lewis4x4

iTrader: (8)

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?

AreCee

iTrader: (1)

Bite the bullet and dispose of it.

RogerDaShrubber

iTrader: (6)

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.

UrabusDenis

Sir , I agree with you 100% ...

Topfuel99

iTrader: (1)

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

Infinite 12th

iTrader: (3)

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...

RogerDaShrubber

iTrader: (6)

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.

Infinite 12th

iTrader: (3)

Thanks now I know

CarbonJoe

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.

CarbonJoe

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.

ta04evah

iTrader: (2)

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.

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.

Chaz955i

iTrader: (5)

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.

RogerDaShrubber

iTrader: (6)

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.

ta04evah

iTrader: (2)

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.

RogerDaShrubber

iTrader: (6)

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.


+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.