Li-ion vs Li-poly battery?

I m currently searching for a battery that has an high discharge rate and I found these two:
Li-ion: http://www.ebay.com/itm/New-DC-12V-Portable-9800mAh-Li-ion-Super-Rechargeable-Battery-Pack-2-/180832863362?pt=UK_Sound_Vision_Battery_Chargers&hash=item2a1a7a8482

Li poly: http://www.ebay.com/itm/5200MAH-6S-50c-MAX-100C-22-2V-Helicopter-Airplane-LIPO-PACK-BATTERY-BEAST-Nano-/360510967745?pt=US_Character_Radio_Control_Toys&hash=item53f020cfc1

I need 40 volts so If I buy the Li-ion y will buy 4, and 2 of the Li-poly.
I want to know which battery will be better for an high discharge for about 3 seconds, and about 15 times. I will use the batteries to create an high powered electromagnet to move steel.

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frollard4 years ago

under 'chemistries' you can see how each type affects the usefulness in different applications. Also be advised many ebay/china sellers flat-out lie about the chemistry and capacity through poor translation and hopeful estimations.

I highly recommend checking out hobbyking who supply turnigy cells -- good all around price to quality ratio.

Different voltages in BATTERIES is because of a different number of series cells in each battery. (1 cell = 4.2 volts). Because they are in series you will need a series charger to balance the cells or you risk a very short battery lifespan. There is nothing stopping you putting charged batteries in series.
When shopping for batteries, look for the number in series - usually noted as 1S or 4S, etc. The voltage will vary with the number of cells, and the total capacity in mAh, higher = better = heavier/bigger.
Lastly is the C rating, or discharge rate. Discharge rate is the speed at which you can pull power from the battery. 20C on a 5000mAh battery means you can draw 100 amps at the rated voltage. 50C is 250 amps at rated voltage. This is important depending on how much current your cap charger draws.

Kurt Gerhard (author) 4 years ago
Can you recommend me a charger for these batteries:

almost ANY of those would work - just make sure they can balance 6 cells (since you chose 6S). Those 130C batteries you chose are pretty beefy - do you reasonably see using 260 amperes at 22 volts?! (5720 watts peak)...that's a ridiculous amount of power and might not be worth the tradeoff in cost.
Kurt Gerhard (author)  frollard4 years ago
NO, I will use 44.4 volts. I am making a multistage coilgun that doesn't use capacitors, so I need a lot of power to move the bullet through the different stages.
That's fair -- I would just be concerned it's not enough; there is good reason that people use capacitors - they dump an incredible amount of current, and do it a lot more efficiently and happy to do so than even high end lithiums. Will be a very cool project however it works out!
Kurt Gerhard (author)  frollard4 years ago
Here is an example of one using lipo batteries:
Kurt Gerhard (author)  Kurt Gerhard4 years ago
I also need to find a voltage regulator that can give 9v output from the 44.4v. I didnt find one that doesnt drain much current
Voltage regulators are inherently lossy - especially at 44 down to 9 volts.
Look for a DC>DC switch mode converter on ebay or dealextreme - they are very efficient, and some can handle up to 50 volts input. Alternately, just tap off one battery and use a 7809 (or the above smps) on just 22v - much more reasonable to regulate down 55% than 80%.

Kurt Gerhard (author)  frollard4 years ago