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Discussion Starter #1
Hi.

I have '98 BMW E39 520i EUR. I just noticed that after several days of not driving my battery drains dead so I can forget about starting my car. I have 2 amps + 4 speakers + aftermarket HU + 12" sub. Before that I've installed standard (let's say not budget but also not a premium MA) 85Ah battery. It has half a year. Now I connected multimeter to my battery and removed fuses one by one. Nothing beside light related stuff (which were on) influenced the drain. Once car fell into sleep mode my reading was 0,02A. Now this really stumped me. I know it should be 0,005A our something around that but still, it's just 0,02A. Could you give me any tips? Of course I didn't encoutered these problems before installing my audio system. I guess my alternator is too weak to supply the power demand but still I can fire up my engine after one day but after 4-5 days it's impossible. Please help. Thanks in advance.
 

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Hi.

I have '98 BMW E39 520i EUR. I just noticed that after several days of not driving my battery drains dead so I can forget about starting my car. I have 2 amps + 4 speakers + aftermarket HU + 12" sub. Before that I've installed standard (let's say not budget but also not a premium MA) 85Ah battery. It has half a year. Now I connected multimeter to my battery and removed fuses one by one. Nothing beside light related stuff (which were on) influenced the drain. Once car fell into sleep mode my reading was 0,02A. Now this really stumped me. I know it should be 0,005A our something around that but still, it's just 0,02A. Could you give me any tips? Of course I didn't encoutered these problems before installing my audio system. I guess my alternator is too weak to supply the power demand but still I can fire up my engine after one day but after 4-5 days it's impossible. Please help. Thanks in advance.
I suggest having your battery tested, sounds likes its on its last leg if you ask me
 

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I'm not sure this applies to you, but amplifiers with signal sensing turned on, will drain a battery in about that many days.

Since it began at the same time as this sytem, you should place your ammeter in line with your new gear and see if it is in fact the audio system, and find out which part of it is the cause (amps, head unit, etc).
 

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take the car to a shop and get them to check for shorts. if it's in the audio system they'll tell you, if it's a typical german car wiring nightmare, they'll help you out
 

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How is your hu wired is it on permanent live (As in you can listen to it without the keys in the ignition) Or ignition needs to be on ?

I ask because i used to have a Pioneer that was permanent live wired and never had a problem then i got an Alpine wired this the same and it would flatten the battery after 2 days of not using the car..I changed it to ignition live and have never had a problem since....
 

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Possibly your head unit/amp/s are staying on. Hopefully you don't have an electrical nightmare ahead of ya.Goodluck.
 

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I've installed standard (let's say not budget but also not a premium MA) 85Ah battery. ....... I guess my alternator is too weak to supply the power demand but still I can fire up my engine after one day but after 4-5 days it's impossible.
I'm not sure this applies to you, but amplifiers with signal sensing turned on, will drain a battery in about that many days.

Since it began at the same time as this system, you should place your ammeter in line with your new gear and see if it is in fact the audio system, and find out which part of it is the cause (amps, head unit, etc).
Both of these are strong possibilities.
 

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If you let a battery go completly dead (even a brand new one) it will never hold a full charge again.
This. I had a small Optima yellow in my car, 66 ah. I left for Europe and that thing died and stayed dead for 3 weeks. It never lasted more than 4 days after that. All my alarm back up batteries are probably weaker too so they suck more juice while parked.

Got a massive Optima yellow now, two times the reserve capacity and brand new. It starts like a champ whenever, whatever. 85ah is merely adequate.
 

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Discussion Starter #10
I'm not sure this applies to you, but amplifiers with signal sensing turned on, will drain a battery in about that many days.

Since it began at the same time as this sytem, you should place your ammeter in line with your new gear and see if it is in fact the audio system, and find out which part of it is the cause (amps, head unit, etc).
Signal sensing is off. At least on JL Slash 500/1 v2. I also have Rockford T-400 but I guess it doesn't have signal sensing.

How is your hu wired is it on permanent live (As in you can listen to it without the keys in the ignition) Or ignition needs to be on ?
No. I have Alpine CDA-117ri and its not on permanent live. You won't switch it on withouth the key in ignition.

If you let a battery go completly dead (even a brand new one) it will never hold a full charge again.
So if I my battery will go dead even once then it means I have to dump it?
 

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even 0.02amps is a very low drain. Even if your battery has only 90 minute reserve capacity @ 25 amps drain, your current drain is a thousand times lower. I suspect that your battery is either not holding its charge or not being charged properly. I agree that if your battery has been completely drained a few times then it won't hold a full charge anymore. This is typical of standard auto batteries. In order to be able to be fully discharged you need a "deep discharge" type battery used in boats or other applications that don't have a generator. Or the spiral wound gel cell or agm batteries. That technology has been used in alarm systems and batttery back up systems for decades and is has been available for cars for many years.
 

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Discussion Starter #14
So what can I do right now?
 

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Get your charging system checked and/or get a new battery!
Carry booster cables with you!
X2, also do all the standard troubleshooting stuff.

make sure your amplifiers are off. disconnect the fuse on the main power wire to your audio gear and see if the drain goes away.
 
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