[67_LS1]

Because I decided not to run a BCM with my engine swap, my alternator runs at 13.7 volts all the time, which I thought would be enough. But roughly every 6-8 months my battery goes dead. Really dead. It takes a 24 recharge to revive it.
How can I find if there is a tiny electrical drain? I have no clock or radio. Nothing that is “on” all the time. I now use a trickle charger all the time but what a pain in the a$$ fir a car I drive everyday.
Help!

 

[billdini]

Although 13.7 (mine is about 14.4v) is a little low that shouldn't be a cause of a dead battery. Are you using a lead battery or an AGM? I would likely think you have a intermittent short that shows up every 6 months or so. If you battery was getting slowly dead you would notice it in your starting power as it gets closer to being dead. Also every time a lead acid battery is killed fully it loses about 10-15% capacity unless it is a deep cycle battery.

 

[blm]

Hook your multimeter in line with the negative battery terminal and the negative battery cable. Set the meter on amps. You xhould see a draw on the meter. Then one at a time pull a fuse and check if the draw is gone. If not replace the fuse and try the next one. If it is gone you know what circuit is causing the draw.

 

[67_LS1]

Although 13.7 (mine is about 14.4v) is a little low that shouldn't be a cause of a dead battery. Are you using a lead battery or an AGM? I would likely think you have a intermittent short that shows up every 6 months or so. If you battery was getting slowly dead you would notice it in your starting power as it gets closer to being dead. Also every time a lead acid battery is killed fully it loses about 10-15% capacity unless it is a deep cycle battery.

It does exhibit weakness a few days before it’s dead. A little harder starting.
I do have an ECM that is powered all the time.
The battery is lead acid.
I just found a device that will let me turn up the voltage, but it will still be fixed.

Hook your multimeter in line with the negative battery terminal and the negative battery cable. Set the meter on amps. You xhould see a draw on the meter. Then one at a time pull a fuse and check if the draw is gone. If not replace the fuse and try the next one. If it is gone you know what circuit is causing the draw.

Thanks. I’ll try this.

I would love to find a voltage regulator swap for my alternator. It’s a Denso but has a very specific case that actually bolt to the block. I’ve seen lots of VR swaps but not on this model.

 

[billdini]

How many time has this battery been killed. How old is it. The battery itself could have an internal short as well. Have you isolated this battery with another. I do agree with Brads test above but most DVM's do not have the amp capability and you may have to buy or borrow a higher power amp meter to measure.

 

[marcrose]

Anything more than 2 milliamps parasitic draw will cause battery to drain over time.6-8 month interval is not parasitic draw unless its very intermittent. Put a quick disconnect on your battery and use it,if its ok then the battery is the problem.

 

[billdini]

Anything more than 2 milliamps parasitic draw will cause battery to drain over time.6-8 month interval is not parasitic draw unless its very intermittent. Put a quick disconnect on your battery and use it,if its ok then the battery is the problem.

I think you meant if the battery still dies after being disconnected it is the battery itself.

 

[B52bombardier1]

Is your PCM powered up with operating power all the time or simply PCM memory "keep alive power" all the time? Which type of PCM? With the key off, your PCM should only have memory keep alive power which is a very, very small drain.

Have you tested the rectifier diodes in your alternator for AC volts leakage to ground?

Rick

 

[Bob Tiley]

If you have an ECM (Computer) that is the draw on your battery, you answered your own question. I would suggest using a battery disconnect switch or disconnecting the battery cable before you store it for several months or just start it up and run it every few weeks.

 

[Dean]

parasitic_drain.pdf (chevelles.net)
currentdrain.pdf (flashoffroad.com)

 

[kmakar]

If you have an ECM (Computer) that is the draw on your battery, you answered your own question. I would suggest using a battery disconnect switch or disconnecting the battery cable before you store it for several months or just start it up and run it every few weeks.

Bob nailed it. Put the ECM on a relay that only powers on when the key is turned on.

 

[67_LS1]

The battery was in the car just under 2 years. I know this because I took it back as I have three other times and said I thought the natter was junk from day one.
So last Wednesday the battery was replaced with new.
Today I tried to start the car...dead as a door nail. Checked the voltage and it reads 3.2 v.
So what was one a small drain has turned into something bigger.
I’ve got it on a 2 amp, 24 hour charge but not sure it will come back from that low.

 

[kmakar]

The battery was in the car just under 2 years. I know this because I took it back as I have three other times and said I thought the natter was junk from day one.
So last Wednesday the battery was replaced with new.
Today I tried to start the car...dead as a door nail. Checked the voltage and it reads 3.2 v.
So what was one a small drain has turned into something bigger.
I’ve got it on a 2 amp, 24 hour charge but not sure it will come back from that low.

2 amps is much too low. Should be on at least 10 amps to 15amps to try and bring it back. After it gets to 90%, then you can drop it to 2 amps.

 

[67_LS1]

2 amps is much too low. Should be on at least 10 amps to 15amps to try and bring it back. After it gets to 90%, then you can drop it to 2 amps.

I just remember that when I would bring it back to Batteries Plus where I bought, they would put it on a slow charge for 24 hours. It always brought it back but I was never under about 10 volts.
In addition to a draining issue I’m beginning to think the constant 13.7 volts isn’t going to cut it long term. Can I remove the internal voltage regulator and bring out the rectifier leads out to an external regulator. Similar to what the car had originally???

 

[kmakar]

I just remember that when I would bring it back to Batteries Plus where I bought, they would put it on a slow charge for 24 hours. It always brought it back but I was never under about 10 volts.
In addition to a draining issue I’m beginning to think the constant 13.7 volts isn’t going to cut it long term. Can I remove the internal voltage regulator and bring out the rectifier leads out to an external regulator. Similar to what the car had originally???

I'm not sure. That's a good question (that I'm not qualified to answer). I just know wet batteries and the only possible way to save it when it's gone that low is to "shock" it. In the solar charging world it's called a bulk charge (to 90%) then absorb (to 100%), then float (thereafter). An alternator should be putting out over 14 volts when charging (between 14.3v and 14.7v) when bulk charging. How many output amps is your alternator? I bought a clamp DC amp meter (looks identical to a standard ac amp meter, but mine does both ac and dc) to check for drain, but it also works well to see what the charge rate going to the battery is. The volt output is key, but amperage is just as important.

 

[67_LS1]

I'm not sure. That's a good question (that I'm not qualified to answer). I just know wet batteries and the only possible way to save it when it's gone that low is to "shock" it. In the solar charging world it's called a bulk charge (to 90%) then absorb (to 100%), then float (thereafter). An alternator should be putting out over 14 volts when charging (between 14.3v and 14.7v) when bulk charging. How many output amps is your alternator? I bought a clamp DC amp meter (looks identical to a standard ac amp meter, but mine does both ac and dc) to check for drain, but it also works well to see what the charge rate going to the battery is. The volt output is key, but amperage is just as important.

Because my alternator is PWM and I’m it running a BCM, it has defaulted to 13.7 volts. No matter the load = 13.7 volts. Amperage I don’t know and I don’t have a clamp for my Fluke.

 

[kmakar]

Because my alternator is PWM and I’m it running a BCM, it has defaulted to 13.7 volts. No matter the load = 13.7 volts. Amperage I don’t know and I don’t have a clamp for my Fluke.

13.7 will never do it. It would be great if it were like the old GM alternators that you could rebuild and had is own charging and regulator built in, and all you had to do was excite it to get it charging.

Just read this... maybe you can start there?

How to make a PWM alternator work? - LS1TECH - Camaro and Firebird Forum Discussion

Conversions & Swaps - How to make a PWM alternator work? - Hi, I need some infos about LS/Truck PWM alternators. When did GM started to install these on Corvettes, Pontiacs and on trucks? I read that '05 an up truck alternators are PWM ones. Camaro 2010 and up is PWM as well. What is needed to...

ls1tech.com

 

[67_LS1]

I’ve read that before. It’s kinda what I have now.
There is another one, I’ll try and find a link, that shows you how to use a small PWM generator to adjust the duty cycle up to get more than 13.7. I may try that.
Once I find what’s killing it.
I also just checked my charger that has been on all day..nothing. Then I remembered an old trick to get a charger going on a really dead battery.: Connect another good battery. Chargers won’t even turn on to a 3.6 v battery but if you put 12 v there it will turn on and hold the voltage after the other 12 v is removed. I jumped the battery from another vehicle, reconnected the charger and it’s holding above 12 volts @ 20 amp charger input.

 

[67_LS1]

Here is a link to the post about using a PWM Signal Generator to adjust the voltage output. I ordered one on eBay. This should fix the charge issue (fingers crossed).
I still need to find an amp clamp for my Fluke.

2 pin 2006 + alternator. Don't throw it away!! - LS1TECH - Camaro and Firebird Forum Discussion

Conversions & Swaps - 2 pin 2006 + alternator. Don't throw it away!! - I just swapped the regulator in my alternator from 4 pin to 2 pin, so now it's like a 2006 or newer alternator. Why??? Because GM thinks it's better than the older 4 pin one and they must know something. Oh but everyone says...

ls1tech.com

 

[Hotwire]

Here is a link to the post about using a PWM Signal Generator to adjust the voltage output. I ordered one on eBay. This should fix the charge issue (fingers crossed).
I still need to find an amp clamp for my Fluke.

2 pin 2006 + alternator. Don't throw it away!! - LS1TECH - Camaro and Firebird Forum Discussion

Conversions & Swaps - 2 pin 2006 + alternator. Don't throw it away!! - I just swapped the regulator in my alternator from 4 pin to 2 pin, so now it's like a 2006 or newer alternator. Why??? Because GM thinks it's better than the older 4 pin one and they must know something. Oh but everyone says...

ls1tech.com

I don't know that you'll find an add on clamp unless your fluke is set up for it? I've got a 78 and wish I could get a clamp for it. Unfortunately the clamp meters at hazard fraught are gaining my attention.. Don't have to have dead nuts accuracy, a ball park would be ok with me.

Good luck on the PWM retrofit. I was going to say, if you have any electric motor/generator rebuild places around you I'm sure they could reconfigure what you have to work, but then you're stuck going back to them if the alternator stops. The ebay fix makes it easy to get off the shelf parts..