OVMS on my app requires me to click on the image of the trunk lid in order to "wake up" the temperature sensors.
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Replacing the 12V aux Battery
- Thread starter scotty2541
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- Roadster
IslandRoadster
Former Owner of #609
I was going to replace the 12V battery and was thinking about doing it with a lithium ion replacement battery. Unfortunately none of the sizes are exact and there was delay in ordering, so I just went with the tried and tested AGM battery from the auto parts store.
Ohmmu has the same length & width + 1cm taller.
https://www.ohmmu.com/product-page/12v-lithium-battery-for-tesla-roadster
IslandRoadster
Former Owner of #609
have to do that next time. Hope they’re still making them in five years when I need to replace the new AGM battery I bought. Thanks for the tip. Should have asked sooner!
found this old post vs the two
Replacing the 12V aux Battery
"I have a 40ah Lithium battery in my Roadster's trunk to power the sound system...another one of the reason's that I did not replace my 12v battery (running the Roadster's other systems), is that Lithium batteries require a special charger...the Roadster is recharging a 12v lead acid battery from their Lithium ESS...to me, this means that the "recharging setup" between the ESS & the 12v is NOT using a Lithium charger for the 12v, it is using a lead acid charger.
I am not nearly technical enough to understand the differences between these two types of battery chargers, so I would not make this change as I would not want to risk damaging the ESS / damaging the 12v battery / starting a fire due to an incompatible recharging setup between the ESS & the 12v.
The small Lithium battery charger that I use to recharge my 12v Lithium battery for my sound system is a special charger for Lithium batteries...it pre-conditions the battery prior to charging it...charges in stages, and has a few other features that the Lithium battery manufacturer's say that a Lithium battery charger must do (that a lead acid battery charger doesn't do) to safely charge the Lithium battery...I mean, this could all be marketing buncombe, and the Lithium and Lead acid chargers are identical, but for a few quid, I was not going to take a chance of damaging my car by going against the manufacturer's advice... "
Replacing the 12V aux Battery
"I have a 40ah Lithium battery in my Roadster's trunk to power the sound system...another one of the reason's that I did not replace my 12v battery (running the Roadster's other systems), is that Lithium batteries require a special charger...the Roadster is recharging a 12v lead acid battery from their Lithium ESS...to me, this means that the "recharging setup" between the ESS & the 12v is NOT using a Lithium charger for the 12v, it is using a lead acid charger.
I am not nearly technical enough to understand the differences between these two types of battery chargers, so I would not make this change as I would not want to risk damaging the ESS / damaging the 12v battery / starting a fire due to an incompatible recharging setup between the ESS & the 12v.
The small Lithium battery charger that I use to recharge my 12v Lithium battery for my sound system is a special charger for Lithium batteries...it pre-conditions the battery prior to charging it...charges in stages, and has a few other features that the Lithium battery manufacturer's say that a Lithium battery charger must do (that a lead acid battery charger doesn't do) to safely charge the Lithium battery...I mean, this could all be marketing buncombe, and the Lithium and Lead acid chargers are identical, but for a few quid, I was not going to take a chance of damaging my car by going against the manufacturer's advice... "
IslandRoadster
Former Owner of #609
I have read that some lithium batteries have a built-in battery protection system that prevents the kind of damage you describe, or so says the company selling them. They say, "Our lithium ion technology uses the latest and most advanced built-in battery protection system to prevent damage to the battery. You may utilize a standard charger for our products, although in some cases a lithium charger may be required to charge the batteries." I have not basis to verify the claims.
I put in the Ohmmu 12 volt battery last December. No complaints whatsoever and the company's personnel is incredibly responsive to any questions. Fit perfectly and guaranteed for four year which if it lasts at least that long, almost makes up in the increased cost for what would have been spent for two or three OEM batteries. Plus I do not have to worry about dealing with low 12 volt battery warnings and replacing the battery for several years.
IslandRoadster
Former Owner of #609
watched @CM_007 ‘s son Randy replace the battery in #609 today. Makes insanely short work of it. He removed the wheel, opened up the panel, replaced the battery, closed it back up again, and reinstalled the wheel in 15 mins. Would have taken me at least 1.5 hours.
n2mb_racing
Active Member
Anyone know how the 12V lithium replacement batteries deal with charging below freezing? The BMS in the battery has to prevent it since the car doesn't know it's a lithium battery, but since it is a 2-wire BMS, that means cutting off the battery. So, then are you stranded?
IslandRoadster
Former Owner of #609
I would be interested in real-world performance too. I suspect it’s going to vary from battery to battery depending upon the cells and battery management system.
The battery company that @drewski mentioned says on their website “Our in-house Thermotron chamber allows us to push the envelope with capabilities of reaching down to -70° Celsius (-94° F) on the low side and up to 185° Celsius (365° F) on the high side. Testing has been performed on all products we sell (per IEC so we can stand behind our batteries 100%.”. That quote implies, but does not directly state, that they can operate without problem in lower temperatures.
n2mb_racing
Active Member
You can discharge a lithium ion battery down to very low temperatures, but you cannot charge any lithium ion battery below freezing. I don't know how you can deal with this if you live in a very cold climate. That's why all Tesla cars still have a lead-acid 12V battery. I'm pretty sure if there was an obvious solution, they would have switched to a 12V lithium ion battery a long time ago.
I think you'd have to put in a 12V battery heater as well, and I'm guessing they thought it wasn't worth the cost when a properly charged AGM battery will last ~4 years.
IslandRoadster
Former Owner of #609
From reading this article, even lead acid batteries have problems below freezing, although the article notes that they are more forgiving the LIon. Assuming one parks one's car with a full battery, when one starts the vehicle, the BMS should prevent charging if internal battery temps were below freezing. But once the battery begins to discharge, temps should rise within the battery due to the discharge, shouldn't they? That would then allow the BMS to charge the battery. What's the temperature rise of LIon batteries when they discharge?
Hi CoolVariable,
You may be on your own here...
Our 12V batteries are generally located inside of the right front wheel well...
Gruber sells a replacement kit where the "wheel well" battery is in your trunk.
But an aftermarket sound system would be a unique situation...
Any pictures to help us???
Aftermarket installer name??? (In Michigan I probably cannot help...)
Shawn
You may be on your own here...
Our 12V batteries are generally located inside of the right front wheel well...
Gruber sells a replacement kit where the "wheel well" battery is in your trunk.
But an aftermarket sound system would be a unique situation...
Any pictures to help us???
Aftermarket installer name??? (In Michigan I probably cannot help...)
Shawn
Here are some photos.
The battery is underneath the panel where the charging door is.
Attachments
n2mb_racing
Active Member
Neat spot to put it. I always wondered why there was so much empty space in there...
But , probably hell to get at. If you replace it, definitely replace it with a high quality lithium battery so that you don't have to replace it again.
Although, if you live in Michigan, I'm not sure that's a good idea. I still have no idea how the 12V lithium batteries handle charging below freezing. They shouldn't allow it, so does that mean your car dies when it gets really cold because the 12V battery BMS has to save itself?
n2mb_racing
Active Member
Maybe consider a 12V lithium battery with a built in heater, like this one. But, I don't know if it will fit.
Cold Weather Lithium Deep Cycle Battery | RELiON
Cold Weather Lithium Deep Cycle Battery | RELiON
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