The Big 3 Mod

[Cattivo]

Our E70 X5's are known for their weak battery and quick discharge if not started every couple days. I've been doing some research from other car forums who also are having issues with the car/truck battery.

I just picked up all the material for The big 3 mod...The "big 3" upgrade is a common mod done by others... It involves upgrading the size and quality of wire for the battery and alternator. This mod will provide better current flow which can affect many aspects of your vehicle (i.e. less voltage drop, no dimming lights, even better mileage, etc...)

There has been some debate on whether or not to fuse the lead from the battery to the alternator... I chose to have the extra insurance and bought a 200amp waterproof ANL fuse.

For parts, I ordered my supplies from knukonceptz.com. Most go with 1/0 gauge wire...you can even use welding cable.

Easiest way to install everything is follow the paths of the factory cable and finish everything off with wire loom.

On the (-) side:
Battery to chassis
Battery to block

On the (+) side:
Battery to alternator

[mitch808]

The Big 3 is not new, but more prevelant with today's cars and their increased power draw. Often someone with a large aftermarket stereo installs this "mod," to prevent flickering lights during big bass notes. *Capacitors are a crutch not a solution!*

I am not sure it's going to do much for us, then again, no one has really tried it and documented it.

[protecon]

Originally Posted by Cattivo

Our E70 X5's are known for their weak battery and quick discharge if not started every couple days. I've been doing some research from other car forums who also are having issues with the car/truck battery.

Are you having issues with your battery?
Wouldn't it be easier/cheaper to stick a small solar charger on the back window?

[Cattivo]

Originally Posted by mitch808

The Big 3 is not new, but more prevelant with today's cars and their increased power draw. Often someone with a large aftermarket stereo installs this "mod," to prevent flickering lights during big bass notes. *Capacitors are a crutch not a solution!*

I am not sure it's going to do much for us, then again, no one has really tried it and documented it.

I wanted to give it a try on my 50i, I noticed if I don't start it for a couple days during extremely cold temperatures the i-drive throws battery discharge warnings and drives very sluggish until it reaches operating temp.

I don't have an aftermarket stereo and have recently replaced the battery including the IBS cable all registered by Carley...I'm going to give it a try for shits and giggles, can't hurt

[Thecastle]

Bigger gauge wiring helps with large current draw, if you run high power devices. But it won't fix the problem with your increased discharge warning. The issue isn't a wiring one, its limitation of the type of battery we use, and the large power draw of the car when it's off. You'd be better off using a battery charger to desulfste the battery and charge it properly. You can't increase the battery charging rate by increasing the battery cable size, the maximum charge rate is a limitation of battery chemistry, type and temperature in exchange for life.

automotive batteries that were designed for high current quick discharge to start a car. We really need a deep discharge battery or marine battery to better handle the constant load these cars place on the battery especially post shutdown. Using a car batttery in a deep discharge role is a recipe for short battery life and a quick reduction in capacity and hence warnings for increased discharge aka low battery.

There is a limit on how fast you can charge a battery as well. The faster the charging the hotter they get, which increases degradation of the battery and evaporation of the electrolytes which also reduces capacity. Basically you can't charge it faster than about 10ahr without degrading capacity and life span. So putting a bigger cable in won't help with charging the battery more quickly as the real charging limit is the battery itself and it's internal,design. The car automatically limits charging voltage and current to optimize battery life. A 3 gauge cable just isn't necessary for optimal battery life.

Car batteries are very poor at handling a deep discharge and are easily damaged (reduced capacity) when discharged below 50% of their capacity which probably happens frequently with the v8s. They can only handle this kind of discharge a few hundred times (200ish) before they fail.

Anyway my x5 has a 92ah AGM battery, which at 12v is only 1100 watts. Which really isn't very much power and the amp hour rating is for a 20 hour draw. Especially when your talking about running fans, water pumps, electronics, etc, for a considerable amount of time after shutdown. It wouldn't surprise me if shutdown cooling dosent consume 20-30ahr. Electric motors draw a lot of current,

I have a lot of experience with batteries from modding rvs for off grid use. Batteries are complicated and fickel beasts, and it's no,surprise such small batteries are struggling with big power draws and deep discharges and have a short life.

[boneca]

good luck bro and let us know how it went, maybe DIY as well?
I had my car in the garage for 3 month and only started it maybe 4 times all this time, I took it out for a spin once, finally when I got to it this weekend my battery was almost dead but not completely, I connected charger for 24 hours and discharged went away. I still considering replacing the battery soon as I believe its original one!

[Torgus]

Originally Posted by Thecastle

Bigger gauge wiring helps with large current draw, if you run high power devices. But it won't fix the problem with your increased discharge warning. The issue isn't a wiring one, its limitation of the type of battery we use, and the large power draw of the car when it's off. You'd be better off using a battery charger to desulfste the battery and charge it properly. You can't increase the battery charging rate by increasing the battery cable size, the maximum charge rate is a limitation of battery chemistry, type and temperature in exchange for life.

automotive batteries that were designed for high current quick discharge to start a car. We really need a deep discharge battery or marine battery to better handle the constant load these cars place on the battery especially post shutdown. Using a car batttery in a deep discharge role is a recipe for short battery life and a quick reduction in capacity and hence warnings for increased discharge aka low battery.

There is a limit on how fast you can charge a battery as well. The faster the charging the hotter they get, which increases degradation of the battery and evaporation of the electrolytes which also reduces capacity. Basically you can't charge it faster than about 10ahr without degrading capacity and life span. So putting a bigger cable in won't help with charging the battery more quickly as the real charging limit is the battery itself and it's internal,design. The car automatically limits charging voltage and current to optimize battery life. A 3 gauge cable just isn't necessary for optimal battery life.

Car batteries are very poor at handling a deep discharge and are easily damaged (reduced capacity) when discharged below 50% of their capacity which probably happens frequently with the v8s. They can only handle this kind of discharge a few hundred times (200ish) before they fail.

Anyway my x5 has a 92ah AGM battery, which at 12v is only 1100 watts. Which really isn't very much power and the amp hour rating is for a 20 hour draw. Especially when your talking about running fans, water pumps, electronics, etc, for a considerable amount of time after shutdown. It wouldn't surprise me if shutdown cooling dosent consume 20-30ahr. Electric motors draw a lot of current,

I have a lot of experience with batteries from modding rvs for off grid use. Batteries are complicated and fickel beasts, and it's no,surprise such small batteries are struggling with big power draws and deep discharges and have a short life.

This.

The Big 3 isn't going to hurt but it isn't going to help your discharge issue. It is good you fused the wire. Only idiots on car audio forums don't fuse to save money. The fuse protects the wire.

My suggestion would be to buy the largest deep discharge you can fit. Just make sure the CCA is high enough, which they should be if you get a monster DD. I've done this on other vehicles and never had a problem. Large DD are expensive and heavy for what it's worth.

Or, hook it up to a charger.

[Cattivo]

I'll try it out this weekend and see if there are any changes if anyone is interested

[Torgus]

Originally Posted by Cattivo

I'll try it out this weekend and see if there are any changes if anyone is interested

Please do, It's mainly done for car audio systems. On some cars the grounds are weak from the get go or corrode over time so it can 'help' the system. It certainly is not going to hurt.

It would be great if you did a step by step with pics. I have a bunch of 1/0 and connectors lying around. But I don't think I will do a stereo system on this car...

[007_e350]

a little irrelevant but maybe not.. I had an e-class back in the day and it was going through a battery every 3 months - dealership couldn't figure the cause and kept insisting bad battery etc etc
I hooked up an ammeter to the positive terminal of the battery and closed the trunk latch while truck was open - locked the car, waited till everything shutoff (15 mins) - and observed the amperage withdrawl .. It used to wake up once every 30 mins and draw 3 amps and go back to 0 ... I started removing fuses to see whats the culprit but couldnt pin it down, eventually traded the car ........... now I've found out there's a TSB in w211 E-Classes about SAM module (signal actuator module) that malfunctions and draws current while the car is turned off .. I'm like get the ef outta here MB I lost a beautiful car because the stealership couldn't diagnose and kept charging us enormous amounts of money with inconclusive diagnosis