Max charge voltage for AGM batts

[Gyro]

I'm on my second set of UB12350 AGM batteries for my motorcycle. I've been careful in how I use and maintain them, yet I only get a couple hundred miles before they start suffering serious loss of range. It has been bugging me why I've been having this problem.

Since the second set is now dying, I'm looking to replace them with LiFePO4 cells. However, I just came across something I hadn't notice before. I found a website that said that AGMs should not be charged beyond 14 volts. This seems to conflict with other places that say you can charge them like normal lead-acid batteries. My bulk 72V charger charges and holds them at ~14.7V.

So my question to those more experienced than I, could this be the cause of my problems? What is the correct charge cycle for AGM SLA batteries?

The charger I'm using is this one: http://www.cloudelectric.com/product_p/bc-hwc1b-72v-fslash-8a.htm

Thanks.

 

[slowlane]

I got UB's AGM in July from a distributor. Also got the spec sheets produced from an independant source (I think at UB's cost), FOUR sheets of graph specs (all is known). SLA AGM chemistry varies by plate alloy, they ain't pure lead. All ref is for UB brand 2010. Life cycle : 70% discharge= 100. 50%=300-400. 30%=1300 to 1400!!! LAB results @ 72'F and at LOW amps.. I switch my 36V pacs, rather than go below 50%, hoping for a one year of use, every day year round. Charge specs are printed on bats. UB-AGM are safe at 4.5A, don't know about later at half life. Hurry up I use 4A, got time 2A. SMART chargers (3 stage), ONE per bat, 6A will work on 3 bats parallel EXCEPT sensing of the final millivolt won't work, leading to overcharge however slight. My Schumacher 2-4-6A chargers from wallymart-$34CAN vary in finish charge, mostly undervoltage 14.7 to overcharge 15.2. USE the return policy to get 14.9V on the very end of charge (voltmeter watching). UB wants 15.0V finish. Relaxed voltage is mostly 13.3-13.4. Your problem may be overcharge... do you hear short wistles? They don't get warm at 4A either. Overcharge or depleting, not the batteries. Another benifit of AGM is 75% AH at 32'F verses 40-50% SLA . I'm no expert, but I took the time and got the specs and getting results. I use inline 36V cheapy on occasion, do NOT get same AH's (time and fell, not AH measured). Had a hard time with bats not too long ago. Lots of BS on bat science posted on web found ONE believable by a U prof.. EDIT add on: Call Chris at TNC scooters, if I recall correctly, he states 100 cycles in TENN. with his bat products.

 

[deardancer3]

Many years ago, i saw a note about some problems when Harley Davidson went to AGM and thought the problem was with the Hawker Batteries.

Turned out it was the City pub cruiser guys that rode around town with no significant speed or engine rpm; the Hiway cruising guys did not have a problem.

ANalysis showed ( if my memory is correct) that the low rpm guys were not getting enough voltage to charge the new AGM's; and an alternator pulley was changed to a different size to get more rpm's on the alternator for higher voltage and the problem was solved.

That was a while back, but you might check to see if you have a similar situation.

Sounds like your Battery was not getting 100% charged for some reason. Best investigate if you are considering Lithium Iron Phoshpate with BMS as they want and even higher voltage.

d

PS - there is a difference between Charge voltage and Float voltage. Float V is long term (over 12 hours an up to forever)and pretty critical to not get too high, charging voltage can be higher than Float V and not as critical until you get to 92-97% completion ,, when most charges switch to float. The Terms do not interchange.
If I remember Soneil, they went to about 29v on a 24v pack just before going to float or off.

Put a long lead DVM across the battery and check the battery voltage when charging, riding, lights on, etc. You might have a defective charging circuit, or too low or too high a charge voltage. Put a cheap wally world lead battery in til you get it fixed.

 

[Gyro]

I got UB's AGM in July from a distributor. Also got the spec sheets produced from an independant source (I think at UB's cost), FOUR sheets of graph specs (all is known).

SLA AGM chemistry varies by plate alloy, they ain't pure lead (all ref is for UB brand 2010).

Life cycle tests (LAB results @ 72'F and at LOW amps..):
- 70% discharge= 100.
- 50%=300-400.
- 30%=1300 to 1400!!!

I switch my 36V pacs, rather than go below 50%, hoping for a one year of use, every day year round.

Charge specs are printed on bats. UB-AGM are safe at 4.5A, don't know about later at half life. I use 4A, got time 2A. SMART chargers (3 stage), ONE per bat, 6A will work on 3 bats parallel EXCEPT sensing of the final millivolt won't work, leading to overcharge (however slight).

My Schumacher 2-4-6A chargers (from wallymart-$34CAN) vary in finish charge, mostly undervoltage 14.7 to overcharge 15.2. USE the return policy to get 14.9V on the very end of charge (voltmeter watching). UB wants 15.0V finish. Relaxed voltage is mostly 13.3-13.4.

Your problem may be overcharge... do you hear short wistles? They don't get warm at 4A either. Overcharge or depleting, not the batteries.

Another benifit of AGM is 75% AH at 32'F verses 40-50% SLA . I'm no expert, but I took the time and got the specs and getting results. I use inline 36V cheapy on occasion, do NOT get same AH's (time and fell, not AH measured).

Had a hard time with bats not too long ago. Lots of BS on bat science posted on web found ONE believable by a U prof..

EDIT add on: Call Chris at TNC scooters, if I recall correctly, he states 100 cycles in TENN. with his bat products.

Slowlane. I had a hard time reading your reply so I did a quick edit of the format to make it easier to read as you have some good info. If I misrepresented anything you wrote, please let me know.

One thing that jumps out at me is the relatively low life cycle at 70% DOC. My daily usage is just a little less than that. It could be that I'm simply wearing the batteries out. I'm pretty sure the batteries are not venting.

Deardancer, I'm aware of the float/charge voltage difference. I didn't mean to muddle them together. The charger is supposed to go into float mode automatically. The voltage I quoted earlier was apparently the float voltage (but I'll double check), that is what concerned me.

I have six batteries so I would have to match it with another of the same type.

 

[dogman dan]

Sounds to me like the main issue may be the way you are using them. All the sucess stories i've read about lead EV's talk about using them 50% dod. I could be wrong, but you may have a smallish pack, that has you using them at a highish c rate? That would only make things worse. Any chance you could convert to lifepo4 soon?

 

[deardancer3]

Gyro, are you using these AGM's to START a motorcycle engine, or are you using them to move the motorc cycle??

I was assuming to start.

d

 

[Gyro]

Gyro, are you using these AGM's to START a motorcycle engine, or are you using them to move the motorc cycle??

I was assuming to start.

d

I'm using them to move the motorcycle:
http://endless-sphere.com/forums/viewtopic.php?t=16836

 

[deardancer3]

Gyro, are you using these AGM's to START a motorcycle engine, or are you using them to move the motorc cycle??

I was assuming to start.

d

I'm using them to move the motorcycle:
http://endless-sphere.com/forums/viewtopic.php?t=16836

then please ignore my post about the pulley size and charging voltage; I thought you were riding a regular ICE motorycle that was having trouble with the starting battery not recharging while riding.

Sorry

D

 

[vanilla ice]

IIRC my HK charger takes them to 14.7v while my dumb starter charger holds them a tad over 15v. I have 24, 36, and 48v agm ebike chargers and they charge to lower voltages per battery. All the bats sit in the high 13's when off of the chargers. I would think the same type of thing that applies to lipos applies here.. charge to a tenth lower voltage per cell to extend life.

 

[slowlane]

I missed motorcycle, thinking ebike. UB12150 (Universal Batteries) has a one year warranty, may apply to all AGM. Short having an overnight (slow) drain or overcharge possible. Find the distributor and get a damaged battery to them, gets cut open, tells the story, warranty or abuse. Bypass the retailer.