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forums.rcpitstop.com  |  In The Pits  |  Battery talk  |  Battery problems wes
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Author Topic: Battery problems wes  (Read 2866 times)

Mavrick

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Battery problems wes
« on: October 24, 2005, 12:24:55 PM »
Hi wes its mark and i need help......ALL my lipo batteries that i bought are dead.....the latest victim was the new absolute power 2200ma i just bought.....one cell is dead its only reading 6.4volts.....the others use to be 3 cells each but there is only one good cell left now....

HELP!!!!......What is going on??


Offline Dr.Stupid

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Re: Battery problems wes
« Reply #1 on: October 24, 2005, 06:44:42 PM »
what is the cut off for your esc set at, you cant discharge Lipo batteries below 3 volts per cell, they don't like it. If your 3 cell packs drop below 9 volts during discharge and are left at this state the can croak. are the packs puffy at all? or did they get that low onder load?
There are no stupid questions, only that which remains unknown.

Mavrick

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Re: Battery problems wes
« Reply #2 on: October 24, 2005, 07:09:55 PM »
Ok i will check my ESC to see what it is set at.....and yes sometimes one cell is puffy.....what does that mean??

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Re: Battery problems wes
« Reply #3 on: October 24, 2005, 07:33:10 PM »
puffing cells is from charging at too high of a rate, or exceeding the limit of the cell discharge rate.


WARNING
Safety precautions for Lithium Polymer and NiCd cells/packs

1. Never fast-charge any battery type unattended.
2. Never charge LiPo cells/packs at any rate unattended.
3. Only charge LiPo cells/packs with a charger designed specifically for lithium polymer chemistry.
4. LiPo cells can ignite because of unmatched cell capacity or voltage, cell damage, charger failure, incorrect charger settings and other factors.
5. Always use the correct charging voltage. LiPo cells/packs may ignite if connected to a charger supplying more than 6 volts per cell.
6. Always assure the charger is working properly.
7. Always charge LiPo cells/packs where no harm can result, no matter what happens.
8. Never charge a cell/pack in a model. A hot pack may ignite wood, foam or plastic.
9. Never charge a cell/pack inside a motor vehicle, or in a vehicle’s engine compartment.
10. Never charge a cell/pack on a wooden workbench, or on any flammable material.
11. If a cell/pack is involved in a crash:

a. Remove the cell/pack from the model.
b. Carefully inspect the cell/pack for shorts in the wiring or connections. If in doubt, cut all wires from the cell/pack.
c. Disassemble the pack.
d. Inspect cells for dents, cracks and splits. Dispose of damaged cells (see below).

12. Dispose of cells/packs as follows:

a. Discharge: with the cell/pack in a safe area, connect a moderate resistance across the terminals until the cell/pack is discharged. CAUTION: cell/pack may be hot!
b. Discard:

- NiMH: place in regular trash.
- NiCd: recycle (cadmium is toxic).
- LiPo: puncture plastic envelope, immerse in salt water for several hours, place in regular trash.

13. Handle all cells/packs with care, as they can deliver high currents if shorted. Shorting by a ring, for example, will remove a finger.

14. Always store cells/packs in a secure location where they cannot be shorted or handled by children.

15. When constructing a pack, use only cells of the same capacity (mAh). During continued use of a pack, periodically check individual cells after discharge and before charging to verify cell voltages are within 0.1V of each other. If a pack has become unbalanced (i.e., cell voltages are more than 0.1V apart), restore balance by charging the cells individually to 4.2V before reconnecting as a pack.

There are no stupid questions, only that which remains unknown.

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Re: Battery problems wes
« Reply #4 on: October 24, 2005, 07:35:24 PM »
Lithium Polymer Charging, Handling, Safety Information
 
Charging:

Lithium Polymer batteries have specific charging requirements and ONLY chargers rated for Lithium Polymer cells may be used.  The best charger is one that requires the user to manually select cell count and charge rate for each pack of cells, then automatically check to see that the settings are correct.  The Apache SMART chargers work in this manner.  Chargers which use only automatic detection of cell count (and on that basis set charge voltage) are prone to error, and can damage cells or cause a fire due to over-voltage charging of cells.  We recommend that these chargers be set manually, if used. Other chargers are set manually, but do not include a safety circuit to oversee that setting.  These are prone to user error, and should also be checked very carefully to insure proper use.

For best results, a CC/CV charger, like the Apache SMART chargers, should be used. These charge initially at a constant 4.2V and constant 1C rate, then taper the charge rate as the battery nears full capacity.  Cells are about 90% charged in one hour, and can be left connected for another 20-30 minutes to complete the charge. The maximum permissible charge voltage per cell is 4.25V. The maximum charge rate for Lithium Polymer cells is 1C (ex: 0.7A for the ET-0700 cell). Please do not charge your lithium polymer at any rate higher than 1C.  Doing so may reduce the capacity and life cycle of the cells, with very little savings in charge time.

We believe that the Apache SMART Charger line is the safest charger on the market today.  In a recent test of the safety detection circuit they contain, more than 1000 improper combinations of battery and jumper settings were connected, and the chargers were 100% accurate in detecting these errors - emitting a warning tone and refusing to charge in each case.  Human error is much more likely than charger error, and the Apache oversight circuit is highly recommended insurance for that rare case when your attention might wander for a moment.

Charging Safety Tips

Lithium Polymer cells are a tremendous advance in battery technology for RC flight. However, due to the chemistry of lithium cells, there is a possibility of fire if charged improperly. It is unavoidable due to the nature of lithium itself. This is no different from many things we use in daily life which are inherently dangerous – knives, kitchen cleaners, automobiles, for a few examples – but which can be used very safely by adhering to simple rules and precautions.

 Be absolutely sure that the Lithium Polymer charger settings are correct for the battery pack being charged – both voltage and current settings 
 Care should be taken to charge on a fireproof surface, such as brick. 
 Do not charge batteries near flammable items or liquids 
 Keep a dry fire extinguisher nearby - or a large bucket of dry sand, which is a cheap and effective extinguisher. 
 Do not charge inside an automobile, especially while driving 
 Batteries should NEVER be left unattended while charging 

Handling Cautions:

New cells may have a high initial charge, and care must always be taken to insure that loose cells are not short circuited. Please:

 Do not put the loose cells in a pocket, bag, or drawer where they could short-circuit against other items, or the battery tabs could be pressed against each other. 
 Do not place the loose cells on any conductive surface, such as a metal-topped table. 
 Keep loose cells and battery packs WELL out of reach of children! 
 Buy pre-assembled packs from an authorized dealer, rather than assembling packs from loose cells 
 Take care that the cells are not punctured, especially by metallic objects like hobby knives. 
 If the electrolyte in the cells should get on your skin, thoroughly wash with soap and water. If in the eyes, rinse thoroughly with cool water. Immediately seek medical attention. 
 Electrolyte spills can be cleaned from models or workbench with methanol or detergent-water solution. 
 Although environmentally friendly, lithium polymer cells must be FULLY discharged before disposal.  Use a resistor setup (light bulbs, for example) to accomplish this, to avoid the possibility of a short-induced fire after disposal. 
 For long-term storage, charge fully, then discharge to 50%-60% of rated capacity. 
 
There are no stupid questions, only that which remains unknown.

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There are no stupid questions, only that which remains unknown.

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