Should IP67 Charge time be similar regardless of DoD?

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murphfish asked Dec 17, '22

Should IP67 Charge time be similar regardless of DoD?

Is it "normal" for IP67 12 v @25A on 225Ah AGM battery to require 5-6 hours charge time regardless of the Depth of Discharge?

17% DoD vs 32% DoD are all taking 5-6+ hours to fully charge

In the app chart to get to float mode:

Charge contributes 36.6 Ah in 5 hours and 57 minutes

Yet, charge contributes 74 Ah in 6 hours 28 minutes

(similar time for every DoD scenario)

I checked advance settings and absorption mode is set to "adaptive". New Batteries (6v x 2, in series) AGM, (had them load tested and great), battery manufacturer settings used in advanced settings. I have also test on default high settings with same results.

Really tough to use when campgrounds (no shore avail) only allow 2 hours, twice a day to run generators. Are smart chargers not the choice to use for this type of regular RV use type which depends on limited generator time?

Any advice or knowledge to share is very very welcomed.

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Answer 1 · 2022-12-18T05:02:23Z

Alexandra answered · Dec 18, 2022 at 05:02 AM

@murphfish

Use the graph in the advanced to see how long in each stage the charge is ie bulk Absorption etc. You will see the difference there.

75ah can be replaced in 3 hours by a 25a charger (not as exactly as that but for the ourpose of explanation) so the rest of the time is just spent reversing all the chemistry .. so mostly done in the Absorption stage.

How long is spends there is the adaptive part.

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kevgermany ♦♦ commented · Dec 18, 2022 at 05:45 AM

@murphfish

Also AGM charge efficiency is only about 85-90%. And the efficiency is lower the closer the battery is to 100% charged.

Another thing you may be missing is that the battery limits charge current, the charger will not be able to push full 25A through the battery at higher SOC levels.

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murphfish commented · Dec 18, 2022 at 07:27 PM

Thank you for your feedback, I value it.

Yes indeed, am utilizing the graph to see the bulk time, absorption, etc. I suppose what I am learning is that on a "smart charger" overall (bulk/absorption combined) charge time is not proportional to DoD?

I do understand that during aborption the amps decrease during that variable stage.

Is nearly six hours charge time normal for 17% DoD? We are trying to go easy on the night time usage so we can charge quicker in the morning but charge time required with this smart charger is still a longer time. For us our priority is get our batteries charged vs elongating the overall life of the battery.

Any thoughts welcome on how best to enjoy the heat and benefits of our RV at night time, with the generator time we are allowed. (4 hours/day). Do we ditch the smart charger or are there settings that will charge to full in the 4 hours of permitted generator time.

Thanks again.

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JohnC ♦ murphfish commented · Dec 19, 2022 at 08:04 AM

Hi @murphfish

4 hrs of genset time at such low DOD is a waste of fuel. Once you reach Absorb stage, maybe 30 min more. You mention 'heat', and if your batts are up at like 25 degC, when they cant accept 10A of charge they''ll be like 98-99% full. Just not worth running it.

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