Trickle chargers on AGM

[Bluedog225]

Good morning,

Is there a downside to putting a small solar panel trickle charger on an AGM battery in long term storage?

I’d pick it to roughly match the discharge rate of the specific battery. E.g.: 20 watts directly to the battery terminals with no charge controller.

And if I did use the trickle charger resulting in a constant high voltage, I’m reading the text below to say that a boost charge every 90 days is still required. Does that sound accurate? The instructions are below and I could read them either way.

Also, is there a way to have an automatic boost charge applied every 90 days in the Victron ecosystem?

Thanks

 

[sunshine_eggo]

Good morning,

Is there a downside to putting a small solar panel trickle charger on an AGM battery in long term storage?

Storage is Storage, i.e., disconnected with no loads or chargers applied.

I’d pick it to roughly match the discharge rate of the specific battery. E.g.: 20 watts directly to the battery terminals with no charge controller.

This will likely destroy the battery. Float power is variable and often very low especially for AGM. It also varies by temperature. Cold temps = very low self-discharge. Hot temps = faster self-discharge rate.

And if I did use the trickle charger resulting in a constant high voltage, I’m reading the text below to say that a boost charge every 90 days is still required. Does that sound accurate? The instructions are below and I could read them either way.

A boost charge is required when in STORAGE. By keeping the battery floated, it is not in storage.

Also, is there a way to have an automatic boost charge applied every 90 days in the Victron ecosystem?

The maximum repeated absorption interval is 45 days, but that requires the inverter to be on (maybe just in charger only mode), which will draw from the battery even if it's just to measure the voltage.

IMHO, either put it in true storage, keep using it or put it on a reduced float (13.2V) to discourage sulfation and do a periodic charge.

Do not attach an unregulated source to it under any circumstances.

 

[time2roll]

I believe the AGM will perform better with a robust charge every 90 days as stated in the manual.
That is my experience with Optima and Lifeline.

 

[Bluedog225]

Good info as usual.

To confirm my understanding, if I don’t intend to regularly cycle the battery and I want to maximize its useful life I should put it in “true” storage. That is, no load and no charge. And boost per the instruction manual every 90 days.

And thanks!