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Battery I presume? Secret menu test results...

6K views 20 replies 7 participants last post by  ajc 
#1 ·
Did some work on my car and it sat for a couple weeks. When I tried to start, everything lit up, then click, click, click. No problem, stuck it on the trickle charger for an hour and it started up. Day and half later after just stop and go driving, click, click, click. Checked secret menu and showed 11.4. Stuck trickle charger back on for 6 days since I was out of town. Ran secret menu test today--results below:

key on (no start): 11.6 to 11.7
idle: 13.3-13.5
headlights on: 12.7-12.8 then back to 13.6
driving around: consistently 13.5-13.6, but when clutch in and stopping, 12.1-12.3, then back to 13.5-13.6
engine off after drive (17mi): 11.9-12V.

I assume I have a battery issue, but just wanted a second opinion before I trot out to buy a new one. Currently has 850 CCA Interstate battery previous owner had replaced 1/2012 (after researching I realize it is supposed to have 950CCA)...

As far as use, not a DD. Car sits for a week or two at a time, if sits longer I usually stick the trickle charger on it. From what I read on the board it could be alternator, voltage regulator, or battery...appreciate any input. I'm thinking battery because of age and I'm not getting 12.5v when off.

Thoughts?
 
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#6 ·
Battery light indicates a charging fault, but frankly the system is a fault thru and thru. It is BMWs first attempt at smart charging and it works great if the battery is charged but fails when the battery is partly charged. I don't have the time to explain it all now but the short story is the alt is controlled by the DME. You have seen some of the things it does. When you come off the gas it turns the alt off until a stable idle is set. It also charges at a much lower rate while the car is in startup/warmup mode. Ton of other things too.

It does a really bad thing and seems to evaluate the battery voltage and decide that what ever state it is in is its fully charged state. It slows charging when it gets there which is likely why you only see 13.3-5.
Although you are reading low voltage it is likely because your trickle charger will only partly charge the battery. Read the voltage while charging it will not be near 14v, most only charge to 12.6 max so they can be left on forever without damaging the battery. So the math says you need to fully charge your battery. You were at 11.6 which equals a 10% charge so 85 CCA and you need to get to 850 so that is 765. A trickle charger will only charge 1 - 1.5 amps per hour but those are not CCA generously 1.5 becomes 1.2. This is an average to full charge it will do the bottom 50% much faster than the top. Roughly and only if it could it would take 26.5 days for a trickle charger to charge a battery to full from 10%.

What you might want to do is get a better charger or take it somewhere and have it charged to 12.9 volts put it back in and see if your problems are solved. It may not get to 12.9 but even if it gets to 12.75 you will likely get years of service.
View attachment Battery State of Charge Reference Chart.pdf
 
#7 ·
Always appreciate your insight Sailor 24. It is reading 11.8 on the trickle after the trickle goes to "infinity charge" so I will either pull it and take it to my mechanic or my neighbor said he has a charger I could borrow. Not sure what he has, but he uses it for his boat batteries...
 
#8 ·
I got a nice charger /maintainer at Harbor Freight. Around $30 if I recall. It has both the slow trickle charge at 1 amp and a faster 10 amp charger. It has never failed to charge a dead battery, but it can take 3 days if really dead (like yours seems to be).

I will look later to see brand/part number. It is a red/black case and has alligator clips. I also have a Schumacher which works well if the battery is not dead; it maintains, but the battery needs some charge for it to work.

I guess this is partly @ Sailor, but if you can get the car started (jumper), once you drive for a while, won't the DME allow 13.6 or 13.7 and charge the battery to top it off? I see those numbers all the time when running on the highway.

Regards,
Jerry
 
#9 ·
Gsfent--No need to look it up--the one I borrowed is a Schumacher CS10 which has 55 (start)/ 10 (boost)/ 6<>2 trickle. Had it on 10 amp then checked after 2.5 hrs and it had rolled to trickle so checked volts (with charger removed from battery) and still had 11.7-11.8. I'll keep it on overnight and check in the AM. If shows the same tomorrow, I suppose I pronounce it dead, huh?
 
#11 ·
#10 ·
If you don't have a glass matt battery ignore this and just trade that battery for an AGM. If you have an AGM then try this.

Think you borrowed a smart charger. If it is a really smart charger then it will do the least damage to a battery but it might take 20 some odd days to charge the battery. Smart chargers really are not smart they can just evaluate if there is a plate with less volts than the others. If they detect this they are not likely to charge the battery. You need a dumb charger so you can force that plate to the same volts as the others.

This could break the battery so charge it with the charger the way you are until you have decided your only choice is to replace. It will likely work. Take the battery out of the car. You should have that now because the BMW systems will interfere with a smart charger anyway. At min you have to have one of the posts disconnected.

Assuming it is out and away from things that could be damaged turn the charger to 55 amps, it is not smart then, but it might be and will just turn off. If it does either the battery has a short and is no good or the charger is one of the best on the market. None smart chargers are better for smart people as the smart is left in your control.

After about fifteen minute turn the charger down to 10 amps for the time it takes to switch to trickle, then turn it back to 55 likely for ten minutes then back to 10. If there is a meter, reference that the farther it is in the red the less time you do it. Wait until it switches to trickle and repeat. You don't have to be there right when it turns to trickle but the closer to that time is more productive. Repeat, it will likely take 5 or 6 times before the charger will not switch to trickle and will just charge the battery.
Maybe you have a cheaper neighbor that would not pay for the smart charger borrow his and charge on 10 amps for 24 hours remove the surface charge with any bulb for 30 secs then read the volts if not 12.9 hook up the charger again for 2 - 10 hrs, repeat the voltage read. If you have not got to 12.6 get a new battery. If after that charge the voltage is the same you have reached the max charge, use the chart I posted to decide how screwed the battery is. If you even gain .1 volts repeat the charge you are washing sulfate and will likely have a brand new battery when done.

New battery might be easier and much less work.
 
#12 ·
Current battery is not an AGM. Sat overnight and still 11.6 so time for new battery. Question--which one? Local options below:

Napa AGM 950 CCA $250
Advance AGM 850 CCA $175 w/ discounts
Advance Reg 950 CCA $175

Better to buck up and get the 950 CCA AGM or is 850 CCA AGM adequate?

Thanks for the link on the charger Jerry...
 
#13 ·
Current battery is not an AGM. Sat overnight and still 11.6 so time for new battery. Question--which one? Local options below:

Napa AGM 950 CCA $250
Advance AGM 850 CCA $175 w/ discounts
Advance Reg 950 CCA $175

Better to buck up and get the 950 CCA AGM or is 850 CCA AGM adequate?

Thanks for the link on the charger Jerry...
:)

I have had about the same luck with both kinds of batteries. So I tend to go for the one that has the best reserve in amp hours and CCA for the money.

In your choices above, I would prob go with Advance Reg 950 CCA. I recently purchased one at I think either Advance or Auto Zone and it came with a 3 year non prorated warranty and then I think 2 years prorated. I can probably find the receipt tonight when I get home and see what brand and price.

Regards,
Jerry
 
#15 ·
Just a note if you are paying that much you might want to check with the dealer. I have no logic/proof to this but most cars got ten years out of the OEM battery, but now we think 5 years is a long time. I replaced the original battery shortly after I bought the car in Oct 2010 I am on my second replacement now, my next will be BMW just to see if it goes longer, and I don't care how much I have to spend.
 
#18 ·
13.8 is the target which should show 13.6 -13.9 most of the time. At 14.2 the Alt is completely turned off and the car goes into Alt failsafe which just means it is turned off. I have never seen 14 Although some guys report seeing 14, I am skeptical, I think something maybe wrong with those cars.
 
#20 ·
Have you checked the battery connectors? Last year I had some very strange problems due to terminal corrosion (low voltage code, computer losing settings, stalling during idle).

These continued even after swapping the battery and tightening things down. Eventually, I used a wire brush on the battery terminals and connectors and it hasn't been a problem since.

This is a particularly annoying problem because the voltage can appear normal when there is minimal current.

FWIW I found a battery at Auto Zone for around $150, it seems to be doing fine so far.
 
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