Battery not staying charged

I have a 1996 Toyota Celica, and have had trouble maintaining my battery charge. If I do not drive the car for 8 days, I have to recharge the battery. I have a 1200 watt amplifier in the trunk. Could this be draining my battery. I’ve been told that I need to get a trickler battery charger or battery tender that can stay connected to the battery to boast the charge, or a capacitor for the amp. Does anyone have any experience with the battery chargers/tenders? Are they safe. What do you all recommend? Thanks

How old is the battery? If it’s over three years old it might be a good idea to replace it. Car starting batteries are not designed to be deeply discharged and recharged. It shortens the battery’s life.

You also might want to check for parasitic draw off the battery as the vehicle sits. To do this, remove the negative battery cable and connect a test light between the battery post and the negative cable. If the light comes on there’s a parasitic draw on the battery. To determine what circuit is causing the draw, remove the fuses one at a time. When a fuse is removed and the light goes out, that’s the circuit that’s causing the parasitic draw.

If you think you need a battery tender, here’s good one


This is the third battery I have had in this car in two years. When the battery that came with the car when I purchased it would not stay charged, I replaced it with a cheap battery. When it would not stay charged, I put a heavy duty battery in. I’m still having the same problem. So, based on what you’re telling me, if I get a trickle battery charger, or a battery tender, the battery will stay charged, but the battery life will be shorter. Is there any danger keeping these connected? Thanks again.

Rather than trying to keep batteries charged, maybe it would be a good idea to look for the cause of the problem rather than just patching the result.

My guess is you either have a problem with the charging system or you have a parasitic drain that is draining the battery when the engine is off.

That large amp could be the problem. It could be causing a parasitic drain or drawing so much power that the charging system can’t keep up.

1200 watts is pretty big if you have it cranked up most of the time. Has this 8-day thing been happening the entire time you’ve had the car or is it something new?

1200 watts at 12 volts is 100 amps. Your car has a 70 amp alternator, unless you have upgraded it to a heavy duty alternator. Therefore, with the amp cranked up, you are discharging your battery as you drive, even at highway speed.

Aside from that, the main power lead to the amp is always hot, and you may indeed have a 50mA drain or greater that discharges your battery when you park the car for extended periods. You can test that theory with a meter. Remember that you have to leave the ammeter connected for several minutes before you can read the drain.

My daughter has a Pioneer CD changer in the trunk of her BMW, and she has to unplug it if she is parking the car for more than a couple of weeks, because it will drain the battery in about 4 weeks.

Beads: I can’t exactly remember when this problem started, but it has continued for at least 4 years and 3 batteries. This is actually my son’s car, who is away at college, so it doesn’t get driven much. It’s been in a warm climate, but we are about to ship it to him in a colder climate, so I’m afraid the cold weather might add extra burden to the battery.

Manolito: So, if I upgrade to a heavy duty alternator, should this solve my problem, or do I need to get a smaller wattage amp? Would my regular auto mechanic be able to check this, or do I need an electrical specialist? Roughly what would a heavy duty alternator cost? Thanks for your help.

Going from your previous statements Katrice, there is a excessive current drain on the battery while the car is parked. Even a new battery and alternator will not help fix that. The source of the trouble needs to be tracked down. This is normally done by monitoring the current drain with a ammeter and pulling fuses one at time to see what fuse leg has the excessive current drain on it. Once the fuse leg is pinned down then the devices that are tied to that leg are looked at. A good shop should be able to track the trouble down without too much difficulty.

Electrical systems in todays vehicles normally draw a small amount of current to keep things running in the car, like memories. Normal current draw for most vehicles is between 20-30 milliamps I believe. You should be able to park a car for at least a month before a good battery will start to get low on charge. You can keep a charger on the battery to keep the charge level up but the best thing to do in my opinion is to fix the real problem so you don’t have to do that.

Okay… so I took the car to my mechanic and he isolated the various fuses. He said that the AM2 fuse was the one that was drawing the extra amps. I think he said it measured 130 on his ammeter. He said that this fuse was wired to the ignition switch and starter, and felt that the problem was with my cars security alarm system. He thought the alarm system was somehow wired into this. He also felt that if we changed the alarm system out, it would fix the problem, but that they didn’t do that type of work at his shop. None of the other fuses were drawing anomaly high. Does this all seem plausible to you all. I don’t want to spend a lot of money for a new alarm system to find out I still have the problem. I appreciate all of your advice!

Why don’t you perform a test and unplug the alarm module and see if the batery goes dead?

You’re welcome for the help.

I looked at some service data and it shows fuse AM2 alright and it goes to the areas he stated. The data shows that in order for that fuse to get power the headlight relay must be turned on. It also shows that the power cannot go further until the ignition switch is turned on so something must have been added to that leg and something is turning on the headlight relay. The headlight relay coil is controlled through the ground side of the coil and that runs to several areas. One looks to be a controller for the DRL lights so there may be a problem with that.

By pulling the headlight relay out and checking to see if the extra current drain stops it will show you if you are on the right path. If the current does go down to a normal level then the ‘head’ relay coil circuit will need to be checked for the trouble source.

At this point I doubt the alarm system is causing the trouble but further testing will determine that for sure.

My mechanic checked the am2 fuse with the security alarm enabled and it was drawing 137 mA. When he disabled the alarm it was drawing 30 mA. I haven’t had any problem with my headlights that I know of. I’m scheduled to put a new alarm system in tomorrow. Could it really be the headlight relay as you suggest. I would really hate to put this money into a new alarm and still have the same problem. Thanks for your advice.

The way I see it you have two problems:

The first is that amplifier…if you’re cranking it up it’s straining your charging system and perhaps even you battery. The battery is in the circuit, and it’s passing current like a wino passes pee. And it may be slowly getting weak as you drive.

The second is that aftermarket alarm system. These are known to cause all variety of problems, and it sounds like yours is a parsitic drain on an already stressed battery. Do you really need this?

It sounds to me you have found the trouble since removing the alarm system dropped the current draw to 30ma. That is a normal current level for other systems to maintain memory. Don’t worry about the other things as it appears they aren’t a problem. You should be good to go. It would be nice to know what kind of current draw the new alarm system puts on the battery. Hopefully no more than another 25ma of current. I like to use 80 milliamps as a maximum current draw limit when a car is parked and things are in the sleep mode.