX for a model 3 is 45Ah.
android04
Active Member
I installed a battery monitor with a shunt that measures the energy in and out of my OEM battery in September 2021. I have only ever seen it cycle less than 3 Ah from full capacity, which is a very shallow discharge. By the way, my OEM 12v battery is 4.5 years old and has 87k miles.
israndy
Supercharger Hunter
It may be your car is more active than other owner's cars. If a car sits at the airport for a month and the HV batt is off, just driving that card reader and bluetooth could draw more than 3 Ah. The HV batt recharges when the 12v batt gets too low, but a 45 Ah battery shouldn't read as low after only 3 Ah.
What battery monitor did you get?
What battery monitor did you get?
Dysan911
Member
I was just about to ask you if got anything yet. I’m tempted to install my V3 and see if I have the same results as you on 2022.24.8.
android04
Active Member
It is possible that my car charges my specific battery more often due to its age or something it measures on it. In my case, it makes no difference if I check the battery meter multiple times a day or let the car sit for 3 days -- it never reads less than about 3 Ah less than a full charge. If I leave Sentry Mode on then it stays at a full charge the whole time.
This is the battery monitor that I've been using https://smile.amazon.com/AiLi-Voltmeter-Ammeter-Voltage-Motorhome/dp/B07CTKYFTG/
Dysan911
Member
Will do. Should I top mine off on a trickle charger first? It’s been in the shelf for a couple months. Also can you use a regular 12v battery trickle charger on them?
Good idea to top off to at least 90-95% SoC (not sure you want/need to max it out).
Ohmmu's and other LiFePo4s do indeed prefer a different trickle charger profile from legacy batteries. There are dedicated and dual-mode trickle and fast chargers for them.
Ohmmu's and other LiFePo4s do indeed prefer a different trickle charger profile from legacy batteries. There are dedicated and dual-mode trickle and fast chargers for them.
Previous versions Sean had said a regular charger BUT I purchase a trickle charger for Lithium batteries on Amazon. I would contact Ohmmu again to see what charger. In theory the BMS should protect the battery but they should know for sure. I also received a letter from Ohmmu that they were considering restarting production of the battery for M3/Y. I would be happy in install the V4 when I see enough usage that the failure messages has been resolved.
Dysan911
Member
Yeah, I actually found a Li 12v Battery charger on Amazon. It'll be here Friday. I also have a V4+ on order with Sean but he told me that it's going to be held in their fulfillment area until those are ready to ship in a few weeks. If anything the V4+ has a BT-controlled BMS that he mentioned would allow us to reset the Battery via an App, quick and easy should Tesla trigger one of those hard amber alerts. Hopefully, the latest software from Tesla will prove to resolve the failure messages though.
If this is true, how do they ever work in a Tesla, which charges them as if they are Lead Acids?
israndy
Supercharger Hunter
Prefer doesn't mean Only Works this one way
You can trickle charge lithium batts, but it doesn't do much for them, they don't have the high self discharge rates of other battery chemistries.
Just as easy to charge up the lithiums twice a year and save all that wasted electricity that would be converted to heat
In the car the batts are in use so they run down from use and then the traction battery connects and charges them back up, not trickle charged at all in any car, just lead acids in storage
You can trickle charge lithium batts, but it doesn't do much for them, they don't have the high self discharge rates of other battery chemistries.
Just as easy to charge up the lithiums twice a year and save all that wasted electricity that would be converted to heat
In the car the batts are in use so they run down from use and then the traction battery connects and charges them back up, not trickle charged at all in any car, just lead acids in storage
Easy. That is exactly where the LiFePO4 BMS comes in, and gets (or at least pre-2022.24.x/.28.x, got) into all kinds of fun arguments with the VCFront BMS logic.
Plenty of cheap and not-so-cheap LiFePO4 chargers out there for shelfed Ohmmus.
So many people believe a BMS is magic.
It has 2 jobs:
Shut off if the voltage gets too low, too high, or the current gets too high
Balance the internal cells
The Tesla charge algorithm doesn't trigger the too high or too low logic. The BMS is completely transparent. It cannot change voltages. Tesla detects a Lithium because the whole profile of the battery is different. I know this because I've hooked up a LFP with zero BMS and it still triggers the VCFront.
If the BMS could magically adapt the battery to work in a Tesla, it wouldn't need a "special charger" when it wasn't in a Tesla either.
The complete irony here is people that believe you need a special charger for an LFP when it's out of the car, but somehow the Tesla charger which is very much tuned for Lead Acid will work just fine. It can't be both.
That said, the whole reason we use 4S LFP is that it's actually a pretty good simulant of lead acid and charges just fine on a lead acid charger.
As you stated, there is no magic here - with or without a BMS, an LFP is simply quite different from a Lead-acid chemistry battery.
No harm is trickle charging an LFP with a vanilla Lead-Acid/AGM/Spiral Cell/etc charger (especially if modern/profiled vs an old school constant voltage/constant current charger) but that doesnt mean its optimal for LFP chemistry. For that, an LFP-friendly trickle or rapid charging profile is needed and there are dedicated chargers for the job. Teslas LVB charging logic in the older (pre-15.x v LVB 3/Ys) is of course catering to a vanilla automotive lead-acid.
The BMS inside the Ohmmu housing (regardless of how primitive it might be) simply helps the LFP cells handle some edge cases, with whatever the outside world throws their way - for example OVER voltage, OVER temperature (while charging or resting), and OVER current (shorting of terminals included).
No harm is trickle charging an LFP with a vanilla Lead-Acid/AGM/Spiral Cell/etc charger (especially if modern/profiled vs an old school constant voltage/constant current charger) but that doesnt mean its optimal for LFP chemistry. For that, an LFP-friendly trickle or rapid charging profile is needed and there are dedicated chargers for the job. Teslas LVB charging logic in the older (pre-15.x v LVB 3/Ys) is of course catering to a vanilla automotive lead-acid.
The BMS inside the Ohmmu housing (regardless of how primitive it might be) simply helps the LFP cells handle some edge cases, with whatever the outside world throws their way - for example OVER voltage, OVER temperature (while charging or resting), and OVER current (shorting of terminals included).
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ANY 12 volt battery 51R with a minimum 33Ah rating (per the manual). Most 51R's exceed that. The factory AtlasBX is 45Ah. Advance Auto has a DiehardEV battery (it's an AGM battery) and is sized the same as the AtlasBX. I had a 51R AGM and the clamp was all the way down. Snug but not tight enough to prevent a small movement. The Diehard fits right. No issues being AGM. 41Ah. Is supposed to last 30% longer than standard AGM. Not suitable for ICE cars nut designed for EV's. Some may grunt it's not lead acid and wont last in Tesla but it has a 3year warranty and they are marketing it for Tesla.
Even Tesla themselves? They are reasonably priced. And given your join date, it should be under warranty as well unless you are trying to do a "proactive" replacement.
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