Lightweight battery

[Cobra1956]

Has anyone switched to a lightweight battery? If so How did you address the coding and that huge piece of junk at the b+ terminal. Is there a way to lose all of that?

I am going to assume that the car does need to know if it is an lithium ion battery but had no issues using it in my other cars. Any info or help is appreciated!

[Suprgnat]

Originally Posted by Cobra1956

Has anyone switched to a lightweight battery? If so How did you address the coding and that huge piece of junk at the b+ terminal. Is there a way to lose all of that?

I am going to assume that the car does need to know if it is an lithium ion battery but had no issues using it in my other cars. Any info or help is appreciated!

Antigravity recommended coding the battery as an AGM of the same Ah rating.

[Cobra1956]

Thank you!

Also happened upon some additional info from BMW. It appears that the heat number is 105c. North of that it does stuff to protect a lead acid battery to prevent you from boiling off the water in the battery rather than converting it to acid. It also looks at low volts and bumps up the idle speed just a bit to give you 14.8 versus 14.3 volts. What I am getting from this, battery tender is your friend, short trips create most of the issues as you have a voltage regulator, track car with no water in the battery is probably zero issue but the tender probably dont hurt prior to an event. Will keep looking but think more weight reduction is on the horizon

[ZHPizza]

There's a handful of discussions on e90/etc forums with people going to a lithium battery without issue. Enough so that I'm not concerned about using an antigravity battery. Here's one that I saved talking about the coding:

https://www.m3post.com/forums/showthread.php?t=1823469

[Cobra1956]

Thanks, good information there. I think the whole thing revolves around mpg. Similar to running thinner oil in engines. It also seems that the lead acid battery they(bmw) sell the car with has water in the equation so heavy rapid charging most likely leads to overheating and boiling off water so if you drive short trips and you don't charge the battery at some point they have to make that up somehow. Telling the computer what battery you have in there is the way they avoid getting in trouble from things going sideways when they need to up the volts to get it charged. No free lunch! My bet would be that when this crap was designed they banked on at some point a car would get driven long enough to sufficiently charge the battery at a lower level of voltage output.

[Cobra1956]

Ready to put my Anti gravity battery in. My take on the programmable battery issue is this is all mpg junk. From my research a normal charge rate is about 14.1 volts and the higher charge is about 14.7. Neither of these should cause any issue to a battery but it my theory is correct it works as follows. BMW assumes that you will drive your car sufficiently to charge the battery so basically long enough trips to charge at low volts. In the event you don't the ecu says we need more juice and the alternator charges at the higher rate. Higher rate equals more drag and lower mpg. Years back when I went to the lithium battery in the old car I read thread on batteries exploding and what I found was in most cases the wrong kind of charger was being used. Where a normal lead acid charge starts with higher amps is trails off as the battery nears full charge. From what I see with my lithium charger it is the opposite. Litum being seal eliminates the issue of possible water boil off on conventional lead/acid batteries and from a liability standpoint there is no way a mfgr would send something out the door that has no voltage regulator so if your liltium is charged somewhat enough to start your car you should be good to go. My question revolves around the spaghetti on top of the battery. From the best I can tell it is a fusible link in the event of accident and b+ distribution. I have not chased the circuits yet but it is possible that some of the wires are no longer needed based on what gets pulled out of the car.
Does anyone have a wiring list of what is tied into the current monstrosity on top of the battery. Plan is to tie in small b+ buss and send it. Only issue should be what gets tied to the can bus system and how it effects other systems.
Airbags are gone. So maybe fuel pump or similar.
If anyone has anything please share.
If not I will let you know what I come up with after the delete.
Thank you

[Cobra1956]

Busted out the battery today. Here is the thought process. Feel free to shoot holes in any of it. This battery started my s54 with 50 wt oil. I will assume that the n55 has less compression so it should be able to do it. The mess that sit on the top of the battery should be able to be completely eliminated. That would leave you with the safeties at the positive and negative sides on the cables. The rest of this is just a fancy way to add more positive connections to the battery. If I put eyes on the two plug ends they will fit on the post left on the positive terminal, or you could modify the plastic mess to add another port if needed. Current should not be any issue as the flow is from negative to positive and there are still fuses up stream on the positive side.Out with fatso and in with this:
Poor camera skills are back. This gives you this on the other side. One post and a few ports for plugs.

You still have the positive and negative here.



There is also and option of using a small buss bar like this to spread out the termoinals if desired.

[scratchgolf135]

Shouldn't be an issue. I have a tiny 4.5lb braille microlite in mine and it starts my N54 with ease.

[Cobra1956]

Battery started the car but not well. I can't remember when I bought it so I replaced it with a little more powerful one.


Installed and mounted yesterday. 5lbs total so about 50 pounds lost.

[ZHPizza]

Also got mine installed and it's been doing a great job starting the car

Managed to make the positive terminal contraption fit nicely on top, using a thick sheet of foam as a spacer. This also filled the gap enough to be able to use the OE strap thing to hold it in place.

Was really happy to see a 40Ah AGM coding option in Protool too. Overall a great install that shaved 47lb.

[Cobra1956]

That batter give you nice options with the ability to use either side for the terminals. Like that!

[ZHPizza]

Fyi the Antigravity Bluetooth battery monitor is pretty awesome. Check out the tools in the app!