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Old 08-06-2009, 08:59   #1
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Charging Problem?

Since I launched this year (about a month ago) I have noticed that it takes longer than last year to charge my batteries via the alternator. While the boat was on the hard, I charged the batteries via shore power monthly, and it never took more than 10 minutes to top up my 2 4D cells. I would assume that this means that the batteries are still holding a good charge.

I am assuming that either my consumption has gone up, or there is a problem with my charging system. The charging is done by the alternator on my Yanmar 3YM30 and a Xantrax charger. With the charger (and motor) on and the batteries topped up, i see a voltage of 13.5 volts.

My first thought was that the alternator belt might not be tight enough as I loosen it for the winter, but the tension on the belt seems ok. I then thought that maybe i have a leak that is causing the bilge pump to run more frequently and draining my batteries, but i see no evidence of this.

Any ideas of what I can do to get a better understanding of what is happening here?

Thanks,
Pete
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Old 08-06-2009, 09:36   #2
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With the 3ym30 engine, there is one location for both charging current output and starter power input. This as you are probably aware is a terminal on the starter. I experienced a reduction in output once because the nut holding the wires to the starter had come loose. I'd check that to be sure everything is secure as an initial step.

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Old 08-06-2009, 09:42   #3
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A significant problem for car charging is always the earth lead. It is always the first thing I check. Long time since I played with an inboard engine, but they must have an equivalence.
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Old 09-06-2009, 09:57   #4
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Thanks for the input. These are good thoughts. I will check this weekend and see if I spot anything suspicious.

Pete
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Old 09-06-2009, 10:18   #5
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I think you are getting false readings of surface charge that are masking the underlying battery condition. You CANNOT make ANY judgement about battery state of charge by voltage readings if the batteries have been charged (even for a little while) within the last 24 hours.

Assuming they are wet cells...some suggestions:

1. Get a REAL battery monitor that measures amps in and out. Like this:
Victron BMV 600 Battery Monitor

2. Discharge your batteries at least 30% then leave them on your charger overnight. THEN apply an EQ charge of 15.5V for 8 hours while monitoring temperature to keep under 120degrees. Hopefully you Xantrex has an EQ cycle. Otherwise they'll need to be removed.

If you don't want to spend the $$ on a battery monitoring system...get an accurate hydrometer...fully charge the battery overnight...wait 24 hours with NO charging and NO load and test:
State of Charge/Specific Gravity Chart:
12V6V
100%1.265
75%1.225
50%1.190
25%1.155
Discharged1.120

If you show less than 1.235...do an EQ cycle and see if things improve. If the readings are below 1.225 you can also try an EQ...but chances are the batteries have been degraded.
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Old 09-06-2009, 10:31   #6
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Thanks for the info. I can't leave it on a charger overnight as I am on a mooring. I equalize the batteries each fall when I pull the boat out. At that time the hydrometer reading was very good.

I have considered getting a real battery monitor. For now I am using the Xantrax Freedom charger/inverter control panel. It shows 3 states for the battery that correspond to the three charging modes. When the charger goes into the 'float' mode, I consider the batteries fully charged. The time that it takes to get to this state is significantly longer than in years past. It could be the age of the batteries (about 4 years old) but before i get new batteries, i want to make sure that it is not something simpler.
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Old 10-06-2009, 16:48   #7
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Find a marine electrician with a battery conductance tester and have him test your batteries. These testers are manufactured by Midtronics and use a high frequency pulse to test the internal resistance of the batteries and correlates this with actual CCA of the battery. It is recommended that you replace the batteries when the actual CCA is < 80% of the CCA stated for the battery.
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Old 10-06-2009, 17:11   #8
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I like find a marine electrician and have him fix it better!

Okay, I'll keep my fingers to myself now!
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Old 10-06-2009, 19:58   #9
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Originally Posted by cruiser_pete View Post
I equalize the batteries each fall when I pull the boat out. At that time the hydrometer reading was very good.
A couple of more thoughts:
1. If you tested in the fall after charging fully or EQ'ing and did NOT wait 24 hours...you had a false test. Also...hope your hygrometer gives real readings...not just good/caution/bad auto type.
2. If the batteries were left to self discharge over the winter before recharging, they could have lost considerable capacity and sulfated.
3. Your comment about never taking more than 10 minutes to fully charge a 4D pair and using only the Xantrex leds to tell you state of charge says to me that you have been gradually murdering your batteries by not taking the literally hours it takes to get a 100% charge on your batteries since the Xantrex lights up well before full charge is achieved and it takes several hours to get the last 10% of charge in.

I suspect that your batteries are no longer capable of performing close to their rated amphours. Your only hope of saving them will be to remove them and fully charge them ashore...then put an EQ charge on them to see if you can bring them back to near full power. Wait 24 hours and check specific gravity.

Alternatively, you can take 'em to a battery shop and have them load tested after charging. Good luck!
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Old 10-06-2009, 20:04   #10
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Quote:
Originally Posted by Strygaldwir View Post
With the 3ym30 engine, there is one location for both charging current output and starter power input. This as you are probably aware is a terminal on the starter.
Keith
Is this the case with other marine engines? My boatyard is finishing the install of my Nanni and there is only one wire from the starter area to the battery switch. There seems to be no connection from the alternator itself other than the external regulator. I have separate house and starting circuits and had planned for the starting battery to feed the starter and the alternator to feed the house with an echoe charge to the start battery.

In the above case, how do you start with one bank and charge the other?
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Old 10-06-2009, 21:47   #11
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Well, therein lies a problem! It was certainly a surprise when I was installing the 3ym's especially given that the 3gm30's have seperate circuits. I ended up just putting a battery switch in the circuit. I use this to manually shift battery banks. This has an advantage in that I can readily start my engines from the starting bank or the house bank. Perversly enough, it also lets me use my starting battery as a house bank.

You can use a battery combiner to tie the two banks together for charging.

I don't know about other engines, I expect not though. As I said, it doesn't even exist for the 3gm series.
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Old 11-06-2009, 09:29   #12
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A couple of more thoughts:

2. If the batteries were left to self discharge over the winter before recharging, they could have lost considerable capacity and sulfated.
3. Your comment about never taking more than 10 minutes to fully charge a 4D pair and using only the Xantrex leds to tell you state of charge says to me that you have been gradually murdering your batteries by not taking the literally hours it takes to get a 100% charge on your batteries since the Xantrex lights up well before full charge is achieved and it takes several hours to get the last 10% of charge in.
Regarding the winter, they were charged every 3 weeks. While the Xantrax did indeed light up after 10 minutes, i left it plugged in for hours after that.
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Old 11-06-2009, 09:32   #13
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Originally Posted by Strygaldwir View Post
I like find a marine electrician and have him fix it better!
Can you interpret please?
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Old 11-06-2009, 12:03   #14
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Pete...OK...should not have any worries then!!
I'd just try to EQ them to bring some extra life back into them before giving up on them.
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Old 11-06-2009, 12:06   #15
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Check, your cable attachments everywhere, but check the batt terminals for "wet" corrosion. It may not be visible like the white corrosion.
Charge your batteries, disconnect one of the leads to each battery, measure your voltage the next day. If the battery charge stays up 12.5 volts or so. the batts are good.
10 minutes charging might be reasonable if you aren't really drawing anything out...
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