Hi, I've just been reading a similar project but due to differences in batteries and power want to make sure I get the right regulator.

I need quite a bit of advice here regarding runtime and regulators. I'm looking to buy a 100w rms, or 200w rms class D monoblock car amplifier that will be powered by an 18v 5ah Dewalt lithium battery. I'd like the battery to last 8 hours on a single charge and will be powering a 6 inch mini sub. The mini sub will be a bass back up for the Dewalt toughsystem radio which I believe has Clarion car components in it. Any advice much appreciated.

 

Hi, I've just been reading a similar project but due to differences in batteries and power want to make sure I get the right regulator.

I need quite a bit of advice here regarding runtime and regulators. I'm looking to buy a 100w rms, or 200w rms class D monoblock car amplifier that will be powered by an 18v 5ah Dewalt lithium battery. I'd like the battery to last 8 hours on a single charge and will be powering a 6 inch mini sub. The mini sub will be a bass back up for the Dewalt toughsystem radio which I believe has Clarion car components in it. Any advice much appreciated.

If you know nothing about regulators, you should start with the simple case of a linear regulator: an LM317 for example. They are simple to design and use but they have one MAJOR drawback. The more current you pull through them, the HOTTER they get. For example if the 12V load pulls 1 Ampere, the regulator must dissipate (18V -12V)*1Ampere = 6 watts. A TO-220 package with a really good heatsink can manage 10°C/watt of temperature rise from junction to ambient. In your case that will be 60°C. Assuming the ambient temperature is 20°C, that means the junction inside the regulator will be at 80°C. This is not impossible but you do have to design the heatsink and the mounting with some degree of care.

If this doesn't work for you, then we need to consider a switch mode DC-DC converter. Before you consider building one of these you should think about buying one. This doesn't even include conversion losses.

I'm curious about how you intend to get 100-200 watts out of the 5 Ah battery. If you do it might last an hour: 18V times 5A = 90 watts and 18V times 1A = 18 watts.

 

Thanks for the reply, I had hoped to be able to buy a voltage regulator from my local electrical engineering shop, I know they supply regulators but not sure if that's all I would need. Something similar to these in the link perhaps? Although they are rated to a low ah.

http://www.maplin.co.uk/c/components/semiconductors/voltage-regulators

 

car amplifier

Check what the high limit on the voltage is for the amplifier. Cars do not supply 12.00 volts. They wander around 14.5V to 15.5V. That can save you some waste power in the regulator.

 

That's a good idea and a much better alternative. I'll see what I can find and hopefully the will be a 200w rms subwoofer amp out there.

 

Can you buy a Class D bass amp that will operate directly from the battery voltage?
Most of them are rated to run from 14.4V so some may run at 18V without a problem.

 

I'm curious about how you intend to get 100-200 watts out of the 5 Ah battery. If you do it might last an hour: 18V times 5A = 90 watts and 18V times 1A = 18 watts.

The average bass music energy is much less than the peak required for the large bass thumps, which is why you want a large wattage amp.
So the average draw from the battery will likely be no more than a few watts.

 

The dealers don't appear to state those statistics, probably unnecessary as cars have a stable enough power supply.

 

The dealers don't appear to state those statistics, probably unnecessary as cars have a stable enough power supply.

You could try contacting the manufacturer.

 

Sent emails out to various manufactures, ill let you know how i get on.

 

The average bass music energy is much less than the peak required for the large bass thumps, which is why you want a large wattage amp.
So the average draw from the battery will likely be no more than a few watts.

I guess that means he might get 8 hours out of a charge depending on his musical tastes. Compare:

1. Toccata and Fugue in D Minor
2. Also Sprach Zarathustra
3. Dark Side of the Moon

 

generic 24 -> 12v 10a inverter will probably work, they generally switch mode buck inverters.
i use them when installing 12v 2 way radio's into vehicles running 2 batteries (24v)

 

Something like this?

https://www.amazon.co.uk/Pyle-PSWNV480-Power-Converter-Technology/dp/B003P165NM

I'm assuming by the DC in the code of this battery it's DC?

http://products.dewalt.co.uk/attachments/productdetails/catno/DCB182/