Multi-stage charging: skipping absorption?

[hey-hey-my-my]

Good morning,


I'm on the road year round in a motorhome with two 100w solar panels (soon to be doubled) charging a 260ah AGM battery via a 20a MPPT charge controller. I also hook up a 30a multi stage mains charger about once a week to properly charge the battery.

I'd like to get the most out of my solar setup. On the material side it's as good as can be: wire gauges & distances, fuses/breakers and voltage are all set up correctly.
On the software side however, there is room for improvement, given that there's no AGM charging profile in the charge controller, only FLA (which forces a monthly desulphation cycle) and GEL (charging voltage not high enough). To this end I've purchased a USB to COM cable which allows me to configure a custom charging profile.

Could you please take a look at my settings below and confirm they're OK for daily, cyclic use with an AGM battery?

I'm hesitant as I've heard of some people setting absorption voltage to the same as float (effectively skipping absorption stage) in order to maximise the daily hours spent in float mode, and to avoid overcharging their AGM battery (the battery being constantly under load, it's hard for the charge controller to estimate DOD).

Considering the battery gets a proper mains charge cycle about once a week, would it be a good idea for me to do this? Any insights would be much appreciated!

Current settings
Absorption charging voltage 14.7 Float charging voltage 13.8 Absorption duration (mins) 120 (see attached image for full settings. N.B. boost = absorption)

Cheers!

 

[Zerax]

You need to get the specification for the exact AGM battery that you have... I'm sure it must be available somewhere. I have never had posh AGMs... but I know that the voltage requirements for flooded cells can vary quite alot...

Also... even after you've setup a new charging profile, I'd keep a careful eye on the voltages (with a good quality multimeter) until I was happy that it was all working as expected.

 

[hey-hey-my-my]

You need to get the specification for the exact AGM battery that you have... I'm sure it must be available somewhere. I have never had posh AGMs... but I know that the voltage requirements for flooded cells can vary quite alot...

Also... even after you've setup a new charging profile, I'd keep a careful eye on the voltages (with a good quality multimeter) until I was happy that it was all working as expected.

Thanks for your reply. It's a Varta LAD260 (which I got as part of an offer - wouldn't have been able to afford it otherwise!). I've searched all over the place for guidance on charging voltages for this model, including the product's datasheet and documentation. It's pretty rudimentary - all it specifies is do not charge at higher than 14.8v.

Guess I'll leave my settings as they are and monitor voltages as you suggest!

 

[PEG]

Hi,there are some good web sites,where they go right in to depth,regarding charge profiles,etc,but these are usually replenish charges.

On a motor home,you will probably have some constant,and regular intermittent loads,during your charging,which will greatly affect any perceived benefit,from a set profile,with no battery use. Even transient loads,from things on stand-by,could affect the monitoring,and charging.

Battery "quiet time",is usually during the night,so you may need a very bright moon

Zerax noted that you need a good quality multimeter,which is excellent advice,when setting and testing DC charge systems.