SLA Sulfation: How Fast Does It Really Happen?
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.
I don't know the answer, but I think it is a good rule of thumb is to always charge right after riding if possible. If you can charge at work, why wouldn't you? If you can't the question is moot.
I probably could charge at work, but it would be a fairly major hassle. I'm trying to figure out if it would be worth it. Also if the SLA's can't handle up to 12 hours without being charged, it may make more sense for me to switch battery types.
I have had no problem not charging SLAs for well over 12 houes. (Sometimes days)
I run the Odyssey dry cell batteries in all of the street and race bikes. We have gotten back from a race and forgotten to recharge them for several days. No issues at all.
Make sure you are using a three stage charger. It will keep them happy for a longer time.
Thanks Ed. That's the primary feedback that I was hoping to hear. I'd like to stick with the much cheaper SLA's, at least for now. I have about 55 or so discharge/charge cycles on mine now, and they still seem to be pretty strong. Had a problem with the V.I.P. battery for a while, but it seems to be working OK now.
My question is "What is your DOD when you get to work?" If the batteries are only 15% discharged, waiting 12 hours won't make any difference, and would reduce the absolute number of charge cycles you are putting the battery through.
If it takes 45% of your battery capacity to get to work, the batteries will be just about flat when you get home. That will leave you with a saggy, low voltage pack on the way home, and magnify the chances of sulfation, as well as pack imbalance.
Charging at work is easy for me, and I enjoy the zoom of the topped-up pack.
I have built and drove EV's for a number of years. I found Gel Cell batteries seem to last a long time if allowed to get up to 2.3 v/c and stay there. Also if discharged to 50 percent or less they can remain balanced real good. I had BC-202 eight volters in my S-10 and all batteries remained 9.1 volt plus or minus 0.05 volts for many years and I got then well used on American Tour de Sol from Olaf Blec of MIT. My Yuasa batteries in 2003 TANK and made in China scooter converted to 60 volts did the same. I left them to be discharged during the day and charged them at night to full 2.3 v/c and got consistent range. Sometimes I forgot to charge my inverter battery pack and saw massive sulfation and my Schumacher charger went into desulfate mode with fast blinking LED.
I think it takes week or days but month of dead batteries or dead cells might be considered DEAD dead. After a winter of Trojan T-125 not being charged they are ruined. But that is a golf cart flooded type of battery and not meant to be sitting around doing nothing but leaking electrons here and there.
Still like others are saying here, if possible - charge after each use. Most made in China scooter chargers are well regulated and can be left hooked up 24/7. I leave mine on all the time except when driving. Perfectly balance too. All batteries are 13.1 volt sitting for hours. After charge they can hold 13.4 to 13.5 for a few minutes.
It seems to me that self-discharge varies by the quality of the SLA battery. My original Wilderness Energy batteries seem to hold up better than the V.I.P. battery (cheap) that I bought on ebay. If I go a couple of weeks without riding (fully charging the batteries at the last ride), the range will be no more than 2/3 of the range if I ride and recharge the day before. The V.I.P. battery seems to have a faster self-discharge rate. I checked voltages after a sluggish final stretch a few months ago: the WE batteries were at 12.0v, and the V.I.P. battery was at 11.5 or 11.6v. The problem with respect to sulfation is that as the battery self-discharges, sulfation increases.