Need Help: Troubleshooting Batteries Optimas / 8Ds

[solecollector]

Hello all -

I have been trying to track down a major problem with my battery system on a sailing catamaran. I just purchased the boat a few months ago so it is taking some time to trace everything....!

My problem is this: my batteries just don't stay charged and they don't ever charge past 11 (the starter batteries - two more 8Ds hold past 12 all the time) Now the last owner made a mistake - he added 6 marine Optima batteries to the bank of 8Ds (2 8Ds that came with the boat originally). The Optimas were purchased 2 years ago and the 8Ds are 6 years old. The entire system had very little use (engines have 800 hours and genet 200).

All of the above happens when the power comes from shore / engine alt / gen set.... three different sources and they never push the batteries past 11.

Now for some reason the previous owner connected up a few devices that are on all of the time. One of them is the 12V plug and when I removed my phone from being charged the meter jumped up last night. So I wonder if the gauge is a little off because of some items in-line? Unsure how that works to be honest.

I checked the batteries themselves and they are at 13.4 (I didn't check them individually but I did disconnect the Optimas from the 8Ds and both banks read over 13Vs). I put the ohm meter on the alt just for grins - way over 13 coming out.

The pain of it all is that the fridge can't run for even half a day and the food goes bad. The inverter alarm goes off at night because the power is so low. I actually saw an 8v on the voltmeter one day when I didn't charge the batteries. I assume that can't be good.

Any help would be great! Thanks for your time! _steve

[noelex 77]

I am a bit puzzled by some of the very different voltage you are reporting.

The problems have to be due to poor charging, poor connections, defective batteries are a combination.

Given you are having problems with several different charging sources 1. Seems unlikely.
Heat is a good indication feel all the major connections such as battery switches and the batteries themselves.
The most likely problem is a dead battery or two with a dropped cell.

You need to isolate the batteries, charge them separately and then put a load on them. I suspect you will find one, or more of the batteries will drop voltage very rapidly and severely shortly after the load is applied.

If one of the older batteries is defective I would at least ditch all the older batteries.

[pillum]

Looks like someting is discharging your system....
+++ to noelex's comments ref batteries.
Assuming the batteries are ok:
It seems you have a basic system with a lot of add-ons, first thing I would do is sketch out an as-built electrical schematic. With this you can identify each power consuming equipment, then use a current (amp) meter to monitor battery discharge, and disconnect each circuit in turn until you fine the one that is defective. Time consuming, but better to know your system now than to try to get to know it when you are at sea and s**t is happening.

[solecollector]

Thanks for the insight! I started to isolate the Optima batteries but when I found out they were fairly new I stopped. I took one out and called Optima to see when they were produced but I guess two year old batteries can get hosed as well.

[nathanp]

Agree with both above comments. Although it would be a major pain in the rear, the best thing to do would be to remove the batteries and haul them all in to the parts store for a load test. Voltage alone does not tell you much about a battery, what you need to know is how well it can handle a load. I would suspect that the 2 six year old batteries probably need replaced. You may also have something wrong with a device or wiring that is putting an excessive draw on one of the circuits as pillum said above. Good luck!

[CharlieJ]

Find a marine electrician with a Midtronics type (conductance) battery tester and have him/her test the CCA of the batteries in situ. While there is little to no direct correlation between CCA and Ahr; I maintain that a battery rated at 1800 CCA/220Ahr that tests out at < 1440 CCA (80% rated) with the conductance tester is at its end of serviceable life. By the way, the 80% number is the industry standard for determining EOL.

Or...if you need a really challenging physical workout, you can remove them from the boat and take them to a battery shop!

[ranger58sb]

Originally Posted by solecollector

I checked the batteries themselves and they are at 13.4 (I didn't check them individually but I did disconnect the Optimas from the 8Ds and both banks read over 13Vs). I put the ohm meter on the alt just for grins - way over 13 coming out.

Steve, I can't tell from your post whether you did this test with the batteries on the charger, recently off the charger, or at rest after being off the charger for a few hours. The latter gives you a more accurate volt reading; testing while on the charger or shortly thereafter generally gives you a reading of the float charge, not the battery's current state.

Also... testing a whole bank as a unit doesn't give you true insight into the state of each individual battery... so if one has a bad cell (or some other symptom), it won't show as quickly... and one bad cell could be hosing a whole bank...

I think Optimas are AGMs? And as I understand it, mixing AGMs and flooded lead acid batteries (perhaps your 8Ds?) together in the same bank isn't optimum (and each type may want different settings on your charger, depending on your actual charger).

-Chris

[solecollector]

Again - thanks all for the well thought out ideas. I'm in KW right now and will be sailing home after we watch the fireworks. Once I get back to Key Largo I'm going to start working on the problem and will update this thread. And hopefully soon - we have a solution!_steve

[svmariane]

Lots of good advice above. Something of concern: "Now for some reason the previous owner connected up a few devices that are on all of the time."

Yeah, those previous owners.... made sense to THEM at the time...

What to do? Me? Once I had her back home (in your case) I'd disconnect everything. I mean everything. (Have to buy an iggy ice chest for cold beers.) And I'd isolate one battery to one charging system, then later hook that bat up to a load. See what happens. Repeat for each bat. Get a base-line for each bat on that one charge system. Drag 'em to a bat place if needed for charging. Might end up throwing away some of those bats...

Then I'd trace ALL my wiring while the bat(s) charges. Bears repeat from above: You'll be best off knowing where every wire goes. Trace them out and make a booklet. Flashlights, ohm meter, and a helping friend if needed. Trace those wires! Might find things that need rework. Yeah - some wires might be behind woodwork or otherwise under cover. Tough. But check.

If you didn't hand-wire the boat yourself, then all sorts of things are suspect. Example: somebody splices two short lengths - and when you finally get the boat the connection has corroded. Bummer.

Note this: On my boat and only discovered while underway, once found a pwr line attached to the main pwr distro panel at one end and to nothing at the other - just dead-ended in the lazarette. But it was run near the steering cable (under the floorboards aft) and had rubbed through. Depending on boat heel, the cable would short out and suck power from my bats.

THAT decided me to trace out EVERY wire on the boat. Bunch of cable ended up in the trash; they either went nowhere or were non-marine wire. My vessel's "previous owner" will get a jolly good right cross to the chin one day...

Good luck!

James