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Boston Swing Cell Auxilliary Battery Upgrade Replacement
Bored, broke and unemployed so I built this today. Drove 40 miles just now with this new battery. No issues. Resting voltage is 14.45V. I am converting the entire car to Lithium. Thought I'd share for all the DIY'ers here. I really enjoy this forum. Lots of good, knowledgeable folks here. I appreciate you guys. Thank you for all your help. This is for ya'll (:
Nice little welder... if you pull TPMS sensors apart they have watch / remote fob type batteries potted inside. You can dremel them out and fit new. But welding on the tabs is the issue.
Not pulled the car ones apart so not 100% sure what’s on the 221, but schrader ones can be done
Couple of comments on the hacks discussed above:
1. Are you certain the original SLA aux battery charger will safely charge lithium batteries?
2. I thought the coin cell batteries in TPMS sensors are purposefully not replaceable so that the assembly doesn't accidentally fly apart while being centrifuged at ~1500 rpm.
Couple of comments on the hacks discussed above:
2. I thought the coin cell batteries in TPMS sensors are purposefully not replaceable so that the assembly doesn't accidentally fly apart while being centrifuged at ~1500 rpm.
that’s the story they want you to believe - the way they make those, the batteries are forced into the housing not out of it, exactly the same with the slightly earlier ones with the valve built in.
Charging is not an issue. I did this because I'm going to replace the starter battery with LifePo4. I'm pulling the AGM under the hood. I'm putting 320AH LifePo4 cells in the trunk and running 1/0 cable from the trunk to the battery connections up front to make the connections. This way we are all the same chemistry and I don't have to deal with DC contactors or relays to isolate different batteries when the car is off.
that’s the story they want you to believe - the way they make those, the batteries are forced into the housing not out of it, exactly the same with the slightly earlier ones with the valve built in.
Interesting that nobody is rebuilding them like alternators, starters and other components are rebuilt.
Charging is not an issue. I did this because I'm going to replace the starter battery with LifePo4. I'm pulling the AGM under the hood. I'm putting 320AH LifePo4 cells in the trunk and running 1/0 cable from the trunk to the battery connections up front to make the connections. This way we are all the same chemistry and I don't have to deal with DC contactors or relays to isolate different batteries when the car is off.
I have no idea how this addresses the charging issue, but best of luck with how ever it turns out.
Charging is not an issue. I did this because I'm going to replace the starter battery with LifePo4. I'm pulling the AGM under the hood. I'm putting 320AH LifePo4 cells in the trunk and running 1/0 cable from the trunk to the battery connections up front to make the connections. This way we are all the same chemistry and I don't have to deal with DC contactors or relays to isolate different batteries when the car is off.
Please let us know how that works out, how you did the cabling etc.
also check the novel name for the secret designed not to fail version at the bottom of each list
Yes, this is what I meant -- starters and alternators are rebuilt because it's economically viable. I suspect TPMS sensors are not rebuilt because the rebuild cost exceeds the cost of a new one.
Senecat, there should be no battery in your boot - yours is the later design ??? it has a big one up front on later cars it does everything
and the one you just did under the dash, is only on the w221 to get the ISM to shift if the front battery has died.... although it would be nice if it did the doors so you can open the car and sort the one under the bonnet
other later Mercs the axu "motorcycle battery" helps the cars logic for start stop - for some reason
I do wonder how the car will cope with the box of tricks many cables connect to in front of the big battery... if you have a lithium simple thing there. Many aftermarket retrofit Lithium ones include their own battery management system - with logic for how it charges and how it behaves.... check out complicated idea for bikes... https://www.motobatt.com/en/hybrid-batteries
There's nothing to it as far as converting to Lithium. The AGM under hood will be deleted, the LifePo4 cells will be mounted in the boot, and the LIN line to the alternator will be disconnected, charging the cells at a constant 14.5V instead of using the computer controlled variable charging program. The 1/0 OFC cable connections under the hood are simple. Three runs of 1/0 from the rear battery to the front; One cable from battery positive to alternator charge post, one cable from battery positive to the factory under-hood battery connection, and one cable from battery negative to factory under-hood negative. None of this is new anymore, competition stereo folks have been doing it for years now, the popular Lithium chemistries being LTO, LifePo4, and LiMn2O4.
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
