06 E320 CDI 'Low Battery' Display discrepancy? - PeachParts Mercedes-Benz Forum

jcyuhn · #1 08-14-2013, 10:07 AM

Quote:

Originally Posted by hookedon210s

Replace the aux battery first---it's at least 7 years old. Very doubtful that the aux battery relay is bad. Once installed start vehicle and check voltage at aux battery. It should be about 14V which would indicate that the aux battery relay is good. Note that it may take a few cycles of driving the vehicle for 15 minutes at a time to clear the low battery message---15 minutes being the approximate time the aux battery relay will permit the aux battery to charge per operating cycle. Mark

Good input. I trickle charged the new battery @2 amps for perhaps 3 hours before installing it in the car. While that is no more than a 50% charge, it was enough that I never saw the red battery warning message again.

Skid Row Joe · #2 08-15-2013, 04:20 PM

Quote:

Originally Posted by hookedon210s

Remember, the cables to the aux battery are hot all the time unless you disconnect the main battery. I just wrap the positive aux battery cable in a heavy kitchen towel when replacing the aux battery to prevent shorting the cable to ground and taking out the aux battery relay ($$$) or worse. As JC said, the aux battery needs to be filled with the included electrolyte, permitted to stand per the instructions, sealed and then charged before installation. Really not very difficult to replace, you can get the battery from McParts for about $100 and MB gets about $300 for the job. Mark

Quote:

Originally Posted by jcyuhn

If you get a red battery display immediately upon starting the car, but no additional error messages, then you need a new auxiliary battery. The aux battery is located under the hood, underneath the cabin air filter. The aux battery supplies backup power to the SBC brakes in the even of a fault with the main battery. It was supposedly deleted on later 211 models when the SBC was replaced with conventional brakes.

The aux battery is a standard powersports (motorcycle, etc.) size AGM battery. Different manufacturers use different terminology, but it's a GTX-14BS or equivalent. It is readily available at McParts stores such as Pep Boys, Wally-Mart, and AutoZoo. Do be aware the batteries are shipped dry; you have to add the acid, let it absorb into the AGM, then seal and charge the battery before installation.

If the main trunk mounted battery is low, the car will either not start (duh) or will give an error message to the effect that electrical consumers have been disabled. Your heated seats will be disabled and your blower fan will be restricted to low speeds. When the battery reaches a sufficient level of charge, all the toys will be enabled. I have seen this message after letting the car sit for an extended period of time, such as when traveling overseas on business.

Cheers,

- JimY

Quote:

Originally Posted by hookedon210s

Replace the aux battery first---it's at least 7 years old. Very doubtful that the aux battery relay is bad. Once installed start vehicle and check voltage at aux battery. It should be about 14V which would indicate that the aux battery relay is good. Note that it may take a few cycles of driving the vehicle for 15 minutes at a time to clear the low battery message---15 minutes being the approximate time the aux battery relay will permit the aux battery to charge per operating cycle. Mark

Quote:

Originally Posted by jcyuhn

Good input. I trickle charged the new battery @2 amps for perhaps 3 hours before installing it in the car. While that is no more than a 50% charge, it was enough that I never saw the red battery warning message again.

OK, so, I have a couple more Qs.

I am thinking that I'd prefer the sealed top battery - which is different than what hookedon is describing.

If I put the sealed top battery in, do I still trickle it, jcyuhn?

MB dealer wants $119.00 for it @ my MBCA member price - and it looks like I can get an AutoZone sealed battery - the motorcycle one for $80 - $85. Problem is, AZ doesn't show a part number / application for an auxiliary battery for the 06 CDI.

I see the style number you wrote above, jcyuhn. It that a good number @ AutoZone?

From YouTube, I got this HM Honda MC part #31500-HC4-726AH for: $102.59

I suppose I need cross-reference numbers at this point.

Is it worth it to just go with the MB dealer's battery? Downside the MB dealer is a 36 mile roundtrip ride. So, I thought I'd go AZ or Interstate, IF I can get a proper application part number.......

hookedon210s · #3 08-15-2013, 04:42 PM

You don't need the dealer battery. Both the dealership and motorcycle battery are AGM batteries---so called Absorbed Glass Mat batteries. Both batteries are "unsealed" when you purchase them because they are dry, i.e. without electrolyte. You activate the battery by adding the electrolyte that comes with the battery which is absorbed by fiberglass mat separators, letting it off-gas for a bit as stated in the instructions and then installing the non-removable caps which makes it a sealed battery. Once absorbed, the electrolyte will neither spill nor evaporate unless overcharged. Since the on board charging system will only charge the aux battery in 15+- minute cycles MB says you must charge the battery after activation. I assume the system would eventually charge the battery but why stress the $$$ MB system (aux battery relay) in lieu of using a cheap trickle charger? Just my $.02. Mark

jcyuhn · #4 08-15-2013, 04:54 PM

Hi SRJ -

I can clarify. Don & I are describing the same thing. The batteries are shipped dry. You add the acid (it's easy), let it absorb, and then seal the battery. It is a sealed, maintenance free battery from that point forward.

GTX-14BS is a good number. Many manufacturers sell under that number, others cross reference to it. At any rate, you need an AGM battery that is 5.875x3.375x5.6875 inches. Go buy it at autozone. Take it out of the box and compare it to the one in the car, make sure they are the same physical size. If all is good, add the acid and pop it in the car.

No need to go to the dealer, they are selling the same thing. For the extra 30 bucks they will add the acid for you, that's all.

Trickle charging it is optional. The car will charge it for you, but you'll get the red warning at start until it is sufficiently charged. May take a few start cycles.

Skid Row Joe · #5 08-15-2013, 05:02 PM

10/4 I'm stoked with ya'll's info!