Dead battery

[sumo]

It's my fault, I left the ignition ON overnight. I don't know why or how but there you have it.

No big deal I'll just recharge it with my Battery Tender Jr, should be fully charged by tomorrow noon.



Nope. BTJ light still solid red and bike still dead.



Checked voltage, 8 volts.



I pulled the battery and hooked up a real charger, it's only accepting 0.5 amps normally it shows 4 or 5 amps while charging. Not looking good.

Update: I went out for a couple hours and now it's charging at near 6 amps. Things are looking up.

 

[670cc]

The BT junior does not work below a certain start voltage.

The maximum charge amps is usually listed on the battery. An 11 amp hour battery typically has a suggested charge rate of 1.1 amps (1/10 AH rating). A think fast charge rate of 2.2 amps (1/5 AH rating) is the maximum, but I may be wrong. You might want to check the label.

Once you've gotten the battery "woke up" with the big charger, you might want to go back to the slower BT Jr. charge rate.

 

[Hank]

I agree with 670cc. I don't understand the physics, but batteries that are completely dead seem to often require some kind of shock to get them back up to a certain level before you can slow charge them. You can often find supposedly dead batteries for sale and all they need is a series of small charges to sort of trick them.

 

[dduelin]

I seem to recall from my boat owner days that AGM batteries like a bulk charge current of 10% to 25% of the battery's Ah rating. In our case about 1.1 amps to 2.75 amps.

If a battery is too discharged to allow a charger to kick in you can connect it in parallel to a good battery and connect the charger to one or the other and charge them together.

 

[sumo]

Thanks for the info. I've put the battery back in the bike and it is alive. I did not start it and have put it back on the Battery Tender which is solid red meaning it is charging and it thinks the battery has less than 80% charge. It should change to blinking green (meaning better than 80% charge) finally it should go solid green when fully charged. Lets see. Thanks again.

 

[dduelin]

Thanks for the info. I've put the battery back in the bike and it is alive. I did not start it and have put it back on the Battery Tender which is solid red meaning it is charging and it thinks the battery has less than 80% charge. It should change to blinking green (meaning better than 80% charge) finally it should go solid green when fully charged. Lets see. Thanks again.

Again, If I recall correctly the BT's do all you describe but they also have a 8 hour charge limitation. If the battery does not achieve 80% of charge in 8 hours the timed cycle algorithm kicks in and the charger goes into float mode which will not bring up the last 20%. It should still be fine though even at 80% of charge. Charging banks of boat batteries I was always happy to get 80% and shut off because it takes a very long time to bring up the last 20%.

 

[sumo]

The BT junior does not work below a certain start voltage.

The maximum charge amps is usually listed on the battery. An 11 amp hour battery typically has a suggested charge rate of 1.1 amps (1/10 AH rating). A think fast charge rate of 2.2 amps (1/5 AH rating) is the maximum, but I may be wrong. You might want to check the label.

Once you've gotten the battery "woke up" with the big charger, you might want to go back to the slower BT Jr. charge rate.

So according to the battery 5.5 AMPS in Quick mode 1.1 AMPS standard. It's interesting how my charger went to 'near 6 AMPS' it figured out the 5.5 all by itself. It does say right on it that it is a 'Fully Automatic Charger'. Looks like I lucked out when I bought it back in 1996.

The BT Junior puts out 0.75 AMPS which is under 1.1 AMPS and in my mind should be fine.

UPDATE: BT Junior is Flashing Green.

 

[ste7ios]

To recover a heavy sulfate battery they usually do a charge with very high voltage and very small current (some mA) to break some sulfation crystals, and start accepting some current. Because that may produce gases (and dry it) it's usually not recommended for VRLA batteries...

In general the most recommended way to charge a lead acid battery is a charge rate of C/10 as already noted. Higher than that may also cause gasing...

To have an idea about charging: Charging Information For Lead Acid Batteries – Battery University

Note that many chargers are not so accurate and may overcharge a battery. As I know Schumacher is one of them... Keep an eye on him...