Dead Battery (3x in 2mths) - 30A BAT Fuse has 500mA draw - what next? (7 Viewers)

[agaisin]

Facts:
1) car wouldn't start for 3rd time in 2 months - first time was on the 7yr old original battery, second and now third time was on a new battery (that was fully charged after second issue).
1) car was last driven a few days ago
2) car wouldn't start yesterday
3) battery V reading is 6.5V
4) current draw is ~500 mA
5) draw went down to ~10mA when BAT fuse was pulled (or when short pin A is pulled but looks like BAT is downstream of short pin A)
6) multimeter being used is new, fresh batteries, good fuses and user now understands how to test V and A correctly

I chose a fresh post so I don't get bogged down in the issues with my previous attempts at diagnosis.

From my basic attempt at reading the EWD the BAT fuse comes off the short pin (and other things come off short pin too) so that should mean the BAT 30A fuse is the real issue and whatever comes after BAT 30A fuse must be causing the draw. I can't figure out what that is though so I'm not sure what next. Anyone have an idea what could cause a drain like that coming off the BAT fuse and where I should look etc?

I did searching and couldn't find much so I guess this isn't a common issue. Would love some advice.

Thanks!
Art

 

[liveoak]

i see you have an 05 and it is stock. does that mean totally stock? no aftermarket radio, lights, alarm, winch, trailer brake module, lojack etc...

 

[agaisin]

Only aftermarket items are Vaistech Modules for satellite radio and ipod.

However, since I identified the BAT fuse as the source of the draw, I would expect that to narrow the focus to whatever comes downstream of that 30A BAT fuse, right?

Also - I know it seems logical to assume BAT means Battery but I am not so certain of that. Can anyone confirm from EWD what runs off the BAT fuse?

 

[agaisin]

Well - if I'm reading the EWD correctly, the BAT fuse doesn't seem to have anything to do with Battery as (I) expected. The Dome, ECU-B2 and RADIO fuses come off that (each 10A). I pulled each and it looks like the ECU-B2 fuse is the source of the draw.

Great - but the ECU-B2 is the anti theft system and I don't know what's normal draw since it is one of the few things that should be drawing current even when the car is off.

If all the above makes sense, would love tips on how to troubleshoot the ECU-B2 current draw.

 

[liveoak]

did you drive the truck after replacing the battery? is it possible your alternator went out instead of the battery and when you drove it the battery drained? if alternator is ok i would disconnect those sat/ipod modules and start there. good luck.

 

[Sandroad]

A couple of things. First, that’s a very unusual low battery voltage reading. A completely discharged battery will read around 10.5 volts and the 6.5 volts you found is weird. You wouldn’t be the first person to buy a new battery that was defective with an internal short right off the shelf. However, if your reading of a ½ amp load is correct, that will also discharge a standard battery to about half capacity in 6-7 days. I can’t figure out anything useful from the ’04 EWD or the FSM, other than replacing things downstream of the ECU-B2 fuse that you measured as causing the draw.

 

[agaisin]

I'm probably just back to square one here - the .5A drain is only initially and then it goes down to ~30mA. Every time I pulled the BAT fuse and put it back it would 'reset' and go to .5A for a short period (30 seconds). If I sit there long enough that goes down to 30mA. I haven't sat there long enough to study the pattern and can't find any details in the FSM on whether .5A is ever normal and what the pattern is...

did you drive the truck after replacing the battery? is it possible your alternator went out instead of the battery and when you drove it the battery drained? if alternator is ok i would disconnect those sat/ipod modules and start there. good luck.

liveoak, to answer your questions:
- After the first battery replacement, I never tested the battery's state of charge b/f installing it and I do not know if it was fully charged after driving it - I don't remember exactly how much I drove it but it was definitely not more than once or twice/week.

After the second dead battery, I definitely fully charged it with a proper battery charger using the documented settings (it's a diehard platinum p5 battery and I used a sears diehard platinum charger with a special setting for their diehard platinum battery line). It took hours to complete charging. I verified it was very fully charged (~at least 12.7V iirc). However, I did not drive it more than once a week after that and possibly only short trips. In some cases my once a week could have been a <10 minute trip.

Regarding the sat/radio, if the radio fuse had no effect on the current draw does it make any sense to look there?

A couple of things. First, that’s a very unusual low battery voltage reading. A completely discharged battery will read around 10.5 volts and the 6.5 volts you found is weird. You wouldn’t be the first person to buy a new battery that was defective with an internal short right off the shelf. However, if your reading of a ½ amp load is correct, that will also discharge a standard battery to about half capacity in 6-7 days. I can’t figure out anything useful from the ’04 EWD or the FSM, other than replacing things downstream of the ECU-B2 fuse that you measured as causing the draw.

Sandroad:
- agree, 6.5V scared me. I charged it and it appears to be holding it's charge 2 days later at 12.75V after starting her up for a few minutes since. Technically fully discharge is 10.5 (1.75V per cell), and mine was at about 1V per cell. I don't know if I should replace it or not since it appears to be holding it's charge at this point? I have found some generic information about the advantages of AGM over flooded - for example typical flooded is considered bad if it dips below 10.5 and can't recover from that, but AGM apparently can handle deep discharges, just haven't found any concrete information about just how low it can go b/f it can't be fully recharged...

-regarding the .5A reading, I looked again and I definitely get it intially, but after 30 seconds or something it goes down to 30mA for an extended period. Only thing is I can't find details in the FSM about how much current is normal, and what the cycle is for the anti theft system. So I'm guessing this is not a real parasitic draw, and just the anti theft system doing it's thing.

- Furthermore, regarding your math:
I have a Diehard Platinum P5 with the following specs (Sears: Online department store featuring appliances, tools, fitness equipment and more)
59 Amp Hours
100 Minutes Reserve Capacity
740 CCA

For interest's sake, the OEM group size is 27F I believe, which is larger than the 35 that Sears maps our trucks to. Also interesting is that the Diehard Gold comes in a 27F, the Diehard platinum does not appear to, so they map us to the next closest (in their book) which is group 35.

The 27F Diehard Gold has 165 Minutes Reserve Capacity vs. Diehard Plat Group 35's 100 Minute Reserve Capacity...

If I had a constant .5A draw (I don't), with only 59AH, I believe the battery would be drained at about 5 days. With the OEM Spec 27F or better, presumably I'd have 8.5 days (assuming .6*165 = 99Ah = .5A*24*8.5 = 8.5days).

Also, it seems to be common knowledge that AGM batteries require higher charging voltage than conventional wet cell batteries, and combine vehicles that weren't specd for AGM with high mileage alternators that aren't necessarily performing at their peak, I wonder whether that is a factor.

Also, I don't know what's normal for an LX470 that isn't driven daily. They are luxury cars with lots of battery drain - tilting steering wheel, running board courtesy lights, daytime running lights, all the other normal stuff light dome lights, radio, anti theft system, etc.

Even with a tip top alternator and a flooded battery, if I'm not driving the vehicle enough (what's enough...) will I need to either:
1) disconnect negative cable during the week (ghetto)
2) get a battery tender and use it during the week (my LX is not parked in the garage so this is a PITA)
3) get a battery kill switch so I disconnect the negative cable from within the cabin during the week
4) get a solar trickle charger


I don't know what I should expect in terms of how long/often I need to drive it to keep the battery charged. I would love to hear some anecdotal info from others that don't daily drive their LX or LC - how infrequently do they drive with no issues?

 

[liveoak]

did you verify the alternator was good? simple test is to carefully disconnect (neg)battery while truck is running if it stalls it's bad if it keeps running is probably good.

driving with a bad alternator and a fully charged battery you could make it quite a few miles and would definately run the battery voltage down. if you're only driving short trips you could make it back home without the battery ever getting a charge. then you go to start it the next day and it won't start because of the high demand of the starter.

this is only my theory based on what i've read so far. you never said if you checked the new battery voltage after you drove it.

 

[mobi-arc]

DO NOT LIFT THE GROUND CABLE WHILE THE VEHICLE IS RUNNING.

This is the easiest way to blow out the alternator's rectifier. This was a common way of testing your Grand Daddy's generator but NOT on alternators.

NOT GOOD ADVICE.

did you verify the alternator was good? simple test is to carefully disconnect (neg)battery while truck is running if it stalls it's bad if it keeps running is probably good.

driving with a bad alternator and a fully charged battery you could make it quite a few miles and would definately run the battery voltage down. if you're only driving short trips you could make it back home without the battery ever getting a charge. then you go to start it the next day and it won't start because of the high demand of the starter.

this is only my theory based on what i've read so far. you never said if you checked the new battery voltage after you drove it.

 

[agaisin]

DO NOT LIFT THE GROUND CABLE WHILE THE VEHICLE IS RUNNING.
This is the easiest way to blow out the alternator's rectifier. This was a common way of testing your Grand Daddy's generator but NOT on alternators.
NOT GOOD ADVICE.

^^^^ What he said. The FSM specifically says not to do this (bullet #4 in the Charging System Precautions) and almost every modern article I've read says not to do this.

did you verify the alternator was good? simple test is to carefully disconnect (neg)battery while truck is running if it stalls it's bad if it keeps running is probably good.

driving with a bad alternator and a fully charged battery you could make it quite a few miles and would definately run the battery voltage down. if you're only driving short trips you could make it back home without the battery ever getting a charge. then you go to start it the next day and it won't start because of the high demand of the starter.


this is only my theory based on what i've read so far. you never said if you checked the new battery voltage after you drove it.

Liveoak - thanks for your input. Here's more info to address your points:

I did verify the alternator is good in two ways:
1) had it tested at local auto store (after second dead battery) and it showed that battery, alternator and starter all tested good.
2) The spec in the FSM says 13.2-14.8V is within spec etc.

Today as I took it out a few times and checked the voltage after driving (short trips) and it was always above 12.7V.

The auto store's test verified that the starter's draw was within acceptable range. Furthermore, I saw that my voltage dropped only ~1.25V while starting (ie. multimeter read 12.84 with engine off, then 11.58 was the minimum reading while starting).

 

[AimCOtaco]

agaisin,
I would try and put a full slow charge into that AGM so you have no doubt about it's initial state and I would also consider the mod where you bump up your charging voltage. 12.7 is a tad low, combine that with the higher voltage requirements of the AGM and lots of rest time and that might be enough to cause your problem.

30mA for the security system sounds about right. I would be willing to bet the 500mA surge comes at the beginning because there are probably a number of filter capacitors in the electronics charging up and in addition the system may power up for a self test and then fall to the idle 'watch' power level. I don't think that is enough to be your problem. I think calculating draw down time was a good way to verify that the 30mA should not be an issue for the huge battery.

 

[slimbuddha]

I don't know what I should expect in terms of how long/often I need to drive it to keep the battery charged. I would love to hear some anecdotal info from others that don't daily drive their LX or LC - how infrequently do they drive with no issues?

It is the norm for me to only drive my '99 once or twice a week, and only for a 5-10minute drive, and also very common for it to sit a week between drives. I have a Toyota battery that is about 6 years old, and I have not had one problem starting it due to the battery.

 

[agaisin]

agaisin,
I would try and put a full slow charge into that AGM so you have no doubt about it's initial state and I would also consider the mod where you bump up your charging voltage. 12.7 is a tad low, combine that with the higher voltage requirements of the AGM and lots of rest time and that might be enough to cause your problem.

30mA for the security system sounds about right. I would be willing to bet the 500mA surge comes at the beginning because there are probably a number of filter capacitors in the electronics charging up and in addition the system may power up for a self test and then fall to the idle 'watch' power level. I don't think that is enough to be your problem. I think calculating draw down time was a good way to verify that the 30mA should not be an issue for the huge battery.

Thanks - a few things:
1) 12.7 was the Voltage at the battery with the engine off. So that is actually perfect battery voltage. It would be low with the Alternator running and would indicate a bad alternator. But with the engine on my Voltage is all within spec. It's initially >14V, then goes down to about 13.6/13.7 at 2krpm and while at cruising speeds and on the low end it goes down to ~13.3ish around town and idling. That's what I've observed so far.

2) regarding draw - <50mA is acceptable by every standard I've seen and is definitely not enough to drain a battery. Actually to do the math at 0.03 Amps (30mA) it would take ~82 days to deplete a 59 Amp hour battery (.03A * 24 hours * 81.94 = 59 Amp hours). So 30mA is definitely not a problem but if I did have a constant 500mA draw that would be a problem. Fortunately I don't.

It is the norm for me to only drive my '99 once or twice a week, and only for a 5-10minute drive, and also very common for it to sit a week between drives. I have a Toyota battery that is about 6 years old, and I have not had one problem starting it due to the battery.

Great data point - thanks!
Any one drive this infrequently with AGM Batteries (with a Diehard Plat P5 Group 35)?

 

[AimCOtaco]

Thanks - a few things:
1) 12.7 was the Voltage at the battery with the engine off.

DOH! Sorry, misread that.

I NEED an answer to your problem! I can't think what else to check! Sounds like your doing all the right things but something has been missed. Don't take this wrong but you did verify the no-starts were low battery and not just starter contacts right? ( i have not read your old thread )

Your battery terminals are also perfectly clean and tight right? Often I find bad batt connections where the high current will flow for starting etc, but the connection is bad enough that no charging takes place. 'Yota terminals are good but lack range in my opinion so after a few cycles they don't tighten very well, have used brass shim stock to improve the tension on occasion.

Good luck!

 

[agaisin]

DOH! Sorry, misread that.

I NEED an answer to your problem! I can't think what else to check! Sounds like your doing all the right things but something has been missed. Don't take this wrong but you did verify the no-starts were low battery and not just starter contacts right? ( i have not read your old thread )

Your battery terminals are also perfectly clean and tight right? Often I find bad batt connections where the high current will flow for starting etc, but the connection is bad enough that no charging takes place. 'Yota terminals are good but lack range in my opinion so after a few cycles they don't tighten very well, have used brass shim stock to improve the tension on occasion.

Good luck!

That's how I feel about it too - I would prefer to know something failed so I can replace/repair it rather than guessing/theorizing. So - thanks for feeling my pain and helping to troubleshoot.

To answer your questions:
1) I believe I can say with confidence that my no starts are due to low battery rather than starter contacts. The reason is b/c for certain this third time I read the voltage and it was stupid low, and also b/c once I juiced up the battery it started fine. I have not yet seen where my battery was full SOC and it wouldn't start.

2) Certainly for the second and third times the battery terminals were tight. I have not cleaned the terminals b/c in each case my battery was dead. Although the posts are new and clean the cables could definitely be in less than perfect shape. I assumed if it is starting through the cables it is charging through the cables. If what you're saying is true that high current at startup flows and charging current while driving doesn't, then that is an interesting twist.

 

[liveoak]

sorry about the bad advise, guess i need to get up to date.

 

[2000UZJ]

DO NOT LIFT THE GROUND CABLE WHILE THE VEHICLE IS RUNNING.

This is the easiest way to blow out the alternator's rectifier. This was a common way of testing your Grand Daddy's generator but NOT on alternators.

NOT GOOD ADVICE.

My ground lead came off while driving the other day. I did not notice until it failed to start. Everything seems fine, drove 300+ miles with no issues. I tightened it back down. Just wondering if I should keep an eye on anything.

 

[AimCOtaco]

My ground lead came off while driving the other day. I did not notice until it failed to start. Everything seems fine, drove 300+ miles with no issues. I tightened it back down. Just wondering if I should keep an eye on anything.

If you're still charging ok after re-connecting it then you have not damaged the alternators rectifiers and probably have nothing to worry about.

 

[Trunk Monkey]

Somewhere, and I can't for the life of me remember where, I read that AGM batteries are a royal PITA to charge. Normal charges don't work or something. They may charge, but won't hold it, etc. Maybe it's all the folks I know that try to save a dead 2 year old Optima through charging and they never come back.

If you can verify that the battery is holding a charge and recharging through the alternator then I'd start looking for a drain somewhere. It could be some accessory that is wired bad and is staying hot with the truck off.

 

[mobi-arc]

No worries. Lifting the ground doesn't guarantee a blown rectifier, but it creates a load dump scenario and it's possible to blow the rectifiers. May not blow them, but it can depending on various conditions.

sorry about the bad advise, guess i need to get up to date.

Agreed. Losing ground doesn't absolutely mean you'll blow the rectifiers, but it can so it's generally not a good practice to purposely lift the ground and create a load dump.

If you're still charging ok after re-connecting it then you have not damaged the alternators rectifiers and probably have nothing to worry about.