Battery Life
I very recentlyl bought a 2000 540i (the car was placed in service in 10/99). It appears to have the orginal battery, making it almost four years old. There appears to be a coding to it. If a green dot appears in a window it is fine. A black dot means charge. A yellow dot means replace. Assumnig I am looking at the right thing, the window has a black dot. I gather BMW puts the battery in the back to keep it away from engine heat and give it longer life. Should I replace the battery? What kind of life do people generally get from their batteries? Thanks.
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4 yrs isn't bad for a battery but everyone's experience is different so there's no real accurate gauge of battery life.
95 T Bird, 66,000 original battery
this is one thing you should be able to avoid if you have the dealer change it out, they should be cognizant of the issues.
but you should figure out what your security codes are on radios, etc. and write them down now, while you can. see the dealer if you can't find the instructions.
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although it appears I don't have similar issues in my detroilet iron at first research, I am going to whip up a standby voltage regardless before I hook up my trailer brake controller direct to the battery. this will consist of a 12v gel cell hooked through a lighter plug to keep the radio, etc. memories alive while I fool around with the post connectors.
there are "radio save" kits of a lighter plug and a 9-volt battery clip in auto parts stores. but if you have a hood, trunk, or door light on while you are changing that battery out, the 9v job will be dead in seconds. your general 1.5 CP bulb draws something just over an amp, so I figure a 6 AH battery from one of my computer UPS systems will do just fine.
2014 Mini Cooper (stick shift of course), 2016 Camry hybrid, 2009 Outback Sport 5-spd (keeping the stick alive)
Case in point---my Benz battery is over 5 years old, works fine day in and day out, but when I took it up to snow country it could not crank beyond 30 seconds (in 10 second bursts). So for 95% of my use it was good but for that 5% is was useless.
I think 4+ years is a good time to switch out the battery if you MUST have absolute reliability under all conditions.
I've got a couple phoenix-area transfers in the office, but have not asked them to raise their hoods yet to verify this...
sure a far cry from chrysler's introduction of the alternator, in which they took the battery out of a test car, and drove it coast to coast to coast to show the alternator provided more power than anything before.
For me an AC Delco maint free (no caps/plugs to check level etc) and if no Delco available for engine then the best top of the line (non gel) highest CCA one I can find that fits the case at Advance Auto or Auto Zone . Go for the warranty (by that I mean the replacement free part of the warranty) the prorated portion is worthless. So a 2 year replacement free 4 year prorated is better then a 1 year replacement free with 5 year prorated.
otoh, the battery is made by Johnson controls which also makes the interstate batteries. I was thinking that maybe it might be a good deal.
Amazingly enough, Sears sells a replacement battery that matches the CCAs and dimensions of the OEM battery for $99. It also has a pro-rated warranty up to 7 years. It makes me wonder if they really expect it to last that long.
My original battery surely did. It still started the car reliably, but the voltage would sometimes dip during starts, resetting the clock.
Anyhow, the new battery worked out great, and resetting the radio anti-theft is something that most owners of German cars are used to.
my personal uninformed opinion, based on no particular access to industry data at all, is that any battery that doesn't last at least 3 years without abuse (bad alternator or regulator, off-road racing, jumping across the cornrow furrows, running it dry, etc.) is one that I will never buy again.
Both the ones in my truck and my convertible are slowly approaching their 7th year of service.
See my post “528i Starting Problems”. The new battery, so far seems to have resolved my 6 month random no start problem which several BMW dealers could not and did not even thing of the battery. The battery was the original that came with the car.
Were Chrysler alternators better than GM alternators, back in the day? I know that Mopar went to alternators before GM, but what about when GM finally switched to them?
a generator car would stop dead because you have to turn the armature (basically the same thing as an alternator rotor) within a magnetic field to generate electricity. both alternators and generators use a field coil to set up that magnetic field instead of pounds of permanent magnets; cheaper, lighter, smaller, and lasts longer.
generator fields were always energized from the battery, thus, take the battery off, no magnetism, no voltage... nothing to commutate for spark coil primaries, so no spark... you walk.
old-style alternators, like the original Motorola ones that Chrysler introduced, had a mechanical relay voltage regulator that allowed the battery to energize the fields through a resistor, or allowed the rotor's wye-coil to energize the fields through a diode module... with the higher output to the battery going through larger diodes. so the original Motorola alternators could indeed self-excite just enough at idle to keep operating once started.
doesn't work that way today, the battery is at minimum a reference voltage for solid-state regulators that control output by adjusting the current in the field coil. my big Ford alternator even has a lead from the engine computer to cut alternator output if you whack the accelerator hard and the engine needs to shed some auxiliary power beyond the a/c compressor to try and deliver. you pull the battery cable on a modern charging system and you will get an ugly and dangerous spark along with hundreds of dollars of charging system damage.
Swschrad, thanks for the rundown on alternators, batteries, (and bears ;-) Interesting info. Good to know, too...I wouldn't have known that you can't pull a battery out of a modern car without doing some real damage. Although in the case of my Intrepid, the thing's so buried it's not like it's a 30-second yank-job, anyway!
"you pull the battery cable on a modern charging system and you will get an ugly and dangerous spark along with hundreds of dollars of charging system damage."
But that is only on a running engine/active charging system, right ? If the alternator is not running, there would not be enough energy in a static field to cause that kind of damage, from my point of view.
Otherwise all those manuals asking me to disconnect my battery before doing any electrical work on my car would have been seriously wrong.
you are completely correct that if the system is not in use, pulling the battery cable(s) off only affects things like computer eraseable memory and so on, and should not be breaking flows of current and removing reference voltages/currents from operating systems that need 'em.
the regulators let through a tad bit of the 16 volts, then click open their relay contacts as coils heated up, and then the battery was fed with something like 10 volts until the coils cooled down again, and higher voltage hit. the battery as a voltage damper masked this action, and you appeared to have anything from 12 to 16 volts, depending on how you bent the relay contacts to introduce a mechanical delay in the process.
those regulators could stick and either overcharge or undercharge the battery, but with nothing to damage, really, it was possible to run on 'em if you didn't have large current loads with the battery off. remember, we didn't have computer control on the 1961 mopars for anything, and computers tend to do things like melt and die instantly if they are fed overvoltage.
what happens now in a regulator is you have a solid-state IC and transistor system -- you have a reference voltage generated off the battery by an IC that biases the operation of a current amplifier stage (pass transistor) or equivalent output circuit in a triac or IGFET. the reference voltage is part of a comparator, in which this is checked against the output of the alternator. if the reference voltage is higher, that means the alternator is low, and more current is allowed to the field, creating more voltage. if Vr is lower than the alternator, the alternator is cut back by reducing the current in the field winding.
and if Vr from the battery suddenly disappears, you go out of range. what happens depends now on what choices the designer made. if the designer of this car's regulator decided that there would be no extraordinary measures to try and recover from what might be a dirty connection, the field will be cut below the point at which you generate electricity, and you stop dead.
if the designer decided they would try and "punch through" a spot of corrosion at a battery connection that could have caused loss of Vr, the bias on the pass transistor (triac, IGFET, whatever) would be radically modified, and the last gasp of power from the collapsing magnetic field in the alternator would basically be cut through. you "spike the field," which is probably already spiking, to try and weld through the problem in the battery leads.
physics predicts that as the magnetic field dies in a coil, and the steady (saturated) field collapses, this magnetic field collapsing will in itself cause a spike voltage. the collapsing field cuts across the coil wires and provides a magnetic analog to the engine's rotation usually used to cut the field with the windings of the rotor, generating voltage. the spike from a collapsing field is often higher than the steady voltage the rotor makes cutting a steady field.
/ late edit / oh, yes, the little detail about the field "should already be spiking" due to collapsing voltage. this means if the variables are aligned in the wrong way, even if your design of the regulator doesn't cut the spike through, you can still generate an overvoltage spike in a "coast to stop" system that can damage electronics. almost forgot that point. / end edit /
there should be "snubber" diodes to short out the spike in the wrong, anti-polarity direction, which is why you are advised to never try and "polarize" an alternator by shorting the thing briefly on installation... something you had to do on a generator. whether or not the snubbers are damaged by peak reverse voltage over their limits, there will be a big spike positive.
big spikes positive with solid-state electronics punch through the silicon's structures and kill stuff.
so there is quite enough likelihood that pulling the battery from a running alternator system nowadays is going to be ugly that I am not going there on a bet. the Belchfire Motors alternator for 2001 might have been designed to just quit if you do this, but the 2002 supplier might have had another idea altogether. and I'm not going to be the test agency for these parts, particularly as the costs keep rising for the things :-D
lest anybody say it's idiotic to put a zap into an open circuit and anybody who does it is a thug on drugs... the telephone system, from DC to daylight, on every service, is built with a "sealing current" flow that does the exact same thing. this is done because corrosion at the connection points has shut down lines since the 3-wire days. "sealing current" flows as the 48 volt battery is interrupted, and that usually has an arc-welder effect to cut through the crud at one or many points of the wire/connector mating point and restores the circuit. the end effect to a voice user is crackle or hiss, and to a data circuit is a shot of spikes that causes a loss of nail-up information between ends, taking the circuit down for transmission until the two ends nail-up a new logical connection on the wire.
MORAL: if your battery is a paperweight, copy the numbers off the label or out of the manual, and whistle up a cab, bus, or neighbor to ride down to Parts Is We and get another one that way.
Well, what's the worst case scenario if you pull out your old battery without anticipating radio codes, computer issues, etc.?
get a fuseholder, a power plug for the lighter socket, and a gel cell from your batteries plus or similar outfit that is good for 4 AH or more, and you have enough hold current to get past the fifteen overhead and courtesy lights that come on when you open the door on something like my friend Exploder.
in the case of my car, I would just lose the radio settings, and the engine computer would just hunt and fiddle around for 30 seconds to a minute after I make my first start until it gets the idle profile restored. not worth worrying about, except I am an electronics tech head, so I will do it when I finally get my trailer control power wired.
in the case of a european car, you best be on good relations with your dealer, they will probably have to help you recover your radio from "enter code" hell.
but it worked out. I must aploogize, when I first read your #36, I thought you were saying disconnect the bad battery after jumping the car to life and had visions of unpleasantness. re-reading, you were just talking about taking the jumpers off. that is still legal and permitted in all jurisdictions
But you do make a good point about lights, so if you have an underhood light or trunk light, make sure the bulbs are removed before you proceed.
But the 9V should work.
TB
however, if you are SURE you can use those clamps without interfering with taking off and putting on the cables, an electrolytic in the range from 1000-2200 uF should suffice to make DC, not DC with high ripple.
measure the voltage on a testbench with a single 914 bulb as load first, though... if it's above 14 volts with capacitor added by a toggle switch, you may risk the electronic geegaws, although as a safety measure in design, they should tolerate 16.
"[...] in the case of a european car, you best be on good relations with your dealer, they will probably have to help you recover your radio from "enter code" hell."
Strange, but in all my european cars (BMW, Benz) the code was on a little check card that came with the manual. It takes me less than a minute to punch it in. If you have misplaced it, a simple call or e-mail to the dealer will do.
It's probably better to get familiar with it anyhow. I'm not comfortable working on my car unless I have disconnected the battery. (No spark, no fried electronics when opening/closing electrical connections.)
I didn't check the size of the fuse in my 6 AH hold battery that I hooked to a lighter plug for volatile RAM maintenance yesterday, turns out I had a 2 amp in there. popped the back hatch for another tool and the courtesy lamps blew it. oh, well, all I really had to reset was the climate control out of it, and that's two buttons. your results may vary... if the wiring on your lighter cord can handle it, use a 10 or 15 amp fuse just in case.
a motorcycle battery should have more oomph than 6 AH for sure, I'd guess maybe 30 to 40 for most of 'em, and that's plenty of hold battery for a day or more on your eraseable settings.
It is supposed to be able to jump a dead battery in about 10 minutes of connection time. I have never tried it out because I have jumper cables and they would be faster.
Would a device like this be enough to hold the charge while one replaces the battery? Our GM car has a radio with the "theftlock" feature. I don't have the code for the radio and want to avoid hassle when swapping the battery.
this would be a good time to determine and write down what the activation process is for that radio, and staple it in the owners manual radio section.
as for replacing jumper cables... well... let's just say I have my doubts. the little geegaw might do the job if the glove box light was on for two days and ran the battery down, 10 minutes is more than a mite optimistic. but if there is a fundamental problem like a dead cell or the battery is just beat and done with, the lighter plug jumper won't do diddly for you.