Battery Tender Plus
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Newbie
Joined: Mar 2008
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'06 E350, Brabus Springs
Battery Tender Plus
After one and a half months vacation in sunny California this past winter, I came home to find my car's battery totally drained. I boosted it several times and left the car running for half an hour but each time, the battery would not hold charge. Since the car is 8 years old, I thought it was time to replace the main and auxiliary batteries. I called the dealer and was quoted $470 and $150 respectively, not including installation and taxes. Instead of replacing the batteries, I decided to try and charge the main battery using Battery Tender Plus (BTP). The unit cost me $69.99 plus tax. After 36 hours of charging, the BTP is finally showing the battery is charged 80% +. I took the car out for a drive and when I got home, I tried the ignition to be sure. The battery held its charge. To active the BTP, I hooked up the battery on wife's car to the dead battery. The BTP would not start charging otherwise, with a completely dead battery. I think I might have saved myself some big bucks, although I don't know how long the existing batteries will last. This is not a plug for BTP. Just want to let others know of my experience. I am a happy camper right now.
Junior Member
Joined: Feb 2014
Posts: 64
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From: Washington
2001 W210 E430 Sport
You can not just run the vehicle for 30 minuets in the garage to charge the battery, you need to actually drive it. There are so many computers on these cars now a days that if you do not plan to drive the vehicle for 2 weeks, you really need a trickle charger (battery tender) on it.
FYI: The vehicle needs over 8.5 volts (forgot how many amps) for it to start. Your headlights and radio will still work, but not enough juice to start it.
FYI: The vehicle needs over 8.5 volts (forgot how many amps) for it to start. Your headlights and radio will still work, but not enough juice to start it.
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Joined: Aug 2010
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From: Charlotte NC area
2019 WS222 S450 4-Matic / 2007 W211 E350 4Matic (Sold) / 2008 X164 GL320 CDI
If the battery is was not damaged by draining it completely, its life was shortened.
Check the voltage after sitting for 8 hours and see if you have at least near 13.2V
If not the battery is bad.
Check the voltage after sitting for 8 hours and see if you have at least near 13.2V
If not the battery is bad.
Thread Starter
Newbie
Joined: Mar 2008
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'06 E350, Brabus Springs
Good suggestion. Btw, the battery tender now has green light on, which means the battery is completely charged. Very happy I managed to rescue the battery somehow. I thought I could never revive the battery, it being nearly 8 years old and considering the bitter cold winter we've had in the north-east. Curiously, I read some threads earlier saying the battery tender would not charge an AGM battery, but it did in this instance. The OEM battery by the way is a Varta 95Ah.
Out Of Control!!
Joined: Aug 2010
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From: Charlotte NC area
2019 WS222 S450 4-Matic / 2007 W211 E350 4Matic (Sold) / 2008 X164 GL320 CDI
Newer Battery maintainers are usually AGM compatible. (Read the packaging and instructions)
Any charger with charge them, but if it does not have the right float voltage it is not good for the battery long term.
Just because the light turned green does not mean the battery is fully good.
Also, contrary to popular myth, cold weather is good for battery life. (as long as you don't let it freeze.)
Any charger with charge them, but if it does not have the right float voltage it is not good for the battery long term.
Just because the light turned green does not mean the battery is fully good.
Also, contrary to popular myth, cold weather is good for battery life. (as long as you don't let it freeze.)
Super Member
Joined: May 2009
Posts: 673
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From: Frederick
2000 ML320, 2005 E320 CDI
Check reviews for Battery Tender brand. Many many negative reviews. I went with a Yuasa? Brand after days of searching for reviews. Never an issue. I actually need another because my Father uses mine on his truck too often. They are cheap. Found mine on Amazon.
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Out Of Control!!
Joined: Aug 2010
Posts: 12,516
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From: Charlotte NC area
2019 WS222 S450 4-Matic / 2007 W211 E350 4Matic (Sold) / 2008 X164 GL320 CDI
I have a Craftsman/Diehard and a Bosch C3.
Both are microprocessor controlled and designed for AGM batteries.
Both try to charge and show as good a battery that has a cell that is failing.
Both correctly identify as bad a battery with a fully failed cell.
Both are microprocessor controlled and designed for AGM batteries.
Both try to charge and show as good a battery that has a cell that is failing.
Both correctly identify as bad a battery with a fully failed cell.
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84 300d 2009 e320 bluetec (retired)/, now 2012 E350 4-matic blueefficiency automatic
I see the main issue of battery charger used while the battery is on a modern car is over voltage (>14.8V) and blowing out one of the boards. Many desulfation programs goes over 16V and should only be used if the battery is off the car. Some recommend to charge at 14.2 to 14.4 V for AGM type batteries/ lower for sealed gel batteries. After a long drive (60 miles), the voltage at the battery is 14.30V at 1500 rpm and 14.25V at 700 rpm with a 1.5 year 95 AH AGM battery.
Last edited by dave2001auto; Mar 21, 2014 at 04:53 PM.
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Joined: Sep 2014
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From: NOVA/DC
20' RCF, 18' NX, 09' E350, 07' Solara, 05' STi, 01' Ranger
So I have to ask about battery tender since the battery in our car is in the trunk...
All our vehicles that are in the garage are hooked up to a battery tender, which is no problem because the batteries are under the hood, there for I can leave the hood popped but not open and run the wire through... being that our e350 has the battery in the trunk what is the best way to route a wire so that I don't have to have the trunk fully opened all the time in the garage? IE: Having the trunk open will be impossible if and when I get a car cover for the car.
Is there a spot to jump from at the front of the car that I can attach the points to via the battery tender? Just seems like the battery in the trunk is a total PITA.
Thanks,
-Nigel
All our vehicles that are in the garage are hooked up to a battery tender, which is no problem because the batteries are under the hood, there for I can leave the hood popped but not open and run the wire through... being that our e350 has the battery in the trunk what is the best way to route a wire so that I don't have to have the trunk fully opened all the time in the garage? IE: Having the trunk open will be impossible if and when I get a car cover for the car.
Is there a spot to jump from at the front of the car that I can attach the points to via the battery tender? Just seems like the battery in the trunk is a total PITA.
Thanks,
-Nigel
Super Member
Joined: Sep 2014
Posts: 917
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From: NOVA/DC
20' RCF, 18' NX, 09' E350, 07' Solara, 05' STi, 01' Ranger
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From: MA
2008 E350 4Matic, 2011 E350 4matic
You could probably also pull a trickle charger into the cigarette lighter. You'd have to move the fuses so that the lighter is on even when the power is off. There's a fuse block under the trunk, there's only two fuses that let you move it to a separate position. Lots of trickle chargers come with adapters so you can use the cigarette lighter or clips. Also while the trunk tends to pop open completely, it could also be cracked although the light would probably stay on.
Super Member
Joined: Sep 2014
Posts: 917
Likes: 134
From: NOVA/DC
20' RCF, 18' NX, 09' E350, 07' Solara, 05' STi, 01' Ranger
Perfect! I'm going to use this exactly as it's perfect and will actually be a shorter run of wires because my outlet is on the driver side wall, where for our CLK it was on the passenger side and my wife ripped out the damn thing from the wall because she didn't see the cable under the car...lol This is perfect, can leave the hood cracked and slip the connector out the side!
Thank you!
-Nigel
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84 300d 2009 e320 bluetec (retired)/, now 2012 E350 4-matic blueefficiency automatic
My open trunk lights turn off after 5 min. I leave the trunk wide opened in a closed garage to avoid a drive away with the cable connected and critters in the trunk
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From: Charlotte NC area
2019 WS222 S450 4-Matic / 2007 W211 E350 4Matic (Sold) / 2008 X164 GL320 CDI
Of course if you are charging, that may be irrelevant.
Out Of Control!!
Joined: Aug 2010
Posts: 12,516
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From: Charlotte NC area
2019 WS222 S450 4-Matic / 2007 W211 E350 4Matic (Sold) / 2008 X164 GL320 CDI
Senior Member
Joined: Jul 2013
Posts: 493
Likes: 14
84 300d 2009 e320 bluetec (retired)/, now 2012 E350 4-matic blueefficiency automatic
The tender only puts out 2 amps max and tops off a good battery Overnight with the trunk open. If the parasitic drain must be lower than 2 amps. Likely under 50 mA to top off the battery That quickly
