Question about car battery sulfation

[GasSavers_rGS]

Is sulfation of a car battery a real problem or is it part of some sort of marketing ploy for sellers of "desulfator" devices?

[skewbe]

I don't have first hand experience with desulfering a battery, but there is plenty of info online on how to make one:
http://www.flex.com/~kalepa/lowpower.htm

[MetroMPG]

My understanding is that when used normally, 12v starting/accessory batteries don't suffer from sulfation (compared to a similarly constructed battery that is discharged deeply) because full charge is pretty much always maintained by the alternator.

Sulfation occurs when a battery is left partially discharged for a long period of time.

Yup:

Sulfation refers to the process whereby a lead-acid battery (such as a car battery) loses its ability to hold a charge after it is kept in a discharged state too long due to the crystallization of lead sulfate. [source: http://en.wikipedia.org/wiki/Sulfation ]

I have pretty much ruined my car's 2 year old starting battery from just over a year of regularly running it down without the alternator. (In fact if it wasn't supported by the 2 floodies I'm now carrying, I would have had to replace it already).

EDIT: sulfation is more of a problem for EV's, since the pack may go days (or weeks, in my case) between "full" and needing a recharge. The guy who donated his used floodies to project ForkenSwift runs desulfators on each battery in his Ford Ranger EV (and will also admit he hasn't done any controlled testing to say whether they prolong batt life).

[GasSavers_rGS]

Originally Posted by MetroMPG

My understanding is that when used normally, 12v starting/accessory batteries don't suffer from sulfation (compared to a similarly constructed battery that is discharged deeply) because full charge is pretty much always maintained by the alternator.

Sulfation occurs when a battery is left partially discharged for a long period of time.

Yup:

I have pretty much ruined my car's 2 year old starting battery from just over a year of regularly running it down without the alternator. (In fact if it wasn't supported by the 2 floodies I'm now carrying, I would have had to replace it already).

EDIT: sulfation is more of a problem for EV's, since the pack may go days (or weeks, in my case) between "full" and needing a recharge. The guy who donated his used floodies to project ForkenSwift runs desulfators on each battery in his Ford Ranger EV (and will also admit he hasn't done any controlled testing to say whether they prolong batt life).

MetroMPG,

Thank you for your reply.

My question about sulfation is if it's true that sulfation is accelerated when the car battery is exposed to high temperatures such as the fact that it's in the engine compartment of the car as well as very hot external atmospheric temperatures?

[MetroMPG]

My (not at all solid) understanding is that lead plate corrosion is more of a problem with high temperatures. Though I suspect a partially discharged battery will sulfate faster in warmer temps as well.

One of the reasons the US military is so interested in improved battery tech is because PBa doesn't hold up well in hot temps (ie. Iraq). As this US military Iraq battery dump attests:

[brucepick]

yikes.

[MetroMPG]

Yeah, no kidding.

And knowing that mil-spec is somewhat (slightly?) different from ForkenSwift-spec, I bet there are more than a couple of batts in that pile that would work quite nicely for my purposes...

[trebuchet03]

Originally Posted by rGS

Is sulfation of a car battery a real problem or is it part of some sort of marketing ploy for sellers of "desulfator" devices?

I'll attest that desulfation actually does work as I've seen it work first hand. An otherwise "bad" battery was brought back to life in about 24 hours and continued to show improvement over a week of use/pulse charging (desulfation). An easy (but not always accurate) way to tell if a battery is sulfated is to run your hand across the side and see if the cells are bulging. If they are, you likely have a sulfated battery.

But like Metro posted, it's not a big problem as you're not cycling the battery and then leaving it undercharged.

My question about sulfation is if it's true that sulfation is accelerated when the car battery is exposed to high temperatures such as the fact that it's in the engine compartment of the car as well as very hot external atmospheric temperatures?

After saying everything I said above... I too wonder if the charging voltage is high enough. At a higher temperature, the surface voltage (and voltage required to fully charge) increases. So I wonder if any of us are, in fact, charging at voltage too low causing the battery to never fully charge on longer runs where heat soak sets in...

[MetroMPG]

Originally Posted by trebuchet03

I'll attest that desulfation actually does work as I've seen it work first hand. An otherwise "bad" battery was brought back to life in about 24 hours and continued to show improvement over a week of use/pulse charging (desulfation).

Would it have "come back" with conventional charging & discharge cycles? What was the control?

[trebuchet03]

Originally Posted by MetroMPG

Would it have "come back" with conventional charging & discharge cycles? What was the control?

The first thing tried was charging and discharging... The battery was abused to the point that it wouldn't take a charge at all (well, perhaps a few mAh ).

After that didn't work, the desulfator was put on and after 1 charge cycle (which took a day), what was once a dead battery was a viable battery that was no longer puckered up from sulfation.

So there wasn't so much of a control as there was a try things until you find something that works attitude (as is/was the ethos of that community).

Perhaps it's worth noting that the batteries is and were used for an electric wheelchair - a likely candidate for battery abuse