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.
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.
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.
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.
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.
Hmm. I've just triple checked and Saturnus once said the amp I'm using consumes 350ma, not 2a
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)
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)
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.
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.
I was hoping it would also work while plugged in to the charger.
Yes it will. Given that the charger will be putting out approximately 13.6v, then at low power levels from the amp, the power will be taken from the charger. If the audio level is turned up, then at some point the amp will be trying to take more current than the current-limit of the charger supply. At this point the charger output voltage will drop to the battery voltage and the extra current required by the amp will be provided by the battery.
Ths should all be ok if the PSU is designed for use as an SLA battery charger.
Better & better, thanks Mooly!
Didn't know about this option
What sort of subjective performance gains can be achieved for a TA2020 running from one of these setups (SLA + cheapo 500mA charger) compared to the ubiquitous 12V/4A SMPS bricks? Anyone done this before? I'm intrigued.
Here in the States we have these available for very little money, too.
Wall wart charger
4.5Ah SLA
What sort of subjective performance gains can be achieved for a TA2020 running from one of these setups (SLA + cheapo 500mA charger) compared to the ubiquitous 12V/4A SMPS bricks? Anyone done this before? I'm intrigued.
Here in the States we have these available for very little money, too.
Wall wart charger
4.5Ah SLA
Yes it will. Given that the charger will be putting out approximately 13.6v, then at low power levels from the amp, the power will be taken from the charger. If the audio level is turned up, then at some point the amp will be trying to take more current than the current-limit of the charger supply. At this point the charger output voltage will drop to the battery voltage and the extra current required by the amp will be provided by the battery.
Ths should all be ok if the PSU is designed for use as an SLA battery charger.
Cheers
I can confirm that a 300mah power supply will work with a TA2020, but only up until about half volume.
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