RV AGM Charging question..

[JRH]

I Have a 3 year old Renogy 100 amp 12v AGM batt on the toungue of my RV .. it has sat there doing fine . it’s always at 13.2…always floating Since new…It has nothing to do nor connected with my solar or solar trailer. I haven’t touched it other than to glance at it ….it is charged by the factory batt charger that came in the RV.

I thought about disconnecting it today and run it down some and exercising it abit with @ victron IP 12v 22/ 30 amp …I then realized I had no idea what parameters are suggested today to set the charger to…
Never had an AGM…probably won’t have another .. but for now it’s doing fine……

1) should I mess with it.. ?
2) what type charging parameters. ?
3) Is this even needed…? ..
4) what am I solving , if anything.?
5) How long do they last..the way I’m using it. ?
6); .should I do it every now and then. .?

thx., J.

 

[sunshine_eggo]

13.2V is low for float as they specify 13.5-13.8V, and 13.2V is low for the constant voltage of an RV converter. I suspect that it periodically, as often as you disconnect/reconnect to shore power cycles through a 14.4V-ish boost, 13.6V-ish absorption and finally a 13.2V float storage voltage.

AGM should be charged using temperature compensation - higher voltages in lower temps and lower voltages in higher temps. Doubt this has been done.

1) Meh
2) Consult Renogy's specification for your battery (probably printed on the side).
3) Maybe.
4) extended and low voltage float can encourage sulfation and capacity loss.
5) 1 month to 10 years.
6) If your converter behaves as I describe above, once a month, unplug from shore, plug back into shore.

"Equalization" of AGM can be done, but it's different than for flooded batteries. Some manufacturers have a spec, most don't. The common practice is to hold at the peak absorption for longer than is typical (2-4 hours typical, up to 12 hours for equalization). This can recover some lost capacity.

If you truly aren't using it for anything, it's probably better for it to either float at 13.5-13.8V OR completely disconnect it from everything and charge up every 3 months.

 

[JRH]

13.2V is low for float as they specify 13.5-13.8V, and 13.2V is low for the constant voltage of an RV converter. I suspect that it periodically, as often as you disconnect/reconnect to shore power cycles through a 14.4V-ish boost, 13.6V-ish absorption and finally a 13.2V float storage voltage.

AGM should be charged using temperature compensation - higher voltages in lower temps and lower voltages in higher temps. Doubt this has been done.

1) Meh
2) Consult Renogy's specification for your battery (probably printed on the side).
3) Maybe.
4) extended and low voltage float can encourage sulfation and capacity loss.
5) 1 month to 10 years.
6) If your converter behaves as I describe above, once a month, unplug from shore, plug back into shore.

"Equalization" of AGM can be done, but it's different than for flooded batteries. Some manufacturers have a spec, most don't. The common practice is to hold at the peak absorption for longer than is typical (2-4 hours typical, up to 12 hours for equalization). This can recover some lost capacity.

If you truly aren't using it for anything, it's probably better for it to either float at 13.5-13.8V OR completely disconnect it from everything and charge up every 3 months.

First I omitted that I live in it about 90% of the time and it goes nowhere.. too much effort to go moving around …,that’s why they make nice hotels….with bars…….?

its a factory installed WFCO 55 amp converter / charger …it’s always had a 13.2 output..im not aware of how you can adjust anything on it… it just sits there under the towel bin doin it’s thing…

I am not impressed with it but it has worked for 9:years.. I will probably upgrade it and will look to see if Victron makes somthing i can use or adapt with…..dunno..? Haven’t studied that part of it yet…
at that time I’m probably Gona go with a lithium drop in batt mounted in side the pass thru ..( free warmth).
since the renogy is not a cheap,battery ( for AGM) I thought I might try and take care of it before it croaks…
last year I disconnected it and r@n it down abit and then with the WFCO it but that all I have done.

all of my money and time has gone into building out the solar trailer and it’s parts.


thanks a ton for the input…I will go forward with your numbers

th….J.