Battery Maintenance - De Sulfation
Comments
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Re: Battery Maintenance - De SulfationFirst, the resistive heat loss is proportional to square root of the current, which produces much more heat at faster charge. Second, this is much less time for the heat to dissipate.
I think you mean 'proportional to square of current'. --vtMaps4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i -
Re: Battery Maintenance - De Sulfation
I find there there is very little heat until you reach the gassing voltage. I guess you could supply enough amps where a bank would see the voltage rise so fast that it wouldn't stay in bulk long enough where you'd see some heat. Yesterday I was putting 225 amps into a 1100 amp hr bank @ 12 V, It took 80 Minutes to reach 14.4 V ( Gassing ) and the Temps in the cell readings went from 77.5 F to 80.6 F. , thats not much rise. The 30 Min reading was 77.9 , the 60 minute reading was 79.9.I can confirm that my batteries heat up faster at higher charge rates in bulk mode. And I have an explanation for this. First, the resistive heat loss is proportional to square root of the current, which producs much more heat at faster charge. Second, this is much less time for the heat to dissipate.
Of course, if you heat up the battery to levels seriously above ambient, the heat dissipation will speed up, but that's a totally different question. -
Re: Battery Maintenance - De SulfationChrisOlson wrote: »As Steve (Higgins) from Surrette pointed out, the industry has pretty much adopted the IUIa charging profile for industrial batteries because it's more efficient than voltage-based charging. More efficient means it gets the job done with less heat and torture to the battery.
I think IUIa is popular because it can charge the batt quickly without having to spend too much on a higher Amp charger. And it's not to say there's no other way to charge a battery, IU charging is still used to charge multiple batteries in parallel, which you can't do with an IUIa charger. Here's what the battery technology handbook says about IUIa charging:
Attachment not found.
And IU charging:
Attachment not found. -
Re: Battery Maintenance - De Sulfation
Note that section 12.4.8.4 (1) in the second IU document has an error in the temperature spec...
It calls maximum temp as 35C or 131F... 35C is actually 95F. And 131F is 55C.
95F is probably too low of max temp, and 131 is getting towards the very high side or beyond.
-BillNear San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset -
Re: Battery Maintenance - De SulfationBlackcherry04 wrote: »I find there there is very little heat until you reach the gassing voltage.
That's pretty much what I have seen whenever I graph the log data from my Classics. Very little temp rise until the bank gets up to within a couple volts of Absorb voltage. If the voltage stays at Absorb -2V for a long time the batteries will get hotter than they do if there's sufficient incoming power to get them to Absorb voltage and get the job done. But I use higher Absorb voltage than most people do. So for most folks Absorb -2V (or -1V on 24V system and -0.5V on 12V system) might not cause much of a rise in battery temp like it does for me.
The way I have stopped this phenomenon is to set the AUX offset lower in the Classics so that it brings the water heating online sooner and keeps the voltage at Absorb -3V to Absorb -4V. This keeps the batteries in the cooler running range until the stats kick the water heaters out. Then on a good day, with the water heating load finally off, it zooms right up to Absorb voltage and gets 'er done.
YMMV, but it definitely keeps my batts 5C cooler doing it that way.
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Chris -
Re: Battery Maintenance - De SulfationI think IUIa is popular because it can charge the batt quickly without having to spend too much on a higher Amp charger. And it's not to say there's no other way to charge a battery
I like how Steve Higgins put it in another thread - no two systems are going to be alike. So it's almost impossible to publish a single charging profile that will work for all situations. And yet, that's what most people who have off-grid battery systems assume, that what it might says in a manual is going to work for the way they cycle their batteries. It just doesn't always work that way.
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Chris -
Re: Battery Maintenance - De Sulfation
What I have is a voltage disconnect switch, I bulk in the 225 - 250 Amp range and as I reach gassing ( 14.3 V @ 12V nominal ) I drop 150 Amps of charge potential and finish off with 100amps. Basically the chargers would start cutting back on their own, but I don't need that many amps to finish absorb. My interest is purely financial based on fuel consumption. The temperature readings come from a probe immersed in the electrolyte at the plate level , I feel confident in them.ChrisOlson wrote: »That's pretty much what I have seen whenever I graph the log data from my Classics. Very little temp rise until the bank gets up to within a couple volts of Absorb voltage. If the voltage stays at Absorb -2V for a long time the batteries will get hotter than they do if there's sufficient incoming power to get them to Absorb voltage and get the job done. But I use higher Absorb voltage than most people do. So for most folks Absorb -2V (or -1V on 24V system and -0.5V on 12V system) might not cause much of a rise in battery temp like it does for me.
The way I have stopped this phenomenon is to set the AUX offset lower in the Classics so that it brings the water heating online sooner and keeps the voltage at Absorb -3V to Absorb -4V. This keeps the batteries in the cooler running range until the stats kick the water heaters out. Then on a good day, with the water heating load finally off, it zooms right up to Absorb voltage and gets 'er done.
YMMV, but it definitely keeps my batts 5C cooler doing it that way.
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Chris -
Re: Battery Maintenance - De SulfationI think you mean 'proportional to square of current'.
Yes. That's what I meant.
I found that I get heating when current is high during bulk. I once turned on a generator too early and sun came up unexpectedly and I've got high current (24%) for an hour. The temperature rose by 8 degrees C in an hour.
In contrast, at higher voltages, I didn't see that much heat. At 59-60V absorptions there was no heat whatsoever. At 64V, there's some heat, but not much, it would take many hours to go up by 8 degrees C. -
Re: Battery Maintenance - De SulfationYes. That's what I meant.
I found that I get heating when current is high during bulk. I once turned on a generator too early and sun came up unexpectedly and I've got high current (24%) for an hour. The temperature rose by 8 degrees C in an hour.
In contrast, at higher voltages, I didn't see that much heat. At 59-60V absorptions there was no heat whatsoever. At 64V, there's some heat, but not much, it would take many hours to go up by 8 degrees C.
This makes sense of course because the battery's resistance is lowest when discharged; hence more current flows which equals more heating.
I think the whole "charge 'em quick" notion is to get the heating part over with ASAP and then let them start to cool. In a perfect world the high current would be done by the time the batteries hit the maximum temp and then the heating affect would drop off rapidly before that point was exceeded.
The thermal cycling of the plates is probably a lot more complex of an issue than it appears, and no doubt depends on exactly what they made those plates out of too. -
Re: Battery Maintenance - De Sulfation
If bulk voltage on your batteries is above 57.2 in your case, I am sure you'll see heating. Thats why I keep the high input current below the Gassing voltage. If you can show me something different, I am listening.Yes. That's what I meant.
I found that I get heating when current is high during bulk. I once turned on a generator too early and sun came up unexpectedly and I've got high current (24%) for an hour. The temperature rose by 8 degrees C in an hour.
In contrast, at higher voltages, I didn't see that much heat. At 59-60V absorptions there was no heat whatsoever. At 64V, there's some heat, but not much, it would take many hours to go up by 8 degrees C. -
Re: Battery Maintenance - De SulfationCariboocoot wrote: »The thermal cycling of the plates is probably a lot more complex of an issue than it appears, and no doubt depends on exactly what they made those plates out of too.
Getting a battery manufacturer to actually tell you what the composition of the plates are in their batteries usually doesn't happen. It's like it's a big Trade Secret or something. And if you talk to manufacturer A they got the biggest and thickest and most heaviest duty plates. If you talk to manufacturer B they got the same thing. And they all got special names for the Super Duper HydroSorb Separators, or whatever, in their batteries.
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Chris -
Re: Battery Maintenance - De SulfationBlackcherry04 wrote: »If bulk voltage on your batteries is above 57.2 in your case, I am sure you'll see heating. Thats why I keep the high input current below the Gassing voltage. If you can show me something different, I am listening.
During bulk stage, voltage is usually 54-55V. At 100A current, I see about 2 C increase per hour. Once, at 160A current, I saw 8 C in one hour.
As absorption nears, voltage goes to 64V rather quickly.
During absorption at 64V (tapering current from 80-100A to 15-20A) I see increase of 2-3 C during the whole 4 hour absorption.
So, voltage doesn't affect heating as much as current does. -
Re: Battery Maintenance - De Sulfation
How are you measuring it ?? In the cell at the electrolyte level ?? There is not a BTS that I'd trust at high current. The on the post sensors are effected by the heat in the cables from that much current @ 48 V. The ones on the battery case have to much lag. It's odd that you see that kind of heat below gassing. Voltage is everything about a battery. How you know when you'v finished the bulk stage ?? I have no idea how you decern the two when you raising the voltage of the battery 6 + volts above the gassing level to absorb trigger.During bulk stage, voltage is usually 54-55V. At 100A current, I see about 2 C increase per hour. Once, at 160A current, I saw 8 C in one hour.
As absorption nears, voltage goes to 64V rather quickly.
During absorption at 64V (tapering current from 80-100A to 15-20A) I see increase of 2-3 C during the whole 4 hour absorption.
So, voltage doesn't affect heating as much as current does. -
Re: Battery Maintenance - De SulfationBlackcherry04 wrote: »How are you measuring it ?? In the cell at the electrolyte level ?? There is not a BTS that I'd trust at high current. The on the post sensors are effected by the heat in the cables from that much current @ 48 V.
I use Xantrex BTS. I have no idea how accurate it is. I don't think cable heating is a problem because I monitor cooling too and it is always very slow. Heated cable would cool down very quickly after the charging is over. -
Re: Battery Maintenance - De Sulfation
All I am saying is if your seeing 8C temperature rise @ 54-55 volts it's something I have never seen. Although 160 amps @ 48 v would equate to 640 amps @ 12 V, that is big current, something is going to heat up. Cable would cool down fast , but your not stopping at some bulk voltage, your charging batteries full cycle I assume.I use Xantrex BTS. I have no idea how accurate it is. I don't think cable heating is a problem because I monitor cooling too and it is always very slow. Heated cable would cool down very quickly after the charging is over. -
Re: Battery Maintenance - De SulfationBlackcherry04 wrote: »All I am saying is if your seeing 8C temperature rise @ 54-55 volts it's something I have never seen. Although 160 amps @ 48 v would equate to 640 amps @ 12 V, that is big current, something is going to heat up.
If battery internal resistance is 25 mOhm, 160A current will produce 630W of Heating power. Figuring out the ripple, it's close to 1kW. Looks capable of increasing temperature by 8C.
Perhaps your battery are not discharged enough to accept big current at 54-55V and the voltage goes up right away.Blackcherry04 wrote: »Cable would cool down fast , but your not stopping at some bulk voltage, your charging batteries full cycle I assume.
In winter I usually stopped the charging as soon as voltage goes up (e.g. 58-59V), execpt for weekly full charges. -
Re: Battery Maintenance - De Sulfation
Quick note about bulk current from East-Penn / Deka
In their tech manual for their VRLA products (1927.pdf) they mentioned that for the longest life, they recommend getting as close as possible to 30% of the 20hr rate for bulk current. (I note for their flooded 2V, 20% is the limit in another doc 1913.pdf) while maintaining voltage and temp comp.
Aside from safety precautions, it is the only statement I've seen from a manufacturer that has a current limitation on a product actually say it was beneficial to get close to the limit.
I wish they went into more detail about how beneficial it was and under what circumstances, but there it is ... -
Re: Battery Maintenance - De Sulfation
For those whom are 'Treky' fans. StarTrek Next Generations dealing with sulfation
On the more serious side, I thought about the association with the episode "The Crystaline Entity".
Even if you believe the theories about resonating the sulfate crystals to break them up, (as done on The Crystaline Entity) you have got to think about the broad range of variance in conditions between battery AH size and condition of battery. Tuning the amount of current and frequency of current would likely be very unique to a given battery. One-shoe-that-fits-all size batteries desulfator seems improbable, even if you believe in the vibrating crystals to breakup theory.
My opinion, is at best, you may be able to break off a sulfated chunk so it might settle to the bottom of battery so you at least expose free lead left deeper in plate. It will have eaten some of the plate and permanently tied up some of the battery acid but clearing the plate is better then having it insulated by hard sulfate.
This can usually be accomplished with a short period (20 to 45 mins) of a high current charge of 25-35% C rate on a partially discharged battery.
---expecting a Treky reply to contest the incorrect name of the episode name. FYI, it was not "the crystaline entity". -
Re: Battery Maintenance - De SulfationThe Enterprise intercepted the Entity after it had killed the entire crew of a freighter, the Kallisko. They attracted the Entity by emitting graviton pulses at ten per second from the Enterprise, as lower pulse rates had no effect on the creature. The creature approached the Enterprise, replying with a series of graviton pulses that the Enterprise crew interpreted as meaningful, but which it needed time to decode. Marr increased the pulse rate, eventually trying a continuous graviton emission. The Entity stopped emitting pulses of its own as the emissions drove it into resonance. The Enterprise crew tried to stop the emissions, only to find that Marr had isolated the access code for the emission controls. Before the crew could halt the emissions, the resonance shattered the Entity. (TNG: "Silicon Avatar")
Google is a wonderful thing. -
Re: Battery Maintenance - De SulfationThis can usually be accomplished with a short period (20 to 45 mins) of a high current charge of 25-35% C rate on a partially discharged battery.
Maybe this is what East-Penn/Deka is saying about getting as close as you can to 30%C for longest life..
I think Scotty was the one doing all the battery equalizing / desulfating. He sure was obsessed about Di-Lithium crystals. I guess we'll never solve the sulfation issue.
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Re: Battery Maintenance - De Sulfation
blame it on the clingons. (spelling deliberate.) -
Re: Battery Maintenance - De SulfationCould also be an effect of corrosion of positive plates ....
I think this is the crux of the issue. Any battery that has sat around in a deep discharge condition long enough to have HARD sulfation, is also suffering from grid corrosion from the acid attacking the grid. So even if the pulse technique proved to break up hard-sulfation, there is nothing it can do to restore a corroded grid(s), and you are left with a battery that has much less capacity than it did before, (in addition to the hard sulfation!) and gambling on a failing grid or worse corroded / cracked bus and playing the odds with imminent failure.
If you've got a *hard*-sulfated battery, time to call it quits and start over unless you want to just play around reviving a zombie.
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