[Shop-talk] Float chargers

[Jeff Scarbrough]

Sounds like it may have partial bridging of the plates, causing a drain
internally.  In the olden days, there were simple ways to check...I don't
know what you do now - take it to the FLAPS and let them put it on
the machine?

Jeff Scarbrough
Corrosion Acres, Ga.

On Tue, Apr 7, 2020 at 10:34 AM Jimmie Mayfield via Shop-talk <
shop-talk at autox.team.net> wrote:

> The recent discussion about solar-powered float chargers has reminded me
> of an issue that I've yet to understand or resolve...
>
> I have a Battery Minder 12248 (12V 2/4/8A) charger/de-sulfator with
> temperature compensation sensor.  While I've never been able to
> appreciably restore a dead UPS battery using the de-sulfation mode, it
> seems to work fine as a slow charger.  It has several modes -- gel-cell,
> AGM or flooded -- which, near as I can tell, adjusts the threshold
> voltage at which the charger switches from bulk-charge mode to
> float-charge/de-sulfation mode.
>
> Every 12V battery that I've ever connected to the charger, even the old
> AGM batteries taken out of my UPS units, eventually reached the
> threshold voltage and switched over to float mode (usually within 30-45
> minutes for a nearly-fully-charged battery).  Except one.
>
> About 2 years ago I installed an Interstate battery from Costco (size
> 27F, 890CA, 710CCA) in my truck.  It's a flooded battery and if I
> understand Interstate's spec correctly, its capacity works out to around
> 100Ah.  The battery has a resting voltage of 12.6V so it doesn't appear
> to have any shorted cells and has no trouble starting my truck.  So it
> seems to be a normally healthy battery, right?
>
> Thing is...I've never seen my charger go into float mode when connected
> to this battery even when it was nearly new.  With the recent pandemic
> stay-at-home orders, yesterday I decided to connect my truck to the
> charger to stave off parasitic drain (measured to be 20-30mA) that may
> have accumulated over the past week of inactivity.  I'm currently at 16
> hours (@4A) and it still seems to be in bulk-charging mode.  I have
> difficulty believing that the battery needed 50+ Ah.
>
> So what's going on here?  This is the only battery that I've come across
> that behaves like this.
>
>
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