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Old 29-10-2016, 04:29   #1
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New batteries but low voltage

I had been getting up in the morning with battery voltage of 12.2 with 60-90AH out. So since the batteries were 6 years old and I had abused them I replaced them yesterday with 4 new Trojan T105s that I charged till they accepted 9A at 14.4V. To test them I turned off shore power and went to bed. This morning they were reading 12.25V at -6.3A and -67 AH. This seems way too low based on the AH and is the same as the old batteries.
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Old 29-10-2016, 05:03   #2
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Re: New batteries but low voltage

I would say that they weren't fully charged or you have an electrical load that they can't handle. Or that your voltmeter is inaccurate.
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Old 29-10-2016, 05:04   #3
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Re: New batteries but low voltage

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I had been getting up in the morning with battery voltage of 12.2 with 60-90AH out. So since the batteries were 6 years old and I had abused them I replaced them yesterday with 4 new Trojan T105s that I charged till they accepted 9A at 14.4V. To test them I turned off shore power and went to bed. This morning they were reading 12.25V at -6.3A and -67 AH. This seems way too low based on the AH and is the same as the old batteries.
New flooded batteries don't attain their full capacity until they've been cycled a few times, say 8-10 times at least.

Moreover, the T-105s should be charged at 14.8 to 15.0VDC, per Trojan's recommendations.

The AH counter needs to be reset, and you need to check the actual voltage at the batteries with a dependable digital voltmeter....to be sure.

I'd guess the batteries were not really at full charge when you started.

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Old 29-10-2016, 05:20   #4
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Re: New batteries but low voltage

The voltage between my battery monitor and my instrument panel are agreeing. My handheld is reading a little lower so I wouldn't call it "dependable" but it is what I have.

Even if the batteries weren't at perfect full charge before I started last night I would think they would have been close. I turned off all loads and waited a few minutes and the voltage went up to 12.35 considering that they should have been around 85% SOC

I'll cycle them again, but the thing that is bothering me is that the old batteries were reading the same (and they were reading higher a couple months ago and nothing has changed really)
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Old 29-10-2016, 05:41   #5
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Re: New batteries but low voltage

I doubt if you have a real problem. Just cycle the batteries a few more times (take them down to at least 50% DOD then fully charge them). And, of course, check all your connections.

Finally, remember that voltage, per se, is NOT an indication of battery capacity, but rather of state-of-charge (SOC). It's perfectly possible to have a relatively high voltage indicating a high SOC with batteries which have greatly diminished capacity.

Also, note that measured voltage often increases after showing a level of 12.4 or so and with a modest load attached. So, don't panic....just wait awhile to be sure of what you're seeing.

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Old 29-10-2016, 06:11   #6
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Re: New batteries but low voltage

I'm not panicked (yet). My system always has read lower voltage than theory even when the last set of batteries were new. I'm just pissed that I may have replaced batteries for no reason. I need to get this done today while I'm in an overpriced slip because I don't want to listen to the generator run.
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Old 29-10-2016, 08:01   #7
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Re: New batteries but low voltage

Sounds like your charger is not working properly.
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Old 29-10-2016, 08:18   #8
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Re: New batteries but low voltage

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I'm just pissed that I may have replaced batteries for no reason.
I'm thinking you're right.

Your brain is used to lots more work and now that you are a bit isolated out there cruising you may be overthinking things

On Monday last while sailing back south across the bay, my autopilot started freaking out. It loses it every now and then so I didn't think about it.

Then it did it again an hour later while I was sailing upwind close through anchored oil tankers with an unfavorable strong incoming tide and

Later the radio went off then back on. Battery voltage looked ok so I replaced my $12.00 controller. The other one was showing no charging but the solar panel showed connection

Same problem so I separated the batteries which had been in parallel. One read 10.8 volts so I came in on the other one.

Thinking it may have been a connection problem, I charged this battery off and on last week but it wouldn't hold a charge for more than a few hours so I replaced it after it tested bad at Autozone
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Old 29-10-2016, 08:29   #9
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Re: New batteries but low voltage

Chill. You may not have any problem.

Breaking in New Wet Cell Batteries: "Breaking In" New Wet Cell Batteries
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Old 29-10-2016, 08:51   #10
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Re: New batteries but low voltage

I did a hard discharge using my inverter and an electric heater. I can definitely say from that that the new batteries hold better voltage and have more capacity based on the voltage that the batteries stayed at for the 2 hours I did this. Charging them back up now and will see what happens.
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Old 29-10-2016, 08:53   #11
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Re: New batteries but low voltage

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Sounds like your charger is not working properly.
I considered posting why I believe my charger is working just fine. But, instead I figured it would be more interesting to find out what I posted that you based your belief that it isn't.
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Old 29-10-2016, 08:54   #12
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Re: New batteries but low voltage

Exactly what one would expect :-)

It's a very common and intuitive mistake to (mis)judge battery capacity (i.e., residual AH capacity) by battery voltage. Fools a lot of people, maybe most.

I'm sure you'll find that performance actually increases as you get those new T-105s actually working.

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Old 29-10-2016, 08:56   #13
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Re: New batteries but low voltage

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...I charged till they accepted 9A at 14.4V...This morning they were reading 12.25V...
...This...
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Old 29-10-2016, 09:05   #14
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Re: New batteries but low voltage

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...This...
Terra Nova...

That's no indication that the battery charger is defective.

However, as I noted above, recommended charging voltage for T-105's is 14.8-15.0VDC. Your charger may or may not be able to be set for this voltage. Maybe the ship's alternator/regulator can be set this way??

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Old 29-10-2016, 09:23   #15
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Re: New batteries but low voltage

If you have strange readings, check the ground (earth, negative) connections, especially the connection onto the engine. Any corrosion here can mean that batteries do not charge correctly and voltage measurements can be very strange. It is worth cleaning these up at least once a year.
I have seen this on a couple of boats (engine not turning over.... flat starter battery as not charging...); cleaned up the connections and tightened. Bingo!
Good luck.
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