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Old 02-10-2007, 14:48   #1
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gel accumulators

Hello to all of you are at the forum.
I have a question as fllws: Presently i work on the yacht and the servicing batteries are gel type. After two times it was charged they get swollen and already ndo not have enough cappacity . If some one could tell me the reason for that . Thank you in advance
Yours Emmonev
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Old 02-10-2007, 16:49   #2
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First guess would be they are not being charged properly. Gel cells require a specific charging profile, believe they cannot tolerate higher voltage charging that flooded or AGM can handle. If they are swelling there's something seriously wrong.
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Old 02-10-2007, 17:39   #3
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Swelling and charging gel-cell or AGM batteries

It can be normal for gel-cell or AGM batteries to swell, particularly if the internal temperature varies greatly during charging from a deeply discharged state. If the swelling occurs from high internal temperatures due to excessively high charging currents over time (high charging currents may be O.K. as long as the internal temperature rate of increase and value is not too great) the swelling may be excessive and pressure release of the safety valves may release water along with the gas. This is evidenced by great bulging.

Gel-cell charging does not have to follow a protocol particular to gel-cell batteries only. Like ANY deep-discharge lead-acid battery gel-cel batteries that have been deeply discharged must have the charge voltage reach or exceed 14.4V @ 20-25 deg. C (for a 12V battery) in an acceptance mode else the capacity lost will not be recovered and subsequent charge/discharge cycles will evidence gradual loss of said capacity. Long has it been observed that some overly conservative charge instructions offered by some gel-cel and AGM battery distributors which do not allow a sufficient acceptance voltage to be reached for a sufficiently long time that the batteries suffere a premature death exhibiting an unacceptable gradual loss of capacity. To be sure, excessive gassing and temperature rise due to excessive charge currents (usually long into the charge regimen) will also result in a gradual loss of capacity.

One safe caveat when charging at or above 14.4V is to keep the charge current at or below the value of Amp-hours missing from the battery. By doing so no excessive gassing or temperature rise will occur (do not charge at or above 35 deg. C). Obviously it is handy to have a real battery monitor to be able to observe such a charging condition.
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Old 02-10-2007, 18:53   #4
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Interesting, but doesn't that just apply to the bulk stage? The Onboard Solutions manual for their charging product gives the following values:

Flooded (Lead Acid)
14.6 Absorption,
13.3 Float
AGM (Absorbed
Glass Mat)
14.4 Absorption,
13.3 Float
GEL cell
14.1 Absorption,
13.8 Float

Are these accurate? How important are the absorption and float cycles? I thought they all needed to be correct for proper charging.
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Old 02-10-2007, 19:39   #5
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Lead-acid battery charging

Hi Jdoe71,
Those numbers exemplify the misinformation which is prevalent in the users world of batteries. Let us first open our eyes in the use of various terms. "lead-acid" does not denote flooded-cell constructed batteries only. Lead-acid denotes battery chemistry of which gel-cel, AGM and flooded-cell constructed batteries form sub-groups. Regardless of the subgroup the electrochemistry is essentially the same. Differences vary little with regard to those designed to be used in deep-discharge high current applications.

The three-step charging regimen was developed and proposed as an approximation to the Amp-hour charging "law", a textbook documentation from the 1930's which was not popularized until David Smead, and Rick Proctor of Cruising Equipment Co (yes, at one time Dave Smead worked with Proctor before forming his Ample Power company) insisted on proper technical references rather than promulgating the usual "what my father did seemed to work" kinda pseudotechnology.

As a result of the misinformation which is prevalent even within the battery distributors of various manufacturers there is no uniform agreed upon set of acceptance and float voltage values across the manufacturing board.

Battery electrochemists, few as they are, are the ultimate source of "real" information which is why I, along with few others, refer only to the authoritative electrochemistry textbooks and technical publications. The fact that battery distributors must print some information which is in keeping with what available product chargers are capable of delivering helps limit their exposure to having to make "good" on battery warranty contracts.

Over several decades I, and others, have verified that indeed the gel-cel and AGM batteries still benefit from that old Amp-hour law charging which the 3-step charging regimen approximates. The two fundamental reasons for varying particular voltage limits for acceptance and float values are temperature (well defined) and specific gravity. Regardless, if the Amp-hour "law" is followed by using a battery monitor that is capable of measuring accurately Amp-hours in and out the deviation of acceptance voltage is allowed without penalty.

In conjunction with having utilized a sufficiently high acceptance voltage the charge acceptance of a fully charge battery will be very low and it has been observed that the slight variation of float voltage will therefore, result in little current change and certainly not so as to gas the battery as long as radical temperature changes (greater than 10 deg F, for example) are noticed in order to adjust the float voltage.
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Old 03-10-2007, 06:37   #6
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Rick, thanks for taking the time to provide such a detailed explanation. I want to be sure I understand this, I knew that these are all lead-acid batteries and understand the construction methods of them and I think I have a grasp on where each excels or is deficient compared to the other types. But I always believed there were differences in charging profiles required because the battery makers say so.

So the profiles don't matter a lot regardless of battery type as long as the voltage is high enough (14.4 at least), the amps removed are returned and the temperature is kept low enough to not cause excessive gassing and internal damage. Is that a correct summary?

Thanks again for the education, much appreciated.
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Old 03-10-2007, 10:59   #7
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Emmonev-
If you mean that your batteries have already lost some of their original capacity, that could be a sign of overcharging which has begun to "cook" them and boil out electrolyte (in the form of gas). If the batteries do vent gas during charging--they are being overcharged and damaged.

Rick, a gentlemen who asked that I not mention his name or employer (they make a large number of batteries under multiple brands) told me recently that the maximum charging voltage and amperage must both be considered. If the voltage is kept low enough, the amperage can be real high. But as the voltage approaches limits for that battery chemistry--what "had been" safe amperage can become unsafe. That being part of the reason they use volt and amp ratings for the 3-stage modelling, which he outright said is obsolete but still useful if you aren't a computer.[g]

Everything I've seen about gel batteries says they MUST run at slightly lower voltage than other lead acid cells, or they will be harmed. I would guess that means "harmed if you use amperage at that excess voltage", i.e. if E's charging system is pumping many amps, and the voltage has not been reduced for gels, he could be cooking them off.

Of course without knowing the battery type/specs, and the system voltage, that's still an assumption.
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Old 03-10-2007, 14:01   #8
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gel accumulators

Many thanks to all of you get involved in my case. Unfortunatly as it seems the accumulators has boiled because as it has explained in your comments they need special charging pannel . In my case we have the yacht that has builded 1981 year and the charging device has 3 voltage stages that could not to be tunned.

Thank you one more time because you save my ........


Best Regards,

Emmonev
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Old 03-10-2007, 14:53   #9
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Rick, I have followed your advise, on setting up the battery charging system on my boat which is due to go in the water in a week.
I have four 200amp AGM battery set up as one bank. I have a xantrex regulator.
I also have a 13 hp Honda driving a 200 amp alternator for charging the batteries.
I get about 170-190 amps out of the honda running at 1/2 throttle.

The other day i left all the lights on overnight by accident and flattened the battery bank.
The next morning I had only 8 volts reading on the xantrex battery gauge.
I statred the Honda (by hand) but the alternator would not charge. I assume this was because the voltage was too low.
As it was, because I am still connected to mains power, I put a small battery charger on the batteries until the voltage reached 9.5 volts at which time I started tthe Honda again and the alternator did in fact cut in at 170 amps.

The question is (other than don't flatten the batteries again) how can i excite the alternator to charge if I am at a seculed mooring if the same situation happens again.
I do have two Honda outboards but they only put out 15 amp each.
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Old 03-10-2007, 17:55   #10
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Beau, it sounds like you need an older dumber alternator/regulator. The modern trend seems to be that they are set so they will WORK with a low battery--but they are programmed to not do so. Any battery voltage below ~10VDC and some of the newer equipment will simply refuse to engage, in the belief that 10V is "wrong" and they don't want anything to start up without professional intervention.

Sounds like the kind of engineering that comes out of Bavaria, not Detroit, (sigh)

I think you'd have to recable at least one battery to make 2x8=16V and convince the alternator to start up charging that--then shut down once it got some juice, and set them back to normal.

AFAIK this is programmed in the internal regulators and can't bypassed without giving their sense lead a "normal" voltage.

Unless you patched the output from one of the Honda outboards in...or used them as the primary charger until you got up past 10V?
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Old 03-10-2007, 21:43   #11
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Beau - Just my humble opinion but I wouldn't go long range cruising - read self sufficient - without 2 banks.

Also - flattening 800ah overnight seems sporty. What is your "normal" load out?

Are you considering an alternate charge source - i.e. solar?
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Old 04-10-2007, 00:41   #12
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Beau
If you are on the hook and desperate to fool the reg then you could just find 12V elsewhere, maybe some AA cells. It is only a sense input that would draw almost no current.
I am assuming the Xanrex has a remote sense lead

Mike
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Old 04-10-2007, 01:54   #13
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The alternator is off a mercedes truck.

we are located in a shed and with the tinted windows fitted it was a bit dark so we have been running lights/testing anchor winch etc plus generally checking that everything works.
Plus the Xantrex battery gauge was not set up right.
In future I will watch the voltage drop more carefully. Which seems to be the best test, and not let the voltage drop below 11.2.
Also the Chonda motor and alternator has not been properly installed yet (exhaust pipe need replacing etc.)
It is a bit nosier than expected so I am proceeding with a sound reducing enclosure with metal mesh and foam and cooling air is supplied with a car type 12volt radiator fan through a series of baffles.

Power use seems reasonble with fridge and freezer drawing 40 amps at start up and then dropping to 14 amps when compressor is running.
The 9,000 btu air conditioner which will only be used at night in a small cabin uses 50 amps to start and run (inverter type air con) but the amp draw drops down as the temperature drops.

I will carry a spare battery to excite the alternator if it happens again, plus as I said I can hand start the 30 hp Hondas.

Mast goes on next week and in the water hopefully next friday.
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