Since the Rushmore bikes come with an AGM battery, why does both the owners manual and the Harley service manual say that a 12.7 volt reading is a 100% fully charged battery?

I've left my stock AGM battery (even when the bike was new) on a battery tender till it gave the green light, and after letting it sit a few hours off the tender, never read 12.9 volts like the article says it should read.

So who do we believe?

 

As mentioned, the volt numbers alone is not the whole story. It is just one point of reference.
For example, with a brand new vehicle with a brand new battery, let it sit outside in the winter for at least a week. What kind of voltage would you expect to be "Normally acceptable" in this incidence with a good digital meter at the battery?
No, most people don't concern themselves with that. They put the key in the switch, the engine spins over and starts just fine. How strong the battery amps handle the load is a key also, not just numbers on a volt meter.
To be honest, I have never accepted that a 12.2 volt battery is half dead. The folks that push that the most - they sell batteries, don't they?

 

I hope you carry jumper cables. The numbers dont lie. http://www.marxrv.com/12volt/12volt.htm

 

Don't use this STD-FLOODED LEAD ACID.

Use this AGM-GEL and all you need to know.
12.8 = full charged
12.6 = 75% charged
12.3 = 50% charged
And remember, a surface charge of 12.8 can still mean a warn out battery. If you are having problems, charge 24 hours and load test only after it is removed from bike.

LITHIUM ... Way overkill and priced and more for the guy with two dick attitude.

 

Great post!

Frankly, I didn't even know I HAD an AGM-GEL battery in my 2013 Road King till at just 7 months old, it took a crap. I got it to the dealer, they of course tested, then replaced it under warranty, but the very first thing the tech asked, was.... do you leave the bike on a battery tender. Well, yes, of course I do. He said, I'm sure that's what ruined your battery. And I'm sure that it will just ruin this one UNLESS YOU HAVE THE NEW STYLE BATTERY TENDER DESIGNED FOR THESE NEW AGM-GEL BATTERY'S. I of course looked at him like a deer in the headlights, and he began to basically give me the same speech you just did. And explained the conventional Lead Acid tenders will incorrectly charge my AGM-GEL battery, over and over, to the point it will finally fail. And it did. So he sold me the new digital tender designed specifically for my battery, and I have never had an issue since.

 

If you really want to know what happens inside your battery spend some time here readig the Technical information:
http://www.batterytender.com/Battery-Basics/

 

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Well including my own bike and 2 other bikes i maintain for other people giving me 3 amg bike batteries to test at diff times i never had a 12v AGM bike battery ready only 12.6 or 12.7v when properly /fully charged with time to sit & stabilize temp/voltage.

I had each one of those 12v AGM bike batteries on a small 1.5amp maint/float charger till fully charged ,removed charger from each battery and let them sit post charging so they would stabilize temp & voltage post charging before testing their true 100% full voltage.

And what i got was all 312v AGM bike batteries were dead nuts on the 12.9v 100% full charge voltage for an AGM 12v battery .

And i verified my voltage readings were accurate by using a brand new deltran digital battery voltage tester i have along with also using std type hand held digital volt meter i have too that both showed the same 12.9v on the 3 12v agm bike batteries post charging & sitting to stabilize voltage before testing.

I have also tested the std lead acid non agm battery in my every day use car and my wifes too with ensuring batteries were fully charged using the same maint charger and then letting site to let voltage come down & stabilize post charging and they both showed 12.6v on the deltran digital volt meter and my std hand held voltmeter read 12.6v on 1 battery & 12.61v on the other/wife's car battery.

So for me the 100% charge voltages are hitting spot on when i tested AGM & std flooded lead acid 12v bike & car batteries using 2 diff volt meters,thats all i can tell you.

Late time,i didnt post this thread to start any kind of deep discussion ,it was only to let guys know std lead acid vs agm-gel bike batteries do in fact have slightly diff 100% full charge voltages for awareness when testing battery voltage.

Thats because i thought it would be good for guys to know a std flooded lead acid 12v batteries full 100% charge of 12.6v is only 75% charge voltage for a 12v AGM battery so they would be aware of that for testing where you would not want to start out @ only 12.6 / 75% charge (thats correct for a std lead acid battery full 100% charge voltage) with a 12v AGM battery that i verified using 2 diff volt meters in fact has a 12.9v 100% full charge voltage especially when doing a load test that it would liikely fail starting at 12.6v.

And i wouldnt be surprised at all if the 100% battery voltage readings on any battery tech could vary by .01-.02 even .03v-.05v due to things like variance in meters used ,amount of time battery has been off the charger prior to testing its full charge voltage along with outside airtemp & temp of battery itself at the time its full voltage was tested too.

Scott

 

So to me, after reading this, my stock battery is weak, yet the load test done at my Harley dealer which printed out a test results receipt, shows the battery is good. I bet if I didn't mention the possibility of getting a new battery under warranty, then the dealer would have said the battery should be replaced. I didn't watch them test my battery, but I bet they can mess with the settings to make the battery look good.

 

On my 2013 FLHTC I've installed a 500 watt amp and speakers, LED headlight and passing lights (daymaker) and with a high-output charging system (54amps) still finding load exceeds available power sometimes. It seems to depend on the condition of the charge on my OEM battery.
Thanks for this thread Scott, because I am interested in upgrading the battery to 800 CCA lithium. This information is important. And I know It'll last longer under the larger load and charging demands, so it's worth the extra $$$, especially if it solves my problem of power (amps) available.
I found such a battery in the Optima RedTop selling for $185.97. What do you know about that one?