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Go Back   SailNet Community > On Board > Gear & Maintenance > Battery Equalization Amperage
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Thread: Battery Equalization Amperage Reply to Thread
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Topic Review (Newest First)
02-02-2012 10:36 AM
obelisk
Merry Christmas, Charlie Brown

I was unable to equalize the battery bank I was having trouble with so I contacted the battery shop here in Puerto Montt and they came to check them. after hooking up their machine, to each battery we found that the BEST of the 3 12V Rolls 113t batteries only had 32% of its life remaining. it was a sad site sitting in the battery box all alone. one crew member equated it to the Charlie Brown christmas tree:



I decided on a new 450AH bank with 4 6V Trojan batteries. 2 banks of two batteries hooked in series. after cuttien the battery box in half and re glassing (with some west system and an old cotton T-shirt!) it to acommodate the extra 1/2" needed, here is the setup:
01-08-2012 08:32 AM
obelisk i know that 14.8 is not ideal but i had read that, given a longer period, it would accomplish the same thing. i guess i'll look into borrowing/renting a portable charger somewhere in Pto. Montt.

a note about battery monitor calibration: I have found in teh past that it does not read completely accurately until after a deep discharge/full recharge cycle once it has been unhooked. maybe the lack of equalization and resulting sulfation has got ti all mixed up. i'll let my batteries do the thinking for the time being and worry about the monitor later--it is reading accurate amps and volts, which is enough.
01-08-2012 12:25 AM
btrayfors
Quote:
Originally Posted by obelisk View Post
hmm, am i being fooled by my battery monitor? it reads 100% and has since beginning equalization and the charger is still putting in almost 10A.

Yes. It's not accurate, and needs re-calibration.

BTW, 14.8VDC is not enough to do a real equalization. You need at least 15.5VDC, increasing to about 16.5VDC.

Bill
01-07-2012 11:59 PM
obelisk hmm, am i being fooled by my battery monitor? it reads 100% and has since beginning equalization and the charger is still putting in almost 10A.
01-07-2012 11:19 PM
Maine Sail
Quote:
Originally Posted by obelisk View Post
so, the batteries themselves will dictate how many amps they receive during equalization?

I have separated my three batteries and am equalizing them separately so that I can retain use of the boat's electrical system in the meantime. my battery charger is currently (no pun intended) putting in 10A at 14.3V into my 136AH flooded deep cycle battery. I have set the voltage to 14.8, the max setting. It is not the desired 15.5, so I will just have to continue the process longer. Will the amps continue to drop as the voltage comes up to the target and the SG rises?
Yes the current will drop. You should see under 2% of capacity acceptance when the batteries are mostly full. The last bit takes a long while and with healthy batteries you can get them to under 1% acceptance at around 14.4V so slightly higher at 14.8V..
01-07-2012 11:00 PM
obelisk so, the batteries themselves will dictate how many amps they receive during equalization?

I have separated my three batteries and am equalizing them separately so that I can retain use of the boat's electrical system in the meantime. my battery charger is currently (no pun intended) putting in 10A at 14.3V into my 136AH flooded deep cycle battery. I have set the voltage to 14.8, the max setting. It is not the desired 15.5, so I will just have to continue the process longer. Will the amps continue to drop as the voltage comes up to the target and the SG rises?
01-07-2012 03:56 PM
btrayfors A battery has a certain (and variable) internal resistance. The value of this resistance depends on several things, most notably:

1. the type and chemical composition of the battery (flooded, AGM, gelled lead-acid);

2. the state-of-charge (SOC) of that battery -- the lower the SOC the less internal resistance the battery;

3. the ambient temperature and internal temperature of the battery; and

4. the condition of the battery -- as batteries age and deteriorate, their internal resistance changes.

Now, think about Ohms Law. In any active electrical circuit, amperage = voltage divided by resistance (I = E/R). As resistance increases such as when a battery moves toward a higher SOC, then current (amperage) decreases accordingly.

It's the battery, not the charging source, which determines how much amperage will flow, assuming the same voltage being provided.

If, for example, a battery is accepting 25 amps @ 14.2 volts from a 50-amp charger, it would accept exactly the same amperage from any charging source -- battery charger, wind generator, solar panels, etc. if they were to be controlled at 14.2 volts.

The only way to "push" more amps into the battery would be to increase the voltage.

Wind generators have "dump" resistors because they need to be kept under load, even when no further charging is required. You can't just break the circuit, because you'll blow them out. Therefore, you have either to physically stop their rotation or divert their output, e.g., to "dump resistors" (preferably to a useful one like a 12VDC heating coil in the hot water heater).

Solar panels are different: their circuits can be interrupted without damage by a simple switch.

However, both wind generators and solar panels -- as well as all other charging sources of any decent capacity -- require a good regulator to control their voltage levels. Why? Ohms Law, as explained above.

Hope this helps a bit.

Bill
01-07-2012 02:10 PM
notawriter Maybe Iíve got the science wrong, but Iím confused by the answers to the original posterís question. My understanding is that a battery in need of recharging is not a traditional load which will simply draw the amps it requires. I also think that charge generators (for example wind and engine alternators) actually push electrons down the wire and thus "dump" resistors are often part of the system. Do battery chargers have electronics which accomplish this and prevent the battery from ďacceptingĒ too much charge too fast?
01-05-2012 06:12 PM
obelisk unfortunately, i have been in the US and away from Chile for some time, working, and unable to properly tend to the batteries. I have a Balmar ARS-5 charger that does not have an equalization setting but I do have an equalization setting on my SolarBoost 2000e solar charge controller or access to an independent mobile adjustable charger.

If i may get straight to the point: I can adjust the voltage, but is 12-20 amps too much to be putting into a a 408ah battery bank during equalization as long as I monitor the temp and stop charging and cool down when the electrolyte nears 118deg F?
01-05-2012 04:36 PM
btrayfors Yes, I agree with Maine 100% on this.

And, the batteries I was trying to revive experimentally are a perfect example of what he said. They lived their 8 years as a power source for my radios in my home. They were on an Iota DLS-45/IQ4 smart charger with a float voltage of 13.6VDC 24/7. They obviously didn't move around much, but were stationary at my radio shack location.

Occasionally, they'd get a healthy draw of 90A with my 12V 500 watt HF amplifier on, but the charger was on at the same time so they really didn't get much of a workout unless we lost power....a relatively rare occurrence.

Sometimes, not often, I'd "exercise" them by pulling the plug on the battery charger for a day or two, and using the radios entirely from the batteries.

During equalization, the batteries bubbled vigorously and got warm, but not hot. You could feel the warmth on their sides, but not really at their terminals. There was no noticeable loss of electrolyte. These batteries, like all of my T-105s, have WaterMiser caps.

Conclusion: Despite being on a 13.6VDC float charge 95% of the time, they nevertheless aged and lost capacity (most likely through stratification and sulfation) over those years. I removed them from service about six months ago when they were down to about 45% capacity (as measured by a Midtronics tester) and were losing it fast.

A couple of weeks ago when I tried to revive them, they were at about 30-35% of original capacity. After several days of jolting them pretty good with a healthy equalization charge of 16.5VDC @ about 20 amps, they still tested about 35% capacity, so no improvement there.

There was a sort of "improvement" though: the cell bubbling was more uniform (one cell barely bubbled at all when I began the treatment) and the pair now holds a charge much better than before, i.e., the self-discharge rate is much less. However, their capacity didn't really improve.

I did do a real (direct) capacity test with them, however, putting a 12 amp load on them. They delivered just over 70AH in a 6-hour period before falling to 10.0VDC under load, which is consistent with my earlier estimate of 30-35% capacity. A new T-105 pair, broken in, would have gone almost 20 hours before dropping that low.

FWIW,

Bill
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