Lipo Battery Comparisons - C Ratings, Voltage Under Load
Are $100+ USD lipo battery pack worth the money? Or are cheap lipos good enough? Are C ratings true or marketing hype? Here are some of my benchmark testing, you might be surprised at the result. Also some of the info I got from SMC facebook page.
First my personal tests.
Photo: I attach a 7 car lightbulb load to the Lipo battery then take voltage readings every 15 seconds for up to 8 minutes. A higher average voltage will indicate a stronger battery pack. Around 2000mAh is consumed by this test (approximately 15amp discharge).
Table: Shows the average voltage of several lipo brands over 8 minutes with a load of 15amps.
Fantom 5300/65c - 7.85 volts @ $105USD/pack
FullyMax 5100/40c - 7.78 volts @ $70USD/pack
FullyMax 3300/35c - 7.61 volts @ $36USD/pack
Tiger 3500/35c - 7.53 volts @$33USD/pack
And my very old Orion lipo batteries at 7.28 volts.
Below are some of my recent tests in 2013.
Silverback 4200/45c shorty pack - 7.62 volts @$45/pack
Turnigy 4200/40c Nano Tech stick pack - 7.66 volts
Things to consider when deciding the best pack are 1) weight, 2) capacity, 3) punch (i.e. average discharge voltage under load) 4) reliability (e.g. does not bloat) and 5) cost.
Summary: It seems lipo battery packs vary by around 0.5 volts from weak packs to the best batteries with highest C ratings. And some of the cheap lipos are only 0.3volts lower than battery packs that cost 3 times more. So yes, best value are the cheap lipos that are very strong and also lightweight.
7.4v RC Car Lipo Battery Comparison
Buy according to brand, capacity, c-rating. These are 7.4 volt hardcase packs for rc cars. Estimated selling price in USD. 3Racing, Fanthom, FullyMax, Intellect, Losi, LRP, Nosram, ORCA, Orion, Racers Edge, Reedy, Revtech, Silverback, SMC, Team Powers, Tekin, Thunder Power, Turnigy Nanotech, Venom Power and Yeah Racing lipo batteries.
Part II. SMC TestsSMC is a well known brand for high performance battery packs. Here are some of their lipo battery tests, comparison and benchmarks as taken from their facebook page (http://www.facebook.com/smcracing).
"6000/65C inboard Nano pack.
Using a Competition Electronics LiPo GFX set at 35 amp discharge. I got the following data on the Turnigy 6000/65C Nano. 5774mAh, 7.36 average voltage and 6.8 milliohms for the internal resistance. The SMC C-Max 5400/50C has the following data. 5667mAh, 7.45 average voltage and 4.7milliohms of internal resistance.
One of the factories told me to make cheaper cells with good performance you must use cheaper materials with some added chemicals to increase the power. They say this will impact cycle life so this made me want to test packs using this combination.
5000/40C cycle 1: 5279mAh
Cycle 24: 4608mAh 13.7% drop in mAh
6000/65C Cycle 1: 5774mAh Cycle 25: 5608mAh 2.9% drop in mAh ($39.95USD from Hong Kong)
6 inches of wires adds 12% of resistance under a 17 amp load
We recommend you use 3.4 volts per cell to increase the cycle life of your packs and reduce the chances of premature swelling.
Typically to get higher mAh you need to lower the C rate.
Higher charge rates will
only improve performance if you run
the pack as soon as it's off the charger as this will result in
slightly higher cell temps which reduces the IR.
I have come to the conclusion that in a hardcase 2S pack the maximum C rate possible is 35 to 40C if the pack has 5000mAh. If the pack has 6500mAh it will have 25 to 30C.
If your racing competitively a lower mAh pack will not have as much power due to a lower voltage curve."
Source: SMC Racing
Where to Buy Radio Control RC Cars and Trucks
At your local hobby shop or try the rc store page.
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