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Old 09-06-2018, 09:37   #46
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Re: Is There a Point to Float with LA/Liveaboard/Solar

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Am I right to be concerned about Hydrogen and Oxygen generation during "topping off" charging? Seems like you would never want FLA batteries to start gassing unless very well ventilated. I have personally witnessed a small building explode due to this ...
Literally thousands of boats have used fla batteries cruising for years, I would say very close to all are housed inside.
The gas is explosive but if using proper charging regimes it should never be an issue. When equalising I run the bilge blower just to err on the side of caution as the batteries are gassing more than normal.
I've never had a problem.
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Old 09-06-2018, 09:50   #47
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Is There a Point to Float with LA/Liveaboard/Solar

I don’t understand cooking a battery at absorption voltage.
Maybe it’s because my absorption voltage is 14.3?
Millions of automobiles run around with constant voltage of 13.8 to 14.2 V.
Most all boats do the same as only us battery nerds run external regulators like the Balmar 614.
Finally, just for grins I turned off my Sterling Pro charge Ultra and turned it back on, this puts it in absorption.
Now my bank is well and fully 100% charged, but the total amount of current going into my 660 AH bank is .2 amps, I’m cooking a 660 AH bank with .2 amps?
I’m not abdicating leave one in absorption forever, but assuming nothing is wrong with your bank internal short etc, as it approaches well and truly 100% charged, the amps will continue to drop, to almost nothing. I consider .2 amps almost nothing. An hour or two at levels like that ought to hurt nothing.
I think what really kills banks is voltages higher than absorption, or how do automobile 12 V batteries last so long?Click image for larger version

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Old 09-06-2018, 09:50   #48
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Re: Is There a Point to Float with LA/Liveaboard/Solar

I suspected that most solar charging on boats lacks the power to gas the batteries much, but good to know practical experience proves it safe.

I just hope that the explosions blamed on propane were not really battery gasses...
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Old 09-06-2018, 09:56   #49
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Is There a Point to Float with LA/Liveaboard/Solar

Hydrogen is so light a gas, it’s very improbable that you could get an explosive concentration.
Only reason Propane is so bad is it’s heavier and therefore will sit down low and accumulate, hydrogen and CNG will dissipate through the hatch boards etc.
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Old 09-06-2018, 10:06   #50
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Re: Is There a Point to Float with LA/Liveaboard/Solar

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how do automobile 12 V batteries last so long?
I am not sure they do.

Automotive batteries are usually kept close to 100% SOC, which lead acid batteries love, so they should last a long time, but personally I have experienced a longer life from batteries in my boat house bank than the batteries in my car.

Automotive batteries are not often regulated with a multi step algorithm, as are the batteries in our house bank, but the voltage (if measured at the battery) is typically closer to our float voltage than an absorption voltage.
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Old 09-06-2018, 10:48   #51
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Is There a Point to Float with LA/Liveaboard/Solar

Automotive alternators should output 14V plus or minus .2V.
Unless standards have changed.
Lifelines absorption voltage is 14.3, only .3 V higher than a non regulated alternator will supply all of the time.
The fact that automotive batteries stay at 100% SOC further brings the question that absorption voltages aren’t killers, cause the live right at absorption levels, the whole time the car is running,
However this is all sort of mute, at absorption voltage, amps accepted will continue to drop to almost nothing over time.
How is this damaging a battery and it’s done for only an hour or two, at the most? That was the question that started the thread.
I don’t believe it’s damaging.
I guess I won’t change your mind anymore than you will change mine.
Now if my Solar controller could be programmed so that I could set an actual acceptance rate of charge to end Acceptance and drop to float, the yes, of course that would be best, but going by a timer just doesn’t work in my opinion, cause every day is not the same Solar wise, some days you get great output, some days not so much.
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Old 09-06-2018, 11:46   #52
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Re: Is There a Point to Float with LA/Liveaboard/Solar

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Automotive alternators should output 14V
14v is closer to a typical yacht float voltage than an absorption voltage, especially as car electrics usually have more voltage drop than boats so the actual battery voltage is likely to be close to 13.8v, which would be a typical house bank float voltage.

An absorption time of one to two hours is fine, but one or two hours after the end amps are reached is not ideal.

I agree solar days do have considerable variation, but if the solar output is low, the controller will spend much longer in bulk. The controller will never reach float, or even absorption, which is how it should be.

An absorption timer is not the perfect way to determine when to drop down to float, but if the battery has been kept at, for example, 14.6v (as a typical absorption voltage) for say the 2 hours, then the battery return amps are likely to be at a level where a drop down to a float voltage is appropriate.

If not, the absorption time needs to be increased.
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Old 09-06-2018, 12:06   #53
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Re: Is There a Point to Float with LA/Liveaboard/Solar

Starter batts are not cycled, normal cranking does not come close to DoD of 1%

And I know for myself, 5 years is considered a long lifespan, while I'm shooting for much more than that from my expensive deep-cycling banks.

Depending on location, alts in many modern very efficient vehicles are rarely putting out high voltages.
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Old 09-06-2018, 12:11   #54
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Re: Is There a Point to Float with LA/Liveaboard/Solar

I agree that the often-recommended .005C transition setpoint is often pushing too hard for sealed chemistries, best to follow mfg specs.

I believe Firefly's is .02C and ideal is "just stop" as with LFP, rather than Floating.

So while this is a very rare problem - holding Absorb V too long - in most cruising setups, it is worth being aware that "too much of a good thing" can reduce longevity.
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Old 09-06-2018, 12:11   #55
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Re: Is There a Point to Float with LA/Liveaboard/Solar

Car batteries are a completly different thing. They are made only to efficiently start the engine.
thin plates like a net to increase the surface and get as much current as possible from a small battery fore 15 to 30 seconds, then recharge. They will die when deep discharged or used as house battery, they simply will dissolve. All the time tney usually float, they are well oversized to ensure starting in cold conditions. It is not about capacity, but about current.

House batteries are completely different, thick lead plates, not so high current but a lot of capacity, they weight 20-50% more per Ah than a start battery. They have a deeper sink for the acid, so if small parts of a plate dissolves, falls down it does not short the cell. They are made to cycle.
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Old 09-06-2018, 12:13   #56
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Re: Is There a Point to Float with LA/Liveaboard/Solar

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How is this damaging a battery and it’s done for only an hour or two, at the most? That was the question that started the thread.
I don’t believe it’s damaging
I agree, for only a few hours, and only some cycles, much better than not getting to Full often enough.
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Old 09-06-2018, 12:14   #57
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Re: Is There a Point to Float with LA/Liveaboard/Solar

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An absorption time of one to two hours is fine, but one or two hours after the end amps are reached is not ideal.

Really, you charge your bank in only an hour or two at absorption voltage? Most take a lot longer, maybe your in bulk for four or five hours? Cause it takes five or six hours to charge my bank, as it does most I think,
Typical Solar day is what 6 hours or so? Remember most of us are panels are mounted flat, that takes an hour or two off of the insolation charts.
That is right at about the time it takes to charge a bank, except the fact that Solar starts and ends trickle charging, unlike charging off of a generator or alternator, Solar doesn’t give high amps when high amps can be accepted.
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Old 09-06-2018, 12:17   #58
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Re: Is There a Point to Float with LA/Liveaboard/Solar

Hydrogen release is a normal thing with FLA.

Only harmful if allowed to build up in an unvented space.

Which if that's true for your whole living space, would in itself be unhealthy, humidity alone causes problems.

Even sealed batts offgas, but normally not much.

And yes it rises, so easy to vent for those who are sensitive.

IMO not a reason to avoid FLA.
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Old 09-06-2018, 12:18   #59
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Re: Is There a Point to Float with LA/Liveaboard/Solar

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Really, you charge your bank in only an hour or two at absorption voltage? Most take a lot longer, maybe your in bulk for four or five hours? Cause it takes five or six hours to charge my bank, as it does most I think,
Typical Solar day is what 6 hours or so? Remember most of us are panels are mounted flat, that takes an hour or two off of the insolation charts.
That is right at about the time it takes to charge a bank, except the fact that Solar starts and ends trickle charging, unlike charging off of a generator or alternator, Solar doesn’t give high amps when high amps can be accepted.
This is a GEL issue, not so much with AGM, they need shorter absorption, or FLA, and definitely not with LFP. It is also a question of Solar capacity and other charging sources like wind /hydrogenerator, alternator etc.
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Old 09-06-2018, 12:21   #60
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Re: Is There a Point to Float with LA/Liveaboard/Solar

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Automotive alternators should output 14V plus or minus .2V.
I thought they were higher these days?
The Iskra AAK on my newish Beta is set to 14.6v, quick google shows it seems a popular choice for cars as well. Data sheet says nominal 14v.
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