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HomeAircraftHelicopterMain Discussion › Safe low voltage lipo. Are we selling ourselves short coming down at 3.8v per cell ?
04-25-2017 02:12 PM  15 months agoPost 61
Pistol Pete

rrProfessor

Seffner, FL

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Or am I doomed trying aggressive maneuvers on these older tired lipos?
Given your description of events, YES.

Those batts are doomed for low head speed hovering or bench set-up duties.

As a rule of thumb I set ESC-LVC to the next lower number than LiPo alarm. So for me thats 3.3V and 3.4V respectively with newer batts and increase it as batts get older.

When alarm chirps at 3.4V, I just lower head speed which turns off alarm. I get to hover around for at least another minute then finally land when alarm sounds off a second time. Otherwise LVC is next to kick on.

@Juan
Sorry to say you are confusing ESC with BEC.

The only setting a BEC has is regulated voltage output.

~~Enjoying the hobby one flight at a time~~

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04-25-2017 02:19 PM  15 months agoPost 62
JuanRodriguez

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The Villages, Florida

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Yes, ESC is what I meant in my posts..... Senior moment corrected.

OP doesn't mention the use of a BEC at all....

Been there, done that and old enough to know better.....

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04-26-2017 08:44 AM  15 months agoPost 63
betty

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Shenzhen

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Better landing at 3.7-3.8 per cell. It will help lipo battery maintenance.

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04-26-2017 09:47 AM  15 months agoPost 64
joshreynolds777

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Willis, Tx

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No fear there Betty. That's what the cells read when I come down. 3.77 is about as low as I've gotten them.

Except the other day after a couple
Cocktails... flew one I thought was charged.

LVC did its job and lowered the hs, brought it down. And the cells were something like 3.3v-3.4v. Oops !

Charged back to storage level. And the packs beeen just fine.

I'm gonna do like someone suggested and use 3.2v LVC in the esc. And use 3.4v on the alarm and see how things go.

I took apart one of my new 12s sticks to try 6s on the 550 and 570 a bit. Those packs are Brand new, betting they'll hold up to my abuse better than those old turnegys.

Cheers

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04-26-2017 06:45 PM  15 months agoPost 65
EEngineer

rrProfessor

TX

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"I took apart one of my new 12s sticks to try 6s on the 550 and 570 a bit. Those packs are Brand new"

Let me try to understand...

You bought a brand new 12S stick pack......and then took it apart...to take one of the 6S batts within....and try that 6S batt on a 6S machine....right?

Why didn't you just buy a brand new 6S batt for this purpose?

Or do you save that much money by purchasing "stick packs" instead of "singles"?

Logo 600SXs, 800XX, TDR IIs

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04-26-2017 08:44 PM  15 months agoPost 66
joshreynolds777

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Willis, Tx

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No no. My 12s packs are just two 6s packs with Velcro on the battery tray

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04-26-2017 08:51 PM  15 months agoPost 67
joshreynolds777

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Willis, Tx

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Well to be more clear, my 5000mah 12s (2 6s packs) for the 770 were held together with heat shrink. So all I did was remove the heat shrink and use a Velcro system. Followed by needing to make an adapter for the 550 (different connector)

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04-26-2017 09:03 PM  15 months agoPost 68
EEngineer

rrProfessor

TX

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Got it now....

Do the soldered connections for the ESC look good, if some one has soldered them on?

In addition, to the motor connectors?

Just asking....

Logo 600SXs, 800XX, TDR IIs

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04-27-2017 12:28 AM  15 months agoPost 69
joshreynolds777

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Willis, Tx

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Good question. I'll be checking it out !

Wish I could fly today. This Texas weather is insane. Apparently a tornado warning without a cloud in the sky.

Too bad its gusting around 40 miles per hour.

I'm brave. But not that brave :-)

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04-27-2017 08:04 AM  15 months agoPost 70
betty

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Shenzhen

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Just a suggestion. That's why some people use their lipos for over 4 years, but some just keep less than 2 years.

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04-27-2017 11:21 AM  15 months agoPost 71
Richardmid1

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Leeds, England

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Remember , he is talking of OLD batteries so it is conceivable that one or more of the cells dip below 3V under heavy load.... I've seen it myself on two 5 cell packs while being connected to a Watt Meter.
Yes but the LVC prevents the pack from dropping below the set voltage under load So if you set 3.4v/cell you would have to have a cell that was 0.5v+ lower than the rest for it to drop below 3v and that's IF the rest of the cells were all at 3.5v. 0.5v is a huge imbalance even on an old li-po. IF you have a li-po with such an imbalance you probably should dispose of it.

60% of the time, it works every time!

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04-27-2017 07:19 PM  15 months agoPost 72
EEngineer

rrProfessor

TX

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"That's why some people use their lipos for over 4 years"

Yeah...right....

Tired..old...worn out batteries....yeah, that's the ticket to success for sure.

Logo 600SXs, 800XX, TDR IIs

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05-02-2017 07:38 AM  15 months agoPost 73
betty

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Shenzhen

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, my lipos are four years old and they are still like almost new. No matter you believe it or not, it is a fact.

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05-02-2017 08:07 AM  15 months agoPost 74
wjvail

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Meridian, Mississippi

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I tend to fly my batteries down to around 3.7 volts per cell. I test my packs periodically and I typically test them down to 3.55 volts per cell. Even in a safe testing environment I don't see any advantage to running cells down to 3.3 volts per cell.

Attached are two discharge graphs. The first is a healthy 8,000 mAh battery discharged at 20 amps and discharge to 3.3 volts per cell. Notice how little capacity actually remains in the pack below about 3.6 volts per cell.

The second graph is similar but is of an older pack. In this graph the discharge voltage is 3.55 volts per cell. Notice that cell four, the yellow cell, dies sooner and is cascading down to zero before the other 3 cells. In this instance the pack overall voltage remains comparatively high and would continue to fly a helicopter but cell four would be permanently damaged. Most packs will have one cell that dies before the others. Most packs will have one (or more) cells that begin a rapid loss of voltage before the other cells in the pack.

"Well, Nothing bad can happen now."

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05-02-2017 10:42 AM  15 months agoPost 75
joshreynolds777

rrApprentice

Willis, Tx

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I don't think anyone is running cells down to 3.3v. Not intentionally anyway. Under a load older packs might be hitting that in the air. But resting back up to 3.7-3.8v. That's in my case

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05-02-2017 12:41 PM  15 months agoPost 76
JuanRodriguez

rrProfessor

The Villages, Florida

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Josh,

Resting voltage after the fact means nothing......(to a point, that is) when discussing how packs are damaged.

That's why it's important to use those low voltage alarms that triggers when the low voltage threshold is reached....

wjvail's post illustrates that nicely and supports the point I was making a few posts up....

Been there, done that and old enough to know better.....

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05-02-2017 01:15 PM  15 months agoPost 77
Richardmid1

rrProfessor

Leeds, England

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My longest lasting, lowest IR pack has been run down below 3v/cell many times! It's my TX lipo! So it's not JUST running packs down low that reduces their life, how quickly the pack is discharged plays a much bigger role in pack longevity.

This means that the easier you are on the packs in terms of discharge speed your flight time can actually increase exponentially.

If you are a 3 minute hard 3Der you would want to keep the packs no less than 3.8v/cell after a flight or your packs won't last long!

If you can get 5 minutes (typical average Joe trying some 3D) you would be ok going to 3.6v/cell. If you get 5 minutes with stopping at 3.7v+/cell you maybe short changing yourself by 30 seconds/flight.

If you can get 7 minutes+ you would be ok going to 3.5v/cell. If you get 7 minutes+ with stopping at 3.7v+/cell you could be short changing yourself by 1-1.5 minutes/flight!

60% of the time, it works every time!

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05-02-2017 01:33 PM  15 months agoPost 78
Pistol Pete

rrProfessor

Seffner, FL

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my lipos are four years old and they are still like almost new. No matter you believe it or not, it is a fact.
I believe it.

However, the devil is in the details such as:
Size (Cells)
Capacity (mAh)
Load (Max Amp)
Cycles (Discharges)

...and last but not the least...

Brand.

Your profile is empty. Given its optional and this forum is closing but there is no need to have a hidden agenda.

Ever since your first few post I had a hunch you were in the battery industry to which I ask directly and you replied as well. A great start.

Be part of the group with common likes. After all, we even accept people from the UK

~~Enjoying the hobby one flight at a time~~

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05-02-2017 01:42 PM  15 months agoPost 79
joshreynolds777

rrApprentice

Willis, Tx

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I'm always on my cell phone. So I can't see those graphs at all. I'll have to view em on the computer later. Can't zoom in either to pics on this site.
But I AM actually using those voltage alarms. I have them set to go off if one cell hits as low as 3.4v. This only happens on my old packs. Never on the newer ones. How old are the old ones ? No flipping clue. Older than ole Betty's 4 year olds I bet. I acquire a bunch of my lipos along with used helis I've picked up on here. What I'll eventually do is phase them out. But for now when I use them, and hear the alarm, I'll drop down the head speed and it'll stop and I'll finish the pack out taking it easy without setting the alarm off again. . Without even looking at the graph I can agree it might be damaging to the cells to take them low like that I suppose. But they're already old and beat up so I'm not too worried about damaging them further. So long as I'm not risking a ball of fire or anything. And the cells are staying balanced

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05-02-2017 02:22 PM  15 months agoPost 80
Richardmid1

rrProfessor

Leeds, England

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But for now when I use them, and hear the alarm, I'll drop down the head speed and it'll stop and I'll finish the pack out taking it easy without setting the alarm off again
Castle ESC's will do this anyway when set to soft cutoff, it just reduces the rpm enough to stay above the set voltage threshold.

60% of the time, it works every time!

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HomeAircraftHelicopterMain Discussion › Safe low voltage lipo. Are we selling ourselves short coming down at 3.8v per cell ?
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