"Battery Tender" Companion Thread:-)

No possible problem, because this device has a diode in series with the 9v battery, preventing current flow from 12v main battery into the 9v battery. Restated, the 9v battery cannot provide any current until the car wiring drops below ~8.3 volts*. And when the car's voltage does increase when the main battery being placed back into service, the 9v battery is electrically decoupled from the circuit. The diode protective effect is instantaneous, give or take a few harmless nanoseconds. And as long as the 9v battery voltage is being below 12v battery voltage will not attempt to charge the main battery.

Realize if you leave this device in place for any considerable number of days, the 9v battery will discharge fast as it alone must provide current to ALL devices drawing curret. And any lights or ignition left on such as when you open a car door, that 9v battery is headed south quickly.

You've probably already got a 9v connector and cig plug to make one except for the 20 cent silicon power diode 1A 20v rating or greater. A dandy device which belongs in every mechanics toolbox. Striped band diode cathode to car battery positive.

*(9v bat voltage minus ~0.7v for silicon diodes)
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It occurred to me that if you are working around the airbag (have to remove it for some reason) You would not want to use one of these devices. It could provide enough power to cause a fault code to be stored in the computer. There is a small chance you could inadvertently fire the airbag (you won't like it). Typically you disconnect power and wait for everything to discharge before removing the airbag.

In this case you will just have to reprogram the radio.

 

Gee Whiz. I keep doing this. Look, those things are fine when doing battrery maintenance. I have one I use on all my five cars from the '98 Tracker to the 575M. However, the good battery tender protects the battery from discharge while sitting. Right now, (forget Al Gore) there is a ton of salt on the road and the temperature is less than 20 degrees. Salt and aluminum do not mix so the 575M sits in the garage. Battery tender, period. Get one and use it. No worries, mate. Cheers!

 

I have one, and it works, but as mentioned, it is designed for use for a few minutes to perhaps a couple hours...I would not trust it beyond that.

I have switched to using a battery tender with a cigarette lighter adapter...it has 1.5 amps. I can leave it indefinitely if necessary.

 

No problem, send her inside to do the dishes.

True but not a biggie. Go to the store and get a cheap diode. Total non-critical part, you can pay more but its unnecessary. Second thought..if you have some non-working electronic gizmo, ax it open and extract a likely looking critter...black cylindrical, silver band at one end. So you just might have all the parts on hand as we speak. (do love that POWIEE!!)
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Does anyone know if you can hook a battery tender to the terminals in the engine compartment on a 355 rather than going direct to the Battery?
I know the battery is where i should connect, but because of how abd where the car is parked it would be easier to hook up at the rear..

 

Yes, you could remove the right side engine compartment side cover, and there is a terminal junction box. You could connect up the ring terminals with the quick disconnect to that, and then reinstall the cover, and leave the disconnect tucked underneath.

Easier still, would be to splice on a cigarette lighter adapter to your battery tender, and just plug it in that way. The door gaskets will easily close on the cable without pinching.
http://www.radioshack.com/product/index.jsp?productId=2062275&cp=2032056.2032136.2032154&pg=2&parentPage=search&y=13&origkw=cigarette&kw=cigarette&x=7&numProdsPerPage=20&parentPage=family

 

Thanks! sounds easy.....

 

NEVER use a battery charger or tender on a car without the battery connected. The open voltage of the charger could be 20 or even 30 volts. This will FRY delicate electronics. People have done this and it is very expensive.

aehaas

 

Just make sure there is a car battery in the car and your charger is directly connected to it while charging.

 

I need some clarification on this. There is a ground strap-wire disconnect on the 308 & 328 (two I am most familiar with). Must the ground strap be connected when using a Battery Tender Plus? This unit provides 1.25 amp, and in their brochure they detail charging a battery in situ and out of the car. Now I doubt they address "every" car, and don't want to be redundant but since Ferrari has ground straps is it ok to use this tender attached to the battery but with the ground strap disconnected?

 

As long as you connect the wires or leads from the charger directly to the car battery terminals, nothing else matters. All configurations are irrelevant.

aehaas

 

Thanks Ali, I just hooked up my tender yesterday and have been charging it with the strap disconnected..thought I may have done something wrong, and yes the charger clips are attached directly to the battery terminals..
don't see me driving in the near future, we still have about 3 ft of snow in places, and more expected this weekend...(Colorado)..

 

Also I guess thoes who use the cigarette lighter method should be advised that potential problems may exist with that method of charging.

 

While you're correct about charging functionality, what about the data stored within the system?

By not having the ground strap attached to the car's power system, won't the history of the engine operating parameters be cleared from memory?
Then again, perhaps it isn't important on 3x8 series

 

Please be more specific. I see absolutely no problem as long as you restrict the charging amperage to 3 amps or less (the lighter itself draws more than that). Many manufacturers that sell battery tenders include a cigarette adapter plug, so I seriously doubt it can be a problem. Among the manufacturers that include a cigarette lighter adapter with their chargers are: BMW, Porsche (who sell a relabeled Deltran Battery Tender Plus) and Black and Decker.

 

+1

The battery has internal resistance so it takes most of the current and voltage. So charging without the battery goes away from goodness. I have never heard of anyone trying it or having trouble, but I personally would not do it.

Lee

 

I did it once a few years ago with a 1.25 amp battery tender...no problem. Obviously, it sounds like it would not be advisable with a 10 or 20 amp battery charger.

 

I have only seen it on the boost setting of big shop chargers and battery or not they can be trouble on some cars. There was a guy this week in the 360 forum who lost a dash board because he had no tender and tried a charger to start the car.


Lesson #1 Leave the battery on and keep a tender on it.

 

Well said!

I used the lighter socket on my 2003 Modena for years without a problem. I used 0.50 amp charging rate to sleep well at night. I use this approach on many of my cars.

My F430 lighter socket goes dead so I cannot use it for charging. I hooked up a 1.25 amp "Battery Tender" directly to the battery. it works well and I still sleep at night.

Lee

 

Yeah, some lighter sockets have direct connection to the battery all the time
and then some are only "switched" when the ignition is on

 

Does anyone know if a 1990 Mondial t Cab's lighter is switched with the key or on all the time?