Leaving Batteries Uncharged?

What you have read is true but it really refers to leaving them in a partial charge more often than not. Yes there will be some very very very small amount of degradation while you watch the movie but it will be so small that when you get home and charge the battery pack the charge process will repair most of it. The problem is plate sulfurication. Sulfurication will build up over a long period of time and may be dealt with by using a charger that has a desulfurication mode. Charging the batteries at the end of each and every ride will minimize this problem so the degradation will be so minor it isn't worth worrying about until you start to see a drop in battery performance then you can use the charger with the desulfurication mode and get back most of the batteries performance.

Grandpa Chas S.

Hi all, Can anyone tell me more about a, "charger with desulfurication mode". Also, where can I get one for SLA 36v?

http://www.soneil.com/ -- 'cept it's spelled: De-sulfation of battery

You can find their fine products at EV parts sellers around the world as well as other places...

And there are many places to get 36v SLA chargers.. http://www.7gen.com/website-categories/electric-vehicle-parts

I think Chas has been listening to george dub too long!

Maybe he can do some stand in for the Frank tv impersonator guy.. :D

Sorry I guess the farmer in me is showing, the word sulfurication really deals with sulfur in soil not batteries. I really meant the build up of sulfur on the battery plates.

Grandpa Chas S.

Found this online:

A high battery state-of-charge (SOC) is important for battery health and for maintaining the reserve storage capacity so critical for solar system reliability. An FSEC Test Report (reference 6) noted that "the life of a lead-acid battery is proportional to the average state-of-charge," and that a battery maintained above 90% SOC "can provide two or three times more charge/discharge cycles than a battery allowed to reach 50% SOC before recharging."

http://www.solarhome.ru/control/why_pwm_chargers.htm?print=1

Another academic report (on AGM batteries) I saw confirmed this, and even noted that the battery lasts longer if a 10% depth of discharge occurs before recharge vs a 5% DOD, but past 10% charge/discharge cycle ability diminishes rather linearly. The report didn't state the duration between charges however.

After getting used to the price of Lifpo4, I find worrying about a set of SLA's for a bike less worth bothering about. As long as you are not discharging past 80% and leaving them for days, don't sweat it like it's life or death.

Say you ride to the movies or work on flat ground and use 30% of your battery. When you get home to a charger, you still have only used 60% of capacity, and are still charging within 12 hours. Don't worry. You aren't riding the batts that hard.

Say you ride to work, using 60%, riding back home you run out of power, and after milking the very last bit of power out of the batteries, don't bother to charge since you won't be riding tomorrow. Do worry, this type of use will kill the batteries.

Sure it's ideal to go easy on the batteries. Especially if it is a larger EV and a pack costs over $150. But don't lose sleep over a 10% shorter lifespan. The key thing is to keep it below 80% discharge during the day and charge at night. If your daily ride is taking the batteries past 80% routinely, start saving for lifepo4 because you just need more range anyway.

I am not sure about the following statement (which I made up), could others please comment:

"During recharging of SLA batteries no additional sulphation occurs, even if it is a VERY slow recharge"

If that is true, then a solar panel on the EV would still not add appreciable range in the short run, but a significant amount of extra battery life expectancy over it's useful life span.

Mr. Mik

↑ I actually was wondering the same thing a while ago. I thought about getting a tiny lithium pack and having it very slowly trickle charge the SLA pack. I never did anything with the idea, though, since I killed my batteries a short while later.

That is an interesting idea. I still think the crystals won't be that hard by nightfall and won't be so big if the discharge is less than 50% while the ev sits. But for those with larger ev's the cost of new batteries makes it worth doing anything that might help. Another thing I've wondered about is some type of device that would quickly blast off crystals that could be used on an opportunity charge outlet. Something that would only need about 15 minuites of plug in time would be easy to do while making a purchase in a store while parked by the ice machine. Finding a place for a proper charge can be hard, but if you could just get rid of some crystals quick it would help battery life and be easy to sneak.

Dogman,

You mean something like this? http://home.comcast.net/~ddenhardt201263/desulfator/desulf.htm

Yup. Apparently they do work. The soneil chargers mostly have it built in, as do many other brands of quality chargers. The cheap scooter chargers usually don't. But if you can just recharge right away, it is not even needed. The pulse is needed when the crystals are harder, and in my opinion, if you can just not leave it uncharged overnight, that is good enough. At first the crystals are soft, and regular chargers dissolve em. Even when best cared for, they are only going about 250 complete discharges. But they can go a lot more if never completely discharged in the first place, possibly a thousand, if never below 50 or 60%. So the real way to care for sla's is to not run them dead all the time.

I'm soon going to 48v, so may have a 36v Soneil charger for sale (I think, may keep in case I decide to go back to 36v). If I understand the Soneil website correctly (don't know much about things electrical yet), the desulfation mode only operates under deep discharge conditions, and the LED blinks when in that mode. I ride my BD36 4 miles to work, let it sit all day (sometimes 12 hour days), then ride home and connect the charger. I've never seen the charger blink.