36v step-down project

[toxictoad]

Hi, I have a spare (tempremental) battery that I want to use to connect other things to just for pratice\testing.

The battery is a dolphin downtube 36v 15Ah with the harness that has the two power cables coming off.

So I was thinking of first connecting this to the 2 power cables from the harness

Waterproof DC48V/36V/24V 15-55V to 12V 3A 36W Converter Step Down Regulator
http://www.ebay.co.uk/itm/261225906457?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Then connecting this
Dual Double 2 USB DC-DC Car Converter Module 12V To 5V 3A 15W Power Adapter
http://www.ebay.co.uk/itm/391095264619?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

And this to the step down converter
Car Audio Stereo HiFi Amplifier 2CH 500W Power Motorcycle Amp MP3 Speaker 12V
http://www.ebay.co.uk/itm/Car-Audio-Stereo-HiFi-Amplifier-2CH-500W-Power-Motorcycle-Amp-MP3-Speaker-12V-/142045059466?hash=item21128b998a:g:~sAAAOSwbYZXeizL

Then hooking up some speakers and mp3 player...power on

This look like it will all work together?

 

[danielrlee]

IMO the 12V converter isn't quite powerful enough and it'll cause the amp to distort when the bass plays.

Also, the amp is crap. If you can stretch your budget a little further, get something based on a Tripath TA2020 chipset (search for TA2020). It'll have a lower power consumption, will be louder and have much, much lower distortion levels.

 

[toxictoad]

Thanks danielrlee,
Found a TA2020 amp in price range. What am I looking for when it comes to the step-down converter?

Would this do it?
http://www.ebay.co.uk/itm/200W-15A-12V-Voltage-Power-Module-Step-down-DC-DC-8-60V-to-1-36V-Buck-Converter-/311563030853?hash=item488a9a9145:g:hRsAAOSwAuNW3-~3

 

[danielrlee]

I'd say that buck converter is about perfect for the task.

To ensure a long and healthy service-life, it is good practice to de-rate power supplies by 50%. Treat that DC converter as a 7.5A supply. In my experience, TA2020 amps are happiest with a 5A supply when playing heavy bass at full whack. Add to that another 2A for a power hungry media device and you've covered your bases nicely. If you dial-in an output voltage of 13.6-14v from the supply, you'll eek out the most power from this amp while still keeping it happy.

Which amplifier have you settled on?

Also, do you know what speakers you plan to use? As with any low powered amplifier, high sensitivity speakers are your friend and will give you the most volume from the available power. In fact, you'll probably be surprised how much noise you can make with 20W given the right setup.

 

[toxictoad]

What do you mean here?

If you dial-in an output voltage of 13.6-14v from the supply

Looking at the Lepy LP
http://www.ebay.co.uk/itm/331837097562?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

For now just planning on trying the speakers I have gathering dust, don't know specs but I have 2 L|R from a 5.1 digi home system and a pair of full range hi-fi speakers. I know there won't be any bass of the small ones as they're used with a sub but I could try it out

 

[danielrlee]

Nothing wrong with that amp. I've used the board from the exact same model to replace the amplifier on a crap portable PA system. Completely transformed the system into something great for camping and outdoor parties.

If you dial-in an output voltage of 13.6-14v from the supply

What I meant here is that the output on the DC converter can be adjusted by turning the screw on the small blue potentiometer and that the amp works best at around 14v. Do you own a multimeter? You will need one to set the output voltage of the DC converter initially.

I also forgot to tell you about another amplifier option:

http://www.ebay.co.uk/sch/i.html?_odkw=tpa3116&LH_PrefLoc=2&_sop=12&LH_BIN=1&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xtpa3116+bluetooth.TRS0&_nkw=tpa3116+bluetooth&_sacat=0

These are based on a newer TPA3116 chipset by Texas Instruments. All the boards in the above link also feature a bluetooth input for wireless audio if that interests you. The TPA3116 is a little more detailed than the TA2020 (although the TA2020 is still amazingly detailed) and is a more powerful amplifier, but isn't as efficient, nor is the bass quite as full as with the TA2020.

Another reason why I usually recommend the TA2020 for battery powered setups is its lower voltage input. It will happily accept 12-14.6v, where the TPA3116 requires 18-24v. This isn't an issue where you are using an adjustable DC converter, but helps simplify things if you require a battery only solution and want to stick to a low cell count or SLA.


EDIT: I've been reading about developments to the TPA3116 based boards since I last looked at them and it appears that they are generally regarded as superior amps to the TA2020 based boards. Also, they do apparently operate on voltages as low as 4v with reduced power capability. You won't be disappointed with either of them really.

 

[toxictoad]

Cool on the TPA3116, don't really wanna spend much on it atm (did see a nice one though!) but can see myself upgrading and making a good mobile sound system, maybe get a higher Ah 24v or something...this year camping (24 of us) all we had was a very small pair of BT speakers, crowd around the speaker time!

Yep, I have a multimeter so that's all good. I thought it would adjust voltage automatically for some reason. If I wanted to add something else that required <> power of the amp, how would it work?
E.g. 36v battery - step-down converter 1 set to 14v for amp
36v battery - step-down converter 2 set to 24v for light or would they both come from the same converter?

 

[danielrlee]

You would require another DC converter for each voltage you wish to output. Their inputs would all connect to the battery in parallel as per your example.

FYI, the TPA3116 amps apparently sound best operating on 19.5v.

 

[toxictoad]

Cool man, thanks for all the advice...I just gotta get the bits and put it all together now. I'll post back when I get somewhere or get stuck

 

[toxictoad]

Got it all setup n working. I connected 2 5.1 speakers and a sub-woofer and it sounds really good. It's not a mobile solution right now but stage one is done