Elite 3600 cells

[RMZDADDY]

I guess I didn't realize sport boaters weren't as informed in terms of how to use and care for their cells. I've got 48 3800's that are 2 years old and still perform well. I know how to balance and charge my cells, use a temp gun, keep track of time, and check amp draw. And since we're being categorized, some of us "sport boaters" are raising families and dont have the money to spend $400 on one set of packs.

[Fluid]

Geeze, lighten up RMZ - if the shoe doesn't fit then don't wear it - I was clearly addressing sport boaters in general. And I was speaking from over 20 years of experience helping sport boaters and racers, and the facts as I presented them are real. Sure, not all SBs are the same, and not all racers take care of their stuff. I was trying to point out that the general statement that not pulling racing amps means the cells will somehow last forever is flawed today.

Actually, quality LiPos equivalent to 24 x IB3600s don't cost $400 either. Cheapbatterypacks.com has PolyR/C 4S/20C/1800s for $76. That makes 8S2P with 3600 mAh for just $304, and 28 ounces less weight. Higher performance cells cost more and weigh more, but you did say 'equivalent'....

You will learn the fragility of current NiMH cells, which do not compare with the robust past generations like the GP3300s and 3800s. And I believe I very clearly stated that I was not promoting abandoning NiMH cells now. But the future is coming, and the R/C hobby in general has already embraced LiPos....meaning the impending death of NiMHs. I just hate to see anyone not enjoy the advantages of LiPos sooner than later. I guess you can string me up for having that self-serving thought.....


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[RMZDADDY]

No offense taken Fluid, although "you sport boaters" sure seemed directed at Reddy and I. I was merely stating what my personal experience with nimh has been and the fact that I can't afford to drop a big chunk of change on one set of packs. I agree that lipos are the future, but I won't be able to come up with that kind of money for a year, maybe two. Ignorance is not the issue here, finances are.

[Fluid]

Few of us are independently wealthy, I understand the cost factor and did not mean to offend. I see too many R/C boaters (particularly gas boaters) get heavily into their boats, then realize they can't afford it and have to liquidate. This is just toy boats afterall.


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[Piranha2]

Well, right now I'm sticking with the NimH's. I'm not even up to the level of a sport boater. I will continue to follow your posts as you guys work this out and I in turn become educated with the use of lipos, maybe then I will switch. And Fluid, you want me to use Lipos so you can read about my Titan blowovers and barrel rolls.

[Piranha2]

oops, sorry Fluid, "you" just want to beat me up with my best boat and best set-up:D Doug's the one that wants me to use Lipos so I'll flip.

[yz120]

[QUOTE=Piranha2;8176]Well, right now I'm sticking with the NimH's. I'm not even up to the level of a sport boater. I will continue to follow your posts as you guys work this out and I in turn become educated with the use of lipos, maybe then I will switch. :D

[Doozie870]

I have been hearing two completly different storys on lipo life expectancy!!
#1- lasts for years no problems.
#2- forget voltage cutoffs,do not use more than 50% of the total mah if you want them to last a year?

Please Help!!

[Piranha2]

Thanks Doozie, you're turning this into the golf swing........

[Quicksilver]

well as a sport boater, I actually never run my boat past a voltage dump. Basically as soon as I loose 5-10 mph I bring it in.

However since I've bought the 16 IB3600s, which I love, Ive yet to run it to any sort of voltage dump. I dont even know how long it would actually run, I just end up running 10 minutes or so and stopping just because I dont want to damage ANYTHING. My batteries, have yet to get above maybe 85 degrees, my motor runs around the same temp and my esc stays cool. I want my batteries to last a good long while, since I'm far from made of money.

[Fluid]

#1- lasts for years no problems.

It can be confusing, perhaps I can help. LiPos can be permanently damaged just like NiMHs. Just like NiMH cells they need the proper care. Fortunately, much of that care can be automated so we don't have to worry about forgetting.

Three basic rules for LiPo safety (from Castle Creations):
Never let the cells get under 3.0 volts
Never let the cells get over 140F
Never store* the pack fully charged, store at 1/2 charge

* Store means more than a month, 1/2 charge means put a little charge back in the cells after running to cutoff. I store at 3.8 volts.

#2- forget voltage cutoffs,do not use more than 50% of the total mah if you want them to last a year?

I disagree, as do most in the industry. The absolute lower limit is 3.0 volts, but most prefer to use a 3.4 volt cutoff in high power use. That is almost all of the usable capacity, but still provides a safety margin. Just like NiMH, taking the cells too low causes permanent damage.

With good care and quality LiPo cells you should expect several hundred cycles before the battery performance degrades. Most battery sellers post a list of recommendations to follow. Read and follow them, or don't and take the risks yourself.


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[Fluid]

well as a sport boater, I actually never run my boat past a voltage dump. Basically as soon as I loose 5-10 mph I bring it in....

QS, this is what I mean. That 10 mph drop means that at least a few cells in the pack have probably dropped below 1 volt per cell, initiating damage. The cheaper or more unbalanced the cells, the more likely this is to happen. Set the ESC voltage cutoff at 1.0 to 1.05 volts per cell and be safer. Don't have an ESC with a voltage cutoff? Inexpensive cutoffs can be found online.

Guys, I did not intend to dis sport boaters - heck I'm a sport boater too, one who happens to race now and again. My whole point was to help to 'wake up' sport boaters who thought they were being "kind" to their cells. Modern cells are not nearly as robust as those of one to two years ago, but they are more costly. The more we know about our power supplies the better we can protect them for a longer life...NiMH or LiPo.

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[ReddyWatts]

This is a very good article about NiMH batteries.

http://www.hardingenergy.com/pdfs/NiMH.pdf

Most brushless controllers have a .9 volt NiMH cutoff set as their default setting. Dont let that standard 1.0 discharge voltage fool you. When you are running full throttle a battery voltage can dip down less than 1 volt, but when you let off of the throttle or the controller slows the boat, it goes back over 1.0. This is not damaging the cell. The battery is not being discharged below its 1 volt capacity. The 1.0 volt standard is for a slow discharge of an actual cell voltage. It may not be the batteries slowing down the boat, it can be the controller. You also have a voltage drop in your wiring that is not figured in, (depending on your wire size, length and amps) that can cause a controller to a premature cutoff . Check your controller default cutoff setting. Also give yours batts a slow charge every now and then to equalize them. I give my NiMH cells a once a month slow charge, year round.

Look at figure 3.7.2. The sharp voltage dropoff starts at 1.2 volts.

Thats my 2 cent opinion.

This article will hopefully help everyone to understand their NiMH batteries.

[Quicksilver]

QS, this is what I mean. That 10 mph drop means that at least a few cells in the pack have probably dropped below 1 volt per cell, initiating damage. The cheaper or more unbalanced the cells, the more likely this is to happen. Set the ESC voltage cutoff at 1.0 to 1.05 volts per cell and be safer. Don't have an ESC with a voltage cutoff? Inexpensive cutoffs can be found online.

Guys, I did not intend to dis sport boaters - heck I'm a sport boater too, one who happens to race now and again. My whole point was to help to 'wake up' sport boaters who thought they were being "kind" to their cells. Modern cells are not nearly as robust as those of one to two years ago, but they are more costly. The more we know about our power supplies the better we can protect them for a longer life...NiMH or LiPo.

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Just for the record those were my crappy old packs, I did state I dont run my IB's to a voltage cutoff. With my amp draw 3600's run a long time, I run them as long as I ran my old cheap 2400mah cells. wouldnt this be ok? I dont want to hurt them after all.

And I guess I'm ignorant in this respect what does a voltage cutoff device do? The boat doesnt stop dead in the water does it? I'll get one if theyre reasonably priced and have no drawbacks.

[Rex R]

when the pack voltage falls below the cutoff point 1 of 2 things can happen (depends on the esc)1) hard cutoff; esc cuts all power to the motor(steering still works) 2)soft cut off esc reduces motor power in an effort to bring the voltage back up(airplanes and helicopters usually, allows for landing under power) , untill the pack hits the hard cutoff point(at which point it acts like the 1st case).
usually if you wait a couple on minutes the pack voltage will recover enough to allow the esc to switch power back on...you may have enough to bring the boat back to shore by the shortest route, DO NOT attempt to bring it back fast! slow is your friend at this point.