After 7 seasons with my old Group 27 battery I just recently got replaced it with a Group 31 AGM battery. I've charged it for the first time today after a weekend without shorepower.
I've read quite a bit about the need to charge AGM's at no more than 14.6 volts - and the dire warnings about your batteries early demise if you choose to ignore this limit.
My charger, picked up a couple of years ago, calls itself an "intelligent charger" - variable voltage, 30 - 10 amps. It has charge settings for regular, deep cycle and AGM/Gel batteries. It has served me well and I have had no complaints.
However - I was surprised at the voltage fluctuations today - somehow - because it was on its AGM setting I didn't expect to see it go above 14.6 volts.
The battery was at 12.3 volts when I started charging.
For the first 1 1/2 hour or so of its cycle it fluctuated from 13.0 volts to 15.0 volts. For the next approximately an hour it fluctuated as high as 16.8 volts. The high voltage fluctuations are quick - not much more than a minute or so then back down to a lower voltage for a much longer period of time. It is now finishing off at 11.6 volts.
So I guess I'm confused.
Is the charger operating correctly for an AGM battery?? - or should I be looking at another one - and if so - any suggestions as to brand name and model??
Thanks,
Jay
2002 Bambi 19' - the "Toaster"
2003 Nissan Pathfinder - the "Buggy"
I would recommend a new charger. Xantrex makes quality marine chargers with AGM and Gel settings. They can also be temperature compensated. Given the price of quality batteries, it pays to use a quality charger. Those voltages are way too high. Also will reduce life of other 12 volt components in your RV. Casey
What does your converter manufacturer have to say about the short duration higher-voltage readings? 16.8 VDC is WAY too high, irrespective of what battery technology you have. Wonder how your refrigerator PC board would like that spike???
Well... Let me make some guesses.. You were not measuring voltage at the battery but at some other point, perhaps the converter output.. And each time the voltage went DOWN, it was a bit higher than the last time.. (Kind of like a bumper jack)
Am I right? If so read on.. If not. Well optionally tell me, but stop reading now.
The unit would go into boost mode (15 volts out) to push amp-hours into the battery, then it drops to "Check" mode, measures the battery voltage after a short period of time and goes back into "Boost" mode to push in more amps
It continues to do this till it sees the voltage approaching the 14.x set point when it checks.. then it switches to "Absorption" mode where it holds the 14.x volts and monitors current.
This is a true 3-stage charger
Most 3-stage chargers are really 2-stage with boost and absorption both the same voltage, Only in "Bulk" or "Boost" mode they limit current and in "Absorption" mode the limit voltage and monitor current.
Nothin adds excitment like something that is none of your business John is Near Kenwood TS-2000 housed in a 2005 Damon Intruder 377
When it comes to gel batteries the correct way to charge them is no more than 2 amps and it can go up to 48 hours to get it correctly charged. If you have any questions, pm me. We do this everyday for a living.
Alan
Alan, Brenda, Kyle
Queen Creek, AZ
2007 F-250 XLT Supercrew V-10,w/tow command,4.30,Equalizer hitch, WD bars
2008 Jayco 26BHS
bkbajb wrote: When it comes to gel batteries the correct way to charge them is no more than 2 amps and it can go up to 48 hours to get it correctly charged. If you have any questions, pm me. We do this everyday for a living.
Alan
OP's question was about AGM batteries, not gel.
The voltages are too high. Here is a report by C&D Technologies, an AGM manufacturer, on why those voltages are bad. I'm using a Progressive Dynamics converter with excellent results charging my AGMs, but there are stand-alone chargers too.
What battery is it? What charger is it?
I agree with the above recommendation of a Xantrex battery charger. Xantrex Truecharge 40 or an XADC40 would solve your trouble.
2001 F150 SuperCrew 5.4 Lariat Offroad 4x4 Tow Package 4.10 Truetrac
2006 Keystone Springdale 249FWBHLS
12K SuperGlide, KGE3000Ti 2.3kw rated 2.6kw max
Frank's voltage booster, Prosine 1800 powered by 4 GC2 batteries
Thanks for the responses - looks like I am in the market for a new charger.
For some clarification to wa8yxm - the voltage output of the charger is taken from a digital display on the charger itself - but I think you are right - the longer, lower voltage readings at the bottom of the cycle did seem to be higher as time went on - but I think that this would have to be confirmed through a little more diligent monitoring than what I did today.
bkbajb wrote: When it comes to gel batteries the correct way to charge them is no more than 2 amps and it can go up to 48 hours to get it correctly charged. If you have any questions, pm me. We do this everyday for a living.
Alan
LIke so much with batteries this is wrong.
The amprage depends on the size of the battery, for example a 100 amp hour gel cell can be safely charged at 20 amps
of course an AGM of that size can take 30
Which leads people to brag about how much faster you can charge AGM's
Of course...... Flooded wet cells also take 30 amps
NOTE without checking I'm not sure if the gel cel rate is 20 or 25%
Note 2: Source: Xantrex, manual for the prosine 2.0
LIFELINE RV BATTERY BENEFITS
User Safe
sealed construction
non-spillable
install in any position if properly supported.
submersible without damage
Maintenance free (no adding water or repairing corroded terminals) Fastest recharge. (no current limitations with voltage regulated recharging)
Deep Cycle (thick positive plates to provide real deep cycle performance)
Outstanding cranking performance (aircraft cell construction lowers internal resistance)
Best charge retention (especially against flooded cell types)
Lowest discharge rates (Less that 3 percent per month unattended)
Easily shipped (even via UPS except GPL-8D and GPLAD because of weight)
Shock and vibration resistant. (100% of plates are covered with separator liners)
Properly supported, LIFELINE AGM batteries with absorbed electrolyte can be installed and operated on their side. END OF QUOTE.
Because of lower internal resistance, AGM batteries CAN be charged faster than wet-cell batteries. Said another way, more of the charging current is stored in the AGM battery, less is turned into heat.
We have been using their batteries in our boats and RV's for decades. Though initial cost is high, we have found their benefits payoff in the long run.
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