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Discussion Starter #21
Correction to thread by Ray: the resistance measured should read .03 ohms, not .003. Most DVM's show resistance readings to tenths of an ohm. ray
Thanks for your feedback Ray... My bad. I was assuming you meant taking a direct voltage meter reading from a negative and a negative. I should of known you meant comparing two readings...
And so today, I took a couple more measurements...
First, before I explain what I did, here a pic of the BMS.
As you can see, it draws its negative internally thru the actual battery post.
The two pin Connector consists of the LIN that feeds to the body module and the battery positive feed... Which also comes off the battery post. In between is the fused link (0 ohm resistance).


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Now the measurements... Checking the positive voltage feeding the BMS, I measured from negative to these points here...
All points measured same voltage as direct battery post + and -




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Discussion Starter #23
Next, I checked battery post + to the main chassis ground. No loss there either... Same as direct to battery measurement.

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Discussion Starter #24
Now, at the BMS side (unplugged from LIN and +), I measured these two points to battery +
The LIN voltage measured 9.5V (red arrow) and the yellow arrow (+ feed for BMS) measure 11.4V.
For reference, battery voltage with engine off was 12.23V...

I think to eliminate any issue at these points, I could use some help...
Is any one able to meter these 2 points on there BMS?
If the readings are the same, then I'd have to start looking elsewhere... Likely the LIN line to the body module.
 

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Wungun: I am a little concerned regarding the battery voltage with the key off. A fully charged battery should measure 12.6 volts, or close. 12.3 volts indicates a partially charged battery. Have you checked the voltage between the battery terminal (negative) and the black wire on the BMS? That should show something under .2 volts. I suspect the LIN line is for the ECM to charge control, for the alternator. What is your battery voltage when the engine is running? One other thing to check is the voltage between the Mon wire on the BMS and the battery positive connection. You might also check the voltage between the alternator output (the red wire) and the battery positive, which should be about .3-.4 volts, depending on the current the battery is drawing. Your reading indicate a voltage drop somewhere. Your battery voltage while the key is off indicates a partially charged battery. You might also check the voltage on another battery to check your meter. Let us know... Ray
 

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Discussion Starter #28
There is NO black wire for the BMS. The wiring diagram just shows the BMS circuit. It draws negative power internally thru the battery post. This is all integrated. The only conductors that plug into it are LIN and +.
Both my old and new BMS measured the same, so I'm eliminating it as the cause.

When the fault first showed up, I metered the battery at work, and low and behold, 12.2V. I thought as you did, that the battery is going... So I replaced it with a 790CCA AGM battery.
The new battery certainly cranks over the engine much quicker, but it still only measures around 12.2V between terminals.....
I use a cheap digital meter... But the one I checked the old battery with was a good Fluke MM.
I agree, that voltage seems low. But there is no other indication that its not normal. It's easily started the motor in minus 30 degree nights.

With the engine idling, I'm seeing over 14V at the battery...

Also, I'd eliminate the alternator as I've had this fault for maybe 6 weeks now....? Car still drives fine.

Wungun: I am a little concerned regarding the battery voltage with the key off. A fully charged battery should measure 12.6 volts, or close. 12.3 volts indicates a partially charged battery. Have you checked the voltage between the battery terminal (negative) and the black wire on the BMS? Ray


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Discussion Starter #29
@Ray.
Yes,the LIN line is the communication line for the ECM/BCM.
The MON line measures proper, full voltage going TO the BMS.
From the BMS MON line to battery positive, its 11.5V as I mentioned.
I need someone to check this on their Rover...
And also LIN to +

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Discussion Starter #30
https://www.rangerovers.net/forum/6-range-rover-mark-iii-l322/20369-info-electrical-troubleshooting.html


Here are the generic basics follow through the tests with a basic multimeter. These are tried and true measurements to check your battery, alternator AND cables for resistance if you have cruddy cable ends at either end or a cable failing it will have high resistance and no amount of prayers are going to get perfectly good alternator to charge a battery.
Here is what I have... Couldn't get access to alternator for measurements...
Car running voltage is less than when I last checked it (14.2V) this time.... Odd

Engine off, all accessories on for 30 seconds, then off. What voltage ___12.17V
2. Voltage across battery at idle (no electrical load) ____13.98V
3. Voltage across battery at 2000rpm (no electrical load) _____13.98V
4. Voltage across battery at 2000rpm (everything electrical switched on) _____13.94V
5. Voltage at ALTERNATOR at 2000rpm (everything switched on)___________________
6. Voltage drop between alternator body and battery negative (YES negative). Measure at max electrical load and 2000rpm ______________ (millivolts please)
7. Voltage drop between alternator positive and battery positive. 2000rpm, max electrical load _____________
8. Check Voltage drop from Battery Negative terminal to 1st groundpoint on vehicle_________0. 00V
9. Check voltage drop from 1st ground point to block_____0.03V_____
10. Check voltage drop from Alternator Housing to block__________

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Discussion Starter #31
Also, when I did replace the battery with a new one, it also measure around 12.2V

Is it possible that my new battery is also bad, yet despite voltage readings, seems otherwise perfectly fine?


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Wungun, Unless I am mistaken there is a black wire running to the right of the BMS off the diagram. Can you determine its destination? From the diagram, it appears to run directly off of the battery - to somewhere off the page. Is the diagram misleading? There must be a reason for the battery or charging fault indication on the dash. These systems use voltage drops for everything in troubleshooting. It is possible for the new battery to show a different current draw from the original, but that does not explain why your readings appear very similar. I have seen, for example, similar errors created by the alternator not properly seated in the mount, or defective connectors on the battery. These voltage readings, particularly on the battery with everything off concern me. I know that this is aggravating. One thing to consider here is that the alternator charging voltage is the regulated voltage with a fully charged battery. If the alternator is charging a partially discharged battery, much of the alternator's energy is in current, which WILL lower the voltage. That also concerns me. Suggestion: if you have a battery trickle charger, try charging the battery all night, then check your voltages again. Let's start with that. Ray
 

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Discussion Starter #33
Wungun, Unless I am mistaken there is a black wire running to the right of the BMS off the diagram. Can you determine its destination? From the diagram, it appears to run directly off of the battery - to somewhere off the page. Is the diagram misleading? There must be a reason for the battery or charging fault indication on the dash. These systems use voltage drops for everything in troubleshooting. It is possible for the new battery to show a different current draw from the original, but that does not explain why your readings appear very similar. I have seen, for example, similar errors created by the alternator not properly seated in the mount, or defective connectors on the battery. These voltage readings, particularly on the battery with everything off concern me. I know that this is aggravating. One thing to consider here is that the alternator charging voltage is the regulated voltage with a fully charged battery. If the alternator is charging a partially discharged battery, much of the alternator's energy is in current, which WILL lower the voltage. That also concerns me. Suggestion: if you have a battery trickle charger, try charging the battery all night, then check your voltages again. Let's start with that. Ray
Sorry, it's a bad pic of the schematic...
That black line leading off the page is going to chassis ground.

Since it is a relatively new battery with a 5 year warranty, I'm going to inquire about having it replaced. I think it should show higher static charge.
I don't believe the alternator is at fault as the dealer never pulled any codes concerning it.

Trickle charging the battery over night is a good idea. Would be nice to know if it'll actually hold a higher level of charge.

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Something else to consider here is the temperature where you are. If the temperature there has dropped slightly, it may directly affect both the DMM and the battery. Can you check the voltage between the battery negative and several ground points, for example, engine ground, chassis ground, alternator case? It is possible that the only code set by the ECM might be when the charge rate drops lower than it presently appears. I know I appear to be harping on voltage drops to various grounding points, but I have repaired too many electrical and electronic problems with this procedure to count. I have seen silly stuff like this eat people's lunches and dinners. If you look at the published procedures on this posting, it also includes voltage drop testing at various points as well. I think we can solve this if we take it one step at a time, and don't overlook anything. Ray
 

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Discussion Starter #35
Something else to consider here is the temperature where you are. If the temperature there has dropped slightly, it may directly affect both the DMM and the battery. Can you check the voltage between the battery negative and several ground points, for example, engine ground, chassis ground, alternator case? It is possible that the only code set by the ECM might be when the charge rate drops lower than it presently appears. I know I appear to be harping on voltage drops to various grounding points, but I have repaired too many electrical and electronic problems with this procedure to count. I have seen silly stuff like this eat people's lunches and dinners. If you look at the published procedures on this posting, it also includes voltage drop testing at various points as well. I think we can solve this if we take it one step at a time, and don't overlook anything. Ray
Took readings for what I could... Not altenator though as I couldn't access it...
Check it out

Engine off, all accessories on for 30 seconds, then off. What voltage ___12.17___
2. Voltage across battery at idle (no electrical load) ____13.98________
3. Voltage across battery at 2000rpm (no electrical load) _____13.98___
4. Voltage across battery at 2000rpm (everything electrical switched on) _____13.94____
5. Voltage at ALTERNATOR at 2000rpm (everything switched on)___________________
6. Voltage drop between alternator body and battery negative (YES negative). Measure at max electrical load and 2000rpm ______________ (millivolts please)
7. Voltage drop between alternator positive and battery positive. 2000rpm, max electrical load _____________
8. Check Voltage drop from Battery Negative terminal to 1st groundpoint on vehicle_________0. 00V_____
9. Check voltage drop from 1st ground point to block_____0.03V_____
10. Check voltage drop from Alternator Housing to block__________

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Discussion Starter #36
At the shop now...
They tested the battery. They say it's testing strong but maybe not taking a full charge...?
They are gonna warranty it and drop in a brand new one...

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Discussion Starter #37
Using my Bluetooth OBDII dongle, I'm monitoring the voltage (Or at least what the car thinks is the voltage) while I drive. Will compare it with my multimedia this week.
So on my way home, just showing 13.7 to 13.8V.
Discouraging, considering I've seen it as high as 14.3V previously.

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wungun, sorry this diid not fix this issue. Is the battery light still on on the dash? On perusing the image you sent of the BMS, you have basically two places to locate a voltage drop. One is between the battery negative and the post of the BMS. The other is on the cable side of the BMS, between the cable side of the BMS and its post. You might first try checking between the battery negative terminal and the cable coming off of the BMS. If this drop is less than .5 volts, with the engine running, you can eliminate this as a possibility. Locating a voltage drop can be tedious, but I still think it is your source of the problem. Can you reach the alternator terminals? If so, we can do some quick and dirty check to either locate or eliminate some possibilities. Ray
 

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Discussion Starter #39
wungun, sorry this diid not fix this issue. Is the battery light still on on the dash? On perusing the image you sent of the BMS, you have basically two places to locate a voltage drop. One is between the battery negative and the post of the BMS. The other is on the cable side of the BMS, between the cable side of the BMS and its post. You might first try checking between the battery negative terminal and the cable coming off of the BMS. If this drop is less than .5 volts, with the engine running, you can eliminate this as a possibility. Locating a voltage drop can be tedious, but I still think it is your source of the problem. Can you reach the alternator terminals? If so, we can do some quick and dirty check to either locate or eliminate some possibilities. Ray
Battery light still on, yes...

Can't get to alternator terminals... Would be the next logical place to check.
I think you need to get to them from underneath??
I'm beginning to suspect a bad + cable of the alternator or a bad ground somewhere. That, or my alternator is dying slowly. That kinda makes sense as the new battery is barely making it past 12.2V charge level, same as the original battery, which triggered the charging fault.

The chassis ground point that's connected directly to the BMS/negative terminal post has 0V drop.... It's a clean connection.

Not sure if you still understand what I'm saying about the BMS negative.... It's totally integrated into the post clamp. The only two conductors that are accessible are the + feed and the LIN wire to the back of the fuse block/body control module.
See image...
Black arrow is where chassis ground attaches, red is + in, and blue is LIN.

I appreciate you helping me figure this out... It's very frustrating, especially in the dead of winter and working on the car myself is next to impossible.

Seeing as the ECU is "reading" just 13.7V with the motor on concerns me now.
I still need to verify this with a MM.
Initially, I was seeing 14+ volts (but STILL had charging system fault)

Also, see pic of what the dealer did...
Notice just the one OBD code... Nothing mentioning any alternator voltage or charging errors... (Also this is with new battery)



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wungun, I do understand what you are saying Re: BMS. Just for grins, I would like to check for voltage drops at these terminals on the BMS. Let's just check the voltage drop between the battery - terminal to the output cable to chassis ground. I know this sounds fruitless, but I have seen stranger things in my 45+ years in vehicle electronics. Should see <.5 volts. I would like to check the engine ground to battery - as well. Both of these checks should be made while the engine is running. Let's start with that. While we are running these checks, let's keep the battery charged with a trickle charger. Please keep me advised as I am convinced we can find the problem. From what I recall from your initial posts, it appears as if there are issues on the ground side of things. It is easy to overlook these things. We won't miss a trick if we stay focused. Ray
 
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