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Old 22-09-2016, 00:58   #1
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Battery Test?

Can someone please instruct me on how to test my house battery bank to find out if our eight Trojan T-105 batteries need replacement?

Three weeks ago at anchorages and while motoring I could only bring them up to 71% of their damaged 370 max amp hours. As soon as I got back to a dockside mooring and plugged the boat back in to shore power, they came back up to 100% within 20 hours. The batteries are now 4.5 years old. The Trojans now seem to be working and holding a charge much like they did back in May at the beginning of the season.

I have a voltmeter, but don't know how to test.
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Old 22-09-2016, 03:09   #2
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Re: Battery Test?

Open circuit voltage (batteries disconnected) on a fully charged t105 according to Trojan's website should be 6.37 volts and the specific gravity should be 1.277.

When was the last time you equalized the batteries?
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Old 22-09-2016, 03:13   #3
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Re: Battery Test?

Bulk charge rate should be 14.82 volts and the equalization charge should be 16.2v. Float should be 13.5v. If you are not attaining these voltages when charging you are not fully charging the batteries.
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Old 22-09-2016, 03:53   #4
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Re: Battery Test?

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Originally Posted by undercutter View Post
Bulk charge rate should be 14.82 volts and the equalization charge should be 16.2v. Float should be 13.5v. If you are not attaining these voltages when charging you are not fully charging the batteries.
I've never equalized the batteries, how do I accomplish and test for all this? I hired an electrician three years ago to do this work and show me how to maintain everything, but the guy turned out to be an incompetent.

I guess I need to start over.... We have a Magnetronic DCC 4000 battery control system onboard.
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Old 22-09-2016, 03:54   #5
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Re: Battery Test?

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Originally Posted by Kenomac View Post
Can someone please instruct me on how to test my house battery bank to find out if our eight Trojan T-105 batteries need replacement?

Three weeks ago at anchorages and while motoring I could only bring them up to 71% of their damaged 370 max amp hours. As soon as I got back to a dockside mooring and plugged the boat back in to shore power, they came back up to 100% within 20 hours. The batteries are now 4.5 years old. The Trojans now seem to be working and holding a charge much like they did back in May at the beginning of the season.

I have a voltmeter, but don't know how to test.
Ken,

How exactly was the 370Ah capacity determined? What was the discharge rate, what temp were the batteries at and what was the cut off voltage?

Eight T-105's should deliver considerably more, approx 900Ah's as a 12V bank. If your 900Ah bank could only deliver 370Ah, and if the testing was done correctly and accurately, then you are due for a bank replacement.

With flooded batteries, on cruising boats, I look to start replacing them at around 80% of "as new" and for coastal cruising I will let them go as low as 70% of "as new" but below this we start losing cells and having cell balance issues considerably more regularly. In a shore side off-grid solar application I will let them go as low as 60% (stationary no vibration). If your bank is 12V then your batteries are well beyond end of life.
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Old 22-09-2016, 04:03   #6
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Re: Battery Test?

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Ken,

How exactly was the 370Ah capacity determined? What was the discharge rate, what temp were the batteries at and what was the cut off voltage?

Eight T-105's should deliver considerably more, approx 900Ah's as a 12V bank. If your 900Ah bank could only deliver 370Ah, and if the testing was done correctly and accurately, then you are due for a bank replacement.

With flooded batteries, on cruising boats, I look to start replacing them at around 80% of "as new" and for coastal cruising I will let them go as low as 70% of "as new" but below this we start losing cells and having cell balance issues considerably more regularly. In a shore side off-grid solar application I will let them go as low as 60% (stationary no vibration). If your bank is 12V then your batteries are well beyond end of life.
We hired an electrician three summers ago to program our battery control system and instruct me on how to maintain everything, but when he was finished nothing made sense. He'd fully discharged the battery bank at the time and set 370 amps as the 100% value for the monitoring system. He told me that because the monitoring system was not properly programmed at the time the batteries were replaced buy the English shipyard, they were damaged. I'm now doubting this was true. It seems like the batteries have more capacity than what we were led to believe.

The bank is comprised of eight 6v batteries in a 24v configuration designed to provide 450 amp hours.
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Old 22-09-2016, 04:15   #7
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Re: Battery Test?

Not sure about the controller but doesn,t look like it regulates charging? What type of charger/inverter do you have? Is it one unit or are they separate?

Batteries should be equalized semi annually depending on how you use your batteries. If you typically draw your batteries down to 50% or less then equalizing is not required as often as your are charging at a higher amperage which tends to help keep the plates clean. If you only draw your batteries down slightly on a regular basis or are plugged in to shore power for long periods then equalizing is mandatory.

I agree with Mainesail that the 370ah is low but this number is usually input into the monitor manually by the user. Sounds like someone miscalculated the total ahr rating for your setup which as Mainesail says should be 900ah which is exactly what mine is with the same configuration. I try to draw my batteries down to at least 60% before charging whenever possible although some will disagree. It is all about cycles but I believe that these batteries are good for about 5000 cycles, 100% discharge and recharge cycles that is although you never want to draw your batteries down more than 80%.

Give us some input on your charger/regulator and we can probably offer suggestions on how to accomplish equalization and adjust for proper charging voltages.
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Old 22-09-2016, 04:22   #8
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Re: Battery Test?

Others are likely more knowledgeable than I but I suggest that you take specific gravity readings from each cell as well as test open circuit votage for each battery when disconnected after fully charging. Some say to leave the battery rest for 2 hours after charging and disconnected so that you are not reading surface charge.

A little research on line will explain how to test for specific gravity and the tools required.
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Old 22-09-2016, 04:42   #9
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Re: Battery Test?

The battery charger is a Mastervolt 24/50 and I've included a photo of what the indicator lights look like after five days of being plugged into shorepower.
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Old 22-09-2016, 05:21   #10
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Re: Battery Test?

Ken,

Unfortunately you're going to need to conduct your own capacity test.

Discharge Load - 450Ah / 20 = 22.5A

Run this test with batteries between about 73F and 80F

Start a timer and run the 22.5A load. Try to keep the load as constant as possible at 22.5A. As voltage falls so will current, unless you are running it though a constant power source such as an inverter.

Run the 22.5A load non-stop until battery voltage hits 10.5V. Look at your timer when the batteries hit 10.5V. If the bank ran for 15 hours your current Ah capacity is 75% of new.

Recharge to 100% SOC immediately and follow up with a 2 hour EQ.

This is best done at the dock.
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Old 22-09-2016, 05:48   #11
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Re: Battery Test?

Ken,

Quickly reading the manual you must ensure that the dip switches for your charger are set on traction to get close to the required voltages. It looks like even those settings are a bit low however they are adjustable if you have a remote controller in the system. Also there is the capacity to equalize the batteries with this charger however the factory setting for this feature is set to off. Again this is changeable with the remote controller. I strongly suggest that you check the settings of the dip switches to ensure that they are set correctly. If they are all set to off then they are not correct. dipswitch 2 should be set to on for Trojan with all the rest off.


I believe your amp hr setting should be 450 for this 24v system.

You definitely need to equalize your batteries if they are 4 years old and it has never been done. You will need a remote controller to do this.
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Old 22-09-2016, 07:10   #12
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Re: Battery Test?

Hey guys, he is talking about a 24 volt system. 375 amp on a 450 amp system is not wonderful, but does not mean scrapping them all out before finding out if a simple adjustment of his charging system might make it better. Sitting down and really studying the manuals might show up the problem. Ken, Best of luck. Grant.
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Old 22-09-2016, 07:13   #13
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Re: Battery Test?

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Hey guys, he is talking about a 24 volt system. 375 amp on a 450 amp system is not wonderful, but does not mean scrapping them all out before finding out if a simple adjustment of his charging system might make it better. Sitting down and really studying the manuals might show up the problem. Ken, Best of luck. Grant.
Could I politely ask you to learn the difference between Amps and Amp hours before offering advice on electrical matters?

Amps v Amp hours v Amps/Hr
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Old 22-09-2016, 08:11   #14
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Re: Battery Test?

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Could I politely ask you to learn the difference between Amps and Amp hours before offering advice on electrical matters?

Amps v Amp hours v Amps/Hr
However, the point is that with the bank configured as 24V, there are 450 amp hours to be had, not 900.
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Old 22-09-2016, 08:16   #15
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Re: Battery Test?

Going to finish my potatoe chips, then open up the manuals and read them.

Thanks for all the help.
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