roosevelthuntjr

I just installed, 2 Diamond D3 Subs in a slot ported box, powered by a D1000.1 amp 1100 watts mono, and a 2 farad capacitor. The Diamond Speakers say 4ohms on them. The problem I'm having is when I listen to my radio for like 10 min or so, I get a message on my dash "Low Battery, Convenience Features disabled" and the subs cut out.
My system was installed by Best Buy, (don't laugh as I was fully ready to pay the stealer-ship whatever it cost to do this but they absolutely wouldn't). The guy at Best Buy couldn't figure what the hell was going on. I called dealership and looked at my manual and the only thing we can figure is when the battery in the trunk gets low, the one under the air filter takes over and the power for the amp is cut off completely. Which doesn't make sense because the aux battery under the hood is supposed to be for the SBC Breaking system.
They tapped into the sub wires on the rear deck to power the amp. I've had no battery issues until this amp install. Am I missing something here, do I need to purchase a new battery? Do I need to pay hundreds for the only pro installer in my town to wire up a simple amp and sub box. Any thoughts would be appreciated! Thanks in advance! 2005 E320 sedan.

Skylaw

I don't deal much with audio system upgrades, but from your description you may need a larger alternator. It would seem that the drain you have placed on the battery exceeds the alternator's ability to charge it.

jaedee

My suggestion would be to measure current draw and voltage loss (at the battery) while your stereo is off and again with it on. I would also measure alternator output to make sure that as skylaw said, your alternator is not able to keep up with the demands. Comparing the information can indicate if you possibly have a weak battery or alternator to begin with and maybe the current being drawn from the amp is just too much for them handle in their current state. If your battery/alternator are 5 years old since you have an 05 vehicle) it could simply mean that it is time to replace your battery and alternator. Hope that helps.

rob13572468

This is actually a common problem with the W211 E class... The issue is that there is a module at the rear battery that monitors voltage and current draw and protects the system aginst having a high current draw. The problem is that when you play dynamic music the amplifier pulls enough power to drop the voltage momentarily enough to send the car into protect mode.

You are going to need to pull the wiring for the current measuring module and regulate the the sense wire so that it always sees ~13 volts

jwhbud

Rob, is there anyway you could tell me exactly how to regulate the module? I'm having this exact problem. The battery and alternator are both good so I'm guessing that what you said is my issue. My car audio guy said he would take care of it but needs some more info. Any help would be much appreciated. Thanks.

rob13572468

pin 14 on the module is the sense lead for the main battery... you would want to diode isolate that lead just before the module with a 5A diode and then put a small stiffening cap (1/10 Farad) between pin 14 and ground but after the diode. e.g. the diode keeps the amp from pulling that line low when the bass hits and the cap keeps the voltage up.

rob13572468

also the aux battery sense is at pin 7 (in the same 14 pin connector) you can do the same for that one although it shouldnt be the one that needs it.

jwhbud

Where exactly is the module located? I kinda remember seeing a small black box mounted at the very rear of the trunk but I'm not positive that's it. The way my car audio system is set up makes it hard to see, so before we start taking it all back out of the trunk I wanted to double check. Thanks for the help by the way!

jwhbud

Is there anyone else out there that may be able to tell me the location of the module? My car audio guy won't touch it until he knows for sure what he's messing with.
Thanks!

rob13572468

you cant miss it.. its the box 6 inches to the right of the battery in the wheel well... the two are connected with a big 2 gauge cable.

jwhbud

Thanks a lot Rob, I really appreciate the help. I'll pass this info on to the installer and hopefully the problem will be solved.

jwhbud

Well after finally getting the chance to apply the fix it would seem that it wasn't the best solution. The radio no longer shuts off but now I get the "Low Battery, Convenience Features disabled" message all of the time usually when starting the car, which keeps the easy entrance feature from working (the auto up and down for the steering wheel). I did however just put a brand new battery in at the same time so I guess there is the slight chance that it has issues.

jwhbud

Another question for you Rob, all I had access to was a 6A diode instead of the 5A diode will that make a difference? The electronics store I went too wanted to know voltage and or wattage of the diode they said I wasn't giving them enough information. And also is 100mf the same as a 1/10 capacitor? Again, thanks for the help.

rob13572468

100 mf is sometimes confused with 100 uF or 100 microfarad which is 100/1,000,000 or 1/10000 so thats too small... as long as it says mF and not uF its fine.. The 6A diode is fine... bigger is ok.

Finally keep in mind that there may be a bit of difference in the values needed for your particular setup. The values i gave worked for a system that i did but yours may pull more current or faster and may require a higher capacitance. The ideal way to do this is to actually put a scope on that sense line so that you can watch it as the music is playing.. The idea is to keep the voltage stable on the line.

Finally you can also try just using the capacitor on the line without the diode.. One issue with the diode is that all diodes have a voltage drop anywhere from 0.7 to 1.5 volts and if the the voltage is dropped too low it can result in the message being present as well.. You ideally want to use a diode with as low as forward voltage drop as possible (0.7v) but if the capacitor works well enough the line may be stable without the diode at all so give that a try...

pinebaron

Ideally you should use a Schottky diode.

jwhbud

Well after a couple weeks of testing I finally think everything is good to go. I did do what Rob suggested and removed the diode, leaving just the cap, nothing cuts off anymore and no error codes on the dash.