I've been using the Duralast Gold (track record with AGM hasn't been good) and seems the one in my G35 isn't holding a charge anymore. Shouldn't be down to 63% capacity after a day. It was at 100% when I took it off the charger yesterday. Still starts but much lower capicity and I know it won't. The AGM lasted not quite 2 years and now the Gold apparently after a year.

The original head unit was replaced under warranty by the original owner due to battery drain. No issues after that according to the stack of receipts I got with the car. Alternator is working, after 10 minutes with the charger on, battery was at 66%, in less than half that time with the engine running it was up to 74%.

We went through two of the same gold batteries on my wife's Escape too. Like my car, during that time it wasn't driven every day and often short trips. It took a 3rd battery to get it to sit more than 4-5 days and still start. And now she has a 20 mile round trip commute so it's being driven more. The one in my Accord has been fine, I think its 3 years old now, even if I don't drive it for several days (like when I go out of town), it fires up like I just turned it off.

I talked to my mechanic and he says he has problems too. Batteries just aren't lasting like they used to. Doesn't matter who he gets them from. Anyone else dealing with this? AutoZone is great about replacing them but its a pain to remove the battery (especially on these cars!), take it there, leave it long enough to charge then load test, go back, get the new battery, swap it in and reprogram the audio system.

 

AGM batteries are only good for vehicles equipped with stop/start technology, otherwise they're junk because they are EXTREMELY prone to early failure compared to a regular old flood battery.

Try to find an actual BATTERY STORE in your area, not a parts house. The battery stores carry batteries that are worth purchasing, you won't need the warranty with a good battery because it will just work.

Obviously Optima has some great quality assurance on their batteries but they are double the normal cost of a battery, Odyssey, DieHard, Champion, and Interstate are good reliable brands, XS Power has been the industry standard for extremely high output audio systems for a long time but they're an AGM battery due to the high discharge nature of high power audio systems when the engine isn't running.

The ACDelco AGM battery has been a good one, oddly enough the NAPA house brand batteries are good also, these two are your most budget (while still being reliable enough for daily driver use).

Don't automatically blame the battery though, if you DO have a parasitic draw on the car it's INCREDIBLY hard on the battery and WILL cause premature failure. Disconnect your negative battery terminal and put one probe of the multimeter on the battery post, the other on the negative terminal. With the meter set to DC ohms (if it's manually ranged set it on the 20m or 200m, not the upside down letter u ones). I don't know exactly what the draw should be but usually somewhere around 15-30 milliohms is usual, if it's more than like 100m then you probably have a parasitic draw. Since you're eating batteries like it's going out of style I'm guessing you have a LARGE parasitic draw maybe even a full amp or more (might need to change the range on the meter to a higher range).

If you do have a bigger than like.. 100milliohm (not sure what's actually acceptable spec, might need to google that one) then find a way to tape the meter leads into place while you go through and start pulling fuses one at a time to find out what circuit is leaking power.

If you need me to go test the inherent current draw on my car I can do it sometime this weekend. Then you will have something to compare against.

 

I'll check the draw today or tomorrow. The battery in the car when I bought it and replaced it later was 4 years old so if a draw developed it was after I got the car. Obviously no draw on my wife's SUV, because she can now leave it several days with no issues with the 3rd battery.

It's also cooled off here, which is what tends to finish off batteries. It's always winter when they give up. Also going to check the water level, I know that can cause problems. Battery was at 88% last night around 9 pm, this morning, 12 hours later, 70%. Letting the car run with the charger on got it to 84% in a couple minutes which is considerably quicker than just with the charger.

I know part of the problem is I really only drive it nights and weekends. And many drives are 3-4 miles each way, headlights on so its probably not running long enough to really get charged up, exacerbating the problem.

Also look into a battery store vs AutoZone, just hate eating a $200 battery on this because they will replace it for free vs buying one elsewhere. But may not have a choice.

 

You should be able to get a good battery from a local battery specialty store for around $150.

Also make sure you only ever put distilled water into a battery. Otherwise the insulating water is now conductive due to minerals, that is pretty much the quickest way to destroy a battery aside from just crossing polarity or leaving it discharged.

Just to make sure you're aware of how a battery works, there are 6 separate 2volt (nominally rated) cells, each has two metal plates that are slightly dissimilar metals that are separated by distilled (or demineralized) water. When you draw power from the battery it creates heat on those metal plates, the water is to keep the plates cooled, it MUST be distilled or demin water otherwise the plates will try to pass electrons to each other directly through the water if it's just tap water which is conductive.

If the water level gets too low the top of the plates start to oxidize because they stick up above the water, there can also be insufficient cooling on the plates but it's not usually heat that destroys the battery. The plates will oxidize even inside the water but it's a fairly slow rate that is accelerated based on the temperature of the battery, more damage is caused during the summer months.

The dissimilar plates become more homogenous as they deenergize, they're always TRYING to have the same amount of electrons on the opposing plates, when the battery is fully discharged the two plates have achieved a perfect homogenous state. Once the two metals become homogenous it becomes increasingly difficult to make them "more dissimilar" i.e. take a charge.

This is why a parasitic drain is so damaging to the battery, it's causing a severe discharge (making the plates homogenous) and each time it loses a little bit of it's ability to become dissimilar. The electrochemical reaction of passing electrons also becomes much harder to do because the temperature also affects the chemistry reaction.

Take a hot cup of water and dissolve a tsp of salt, measure the amount of time it takes. Now take a COLD glass of water and try to dissolve the same tsp of salt, it takes significantly longer with the cold water because temperature plays a substantial role in a chemical reaction.

The reason the battery appears to die during the winter is actually because of the damage caused during the summer months, however in the winter time the CRANKCASE OIL is much much thicker when cold and THAT is the big culprit for the battery appearing to die during the winter. It's just a lot harder to turn the engine over with cold thick oil.

New batteries for critical work situations (nuclear reactor spare batteries for backup systems) are typically kept in a refrigerator for storage because they last longer at lower temperature, they should be warmed up before use though.

 

Yeah, heat hurts batteries, cold finishes them off. Definitely hear you on the distilled water. Adding water was pretty common in the olden days and they would always say "distilled water only".

I'm wondering if the huge puddle I went through on Wednesday has anything to do with this. Because it was just before I turned onto my street, didn't realize how deep the water was (probably 6 inches) and I hit it pretty hard. Went down my street and parked in my garage. That night we went out to eat, set my alarm and the horn blared continuously. Unlocked the door with the key, started my car and it turned off the horn. Hit the alarm again, horn kept blaring, so restarted it to turn it off so ended up just locking the car with the key. While we were there, I googled the issue and there were two threads about it. Both ended up with dead batteries in the morning. And no solution (one thread here, OP never came back to say how the problem was fixed) either. When we left, it seemed like my car started a little slow. Got home, put it on the charger, it was at 12.2 volts and 56% charged. Next morning it was fully charged and alarm was working correctly. Didn't drive that day and next morning it was 12.3 volts and 63% charged.

Today I had charged it to 91% and then moved it out of the garage while detailing a customer's car (I'm mobile but he didn't have a good place to do it where he lived) and my car sat outside mostly in the sun. After finishing 3+ hours later, I started my car and moved it back to my garage, put the charger on it and it was still at 90% and it quickly (on the charger) got up to 98%. Wondering it maybe everything just needed to dry out? Hard to do that in an enclosed garage. I'll keep an eye on it to see how much I may be losing per day.

Still going to see if there is excessive draw and check the water level to be sure.

 

Yes you can definitely have a parasitic draw from harnesses getting wet. Just making a guess I would say... maybe the primary harness for the IPDM is wet, not sure though since most of the systems in the engine bay, horn, headlights, etc are all de-energized with the ignition off. But the horn blaring and not responding definitely makes me think water shot back up the battery box drain and got the IPDM harness wet since that's where the horn relay is and the IPDM has many energized components even with the ignition off.

 

Personally I would pop the battery box cover, get a fan on it to blow in air overnight just in case there was moisture that got up into that area.

Might be completely unrelated to that puddle though, you might just have a clogged drain that's getting the IPDM wet.

 

I'll check that too but I did drive through torrential rains in Tennessee in September on my way to see my brand new granddaughter in Cincinnati and everything was okay. Raining so hard I stopped early for the night in fact. It was pretty miserable!
I'll set up the fan in my garage to blow on the battery box area. Greatly appreciate the help!

 

The only other thing under the vehicle that could perhaps be an issue is the positive battery lug down on the starter, considering that you're having electrical issues in general (particularly with charging) you should clean up both ends of both cables just to rule that out as a potential issue.