Trying to squeeze a little additional service out of a weak battery is false economy at its finest. Possible unintended consequences include damaging your alternator and starter, damaging to the vehicle due to excessive outgassing and boilovers, and getting stranded at an inconvenient time or place.

A typical battery has a monthly cost of that is less than the cost of a couple quarts of diesel fuel. Not exactly great savings potential; even less if the battery is covered under a prorated warranty.

In general once a battery has seen better days thats usually about it. You can usually remove the sealing caps and if the battery is pretty dry deal with it and charge and check it.
A poor battery does make your alternator work too hard. There can be false economy here as mentioned. Unfortunatly I have several batteries on their way out. It is not the best solution but occasionally an auto wrecker has some cheap batteries that checked out well. It's up to you to decide on the credability of the seller.

The thing I want to know is how old is the battery? A lot of batteries have 2-3 year free replacements.

Before winter starts, take the battery out and take it to autozone or advance, etc. where they have the free battery testing and charging service. Make sure it works or replace it.

Trying to squeeze a little out of a battery is not good. It can leave you stranded and waiting for AAA, etc. Sitting in a car in 20 degree weather waiting for a jump is NOT my idea of fun.

BTW, Mercedes 1-800 number does offer free jumps and I have used this before like 10 years ago. Its free, but you still have to wait and I tip the tow truck driver.

Mercedes makes a BLACK battery that is gel filled and a lot like optimas. It fits perfectly, looks nice, etc. but also has a heavy price tag. I have been using one for 2 years and it does work great.

There are smart battery chargers you can buy that desulfates the battery and trickle charges it, etc. For a good quality one, expect to pay $100 maybe more.

They kind of work, but kind of dont, it depends on how wore out the battery is, don't beleive the marketing and hype that you can "revive all old batteries", etc. for me, it only worked on 1 out of 4 junk batteries I had. Then the smart charger broke and I had to return it, lol.

They do make stuff that you can pour into a old battery and it supposedly desulfates it and revives it, BUT on the Mercedes black batteries, there is a label that clearly tells you not to remove the caps ever and you cannot remove the caps without breaking the label. so much for that idea....

But I agree with tango. Batteries are cheap and easy to replace compared to starters or alternators.

If the battery has or is discharged, the correct method is to charge is on a charger. That takes a lot of stress off of the car system components. Idling will not fully charge a battery.

First, before charging, I would check the voltage between each cell. A wide variance could indicate an internal short or shorted cell. Not good. If it has been boiling off water, then you also need to check the charging system.

What ever you do, make sure to check it prior to trying to charge it. They can and will explode. I have the experience to back that statement. Fortunately, the battery was out of the boat at the time.

Using a weak battery can cause you a multitude of headaches, including starter issues.

__________________
87 300SDL - 215K Miles !!
99 F-350CC Dually PSD - 190K
86 300SDL - 189K
All on B-100

I second tangofox 100%! I can't believe people trying to stretch a dying battery at the cost of a more expensive alternator, a starter that draws MORE amps as the voltage drops and the additional small amount of extra fuel you are using to drive your alternator trying to charge a poor condition battery at high amperage.

SPEND A DOLLAR TO SAVE A DIME!!!!!

__________________
My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.

Good reading here re battery restoration on my buddy Jim's webpage.

At one point he had a schematic for a desulfator up.

http://www.dallas.net/~jvpoll/Battery/aaDesulfatorSurvey.html

Ah, here we go:

http://www.dallas.net/~jvpoll/Battery/PerformanceDoc23/PerformanceDocumentation_Units23.html

I may have all the parts to make that desulfator. I just have to find my 555 timer ic's and I can just breadboard it.

__________________
1981 300SD 512k OM603