Battery Puffing Issue

[Pathfinder]

Hi, I'm Nate from Chattanooga, TN. I'm new to this forum but not entirely new to R/C boating.

Anyway, I just went for a run at my local water hole with a CEN Aquajet (don't laugh it was my first boat and I'm rather fond of it) and puffed my lipo. I had recently swapped out the two blade prop for a three blade. The original electronics are long gone, and I'm currently I'm running a ProBoat ESC w/ motor. The same thing that is in the Blackjack 26. The lipo is a 30C 5000mAh 18.5v. The boat ran great save for the puffing, very little heat. My question is what would you say puffed my battery? I realize a 3 blade gives a higher amp draw than 2, but could that have been what puffed the battery or would it have been the fact that the LVC isn't set high enough, or both?

Any input is much appreciated. I really enjoyed my run today. The setup feels perfect, I just need to figure out what to do about my battery. I'd prefer it not explode if I can help it. Lol

[JimClark]

How long did you run for?

[Pathfinder]

I'd say the run lasted about 10 minutes total.

[rayzerdesigns]

probably ran too long..and what is your low voltage cut off set for??

[Pathfinder]

I'm assuming the cutoff is set at 2.7v per cell, I honestly can't remember what it was set to originally. The programming card only allows for two options unfortunately. 3v and 2.7v -- or high and low. If the runtime seems to be the issue to you guys, I'm gonna venture out on a limb and speculate that 2.7 might be a little low for a Lipo, yes?

[TheShaughnessy]

2.7 is to low, I would even say 3.0 is too low and should only be used as a safety. For longevity you should not use more than 80% of the rated capacity. Try timing your runs, more then 4 min of wot running is hard on most setups and you will likely continue to puff cells if you run for longer durations. Unfortunately FE boats have short run times

[Pathfinder]

I will start timing my runs out to 4-5 minutes then and see what happens, and set my LVC higher just in case. Thanks for the responses, guys!

[T.S.Davis]

That setup shouldn't run more than 2 minutes.

What prop were you running?

[Pathfinder]

That setup shouldn't run more than 2 minutes.

What prop were you running?

CNC 42mm 3 blade from this site. I had very little heat on anything except for the battery so I'm not entirely convinced that the prop affected the amperage draw too much, the ESC temped at 99 even (which is about normal for this boat regardless of prop). I checked my battery this morning before leaving for work and the swelling is pretty much completely gone in the cells, it stretched the shrink wrap though.

[Jamey]

Did you happen to check the voltage before charging? 3.5v per cell is pushing it IMO, 3.7+ is better for longer lipo life. I am guessing you may have been down around 3v per cell or maybe lower at which point the puffing starts.

[Pathfinder]

I didn't check the voltage this morning. I'll plug it into the balancer when I get home and see what I ran it to. I picked up one of the voltage checker/buzzers for next time. Hopefully that will help me keep an eye on it at the lake.

[Jamey]

So the puffing went back down without charging, interesting. The constant strain while running must have brought the voltage down low enough to puff the cells but once the load came off and the battery was able to stabilize it came back up. Curious to hear what it is at now. I think you are pretty lucky but I would still keep an eye on that battery while charging it up.

I know it sounds ridiculous if you are coming from rc cars and trucks but really the best way to run an electric boat is to time your runs. By best I mean taking care of your equipment and batteries. Check the voltage and temps after each minute until you get to a good stopping point. My voltages are always within .01-.03v of each other unless I had changed a prop or made an adjustment. I only use LVC as a last resort.

[tlandauer]

Pay a lot of attention to that guy. Just because the swelling has gone down doesn't mean everything is back to normal. For starters the capacity might have been reduced, see how much you can charge back. Also it may be hard to balance and a good sensitive charger may refuse to charge if the cells are too extreme in their voltage . Internal resistance may be up also.

Sent from my D6708 using Tapatalk

[Pathfinder]

So I got a new one for ya (and me), just got home and threw it on the TP610c. 3.6v per cell with a .009 differential between them...This one has me stumped.

**Edit** I went ahead and charged it up (after making sure it was on the concrete floor in my garage near NOTHING). The charge went off fine and put 3247mAh back into the battery. Still no more swelling and no heat on either the charger or the battery. Next run I'm gonna try checking every minute or so to see when the issues start.

[tlandauer]

A 30C lipo for boat use is at the border line if the battery is not top quality brand. As we ask for more speed and the demand becomes ever greater, so have the choice of "C" rating gone up. A higher "C" rating from a reputable lipo maker will mean the lipo can deliver more when asked. In that regard, yours was over working not in a sense that it is being overly discharged into a low voltage threshold. Your cells inside the wrapping were venting gas , it will usually shrink a bit when it cools down or sometimes when you charge back.
Your cells balanced fine, what you need to be mindful now is that since this battery has gone thru a hard cycle, it may not hold the voltage well under load. Typical example is when a guy puts a freshly charged battery(ies) in the boat, he goes for a minute or less, then the ESC hits LVC, he wonders what's wrong. What happened is the lipo had degraded enough that you can put a full charge into it but the moment there is a load, the voltage sags enough to trigger LVC.
All in all, just keep a close watch and as you said, time it.
Always leave no less than 20% reserve in the battery. That means a 5000mah battery should be able to have 1000mah in reserve at the end of your run------in that sense, you were ok, I think may be the quality of the battery coupled with the fact that it is a 30C might have contributed the puffing.
There are different opinions regarding what is considered as a sensible "C" rating for boat use, you need to also be aware of some false claims by certain lipo makers. Read a bit more and you will form an educated opinion yourself.