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Jul 19, 2019, 10:18 AM
Bobbybrown
Quote:
Originally Posted by MCSGUY
The one I worked on used a hydraulic unit tied to the yoke to provide movement resistance. We installed a testing servo system that rotated the unit through its range of motion while plotting its force/deflection curve. The resulting graph became part of a permanent data record proving compliance to the design spec.

Joe
That's interesting, I don't recall any charts or graphs being generated for the B1 program, but I do remember there was a very complex computer algorithm that determined not only changes in stick position, but also rate of change as well. Magnetic reluctance was adjusted accordingly using an array of dampers that contained magnetorheological fluid. I wonder if anyone uses plain hydraulic systems anymore, I'll have to ask some of my friends at Udvar Hazy how it's done these days. I am fairly certain the C-17, and modern fighter aircraft use a very similar magnetorheological system in the control sticks.
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Jul 19, 2019, 12:55 PM
pull up -- PULL UP!!!
Quote:
Originally Posted by jj604
I can top that. I had a 3S 1300mAh Turnigy Graphene that was run completely flat (as in zero volts) and stayed at zero volts for for several days TWICE a year apart and still recovered reasonably.
I'm clever enough to have done that twice. Each on a CNHL 1300 G+ from the same purchase. Both times left the battery plugged into a plane and discovered the next day, completely flat.

The interesting part is one battery came back and continues to perform normal flights. The other stayed stone cold dead. My conclusion is it's hard to draw a conclusion.
Jul 19, 2019, 04:26 PM
HAL... Open the damn doors!
jfetter's Avatar
Quote:
Originally Posted by rowdyjoe
No offense intended but, please challenge your source to duplicate my goof (safely) using any "standard" LIPO and honestly report the results. I've seen too many puffed and ruined standard LIPOs in the last 5 yrs. to believe that story without evidence.

Roger on the "baby it". I usually charge at 3C but, backed it down one notch to attempt to revive the battery. After starting the charge, I thought about dropping it down to 1C but, thought "what the heck, it's ruined anyway". I'll know better if it happens again.
The reason I offered his comment instead of my own was to try and provide a little more credibility. Truth is I've done this a few times myself, personally, hence why I asked him in the first place...

Jack
Jul 19, 2019, 04:34 PM
Registered User
Ryguy's Avatar
Given the vast knowledge of lipo wizards that frequent this thread...

I’ve heard storing lipos at cooler temperatures improves longevity. I currently store mine in my beer fridge, but I’m wondering if doing so actually makes a difference. I’m always nervous too pulling them out and popping them on the charger at 2-3C when I know the IR is higher due to the cooler temp. Also, I’d like the space for more beer. Would just storing them at room temperature make any difference?
Jul 19, 2019, 05:00 PM
pull up -- PULL UP!!!
I doubt there's any hard science on benefits of cold storage. No doubt someone will give you any answer you want. But it is known that cold lipos have a lower fully charged voltage. So it would be an overcharge condition to shove 4.2V into a cold lipo, or conversely drop a fully charged lipo into a fridge.
Jul 19, 2019, 05:23 PM
Frankenstein recycled packs
rampman's Avatar
Quote:
Originally Posted by Ryguy
Given the vast knowledge of lipo wizards that frequent this thread...

Ive heard storing lipos at cooler temperatures improves longevity. I currently store mine in my beer fridge, but Im wondering if doing so actually makes a difference. Im always nervous too pulling them out and popping them on the charger at 2-3C when I know the IR is higher due to the cooler temp. Also, Id like the space for more beer. Would just storing them at room temperature make any difference?
I have many lipo's that are 10 years old.
I keep them in a fridge. I live in dry AZ but others should place them in a ziplock type bag and then the fridge.
Always pull them out 2-3 hours before charging
Never charge under 60F (I won't see that for 4 more months )
If charging under 60F only charge to 4.1 volts per cell and at 1C
Storing at room temperature is OK but not as good.

I look at it this way. Treat your lipo's like reptiles. The warmer the pack is the faster the little guys, electrons, move. If kept at/near 40F they will not move fast and not burn as much energy just sitting there and thus live longer.

Rick
Jul 19, 2019, 07:19 PM
Registered User
Hubert1's Avatar
What about storing them at -30C? I have never gotten a solid answer on whether or not this is OK. I pretty sure it's fine, might try it this winter on some batteries that would otherwise be trashed at the end of the season.
Jul 19, 2019, 07:44 PM
aka JetMan Joe
MCSGUY's Avatar
Thread OP
Quote:
Originally Posted by Hubert1
What about storing them at -30C? I have never gotten a solid answer on whether or not this is OK. I pretty sure it's fine, might try it this winter on some batteries that would otherwise be trashed at the end of the season.
Most everything I've read advises we avoid freezing storage conditions.

Joe
Jul 19, 2019, 08:53 PM
HAL... Open the damn doors!
jfetter's Avatar
There's some anecdotal evidence that the fridge is good, a well known user on here for years touted the fridge as the key to his packs longevity. Bottom line, heat is bad, my garage for example stays above 100 all day long in the Summer, so IMO, indoors under A/C is probably all you need to do...

Jack
Jul 20, 2019, 11:47 AM
Registered User
There is no question cool-to-cold storage - not freezing - is better for longevity. Very high storage temps greatly shorten calendar life.

But in high C-rate use cases, the difference for short-term storage is hardly significant, IMO only worth it over many weeks or months.

Let the batteries warm up overnight, condensate evaporate etc before using.
Jul 20, 2019, 01:37 PM
Registered User
dcwwcp's Avatar
I know it has been said before, but thank you very much for all the hard work and posting the results for all of us to see. I am trying to get caught up on reading this thread and interpreting results for applying them to my application. I like to fly sport and 3D planes. Of course this means I am interested in how bad the voltage sags when punch short bursts of full throttle. I find that even though my calculated max. amperage at WOT is only pulling approx. 15C to 18c, The voltage drop I see in the telemetry is disappointing on the batteries I have been using. All the hype, and then the actual results, on the Pulse batteries made me want to sell them the first time I used them. The roaring tops are a little bit better, and so was the price, but the voltage sag is still a let down for the hype of being rated at "70C" and only asking them for 16C. Your results have me interested in the Hobbystar, Hyperion, and dinogy batteries. although the hyperion doesn't seem to be available...if you have any advice I will be glad to listen and greatly appreciate it.

Thank you again for all the work, I am excited to find a battery that I feel good about purchasing.
Jul 20, 2019, 03:15 PM
Registered User
Hubert1's Avatar
I have heard, don't "freeze" before. The thing is, the freezing point of water shouldn't have anything to do with a lipo battery. I'm pretty sure that the liquids in a lithium battery will freeze (turn into a solid) at a significantly lower temperature than water. As I said, I'll give it a shot, and see what happens. We don't get very many days below -20C anyway.

Now back to the topic of the thread. I'm getting very tempted by the HRB batteries. They are very cheap and easy to get here in Canada as Amazon has a decent selection. They seem like they might be a bit too lightweight for EDF applications though, but I guess I could get the 6000 which is still only just over 800g.
Jul 20, 2019, 03:56 PM
Nose down, you're gonna stall
rowdyjoe's Avatar
Quote:
Originally Posted by Hubert1

Now back to the topic of the thread. I'm getting very tempted by the HRB batteries. They are very cheap and easy to get here in Canada as Amazon has a decent selection. They seem like they might be a bit too lightweight for EDF applications though, but I guess I could get the 6000 which is still only just over 800g.
Do you mean this "HRB 22.2V lipo Battery, 6S Graphene lipo Battery 5000mah 100C XT90 " for $135.00 US? That's priced higher than the new HK Panther of the same size. HRB seems to be very "proud" of their batteries.
Jul 20, 2019, 05:56 PM
Registered User
Quote:
Originally Posted by Hubert1
I have heard, don't "freeze" before. The thing is, the freezing point of water shouldn't have anything to do with a lipo battery. I'm pretty sure that the liquids in a lithium battery will freeze (turn into a solid) at a significantly lower temperature than water.
All irrelevant to the price of tea in China.

Each chemistry has a set of temperature specs, separate for charge vs discharge.

The datasheet may state discharge is safe down to -10, but charging at a high rate (say 0.5C) at that temp may permanently render the battery to unrecoverable scrap.

As you get closer to that point, lower and lower C-rates are delivered / tolerated.

Using "freezing" as a colloquial attribute of the temperatures is accurate, valid, if not precise. Because the danger curves are different for each chemistry and in the LiPo world most people have no idea what the actual chemistry is, and each maker has their proprietary tweaks, etc.

And nothing to do with phase changes, neither water's nor cell electrolytes.

LFP as an example, and note I do not believe Winston Chung's claims wrt ThunderSky's Yttrium doping

https://gwl-power.tumblr.com/post/77...on-what-is-the
Jul 20, 2019, 06:00 PM
Battery Puffer
I asked my factory about freezing lipos and they said freezing can crack the electrolyte and not to go below 40F if using a fridge. Lipos degrade faster the warmer they get. So using a fridge in a hot climate makes sense and also for long term storage in a hot climate. But anything under 70F is a good temp for storage.


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