Weather change and battery drain

by JiMi_DRiX Wed Jul 03, 2013 2:26 pm

I have this weird problem with my 76 Monte that I have noticed the last year or two. Usually this time of year, we finally get our first rain, or at the least it rains somewhere nearby and the humidity goes up. It seems that every time the last couple years, the battery in the Monte is low, and it isnt enough to get it to start, and I have to get the jumper box out. I dont get it? I start and drive the car often enough, it should be fine. The battery isnt very old either, and it is a gold top Duralast. Any ideas why this would happen? Or is it just an odd coincidence?

by JB2wheeler Wed Jul 03, 2013 3:02 pm

Does your clock work? When mine still worked and I would leave it parked for a good while the clock would draw the battery down some. Now that my clock no longer works (probably needs lube) I no longer have that problem. JB

by thatfnthing Wed Jul 03, 2013 3:07 pm

Mine used to do weird things when it was cold and damp -- I came out once to find my dome light on for no reason. Just one of the reasons I rewired the entire car. Smile

To find a drain:

1. Make sure everything electrical is turned off in the car.
2. Disconnect + cable from battery.
3. Set your multimeter for DC volts.
4. Hold the red test lead from the multimeter against the + battery post, and the black lead to the + battery cable end you just disconnected, so that the meter bridges the gap between the two.
5. Any voltage reading on the multimeter is your drain. Anything more than 0.1 volt needs to be investigated.
6. To find it, start pulling fuses one by one from the fuse box and recheck -- if the voltage disappears, the problem is in that circuit.
7. Be sure to check non-fused circuits (such as the alternator feed and horn relay) by disconnecting them -- I once had a crappy alternator that would drain the battery back through the main feed when the car was off.

Love to hear what you find!

by Mcarlo77 Wed Jul 03, 2013 3:25 pm

You have some unique weather conditions down in your part of the country that I'm told wreaks havoc on batteries. My folks have lived in the Phoenix area for nearly 20 yrs now and my dad says he routinely has to replace his battery every 2-3 yrs...regardless of brand or quality. The extreme summer heat is harder on a battery than our cold Midwest winters. Are you saying that the rest of the year, it starts just fine? Doesn't your "monsoon season" generally coincide with the hottest time of the summer? Before you go chasing all over the car with a volt meter, have you taken steps to assure the charging system and battery are fine? Don't assume just because the battery "isn't that old" that it's healthy.

Start with the basics and check your voltage on the battery next time it doesn't start. Unfortunately, I have found that a weak battery isn't always uncovered by what seems to be an adequate voltage reading. Confirm your voltage output from the alternator once you jump start it. My next step would be to put it on a battery charger. Usually, that will reveal if there's a bad cell within by how it fails to fully charge.

by JiMi_DRiX Wed Jul 03, 2013 4:15 pm

I'll have to get a multimeter and check for a draw. My only other idea is my alternator. I have a few added accesories (MSD ignition, Electric Fuel Pump, and a small stereo amp). Maybe the alternator isnt keeping up, and the short drives I make every other week or so isnt enough to juice the battery back up enough? It still doesnt explain the humid weather coincidence though.
Yeah the heat here is very rough on batteries out here, but my 76 doesnt get drive in the heat much, and is in covered parking, so the heat isnt QUITE as bad on it.

I dont know the stock rating of the alternator. Anyone have some suggestions for a bit stronger one?

by thatfnthing Wed Jul 03, 2013 11:27 pm

Get the biggest amperage you can afford. Alternators are one place where bigger is always better, since they will only produce what the given electrical load at the time requires. But if the load exceeds the alternator's total capacity, the system will have to supplement the load with battery power.

The other consideration is how many amps the alternator will produce at idle. For example, a 100 amp alternator produces 100 amps at a decent RPM (usually above 1500 RPM, but it varies). At idle, however, it will produce much less. Here's where quality comes into play -- a good one might produce 60 amps at idle and a crappy one might produce only 30 or 40. Ever stop at night and notice the headlights get dim? This is because the alternator is not spinning fast enough to produce enough juice to power all the loads on it, and you are now supplementing with battery power. Step on the gas, the alternator spins up, and the headlights get bright again.

I have a ton of electrical stuff, with more on the way, so I splurged on the Powermaster 140 amp unit, and even got an overdrive pulley to boot to make sure I have enough juice at idle.

by 77mali Thu Jul 04, 2013 5:45 am

Just as an FYI, the stock G3 Alt is 61 amps (Chevelle anyway). I just got a new one rated at 65 as I plan to pretty much keep the electric, A/C stuff stock. If I had done any type of upgrades I would have def. gone w/ more amps.

Heat is a killer on batteries, is your batt the type that you can add distilled water to? They actually expand & contract with extreme fluctuations in temp & humidity. In the winter I will be keeping mine in the basement where it's always a pretty constant & cool temp.

by JiMi_DRiX Fri Jul 05, 2013 2:31 pm

thatfnthing wrote:Get the biggest amperage you can afford. Alternators are one place where bigger is always better, since they will only produce what the given electrical load at the time requires. But if the load exceeds the alternator's total capacity, the system will have to supplement the load with battery power.

The other consideration is how many amps the alternator will produce at idle. For example, a 100 amp alternator produces 100 amps at a decent RPM (usually above 1500 RPM, but it varies). At idle, however, it will produce much less. Here's where quality comes into play -- a good one might produce 60 amps at idle and a crappy one might produce only 30 or 40. Ever stop at night and notice the headlights get dim? This is because the alternator is not spinning fast enough to produce enough juice to power all the loads on it, and you are now supplementing with battery power. Step on the gas, the alternator spins up, and the headlights get bright again.

I have a ton of electrical stuff, with more on the way, so I splurged on the Powermaster 140 amp unit, and even got an overdrive pulley to boot to make sure I have enough juice at idle.

Thanks! I didnt know you could just go big, and it not be a problem. The stock Monte alternator said its 63 amps. I dont remember if my current one is upgraded or not, its been a long time since I put an alternator on that car. After I check for a draw, I'll probably start with the alternator.

Off topic, thatfnthing, do you have more pics of your car? It looks like it has a nice stance! I'm looking for springs/shocks for my 76 to get the stance a bit lower.

by thatfnthing Fri Jul 05, 2013 3:29 pm

Thanks! Got a few in the Gallery. There's a few more in the DSE Lowering Springs thread of the transition. I used the DSE springs all the way around with Belltech 2" drop shocks, PMT trailing arms, and PST polygraphite bushings up front. Made a huge difference.

Mark

by JiMi_DRiX Fri Jul 05, 2013 11:48 pm

thatfnthing wrote:Thanks! Got a few in the Gallery. There's a few more in the DSE Lowering Springs thread of the transition. I used the DSE springs all the way around with Belltech 2" drop shocks, PMT trailing arms, and PST polygraphite bushings up front. Made a huge difference.

Mark

I forgot that was your car! I really like the stance. Your setup might be too low for me though. I have long tube heads, and 275/60/15s on the rear. I think as long as I can get the nose down some, it will look good though. The rear isnt bad at stock height. Do you have any suggestions for lowering just the front? How should I do it from your experience?

by thatfnthing Sat Jul 06, 2013 2:20 pm

JiMi_DRiX wrote:Your setup might be too low for me though. I have long tube heads, and 275/60/15s on the rear. Do you have any suggestions for lowering just the front? How should I do it from your experience?

Well, every car will be different, especially if it's not stock, and I can only really speak for mine. My front end is now so low I can't get the floor jack under the front crossmember. Smile

Luckily my Tri-Y's don't hang low.

I guess for yours I'd start by asking myself:

1. What's the lowest part now in the front (headers, crossmember, etc), and how much can I drop it before it becomes a concern?
2. Is the front suspension stock?
3. Are my tires close to rubbing anywhere now, and how far down can I go before they do?

If you can only afford to go down a little bit because of low-hanging parts, you may just consider lower profile tires. If you can go more, there are dropped spindles ($$$), lowering springs, or good-old fashioned coil cutting (though obviously some guys here have tried that with mixed results). The DSE springs I got said they would drop the front about 1.5". I actually got a lot more drop because the springs I had in there were apparently way too tall. If your front suspension is stock, I would expect you'll probably get something closer to the spec'd 1.5".

by dynchel Sat Jul 06, 2013 5:15 pm

I cut one coil off of my "way to tall" front coils and it dropped appx 1 inch. I considered it a success, no cash outlay and maybe two hours work. I would like to go lower but my exhaust is two close to the ground now. Mad

by pila Sat Jul 06, 2013 9:42 pm

You might try un-hooking the alternator while the car sits, & see if it makes a difference. A bad diode in the alternator might possibly be bleeding some battery power off.....
We are actually luck to have simpler cars, electrically, compared to late models, which can be electronic nightmares...

by JiMi_DRiX Mon Jul 08, 2013 11:14 pm

I got the multimeter out and did some testing. At first I was screwing it up because I was leaning against the car? The batter was at 11.8v. My stereo amp which is connected straight to the battery seems to have a draw of 11.8, but can that seriously be correct? I pulled the fuse and it went away. But I have a draw on the battery though the positive cable of 11.8 too. I pulled the stereo fuse, AC fuse, the fuel pump power, trunk light power, alternator plug, and the draw did not go away.

its been a while since I've done any electrical system testing. Am I doing something wrong?

I did start the car without any problem.

by Mcarlo77 Tue Jul 09, 2013 12:39 am

How long has the car been sitting since last driven? As you probably know, a fully charged battery at rest should be giving you more like 12.8v...not 11.8v. With car running, should be getting a reading upwards of 13.5-14V from alternator. You haven't revealed whether you have confirmed battery becomes fully charged after driving it...or, whether you're getting a healthy output from the alternator. If, in fact, you get home from driving it and it reads fully charged, but drains down to 11.8v within hours or overnight, now you can assume there is a drain somewhere...and, the fun begins chasing that down.

by JiMi_DRiX Tue Jul 09, 2013 1:35 am

true! I need to drive it around the block and check the voltage. with it running my gauge is reading 13-14. is there a way to check the starter for a draw without pulling it off the car? I have one of those mini hi torque starters.

by Cale11 Tue Jul 09, 2013 1:56 am

Did you say Duralast? I know nothing, but I do know if its not Interstate or Delco, It probably is inferior to begin with, just my take.

by JiMi_DRiX Tue Jul 09, 2013 2:25 am

Its a Duralast Gold Top.

by Cale11 Tue Jul 09, 2013 2:27 am

Dont they sell Duralast at Wal-Mart? And im not knocking you for owning one, heck the Laguna I just bought may have one in it lol, just saying, never heard of a Duralast being mentioned in the same sentence with high quality is all. Delco is the best, then Interstate, then I couldnt tell you.

by 77mali Tue Jul 09, 2013 7:04 am

Just curious but did you check all your ground wires? I have a brand new battery & it reads 13.1 volts on the multimeter. Check the engine bay grounds & there are a few under the dash as well. I'd start there.

by dynchel Tue Jul 09, 2013 7:34 am

Cale11 wrote:Dont they sell Duralast at Wal-Mart? And im not knocking you for owning one, heck the Laguna I just bought may have one in it lol, just saying, never heard of a Duralast being mentioned in the same sentence with high quality is all. Delco is the best, then Interstate, then I couldnt tell you.

Duralast is auto zones house brand. Flush

by thatfnthing Tue Jul 09, 2013 9:16 am

JiMi_DRiX wrote:I got the multimeter out and did some testing. At first I was screwing it up because I was leaning against the car? The batter was at 11.8v. My stereo amp which is connected straight to the battery seems to have a draw of 11.8, but can that seriously be correct? I pulled the fuse and it went away. But I have a draw on the battery though the positive cable of 11.8 too. I pulled the stereo fuse, AC fuse, the fuel pump power, trunk light power, alternator plug, and the draw did not go away.

Okay, dumb Q: How many other wires do you have connecting to the + terminal on the battery besides the main cable?

Assuming you're testing like I mentioned earlier (i.e. put the meter in between the + battery terminal and the cable), they will each need to be tested this way. While amplifiers and computers and such will require a constant trickle to maintain their settings, it should be a fraction of a volt. If something is pulling 11.8 volts through the main cable while everything is supposed to be off, you're going to have to keep disconnecting things until the draw disappears off the meter. Don't forget the horn relay and the main alternator feed, also -- these do not have fuses, so the only way to test them is to disconnect them. When the draw disappears, you're on the right track -- put the fuse or connection back and see where those wires go -- start disconnecting things along the way until you get to the specific piece of equipment that's causing it.

If there's really a concern about the battery itself, try this test. How quickly does the battery die when it's all hooked up? A day? Two? Unhook everything from the + terminal and let it sit that long -- if it dies anyway, it's bad. If it maintains power, you have a draw to chase down per the above.

It can be a pain tracking down electrical issues, but it generally boils down to plain old process-of-elimination.

by Mcarlo77 Tue Jul 09, 2013 11:13 am

Jimi...are you sure you aren't confusing draw with continuity when taking readings? In other words, if you took a reading at the battery post and again where the cable connects to the starter for example, you're going to get a similar, if not same, reading (assuming the cable is in good shape). You're only testing continuity...not draw. Logic tells you that if something were really "drawing" 11.8 volts, your battery (at rest) would be dead within an hour or so. That's why it's imperative that you determine whether your battery is healthy before moving forward with diagnosing a slow draw-down of voltage.

By the way, I think the Walmart brand of battery is Ever-Start. Thought I remembered reading that Consumer Report actually rated it as above average in quality.

by Cale11 Tue Jul 09, 2013 12:20 pm

I might have to go look at whats in my car now, it starts every time and I think its some cheesy cheap battery like that.

by JiMi_DRiX Tue Jul 09, 2013 10:26 pm

Yeah its a Duralast Gold Top. They are good batteries, the last one in the black 73 back when my dad was daily driving it lasted over 5 or 6 years out here.

So I must be doing something wrong, hell, I dont know what. The only GOOD i found was that when running, the alternator is cranking it up to 14v. The batteries water level was a little low, so I filled it up, drove it around, put some fresh gas in her and came back home.

Heres a picture of what I'm doing.. setting the multimeter to DCV, and putting it line with the disconnected + terminal, and this is my reading. The reason why I think I'm doing something wrong is that I get the same kind of reading doing the same test in the other Monte.

(this picture is before I filled the battery and drove around. after the short drive I was at about 12.4)

Weather change and battery drain 20130709_180026_zpsf8e15b77

Weather change and battery drain 20130709_180026_zpsf8e15b77

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