Loss of Voltage, Battery on Charger

[cowboyup3371]

For the second time in about 3 months I seem to have lost an AGM battery while the battery was either off the bike or on the bike but on the charger. The first time, 3 months ago, the battery had been sitting off the bike for a year and put on but used twice to test the electrical system. I left it off the charger and when I tried to use it to actually start the bike, found it dropped to 7v.

I bought a new battery and it seemed to have been doing just fine until yesterday. To explain, when I returned to the garage from my New Years Day ride, I immediately connected the battery to my charger/maintainer (1.5A). I didn't check the bike over the latter part of last week or the first part of this due to the weather. As I needed to get my funnel to fix an issue with the Jeep yesterday, I stopped by the garage on the way home. As I walked by my bike, I noticed the maintainer status light was orange instead of green. I checked the battery voltage and it was down to 7v despite having been on the maintainer for a week. Assuming maybe that charger was bad, I moved it to my daughter's brand new charger. However, after 24 hours, it seems the battery has again dropped voltage to 5.6V.

The ignition switch is in the off position (key still in it) and I don't see any possible signs of electrical life on the bike. So, what causes an AGM battery to lose voltage despite having been at the proper voltage during the ride last week and on a maintainer since?

 

[tkent02]

The maintainer. Leave the battery alone, charge it a little bit evey once in a while, they last for years and years and years.

I still haven't bought any batteries for any bikes since long before you moved. They all still start right up, after sitting a month or so, every time.

 

[rkroby]

I had about the same problem with a new AGM battery. My bike was not running but I had it on the bike and would put it on the charger for 4 or 5 hours a week. After 4 months it was completely dead.

 

[koolaid_kid]

A quality battery maintainer will NOT kill your battery. Period. There is something else going on.

 

[tkent02]

A quality battery maintainer will NOT kill your battery. Period. There is something else going on.

But they do.

A mintainer is great if you need to be able to start the bike, at a moment's notice all winter, even if it needs a lot of power to start. This is not usually the case. The bike is going to sit there a long time, it doesn't need the battery sitting at 100% charge all winter.
This is not the best way to make the battery last forever. Just charge it up monthly, or better every week or two. It doesn't hurt as long as the battery stays mostly full.

I used to use them on some of the bikes, those bikes were ALWAYS the ones that needed new batteries. The ones that sat and got charged once in a while never did.
So I quit using them, and I quit buying batteries.

Not an electrical engineer, I don't know why it does what it does, but thats been my experience. I never buy batteries anymore. Haven't bought a battery in years except when I buy a bike with a dead one.

 

[koolaid_kid]

Sorry, Tom, I am. The entire function of a maintainer is to take itself out of the equation when the battery has reached a full charge. It has a sensor in that that turns itself off.
when the same sensor sees a drop below some amount below the proper voltage, it begins to charge again. The ON/OFF values are calibrated into the sensor.
If your maintainer is killing your batteries, that sensor is faulty and the maintainer should be replaced.
I understand completely how they are designed and how they work, and a correctly calibrated and functioning maintainer can no more kill a battery than an alternator can overcharge your car battery while you are driving down the road. It is electrically impossible.

 

[koolaid_kid]

I understand how you feel and I respect your experiences. Not trying to start an internet argument, either. Peace.

 

[tkent02]

I guess maybe they don't take themselves out at the right time. Not sure why, poor calibration, bad connection or something else.

But at least some of them sure do eat batteries.

 

[bluewool]

Some "maintainers" are not recommended for agm batteries. This was the case when I bought my Battery MINDer NOT Battery Tender( I do not like my Tender and use it only as a charger for new batteries). My main bike is always on the minder when I'm away because after a few weeks it often requires significant cranking even with the FI. It's had a MOTO batt for a couple of years now.
AGM's are more susceptible to over charging damage I believe. A poor storage charger may be causing the damage

 

[koolaid_kid]

Some "maintainers" are not recommended for agm batteries. This was the case when I bought my Battery MINDer NOT Battery Tender( I do not like my Tender and use it only as a charger for new batteries). My main bike is always on the minder when I'm away because after a few weeks it often requires significant cranking even with the FI. It's had a MOTO batt for a couple of years now.
AGM's are more susceptible to over charging damage I believe. A poor storage charger may be causing the damage

This is true. The label or documentation mentions that they are safe for AGM batteries. Most likely the sensor calibrations are tighter or the sensors are of higher quality.

 

[cowboyup3371]

So if I am understanding you all correctly, the possibility exists that my maintainer failed to shut itself off and therefore overcharged that battery. The maintainers I have are the Schumacher's you can buy at WalMart.

George, when you say something else is going on, is it something on the bike?

 

[koolaid_kid]

Dale, I know you take good care of your bikes, so let's think it through.
I have read that some chargers are not supposed to be used on AGM batteries. Let's take that as a fact.
Extrapolating from there, it stands to reason that some chargers are safe for AGM batteries. Why is that? I did some research today to figure it out. This is what I found:
In a way, tkent is correct. AGM batteries are more sensitive to overcharging than standard lead-acid batteries. The sensor in the AGM-approved tender must and does have tighter tolerances for these voltage limits. The tender senses the voltages in the cells. If it finds a cell below its limits, it turns on. If all the cells are at the correct limit, it shuts off. However, what if there is one cell lower than the others? It turns out that the tender will begin charging until that cell reaches the proper voltage, then shut off again. But what happens to the other cells? They get charged too, and go beyond the safe limit. This has the ability to kill your AGM battery. Therefore, if your battery has one cell weaker than the others, the tender may kill other cells, killing your battery. If all the cells are healthy, this will not occur.
So, what is the solution if you want to keep the tender connected and not have to worry about when to connect it and when to disconnect it? Put it on a timer. Let it run for say, 30 minutes a day, then shut off.

tkent, you are correct that the tender has the ability to kill the battery (if it has a weak cell, which we cannot tell by observation). I stand corrected.

 

[tkent02]

OK thanks, now I know why, but can this damage a lead acid battery as well? I have also noticed they die a lot more often on the tenders.

I was also thinking, if the maintainer lead clip didn't have a good connection to the battery terminal, it might see it as a low voltage and turn on the charger when it's not needed?

And one last thought, some maintainers don't shut completely off, but they go to a tiny trickle charge instead. Could it be this tiny current eventually damages the batteries after a long enough time?

Don't know, but I'm sticking to my charge it up once in a while routine.

 

[koolaid_kid]

OK thanks, now I know why, but can this damage a lead acid battery as well? I have also noticed they die a lot more often on the tenders.

I was also thinking, if the maintainer lead clip didn't have a good connection to the battery terminal, it might see it as a low voltage and turn on the charger when it's not needed?

And one last thought, some maintainers don't shut completely off, but they go to a tiny trickle charge instead. Could it be this tiny current eventually damages the batteries after a long enough time?

Don't know, but I'm sticking to my charge it up once in a while routine.

O.K., let's think it through, one question at a time.
I did not investigate standard lead acid batteries (remember, AGM batteries are also lead-acid batteries), only AGMs. However, if they suffer from the same issue of weak cells, and there is no reason why they do not, then yes, it could happen to them as well. And they have a much shorter lifespan for a reason, perhaps it is weak cells. IDK, once again, I did not investigate standard lead-acid batteries. I do recall, however, occasions when I brought one in to be tested and the tester person told me they had one or more dead cells.
AFA a poor connection, I saw no mention of that. Even if it had a poor connection, I would expect the very low current required to activate/deactivate the sensor would be present. Remember, a poor connection would limit current, but not voltage. So on this one, I don't think so.
AFA a tender that shuts down to a trickle, avoid those at all costs. A true tender is called automatic, in that all current output ceases. This was also mentioned in the articles I read.
There is nothing wrong with your philosophy. I merely offered a rational, science-based solution to those who wish to leave it connected and not kill the battery.

 

[Gorminrider]

Not sure if your batteries are the same, but AGM's in general...I have a couple of what I think are agm batteries from an electric lawnmower. I wouldn't use em in a motorcycle except as temporary test batteries. They have very specific charge instructions printed on them. The "float charge" is 13.5->13.8v. and you need a pretty special "maintainer".
here's more from http://www.firststartbatteries.com.au/faq.html

Charging your AGM battery

Float or Stand By

This charging method is used for back-up applications. The battery is continuously on charge and consequently the recommended voltages are slightly lower than cyclic charging so as not to damage the battery. Float voltage for these batteries are about 2.25-2.3 volts/cell or 13.2-13.7 volts. These figures may vary.​

Cyclic​

Cyclic charging is used in applications where the battery is repeatedly discharged then charged. A higher charging voltage is used but should only be done from an alternator or a 2 or 3 stage automatic charger. NEVER leave your AGM battery on charge indefinitely since it will overcharge and destroy the battery. The voltage is about 2.4-2.5 volts/ cell, or up to 14.7 volts. However you will get longer service life if you use 14.1 – 14.2 volts.​

So, you need a pretty special maintainer.

...that last bit (14.1-14.2v) pretty much rules em out for my bike's regulator set-voltage at 14.8v

 

[cowboyup3371]

Thank you Tom, George, and others. I already pulled my daughter's battery off of the maintainer and will probably use hers until the summer (She's not riding now until then due to her grades, but that's another matter). I remembered seeing a comment about the type of maintainer to use when I bought my first motobatt last year but I foolishly believed they were the same. I'm going to make a better effort to re-read the article and then pick up the correct one before going too much further.

Scott

 

[tkent02]

The one you have is fine, just don't leave it hooked up.
Use it like a charger, not like a maintainer.
A few hours every week or so is fine.

 

[Dogma]

Regarding the use of a battery tender in Ohio, I would say not to bother. My AGM has always survived the winter well, and only rarely needs help starting the bike in the spring. Either a jump from a car (not-running, of course) or an evening on the charger in anticipation of a ride was plenty. One of mine has seen some abuse too. The battery presently in my 850 has been in continuous service since 2008 at the latest. It's been dead flat a couple times (in the 1000G at RRR) and overcharged by a non-regulating R/R (getting Brett's 700 ES home from BC (The Year of the Cro-Magnon)). I have no doubt I could take the 850 out for a ride today.

Hang on, that's a good idea.