Dead Battery Questions?

[caliguyinTN]

Last weekend I installed a system in my boat. Sub, 2 amps, 2 6 1/2s. During install we killed the Interstate deep cycle having the light on under the bow from about 5 pm until 1 am and having the ignition on plus testing the system once we got it wired up. I bought a jump start box to get us going the next day and that was fine. It took some time for the alternator to charge the battery but by the end of the day it was fine. No starting problems with the stereo on while floating but didn't have the boat off with stereo on for very long.

Well this weekend I stopped by the storage unit where the boat is to install a new headunit. When I got there the battery was dead again. The light can only be on with the ignition on so it couldn't be the light. Is the battery toast? or do I need to get it on a charger? I thought the alternator would have charged it up using it last weekend so charging it on a charger wouldn't be necessary. I'm not sure how old the battery is. I e-mailed the previous owner. I thought the new system might have drained it but with the ignition off all week, no power to the headunit means no power to the amps. Any ideas. Sorry for the long message.

[Diesel]

Take the battery somewhere and have it tested. If you have a fluke it is very easy to determine if you have any draw on the battery with the key off. If you do trace it back to the source and eliminate.

It is possible you killed the voltage regulator on the alternator while jumping, which can drain a battery at rest.

[caliguyinTN]

Take the battery somewhere and have it tested. If you have a fluke it is very easy to determine if you have any draw on the battery with the key off. If you do trace it back to the source and eliminate.

It is possible you killed the voltage regulator on the alternator while jumping, which can drain a battery at rest.

How do I determine if there is any draw on the battery with the key off? How do I check to see if the voltage regulaor is shot? So is it bad to jump start a dead boat?

[Leroy]

You can measure amps if you have a VOM meter by putting in series with the positive lead. Take off the positive lead from the battery and put the positive lead of the VOM on the battery and the negative lead on the cable from the battery. Make sure the VOM is in at least 10Amp mode. Make sure everything is off that you know of.

On your battery, I learned from JimN that everytime you kill the batter you lose about 50% of the power. There are battery conditioners that can recover some of that lost power. My battery charger has a "recondition" mode in it and I used it on my battery at the beginning of this year and it worked miracles on it.

[caliguyinTN]

You can measure amps if you have a VOM meter by putting in series with the positive lead. Take off the positive lead from the battery and put the positive lead of the VOM on the battery and the negative lead on the cable from the battery. Make sure the VOM is in at least 10Amp mode. Make sure everything is off that you know of.

On your battery, I learned from JimN that everytime you kill the batter you lose about 50% of the power. There are battery conditioners that can recover some of that lost power. My battery charger has a "recondition" mode in it and I used it on my battery at the beginning of this year and it worked miracles on it.

So I remove the positive battery cable from the battery and I take the positive lead from the VOM and place it on the positive terminal on the battery and put the negative lead of the VOM on the postitive battery cable I took off, there shouldn't be any reading with everything off? if there is, then I have to find what device is draining the battery?

also, since the battery was dead twice in one week, should I buy another or buy a battery charger that will recondition it? I think first i'm going to see if the battery will hold a charge and see if there is something draining the battery. This has never been an issue until I added the 2 amps and sub. The grounds from the amps are grounded to the battery. Until yesterday when I crimped on 2 terminals to the cables, they are just wing nutted on to the battery. would a bad ground like that cause the drainage?

[Leroy]

Yes, and anything connected to the +Battery terminal. The reading should be at most a few milliamps. If you meter is auto ranging watch it might auto range and show 20 or 40 but the units will be milliamps. If it stays in milliamp range you should expect 1000 or more. If in the amp range expect 1-5 amps. The radio and other microprocessors will draw a few milliamps in standby. I would guess you have something drawing ~1 Amp. Find and fix you problem before you buy a new battery ;)

You probably have something connected in the on position, maybe connected +12V where you should have had a switched +12V. Bad ground would not cause that current draw.

My battery is 3 years old and I killed it on first outing (from leaving lights on) none of the dash lights would come on. After reconditioning it has been strong the rest of this summer.