Burning Out Batteries --- Going back to Wet Cell

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Diagnosing a weird issue in the wife car......Regardless, I've got 2 High End AGM as paperweights.....

Going back to flooded or just a *cheaper AGM*.
Flooded has similar warranty, can be *topped* off with fluid, CCA and reserve is a smigen more than their AGM counterpart. Pricewise, I'm okay with either (East Penn's Deka AGM versus flooded G49).

Aside from Discharge, for a daily driver, any empirical reason to go with AGM.

I'm not spending coin on another High AGM battery, even though I think I have the ~issue~ that was causing it resolved.
 
No, there is no reason to go AGM really, IMO.

Yes, I do use them. My basic reasoning for using them is if the battery is in the trunk, there is less chance of releasing corrosives in a confined environment.

Ive used one under hood before on my saab, but there's really no good reason to do so.

Ive run a group 49 in my 318i, and an H6 in my saab, without issue, from 2008, and they were just perfect when I sold the cars a few weeks back. The 318 was a daily driver and the saab was a long trip car kept on temperature compensated float low and slow otherwise...

When you told that the vendors really want you to hit the battery with higher current, it had me concerned. The reality is that while AGM has nice low impedance and low self discharge and a variety of great characteristics, they too can be very sensitive. They will gas, and if you form gas too fast due to a high over potential with high current, they will burp, and you're not getting that electrolyte back.

There's also something to be said about a use profile that causes perpetual undercharge or consistent float voltage that is higher than needed...

Have you tested mass new vs end of life to see if there was a change?
 
If AGM batteries were really superior the warranty would be longer than flooded cell batteries. But its not. More expensive for same (or close) warranty.

Maybe good for boats where the location makes it a PIA to get to.
 
Originally Posted By: JHZR2

When you told that the vendors really want you to hit the battery with higher current, it had me concerned. The reality is that while AGM has nice low impedance and low self discharge and a variety of great characteristics, they too can be very sensitive. They will gas, and if you form gas too fast due to a high over potential with high current, they will burp, and you're not getting that electrolyte back.




JHZR2. OT, but call up Odyssey, Lifeline or Northstar and speak to them about what is their preferred charge profile.

The battery issues I have now are not related to that statement....been running Odysseys for years on different cars. Just so happened, I burned up 2 brand new ones in less than 3 months.....as I thought the 1st issue was resolved but sadly, it was a different issue that caused the 2nd going out...

This post was just me mulling as I did not want to risk another $$$ battery after being sour about the recent battery issues....so I'm leaking on just a regular East Penn flooded or AGM. Cost between the 2 is not much different. As with most flooded counterparts, the CCA and Reserve specs are always a bit bitter than their AGM counterparts. AND I get to pop those caps open and top off if I need...
 
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Originally Posted By: chefwong
Originally Posted By: JHZR2

When you told that the vendors really want you to hit the battery with higher current, it had me concerned. The reality is that while AGM has nice low impedance and low self discharge and a variety of great characteristics, they too can be very sensitive. They will gas, and if you form gas too fast due to a high over potential with high current, they will burp, and you're not getting that electrolyte back.




JHZR2. OT, but call up Odyssey, Lifeline or Northstar and speak to them about what is their preferred charge profile.

The battery issues I have now are not related to that statement....been running Odysseys for years on different cars. Just so happened, I burned up 2 brand new ones in less than 3 months.....as I thought the 1st issue was resolved but sadly, it was a different issue that caused the 2nd going out...

This post was just me mulling as I did not want to risk another $$$ battery after being sour about the recent battery issues....so I'm leaking on just a regular East Penn flooded or AGM. Cost between the 2 is not much different. As with most flooded counterparts, the CCA and Reserve specs are always a bit bitter than their AGM counterparts. AND I get to pop those caps open and top off if I need...






I'm way beyond calling those folks. I have labs and arrays of these things at up to 1000v operating to explore degradation, mass loss, impedance rise, etc. Boiled electrolyte plenty of times...

There's right and wrong to every story. I've seen plenty of AGMs condemned on impedance for marginal misuse, and others in use for years.

Since it was in the X5, was the type and capacity of battery properly coded into the vehicle, and then He new battery registered as new? When I took my 135i over to group 49 agm (done for low self discharge and due to trunk placement), I had to do both.
 
LOL. JHZR. So you're telling me that what the manuf. calls out for their charge profile for their batteries is bu11sh1t ? And whatever empirical testing they have done in house or in their own or 3rd party lab is all wrong....

Even with the brake regen....on these cars, I hook up the chargers to them to ensure the batteries are consistently topped off...

------

Josh, I'm not 100% sure if the issue is resolved, so can't report back on my resolution as I'm not sure if that was the root cause....will find out after I trend it for a couple of fays
 
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You can lol all you want. I kill batteries, I fund fundamental research and also have found lots of things wrong.

We have killed plenty of batteries doing vendor approved stuff.



As I said, stuff may be right, but not all the time. We've killed plenty of batteries to prove it.

I'm going to a battery development meeting with a premier developer and builder of high end batteries. You're calling an applications engineer reading approved material. Not having a trump card contest with you, but you might accept insight that others have because some of us have millions invested in this technology and have a job to know and do experimentation and learn the unknowns of fairly unknown chemical systems.

So did you code AND register the batteries to the vehicle??
 
JHZR
No Hard feelings....
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All I'm saying is with some of the mauf. mentioned, they have published documentation on how their batteries like to be charged. I never said it was like that for all AGM batteries. Take one of their batteries and discharge it to 10.5 volts. Trickle charge that at 5 amps. Do the same battery at 40 amps......If their testing shows and documents they want a high amp charge during bulk, then I'm going to heed manuf. advice. Unless you're telling me they are advising as such so I can cook out my battery and buy more of their batteries ;-/
 
Ditto!

Yes, there is some literature and some basis for allowing a rapid charge at the start, especially when depleted.

AGM lead acid has a low enough impedance that it will allow a pretty substantial current inrush. In a range from, say 20-80% SOC, it can be done.

But here's the thing... Remember that the Voltage to charge the battery is:

Vcharge=Voc + I*R

Where Voc is the open circuit voltage rested and disconnected at chemical equilibrium, and I is the current, R is the battery DC impedance.

So rearrange algebraically, you get:

Vcharge-Voc=I*R

Or I = (Vcharge-Voc)/R = I = DV/R

Which is consistent with Ohm's law.

So what happens is that for a given R, the bigger that you want I to be, the higher DV (Delta V) needs to be.

So what happens is that you need to drive higher and higher voltage to get more current in.

Look at the Odyssey 65-PC1750. It claims to be a 2 mOhm (0.002 Ohm) battery. The short circuit voltage is 5000A, and if I=V/R and we assume a depleted conduction voltage of 10V then 10/0.002 = 5000. That's good, it means that we have a DC impedance value, not a 1kHz AC impedance (for which a DC resistance is 2-3x higher).

Lead acid batteries have a changing impedance with state of charge, with higher impedance at low SOC.

partone-22f.jpg
(source: battery university).

What does that mean? It really means that a higher impedance is found at low SOCs than the nameplate.

So let's do an example...

If we want to get 20A into that battery above with 4mOhm impedance when it is discharged to 11.5V, we need to get:

Vcharge = 11.5 + 20*0.004 = 11.58V

Not bad, huh?

Yet youll find that chargers do a few things... First, they will PWM the input. So if youre talking 20A in, it may well PWM a 100A circuit 1/5 of the time. What happens then? Your 0.08V charging force becomes 0.4V, and the 11.5V battery is seeing 11.9V for a short time, though their chemistry doesnt necessarily want that. Smaller chargers likely can't do that, but you have to see.

Beyond that, what kind of rectifier is used? Some DC waveforms can look like this:

diode18.gif
(source electtonics-tutorials).

Now imagine where this puts us... PWM plus some really lumpy DC that has a peak that is much higher than RMS.

Where does that put us?

It creates the opportunity for some really high intermediate voltages, with some really high voltages on the double-layer capacitance inside the cell, because the chemical reaction cant occur fast enough, especially in electrolyte starved batteries like AGM, and especially if the electrolyte starts to be lost due to use. Remember that lead acid batteries can and will polarize which means that the electrolyte can be starved of reactive species. Continued loading or forcing of charge has to go to the electrolyte, because there isnt enough material in the reaction to proceed as desired. The practical and observable embodiment of this is exactly why lead acid batteries can have very high capacity in Ampere-hours at a 4-10 hour constant current discharge, but can have a small fraction of that capacity if discharged at a proportionally higher current for just a few minutes. For example, look at the Odyssey PC 310 battery. Over 20 hours, you can pull 0.4A for 5W, and get 8.6Ah. At a discharge rate of two hours, 10% as long, you can pull 3.2A for 41W and only remove 6.5Ah of the capacity. Over 15 minutes, roughly 1% of the duration of the 20 hour experiment, you can pull 19A for 236W, but you can only retrieve 4.8Ah!

That's real, and practical... See it here, page 4: http://www.odysseybattery.com/documents/US-ODY-TM-002_1214.pdf

And the same is the case on charge. There is only so much material available for the chemical reaction. The system is not in equilibrium. But the issue is that under charge, you are at even higher overpotentials, which means that you move asymptotically up on the gassing rate for decomposition of water, and the low overpotential of the lead reactions arent occurring fast enough to compensate.

So consider that chargers will often put out a current-limited but higher voltage than is required. Remember that water will decompose at any voltage above approximately 1.22V, and these fixed current chargers, putting out >13V on a depleted battery, where the >13V is really RMS, and the peak is higher, corresponding to the PWM current, means that there is a lot of opportunity for corrosion and gas evolution. Especially when the charging overpotential required is really low, and so the lead can react and go back with a much lower voltage, and there is just a ton of excess voltage and current.

This is why AC ripple, clean, stable output, and other considerations are so critical from the power electronics side of a charging system.

A utility UPS that can get 15-20 years out of monoblock AGM batteries under climate controlled storage does so because there is negligible ripple from the 12+ pulse rectification (plus filtering) coming from three phase utility power off a zig-zag transformer).

Have you put your charger output through an oscilloscope to see how it behaves? Keep in mind, Im not talking pulsed charging of the battery, Im talking PWMing of the output current from a fixed source to achieve a certain output.

Keep in mind also, that these things are not magically free to do what you want. Most vendors recommend ensuring that a temperature rise of over 10C is avoided. It can be real tough to measure this, especially since the inside of the battery is where it really matters. Many also recommend bringing them back carefully, limiting charge to say, 5% of their 10 hr rate, and limiting temperature rise. example:

https://www.cdtechno.com/pdf/ref/41_2128_0212.pdf

So my point after all this rambling is that you may think youre doing the best possible thing for the battery, following guidance, etc., and actually not doing well for it at all, either due to ripple, dc waveforms, temperature rise, etc. This can cause gassing that burps from the battery, plate corrosion, dryout, and even thermal runaway if sustained. Not saying youre doing any of those things, but you do need to be a bit careful. Not all chargers or power electronics necessarily do the right thing or exactly what an RMS (or refresh rate) meter claims...

And did you register and code the AGM battery to the car???
 
Yes, new batts were registered but during the course of 3 months, and the 2 new batteries + the 3rd new one in there as of last Friday, I'm still f'ing with the issue. I'd rather chase down a mechanical issue than a electrical issue all day ! Something doesn't really add up between the 1st incident and the 2nd incident.....and while all prelim. diags does not point to the alt, when you look at problem and how it manifest it, it seems like it's the alt. Monitoring the alt, v and amp looks fine. Sometimes I just want to go pound sand
 
Frustrating for sure!

What made you think that an AGM, and especially an odyssey, was needed? Did you try to go really light with an undersized battery or something?
 
I've dabbled the idea of a Braille in the track rat but nope, battery was the usual fare with plenty of reserve cap.

And yes, $ for value, wet cells can go 7, maybe even 8 years easy if properly maintained and cost a hair over a Benjamin, with the rise in lead prices, leading to price rises in Batteries as a whole.

I've been running Odyssey for years...I use to travel alot and the discharge factor led me on the Odyssey route. Stuck with what I know works so 12V battery replacements have always been a Odyssey since then --- even though I know that a cheap wet cell will probably do the same purpose for a fraction of the price....and also have a slightly better spec on CCA and reserve

But after having burned up $600+ in lead in 3 months, I am going back to what I always knew but never really did , which was wet cell. $ wise, a JC wet cell, or Deka Wet Cell / AGM pretty much the same costwise in a G49. I'm leaning on the Deka's
 
Dang JHZR2, impressive knowledge there.

I've been deep cycling a Northstar group27 AGM. Recharging sources are a 40 amp adjustable voltage power supply, Alternator whose regulator allows upto 14.9v, and 200 watts of solar with MPPT adjustable charge controller along with a shunted amp hour counting battery monitor.

Fully recharging by Solar alone and only solar, after 5 deep cycles to 50% or less, and the voltage held during discharge on cycle 6, for the same AH removed, is noticeably worse than cycles 1-4.

40+ amps applied until 14.46v is reached and then held until amps taper to 0.4 amps restores lost performance. When on Solar my charge controller is programmed to drop to 13.6v float only after amps have tapered to this same level.

14.9v is well over Northstar's 14.46v recommended absorption voltage. My battery monitor has shown the battery accept 0.0 amps at 14.9v. Obviously the battery was bursting full but my vehicles VRegulator decided to hold 14.9v anyway. Obviously 0.0XX ?amps were required to hold the battery at 14.9v but I do not believe the vents opened. It seems to come to a hard stop amperage wise when fully charged even at 14.9v. Will not push voltage higher than 14.7v intentionally, but my vehicles voltage regulator cannot be adjusted.

I've got ~ 200 deep Cycles over 23 months on it and a couple thousand engine starts. Last night I removed 49 of the claimed/rated 90 available AH from it, and voltage was 12.19 while still under a 0.9 amp load.

Northstar Says 50% charged rested voltage is 12.11v.

So it appears to still have not lost any capacity, as I recorded the same figures, when it was still new and I believe the 90Ah rating is conservative, but I've never done a 20 hour capacity test to 10.5v either. And will not.

It cranks and starts my engine faster than 2 group 27 marine batteries in parallel could, and appears as if it will be outlasting them even being cycled twice as deep.

Soon, I will get a flooded/wet Trojan t-1275 battery for deep cycling and return the Northstar AGM to mainly engine starting purposes/ emergency capacity duties only, but for now and the last 3.5 months it is doing both duties, and doing it well, and it appears to love high amp recharges, and I give it high amp recharges often, and I have extreme confidence in it doing both these duties.

I am interested in Why Chefwong's Odyssey AGM's are failing so prematurely. My Northstar is my First large AGM and it is performing in deep cycle service, admirably, so far at least, and I credit that with the ability to feed it at high amperage charge rates as well as achieving a true 100% recharge nearly every cycle.

It does not like slow charge rates of only 11-13 amps maximum cycle after cycle via solar only. I wish it did, but I've observed the same behavior dozens of times. Low and slow solar till amps taper to 0.5a, and voltage tanks after 5 deep cycles. Fast and hard 40 amps + va power supply or alternator to 0.5a at 14.46v and performance is restored. Fast and hard cycle after cycle until full, and performance remains good.

11 amps is not even considered low and slow by most, but with my solar 11 to 13 amps only occurs closer to noon.
 
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