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Old 03-02-2012, 09:55 AM   #41
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RE: Understanding my genset alternator

BD, thanks for that web site. I'll sit down tonight and read through that, good stuff.

One of my battery banks is not accepting a charge. When I arrived at the boat the other day, the batteries were fully charged reading about 13.6 volts with the charger on. I turned the charger off and after 2 hours with no DC load, the No 2 bank read 12.6 volts and the No 1 bank read 13.2 volts. I'm going to disconnect the 2 batteries on the No 2 bank and test them individually by again charging them to full capacity and then testing after 2 hours off the charger and no load. The batteries are 2 years old from West Marine and if I determine one or both are bad I'll try to get pro-rated new ones. Is my thinking correct??
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Old 03-02-2012, 10:07 AM   #42
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Understanding my genset alternator

Quote:
timjet wrote:
BD, thanks for that web site. I'll sit down tonight and read through that, good stuff.

One of my battery banks is not accepting a charge. When I arrived at the boat the other day, the batteries were fully charged reading about 13.6 volts with the charger on. I turned the charger off and after 2 hours with no DC load, the No 2 bank read 12.6 volts and the No 1 bank read 13.2 volts. I'm going to disconnect the 2 batteries on the No 2 bank and test them individually by again charging them to full capacity and then testing after 2 hours off the charger and no load. The batteries are 2 years old from West Marine and if I determine one or both are bad I'll try to get pro-rated new ones. Is my thinking correct??
*How do you know there was no load.* Just because it doesn't read on your meter doesn't mean there was no load.*

With nothing on check if there is any current flowing by disconnecting at the battery and using a hand held meter between the battery and the B+ wire* or cable. Check that something isn't directly connected to the B+ of that bank and isn't going through the battery cable or connected the other B+ of the two battery set.* PO's do strange things. *Another way is to charge them to full 13.6V and then disconnect the ground on that set of batteries.* let them rest for a time and then see where they are before connecting them back up.* They may just surprise you.


-- Edited by JD on Friday 2nd of March 2012 11:08:54 AM
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Old 03-02-2012, 10:26 AM   #43
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RE: Understanding my genset alternator

Quote:
timjet wrote:
BD, thanks for that web site. I'll sit down tonight and read through that, good stuff.

One of my battery banks is not accepting a charge. When I arrived at the boat the other day, the batteries were fully charged reading about 13.6 volts with the charger on. I turned the charger off and after 2 hours with no DC load, the No 2 bank read 12.6 volts and the No 1 bank read 13.2 volts. I'm going to disconnect the 2 batteries on the No 2 bank and test them individually by again charging them to full capacity and then testing after 2 hours off the charger and no load. The batteries are 2 years old from West Marine and if I determine one or both are bad I'll try to get pro-rated new ones. Is my thinking correct??
You might just be looking at the surface charge on the 13.2V bank.* Like JD says, there may be a small unknown load on the 12.6 bank.* Besides, 12.6 is a full charge.* Take a look at the specific gravities of the cells to confirm a weak cell.

If you don't have a battery monitor to watch loads and charges, and the banks are identical, and if you have the time and inclination, you could swap the batteries in the 2 banks which will allow you to clean up the terminals and tighten all connections in the process.* If the low voltage stays on the same bank, you have a persistent load and your bbatteries are fine.
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Old 03-02-2012, 10:27 AM   #44
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RE: Understanding my genset alternator

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JD wrote:*How do you know there was no load.* Just because it doesn't read on your meter doesn't mean there was no load.*
*I don't have a DC amp meter. I had just turned off everthing DC. But you're right there could have been something powered and I was unaware of it. I'll disconnect the batteries after a full charge and check them again after 2 hours.
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Old 03-02-2012, 10:33 AM   #45
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RE: Understanding my genset alternator

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FlyWright wrote:
You might just be looking at the surface charge on the 13.2V bank.* Like JD says, there may be a small unknown load on the 12.6 bank.* Besides, 12.6 is a full charge.* Take a look at the specific gravities of the cells to confirm a weak cell.

If you don't have a battery monitor to watch loads and charges, and the banks are identical, and if you have the time and inclination, you could swap the batteries in the 2 banks which will allow you to clean up the terminals and tighten all connections in the process.* If the low voltage stays on the same bank, you have a persistent load and your bbatteries are fine.

*It looks like they charged to 75%. I'll check again after disconnecting each battery from the bank.
<h3>SOC (%) vs. OCV
the battery State Of Charge vs battery's Open Circuit Voltage</h3>
An easy method to estimate the State of Charge (SOC) of the battery is by measuring its Open Circuit Voltage (OCV). This measurement should be made after the battery has been at rest for a minimum of four hours with the battery shut off from its charging source and load. The voltage is listed as Volts/cell and for a 12V (6 cell) battery at 25C (77F).


<center><table border="1" cellpadding="5"><tbody><tr><td>State of Charge (%)</td><td>OCV per cell</td><td>OCV per 12V battery</td></tr><tr><td>100</td><td>2.17 or greater</td><td>13.0 or greater</td></tr><tr><td>75</td><td>2.10</td><td>12.6</td></tr><tr><td>50</td><td>2.03</td><td>12.2</td></tr><tr><td>25</td><td>1.97</td><td>11.8</td></tr><tr><td>0</td><td>1.90 or less</td><td>11.4 or less</td></tr></tbody></table></center>
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Old 03-02-2012, 10:45 AM   #46
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Understanding my genset alternator

<h3>*</h3><h3>Lead-Acid State of Charge</h3><h4>Here are no-load typical voltages vs state of charge</h4>
(figured at 10.5 volts = fully discharged, and 77 degrees F). Voltages are for a 12 volt battery system. For 24 volt systems multiply by 2, for 48 volt system, multiply by 4. VPC is the volts per individual cell - if you measure more than a .2 volt difference between each cell, you need to equalize, or your batteries are going bad, or they may be sulfated. These voltages are for batteries that have been at rest for 3 hours or more. Batteries that are being charged will be higher - the voltages while under charge will not tell you anything, you have to let the battery sit for a while. For longest life, batteries should stay in the green zone. Occasional dips into the yellow are not harmful, but continual discharges to those levels will shorten battery life considerably. It is important to realize that voltage measurements are only approximate. The best determination is to measure the specific gravity, but in many batteries this is difficult or impossible. Note the large voltage drop in the last 10%.
<table style="width:400px;" border="1"><tbody><tr><th bgcolor="#ffffff" width="132">State of Charge</th><th bgcolor="#ffffff" width="132">12 Volt battery</th><th bgcolor="#ffffff" width="132">Volts per Cell</th></tr><tr><td width="132">100%</td><td width="132">12.7</td><td width="132">2.12</td></tr><tr><td width="132">90%</td><td width="132">12.5</td><td width="132">2.08</td></tr><tr><td bgcolor="#00ff00" width="132">80%</td><td bgcolor="#00ff00" width="132">12.42</td><td bgcolor="#00ff00" width="132">2.07</td></tr><tr><td bgcolor="#00ff00" width="132">70%</td><td bgcolor="#00ff00" width="132">12.32</td><td bgcolor="#00ff00" width="132">2.05</td></tr><tr><td bgcolor="#00ff00" width="132">60%</td><td bgcolor="#00ff00" width="132">12.20</td><td bgcolor="#00ff00" width="132">2.03</td></tr><tr><td bgcolor="#00ff00" width="132">50%</td><td bgcolor="#00ff00" width="132">12.06</td><td bgcolor="#00ff00" width="132">2.01</td></tr><tr><td bgcolor="#00ff00" width="132">40%</td><td bgcolor="#00ff00" width="132">11.9</td><td bgcolor="#00ff00" width="132">1.98</td></tr><tr><td bgcolor="#ffff00" width="132">30%</td><td bgcolor="#ffff00" width="132">11.75</td><td bgcolor="#ffff00" width="132">1.96</td></tr><tr><td bgcolor="#ffff00" width="132">20%</td><td bgcolor="#ffff00" width="132">11.58</td><td bgcolor="#ffff00" width="132">1.93</td></tr><tr><td bgcolor="#ff0000" width="132">10%</td><td bgcolor="#ff0000" width="132">11.31</td><td bgcolor="#ff0000" width="132">1.89</td></tr><tr><td bgcolor="#ff0000" width="132">0</td><td bgcolor="#ff0000" width="132">10.5</td><td bgcolor="#ff0000" width="132">1.75</td></tr></tbody></table>


-- Edited by FlyWright on Friday 2nd of March 2012 11:56:05 AM
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Old 03-02-2012, 10:50 AM   #47
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RE: Understanding my genset alternator

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FlyWright wrote:timjet wrote:
BD, thanks for that web site. I'll sit down tonight and read through that, good stuff.

One of my battery banks is not accepting a charge. When I arrived at the boat the other day, the batteries were fully charged reading about 13.6 volts with the charger on. I turned the charger off and after 2 hours with no DC load, the No 2 bank read 12.6 volts and the No 1 bank read 13.2 volts. I'm going to disconnect the 2 batteries on the No 2 bank and test them individually by again charging them to full capacity and then testing after 2 hours off the charger and no load. The batteries are 2 years old from West Marine and if I determine one or both are bad I'll try to get pro-rated new ones. Is my thinking correct??
You might just be looking at the surface charge on the 13.2V bank.* Like JD says, there may be a small unknown load on the 12.6 bank.* Besides, 12.6 is a full charge.* Take a look at the specific gravities of the cells to confirm a weak cell.

If you don't have a battery monitor to watch loads and charges, and the banks are identical, and if you have the time and inclination, you could swap the batteries in the 2 banks which will allow you to clean up the terminals and tighten all connections in the process.* If the low voltage stays on the same bank, you have a persistent load and your bbatteries are fine.

*All good valid*suggestions*but he*may not be able to*check the specific gravity on the AGMs.* I don't think he can check individual cell voltage either.*
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Old 03-02-2012, 10:54 AM   #48
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RE: Understanding my genset alternator

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JD wrote:FlyWright wrote:timjet wrote:
BD, thanks for that web site. I'll sit down tonight and read through that, good stuff.

One of my battery banks is not accepting a charge. When I arrived at the boat the other day, the batteries were fully charged reading about 13.6 volts with the charger on. I turned the charger off and after 2 hours with no DC load, the No 2 bank read 12.6 volts and the No 1 bank read 13.2 volts. I'm going to disconnect the 2 batteries on the No 2 bank and test them individually by again charging them to full capacity and then testing after 2 hours off the charger and no load. The batteries are 2 years old from West Marine and if I determine one or both are bad I'll try to get pro-rated new ones. Is my thinking correct??
You might just be looking at the surface charge on the 13.2V bank.* Like JD says, there may be a small unknown load on the 12.6 bank.* Besides, 12.6 is a full charge.* Take a look at the specific gravities of the cells to confirm a weak cell.

If you don't have a battery monitor to watch loads and charges, and the banks are identical, and if you have the time and inclination, you could swap the batteries in the 2 banks which will allow you to clean up the terminals and tighten all connections in the process.* If the low voltage stays on the same bank, you have a persistent load and your bbatteries are fine.

*All good valid*suggestions*but he*may not be able to*check the specific gravity on the AGMs.* I don't think he can check individual cell voltage either.*

Forgot they were AGMs.* This data is for lead acids.
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Old 03-02-2012, 10:57 AM   #49
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RE: Understanding my genset alternator

FlyWright, are those numbers for wet cells or AGM's?
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Old 03-02-2012, 10:58 AM   #50
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RE: Understanding my genset alternator

oops we crossed paths
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Old 07-05-2012, 05:17 PM   #51
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Timjet: interested to know where you got to with your original question, which was about a possible upgrade to your genset's 'start' alternator. I have been down this same path and was told that my 13.5KW genset couldn't take much more than a 20-30A alternator (as installed): the pulleys, belts and whole engineering of that end of the genset is only engineered to support a small alternator spec'd with the sole purpose of maintaining the charge on the genset start battery. I was advised not to even consider upgrading to a 'small' 60A alternator. Much better to address the real issue...inadequate House bank charging capacity....in the tried & proven ways of external smart regulation; larger proppulsion engine alts; and charge from both directed to house bank.

But where did you get to?
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Old 07-05-2012, 05:52 PM   #52
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Quote:
Originally Posted by FlyWright View Post
<h3>*</h3><h3>Lead-Acid State of Charge</h3><h4>Here are no-load typical voltages vs state of charge</h4>
(figured at 10.5 volts = fully discharged, and 77 degrees F). Voltages are for a 12 volt battery system. For 24 volt systems multiply by 2, for 48 volt system, multiply by 4. VPC is the volts per individual cell - if you measure more than a .2 volt difference between each cell, you need to equalize, or your batteries are going bad, or they may be sulfated. These voltages are for batteries that have been at rest for 3 hours or more. Batteries that are being charged will be higher - the voltages while under charge will not tell you anything, you have to let the battery sit for a while. For longest life, batteries should stay in the green zone. Occasional dips into the yellow are not harmful, but continual discharges to those levels will shorten battery life considerably. It is important to realize that voltage measurements are only approximate. The best determination is to measure the specific gravity, but in many batteries this is difficult or impossible. Note the large voltage drop in the last 10%.
<table style="width:400px;" border="1"><tbody><tr><th bgcolor="#ffffff" width="132">State of Charge</th><th bgcolor="#ffffff" width="132">12 Volt battery</th><th bgcolor="#ffffff" width="132">Volts per Cell</th></tr><tr><td width="132">100%</td><td width="132">12.7</td><td width="132">2.12</td></tr><tr><td width="132">90%</td><td width="132">12.5</td><td width="132">2.08</td></tr><tr><td bgcolor="#00ff00" width="132">80%</td><td bgcolor="#00ff00" width="132">12.42</td><td bgcolor="#00ff00" width="132">2.07</td></tr><tr><td bgcolor="#00ff00" width="132">70%</td><td bgcolor="#00ff00" width="132">12.32</td><td bgcolor="#00ff00" width="132">2.05</td></tr><tr><td bgcolor="#00ff00" width="132">60%</td><td bgcolor="#00ff00" width="132">12.20</td><td bgcolor="#00ff00" width="132">2.03</td></tr><tr><td bgcolor="#00ff00" width="132">50%</td><td bgcolor="#00ff00" width="132">12.06</td><td bgcolor="#00ff00" width="132">2.01</td></tr><tr><td bgcolor="#00ff00" width="132">40%</td><td bgcolor="#00ff00" width="132">11.9</td><td bgcolor="#00ff00" width="132">1.98</td></tr><tr><td bgcolor="#ffff00" width="132">30%</td><td bgcolor="#ffff00" width="132">11.75</td><td bgcolor="#ffff00" width="132">1.96</td></tr><tr><td bgcolor="#ffff00" width="132">20%</td><td bgcolor="#ffff00" width="132">11.58</td><td bgcolor="#ffff00" width="132">1.93</td></tr><tr><td bgcolor="#ff0000" width="132">10%</td><td bgcolor="#ff0000" width="132">11.31</td><td bgcolor="#ff0000" width="132">1.89</td></tr><tr><td bgcolor="#ff0000" width="132">0</td><td bgcolor="#ff0000" width="132">10.5</td><td bgcolor="#ff0000" width="132">1.75</td></tr></tbody></table>


-- Edited by FlyWright on Friday 2nd of March 2012 11:56:05 AM




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Old 07-06-2012, 06:28 AM   #53
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D you mention that AGM batteries of which I have 5 will accept a charge at a rate of 100% until they're full, unlike wet cells which charge at 100% until they're 80% full and then the charge rate falls off dramatically. Is this correct?

NOPE.
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