I have a 115AH deep-cycle battery that I bought as a stand-by battery for my amateur radio station. It has been in a "battery box" on trickle-charge (using a charger with a "deep-cycle" setting) for most of the time since I bought it over a year ago, and it has been called on to supply power only a few times.
Recently I noticed that the "fully charged" LED on the charger was not on and started investigating further.
Having not encountered any batteries in the last few decades that have not been sealed and "maintenance free," I was surprised to find tiny print about checking the electrolyte level every 30 days -- but even then it took me a few minutes to figure out how to get access to the cells to check this.
Anyway, when I removed the cunningly disguised covers, I found that the cells looked totally dry, and each took close to a pint of distilled water to bring the electrolyte level above the plates.
The battery has now been on charge for about 20 hours at the charger's
12A setting, but most of the time the ammeter on the charger has shown only about 5A. The cells are all still gassing.
Is this battery likely to come back to life again, or is it toast? Any remedial actions to take?
Perce (This is my usenet alias. I *am* an FCC-licensed "ham," but my real name and callsign have no relevance to this question.)
My sense is that the battery's capacity will be severely impaired. You may have the voltage, but the ampere hours won't be the same. A pint per cell ... the poor thing was dry!
Trickle Chargers do just that ... constant low rate. But doing that to a fully charged battery warms the cells and evaporates electrolyte. Monthly service is probably about right.
A better solution is a battery 'tender' or 'maintainer' that totally cuts off the charge current based on battery voltage. Kits for these are advertised in QST.
It sounds to me that it is likely to survive, but I hope you are not over charging?! I assume you are also monitoring the voltage? To be sure how it turns out, you really ought to get a guage to measure the specific gravity of the electrolyte in each cell and check. Should be available cheap at auto supply stores.
The battery may be recoverable, but I suspect it's going to take some effort, and it may well have passed the point of no return.
The fact that the cells are drawing low current, but are electrolyzing, suggests to me that you've got a combination of a high charge voltage (above 14.4) and some pretty badly sulphated plates. The bottom parts of the plates (where there was still some electrolyte) may be OK, while the upper portions may be sulphated and/or the separators may be clogged with solids.
First thing I'd do, is just give it some time on the current setting, checking the electrolyte level periodically and refilling as necessary. Given some time, the relatively high voltage may clear out some of the sulphation and residue.
If not, then it might be worth trying to recondition the battery. There are electrical desulphators available, which hit the battery with a high-voltage high-frequency pulse in order to break up and redissolve the sulphate crystals - some people say these work very well, others are less impressed. I've also seen chemical desulphation suggested, via the addition of some sort of chelation chemical (I
*think* EDTA is used but don't trust that possibility without confirming it!).
If some of the plate material has disintegrated and fallen to the bottom of the cell, then the battery is probably a goner. The residue can end up shorting the cell.
On 08/16/05 01:14 pm Ed tossed the following ingredients into the ever-growing pot of cybersoup:
You are probably correct in suggesting a hydrometer. But I should have mentioned that the "fully charged" LED has not yet illuminated again; I'm assuming that that is supposed to indicate that the appropriate voltage has been reached. With the charger disconnected, I read 13.4V -- still a little low, I think.
Also, although I mentioned that the battery had been on "trickle charge" for all that time, I was in fact using the specific "Automatic -- Deep Cycle" setting of the charger, which I "assumed" (there's that word again) was "supposed to" (and that phrase again) prevent overcharging.
Living on a boat, I deal with deep cycle batteries continually.
EVERYTHING ABOARD runs off of my batteries and I take good care of them since I hate cold beer. (yes 12vdc refrigeration)
The uncovered plates will have begun to oxidize as soon as exposed to air. The liklihood of being able to recover from that depends on how long they were uncovered. By the way, a "fully charged" 12vdc battery, when not connected to any load at all, and not charging, will read 12.6 volts. So reading higher as you stated is a positive indicator.
When batteries are charged they are (or should be) put through three stages of charge:
Bulk charge - where the battery accepts about 80~90% of it's capacity to charge. A lot of current can be put into the batteries through this charge. When bulk charging I see 50 amps or more.
Absorbtion charge - topping up the battery until the voltage reaches around 14.1 volts. The amount of current put into the batteries tapers off during this charge as the voltage increases.
Float charge - once FULL absorbtion voltage (14.1) is reached, the charger should drop the voltage back to around 13.25 or there abouts, and current is minimal (a couple of amps tops). That's the charge the keeps the battery topped up.
The LED on the charger may be nothing more than a volt meter reading. There is no way to know what your charger is doing without the specs. Most lower cost chargers don't really do much but shut off at a pre-set voltage. Perhaps the LED indicates that the charger is off, and you can measure with a volt meter to see what point the charger shuts off and deteremine how it handles charging. Refer to the voltages above to see when it shuts off and that will give you a rough idea of what the charger does.
As for your battery and it's possible damage:
There are a few things that you can do. First, as already suggested, top up all cells and watch them as you charge the battery. If one cell tends to loose electrolyte much more quickly than the others, the cell is bad and the battery is toast. In simple terms (it's a bit more complicated than this) a cell that is bad will be shorted, and the short causes it to get hot, and that boils off the electrolyte. Similary, if one cell seems quite hot compared to others, the battery is toast.
Pick up a hydrometer and check all cells with it after charging and letting it rest with no load for 15 minutes. Any LARGE differences after charging indicate that the battery is toast. If a cell reads partially charged and all others read charged, the cell is in trouble.
If charging for a period of time (overnight) doesn't bring the battery up to an even charge on all cells (as measured with the hydrometer) after 15 minutes no charge, no load, then there is one last ditch effort you can take.
You can equalize the battery. Basically the battery is significantly overcharged in an effort to redistribute the electrolyte and force the sulphur on the plates (called sulfation) back into the electrolyte.
Typically, the voltage applied is about 16vdc, and the equalize is done over about 8 hours. The battery will bubble like mad so remove the caps to allow it to vent. It will give off explosive hydrogen gas, so no open flames...take all precautions to prevent explosion. And it will loose electrolyte so you'll need to top it up during the process. Since it is a high voltage charge, turn off or disconnect all loads. In my case I turn off all breakers, fridge, stereo, instruments, Han radio, everything that is powered is disconnected to prevent damage.
If after a full equalize the battery cells differ substantially when measured with a hydrometer, the battery is history.
It works, but much depends on the condition of the battery. According to the author, it eliminates the need for periodic equalization, too. But it won't rescue batteries with warped plates or shorted cells or those with too much of the plate material gone, or polluted electrolyte.
Aside from attempting to rescue his battery, the OP has got to fix or replace that charger, and adopt a maintenance schedule that includes electrolyte level monitoring.
On 08/17/05 10:50 pm ehsjr tossed the following ingredients into the ever-growing pot of cybersoup:
Now that I know that this is not a "maintenance-free" battery, I'll get into the habit of checking the electrolyte level.
But are you saying that the "Automatic - Deep Cycle" setting on an "ordinary" battery charger (it's one I bought originally for the car batteries, but the "Deep Cycle" setting seemed like a bonus) is not a reliable way of keeping the batery in good shape?
It's quite possible that this charger is not well suited for long-term float charging of a battery, "automatic" or not.
Many standard chargers are designed mostly for "refueling" a depleted battery. They often use a two-step charging algorithm, to perform the "bulk" charge (high initial current level which brings the battery up to about 80% of full capacity), and then a "topping" charge (lower terminal voltage, resulting in a lower current) to bring them the rest of the way up to full capacity. The switchover between bulk and topping charge happens automatically based on the battery's terminal voltage and/or the current level... it's done at a point which trades off the speed of recharge, and the possible loss of electrolyte.
The terminal voltage during bulk and topping charge can often exceed
14.5 volts, and might be over 15 volts depending on the charger design, battery type, and temperature. It's high enough to result in some loss of electrolyte, if the battery gasses rapidly enough that its recombination catalyst can't turn the gasses back into water.
Many of these chargers do *not* incorporate circuitry which will detect the "full charge" state, and switch over to a proper float-charging regime. Proper floating voltage is a good deal lower than recharging voltage, and depends on the temperature... I've seen figures ranging from 14.1 volts (freezing) down to as low as 13.4 volts (40 degrees C). It also depends to some extent on the specific battery type and chemistry.
A two-phase bulk/topping charger is likely to keep the voltage on the battery rather too high for proper floating. Gassing and loss of electrolyte can occur as a result.
For best charging performance, you really want to have a sophisticated three-phase charger, with temperature compensation for all phases of the charging cycle.
As an alternative (possibly cheaper), use your car-battery charger to recharge the battery after use, and buy/build a well-regulated low-current voltage supply to use as a float charger. If your battery will be stored in a location which has a relatively constant near-room temperature, you could build a simple LM317-based voltage regulator, trim its output for 13.6 volts, and be pretty confident that you could float your battery on this without risking excessive outgassing.
We already have strong evidence that the charger you used cooked the electrolyte. I made no reference to the "universe" of ordinary chargers - I was thinking specifically of yours. But you raise a good point, expanding the question - and others have answered.
Whatever charger you use, you need to verify that it is doing the job properly. Consider building an add-on monitoring/control circuit. Perhaps a comparator with a sonalert to notify you that something is wrong with automatic charger shut-off when the voltage exceeds some level. I built a comparator into an ordinary
10 amp charger to turn it on and off automatically. A 339 works fine - 4 comparators in one chip, so you can have a voltage too low output turn the thing on, and a voltage too high turn it off. Still have two comparators left over to use as you like. Add a couple more 339 chips and you could add a 10 step led voltage monitor, for example.
On 08/18/05 04:47 pm ehsjr tossed the following ingredients into the ever-growing pot of cybersoup:
Well, we don't know how much the charger contributed to the problem, because the electrolyte level wasn't checked for more than a year because I hadn't realized that it's not a "maintenance-free" battery.
While looking for a hydrometer today, I noticed "Vector" brand "smart" chargers (10/6/2A and 6/4/2A) that claimed to have 3-stage charging circuitry and to be suitable for car batteries, deep-cycle batteries, and gel-cell batteries. Are these likely to be any good?
The battery was still warm, and each cell was still bubbling slightly after the thing had been disconnected from the charger for about 3 hours. The SG of each cell was pretty much the same at approx. 1.1175, and the voltage across the whole battery was 12.4. When I put it back on charge, the voltage rose to 13.3.
I think the battery is bad. I may be remembering wrong, but I seem to recall that SG should be around 1.230 for lead acid cells, I think. Also, nominal open circuit voltage on a freshly charged battery ought to be at LEAST 12.8 volts.
I can't comment on the chargers you mentioned - I don't know anything about them. But I wouldn't trust any charger until I have verified that it 1) does charge the battery, and
2) does not overcharge the battery. And even that has the possibility of error. A charger that works fine at 50 F ambient may not work right at 80 F. So my testing, at 50 F, may not reveal a flaw that occurs at 80 F. (Or vice versa.) The terminal voltage - the voltage across the battery at which the charge should terminate - varies with temperature.
Concerning your battery's SG: either your SG tester or the battery is bad. The SG reading is too low. To verify, check the specs on your battery with the manufacturer to see what they say the SG should be. I believe the battery is bad, as there is corroborating evidence from other facts besides the SG reading
Regarding my comment that there is strong evidence that your charger is bad: the electrolyte level didn't go down due to leakage. The alternative is that it went down due to evaporation, which is a result of heat, which in turn can be caused by overcharging. As you point out, we don't know how much of the electrolyte loss was caused by the charger - but the only possibility that can be linked to what you have posted thus far is overcharging. Perhaps there are other factors you haven't mentioned?
On 08/20/05 01:37 am ehsjr tossed the following ingredients into the ever-growing pot of cybersoup:
But won't an unsealed (i.e., NOT "maintenance-free") battery lose water by evaporation even if it's not overcharged? Otherwise why the need to check the electrolyte level regularly?
If the charger was disconnected and the battery open-circuited for 3 hours, there shouldn't be any *active* bubbling going on. There may be some bubbles still 'stuck' to the plates, but no new bubbles should be forming. If there is after 3 hours of open circuit, that would be a sign of internal current flow (an internal short). And that would be bad.
SG on lead acid batteries have a couple of different ranges depending on the exact battery details. I've seen 1.250, 1.265 and 1.280 for fully charged.
1.117 seems very low.
The fact that all cells read the same is a good sign. Usually, one cell will fail before the others and so it's SG will be decidedly lower.
Such a low SG makes me wonder if maybe the electrolyte was lost from spillage or something and *not* just discharge and electrolysis. Evaporation and electrolysis just leaves a stronger acid solution chemicals behind and adding distilled water dilutes it back to the proper concentration. Actual spilling of acid from a cell needs to be replaced with new acid of the proper concentration though.
Not meaning to get this tread off on a tangent, but the above comment prompts me to point out that even "maintenance free" batteries AREN'T, necessarily. On many occassions I have found it necessary to peel back the paper cover on automotive maintenance free batteries, remove the exposed cell caps, and add water, especially after a year or two operating in a hot climate. I don't believe marine type batteries would be any different in this regard.
On 08/20/05 05:06 pm Ed tossed the following ingredients into the ever-growing pot of cybersoup:
Just to complicate matters, I eventually found the Web site for these batteries (the only marking on it is "Stowaway Tournament"; I had bought it at Sam's and assumed it was a "store brand," but it's made by -- and acknowledged by -- Exide). Somewhere in the FAQ they say that they are "maintenance free" but also "maintenance accessible." How's that for confusion?
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