BMW AGM battery or Lithium battery?

[pipiyangtw]

Anyone heard of factory BMW AGM battery or Exide intelligent power car battery? or some light weight lithium battery? Is it fit old school cars like our Z3's?

[Telecomtodd]

You don't want a lithium battery. Lithion ion batteries require specific charging systems, and Z3s (in fact nearly all cars) don't come close. You are far better off using a commercial off-the-shelf - COTS - battery.

[pipiyangtw]

You don't want a lithium battery. Lithion ion batteries require specific charging systems, and Z3s (in fact nearly all cars) don't come close. You are far better off using a commercial off-the-shelf - COTS - battery.

Sometimes my volt gauge shows 13v~13.5v(not at 14v), is it means the battery will be dead soon?

[rotorhed]

I've been using the Braille 17LB AGM battery for about four years, no issues. (Tirerack or AutoAnything.com)

[mpire]

I just went with a Braille AGM as well.

Although the one from Autozone would probably do just as well.

The factory battery is cheaper than the Autozone battery.

[Sammy Sandbag]

Check out Deka lightweight AGM batteries, they actually make batteries for several companies, including Braille. Braille slaps on a different sticker and doubles the price.

[BraveUlysses]

Check out Deka lightweight AGM batteries, they actually make batteries for several companies, including Braille. Braille slaps on a different sticker and doubles the price.

Was going to say it, but you beat me to it. I found that the Deka battery I had a few years ago was not ideal for a daily driver.

[Sammy Sandbag]

Was going to say it, but you beat me to it. I found that the Deka battery I had a few years ago was not ideal for a daily driver.

They make several different sizes. As long as you don't go too small, you should be alright, depending on how often you drive. I have a 14 lbs Deka in my Toyota Spyder, and it turns it over easily. I keep it on a battery tender when not in use for more than a few days. They do make them as light as 9 lbs, but that's probably getting too small for a 6 cyl unless it were track only.

[Remotion]

Lets up this thread. Those arguments mentioned in the second post are pretty much made up and rubbish.

Does anyone have a lithium battery on their Z3? I am going to install next summer LiFePo4 -battery with BMS but would like to know if somebody has experiences.

Battery tech has gone on in three years a lot... 30Kg weight saving on a 1100-1200Kg car is almost 3% of total dry weight, and it's of from the very utmost point of a car.

[Zandr]

Lets up this thread. Those arguments mentioned in the second post are pretty much made up and rubbish.

Does anyone have a lithium battery on their Z3? I am going to install next summer LiFePo4 -battery with BMS but would like to know if somebody has experiences.

Battery tech has gone on in three years a lot... 30Kg weight saving on a 1100-1200Kg car is almost 3% of total dry weight, and it's of from the very utmost point of a car.

"With BMS" is the key here. The second post is spot on, and that's what the BMS is doing. Those weren't readily available a few years ago. To be honest, I'm not familiar with any now, so I'd be interested in your sources.

[z3papa]

I've done several lightweight batteries from Braille, Deka and Shorai. The weight savings has an exponential effect IMO to what you would think on MPG and acceleration. One thing you need to take into account is having a battery tray/hold down since the battery will be smaller. I have one for sale in my part out thread. Deka is probably better than Shorai for long term use especially in cold climates.

[2002Z3]

Remotion, sorry to say I cannot comment on lithium in a Z3, but I do know a little about motorcycles and Li batteries. I did a butt load of research on replacement Li bike batteries early this year . I figure the same minor issues the motorcycle Li batteries have would also apply to cars. Charging was/is apparently not the issue; however, cold power is. Li batteries need to warm up a bit to get "going", so to speak. This is why many sellers of Li batteries for bikes recommend turning on the ignition and headlight(s) for a few minutes (sometimes even longer) to get the battery to start putting out full power. You may notice a similar effect if you have an Li powered electric razor. Mine will start out a little slow and speed up as I use it.

I did not wind up getting an Li battery for my Honda (1100cc Spirit) because it was near 3X the cost of a lead/acid. If I were racing a car or sport bike though and wanted to reduce weight, that extra cost would probably be well worth it.

[Remotion]

I have googled about 15 hours on a topic, and there are many but price range is at the moment really wide.

I have technically new lead/acid on mine but I want to change. What z3papa said about effect is reassuring and that's what I am going after. I drove my car with hatch net (~16kg) and rear compartment separating panels removed and effect was imminent. With battery change I will get that and additionally the weight of my amp (2.4kg) and sub boxes (4kg each) away.

I wont drive the car at the winter, or if I did I could anyway always switch the lead/acid back just to give some traction for the rear axel.

- - - Updated - - -

How about this for example:
http://store.starkpower.com/12V27Ah-...ER-_p_56.html#

I read from multiple sources that one could use smaller Ah rating than in conventional battery, because lithium will give all it's energy at same voltage, where as in lead acid it starts to drop immediately from full.

[Zandr]

The Starkpower batteries are interesting. That's some spectacular power density, and the best BMS implementation I've read about. It's not clear that Shorai actually has cell balancing except with the off-board charger, for example.
The effect on weight distribution is interesting, though. There aren't too many ways to take 20kg out of a car that easily, but the moving the battery is an easy trick for engineers to balance the car. By removing that bit of ballast, we're going to be moving the CG forward. Not exactly desirable in a car as tail happy as the Coupe.

[Remotion]

Well, I dont mind that, and I already have that much removed from another side by having Eisenmann and stuff..

- - - Updated - - -

These look like a solid too: http://www.lithiumion-batteries.com/products/12v-20ah-lithium-ion-battery/

[mpire]

I have wasted large amounts of money on fancy batteries.

Its all just that, a large waste of money.

I got a beautiful Braille battery that died after 2 years of mostly storage.

I would get the cheapest battery you can find, preferably at the Autozone or whatever is on your route home from work.

Then make a Xerox copy of the receipt so you can read it (heat transfer printed reciepts) when the battery fails and you take it back for warranty replacement.

Lithium batteries are great for track cars, but way too expensive for a garage queen or DD.

If you are looking to save weight, swap out your stock exhaust. That will save you 50 lbs right there.

[djb2]

There is some BS on the Stark battery web page.

They state that the max discharge rate is 30C, and that the battery can output 900 amps. That suggests that the battery is at least 30Ah.

On the same chart as the 900A rating, they state that the battery weight is 1.596Kg. They confirm that weight as 3.51 lbs.
But a single 30Ah LiFePO cell weighs that much, and you need four cells to get 12V-14V. So the battery must be actually be at least 6.5Kg / 14 lbs. So not as big of a weight savings as you expect.

Plus you aren't getting the same reserve capacity. Our batteries are about 60 Ah, not 30 Ah.

A LiFePO battery needs both over-charge and over-discharge protection. A cell is permanently damaged when fully discharged, and is likely to ignite when overcharged (or even with a normal charge if it has been over-discharged), so you never want either to happen. Once you have discharge protection (modern MOSFETs are amazing -- it takes only two or three in parallel to carry 900A!), you can trivially reserve a little extra capacity for a single start attempt.

It's not clear that the Stark batteries have true over-charge protection. That would require a second set of MOSFETs. My guess is that they just switch off the main MOSFETs when the voltage is too high, counting on the voltage drop of the intrinsic diodes to provide a little protection for the batteries. That will work fine, until there is a real voltage regulator failure.

[Remotion]

Apparently post I just wrote got deleted somehow. so:

I would get the cheapest battery you can find, preferably at the Autozone or whatever is on your route home from work.

I have already that, under 2 years old cheap battery so no I wont.

Lithium batteries are great for track cars, but way too expensive for a garage queen or DD.

No they are not anymore, hence this thread.

If you are looking to save weight, swap out your stock exhaust. That will save you 50 lbs right there.

Schmiedmann -> Magnaflow -> Eisenmann allready. Actually my pipe is so light that when I hop off the car it raises it's rear corner because only battery side has weight.

- - - Updated - - -

There is some BS on the Stark battery web page.

They state that the max discharge rate is 30C, and that the battery can output 900 amps. That suggests that the battery is at least 30Ah.

On the same chart as the 900A rating, they state that the battery weight is 1.596Kg. They confirm that weight as 3.51 lbs.
But a single 30Ah LiFePO cell weighs that much, and you need four cells to get 12V-14V. So the battery must be actually be at least 6.5Kg / 14 lbs. So not as big of a weight savings as you expect.

Plus you aren't getting the same reserve capacity. Our batteries are about 60 Ah, not 30 Ah.

A LiFePO battery needs both over-charge and over-discharge protection. A cell is permanently damaged when fully discharged, and is likely to ignite when overcharged (or even with a normal charge if it has been over-discharged), so you never want either to happen. Once you have discharge protection (modern MOSFETs are amazing -- it takes only two or three in parallel to carry 900A!), you can trivially reserve a little extra capacity for a single start attempt.

It's not clear that the Stark batteries have true over-charge protection. That would require a second set of MOSFETs. My guess is that they just switch off the main MOSFETs when the voltage is too high, counting on the voltage drop of the intrinsic diodes to provide a little protection for the batteries. That will work fine, until there is a real voltage regulator failure.

Well there are lot of thing you would of had not written if you had read above posts.

[Zandr]

So, has anyone gone for it yet? Having needed to use my (Lithium Ion!) booster pack to start the car this morning, it's time for a new battery.

I think I'm going Stark based on this thread.

[BenFenner]

There was a recent MotoIQ article on the Pegasus brand. The specs and tech looked great, but it's not clear how modern the charging circuitry is for the battery, since they claim to charge it you'll need their special charger?
If it has as good charging circuitry as anything else, the benefits sound nice.

http://www.motoiq.com/MagazineArticl...g-Battery.aspx

[mpire]

I have already that, under 2 years old cheap battery so no I wont.

Well, I went and bought that fancy Braille battery and it died on me after less than 2 years. You have to have a special charger for an AGM battery, a regular battery tender or charger will kill it. Funny thing is that the AGM battery that you can get at Discount Auto for $175 ($50 online coupon, so order online and pick up in store for $125) looks to be the exact same plastic extrusion as the Braille battery. They are probably just re-branded batteries from the same factory.

I have gone back to regular old lead acid batteries in the coupes that just sit, and have an AGM in the DD.

No they are not anymore, hence this thread.

Well, let us know how it works out for you. I would be rather concerned that you have a LI battery down in the well between the exhausts. I know they are heat sensitive, but I would do some research. I would like to know how long it lasts. If you relocate it, then post pictures!

Schmiedmann -> Magnaflow -> Eisenmann allready. Actually my pipe is so light that when I hop off the car it raises it's rear corner because only battery side has weight.

Huh? Is your battery not in the middle of the exhausts? Is this a Z3 or an M?

[BimmerBreaker]

His car is a 2.8 Z3 Coupe

[JWin]

My car has a regular ol' interstate that was the deal a few years ago: http://www.interstatebatteries.com/p...432-2147384906

Saves 20 pounds over stock and doesn't mind sitting for weeks at a time.

Also, perfect fit and placement of drain tube.

[Zandr]

Ordered the 36Ah Starkpower... will advise.

Edit: Ben- the Pegasus battery with the internal BMS is about twice the cost of the Starkpower for a bit more than half the capacity. The Starkpower is also LiFePO4, so I think it has most of the other advantages of the Pegasus.

[BenFenner]

Zandr, thank you for doing the research and reporting back.