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Author Topic:   Two Dead Batteries
prxmid posted 10-02-2005 11:16 AM ET (US)   Profile for prxmid   Send Email to prxmid  
I have a 1999 Optimax, with two- one year old batteries on a Perko switch.

We usually switch between batteries one and two. Last month battery two was dead, switched to battery one, charged them both on All when running and everything seemed to be working fine.

Went out today and both batteries were dead. The last person to use the boat left the switch on Both. No electronics were left on ( Although the boat used to be on a lift and is now in the water...bilge pumps must have been working)

I can't believe it's two bad batteries after one year. Must be a short somewhere but I don't know where to begin looking.

Any help will be appreciated?

CHRISWEIGHT posted 10-02-2005 04:18 PM ET (US)     Profile for CHRISWEIGHT  Send Email to CHRISWEIGHT     

Just a start point put a multimeter in series (positive to battery plus, negative to clamp once removed from battery)

on current range and check for current drain from batteries with no electronics/ electrical load on. then unhook all the loads one by one, don't no of a better way.

regards chris

prxmid posted 10-02-2005 07:14 PM ET (US)     Profile for prxmid  Send Email to prxmid     

I just ordered a Multimeter, I'd been meaning to, now I need it. I looking for amps...what is the normal range? When I remove electronics and hit the 'bad' one What should happen.

Sorry for the naive questions, electronics are not my thing

Jerry Townsend posted 10-02-2005 09:35 PM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
prxmid - your problem is a load (electrical resistance) somewhere in one of the circuits - or a battery with a bad cell.

Some multimeters, are auto-ranging while others require the user to set the range. If yours is not auto-ranging, set the meter on current (amps) and a reasonably low current range (0.5 - 2 amps).

Connect the multimeter by removing the positive battery connector (clamp). Set up the multimeter as mentioned above. Clamp (vise-grips, the positive (normally red) multimeter lead to the positive battery post. While watching the meter's display, touch the meter's negative lead to the battery cable previously removed.

If you do not see any indication of current flow, reduce the range on the meter - until you see an indication of current flow. When you see an indication of current flow, disconnect one electrical circuit at a time - until the current flow is eliminated - that circuit is the one causing the problem.

If you do not see any indication of current flow, even with the lowest current range, the problem is probably in one of the batteries - a short across a couple of cells - or a leak to ground - internally within the battery. Take the batteries to a Sears or other automobile service store and have them check the batteries. ---- Jerry/Idaho

BobL posted 10-02-2005 10:29 PM ET (US)     Profile for BobL  Send Email to BobL     
The changing capacity of an outboard may not be able to charge two batteries at once with the battery switch on “All”. Let the outboard charge one at a time. It is also not a good idea to have the switch on “All” when one battery is at a far lower state of charge than the other. When I experienced a similar problem with new batteries it was my starter and main cable to the starter that were the culprit (causing the load and current drain). After fully charging both batteries and reinstalling them into the boat they have been fine for the rest of the season.
jimh posted 10-03-2005 02:16 PM ET (US)     Profile for jimh  Send Email to jimh     
From the information provided, there may be a stray current or parasitic drain. Also, as mentioned, if a battery has a shorted cell its terminal voltage will be about 2-volts lower than normal. This will cause a good battery connected in parallel to become discharged to the same terminal voltage.
prxmid posted 10-03-2005 09:33 PM ET (US)     Profile for prxmid  Send Email to prxmid     
So (continuing naive questions) If I hook up a voltmeter to pos and neg terminals of each, the bad battery will show two volts lower?
Jerry Townsend posted 10-03-2005 10:29 PM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
prxmid - a voltmeter will show a low voltage - if one or more cells are dead or shorted out. If there is just some internal leakage, the voltmeter will not show that condition - until one or more cells are discharged. An automotive service operation (Sears, can detect many of the internal defects of a battery. --- Jerry/Idaho
c_mccann posted 10-04-2005 06:37 PM ET (US)     Profile for c_mccann  Send Email to c_mccann     
You need to load test the batteries. Most autoparts places sell load testers ad they are easy to use. They'll tell you which of the batteries has a bad cell(s). If the batts are 1 year old, they are probably covered by a warranty, so you could go that route. Now, you need to test your electrical system for possible drains to it, I'd start with ANYTHING attached to the batteries besides battery cables to the master switch. Nothing should be hooked up before the master 1-2-all switch, so that ensures that when it is off, nothing will drain your system. The only exception could be the bilge pump, but that is a debatable item, I stick with everything hooked up after the master switch. I see boats with multiple wires coming out of the batteries and I get the willies, it is a dead battery waiting to happen.
Buckda posted 10-04-2005 06:45 PM ET (US)     Profile for Buckda  Send Email to Buckda     
Thanks for posting this prxmid. You just helped me out with a little mental battle that was waging in my mind by ending the debate regarding liklihood/possibility of losing all power in a two-battery system in my consideration of options for repower.

I'm going to vote for a dead cell in one of your batteries. When you left the perko switch open to both, the current from the good battery dumped into the second (with the bad cell) and depleted both batteries. I'd unhook and charge each battery independently. Then let them sit for a few days to find the bad one.

Good luck!


jimh posted 10-04-2005 09:02 PM ET (US)     Profile for jimh  Send Email to jimh     
The best practice with an OFF-1-BOTH-2 switch is to never leave it in the BOTH position unless needed momentarily for engine starting.
prxmid posted 10-07-2005 05:56 PM ET (US)     Profile for prxmid  Send Email to prxmid     
Thanks for the replies, if the rain ends it's a Saturday project. I'll post results
prxmid posted 10-11-2005 10:27 PM ET (US)     Profile for prxmid  Send Email to prxmid     
Well, I took the good battery out and charged it, took the 'bad ' battery back to West Marine and they checked it out, pronounced it dead- el muerto.

Pro-rated me a new one. I never got the Multi-meter so I guess I'll have to go by elimination. I'll put the new battery in and hope for the best. If #2 draws down again then one of the electronics is draining it.

However, no more leaving it on BOTH.

Jerry Townsend posted 10-12-2005 01:19 AM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
prxmid - Hopefully you have found the problem - I suspect that you have.

I, however, suggest that you go ahead a get a multimeter and play/use it enough so that you feel comfortable with using it. A suitable multi-meter will cost somewhere between $15 and $100. Check with Radio Shack, Sears or other similar stores. I don't want to be out somewhere, need one - and don't have it. That is the reason that there is a good multi-meter in my boat, RV and garage/shop. ----- Jerry/Idaho

prxmid posted 10-12-2005 02:17 PM ET (US)     Profile for prxmid  Send Email to prxmid     
Thanks for the help Jerry, et al.

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