I am loosing my mind. I tend to be very good at tracking this kind of stuff down being in the 12 volt industry for 10 years. I can test the draw on the batteries with the battery switch in the off position and I get zero draw unless the bilge pump comes on. I have the Mercathode fuses open currently. I had the boat running three weeks ago and came up the next weekend to find dead batteries. I had a heck of a time getting them to take a charge with my battery charger. I finally got them to charge up using some one elses charger so I figured my charger was bad. I went down to the boat to run it this AM after using the boat all yesterday and it barely started. Ran it for a bit and it started up fine. I do not have my load tester to check the batteries (they are brand new) but does this sound like it could be a Mercathode issue or is one of my batteries bad, or both? I want to leave the boat in the water but not at the risk of the batteries going down and the bilge pump not working!
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Batteries go dead almost over night
- Thread starter Audiofn
- Start date
Ratickle
Founding Member / Super Moderator
I'm guessing bad batteries. But I always take them out, charge them good, and have them load tested at NAPA or somewhere.
The other way is to take a different battery from somwhere you know is good. Leave that connected in the boat and see what happens while you have the other ones disconnected.
MOBILEMERCMAN
Founding Member / Competitor
New batteries go bad too. It is almost easier to buy a load tester then to pull the batteries. I think you can buy a tester for about $50.
You don't have a amp hooked to it do you. They are usually on all the time and are notorious for killing batteries.
You don't have a amp hooked to it do you. They are usually on all the time and are notorious for killing batteries.
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I bought a brand new set of Optima Blue Deep cycles a couple years back, and they were just plain bad. They would charge fine, and crank the engines no problem, but within a day or two of sitting they would be completely dead. So I returned them and swapped them out for another set, and everything's been fine ever since. I would say your batteries are toast, get a new set.
Geronimo36
Charter Member
It's silly but we've been having a LOT of rain... maybe the float switch got hung up while you were away?? I had that happen on my boat a few times.. I had an oilzorb boom down there and it must have worked itself under the float switch during a rain storm and hung the switch open. A week later when I came down to run it that battery was stone dead....good thing for parallel start! 
What kind of batteries??? As far as charging, the deep cycle batteries don't charge very well on a trickle charge, they only get a surface charge. I've always found they need a 15 amp charge first then a trickle overnight to hold the charge.
With the batterie switches in the off position I like watch for a tiny arc when connecting the cables. If you see a tiny arc, you know you have a draw somewhere...even if it's the radio memory it could be a bad radio.
I agree about testing the batterys with a load tester to know for sure! Shoot, could even be a bad ground cable connection!
What kind of batteries??? As far as charging, the deep cycle batteries don't charge very well on a trickle charge, they only get a surface charge. I've always found they need a 15 amp charge first then a trickle overnight to hold the charge.
With the batterie switches in the off position I like watch for a tiny arc when connecting the cables. If you see a tiny arc, you know you have a draw somewhere...even if it's the radio memory it could be a bad radio.
I agree about testing the batterys with a load tester to know for sure! Shoot, could even be a bad ground cable connection!
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MattBMiller
New member
I had the exact same problem in my boat. Run it one weekend, shut off the batteries and it's dead the next weekend. They wouldn't take or hold a charge. They were interstate batteries, only a year old. Replaced them both and haven't had a problem.
I have a load tester but did not have it up this weekend. I took the ground cables off each battery before I left this weekend. I will test them when I get back up there next weekend. The batteries are Die Hards. I have been turning the battery switch to the off position when leaving. I did listen for the bilge pump running in case it is a bad float
Geronimo36
Charter Member
My buddy recommended I buy the Diehards a few years ago so I did.. I would go down and work on the boat running the radio/amp and after a few weeks of doing that the battery started loosing its charge very easily and even when it was charged it never seemed to crank as well as it did when I first bought it. That winter the battery took a dump from sitting so I replaced both of them and went back to Interstate's.
Maybe it's just the batteries.
Maybe it's just the batteries.
Ratickle
Founding Member / Super Moderator
If you want to do something interesting. Go weigh a diehard top of the line, then take your scale to NAPA and weigh their best. The NAPA was 1/3 more.
Geronimo36
Charter Member
I never used the NAPA batteries, who manufactures them? Like lifters in engines there's only a few companies that make batteries for all the others.
Tony
Founding Member
I had the exact same thing happen to me. I bought one from Autozone, ran it for the weekend next weekend it was dead and refused to charge, went to the same store and exchanged it and same damned thing happened. The third time I went to a different store for the exchange and havent had a problem since.
The most reliable batteries I've ever ownerd are the yellow-bodied one's at Wal Mart. I replace them every spring and give them away to people that don't value their boating weekends as much as I do.
I have seen solid-state voltage regulators in alternators cause voltage drain. If you disconnect the battery cable and put a test light in series, it won't show up as a draw. They need more current to switch on.
I have seen solid-state voltage regulators in alternators cause voltage drain. If you disconnect the battery cable and put a test light in series, it won't show up as a draw. They need more current to switch on.
It was a bad battery... When I got he batteries I told my brother I don't know why I am buying these I have never had good luck with Dei Hards. They were the only ones that had the size I needed so I got them. Well back to Sears they go. I am going to try and get my money back but doubt that they will after 30 days.
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