Hi John,

It just goes to show how different "science" and "reality" can be. I have also lost batteries when left on trickle charge over winter before, although not in recent memory. There can be a whole variety of reasons for these failures and obviously, without knowing specifics of each case, it is hard to know what may have been the reasons for failure. Admittedly, if you know of a number of people that have left their batteries on charge continuously all winter and they failed very quickly in all cases, it would certainly give rise to a belief that the continuous charging was at fault.

I'm going to try to provide you with some more help here and you can decide what works best for you :o)

First of all this may be quite long, so those of you that think you are okay on battery theory and practice may want to lurk elsewhere!

I guess I should point out that (hopefully) I have some expertise in this area because I designed battery charging systems and power supplies for nine years ( And...no, I didn't work for Deltran! ;o) ) Although I don't necessarily have all the answers, I'm more than happy to put my experience to some use.

Maybe I should explain the battery types, because there are so many popular misconceptions and I'm even guilty of promoting a few myself!

We're talkin' lead-acid cells only.....technically divided into five types (five!!! I hear you say), they are all variants along the same basic idea, they are ...... Flooded, Sealed, VRLA, AGM and Gel. A flooded battery is your traditional wet lead-acid cell with lead plates and sulphuric acid, topped up with distilled water when the fluid levels drop; a sealed battery is generally a flooded battery except its sealed from the user and contains a sufficient amount of acid to sustain a chemical reaction for a defined lifetime (usually 3 to 5 years); a VRLA is a Valve Regulated Lead Acid Battery, it is sealed but it has a valve which permits the safe release of gases created during charging; an AGM cell (stands for Absorbed Glass Matte) is actually another sealed VRLA and is often thought of as a Gel cell, technically its not and is really a wet cell but its sulphuric acid is suspended in the fibrous mat and the characteristics are similar to a Gel cell so in my book it can be called a sealed VRLA or Gel cell and it doesn't really matter!; a Gel cell has silica (mostly) added to the sulphuric acid and this forms a gel like electrolyte, the cell is also sealed and generally valve regulated.

Corn-fused now? You will be! ;o)

For the next bit lets simplify those groupings into three if we can.... Flooded, Sealed Wet (this is what most people refer to as "Maintenance Free"), Sealed Gel (this is what most people mistakenly refer to as "Dry").Flooded types are the least sensitive to charging levels provided you top them up with distilled water periodically. Sealed wet cells are more sensitive to charge and generally have a maximum life of five years if treated well. Sealed gel cells are very sensitive to charge levels (particularly over-voltage) and experience shows they mostly start to degrade badly after three years although they can last for five years in some environments, Gel cells are best suited to "standby" applications.

Its worth pointing out that the biggest advantage of the Gel cell is that it is smaller and lighter than other types. Of course it is also "maintenance free".

Now here we come to the important stuff: The type of battery starting to be fitted in most modern motorcycles is the AGM battery. It is small, light and maintenance free, it is valve regulated and the sulphuric acid is suspended in a media, it is non-spillable. Most people are referring to this as a Gel cell and that's okay, technically its not but we don't need to split hairs. An AGM battery likes to see an absorption voltage in the range of 14.4 to 15.0 volts and the float voltage should be between 13.2 to 13.8 volts. A true Gel cell likes an absorption voltage range of 14.0 to 14.2 volts and a float voltage of 13.2 to 13.4 volts. As you can see the tolerances on the Gel cell are lower than the AGM but a float voltage of 13.2 to 13.4 is good for either type.

If you are using a "battery tender" or other similar charger with bulk, absorption and float modes you should be able to switch the charger on and just leave it. If there is something wrong with the battery or the charger then you could have a problem, but assuming everything is okay you can leave the charger on float permanently over winter and just let the battery maintain a full charge. Bear in mind that once the cell reaches full charge it will be putting out the same voltage as the constant voltage float charger, therefore no current will flow and so the battery cannot be overcharged.

So why do people have problems?? Well, in my case the batteries I "lost" over winter were all flooded types and in every case it was because I didn't maintain the fluid levels adequately whilst leaving them on charge...in my defense, when you have fourteen motorcycles and three cars in your garage it can be difficult to keep up on the maintenance :o>I've never had a problem with an AGM or Gel cell hooked up permanently to a constant voltage charger operating at 13.2 volts all winter long.

So what do the ST bikes have? They appear to have valve regulated AGM cells and they can be float charged continuously at 13.4 volts (my personal ideal setting for this battery). Again, a battery tender or similar charger will do the job perfectly.

Now what about the concern that you have lost many batteries by leaving them hooked up to the battery tender? First of all I would have the charger checked to make sure it is working properly. Next, if your other batteries were of the flooded type, you may have experienced a problem where the lead sulfates that occur during natural battery discharge did not recombine properly with the water during recharge, either the fluid levels became too low or the water that was added was impure. Excessive gassing can start to occur if the float voltage remains too high (above 13.8 V)and so large fluid loss can occur quite quickly if the charger is not adjusted properly.

Again, with an AGM or true Gel cell there is no reason why leaving a charger on float all winter at 13.2 to 13.4 volts would cause an early failure of the battery.

Having said all of this, there is no reason why you cannot continue to charge your batteries by periodically plugging in the charger and providing them with a boost voltage. Just be careful not to let them discharge too much, because any cycling of any lead-acid battery promotes advanced aging of the cells.

Incidentally, I would think that, in the case of the ST series battery, it would probably have an average lifetime of three years, mainly because it is a fairly small battery and it has to cope with significant loads under starting conditions. If you get four years out of it I will be impressed!

Sorry if all of this has left you more corn-fused....honestly, I was only trying to help <:o}

Ray C

'01 ST2

--- In st2_owners@y..., "John Swiatek" <ironjohn4@h...> wrote:> Hello Ray C,> > Thanks for the battery explanation. I have lost two relatively new traditional lead acid (non-Gel type) batteries that have been left connected to Battery Tenders all winter. I am not alone, a friend lost a battery that was also left connected to Battery Tender last winter. Come spring the batteries exhibited the same mode of failure; adequate terminal voltage but an inability to deliver current. At the time I was told this failure resembled that of a battery which sulfated (plates shorted). Is that true?> > Since your post I did a little more research and found that sulfation occurs when the battery has been left for a considerable time in a discharged condition, not from an overcharged condition, or sulfur settling process like I thought. Admittedly my opinions have been based largely on personal observation, not science.> > You mention to LEAVE the GEL cell connected to a trickle charger (50-100mA). What about a traditional lead acid? Is there a difference?> > As I understand a Battery Tender, it should switch to a trickle charger after performing the bulk and absorption charge stages. So I would expect to be able to connect a Battery Tender and leave it all winter, experience has proved otherwise. Since I have started only periodically plugging in the charger I have not lost a battery yet.> > So I still cannot explain why myself & others loose perfectly good batteries by leaving them connected to a Battery Tender. I'm corn-fused, please help if you can.> > John