Ctek charger with power supply -- good price
 

The Ctek 7002 is an excellent battery charger/supply made by Swedish Co. that supplies MB with OEM chargers. This model is an advanced one with power supply mode to power your car while you change out battery so you don't lose power and settings which is handy on the newer models especially. Also, this model handles the larger batteries our diesels have.

These sell for over $110 usually so the price is really good too (maybe a close out)!:

CTEK 7002 Battery Charger with power supply

I'd get this myself but picked up a used one for about the same price a few months back.

I've been using one of these for 6+ years and it works perfectly. Less than $20.

Battery size has nothing to do with it. You could charge a 200AH deep cycle Data center battery with this. Would just take a looong time. For maintaining/float charge, makes absolutely no difference.


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Ctek is MB OEM. I would only use this manufacturer on the newer models with sensitive electronics.

Battery maintainer more than signifigant charger. I doubt for example it puts out only 12v. It does have a cut out when whatever voltage it is designed to reach is achieved. Or perhaps a zener diode type of set up as the lights change. .A battery only charged to 12 volts is seriously undercharged.

I have purchased many battery chargers from yard sales for a dollar or two. Not expecting them to work and have not been really disappointed.

They are usually very easy to repair. I have not had one transformer bad in them yet. Perhaps putting underrated transformers in them presented too much of a fire risk. Most chargers under seventy dollars incorporate high failure items. Like very old fashion selenium rectifiers. Made so poorly I really think they are designed to fail. To sell more battery chargers.

Just bridging them with a silicone rectifier gets them back on line in the majority of cases. Parts under a dollar. I have given many away and still have enough for myself. Now the ones with true microprocessors have not come my way. They may not be a walk in the park. Part could be impossible to get. Yet again the risk for a dollar or two it could still be something else of a minor nature.

My brother in laws 175.00 charger failed and it was only the auto resetting current cut out. Most those cutouts are a dollar each for many current ratings.. The manufacture put an odd ball rated one in his so the part was 8.00. During testing it was unable to reach the labels current ratings. Maximum current peak was only for about ten seconds

There was nothing other than an intentional error on the label as the cause. There was no way it could sustain the fifty amp rating for any time on a thirty five amp current cutout. It could easily sustain the two lower amperages claimed.

They really seem to cut corners to maximize their profit on the majority of todays battery charges for auto batteries. Or they want repeat sales.

Leave it to put dead battery chargers out in yard sales. If it is more than 1-2 dollars. Just plug it in somewhere on their property and do a spark test. Older battery chargers are far more durable. Although to be fair the rectifier was a better design in the brother in laws charger.

In my search for parts I found little left of the old north American built companies chargers. They still had the names but their business was having them manufactured overseas. So original parts and some had some odd configurations were NLA. They are just basically distributors today. For a good battery charger you want a voltmeter and amp meter. Or at least an amp meter at the minumin.

Battery tenders/maintainers/chargers are not created equal. And not all are suitable for other than conventional lead acid batteries. Make sure you get a unit that suits your battery type. The amperage they can put out also varies a lot. The Battery Tender pictured above only puts out about .75A, I believe. Ctek have a range of different outputs depending on just what you want to use unit for. The 7002 puts out up to 7A. This is the user manual. It has modes for wet cell and other types of batteries.

I wouldn't connect one of those really cheap units to a modern car (like HF ($10.00 float charger), unless the battery was disconnected. Danger of damaging the electronics because although average voltage may be 12V, it is likely not well smoothed and may have higher spikes. The more expensive multi-stage microprocessor controlled maintainer/chargers will be much easier on your battery. Picture below of typical multi steps. The cheap units don't do this.

I have a multi-stage unit that is likely made by or copied from a C-tek. I leave our E-class connected to that during the winter. No problems for years. I have a larger marine type for general charging and it is also multi-stage microprocessor controlled. Years ago, I had a Battery Tender. I think I bought my present maintainer when that one failed.

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It was a good price.....all five sold in 24 hours!

Battery chargers and batteries are a little like oil threads. There are a lot of schools of thought.

I wondered if the electrical system saw any effect from the frequency spikes for those chargers that desulphate batteries. The battery acts like a large capacitor but may be defeated by high transient spikes increasing the voltage momentarily. Of the spikes are going negative that would not apply.

Since a battery maintained at full charge is not supposed to sulphate. A friend of mine who uses battery maintainers still has short average battery life. He has an assortment of cars of a collector nature. Seldom driven.

I have found to get the expected battery life. I have to keep the vehicle in pretty much constant daily service..

Even then I have had a few batteries just up and quit over the years. With no warning at all.

It seems to vary dramatically....on my diesels I'd be lucky to get 6-7 years from a battery with our harsh winters....but on my 2001 E320 I just replaced the ORIGINAL battery in January because it was cranking very slow if I left it in the cold for more than a couple days. Battery was roughly 18 years old. Pretty incredible. Original MB/Varta battery. Put in a Duracell AGM and its been great.

Interesting that we have had to replace our E320 battery fairly often. Maybe 4-5 yrs.

One problem we have, is too many cars! Or cars we don't ever drive very far.

Originally our E320 sat a lot in summer and was mainly used for long trips in winter. The electronics drain the battery while sitting. Then we might go for short drive and park the car again. Repeat this and battery is sitting there at a low state of charge which is not good for a battery. Car now gets driven much more, but we have same situation with our current newer go-south car. I now use a smart battery maintainer on seldom used car.

My old 300D gets drive a lot in summer, but always very short trips. Each start drains the battery a bit and then trip is not enough to recharge it back to where it was. By end of summer, I notice engine barely turning over before it starts. Overnight charge restores it!

So as barry said - driving car regularly leads to longer battery life (so long as you drive it far enough to recharge amount drained at start) Probably because battery is always almost fully charged.

CTEK 7002 at good price...
 

The same seller has listed more of the CTEK 7002s at $75:

CTEK 7002 Battery Charger/maintainer and power source -- $75

I'm using one of these on my E320 CDI and S550 4-matic over the winter here in OH....if I get a few more years of battery life on each, it will pay for itself. I can also install a new battery and it will maintain power so settings stay static during the change.

Still three left in stock...
 

Still three left:

CTEK 7002 Battery Charger/maintainer and power source -- $75

Seller relisted some more of the CTEK 7002 at $80 (I guess the tariffs are kicking in):

CTEK 7002 Battery Charger/maintainer and power source -- $80

This model is an advanced one with power supply mode to power your car while you change out battery so you don't lose power and settings which is handy on the newer models especially. Also, this model handles the larger batteries our diesels have.

I've seen these at over $110 usually so this is a good price if you need a charger maintainer and the supply mode is a bonus. .