SLA Sulfation Process: How Fast Does It Really Happen?

[Richard145]

Does anyone know how fast the sulfation process actually happens in SLA batteries? I suspect that at least a slight amount would happen with every discharge. I've seen some articles say that in an even partially discharged state, sulfation would begin to be a problem within a few days. I've seen other articles say that in a discharged state, sulfation would be severe in six months. My question mostly has to do with my riding 4 miles to work, letting the batteries sit for anywhere from 9 to 12 hours, and charging when I get home at the end of the day. How much sulfation happens in a few hours? ... 12 hours? ... 2 days? How much more life might I get from the batteries if I charged at work? 10%? 20%? Does anyone know of any articles in which such questions have been answered with specific measurements? My original WE BD36 batteries are about 14 months old, discharge/charge cycles in the low 50's, and still seem to be in good shape. The newer V.I.P. battery, maybe not so good (see posting re: V.I.P. batteries on eBay). I'd appreciate any feedback.

 

[fechter]

My experience is it's not a big problem as long as the battery is not completely discharged. If the battery is really low, then it can be ruined in about 24 hours in some cases. If the battery is half discharged, it takes longer, but every cycle adds up. Sulfation is not the only cause of battery death. Separators can fail as well as internal connections.

To answer your question, I think you'll be fine if you wait until the end of the day to charge as long as the battery isn't discharged too deeply. Charging at work will help, but I can't say how much.

 

[RTLSHIP]

I've read that sulfation occurs even when battery is "fully" charged because the SLA battery is never 100% charged.
I have a Tecmate 12volt Charger/ Desulphator. Can't say for sure that it works, but I use it anyhow.
What I can't figure is why my thumb throttle yellow light comes on at 37 volts for 1 pack and comes on at 36 volts for another etc.
Many sources claim that 300+ cycles are possible with SLA batteries provided that the battery is not taken close to its nominal voltage and properly charged etc.
For the most part, I don't go below 36.5 v on my 36 v pack. The main exception is my 36 v Silicone Greensaver pack which can be taken down to around 35v without damaging it. This Silicone technology has some promise in that it is deep discharge
friendlier than regular SLA. Of course, Greensaver batteries have to be recharged the same day like SLA. They are not as prone to sulphation.

 

[Richard145]

Because of some increased concerns about battery longevity recently, I've been using a little more leg muscle and less throttle. Earlier this week, the voltage of my 48v pack was 49.6 when I got home at the end of the day (8 miles round trip). I connect the charger through a wattage meter, and the charge has been taking about .3 kW hours. It appears that I'm generally not using more than about 60% of the charge for the round trip, so I hope that this helps to extend the life of the batteries.

 

[RTLSHIP]

I have 4 36v 12 ah SLA packs(1 is silicone) and a 48/15 lifepo4. I sort of try to rotate them. They get evenly used.
Also, they get topped off by charger once per week. In the warmer months, SLA will self discharge at a faster rate than in cooler months. Ideally, they should be kept inside with air conditioning.

 

[Old_Scoot]

RTLSHIP.

I'm curious about your Silicone Batteries. It sounds like you've had good luck with them. Would you recommend them in place of conventional SLAs? Do you charge them the same way as your standard SLA packs? I seem to remember reading something about them requiring different charge voltages with different ambient temperatures.

 

[torker]

I have 4 36v 12 ah SLA packs(1 is silicone) and a 48/15 lifepo4. I sort of try to rotate them. They get evenly used.
Also, they get topped off by charger once per week. In the warmer months, SLA will self discharge at a faster rate than in cooler months. Ideally, they should be kept inside with air conditioning.

I am also interested in the greensaver batts. Can you tell if you get any more range out of them compared to generic sla of the same ah? I like that they have a lot less internal resistance. My sla are really made for standby use so I hope I can gain some range using something made for higher amp draw.

 

[RTLSHIP]

torker, you can use them in place of regular SLA. But the weight will be a little more. For $139.(shipping included), I bought 3 new greensaver batts 12 v & 12ah each. The total weight is alomst 30lbs, but these batts behave almost like they are 12v 14 or 16 ah SLA. You have to buy all 3 from the same batch and should not mix them with other batts.
Right now, I have so many different battery packs that most of these packs remain relatively new.
My oldest pack of regular SLA is almost dead. It came used along with my ebike in July 2008. After 1.5 miles, the pack is down to 36v.
How long can SLA last? I'm not sure, but I'm under the impression that they will go for a long time if you: 1) do not deep discharge;2) recharge at every opportunity (bring charger with you as much as possible).
The Silicone Greensavers are suppose to be good for 400 full cycles. Most of my cycles, however are going to be partial.
So I'm guessing maybe 1200 uses. The vendor told me that going w 35v is completely safe. Also, sulfation is generally less of a problem with Silicone. Regular SLA chargers are all that's needed.
For regular SLA I would guess 200 to 300 full cycles. If used reasonably, maybe 1000 partial cycles.
I've read that you get more out nearly all batteries by doing partial cycles. The main exception to that is maybe Nickel cadium batts (memory issues).
hotter weather means SLA batts will self-discharge faster, so it's best to keep them cool indoors and to top them off with charger once a week. I do that with all my SLA packs

 

[chet]

lead acid love being fully charged at all times. Slow charging (Low amp) is desired. A battery minder or trickle charger is best for storage. If using flooded cell batteries, keep topped with distilled water. Wash down cases with baking soda water. Don't get any inside cells. Don't store on cement floors.

 

[Karolis]

2 of 5 my SLA 12Ah batterys are almost dead. I only get about 7km from them on slowly and 2km on hard riding. I went about 2000km on them. I used it from couple of weeks in autumn and started to use a lot more frequantly on late spring till now.

 

[nineball]

Over charging ,is the primary cause of sulfation, allthough sucking them dry is a factor, the cheap trickle charges, don't have HVC (high volt cutoff), they will charge over 15 v if you leave them plugged in, that over volt boils the acid, not good for long term.

The short cycle charge vs trickle charge as different ratings per battery.

You can push a fast charge to 15v and disconnect, but not a trickle that high.

14.2 - 14.7 should be max, 13.8 settled out

 

[scoot]

I have what maybe some might consider a relatively sophisticated SLA charging setup on my Goped scooter, but since I am not an electronics expert I just don't know for sure. I have a Cycle Analyst hooked up and I have observed amperage and wattage readings over time when it charges up my 24v banks (2s2P).

At first it charges at 60 W and a constantant current of 2.5 amps until it reaches 30 to 30.2 volts (hours to get there). Then I noticed the current and wattage dropping off slowly for about an hour or more until it reaches 0.01 to 0.03 amps or so and stays there briefly until finally the voltage suddenly drops to 27.5v at which time it seems to signify the "trickle" state... that's also when the stock flux capacitor light(s) indicate the trickle state.

I usually let it remain in that state for 12 or 24 hours most of the time and unplug it. If I can anticipate a ride , I sometimes plug it back in for 20 minutes or so just before the ride to top it off... seems to to give a lttle bit of brief perfomance boost when I do that... perhaps becasue it gets a full 2.5 amps at first and then drops rapidly to less tha 0.1 amps within just a few minutes.

So, does that seem like a pretty good setup for a SLA charging system? And are my charging procedures sound?

 

[dak664]

Sounds like a good charger, with that last state being a proper maintaining voltage to keep the plates fully absorbed (as opposed to trickle charging which is a continuous overcharge, harmless if water can be replaced). Your disconnecting it allows storage discharge, resulting in that brief 2 amp charge when you connect it again just before going out. You might check that it really is looking at the battery and not just giving a timed minimum charge by disconnecting briefly after a full charge and seeing what it does when reconnected. A smart charger will put out a prequalifying charge at around 0.1C and go to maintenance mode if the voltage if already high enough, which should only take a couple of seconds.

It might be better to charge at a higher rate to reduce the time spent in a discharged condition, though. It seems to me the charger ought to be sized to make a recharge in less than around 20% of the time you are away using the battery.

 

[nineball]

Yup, thats perfect..30 -.30.5 = 15v per 12v pack fast charge, and then 27.5/2 = 13.75 (or 13.8 ), for trickle, and the unplugging will somewhat balance the cells, and the quick top off works well. You should be fine with that regiment.

The other thing at this point to make them last is how far you discharge them, 1/2 would be best, more than that goes down hill, if you know you have sucked them pretty far then trickle them back the as least a 1/2 state and go from there.

But overall sla's are pretty forgiving.

 

[chet]

Yes. They do not like high amp charging, over heat and swelling cells.They do not like deep discharge, and low voltage condition.
That is why they work so well in automotive applications, they are always slow charged to capacity.

 

[RTLSHIP]

I have 2 36 v 2 ah SLA chargers and the peak voltage is around 42 or 43 volts. I've never tried a trickle charger to charge them, though I do have an Optimate desulphator which charges/desulphates each. 12v SLA battery
Do desulphators work? I'm not sure though I have used it on all my 12 v batts, including car batt. This optimate can remove soft sulfation only. I have read that severe hard sulphation occurs when the battery is deeply discharge and left in this state for extended period of time (e.g.overnight, 48 hrs etc)
Damaged SLA by charging with a higher voltage (perhaps 15 volts per a 12 v battery) is possible. Also, charging too fast
(e.g. 4 amp charger) may be harmful to a 12 ah battery. But there's a difference between sulfation and physical damage.
Also, sometimes an 18 or 19 volt zap will help revive a dying battery. The optimate desulphator claims to be able to do this
when conditions warrant.
Ideally, the desulphator should be put on a brand new battery, then about 3 or 4 times a year. It also acts as a 12 v charger. The Optimate Tecmate sort of thinks and acts accordingly.