Simple SLA charging

[fraction]

Lets say I've got a TA2020 amp powered by a 7ah SLA battery.

If I wire up an external 13.6v 2a powersupply to the battery will it

{A} charge the battery if it's been used

{B} power the amp

{C} do both at the same time

and

{D} Not blow up the battery if it's already full and the amp is off.

[Ouroboros]

13.6V is safe as the float-charge voltage to the battery at room temperature, so you will not overcharge the battery even if you leave the PSU connected all the time. The PSU needs to have a well regulated output.

The battery will attempt to take more than 2A from the supply if it has previously been discharged, so it is important that the PSU has current-limiting characteristics that are suitable for battery charging.

[fraction]

Ah, ok. The yuasa can take 1.75a maximum when recharging. I think I'll go for a 1a to be on the safe side. I'm fairly certain this will be enough power with the battery in the middle.

[Ouroboros]

We use the Yuasa 7 amp-hour NPL batteries at work, and they will certainly try to take take more than 2A charging current if they have been discharged to any extent. This isn't a problem, it's just that the charger should be able to operate in current-limit for extended periods. Modern PSUs should certainly be ok.

[fraction]

Hmm. I've just triple checked and Saturnus once said the amp I'm using consumes 350ma, not 2a

The exact power consumption of a TA2020 amp is 350mA (4.2W @ 12V)when driven to just before clipping into a pair of 4 ohms speakers and 60mA (720mW @ 12V) in idle. It's 200mA with a pair of 8 ohms speakers.

The 2a on the back of the amp appears to be a red herring.

Which means I could probably get away with something like this, right? Rapid Electronics - Electrical & Power > Batteries

Which is a proper charger rather than a constant voltage thing, but will also power the amp if it's turned on. I hope. Plus it's 9.99 sterling.

(as you can tell, price is a factor here)

[Ouroboros]

Are you intending to use the amp under battery power only? If you are, then when you connect the charger PSU to re-charge the battery, that is when the charger will current limit for a time until the voltage across the battery has reached the 13.6V float-charge value.

[Ouroboros]

That little plug-top charger should be ok: all that will happen is that the re-charge time of a totally flat battery will take about 12 hours.

[Conrad Hoffman]

Most SLAs have the charging info printed right on them, both the continuous float and the higher timed charge. One caution- don't ever deeply discharge these as it causes permanent damage. Usually if the battery won't quickly pull a high charging current as you try to increase the voltage, it's toast. Every SLA I've ever owned eventually failed because it sat on a shelf too long and discharged below the critical voltage of about 2 V/cell. Never let 'em sit in a discharged state. AFAIK, all schemes of pulse charging, brief reversals and the rest, intending to extend life or rejuvenate sulphated batteries, have proven worthless.

[fraction]

Originally Posted by Ouroboros

Are you intending to use the amp under battery power only? If you are, then when you connect the charger PSU to re-charge the battery, that is when the charger will current limit for a time until the voltage across the battery has reached the 13.6V float-charge value.

I was hoping it would also work while plugged in to the charger.

[speaker]

Just about all my charging questions were answered in this thread; tagged.