Yet Another Battery Woe

[Bill Roosa]

totally correct MS

Totally agree with all your comments MS
However, I have a volt meter handy on my DC panel and I don't want to wait for 24 hours to check, heck an hour is pretty long to wait. I guess my question is how often do you "check" your batteries with a hydrometer? I check my batteries 10s of times a day while sailing and it only takes a second.
I must admit I have an alterer motive here. having a way to monitor your systems and keeping a continuous eye on them is much better than checking once or twice a year. I'm trying to promote the former. I believe they call it forhandedness. But you have to understand the systems. Plumbing and wood finishing are easy, electrical not so obvious to the new sailor.

So batteries do loose voltage for quiet a while after a charge but the major voltage loss is right after charging ends. We don't much care the exact voltage just that it has dropped or risen and if it is still dropping fast or holding steady.

The next step is to observe how batteries act under some common loads found around the boat. All loads of the same amp draw are equal. A light or a motor that draws 2 amp are the same to a battery. amps is amps. As you switch on a load you will note a drop in voltage, larger loads result in larger voltage drops. A good battery will drop voltage and hold steady. A deeply discharged or bad battery will continue to loose voltage rapidly. By rapidly I mean over the course of hours not minutes.

 

[Winkfish]

Andrew, will your engine start on just one battery? If so, is it fairly easy for you to hook the newer 4D battery to start the engine as a test? Then if the others are apparently charged, but still not starting the engine, that would be one step done.

 

[shemandr]

Update: I have pretty much decided that the two older batteries are kaput. I move the newer one into the box and wired it to the #1 wires. It wouldn't charge. I re wired it to the #2 wires. It charges and works fine. There must be a problem with the #1 wiring - maybe that's what finished off the older batteries.
Anyway, how does one test the 1,2,both battery selector switch?

 

[Winkfish]

Update: I have pretty much decided that the two older batteries are kaput. I move the newer one into the box and wired it to the #1 wires. It wouldn't charge. I re wired it to the #2 wires. It charges and works fine. There must be a problem with the #1 wiring - maybe that's what finished off the older batteries.
Anyway, how does one test the 1,2,both battery selector switch?

Did you try swapping the #1 and #2 wires to the good battery? Did you try using the #1 wires on the #2 switch post hooked to the good battery? Do you have a volt meter?

 

[shemandr]

Another update for anyone still interested:
I took out the battery switch thinking it was a likely source of a bad connection. There it was. The nut on the lug for the 1 circuit was loose - very loose. Some of the other wires on that lug were green with oxidation. There was evidence of heat damage to the shrink wrap or whatever covered the crimp. I cleaned it all up and cranked the nut down.
I'm now charging one of the bad batteries and won't be surprised if it charges. I can't explain why it didn't charge when connected to the 2 circuit - but I may have made a mistake in wiring. Next, I'll see if the other "bad" battery will charge.
The two "Bad" batteries are 8 years old but up until 2 weeks ago were performing normally.
MS: I agree that two batteries in service on the same boat have totally different histories. One season the yard didn't connect one battery when they re-installed them in the spring. I used the one battery that was wired as if I were using both. That means I ran it down way more than 50%. One morning the engine wouldn't start. A closer look at the wiring revealed the mistake. The other battery was fine having not been used at all that season. That doesn't even take into effect the times I forget to put the house feed on the same battery as is being charged.