Nautilus battery charge question

apoc555

Hello. I just bought a nautilus ultra agm deep cycle battery. After it was almost charged, i hears gargling noises. Not very loud but noticeable close by. I used charger and battery provided in pics. Csn someone tell me if I'm doing something wrong or if sounds are normal please?

Estragon

Gargling noises in an agm battery are not good. I can't tell from the pic if the charger has an agm setting, but some agm need a lower absorb voltage setting. At higher voltage, bubbles can form, and the battery may vent, rather than recombine gasses, resulting in permanent impairment.

apoc555

Says it's suitable for agm but I don't know why it made noises. Should I choose slow charge or does it matter?

BB.

AGMs typical need around 14.2 to 14.4 volts when charging (at ~70-75F room temperature). What voltage is the battery when it is making noise?

Generally, you don't want to hold 14.x volts "forever". The voltage should be dropped back to float voltage of somewhere around 13.2 to 13.8 volts (check battery mfg. manual for charging recommendations) after about 2-6 hours of "absorb" charging (battery voltage held at ~14.4 volts--If battery is only slightly discharged, closer to 2 hours, if battery is deeply discharged--to 50% or less state of charge, then ~6 hours).

Ideally, the change from charging to float voltage would be when the battery drops to less than ~1% rate of charge in absorb (i.e., 100 AH battery, when charging current falls to less than 1.0 amps).

Gurgling in AGM batteries is typically a sign of too high of charging voltage. And batteries will eventually vent (expel hydrogen and oxygen gasses through pressure relief caps) and you cannot restore lost water. Also the gurgling/overcharging can overheat the batteries and catalyst (if present) used to recombind the H+O gasses. The catalysts only have a limited life before they fail (more gassing, using up catalyst life).

-Bill

apoc555

It stayed at 14.8 the whole time I believe

BB.

That is too high of charging voltage for AGM (again, check battery manual to be sure).

And once the battery is charged, either disconnect the charger (AGM batteries can go 3-6 months between charging in cooler weather and if good shape)... Or a much lower float voltage (~13.2 to 13.6 volts) for long term charging/storage.

-Bill

apoc555

Thank you for help guys. Gonna see if I can get a different charger