Li Ion battery Pack for Amp6

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Since I am a proud owner of an AMP 6, and a Sonic T Amp this is for those who are using T class amps as their iPod/MP3 player amp, and don’t want a bulky lead acid battery or a Ni-cd/Ni-Mh battery, then you might want to consider Li-Ion or Li-Polymer batteries. So in the spirit of Jan’s 41hz.com DIY amps, it might be cheaper to make your own battery pack. Since I am a newbie to amp building, I haven’t gotten into how a power supply or a battery, or type of battery makes an amp sound, so I am definitely not a hardcore audiophile. So for you true audiophiles, you need not read further. For those who are considering portability for their amp and speakers then by all means read on. All I know is I wanted a portable amp for my mp3 player, portable batteries, and portable speakers so I can take them when I go outdoors, play sports etc.

To save you time I will list exactly what you need to get.
With Li-Ion cells, you need a PCB wired to them to prevent over charging and discharging. The PCB will cutoff the battery once it goes below a certain voltage so you cannot damage the cell. And of course it needs a specific charger too, you cannot use one for NiCd or NiMh or SLA, unless it has settings for it. Some expensive models will charge any type of battery, you just will have to pay a lot more for that type of charger. You also need some PVC shrink wrap to help cover the batteries, which protects them and covers the soldering connections. You will need some battery connectors, which you can get at any Hobby shop. And the last thing, which is optional, is a "Fuel Gauge" for the battery. This was the coolest feature, it is a separate PCB that plugs into the primary protection board that has LED's on it. The LED's correspond to the percentage of charge left on the battery, so it takes the guess work out of how much juice you have left. And since they are Li-Ion cells, it will help you determine when to stop using your device to prevent over use of the battery. Sure you can rely on the primary PCB to do that, but why take that chance? With the gauge, just take a look and unplug the battery and recharge it before it gets too low. Li Ion cells are delicate and overuse causes them to shorten their lifespan. And for those of you worrying about the size and weight of the PCB’s, don’t worry, they are tiny! The PCB for my battery is about 4mm thick and shorter than the length of a single 18650 Li Ion cell and about as wide. And the Fuel gauge pcb size is 42mm x 22mm x 4mm. Also there are lots of sites selling battery supplies, but the one I chose was www.batteryspace.com because they gave me tech support and answered my questions when I didn’t even buy anything. Besides, they had cheap prices so I went with them.

Regarding construction of the pack, when you buy your cells, MAKE SURE THEY HAVE SOLDERING TABS! If you decide to order from batteryspace.com Just select the option from a pull down menu below the pic of the cells. Other battery supply websites have options to buy cells with tabs, so before you order make sure you select soldering tabs on the cells. Believe me this will make your life a lot easier, not to mention a lot safer. Li Ion cells can catch fire if not taken care of properly, and a hot soldering iron is definitely something that should be used with care around them. Anyway, if you are making a portable pack for your portable amp, you might just need a 4 cell pack at 2400 or 2600mah at 14.4v. That will provide several hours of use at max volume of your Amp6 (or Amp3). To make a pack like that you would wire the cells in series, and you can either make it a flat pack (4 cells side by side) or a 2 x 2 configuration with 2 cells flat side by side and the same configuration on top. With Li Ion, each individual cell is 3.6 or 3.7v depending on which version you get. And since the 41Hz amps, and other smaller portable amps need 12v DC to operate, the minimum voltage you could use is 14.4v .

Here are the links to the stuff I used for my battery building project.

Link to the charger http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2791

Link to the Li Ion Cells
http://www.batteryspace.com/index.asp?PageAction=VIEWCATS&Category=739

Link to the PCB
http://www.batteryspace.com/index.asp?PageAction=VIEWCATS&Category=988

Link to PVC Shrink Wrap
http://www.batteryspace.com/index.asp?PageAction=VIEWCATS&Category=306

And just in case you need it, you can ask questions in their forum
http://forums.batteryspace.com/forums/


You will also need to buy some battery bars so you can solder the tabs of the cells together. For that you can get some at your local hobby store that sells RC Cars, Planes, Boats, etc. I used Novak mini bars since the regular ones are too wide for 18650 size Li Ion cells. There are also some steps of constructing the actual pack I left out to keep this shorter, but you will also need some kind of adhesive to glue the cells together after you have soldered and wired the pack and pcb. Once you have glued and wired the pack, you must then shrink wrap the whole thing. Not only will it protect the batteries, but it makes it look a lot better too. Once it is shrink wrapped you can then glue or Velcro the Fuel Gauge pcb to the outside of the shrink wrap.

If you haven’t built a battery before, then click on this link. The author is using Ni-Mh cells, so it doesn’t show the wiring of the PCB to the Li-Ion cells. All other steps are the same, you just have to add an extra step to wire the pcb to the soldered cells, and you have to make sure you attach the right cell to the right portion of the pcb.

http://www.batterieswholesale.com/battery_tips/assembling.htm

If you have ever lugged around an iPod Hifi or an Altec Lansing IM-7 with their C and D cells (that are non rechargeable and very expensive) or a Lead Acid 12v battery then you can appreciate the weight savings of Li Ion.
 
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