Li-Ion Power

So I got this boombox with the intention of powering it with li-ion batteries. 18650 batteries are 3.7v (average), so 3 in series supply 11.1v (average). I used 3 in series, 2 in parallel to get 5200 mah, and 11.1v. Fully charged, this pack is at 12.2v, slightly above 8 1.5v alkaline batteries. The drop off is far less, and averages more over it's life as well.



As you can see, both NIMH and alkalines average about 1.2v over their life, and cutoff at about 1v, so an 8 cell boombox is getting 12 to 8v, averaging 9.6v.



3 3.7v li-ion batteries fully charged were at 12.2 v, and it should average 11.1v over its life, with a dropoff around 10v, so it should give a little more power. Here is the box I ended up getting, a Panasonic RX-5050. It's a little rough. I got it off ebay. Skippy provided me with a missing slider







The batteries are slightly longer than a D-cell, so I cut a piece of wood slightly shorter than a D-cell as a spacer. I used the nippled end of a D-cell to contact the boombox circuitboard, and then had a wire going around to a nail on the other end. I then have a test lead with alligator clips on the other side to complete the circuit.

That's some clever work right there!

Do they charge in position from AC? and I love the spacer, although a spin on the lathe and some green paint wouldn't go astray!

Nice work on figuring out the layout for correct voltage.

Tell me, why Li-ion rather than Ni-Hi?

I might have to try that. Do you have to take the batteries apart to charge them?

that is a real good box and that battery setup is a good way to power it up

LOVE IT !!!!

and thats yet more proof that 2x4s are wonderful

Lithium Ion definitely batteries pack more punch and are lighter than alkalines and other technologies. However, the chart is a bit misleading because it is comparing like sized batteries. The problem here is that the Lithium batteries you are using is far smaller than normal D cells. So Standard NiMH D's would provide MORE run time than your Lithium cells without any modifications since they pop right in and provide over 10,000 mah per charge.

Check here and you 'll see that Energizer industrial alkalines have 18,000 mah, which is 3X's+ times the capacity you'll be getting with your lithium cells. Now the boombox you are using here is very thrifty so even standard alkaline D cells will last almost forever. I have a RX-5150 that I use sporadically on/off and the alkaline D's have been in them for probably a year. I don't crank it, but the point is that the life capacity of D's are very good in a thrifty boombox.

http://www.batterycountry.com/ShopSite/alkaline-batteries.html

Terry said:

That's some clever work right there!

Do they charge in position from AC? and I love the spacer, although a spin on the lathe and some green paint wouldn't go astray!

Nice work on figuring out the layout for correct voltage.

Tell me, why Li-ion rather than Ni-Hi?

Click to expand...

The battery needs to be taken out and hooked up to a balance charger. Li-ion has about 2x the capacity for the volume of NIMH. Granted, I am using much less space. You would get more power out of 8x10000mah NIMH, but then you have 8 batteries to deal with.

mellymelsr said:

I might have to try that. Do you have to take the batteries apart to charge them?

Click to expand...

No, the battery pack needs to be hooked up to a 3-cell balancing charger though. It has 4 wires to hook up to the ends and between the three sets.

Superduper said:

Lithium Ion definitely batteries pack more punch and are lighter than alkalines and other technologies. However, the chart is a bit misleading because it is comparing like sized batteries. The problem here is that the Lithium batteries you are using is far smaller than normal D cells. So Standard NiMH D's would provide MORE run time than your Lithium cells without any modifications since they pop right in and provide over 10,000 mah per charge.

Check here and you 'll see that Energizer industrial alkalines have 18,000 mah, which is 3X's+ times the capacity you'll be getting with your lithium cells. Now the boombox you are using here is very thrifty so even standard alkaline D cells will last almost forever. I have a RX-5150 that I use sporadically on/off and the alkaline D's have been in them for probably a year. I don't crank it, but the point is that the life capacity of D's are very good in a thrifty boombox.

http://www.batterycountry.com/ShopSite/alkaline-batteries.html

Click to expand...

The charts simply show voltage drop off for one cell. The capacity in watts for this is 58 watts. Those industrial alkalines have about 3x the power, 172watts, but are throw aways. I'm actually surprised at those. I've never seen alkalines with a capacity that high. Usually they're around 10-12000mah. You can get standard NIMH D-cells, but most of them are simply 2500 mah AA's in shells. You can get 10000mah NIMH: http://www.amazon.com/gp/product/B0...&pf_rd_t=101&pf_rd_p=470938631&pf_rd_i=507846

Also, since li-ion batteries have an almost flat discharge rate. You could may be able to use a 3-cell li-ion pack on a 9 or 10 d-battery box.

>>>>You can get standard NIMH D-cells, but most of them are simply 2500 mah AA's in shells.

This has been a real problem in my area. I suggest you examine all the D-Cell Ni Hi batts you want to buy very carefully.

The Eveready Industrial are a damn good battery, I've used many of them, hard to buy retail here though.

I asked about the Ni Hi vs Li-Ion because from my point of view, unless you already had the Li-Ions laying around, why would you do this mod?

Terry said:

>>>>You can get standard NIMH D-cells, but most of them are simply 2500 mah AA's in shells.

This has been a real problem in my area. I suggest you examine all the D-Cell Ni Hi batts you want to buy very carefully.

The Eveready Industrial are a damn good battery, I've used many of them, hard to buy retail here though.

I asked about the Ni Hi vs Li-Ion because from my point of view, unless you already had the Li-Ions laying around, why would you do this mod?

Click to expand...

I wanted to mess around with li-ion batteries. They're not that expensive:

http://www.dealextreme.com/details.dx/sku.19770

$20 to make this battery pack, and it should last a long time. These are the same kind of batteries in 6-cell laptop batteries.

Guys, it might be dangerous to use boombox on AC power with Li-Ion, especially if batteries don't have integrated circuit inside. Alkaline and Carbon batteries are leaking, Li-Ion - burning...

Brilliant!

I would not try and take that box through the airport....