sjslhill
Well-Known Member
- Joined
- Dec 30, 2001
- Messages
- 774
Is lithium ion the same as LiPo?? :blink: After reading these links it made me look at the battery in my cell phone.. h34r:More interesting and related reading:
http://www.consumeraffairs.com/news04/cell_phone_fire.html
http://tv.ksl.com/index.php?nid=5&sid=149247
http://www.consumeraffairs.com/recalls04/kyocera.html
"Again, it's not the cell phones themselves, but the batteries that are raising the concerns. "
With todays technology of chargers and balancers, the biggest risk is in the water. I have ran many times and the prop picks up weeds, moss or a leaf. Over amping a Lipoly pack is a sure way to catch it on fire. However, a fire in the water is not nearly the problem of having one in the pits. A damged pack from a run in the water like mentioned above could cause a fire in the pits.
Having said this, Lipoly is in the future of fast boat racing and we must take precautions to use it safely.
The CAFE group is doing some important testing and baseline development. Other groups like the E-RCU are jumping in with totally un-tested low cost China packs and are highly at risk for a fire in the future, in my opinion.
1. Use a top rated charger and balancer, the balance should not be needed every charge.
2. Never use packs without taps where a balancer cannot be used to check packs.
3. Always charge in a place that cannot be damage by a fire.
4. Never charge at home and put the packs in your car. Packs are most dangerous when >90% charged.
5. Never used damaged packs
6. Your boat must remain dry at all times, water can damage the negative electrode.
7. Never run your LiPoly pack below 3.0V per cell under load, this will shorten the life of it.
8. Store you packs between 50% and 70% charge only
Much more info here http://www.fmadirect.com/tech_data/techdocs/ Jim Cladwell provided this link.
Jim,
Does that 40 cycle pack have taps on it? I wonder how well it's balanced. Some cells could be over charging and plating lithium as they go. Once it reaches a certain point it will burst into flames while being charged. :blink:
No it does not have taps on it Steve. That is one thing I insisted be on them to allow them to run at all. I am going to run NIMH next year as I just bought 36 cells from Steve but I am buying two of the packs to test though one may end up as a present for a friend who flies planes. I know some are thinking they will be good for two heats but from what I have learned that is pushing it toooooooooooo much for me to be comfortable.
Here is the last test data from last weekend. now for a little background we don't have specific sizes of measured courses but a gold cup course would be probably the biggest sized course we would use
We ran on a gold cup size coarse and ran 6 laps, over 2 minute run time and we used 1250 mah and lost 1volt so if you ran 2 heats of 6 laps you would only use 2500 mah out of 4200 so you could easily run 2 heats per charge
P.S. These batteries are supposed to be rated at 4200mah 22C continous and have tapp wires and 12 ga slilcone wires.
Jim Clark
Jim,
Does that 40 cycle pack have taps on it? I wonder how well it's balanced. Some cells could be over charging and plating lithium as they go. Once it reaches a certain point it will burst into flames while being charged. :blink:
I thought your were running 4200mah packs? 1P? They must be 4000mah cells. I would say they are really only 20C for peak and 12C-15C continuous.The test pack is a 4S1P 4000mah 20C continious. My problem with the voltage/mah numbers is that they were achieved running only the best setup boats in the club when we probably should be testing these ont eh slowest boats so we find out if everyone could run them safely. I was under the impression that we drew 40 amps most of the time and could reach 60 amps in the turns and I don't see how we could be pulling those amps and come up with only using 1250 mah and loosing 1 volt.
Jim
I thought your were running 4200mah packs? 1P? They must be 4000mah cells. I would say they are really only 20C for peak and 12C-15C continuous.The test pack is a 4S1P 4000mah 20C continious. My problem with the voltage/mah numbers is that they were achieved running only the best setup boats in the club when we probably should be testing these ont eh slowest boats so we find out if everyone could run them safely. I was under the impression that we drew 40 amps most of the time and could reach 60 amps in the turns and I don't see how we could be pulling those amps and come up with only using 1250 mah and loosing 1 volt.
Jim
We ran on a gold cup size coarse and ran 6 laps, over 2 minute run time and we used 1250 mah and lost 1volt so if you ran 2 heats of 6 laps you would only use 2500 mah out of 4200 so you could easily run 2 heats per charge
P.S. These batteries are supposed to be rated at 4200mah 22C continous and have tapp wires and 12 ga slilcone wires.
Jim Clark
Thats what I thought Howard but here is what some of the plane guy's are saying
They might be exaggerating a bit, but maybe not by much. There are three basic reasons.
A 4s battery will pump a little more voltage to the motor than the 12-cell NiMH (I assume NiMHs; even more so for NiCd of course). More volts will deliver the same power with less amps.
Next, the weight probably does make a significant difference. With less draft you'll have less drag (and that's a _lot_ less weight). Plus, of course, cheaper acceleration.
Third, the internal resistance of the NiMHs expresses itself as heat, and they're running under a higher demand (3300 vs 4200). So you're going to have a loss to resistance.
Add it all up and I believe the 1v drop -- I'm not sure the mah numbers "feel" right but I can't say they aren't.
and
Another interesting question to ask how they are measuring the 1250mAh for Lipos and the 2500mAh for NiMH. If they're measuring what a charger puts back into the packs then that would account for some of the difference too. LiPo charging is more efficient than NiMH charging so if you USED exactly the same amount of charge you'll need to put more back in the NiMH to get it fully charged than you do into the LiPo.
and
Unless they run their boats through a heat with a Whattmeter inline with the battery pack... That's the only way to MEASURE the mAh used, and the only way to ensure consistency from one battery type to the next.
I'm a little worried that allowing a 4S LiPoly in a 12-cell class is giving the people that can afford LiPolys an unfair advantage that will lead to trouble down the road. Between reduced weight, higher voltage, and greater capacity, they ought to be able to run circles around the "old-fashioned" NiMH boats.
Jim
We ran on a gold cup size coarse and ran 6 laps, over 2 minute run time and we used 1250 mah and lost 1volt so if you ran 2 heats of 6 laps you would only use 2500 mah out of 4200 so you could easily run 2 heats per charge
P.S. These batteries are supposed to be rated at 4200mah 22C continous and have tapp wires and 12 ga slilcone wires.
Jim Clark
Could use an Eagle Tree data logger. Then you could actually chart the data too.Unless they run their boats through a heat with a Whattmeter inline with the battery pack... That's the only way to MEASURE the mAh used, and the only way to ensure consistency from one battery type to the next.
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