Charged state indicator is a little problematic, voltage itself is not enough, it depends on current too. Charging can be indicated based on current. The simplest solution is a current driven relay (+LED +resistor), but it's not cheap nor easy to buy. A little more complicated, but cheaper solution is current sense resistor (0.1 ohm) + OPA (TL071) + LED + 3 other resistors.
Many SLAs have the standby and cycle voltages printed on the label. Does yours?
Here's the sort of thing I would suggest: TI UC3906 Linear Lead-Acid Battery Charger
Here's the sort of thing I would suggest: TI UC3906 Linear Lead-Acid Battery Charger
I own something like this. It's a SMPS and works fine with my 12 V SLAs BUT sadly the dimensions are too big to integrate it into my amp chassis.
What else I can do when I cannot find the same SMPS with smaller dimensions ? It is really hard to find SMPS with 14 V/1 A. This SMPS has the advantage to be connected persistent and safely for many days without overcharging the battery.
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For Input voltages up to 40 V DC is the solution told here by member sofaspud:
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OR this charger was recommended in another forum: the PB137 from STMicroeletronics.
Which solution should be best ?
Did you purchase this item? It looks to me like a "2-amp constant DC output current" that will cook your 7A/h SLA. Use it wisely!!
OTOH, it also says, "Micro-processor controlled three-stage charging extends battery life" which might be almost exactly what you need - 1st stage of charging current, 2nd stage of top-off voltage, 3rd stage of float charge.
If you can employ a circuit that will sense the trigger from 2nd to 3rd stage, that signal could be used to light an LED.
@TheDealer
I'm unsure about using SMPS for SLA charging, because of the hash that may appear atop the DC. I'm not trying to sound an alarm, just stating that don't know, but it may have an effect. But anyhow, I think if it were me I would just install a jack on the amp back panel and not worry about having it inside the chassis.
There is a plethora of SLA charging ICs, with the best choice coming down to your own feature & cost reqiurements.
This is the point I also regarded before
I have 2 options then: 1) Something like the Duracell above named or 2) a separate chassis with SMPS and IC unit.
Do you know a simple method (I know it is not as simple as it sounds) to sign a battery status with an LED light ? (green-orange-red).
Thanks for your help
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