Battery Chargers

[Penguin]

Just bought a new CTEK US 3300 battery charger and so far like the way it works:

http://www.ctek.com/PDF/folder_USA_low.pdf


Got it at Amazon for about $53.

This is the charger Porsche sells in the US with their brand on it for around $100, I believe.


For years I have been a user and advocate for the Battery Tender, mainly for my motorcycles. And the Battery Tender is still an excellent charger. (BMW sells the Battery Tender under their logo for around $70.) But I like this CTEK for a few reasons:

(1) It is water-resistant. While Battery Tender makes a water-resistant model, the mainline version is not.

(2) The CTEK allows you to choose from three modes: (a) 0.8 amp for Motorcycle and other smaller batteries, (b) 3.3 amp for automotive batteries, and (c) 3.3 amp with a higher "top off" voltage of 14.7 for charging in cold weather (below 41F) or for AGM batteries, which like a slightly higher final voltage. (I would note that the X5 charging system seems to run around 14.7 volts much of the time).

(3) The connectors to put different ends onto the charger are nicer than the Battery Tender, which uses cheap trailer-style connectors. The CTEK connectors have o-ring seals and a lever/button to push to lock and disconnect. Not a big deal, but a nice touch.

(4) If you let a battery become discharged a lot for a while, it has a mild first step to counteract mild sulfation of the battery. This is probably most useful for motorcycle batteries neglected during the Winter, but might help larger batteries as well. When it senses a very low battery voltage, it pulses the voltage quickly for a while to help remove some of the sulfation.

Two differences which can be debated are (a) when it goes into maintenance mode, and (b) what it does when it goes into maintenance mode.

The Battery Tender goes into maintenance mode when the current drops to 0.1 amp, while the CTEK goes in to maintenance mode when current drops to 0.4 amps.

When the CTEK goes into maintenance mode, it essentially stops all charging and monitors the voltage. Only when the battery voltage drops to 12.9 volts does it do anything, and then it starts a new, automatic, charging cycle back-up to the maximum voltage before stopping.

When the Battery Tender goes into maintenance mode, it continues a constant voltage trickle type charge maintaining the voltage at 13.2 volts.

Now, some say it is better for the battery to be maintained with a small, constant float charge to minimize the cycling. OTOH, others say that with a 13.2 float charge, the battery will not get back to 95-100% of capacity until a new cycle is manually initiated by unplugging the Battery Tender, letting the battery sit for a while, and then reattaching the Battery Tender.

I suppose a case could be made for either case.

But I think a major advantage for X5 owners is that the 3.3 amp rating of the CTEK should shorten the charging time of an automotive sized battery, as compared to the 1.25 Amp Battery Tender. This is my initial experience as I charged the battery in my Z4 today with the CTEK and it completed the cycle in about 8 hours, where the Battery Tender usually took more than 15 hours to get a solid green.

Anyway, those are my thoughts and initial experiences with the CTEK vs. the Battery Tender.


P.S. CTEK also sells inexpensive pigtail connectors which can be permanently attached to the charging terminals of the vehicle. They have versions which have three LEDs, Green, Yellow, and Red, that show the battery voltage (see the "Comfort Indicators" in the brochure I linked to at the start of this message). At first I was concerned this might be a drain on the battery, being constantly connected. But I bought one and it simply flashes the appropriate LED briefly, like the alarm LED on the mirror. So with this connector, you would get an early warning if the battery was getting low and needed a charge. My only concern is if this very small, very brief pulse could inadvertently cause some modules in the X5 to not go to sleep, since theoretically it could put some noise on the power buss. I doubt that this would happen, but I have to mention it as a possibility.