Anyone installed 2nd battery?
03-13-2014, 03:59 PM
#1
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c230k
Anyone installed 2nd battery?
I'm wondering if anyone has every installed a 2nd battery in the trunk of the w203. I have a bigger audio system in my car and also use my car to power my laptop while away on trips and was thinking about installing an isolated 2nd deep cycle battery to charge things off of.
In theory it should work with a battery isolator, but I know these cars are very picky when to comes to electronics.
Any input would be appreciated.
Thanks,
Tim
In theory it should work with a battery isolator, but I know these cars are very picky when to comes to electronics.
Any input would be appreciated.
Thanks,
Tim
03-13-2014, 04:25 PM
#2
Out Of Control!!
With a good isolator you should have no problems.
Separate the two batteries when you are parked with the engine off.
A Diode isolator will tend to undercharge the second battery. Some use two diodes to isolate both batteries. These work well if the charging system (voltage regulator) can be wired to sense the voltage after the diode. (Runs alt 0.2 to 0.7 volts higher and the batteries receives normal voltage)
This usually is only possible with commercial/RV wiring systems.
One way to go is a diode isolator that has a bypass relay. the second battery charges through an isolation diode, but when the car is running (delayed some period after start) a relay shunts the diode providing full charging voltage to the second battery.
Separate the two batteries when you are parked with the engine off.
A Diode isolator will tend to undercharge the second battery. Some use two diodes to isolate both batteries. These work well if the charging system (voltage regulator) can be wired to sense the voltage after the diode. (Runs alt 0.2 to 0.7 volts higher and the batteries receives normal voltage)
This usually is only possible with commercial/RV wiring systems.
One way to go is a diode isolator that has a bypass relay. the second battery charges through an isolation diode, but when the car is running (delayed some period after start) a relay shunts the diode providing full charging voltage to the second battery.
03-13-2014, 08:18 PM
#3
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Make sure you use the same type of battery as you have up front under the hood. Regular and AGM have different charging requirements.
A regular lead acid up front and a deep cycle lead acid in back is fine. But don't put an AGM in the rear if you have regular lead acid up front
A regular lead acid up front and a deep cycle lead acid in back is fine. But don't put an AGM in the rear if you have regular lead acid up front
03-13-2014, 11:13 PM
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2005 C Wagon (No snickering please!)
If you drive your car whilst using the audio system and laptop a second battery will do nothing for you. There is enough headroom in the factory battery to do the job.
Some Mercedes cars do have a second battery, but the charging, isolation, and suppression circuits are no simple piece of kit. Diode isolators are useful for off-road vehicles with relatively low number of consumers onboard. They primarily allow the starter battery to be protected from discharge while the engine is stopped and the electric system is used for lighting or a Margarita blender.
A second battery running with a typical isolator will expose several expensive system modules to transients they cannot withstand.
I suggest you forgo a second battery and buy spare batteries for your laptop and listen to music on your phone when the engine is stopped.
Some Mercedes cars do have a second battery, but the charging, isolation, and suppression circuits are no simple piece of kit. Diode isolators are useful for off-road vehicles with relatively low number of consumers onboard. They primarily allow the starter battery to be protected from discharge while the engine is stopped and the electric system is used for lighting or a Margarita blender.
A second battery running with a typical isolator will expose several expensive system modules to transients they cannot withstand.
I suggest you forgo a second battery and buy spare batteries for your laptop and listen to music on your phone when the engine is stopped.
03-14-2014, 10:41 AM
#6
Out Of Control!!
Don't concern yourself over how MB does their second battery. It does not make any difference to what you want to do.
I a not sure why a good isolator would subject he car to any "transients".
There are lots of good discussions on the pros and cons of different systems on the RV forums. It is worth the time to read.
Seems our MBs have plenty big alternators to charge the second battery as long as you don't let it go flat.
I a not sure why a good isolator would subject he car to any "transients".
There are lots of good discussions on the pros and cons of different systems on the RV forums. It is worth the time to read.
Seems our MBs have plenty big alternators to charge the second battery as long as you don't let it go flat.
