R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Electric On-Road

Reply
 
Thread Tools Search this Thread
Old 09-19-2011, 04:54 PM   #16
Tech Fanatic
 
lewis4x4's Avatar
 
Join Date: Jul 2011
Posts: 756
Trader Rating: 8 (100%+)
Default

One of my batteries when I go to charge (2s), gives me an error and says to check the voltage. It got too low... Not sure how when my ESC has a shutoff but it did.... What do I do now?
lewis4x4 is offline   Reply With Quote
Old 09-19-2011, 05:27 PM   #17
Tech Elite
 
Join Date: May 2003
Location: Northern & Central Illinois
Posts: 4,337
Trader Rating: 1 (100%+)
Default

Quote:
Originally Posted by lewis4x4 View Post
One of my batteries when I go to charge (2s), gives me an error and says to check the voltage. It got too low... Not sure how when my ESC has a shutoff but it did.... What do I do now?
Bite the bullet and dispose of it.
AreCee is offline   Reply With Quote
Old 09-19-2011, 06:58 PM   #18
Suspended
 
Join Date: Jun 2011
Location: Brisbane
Posts: 1,696
Trader Rating: 6 (100%+)
Default

Quote:
Originally Posted by Infinite 12th View Post
Thank you I'll look for that 3rd hole and watch someone do the balance thing

And I've just decided I will help promote 12th at my local track by getting a RC125.1 in the next month. I was allowed to race someone's TC in 17.5 and I'm sure I would have fun in the that class but I will race TC later

Hopefully I can generate some enthusiasm for an great old class

This means i can get just one revtech lipo to use for whole day...lol



What is the difference between the 60c and 28c like on this page

http://www.google.com/search?rlz=1C1...iw=818&bih=461

Not sure what amps to charge it yet or how long it takes?



lol...I had no idea they are potential time bombs

So it is an charge thing not an discharge thing







Thanks

I didn't know that I could get blown up or hurt with batteries ...lol
Yeah Lithium metal has a tendency to want to turn into Hydrogen gas when put in water, or in the case of LIPO batteries, when Lithium and the solvents used in manufacture are exposed to heat.

Over is the problem, Over Discharge and Over Recharge cause dendrites to grow within the lithium polymer layer of the cell, these can cause small punctures between layers of the cell which lead to short circuits, this gives you the three things needed for an explosion or fire, Lithium in metal form, flammable solvents and heat from a short in the presence of Oxygen equals fire or explosion if enough Lithium has degraded to Hydrogen.
RogerDaShrubber is offline   Reply With Quote
Old 09-19-2011, 11:43 PM   #19
Tech Fanatic
 
UrabusDenis's Avatar
 
Join Date: Nov 2009
Location: Croatia
Posts: 790
Default

Quote:
Originally Posted by RogerDaShrubber View Post
This is utter rubbish. And remind me never to pit next to you guys as you charge your time bombs. The reason why you balance charge is to stop OVER CHARGING. When you over charge a cell, Lithium ion convert back to lithium metal which is a highly reactive species and likes to go BOOM like all alkaline metals.

Thankfully, here in Australia there are rules that control the charging of lipos at all events, charge rate of 1C and must be balanced charged using a lipo charger in lipo mode.
Sir , I agree with you 100% ...
UrabusDenis is offline   Reply With Quote
Old 09-20-2011, 04:10 PM   #20
Tech Apprentice
 
Topfuel99's Avatar
 
Join Date: Sep 2011
Posts: 80
Trader Rating: 1 (100%+)
Default Why use Lipo

Consider the need for special chargers, charging bags, delicate handling etc etc. Why are Lipo batteries used so much. Seems like the danger is pretty high based on reading the attached document mentioned above.

Or is that just the manufactures covering their rear-ends. I guess I'm wondering why they seem to be so popular when they seem so inherently dangerous.

Thanks for the enlightenment
Topfuel99 is offline   Reply With Quote
Old 09-20-2011, 04:14 PM   #21
Tech Fanatic
 
Infinite 12th's Avatar
 
Join Date: Aug 2011
Location: California
Posts: 877
Trader Rating: 3 (100%+)
Default

Quote:
Originally Posted by Topfuel99 View Post
Consider the need for special chargers, charging bags, delicate handling etc etc. Why are Lipo batteries used so much. Seems like the danger is pretty high based on reading the attached document mentioned above.

Or is that just the manufactures covering their rear-ends. I guess I'm wondering why they seem to be so popular when they seem so inherently dangerous.

Thanks for the enlightenment
Lightness
High capacity
No memory
Longevity?

@Everyone

What is the "c" part of 28c, 60c, 65c mean...lol

How is that important for purchasing batteries and usage, performance, etc...
Infinite 12th is offline   Reply With Quote
Old 09-20-2011, 04:42 PM   #22
Suspended
 
Join Date: Jun 2011
Location: Brisbane
Posts: 1,696
Trader Rating: 6 (100%+)
Default

C rating refers to the discharge rate of the pack. If you have a battery that is 5000mha and 20C, you can do a little basic math and 5 * 20 = 100Amps. So once you know that information and have worked out what the current draw of your motor/esc us, you can then make sure you have a pack that is sutable.

If your motor draws 120A then the above 5000mha 20C pack would not be able to deliver the current it requires and thus would underperform and cause the battery to OVER discharge (deliver more current than it is designed to) and this can lead to pack damage and fires.

Also, by not running a pack at its max discharge, you can get more life out of the pack, so if you have a motor that uses 100A, using a battery that can deliver 150A is going to give more cycles out of the battery because you have less cell degeneration.

Simply, for TC you want the biggest mha and biggest C discharge rating you can get, 6000mha 60C and you cannot go wrong.
RogerDaShrubber is offline   Reply With Quote
Old 09-20-2011, 04:59 PM   #23
Tech Fanatic
 
Infinite 12th's Avatar
 
Join Date: Aug 2011
Location: California
Posts: 877
Trader Rating: 3 (100%+)
Default

Quote:
Originally Posted by RogerDaShrubber View Post
C rating refers to the discharge rate of the pack. If you have a battery that is 5000mha and 20C, you can do a little basic math and 5 * 20 = 100Amps. So once you know that information and have worked out what the current draw of your motor/esc us, you can then make sure you have a pack that is sutable.

If your motor draws 120A then the above 5000mha 20C pack would not be able to deliver the current it requires and thus would underperform and cause the battery to OVER discharge (deliver more current than it is designed to) and this can lead to pack damage and fires.

Also, by not running a pack at its max discharge, you can get more life out of the pack, so if you have a motor that uses 100A, using a battery that can deliver 150A is going to give more cycles out of the battery because you have less cell degeneration.

Simply, for TC you want the biggest mha and biggest C discharge rating you can get, 6000mha 60C and you cannot go wrong.
Thanks now I know
Infinite 12th is offline   Reply With Quote
Old 09-21-2011, 04:59 AM   #24
Regional Moderator
 
CarbonJoe's Avatar
 
Join Date: Jul 2006
Posts: 2,661
Default

In general, the "C" rating printed on the battery label is the continuous discharge current rating. The "burst" current (rated for something like 10 seconds or so) is usually 2x the continuous C rating.

From the example given above (5000 mAh 20C) the continuous current rating is 100A, and the burst current rating is 200A. Your motor draws the most current right at a dead start, and drops off considerably the higher the RPM. For example, according to a Novak data logger, a 17.5 motor might peak at 60A draw, but the average current draw is around 20A for the entire 6 minute race.

The "stock" motor classes seem to do better with a lower C rating pack (the theory is that the current draw makes the pack heat up, generating more voltage). I believe that at Vegas last year, the stock class was won with a 28C rated pack.
__________________
*** The Gate - Celebrating 8 years at the same location ***
The difference between genius and stupidity is that genius has its limits. - Albert Einstein
Understeer is when you hit the wall with the front of the car and oversteer is when you hit the wall with the rear of the car
CarbonJoe is offline   Reply With Quote
Old 09-21-2011, 05:04 AM   #25
Regional Moderator
 
CarbonJoe's Avatar
 
Join Date: Jul 2006
Posts: 2,661
Default

Quote:
Originally Posted by RogerDaShrubber View Post
Thankfully, here in Australia there are rules that control the charging of lipos at all events, charge rate of 1C and must be balanced charged using a lipo charger in lipo mode.
What do the Aussie rules say about 1s LiPo packs, since the vast majority don't have a balance port? There certainly must be some vendors packs that are 1s2p construction. Just curious.
__________________
*** The Gate - Celebrating 8 years at the same location ***
The difference between genius and stupidity is that genius has its limits. - Albert Einstein
Understeer is when you hit the wall with the front of the car and oversteer is when you hit the wall with the rear of the car
CarbonJoe is offline   Reply With Quote
Old 09-21-2011, 05:54 AM   #26
Tech Elite
 
ta04evah's Avatar
 
Join Date: Oct 2010
Location: Sydney, Australia
Posts: 2,614
Trader Rating: 2 (100%+)
Default

Quote:
Originally Posted by RogerDaShrubber View Post
Thankfully, here in Australia there are rules that control the charging of lipos at all events, charge rate of 1C and must be balanced charged using a lipo charger in lipo mode.
Actually this is not entirely true, the 1C charge rate is enforced for Off Road.

Quote:
Originally Posted by AARCMCC Off road rules
12.3.4 Li-Poly battery maximum charge rate shall be according to manufacturers specifications. Where no
manufacturers specifications exist, a 1C (C= charge amp rate) is to be used. Charge amp rate = mAh
capacity/1000=X Amps. Overcharging is not allowed.
http://www.aarcmcc.org/docs/AARCMCC%...2020110116.pdf

For on road the rules "recommend" 1C charge rates.

Quote:
Originally Posted by AARCMCC On road rules
11.3.3 Lipo capable chargers are only to be used; it is recommended that Lipo batteries are charged at a
maximum charge rate of 1C. 1C charge amp rate = mAh capacity/1000
http://www.aarcmcc.org/docs/AARCMCC%...s%20201108.pdf

Charging in a fire safe Lipo sack is enforced for on & off road and is an inexpensive insurance against damage or injuries from a lipo battery fire or explosion.

p.s. The above quoted rules and links are for Australian AARCMCC sanctioned events within Australia.
Check with your local track & governing body rules within your country.

Cheers
Rob.
__________________
Castle Hill RC On Road Facebook https://www.facebook.com/groups/121817254587521/
FatBear RC Videos https://www.youtube.com/channel/UCjiAhwa-rk5Vas2rv5IBD4A
ta04evah is offline   Reply With Quote
Old 09-21-2011, 06:20 AM   #27
Tech Master
 
Chaz955i's Avatar
 
Join Date: May 2009
Location: NE Ohio
Posts: 1,022
Trader Rating: 5 (100%+)
Default

Quote:
Originally Posted by Topfuel99 View Post
Consider the need for special chargers, charging bags, delicate handling etc etc. Why are Lipo batteries used so much. Seems like the danger is pretty high based on reading the attached document mentioned above.

Or is that just the manufactures covering their rear-ends. I guess I'm wondering why they seem to be so popular when they seem so inherently dangerous.

Thanks for the enlightenment
They aren't dangerous when used within their design criteria. This isn't different from any other battery. Phones, laptops and many other consumer goods use Lipo technology. If these things were exploding (which seems to be another myth) left and right and burning houses down do you think any company in their right mind would continue to sell them? Their legal team would have a melt down from the class actions. From the physical abuse I have seen these batteries take in a racing environment I would argue they are actually more robust than most give them credit and the dangers are overstated.
__________________
At The Gate Bizzos
Chaz955i is offline   Reply With Quote
Old 09-21-2011, 03:31 PM   #28
Suspended
 
Join Date: Jun 2011
Location: Brisbane
Posts: 1,696
Trader Rating: 6 (100%+)
Default

Quote:
Originally Posted by ta04evah View Post
Actually this is not entirely true, the 1C charge rate is enforced for Off Road.


http://www.aarcmcc.org/docs/AARCMCC%...2020110116.pdf

For on road the rules "recommend" 1C charge rates.


Cheers
Rob.
Ok i should have been a little more specific then, ORRCA QLD rules state:

Quote:
2.3 Lithium Polymer Battery
7.4v (2 (3.7 volt) cells only)
No modifications allowed to the case and/or the battery
Any physical distortion, denting, puncturing or damage to the hard case of
the Li-Po battery will deem the Li-Po battery to be ineligible for use at ORRCA QLD events.
Overcharging is not allowed (voltage higher than 8.4v)
Must charge in Li-Po sack or other device (fire mitigation device able to withstand
and contain a destructive failure without showing a flame).
Must be used with electronic speed control that has either a inbuilt cut-off
or used with an external cut-off device installed (6 volts minimum).
Must be charged using a Li-Po capable charger only at a maximum rate of 1C.
EP Interclub and state titles all fall under ORRCA rules here.
RogerDaShrubber is offline   Reply With Quote
Old 09-21-2011, 08:41 PM   #29
Tech Elite
 
ta04evah's Avatar
 
Join Date: Oct 2010
Location: Sydney, Australia
Posts: 2,614
Trader Rating: 2 (100%+)
Default

Quote:
Originally Posted by RogerDaShrubber View Post
Ok i should have been a little more specific then, ORRCA QLD rules state: EP Interclub and state titles all fall under ORRCA rules here.
No probs, I wasn't aware of your location in Oz

And as long as a little bit of common sense is applied to the known safety procedures the lipo batteries should give you good performance for a extended period of time.

Some key safety points to remember in the charging, discharging and storage of your lipo batteries.

*Use a proper Lipo charger and never a charger not designed for Lipo batteries
*Charge the battery in a fire & explosion containing safety bag
*Never leave the charger unattended, there is no such thing as "set & forget"
*Take care to never short or connect the battery in reverse polarity
*Use a charger or compatible device to discharge the batteries, never use resistors or light bulbs without a voltage cut off device
*Use a esc with a low voltage cut off safety feature, if the esc is not fitted with one use a separate cut off or alarm device
*Avoid leaving lipo batteries in a fully charged state for longer then 1-2 days
*Store lipo batteries in a fire/explosion containing bag at home.
*Regularly inspect your batteries for any form of distortion, cracking or puffing of the hard outer shell, if any occurs remove the battery and place in an area away from any flammable materials
*When disposing of lipo batteries contact your local government services to find an appropriate waste facility to dispose the battery

Cheers
Rob.
__________________
Castle Hill RC On Road Facebook https://www.facebook.com/groups/121817254587521/
FatBear RC Videos https://www.youtube.com/channel/UCjiAhwa-rk5Vas2rv5IBD4A
ta04evah is offline   Reply With Quote
Old 09-21-2011, 10:06 PM   #30
Suspended
 
Join Date: Jun 2011
Location: Brisbane
Posts: 1,696
Trader Rating: 6 (100%+)
Default

Quote:
Originally Posted by ta04evah View Post
And as long as a little bit of common sense is applied to the known safety procedures the lipo batteries should give you good performance for a extended period of time
This is true, a little common sense goes a long way here, lipo are as safe as any other battery out there, but, they require a little more precaution on the part of the user to keep them that way.


Quote:
Originally Posted by ta04evah View Post
Some key safety points to remember in the charging, discharging and storage of your lipo batteries.

*Use a proper Lipo charger and never a charger not designed for Lipo batteries
*Charge the battery in a fire & explosion containing safety bag
*Never leave the charger unattended, there is no such thing as "set & forget"
*Take care to never short or connect the battery in reverse polarity
*Use a charger or compatible device to discharge the batteries, never use resistors or light bulbs without a voltage cut off device
*Use a esc with a low voltage cut off safety feature, if the esc is not fitted with one use a separate cut off or alarm device
*Avoid leaving lipo batteries in a fully charged state for longer then 1-2 days
*Store lipo batteries in a fire/explosion containing bag at home.
*Regularly inspect your batteries for any form of distortion, cracking or puffing of the hard outer shell, if any occurs remove the battery and place in an area away from any flammable materials
*When disposing of lipo batteries contact your local government services to find an appropriate waste facility to dispose the battery
+1 this is good quality and sound advice on lipo usage.

And with the AARCMCC rules, personally i don't think there is any real reason or argument to justify charging at a rate higher than 1C, its not like anyone is turning up to a meet with only 1 battery in the kit, or that the cost of batteries is so exponentially high that one cannot afford to have more than 1 battery in the kit either. That said, i have no issue with someone charging at 5C if that is what the manufacturer has specified as a safe limit for that pack, if the only reason to do so is due to time constraints between heats, but even that would be a push, with a 4 port charger and 4 batteries and 1 hour charge time at 1C, you have a fresh pack coming off the cooker every 15 mins. More than enough for even the most demanding of heat schedules. And that is assuming that you run the pack to max discharge during a heat, which most often than not, is not the case and charge times is much lower than 1 hour.

Last edited by RogerDaShrubber; 09-21-2011 at 10:23 PM.
RogerDaShrubber is offline   Reply With Quote
Reply



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 06:49 AM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net