Battery Maintenance/Float Charger Connected While Battery is Removed

[jim628]

hi:

I am planning to charge my X5 battery with a rather high AMP battery charger. In order to avoid damaging the electrical system, i plan to disconnect the battery and completely remove it from the car. In addition, before i remove the battery , i plan to connect my BMW advanced charging system (float charger) connected. I will leave this float charger connected while the battery is removed.

My question is, is it save to do this? Will this damage the electrical system, especially the expensive electronic control unit of the car?

Thanks
Jim

[bcredliner]

The battery is dead so you are unable to start the engine?

I have disconnected the battery many, many times. Never hooked up anything to provide current for the electrical system. I have also charged my battery many many times without unhooking it. Never had a problem. I have had to re-do the radio presets and enter date and time but that's it.

I don't know what year or model you have. My reference is a 2002.

[Qsilver7]

I've used a simple float charger connected to the engine bay jump start locations...while disconnecting and removing the vehicle's battery.

I've never had any problems...as long as you make sure to protect the ends of the disconnected battery cables...making sure that they don't touch metal or each other. I have wrapped rags around the ends and used some old (no longer worn) socks...just to protect the battery cable ends...since using a float charger in this manner, there's still current running through the system.

Doing this...obviously...saves any of the things you lose to electrical disconnect for short or long periods of no power (radio presets, sun roof, OBC calculations, trip odometer, etc).

I do have a question, though...why are you using the "HIGH" amp feature of your charger? For the most part, a discharged battery does better with a low amp/long charge period. For example, 2 amps @ 20 hours...or 6 amps @ 16 hours is better for the battery than 30 amps @ 3-4 hours.

Also, using the engine bay jump start terminals "seems" to be better for charging the battery with less chance of damaging any sensitive control modules. I've never heard of any issues of blown modules when using the engine bay location...but usually once or twice a year...you hear of issues when someone has connected directly to the battery. Not sure why...or if it was operator error etc...but the engine bay tends to not cause issues.

Just make sure that you use the correct hex nut designed for the ground connection...and not just some random "metal" component in the engine bay.

You can see in the info below from the owners manual...that BMW recommends using the engine bay for charging & jumping...and also it lists some of the things that will need to be reset if you don't, use a power saving device or routine as you're preparing to do.

[BigBlack48is]

high amp charger = bad idea ... been there, done that.

just go buy a new battery

[bcredliner]

Good point, Qsilver. I have always used the engine bay connections. I use the automatic setting rather than the quick charge option. I have used the high output position a few times but only when the battery was low and I wanted to have enough juice to start the engine and then immediately remove the cables and use the alternator to charge the battery as I drove.

Why is the battery dead? Do you know it is a good battery?

[jim628]

Thanks for your comment.

I have a 2006 X5 (also bought on 2006) that i used only on weekends only. The car still has the original battery and I have been using BMW Advanced Charger (Deltran Battery charger/maintainer which has 1.25 A spec) in the last 5 year. Basically as soon as i am done with my weekend driving, i immediately connect my BMW charger and leave it connected until i use the car again the following weekend. The battery has been working great until last week. Since last week, the battery seems to loose its capacity to store electricity. Even though the charger LED changes to green which indicates 100% charge, the battery does not have enough power to start the engine.

Can the battery still be saved? I was hoping so, and i was thinking of taking it out from the trunk and charge it with a high/medium or high AMP charger (probably between 6 AMP to 10 AMP charger). If it does not work, I will probably loose between $30 to $50 for buying a decent charger. But if it works i will probably save at least around $250 for not buying a new battery.

BTW, anybody knows what is Cold Crank Amp for this E53 battery? If i have to buy a new battery, i am thinking of switching to the brand and type used by Mercedes ML350 SUV. It seems like the brand used by MB is very good. I am driving a 2003 C class for my daily commute and the battery on that car is still the original one. It has been around 9 years (the original replaced in 2004 by the dealer, under warranty, due to acid leak).

[Qsilver7]

Originally Posted by bcredliner

...I have used the high output position a few times but only when the battery was low and I wanted to have enough juice to start the engine and then immediately remove the cables and use the alternator to charge the battery as I drove. ...

Double ditto bcredliner on the above quote. That's the ONLY time I use my charger's 50 amp setting. Its when the battery is dead, and I need to get the vehicle started NOW...and hit the road.

But if my battery was discharged due to some unfortunate circumstances...or it's getting old and voltage is dropping...I use the low & slow recharging method to see if that revives the battery.

To the OP:
You may want to also start monitoring your battery if it fell into a state of deep discharge. Many times this can cause irreversible damage that it will never recover from. IF you've unlocked your OBC...you can quickly (like in 15 seconds) run OBC TEST 9 with the ignition in position 1 (hopefully BEFORE starting the engine) to get an idea of the battery's voltage. If it is consistently below 11.89 volts...it's a sign that the battery is not in the best of health because at 11.89 volts...the battery is a 0% state of charge.

[bcredliner]

Suggest you take the battery to local auto parts store and have it load tested before buying a charger. If you need one they will likely have a battery that is fine for your X5. Be sure that the battery you buy is for an X5 so it will be vented in the same way your battery is vented. The battery won't cost you $250 and will last 5-8 years.

[motordavid]

OP: That 8+ yr old batt is toast...the constant charging you are doing is like life support, but the patient is basically dead.

Hit AutoZone, et al and buy a new one. <$200.
Bring the new batt home and put it on a low amp charge for overnight plus, as the store batts have been sitting.

Install new batt, be happy!
GL, mD

[jim628]

[QUOTE=Qsilver7;1014137]Double ditto bcredliner on the above quote. That's the ONLY time I use my charger's 50 amp setting. Its when the battery is dead, and I need to get the vehicle started NOW...and hit the road.

Hi,
WHen you did this, did you:

A) Start the engine while the 50AMP charger is still connected and charging
or
B) Connect the 50 AMP charger, wait few mins, disconnect the 50 AMP charger then start the engine


Thanks.