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Go Back   SailNet Community > On Board > Gear & Maintenance > Electrical Systems > System voltage
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Thread: System voltage Reply to Thread
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Topic Review (Newest First)
08-03-2009 05:00 PM
SteveInMD Based on the numbers you provided, I think your batteries are doing alright. Pulling them down a bit further and then waiting longer to look at the resting voltage would have been a more rigorous test. I'd just keep an eye on them at this point.
08-03-2009 09:13 AM
bhcva Steve....
After a long weekend on the boat and re-reading the Heart 10 manual, the float (and accept) voltage is a function of temperature and what I was seeing was pretty much spot on according to their chart.

I did get to run a short load test....drawing 30% out of the batteries with a 5% load (440ah T-105s) stopping for short rest at 3 points. The voltage readings at those points were about 22 ah (5%) low. I had thought the batteries were in worse shape. Perhaps if I had had the time to go down to 60% I would have seen much worse performance?

Thanks, Bruce
07-29-2009 01:25 PM
SteveInMD Does the charger have a temperature probe connected to the batteries?

If I lived hours from the boat I would have a mechanic stop by and do a load test. He will be able to see of the batteries behave normally under a load.

I'd say the float voltage has more to do with your charger than your batteries, unless they are really really bad.

Since you have a battery monitor you should be able to run the batteries down to 60% or so and then look at the voltage (after resting for a while). If the voltage is below what the tables say then your batteries are on their way out.
07-29-2009 09:56 AM
bhcva I asked because I know that my batteries are not up to snuff, but I don't know just how bad they are. We are hours away from the boat, so it's difficult to find the time to let the batteries come up to full charge then rest for 12/24 hours then let them drain at the recommended rate, etc. As I read the original statement as to float normally being at 13.6 I looked up and saw 13.3 on my link 2000R and wondered what sort of measure that might provide. I did notice a few days later after a sail and being plugged into the dock again, that the float again settled at 13.3.

The batteries are t-105s...four of them about five years old.

Thanks for the replies.

Bruce
07-27-2009 07:43 PM
SteveInMD I'd just stick with the plain old nothing. Without knowing if the batteries are wet, AGM, or gel and if the charger has a temp. sensor the 13.3 vs 13.6 means nothing at all.
07-27-2009 06:55 PM
hellosailor
Quote:
Originally Posted by bhcva View Post
Hello: How much can one read into a float charge of 13.3 vice 13.6?
Well, I almost agree with BT, I'd say "nothing significant" rather than just nothing. In general, a lower float charge would indicate that your battery is weaker to begin with, or there are wiring losses higher than there should be, or the charging system isn't putting out as high a charge as it might/should be.

If the battery is load tested (or at least, tested with the float burned off and after allowing 24 hours for the chemistry to equalize internally) and the charging system is tested in operation, and both test out OK, then whatever the float charge measures, is normal for your setup.

13.3 versus 13.6 could just reflect the different between two meters. Rule of thumb, unless you have a recently calibrated high quality meter, is that the rightmost digit may be off by 2-3 numbers from meter to meter, and that's just because cheap meters aren't intended for high precision.
07-27-2009 04:53 PM
btrayfors Nothing. without further information. Both are appropriate, depending on the situation. What's your question? What are the details of your setup? Why are you concerned?

Bill
07-27-2009 04:27 PM
bhcva Hello: How much can one read into a float charge of 13.3 vice 13.6?
07-24-2009 02:25 PM
SteveInMD Pior - system voltage (as this thread is called) is of fairly limited usefulness in determining the health and charge state of a battery bank. It's better than nothing, but a battery monitor will give you much better information.
07-24-2009 01:02 PM
btrayfors 7 amps is a small load for a T-105 bank of two 6V golf carts in series.

When the batteries are really "fully charged", you will see a float voltage for a short time...above 12.7VDC.

Thereafter, for quite a while, you should be seeing 12.6VDC. How long? Depends on several factors, some cited above.

If the batteries are in very good condition, have recently been exercised a few times, and have been fully charged at 14.4VDC, you'll see 12.6VDC for awhile. You may see 12.5VDC sooner than you'd think, but it will hang in there for a long time if only 7 amps is applied as a load.

There's no way to know the true capacity of your battery bank unless you do a constant load test, in this case applying about an 11 amp load for 20 hours, or until the bank reaches 10.5VDC.

By the way, voltages should be measured at the battery terminals with a calibrated digital voltmeter. You can't rely on other readouts, unless they are known to be accurate.

Bill
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