K6JRF at the mic K6JRF's Page
formerly W6FZC

My Mercedes Benz
S500 Coupe

K6JRF's MB S500 Cpe
(Update: Jul 7, 2010)

Analyze and Troubleshoot "Check Engine" MIL and Electronic Control Units (ECU)!

The PS1562A Charger failed. Repair details here

Maintaining your Mercedes Battery

New Model: Schumacher PS-1562A-CA
Schumacher PS-1562A-CA Charger/Maintener Recently Schumacher has released a new model with the suffix "-CA". This model operates a bit differently with improved user features.

I purchased this model for my second car and it works better than the original model IMO b/c of the following new feature:
- Reverse hook-up protection - Charger will not operate if clamps are reversed. LED indicator will flash.
- Slow flashing of green LED when battery charge is complete.

The last new feature is probably the best since the older unit will fail if the cable connection is reversed. The new second feature alerts the user when battery charging is complete.

Compare the new unit showing the horizontal LED placement vs the vertical placement for original unit (pic below). That should alert you that it's the new "-CA" model.

Inside - PS-1562A-CA
Schumacher PS-1562A-CA Circuit Board The inside has been re-designed to remove the power transformer in favor of a "switching" power supply (PS) that is direct connected to the 120Vac mains. That accounts for the lighter weight, 1 lb vs 3 lb for the original unit.
Schumacher PS-1562A-CA Circuit Board Detail of the PCB shows the switching PS and the signal processing. On the back side (not shown) is the remaining portion of the circuitry. No schematic is furnished so repair will be difficult.

The round, red colored device on the lower left, is an 1amp input fuse. There is no output fuse so the ckt protects against reversed battery cable connection. A nice feature!

Retail price ($22) is similar to the original model but not all outlets carry this model.

Schumacher Battery Charger/Maintener

Slow Charge/Floating your MB Battery
As was described in the previous section re 'reconditioning' or 'equalizing' your MB battery, this section details the "maintainance" techniques that will guarantee a fresh battery even if the car sits for long periods without being started or run. This is a regular occurence now b/c I don't use the car as much as I did. I ride my bike instead!!

Recently, I removed my old Alpine GPS system in favor of a newer, more compact system made by Navigon, Model 7100. This was gift from my son who purchased it and found that he didn't need it. A very nice gift and very much appreciated. My old Alpine read the master map CD located in the trunk. Of course, this is much slower than today's methods [read a flash memory chip] so route calculation typically took up to 3 minutes. The Navigon takes 30 secs. Also when a route is changed on-the-fly, the Alpine would take up to 2 minutes to recalculate the new route whereas the Navigon takes 5 secs or so.

Unlike the Alpine that didn't have an internal battery, the Navigon does [Li_Ion] and it requires apx 5V @ 1amp of charging current whether it is "on" or in "standby" modes. So keeping the Navigon's battery charged will ultimately cause the car's battery to discharge especially when the car experiences long periods of inactivity. So some form of charger is needed b/c charging the car's battery will also charge the Navigon's.

Schumacher Battery Charger/Maintener After doing some Internet reading, I purchased a small battery charger/maintainer made by Schumacher, Model 1562A. There are a number of similar models under this part number but they're all about the same. The price varies quite a bit so shop around. The best price I found was at Walmart for $20.22.

It features microprocessor control with automatic voltage detection (6V or 12V). It has a multistage charging algorithm and desulfation along with a "Maintain Mode". It is also temperature compensated which prevents the battery from overheating. It displays the power and charging status and it works for small or large capacity batteries. It has a versatile quick connect harness that easily changes between battery clamps or ring terminals. It's also features reverse and short circuit protection.

The main operating controls are shown to the right: after making connection to the battery, the microprocessor will take the battery through a 'charging' state, up to 14.8V. Once it's properly charged, the unit switches to a 'float' charge mode where apx 13.3V is applied. If the current demand changes, the unit will go back to a charging mode until the battery is charged, then reverting to the float mode. All-in-all, a simple, straightforward battery maintainer system for a really decent price.

Cable onnected to battery Battery Cable plugged into Schumacher For the W140, the battery is in the trunk on the right side under the carpet.

To make a connection to the battery, remove the carpet and use the supplied "Ring Terminal" battery cable along with two (2) screws to make a 'permanent' connection as shown in the right picture.

The cable length is apx 10' long and has a mating quick-connect on the end. When not in use, it stores nicely in the trunk.
Charge Times vs Battery Size
Charging times vary depending on the size of the battery (amphours) and the state of charge. The table shows the typical charging times based on various battery sizes. A MB battery for the C140 (or W140) is typically 500 CCA minimum with the one I have around 750 CCA capability. From the table, that shows that it could take from 19-1/2 to over 24 hours. Initially, my battery required about 17 hours when first connected to the Schumacher. Now it takes about 2 - 3 hours to attain the float mode.

Definitely a worthwhile device to ensure that your battery is at peak condition whether your car is driven daily or sits for long periods of inactivity as mine does.

Send me Email Icon with your comments