Safe to leave battery tender on (355)

So the manual says to disconnect the battery from the car via the on/off knob/switch when charging or trickle charging. My question is it safe to leave a battery tender on for a period of time while the the switch is off once the battery is fully charged. I have a Deltran Battery Tender.

 

The WSM mentions disconnecting the battery when using a standard charger to recharge the battery. There are also instructions for reacquiring engine parameters if the battery was disconnected.

You can use your Deltran Battery Tender without disconnecting the battery.

 

Thank you sir!

 

I leave my deltran on the 355 with the battery turned on all the time.

 

You will have no problems with Deltran, I've left them on batteries for over months at a time and I never turn the battery off

When you disconnect the battery with the switch it resets all the I/M monitors to incomplete, not a good thing as you may have problems getting them reset to complete in order to pass smog.

 

You're welcome, Mike. I've done that for years with my F355 Challenge and 550 using Schumacher SE-1-125 onboard battery tenders. Engine parameters and radio presets are maintained that way.

Barry

 

Mike, how/where is your charger hooked up? If you use the battery terminals/earth in the engine compartment, the trickle charger won't even charge the battery with the battery switch off.

 

FWIW, I have used the Deltran tenders for a long time. Probably 20 years. I have only had two tenders quit on me. Both of them were the small 750ma models. They are really only designed to keep a battery charged. Dont use it to bring up a weak battery. The bigger ones are 1.25amps, have a longer warranty and generally hold up better. Good company.

 

Ive had me CTEK on my 355 and 612 for years now. No problems.

 

I use Ctek as well. Found them to be the best I have ever used. I keep switch on for emissions data. I do wonder if it plays a factor in alarm battery alarm wear?


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For me the whole point of putting a trickle charger on is so that I don’t have to cut the battery switch off. Every time the power is removed from your ECU is loses its fuel maps and has to relearn everything from scratch. I try to avoid any unnecessary power cuts, then over time your engine learns how it runs best under different loads and is at its best performance.

 

Doesn't lose fuel mapping, just idle parameters. Still, as you recommend, best to not disconnect battery if possible. I ran a microprocessor controlled tender on my 355 through the cigarette lighter frequently without issue. The cord I used was fused (5 amp) as well. The tender only output 2 amps or less.

 

It will lose all the self learned writable maps across the board and go back to the defaults every time an ECU loses power.

 

I used an Optimate on my Mondial, F355 and now my 360 whilst the battery was connected over a period of almost 15 years across all three.

 

I use a CTEK 3300 for my F355 and I leave the switch on. It works like a charm.

 

https://www.amazon.com/gp/product/B005EKY1EM/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

I also use the cigarette lighter plug. Kind of a wonky fit in the plug so you have to work with it to make sure it registers.

 

Also make sure you don't have a late model F355 which needs the ignition on to hook up the lighter to the battery.

 

Mine's a '98 and no issue. Was that changed in '99?

 

Mine's an '98 (not sure of the day/month), but the cigar lighter won't work without the ignition being on. I believe all cars after this period switched to ignition supplied power. The lighter has a fuse, so I don't know if this is an added safety feature.
My car passenger footwell fuse/relay panel decal still has the cigar lighter on the original fuse, but it actually uses a different fuse.

Mirrors, Doorlocks, Cigar Lighter Wiring Diagram

 

6 yrs on a CTEK. I've replaced one battery through my own fault. Never turned off batt isolator unless it was really required.

 

This applies to the 2.7 only. The manual specifically says the learned parameters will not be lost if the ECU is disconnected on the 5.2 and that there is a special procedure for erasing these parameters. The "NOT" part is in bold characters to stress this point.

Ref: Workshop Manual Vol. 1, page C61.

 

The previous owner installed a quick connect to the battery and I just have the wire routed down the front of the car with the charger on the floor. Sorry about the late response, haven't been on the forum in a couple of weeks

 

It seems that trickle charger technology has improved since Ferrari wrote the F355 manual. All the reports seem to be positive for charging with the battery on (no pun intended). You have to wonder why Ferrari didn't tell you to disconnect the battery when driving in case the alternator damaged the electrical system)

Murphy's Law has been repealed