What low voltage cut off to set ESC at??

• 04-22-2013, 10:12 PM
Team arsy car
What low voltage cut off to set ESC at??
Only running Traxxas 2S batteries

Recently bought Hobby Wing SC8 ESC, factory set at 3V low voltage shutoff, however looking into it on the wonder WEB I see 3V is absolute minimum and recommendations ranging from 3.0V to 3.4V. Supplier says leave it at factory setting, any recommendations???

T.A.C
• 04-23-2013, 01:22 PM
I set my esc's to 3.2-3.3 volts some folks set them higher yet.

Andrew
• 04-23-2013, 02:25 PM
Jimmie Neutron
3.3-3.4v is what I suggest.
Keep in mind that when you pull the trigger voltage is dipping down... so if you have it set for 3v chances are voltage is actually dipping below that point.
• 04-23-2013, 04:55 PM
ksb51rl
[QUOTE=Jimmie Neutron;5488014]3.3-3.4v is what I suggest.
Keep in mind that when you pull the trigger voltage is dipping down... so if you have it set for 3v chances are voltage is actually dipping below that point.[/QUOTE]Not chances: definite.
Examples of voltage sag, recorded by an Eagletree datalogger, note the blue lines dipping low.
3S pack
[IMG]http://pic20.picturetrail.com/VOL1338/10348139/19776559/395731109.jpg[/IMG]

2S pack
[IMG]http://pic20.picturetrail.com/VOL1338/10348139/19776559/395734985.jpg[/IMG]

I'm guessing that Traxxas sets theirs at AT LEAST 3.4 volts per cell, and so do I, but my "at least" equals 3.5.

A pack with a voltage of 3.0 volts under load is no fun. You can even tell the difference between a pack with 3.4 vs 3.5 volts per cell if you pay attention. All the lower LVC is doing is killing your battery(ies) 'cause it aint no fun after 3.4.
• 04-23-2013, 06:23 PM
Jimmie Neutron
I knew it was a definite... but I don't like claiming definites without graphs or other proof to back them up. It seems that word, "definite", makes some posters challenge the information given.
• 04-23-2013, 06:45 PM
Jakey
KSB is correct, it is [B]DEFINITE![/B]
• 04-23-2013, 07:43 PM
ksb51rl
What low voltage cut off to set ESC at??
[QUOTE=Jimmie Neutron;5488166]I knew it was a definite... but I don't like claiming definites without graphs or other proof to back them up. It seems that word, "definite", makes some posters challenge the information given.[/QUOTE]
Gotcha Jimmie. Just trying to back you up, not contradict you. I have certain advantages with such posters that you lack. ;) Besides, I remembered where to find the pretty graphs.
• 04-23-2013, 08:01 PM
Jimmie Neutron
oooooo pretty graphs!
:wub:
• 04-23-2013, 08:36 PM
Jakey
A graph really isn't necessary for this one, just some simple math. Approximately 98% to 99% of the useable pack capacity is gone by the time the average RC pack reaches 3.4 volts per cell. Added to this the pack voltage is past the good performance plateau and well into the steep drop noted at the end of a discharge curve. Lastly, a LVC setting lower than 3.4 volts per cell allows the real possibility of an individual cell dropping to or below 3.0 volts near the end of the discharge cycle and 3.0 volts is the recognized minimum below which cell damage occurs. Or to put it more simply - with the LVC set at 3.4 volts per cell instead of ... let’s say 3.2 volts per cell, changes the the runtime by one minute at most. So why risk permanent pack damage for just one minute of slowing runtime?
• 04-26-2013, 02:59 AM
rag6
with my 3.5 setting, when i check the cells, they usually are around 3.7 at rest. this is with both my vxl, and mmps. leads me to believe the vxl is set to 3.5. As ksb said, I can feel the packs falling off slightly just before the lvc kicks, it is useless to go any lower as performance is just not there.

One other thing to consider, when the cells are dumping, if 1 cell has a little less mah in it, its value will drop off faster than the other. It could drop below 3.0, while the other cell is still at 3.4 since the lvc only reads the cumulative voltage of the pack. The lvc does not read individual cells.

If you set the lvc to 3.2, the cell that dumps first could drop to 2.9 or lower under load before the lvc kicks. When I started using my first lipo, I noticed that my pack was unbalanced by a good amount(with my sidewinder set to 3.2) at the end of a run. I bumped the lvc up to 3.5, and my packs are almost perfectly balanced when I first throw them on the charger right after a run. I dont want to feel that large drop off...
• 04-26-2013, 02:35 PM
ksb51rl
Good points, rag6. With the trend toward ever cheaper packs, you cannot expect manufacturers to closely match the cells that comprise them. As you noted, the cell voltages will diverge considerably more as the overall pack voltage drops. Another two reasons to set LVC @ around 3.4 to 3.5 volts per cell.
• 04-26-2013, 05:38 PM
Team arsy car
[QUOTE=Team arsy car;5487638]Only running Traxxas 2S batteries

Recently bought Hobby Wing SC8 ESC, factory set at 3V low voltage shutoff, however looking into it on the wonder WEB I see 3V is absolute minimum and recommendations ranging from 3.0V to 3.4V. Supplier says leave it at factory setting, any recommendations???

T.A.C[/QUOTE]

Wow guys, haven't been back to this post for a while and you guys have thrown some awesome info in here that has helped heaps, I set my ESC to 3.4v (maximum setting) and on 2S - 4000mah I saw a dramatically reduced run time, I switched to 3.2v and the run time was comparable to that of the VXL-3s. But keep in mind new motor/ESC combo, therefore the whole playing field has changed.
My conclusion is to reset to 3.4V to protect the packs, and if you want more run time, buy more batteries or bigger packs.

Thanks all, great info

T.A.C
• 04-27-2013, 09:43 AM
Jakey
[QUOTE=Team arsy car;5490457]Wow guys, haven't been back to this post for a while and you guys have thrown some awesome info in here that has helped heaps, I set my ESC to 3.4v (maximum setting) and on 2S - 4000mah I saw a dramatically reduced run time, I switched to 3.2v and the run time was comparable to that of the VXL-3s. But keep in mind new motor/ESC combo, therefore the whole playing field has changed.
My conclusion is to reset to 3.4V to protect the packs, and if you want more run time, buy more batteries or bigger packs.

Thanks all, great info

T.A.C[/QUOTE]
If you are seeing dramatic run time differences between LVC settings of 3.2 and 3.4 volts per cell, then your battery pack is being seriously over-taxed which results in a premature low voltage shut down.
• 04-29-2013, 06:02 PM
hopduperevo
i had the same exact esc and i set mine to 3.4
• 05-01-2013, 07:15 AM
Team arsy car
[QUOTE=hopduperevo;5492716]i had the same exact esc and i set mine to 3.4[/QUOTE]

That is exactly the conclusion I came too, now a new question??????
How do you know what amperage a motor is drawing if the manufacturer only fives you KV???
• 05-01-2013, 10:06 AM
Jimmie Neutron
With a watt meter or data logger.
• 05-02-2013, 01:18 AM
Team arsy car
[QUOTE=Jimmie Neutron;5493903]With a watt meter or data logger.[/QUOTE]

Hard soldered my wires, so could do but not that keen on ripping it apart for that test, or could just split loom in half and fit connectors.
Trying to work out what "c" rating batteries to buy???
120 to 750 amp ESC & 4000kv motor sold as combo, running 2s 5000mah batteries. So am I safe to assume that the motor would not be drawing anything greater then 120 amps constant?? if so does this formula sound right??

5000mah or (5amps X 25c) constant battery rating = 125A of constant draw
5000mah or (5amps X 50c) bust battery rating = 250A of burst draw

So if this is correct should I be looking at something like 50 to 100c batteries as the 25 to 50c I have may be on their limits??
• 05-02-2013, 09:43 AM
Jimmie Neutron
Finding an honestly rated 100C battery is going to be very difficult... I think the technology threshold is below that.

Keep in mind that you will not be pulling the max all the time. So if your ESC has a 120 constant and your pack has a 125 constant you should be fine.
• 05-02-2013, 06:49 PM
Team arsy car
[QUOTE=Jimmie Neutron;5494711]Finding an honestly rated 100C battery is going to be very difficult... I think the technology threshold is below that.

Keep in mind that you will not be pulling the max all the time. So if your ESC has a 120 constant and your pack has a 125 constant you should be fine.[/QUOTE]

Thanks, currently running 25c to 50c 4000mah and no problems, I have some 50c to 100c 5000mah on order and with the sums I did they should be well and truly good to go.

Would you expect to see the new batteries come out of the truck cooler??
• 05-02-2013, 09:09 PM
Jimmie Neutron
LiPo's do not perform at their peak until they are around 120°F.
• 05-03-2013, 12:29 AM
NvDesertRat96
very informative thread. Man i still have alot to learn. Ill be changing my LVC to 3.4-3.5

ARSY if i remember right you and i are running the same motor esc combo and i run 35c-70c 2s 5000mah and they work great and thanks for explaining the C rating related to ESC amp rating. I was using the Traxxas 5000mah battery and it didnt have the take off and i was told at the track to get a higher C rating, which now makes sense.
• 05-03-2013, 05:16 PM
Team arsy car
Yeah, the formula to work it out I found in the back alleys of the web, so not sure if it is right, that's why I threw it into this thread. 120 degrees Fahrenheit for peak performance is new, I haven't found that any where else, my 4000mah 25c to 50c batteries are spot on then as they run at that temp or slightly over. Oh well 4 x new 5000mah batteries are on the way, no one here wants to use my Nihm batteries any more.
• 05-03-2013, 07:49 PM
Jimmie Neutron
All of my NiMh power my kids Power Wheels...
[IMG]http://www.modifiedpowerwheels.com/forum/userstuff/papa/20071021131554_Aftershock1.jpg[/IMG]

If I get time this summer I will be putting a EVX2 ESC in them and twin Titans... the ESC will be controlled by a servo tester that is operated by the foot pedal.
• 05-04-2013, 05:50 PM
Team arsy car
Sweet wheels Jimmie, forget the twin titans, that thing needs some Mamba Power.
• 05-04-2013, 06:04 PM
Jimmie Neutron
The gear boxes won't hold up... I might go twin DeWALTS, but I doubt they will even hold up to that.