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      05-16-2009, 05:56 PM   #65
Cleveland
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Drives: M3 coupe
Join Date: Apr 2009
Location: Louisiana

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Quote:
Originally Posted by lucid View Post
Cleveland, it sounds like you had an alarm system that was drawing significant current. I don't have an alarm system (I don't know if Swamp or Doba does). In my car, the only possible significant load on the system is CA when the ignition is off (unless the car is performing "significant" functions that I am not aware of when parked; it probably is not completely silent). So, your comparison is off, and how much current CA will draw is unknown at this point.

The specific battery under consideration does have the required cranking amps (per specification).

The specs state that it will last 3100 charging cycles at 10% DOD. It seems like what we need to know is how much of a load CA constitutes exactly, and if that exceeds 10% DOD when the car is parked for a couple of days or not driven enough for a full charge cycle.

With regards to the potential "charging too slowly while driving issue", Braille specifies "daily driving" as a suitable application for this product:

http://www.braillebattery.com/index....s/b3121/specs#

I know every car model car is different, but they should have a good idea of how long it takes a nominal car to charge a 10% discharged battery since they specificed "daily driving" as an application.

A test would be for someone to disconnect the battery terminal every night for a couple of weeks to see if that makes a difference (or log the current when parked overnight), but I'm sure the disconnects will be logged in the computer.
Make sure you don't fall in love with those specs too much...you may be disappointed later on.

The power output of these batteries can be tweaked to a point, but SIZE rules when it comes to making really substantial power in automotive batteries. I love advanced technological breakthrough as much as the next guy but you have to be realistic here. A larger battery case will hold more LEAD plates and a larger volume of ACID. That's what drives the battery power output.

Yes, you can squeeze a few more amp hours, cranking amps, and reserve minutes out of some AGM batteries by using some innovative techniques, but you are still limited to what you can ultimately cram into that small battery case.

Don't fool yourself into believing this battery is the holy grail or something. It's not. It's a good, solid, small form factor, lightweight racing battery. Nothing more...nothing less. That's how i got myself into trouble. I had convinced myself, that these racing batteries were something they were not.

And I got bitchslaped back into reality a few times before I sobered up and stopped drinking the kool-aid...

I suspect you are starting to realize this yourself?

In regards to your quote from the braille website about the charging of these racing batteries...

They ALL recommended daily driving...because that's basically a requirement of ownership. (another thing I found out the hard way)

What they don't tell you is...abosorbed glass mat (AGM) batteries are not very compatible with current automotive charging systems. That's why they recommend that you drive the car around everyday. The CHARGING RATE for that type of battery is slower than that of a conventional wet cell LEAD-ACID battery. (OEM)

Modern alternators are not designed to deal with charging AGM batteries. I'm not saying they CAN'T charge them, they can...although at a reduced rate. The efficiency is reduced, and the alternator has to work harder to charged it back to 100%.

You could do this, but it's not very PRACTICAL though. I know I can't drive my car everyday due to where I work, and my occasional out-of-town business trips.

Every one of the small racing battery brands I bought over the years, told me it would be fine to leave the car sitting for few days. I seem to remember them telling me something like: "It won't hurt anything"

Well that was a bald faced lie!

The only real way to make sure this mod never comes back to haunt you...

...is to install a battery disconnect switch and use it every day.

Now Lucid, lets be realistic here... who the hell is going to go through all that trouble to make sure they never get burned by leaving the console light on?

At that point, this mod is more trouble than it's worth...

Maybe a small percentage of the people with OCD wouldn't mind, and that's about it.