TL;DR: I need something to discharge roughly 160A at 14V into, or 2.24 kilowatts. Any comments, or answers, with either a) something I can dump a kilowatt into, b) some way I can modify a common item to take 2kW DC at 160A, or c) another way to measure battery max continuous discharge current would be greatly appreciated.
Unfortunately, a large number of other people on the Internet that have this problem are dealing with far fewer amps (160A is pretty crazy.) Thus, any comments to "just google it" or that it is similar to previously asked questions aren't appreciated.
I recently bought a large battery, a Hobbyking Multistar 16000mAh 4 cell LiPo battery. Unfortunately, HobbyKing is notorious for inflating its products' specifications. The max continuous output is variously listed as 15C (which would be 15C*16000 mAh = 15C*16Ah =240 amps) and 10C (which would be 160A). The battery voltage should range from 4.0V to 3.2V per cell during use, so 16V to 12.8V.
I'm hoping that the continuous output is at least 10C, or 160A, but I have no idea what is is. People variously report the actual outputs of Multistar batteries as ranging from 10C to 3C, and there's a lack of actual test data and far too much anecdotal data. I'm hoping to test this myself by dumping 2kW into something and measuring the current the whole time.
Basically, I need something to discharge roughly 160A at 14V into, or 2.24 kilowatts. I've looked up things that take power in the range of a kilowatt, and found that microwaves (~1kW), ovens (~1.5kW), power tools (~500W-2kW), projectors (400W-4kW), and hairdryers (~1-2kW) are my best bets. I'm not exactly sure how to plug my battery into any of these though. Obviously the battery puts out ~2.2kW DC at 160-ish amps. I have no idea what my hairdryer wants, or how to get it to take DC, without a large amount of work. I also understand that this would be far into the range of the mad scientist, and would probably result in a cool explosion.
Is there an easier way to test my battery's capacity? Within reach I have a LiPo battery charger (max discharge rate 1A unfortunately), a decent Fluke, a lot of household equipment, a number of power supplies, a 400W projector, and a workshop with a decent number of power tools/electrical equipment.
Any way to test my battery would be greatly appreciated, including ways to get my hairdryers to take DC, ways to discharge two kilowatts into something that's not an appliance, and any other ways to generally test battery discharge characteristics.
[edit] I know that putting a kilowatt into household appliances is pretty impractical and dangerous if you're stupid. I also now know that it's also damn hard. I've now switched to wanting to make, or buy, a large resistor. For the safety police, I know how dangerous 2kW can be. I have always intended that any test — be it on a proven resistor that should work fine or a household appliance — would be conducted outside, on nonflammable ground, with fire extinguishers, where if something blows up I can make a pretty video and share it with the Internet as opposed to dying from electrocution and burning down my house. I also know how 2kW can melt things and have handled energy on this scale before. I'm not an electrician and I know my limits, but I do know how to handle 2kW to the point where the worst that could go wrong is a few hundred bucks of stuff down the drain and a pretty explosion video on Youtube. I am acutely aware that there is a very high chance that the battery, or whatever I'm sticking 2kW into, might explode, and I will share the video with you all when (if) it does.
Best Answer
To dissipate \$ 1\mathrm{kW} \$ at \$ 14\mathrm{V} \$ you need a resistor with a resistance of \$ R = \frac{\mathrm{V}^2}{\mathrm{W}} = \frac{\left(14\mathrm{V}\right)^2}{1000\mathrm{W}} = 0.196\mathrm{\Omega} \$. You can buy a \$ 0.25\mathrm{\Omega} \$ \$1 \mathrm{kW} \$ resistor on Digikey for $54.95 (Part no. FSE100022ER250KE).
Using two or 3 of them in parallel would dissipate \$ 2.35 \mathrm{kW} \$ which is within \$ 5\% \$ of your goal of \$ 2.24\mathrm{kW} \$. If you use \$ 0.25\mathrm{\Omega} \$ resistors then the current will be \$ \frac{ 14\mathrm{V} }{ 0.25\mathrm{\Omega} } = 56\mathrm{A} \$. So you will need a 8 AWG or larger wire going to each resistor.
Alternatively you could wrap some Nichrome wire around a high temperature core (such as a cinder block) to make your own power resistor. This PDF gives some information on NiChrome wire. 14 AWG NiCr A wire has a resistance of \$ 0.1587\mathrm{\Omega} \$ per foot. NiChrome-A wire has a melting point of about \$ 1800\mathrm{°F} \$. If we run about \$ 29\mathrm{A} \$ through the wire the wire will heat to about \$ 1400\mathrm{°F} \$ which leaves \$ 400\mathrm{°F} \$ of margin.
If you run 5 strands at \$ 32\mathrm{A} \$ each you will have \$ 160\mathrm{A} \$ and be somewhere in the \$ 1400\mathrm{°F} \$ range. To make \$ 32\mathrm{A} \$ we need the resistance of the wire to be \$ \frac{14\mathrm{V}}{32\mathrm{A}} = 0.4375\mathrm{\Omega} \$. To make \$ 0.4375\mathrm{\Omega} \$ we need the wire length to be \$ \frac{0.4375\mathrm{\Omega}}{0.1587 \mathrm{\Omega}/{\mathrm{ft}}} = 2.76\mathrm{ft} \$ (2ft 9in). \$ 2.76\mathrm{ft} \cdot 5\ \text{parallel strands} = 13.8\mathrm{ft} \$. Wrap each of the 5 strands around the cinder block so they ar not touching or alternatively use 5 separate cinder blocks.
Wire each strand to the battery in parallel using at least 12 AWG wire for each connection. Dont make the connection with something that could melt such as jumper cables with plastic handles. Also, the copper wire must be run physically separate in the area near the NiChrome because it is likely that some of the insulation will melt.
You can purchase a 21 ft spool of 14 AWG NiChrome wire from McMaster for $19.13. (Part no. 8880K11) Alternatively you can purchase at 20 ft spool from Jacobs Online for $15.00.