IslandRoadster
Former Owner of #609
Here are some photos.
The battery is underneath the panel where the charging door is.
Is that any easier to reach than the right-front-fender mount? Looks like it’s blocked by the PEM and fender.
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Here are some photos.
The battery is underneath the panel where the charging door is.
Anyone know how to DIY replace the "Trunk 12 V battery"?
I have one of those after-market sound systems with a batter in the trunk and while I can see the battery, it seems like I would need to remove the side panel (behind the door) to get to it.
You have to remove the wheel and the front wheel well panel. That is where the stock subwoofer would have been located.
It's funny how this post has aged over the years. I fitted the Shorai LFX19 battery in 2015 and have had zero issues. I sold the car January and the new owner reports it's still had no issues even today. Cracks me up that there are people out there relocating the battery so it's easier to change rather than just fitting a better battery in the first place. Happy to take this result as I'm now going through the same mod on my Twizy and probably on the Model 3 also and getting the same skepticism from everyone. Lol
Based on my earlier testing, a couple of notes regarding the use of LiFePO4 (or similar) batteries in the Roadster (including a puzzle...).Sounds pretty good. Have you found a Shorai that's a good replacement for the Model 3 battery?
The only thing I haven't seen answered is how any of the 12V lifepo batteries handle cold weather charging. Do any of them have built in heating elements to warm the battery before allowing charging? Otherwise, I could see how you could be stranded if you park the car in below freezing weather. The BMS in the lifepo would have to prevent charging below freezing, which means eventually it would run out of 12V power and the car would shut down.
Just found one of these batteries should solve that problem:
Cold Weather Lithium Deep Cycle Battery | RELiON
The RB20-LT is a cold weather performance lithium battery that can safely charge at temperatures down to -20°C (-4°F). This 12V 20Ah battery is ideal for small solar applications, LED lighting and more.relionbattery.com
Ohmmu also makes a drop in Model 3 battery, but unclear if it has a heater.
12V Lithium Battery for TESLA Model 3
Battery Terminals: SAE, Positive Top Back LeftDimensions: 185mm x 116mm x 198mm (L x W x H) / +20mm for postsWeight: 9 lbsWhat's Included: 12V LFP Battery, Warranty Card ATTENTION: Please note that your vehicle may prematurely recommend 12V battery replacements when a LiFePO4 battery is...www.ohmmu.com
Based on my earlier testing, a couple of notes regarding the use of LiFePO4 (or similar) batteries in the Roadster (including a puzzle...).
The Roadster (specifically, the 2.x versions) keep a 13.8v trickle charge (less than an amp) going to the battery whenever the car is asleep. There is a DC-DC inverter in the ESS that provides this power. When the car is awake, that charging is switched to a higher power (a few amps), but still at 13.8v. So, this is very different than the more modern Tesla cars, where those cars depend on the 12v battery to keep the base systems running while the car sleeps. In the 2.x Roadster, the only time the 12v battery is "used" under normal conditions is for a few seconds after the "Unlock" button is pressed on the key fob. At that time the battery is put under a brief 10+ amp load, which I suspect is just a system test to be sure the battery can provide power in the event of a major power system fault. This is what generates the "12v battery service required" VDS alert.
So, the puzzle. In my testing, I never saw the voltage going to the 12v battery ever exceed 13.8v. The specifications for charging the LiFePO4 batteries require at least 14.2v for charging to occur, and 14.4 for balancing the cells. How are these batteries ever charged?
Survived -20 outside this year with no issues. The battery comes with a lot of insulation material and it’s tucked away. Not sure about a model 3 but I’m glad I swapped over.
I was just going by what the manufacturer specified, both the charge voltage and what is necessary for balancing. 13.8v meets neither of those requirements. I also remember reading some time ago (likely a different manufacturer) that their BMS won't actually go into charge mode until the applied voltage is above 14.1 or thereabouts. A good match for an alternator-based vehicle; not so good here. Note this is different than an SLA battery, where the external charger is directly connected to the cells.Lifepo doesn't need to charge above 14 volts. There's very little additional capacity above 14 volts, so for cell life it is better to not charge that high. 13.8V would be fine. As long as you can get the BMS to balance the cells, 13.8 is a fine full charge voltage.
Those look good. Just need to find the right size. And confirm how it handles low temp charging. If you live in a really cold place, the 12v might not charge, leaving you stuck.I don't yet need another 12v battery, but I came across these. Anyone know if one of these lithium replacements would be suitable for a v2.5 Roadster?
Or, should I just continue to stick with AGM style lead-acid batteries? I think I'm on my second after 11 years. I know from experience that the Roadster works just fine with NO battery even connected, as Tesla Service did that once accidentally. I was able to unlock the car by opening the charge port door and waiting a few seconds. Hey, maybe that's a theft deterrent? /s
Probably not a problem under normal circumstances. The battery is intended to be used under decidedly not normal conditions, where the car has a complete failure of the ESS. It, then, powers the flasher lights and such.Looking at sizes, the YTX9-BS is, I think, the standard size for V2+ Roadsters. Those are 5.9" Long, 3.4" Wide & 4.2" with Positive on left, Negative on right.
Noco says this model is the right replacement. Data Sheet says charging temp supported down to -10ºC. But, sheet also says the battery is only 3Amp-Hours of capacity, a lot less than the 8Amp-Hours for the YTX9-BS lead acid variety. Problem?