Lipo Question/help

[wickedgmc]

Well the first time I took the Syncron out it ran perfectly both pairs of batteries 2s2p batteries in series. Took it out second time around and had 1 lipo expand and had a good amount of water in it so I chalked it up to water. Fixed water leak, not a drop of water in the hull this time however both of them swelled up a little bit and I need help figuring out why?

Did I over prop the boat?

Not warm the cells enough? (if you do this, how do you do it?)

Just pushing the cells too hard?

I ordered new cells and they should arrive this week, they are 4s and 6s batteries so I can run them in parallel, that will hopefully reduce the load on the batteries

I am currently running a hydra 120, Feagio 9xl and have used m440, x445 and a p225

any ideas

[JimClark]

What kind of lipos and what are the specs of them

[wickedgmc]

max amps cells, spec from website

# NEW COPPER TAB CELLS!
# 6000mah Capacity
# 7.4 Volts
# 44mm X 137mm X 22mm
# 20C Constant(120 amps)
# 30C Sustained(180 amps)
# 50C Burst(300 amps)
# 297 grams
# Comes with Apache/Hyperion Taps

[Rex R]

well if the packs were comparitvely cool(under 150f) then my guess would be that they were not quite warm enough before you started the run. I've got a 2 ton solar heated battery warmer :), but seriously they don't need a lot of pre-warming (around 100F).

[andym]

I run a similar set up with the triton except I use 5s, they should not swell if they can run constant at about 100amp although I have had similar problems with low end lipo. Try some 30c polyquest and remember to preheat to 100-110F. What were your run times like with 6000mah ? and what do you have your cutoff set at as the higher amp draws seem to heat them up a bit if run to long or to LOW.

[motoxbob11]

I keep wanting to switch to Li-Po batteries but you guys keep scaring me. Not only do you have to keep them dry, not overcharge, not over discharge, not drop them, buy a safe to charge them in, but now you have to PRE HEAT them before a run. They sound like my ex-wife!

[Doug Smock]

My GUESS would be that you are pulling around 65 to 85amps with that setup and range of props with a well setup boat. (running free)
How long did you run?? That may be where the problem is. Do you have any idea how much you took out of the packs?
Knocking on wood here, we haven't had a cell puff yet, we are not warming the cells, but of course our lows have been in the upper 80s.


FLUID, What is your opinion on cell warming? At what temp. should we begin this practice?
Thanks,
Doug

[Fluid]

First off, you do NOT have to pre-heat your packs unless you're running in cold temperatures - above 70F is safe, below may be fine too. I have run my oldest LiPo packs starting off as low as 75F and they are still going strong. I don't know where that idea started, although it is true that the cells will have a lower resistance at higher temperatures. They are just like NiMh cells in that regard. And like NiMH cell - too much heat is the enemy.

If your cells puffed under the circumstances noted, there are several possible causes:

* The packs are not very good quality and some cells over-discharged or over heated
* You ran the setup too long and cell temperature got too high - above 160F internally
* Your setup pulls a lot more amps than it should based on what you reported...running wet, not running at a constant speed (lots of accelerations), driveline drag, etc.
* You over-discharged or overheated the packs at some point in the past - often the effects are delayed


.

[Doug Smock]

First off, you do NOT have to pre-heat your packs unless you're running in cold temperatures - above 70F is safe, below may be fine too. I have run my oldest LiPo packs starting off as low as 75F and they are still going strong. I don't know where that idea started, although it is true that the cells will have a lower resistance at higher temperatures. They are just like NiMh cells in that regard. And like NiMH cell - too much heat is the enemy.




.

Fluid,
You'll see a post from time to time on the red forum suggesting the cells need to be warmed to 110' or so. The author does note lower IR, but as I recall on a recent post, suggests that it will help keep the cells from puffing during the first part of the discharge cycle.
If we ever see temps below 70 again (LOL), I will start pre warming my cells.
Thank you sir,
Doug

[wickedgmc]

Anyone have an other opinions on Max amps packs? I have used them for some time without issue maybe they dont stand the test of time? I guess I will prop down till I figure out the issue

Any one have lipo recommendations?

[Doug Smock]

I don't have any personal experience with them. There are guys who swear by them and those that will never use them again.

How long are you running?

We use Neu energy 25/ 50 4900s. So far so good.

Doug

[wickedgmc]

run time is probably right around the 4 minute mark. The time when only one battery swelled was 5 minutes but when I charged the good battery it took about 4000mah so I was right around the threshold of the battery run time.

I have used the max amps batteries for awhile now and have had no issues, and the customer service you get from Austin and Clint is top notch. I have read alot of people saying the cell count is lower and to try and run about 50% of the rated discharge.

[SJFE]

Since this is a lipo question thread I'll add one of my own. Now I think this is how it works but I need some verification here before I spend some cash. If I take two 3s 11.1v 2400mah @ 12c & parallel them. I will then have 3s-6p 11.1v 4800mah with a 24c rating correct? Then if I take that set run it in series with another set Id get 22.2v s6-12p 4800mah @24c correct ??? Man I have a head ache. By the way total weight will still only be 612g. Total cost shipped 92.96 shipped per set. So for under the price of a singe Neu pack I can power the entire boat..For under the cost of 2 packs I can power the boat twice.... Just lookin for a safe lower cost sport setup to hold me over untill I can aford race packs this winter.

[NorthernBoater]

Since this is a lipo question thread I'll add one of my own. Now I think this is how it works but I need some verification here before I spend some cash. If I take two 3s 11.1v 2400mah @ 12c & parallel them. I will then have 3s-6p 11.1v 4800mah with a 24c rating correct? So the end result in series x2 would be 22.2v s6-12p 4800mah @24c correct ??? Man I have a head ache. By the way total weight will still only be 612g. Total cost shipped 92.96 shipped per set. So for under the price of a singe Neu pack I can power the entire boat..For under the cost of 2 packs I can power the boat twice.... Just lookin for a safe lower cost sport setup to hold me over untill I can aford race packs this winter.

No you will have a 3s2p 11.1 V 4800mah pack rated @ 12c.

[SJFE]

Really? I was told when you parallel lipo packs you not only double the mah but also the C rating as well. So you are saying thats not correct? Now I'm fuzzy on the math. 2-3cell packs @ 11.1v in parallel = 3 cells in series and 2 cells in parallel? I just dont get it. I need to go back and read Jay's article in RCBM again. I'm lost.