SL55 AMG, SL63 AMG, SL65 AMG (R230) 2002 - 2011 (2003 US for SL55 and 2004 for the SL65)

SL55/63/65/R230 AMG: Onboard battery maintainer for both batteries

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Old Jul 18, 2019 | 01:18 PM
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Michael Pitts's Avatar
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2005 SL65 AMG
Onboard battery maintainer for both batteries

I plan to install a NOCO Genius GENM2 8 Amp 2-Bank On-Board Battery Charger in my 2005 SL65.

Has as anyone else done this? If so, wondering where you mounted the unit and how you ran the wires. The leads to the batteries are 6 feet long, so I am thinking the unit should be central, perhaps under the passenger seat or in the cubby behind the seat.
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Old Jul 19, 2019 | 10:32 AM
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Not sure about the product you have acquired, but I assume this is a type of plug-in battery charger/tender.

The SLs have a rear convenience batter and front starter batter that are maintained through a battery control module located in the trunk near the convenience battery. You should most likely locate your battery tender in this location as you will only want to keep the convenience battery charged up. The battery control module makes sure that any convenience features (those not needed to start the car) come from the convenience battery.
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Old Jul 19, 2019 | 11:35 AM
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Thanks for the reply. I do already keep the systems battery in the trunk charged with a portable smart charger. But the car may sit for weeks at a time and I’m concerned this could allow the starter battery to become weak. I stumbled across this on Amazon and it seems like a great way to keep both batteries charged.

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Old Jul 19, 2019 | 12:02 PM
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'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55
Originally Posted by Michael Pitts
But the car may sit for weeks at a time and I’m concerned this could allow the starter battery to become weak.
You needn't be concerned, since no significant current is drawn from the starter battery while the vehicle is idle.
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Old Jul 19, 2019 | 12:33 PM
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SL65 AMG
My SL65 sits for months at a time as I travel a good amount and leave a tender on the trunk battery and have never had issues. The front battery doesn't need it.
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Old Jul 21, 2019 | 01:46 PM
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My '03 SL55 is stored for 3-4 months every winter. I have the smart maintainer on the rear battery. I disconnect it for 2-3 days about every 2-3 weeks. The starting battery under the hood is fully charged every spring when I start the car. I think the NOCO system is way overkill!!

Gary
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Old Jul 22, 2019 | 01:19 PM
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Originally Posted by kittyandgary
My '03 SL55 is stored for 3-4 months every winter. I have the smart maintainer on the rear battery. I disconnect it for 2-3 days about every 2-3 weeks. The starting battery under the hood is fully charged every spring when I start the car. I think the NOCO system is way overkill!!

Gary

+1 - never had an issue with starter battery on my 2007 SL55
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