Lead acid batt analyser

[Mosaic]

The battery has its own RLC parasitics and, once pulsed with a sharp cut off, produces its own kick back oscillations of around 3-5Mhz, thus what they're saying is not true. They ignore that a pulse excites the battery for a few milliseconds of oscillations.
But, of course, they sell battery vitamins.

 

[NorthGuy]

The battery has its own RLC parasitics and, once pulsed with a sharp cut off, produces its own kick back oscillations of around 3-5Mhz, thus what they're saying is not true. They ignore that a pulse excites the battery for a few milliseconds of oscillations.
But, of course, they sell battery vitamins.

You don't really know if the voltage ringing you observe is at your connection points, at battery terminals, at plates, or somewhere deeper. Therefore, there's no proof that the battery gets excited.

You can, however, try to plant voltage probes directly on plates and see if you get ringing in there or not.

Or, if you're willing to risk it, you can put a small (e.g. 50mOhm) resistor into your device instead of the battery and see if you get the same response as with the battery.

 

[nsaspook]

The battery has its own RLC parasitics and, once pulsed with a sharp cut off, produces its own kick back oscillations of around 3-5Mhz, thus what they're saying is not true. They ignore that a pulse excites the battery for a few milliseconds of oscillations.
But, of course, they sell battery vitamins.

The amount of RF energy absorbed by the battery to do 'work' from these oscillations is tiny. The reason it rings is because the energy is being stored in the battery circuit reactive parasitics instead of being absorbed because of an impedance mismatch and is being coupled to space or the wiring.

 

[Mosaic]

After further work, observation and development I have formed a new position on the processes involved.

1) The pulsing isn't the desulfation mechanism, the impressed average voltage level does the equalization. However, pulsing has other overall benefits.
2) The morphology of the plate structure is improved by reflex charging, however, for badly degraded batteries the cycle needs to be very slow for the latency of the chemistry to work. This compensates for low ion electrolyte.
3) Conservation of energy (noting pulse duty cycles) with a loss compensation of about 33% allows a direct & repeatable correlation between pulse current amplitude and average charge current.
4) High current pulses can breakdown dendritic formations (soft shorts = self discharge) which show up as hotspots in cells under charge as observed by FLIR imaging. It takes several hours for this to resolve.
5) Millions of high current pulses 'self test' a battery's ability (conductor & plate integrity & durability) to deliver cranking currents when correlated with cell level thermal profiling.
6) On the fly load testing is required to verify the removal of soft shorts or the presence of hard shorts.
7) High current pulses with temperature control serve to quickly (I*I*R) heat the electrolyte in high resistance cells; delivering optimum electrochemical activity /ion mobility and faster battery recovery than DC methods.

I am at hardware version # 21...lost count of firmware revisions months ago. The bench testing of the automated recovery and re rating systems continue. I am almost ready to enter the beta testing phase and setup a pilot project for commercial recoveries.

I think the system is better termed a Switch Mode Integrated Dedendriting Equalizing Recovery System - SMIDERS

 

[nsaspook]

I think the system is better termed a Switch Mode Integrated Dedendriting Equalizing Recovery System - SMIDERS

Find a better name.

 

[Mosaic]

Ok. let's see.
Switching Pulse Integrated Dedendriting Equalizing Recovery System
SPIDERS

 

[NorthGuy]

After further work, observation and development I have formed a new position on the processes.

Great job!

How common are soft shorts compared to dead ones?

 

[MrAl]

Hi,

I had an old battery that was well past it's rated life time that would go low on voltage. By charging it at a higher than typical voltage it would recover for a while, and work normally in a regular application. The voltage would fall slowly over time though, after being charged and discharged. Another boost with the higher voltage and it was ready to go again. Too bad this was only one piece so there's no statistical data collection possible.

 

[Mosaic]

The failure mechanism being resolved is a combined issue. First, a poor charging regimen starts accruing sulfate. This leads to a slow loss of capacity which is not usually noticed on an SLI battery. Especially one that is a bit over-sized for the application. The sulfate after some time changes chemical state to the 'hard' crystals and over more time this growth can cause dendrites which become soft shorts. While these dendrites are forming, the increasing sulfation of the battery slows the charge acceptance, further compromising the inadequate charging regime thereby speeding up the sulfation.

When the dendrites achieve a soft short (inter plate) condition the battery will appear to 'lose' charge fairly quickly, even if its residual sulfated capacity is sufficient for the application (SLI). This is usually when the user has to replace the battery.

MrAl If your battery responded to equalization then it is slowly sulfating and the loss of plate area will cause the apparent voltage drop due to internal resistance losses. Sudden voltage drop (overnight) implies a soft short.

If a battery suffers a mechanical or corrosion failure a 'hard short' or 'hard open' can occur. The hard 'short' requires a charge and load test cycle to detect while monitoring voltage, a voltage drop in multiples of 2.2V is a sure sign. The hard 'open' will see the cell gassing under load or a very hot spot (I*I*R heating and gassing) under charge. A load test will see the battery voltage collapse in a couple seconds as the electrolyte bridging the 'open' decomposes under the reverse current and emits hydrogen/oxygen and loses its ability to conduct.

A fracture in the grid or buss bars can create a tiny 'open' condition which requires a a significant load to detect. One that exceeds the electrolytes conduction capacity.

A battery left undercharged for many months will develop a LOT of hard sulfate and this will swell the plates and warp them; occasionally swelling the battery case as well in bad cases. This warping will cause both hard open and hard 'short' conditions to occur as well. Such batteries are well past recovery.

I have recovered 12V batteries with voltages as low as 3V at rest with no additives which brings up another grey area.

On the topic of additives which I have also investigated the 'recovery' mechanism requires an electroplating process. This is a double edged sword.

Early: A sulfated negative plate will have fissures in the sulfated paste which permit some capacity. Electroplating (usually cadmium sulphate additive) these fissures temporarily improves their conductivity and gives better electron access to 'lost' islands of active plate material. This causes an apparent improvement in battery capacity and cranking amps after a few 'full' charge/discharge cycles permit enough electroplating to occur.

Late: After many more SLI battery cycles which are mini charge/discharge cycles the electroplating can start to coat the plates to a point where normal plate function is compromised and the battery is truly dead.

This analysis is supported with the addition of copper sulphate instead of cadmium sulphate to a battery. The copper plating progression (-ve plates) is easily visible and progresses 'downward' from the buss bar into the plates over the charge cycles.

In the case of 'EPSOM' salts or MgSO4 , the Mg will not plate due to its high reactivity. What it does though, is it competes with the lead for sulphate ions (ion swapping) and, being very soluble, interferes with the solid lead sulfation mechanism at the plate surface. Also it increases the inherent conductivity of weak electrolytes. Thus it can help a weak cell IF it is added BEFORE dendriting occurs; how much 'help' is unknown. I don't have long term comparisons for the use of Epsom, but it seems to increase plate corrosion and water loss thus buying only a little time. This is possibly due to its electrolytic nature. Thus adding MgSO4, CdSO4 or CuSO4 et al to a new battery as 'insurance' is not useful at all in the long term.

 

[MrAl]

Hello again,

The battery i am talking about seems to have developed a series resistance that changes over time, becoming higher as the charge depletes and then is replenished with a 'normal' charge regimen. As the resistance increases, the normal charge voltage is not high enough to restore the original charge so it never gets fully charged. Only after a higher voltage charge does the charge return to normal, and then it starts to take a charge at the normal charge levels again. Only after taking a charge at the normal levels over time does the voltage drop, and that is attributed to the fact that it is not getting the full charge because of the higher internal resistance, which is not high to begin with but increases as time goes on. Interestingly, the resistance seems to go down as it is charged with the higher voltage. The higher voltage only needs to be about 1v higher too, or alternately a standard voltage applied for a longer time period than normal. But either way the resistance goes back down, then after several charge and discharge cycles it goes back up. This occurred a number of times in the past.
Also, this battery was once discharged to 0v but it is unknown what caused that. It could have been a light left on for example.

 

[Mosaic]

Yes, well you need to equalize and check the Spec. grav. of the cells. Make sure your EQ is complete (std deviation < .030 SG) or the prob will recur.

 

[NorthGuy]

Are the most failures you see due to sulphation (undercharge)?

How often you see corrosion damage - deteriorated positive plates with lots of material (lead/lead oxide) settled on the bottom and cousing shorts? Is there any way to fix that?

 

[Mosaic]

Most of the failures ( 2/3rds) are not repairable, either advanced sulphation & dendrites distorting the plates or positive corrosion and plate shedding (wear and tear). If enough shedding has occurred to short the cell, it's near end of life.
I suppose if I focused on deep cycle batts I'd see more sulphation failures vs shedding/corrosion failures.

I once drilled a batt. case with a 'hard short' due to suspected plate shedding to drain the highly conductive 'black' fluid from the bottom. I didn't achieve much.

Most batts have a single 'bad cell' ..sometimes I wonder about the 'throwaway' culture we have developed. If the cells were replaceable as they once were it would save a lot of acid recycling and wasted energy re-smelting lead etc.

 

[NorthGuy]

I regularly overcharge my batteries, once every 7-10 days I do 4-6 hours at 2.67V/cell, so I think they don't sulphate at all, SG stays high. But I'm worrying about corrosion - there are some signs - like small dark particles in electrolyte, which I guess is lead oxide. Who knows how long it would take for it to settle on the bottom and cause a short. Only time can tell.

 

[Mosaic]

What size batteries do you use?

 

[MrAl]

I regularly overcharge my batteries, once every 7-10 days I do 4-6 hours at 2.67V/cell, so I think they don't sulphate at all, SG stays high. But I'm worrying about corrosion - there are some signs - like small dark particles in electrolyte, which I guess is lead oxide. Who knows how long it would take for it to settle on the bottom and cause a short. Only time can tell.

Hi,

You could try vibrating the battery. That can help level out any particles on the bottom as long as they are not stuck together too well, and thus even out the level of particles. if they came mostly from one cell this can help a lot. If they came from all cells then it might help extend the life somewhat if there are still high spots.

 

[NorthGuy]

What size batteries do you use?

About 700AH.

 

[dr pepper]

Plate warpage is also a failure mode with lead acids, a quick check with a ruler or straight edge across the sides gives you an indication of a problem, the side of a battery bulges when warpage is bad.

 

[nsaspook]

I've got a 12vdc 4 costco GC2 400Ah battery bank that's on it's last legs but it's been a good run (date code 2/12) for the amount of 50%+ murder cycles over the years.

Like NorthGuy I like to overcharge the set just a bit above the recommend SG, yes it causes some erosion but if you use solar to charge you need it done the quick way not the best way at times. Use the right battery for the application. Traction style batteries are designed for charge/discharge abuse over long periods, for this you lose some voltage and coulombic efficiency but gain it back in total Ah storage for the life of the battery as higher long term and less peak output without damaging the plates. Most of this research seems to be directed at automotive 'cranking' type applications so I don't know how well that will translate to energy storage applications.

 

[Mosaic]

Find a better name.

Another update:

The current project code name is ION HAMMER.

The latest 55b24 (370 CCA, 42AH, JIS) battery processed, took 26 hours, fully automated and the data went like this:

Initial SG AFTER 12 hours 400mA precharge: Spe. Gravity - all cells under 1100 and a cranking amp rating of about 155CCA, resting V = 11.78V. Observations of the buss bars showed glittering crystals on the grey bars and white crust on the positive bars. Clean electrolyte, good levels.
26 hours of fully automated recovery consisting of 13 distinct phases including test & rest phases resulted in all SGs over 1270 delivering 457 CCA with 37Ah capacity. Resting V after 12 hours, is now 13.00V
Observations of the buss bars now show matte gray negatives and a crusty white 'shell' on the brown positives. This shell appears to have 'cracked' away indicating possible shrinkage of the buss bar. Such shrinkage can be due to inter granular corrosion reversal.

This batt. is one of my better results ( CCA > OEM, Ah = 90% OEM) and I figure it was a good batt. that was allowed to sulphate due to lack of use as opposed to an abused batt. It's the 31st processed for this particular model of battery.
Total recovery energy used = 55Ah or 148% actual Ah rating.

Often, old sulphated batts have 'shed' sulphate due to paste/grid growth which results in post recovery electrolyte weakness. Even so these battered batteries remain serviceable after recovery, albeit with a bit lower capacity.

One the difference with storage batteries: Quote from:
https://evbatterymonitoring.com/webhelp/section_2.htm
Batteries designed for low-rate applications, such as for storage in solar power systems, contain a larger amount of acid in proportion to plate-active material. They are designed to be plate-limited when used beyond their rated capacity. No plate materials will be available for releasing usable energy. Batteries designed for high-rate applications, such as automotive ignition, etc., have a smaller amount of acid in proportion to plate-active material. They are designed to be acid-limited when used beyond their rated capacity

Thus I would postulate that storage batteries would have better recovery characteristics even with sulphate shedding. I will start testing those soom, when i can obtain some defunct units.