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Old 07-01-2022, 04:09 PM   #1
Junior Member
Join Date: Jan 2017
Location: Sandpoint, Idaho
Posts: 21
Sprinter Trickle Charger Install

We have a 2018 MB Sprinter Sportsmobile Van that had a dead starter battery. We are replacing that starter battery. I thought that the house battery would backup the battery; however, since we have two alternators that is not the case. After a conversation with Field Van, they confirmed that the starter battery is isolated from the house batteries. So. We would like to install a onboard trickle charger/maintainer. To charge the old/dead starter battery Mercedes recommended that I disconnect the starter battery before we attach a trickle charger. If this is the case for all charges, it would seem an onboard charger would not be able to be installed?

1. Do you disconnect your battery to use a trickle charger?

2. Could you attach the trickle charger to the jumper locations under the hood? or

3.Can we attach a CTEK MXS 5.0 or other maintainer permanently to the battery, place the maintainer under the swivel driver's seat and run a ac cord to the engine compartment or to the bumper?

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Old 07-02-2022, 10:17 AM   #2
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Location: Vacaville, just east of the San Francisco Bay Area
Posts: 1,012
As you have discovered, the parasitic draw on the starter battery can be a killer. I measured the draw on my 2016 Sprinter at 50 milliamps. Keeping the starter battery charged will extend its life, as evidenced in my case with the original 2016 battery still going strong at almost 80k miles.

I don't have the dual alternator setup that you have, but my original configuration (since changed) with the Sure Power Separator functioned in much the same way in that the two batteries were isolated and the starter battery only saw a charge when the engine was running. See post #617 in my build thread for my initial solution:

I see no reason to disconnect the battery while the trickle charger is connected. I didn't in the configuration shown in my post and everything functioned just fine. Are you aware of the master disconnect under the dash adjacent to the accelerator pedal? Your choice of connection location may be influenced by this, depending on which side of the disconnect you want to connect to. Had I not proceeded down the path of replacing the separator with an ACR (read posts 617 to 643 for the full story) I would have made the connection directly at the battery had I chosen to install a hard-wired solution.

“Flint” - 2016 SMB Sprinter 4x4 144" RB 150S w/ PH
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Old 07-03-2022, 06:02 PM   #3
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Join Date: Jan 2017
Location: Sandpoint, Idaho
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Fitz, thanks for the advice, always helpful. Decided to hard wire eyelet terminals, add a CTEK extension and run wires into bonnet or behind drivers seat where will have a removable CTEK US 7002 (Have cooler weather up here in Sandpoint.)

We have less than 10,000 miles on the vehicle; 3000 miles were picking up the vehicle and a return trip to Fresno to have a leak repaired. Because of Covid and staying around during bad fire seasons, it has sat in the garage for long periods of time. Hoping to put on some miles this fall.

Again, thanks.
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charger, ctek, electrical system

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