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Old 18th September 2011, 12:38 AM   #11
Motsey is offline Motsey
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I know someone with Ion IPA06 Block Rocker Portable ipod PA Speaker White
The description states it can run for 12hrs on a single charge!
From my working out (rough googled formula) I can run my amp on a 12V 7am sla for only aprox 3.5hrs - thats a huge difference!
Any idea how they last so long, do they use a special battery or do they have special low power commponents?

Last edited by Motsey; 18th September 2011 at 12:49 AM. Reason: some text was in bold
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Old 18th September 2011, 12:49 AM   #12
Saturnus is offline Saturnus  Denmark
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I'm not saying I wouldn't recommend them. You should just know they aren't what the claim to be, so if you're looking for 6Ah, you must buy the "9.8Ah" battery pack (it's actually 6.2Ah).

I know the Ion Block Rocker well, and let's just say that 12 hours of battery time is very much best case. 6 hours at full volume is more realistic (and full volume isn't very loud).

Your TA2020 amp will run 20 or 36 hours at maximum volume on a single 7.2Ah battery, depending on it being with 4 or 8 ohms speakers. This is the tested and measured battery lifetime from the hundreds of people that have built a clone of my Boominator, not a manufacturer claim.

Last edited by Saturnus; 18th September 2011 at 12:55 AM.
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Old 18th September 2011, 01:07 AM   #13
Motsey is offline Motsey
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Quote:
Originally Posted by Saturnus View Post
I'm not saying I wouldn't recommend them. You should just know they aren't what the claim to be, so if you're looking for 6Ah, you must buy the "9.8Ah" battery pack (it's actually 6.2Ah).

I know the Ion Block Rocker well, and let's just say that 12 hours of battery time is very much best case. 6 hours at full volume is more realistic (and full volume isn't very loud).

Your TA2020 amp will run 20 or 36 hours at maximum volume on a single 7.2Ah battery, depending on it being with 4 or 8 ohms speakers. This is the tested and measured battery lifetime from the hundreds of people that have built a clone of my Boominator, not a manufacturer claim.

wow thank you that has made my day

I googled a formula which was obviously wrong =
Quote:
w / v = ahu (amp hour usage) - ah / ahu = hrs it will last

20 / 12 = 1.6 - 7 / 1.7 = 4.1hrs
I am going to definately go for a 7ah sla battery now
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Old 18th September 2011, 01:11 AM   #14
Saturnus is offline Saturnus  Denmark
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Music signals have far lower average value than the RMS value, about 10 times lower in fact. That's why the formula above is incorrect. It also doesn't account for the amplifiers efficiency so it's basically useless.
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Old 19th September 2011, 02:35 PM   #15
dangus is offline dangus  Canada
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I like sealed lead-acid batteries. While they're not exactly light weight, charging is more straightforward than the Ni and Li types. Limit the charging current to about C/5 or less, and voltage to around 14 volts (see the manufacturer's data sheet for specifics). The main weakness is that they will not survive over-discharging, so an idiot-proof system should include something that will disable the power amp or otherwise remove the load once the voltage hits the danger zone (11V?). And users must be educated to treat charging like watering a house plant or feeding a pet; dead is dead.

Unless you habitually listen to music with no dynamic range (pure sine waves, Merzbow), average power consumption will be some fraction of the peak power. For a stereo 10 watt amp, I'd guess less than 1 watt. So that's roughly 100 mA, which a 7AH battery should supply for a long time (3 days?).

Some users of the Ion IPA06 at Amazon.com report over 48 hours of use on a charge. So 12 hours sounds like a conservative rating, based on playing at "full volume" (however that is defined). According to the specs at Ion, it is a sealed-lead-acid battery, the very common 12V 7AH size. Like the one that's sitting on my kitchen counter that came out of a 250VA APC UPS.

Last edited by dangus; 19th September 2011 at 02:42 PM.
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Old 19th September 2011, 08:39 PM   #16
Motsey is offline Motsey
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Quote:
Originally Posted by dangus View Post
Limit the charging current to about C/5 or less, and voltage to around 14 volts (see the manufacturer's data sheet for specifics). The main weakness is that they will not survive over-discharging, so an idiot-proof system should include something that will disable the power amp or otherwise remove the load once the voltage hits the danger zone (11V?). And users must be educated to treat charging like watering a house plant or feeding a pet; dead is dead.
I am thinking of getting this charger for this battery - will that set up be ok?

Also can I buy premade devices or circuits that will disable the power amp when it goes below voltage?

-Thanks
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Old 20th September 2011, 08:34 AM   #17
dangus is offline dangus  Canada
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I prefer a smart-ish charger with V and I limiting. That can be done with a couple of 3-terminal regulators, like LM317. (You'd need to allow several volts drop across each, so the raw supply might have to be around 24V; an HP DeskJet transformer might work.) I don't know anything about that trickle charger. I've come across smart chargers for Power Wheels toy cars, but I think they are sized for bigger batteries (I measured several amps in the initial Quick Charge mode, followed by 1A to top it off, then a pulsed trickle charger.) If you can scrounge a UPS in the 250 VA range, those usually have a 7AH 12V battery, and should make an OK charger, though not suitable for building into a boombox.
This looks like a decent charger.

As for the overdischarging protection... here's a suitable circuit at Maxim.com. Unlike a relay or bipolar transistor, that MOSFET should need essentially no current. On-resistance can be extremely low (I once made a MOSFET speed controller that had lower voltage drop at 100% than the relay it replaced.)

It would be good to include a way to measure battery voltage. That could be a dot mode bar graph display configured as an expanded-scale voltmeter, so all 10 LEDs cover 11V to 13V. But an eBay digital panel meter would be less work, and much more precise. Wire it with a momentary switch to check battery voltage directly, but have it normally powered from the switched 12V, unless current drain really is negligible.
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Old 20th September 2011, 09:43 AM   #18
Saturnus is offline Saturnus  Denmark
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There's no need for undervoltage protection when you use a TA2020 amp with an SLA battery. Minimum voltage for an SLA is 10.5V but the amp will start to lack bass performance at about 11-11.5V battery voltage, cut out completely when you try to play loud at voltages of around 10.5V.

Practically any 2-3A SLA charger will work fine with a single 12V 7.2Ah SLA but keep in mind this is primarily for festival use and select one that have no venting holes so that you don't risk any fluids, beer most likely, water less likely, coming into the charger.
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Old 3rd October 2011, 11:08 AM   #19
fraction is offline fraction
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Quote:
Originally Posted by Saturnus View Post
There's no need for undervoltage protection when you use a TA2020 amp with an SLA battery. Minimum voltage for an SLA is 10.5V but the amp will start to lack bass performance at about 11-11.5V battery voltage, cut out completely when you try to play loud at voltages of around 10.5V.

Practically any 2-3A SLA charger will work fine with a single 12V 7.2Ah SLA but keep in mind this is primarily for festival use and select one that have no venting holes so that you don't risk any fluids, beer most likely, water less likely, coming into the charger.
does that mean a 11.1v li-po cctv battery is going to produce quieter bass when compared with a 12v SLA?
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Old 3rd October 2011, 11:43 AM   #20
Saturnus is offline Saturnus  Denmark
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Quote:
Originally Posted by fraction View Post
does that mean a 11.1v li-po cctv battery is going to produce quieter bass when compared with a 12v SLA?
It won't output as much power. The difference is only about 10%, so not really audible. However if you compare to a "12V" LiFePO4 battery which average 12.8V the difference is a audible 25%.

Last edited by Saturnus; 3rd October 2011 at 11:46 AM.
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