[转帖]Ni-MH battery

组别:中级工程师

2007-08-31 09:27 | 只看楼主

树型| 收藏| 小中大 1

Charge Characteristics

Proper charging of nickel-metal hydride cells is the key to satisfaction with their performance in any product. A successful charging scheme balances the need for quick, thorough charging with the need to minimize overcharging, a key factor in prolonging life. In addition a selected charging scheme should be economical and reliable in use.In general, the nickel-metal hydride cell appears to be more sensitive to charging conditions than the nickel-cadmium cell. It also has yet to develop the volume of operational data that guides design of nickel-cadmium chargers. For these reasons, charging strategies should be selected and charging parameters established in consultation with the cell manufacturer. One advantage today’s application designers do have in developing chargers for nickel-metal hydride cells is the increasing availability of packaged charger circuits.

08 31 2007 9:26AM

古今之成大事業、大學問者，必經過三種之境界： [color=ff0000] "昨夜西風凋碧樹。獨上高

组别:中级工程师

2007-08-31 09:27 | 只看楼主

树型| 收藏| 小中大 2

1. Charging Summary
The keys to successful charging of nickel-metal hydride cells are:
>Use a three-step charging strategy to speed return to service while minimizing excessive overcharge.
>Design for more subtle indications of entry into overcharge.
>Use redundant fast-charge termination techniques.
>Provide fail-safe charge-termination backup(thermal fuse, etc.).When these guidelines are followed, nickel-metal hydride cells can be quickly and reliably charged while maximizing cycle life.

08 31 2007 9:27AM

古今之成大事業、大學問者，必經過三種之境界： [color=ff0000] "昨夜西風凋碧樹。獨上高

组别:中级工程师

2007-08-31 09:28 | 只看楼主

树型| 收藏| 小中大 3

2. Cell Behavior During Charge
Unlike discharge performance where the behavior of nickel-metal hydride cells andtraditional nickel-cadmium cells is very similar, there are significant differences in behavior on charge between the two cell types that relate to basic electrochemical differences. Specifically nickel-cadmium cells are endothermic on charge while nickel-metal hydride cells are exothermic. This difference is manifested in the interrelationships among voltage, pressure, and temperature as discussed below.

08 31 2007 9:27AM

古今之成大事業、大學問者，必經過三種之境界： [color=ff0000] "昨夜西風凋碧樹。獨上高

组别:中级工程师

2007-08-31 09:29 | 只看楼主

树型| 收藏| 小中大 4

3. Voltage/Pressure/Temperature Interrelationships
Figure 17 sketches typical behavior of a nickel-metal hydride cell being charged at the C rate. These curves both indicate why charge control is important and illustrate some of the cell characteristics used to determine when charge control should be applied.The voltage spikes up on initial charging then continues to rise gradually through charging until full charge is achieved. Then as the cell reaches overcharge, the voltage peaks and then gradually trends down.Since the charge process is exothermic, heat is being released throughout charging giving a positive slop to the temperature curve. When the cell reaches overcharge where the bulk of the electrical energy input to the cell is converted to heat, the cell temperature increases dramatically.Cell pressure, which increases somewhat during the charge process, also rises dramatically in overcharge as greater quantities of gas are generated at the C rate than the cell can recombine. Without a safety vent, uncontrolled charging at this rate could result in physical damage to the cell.

08 31 2007 9:28AM

古今之成大事業、大學問者，必經過三種之境界： [color=ff0000] "昨夜西風凋碧樹。獨上高

℡Кāì¤ ( 离线 ) 组别:中级工程师	2007-08-31 09:31 \| 只看楼主树型\| 收藏\| 小中大 5 08 31 2007 9:31AM 古今之成大事業、大學問者，必經過三種之境界： [color=ff0000] "昨夜西風凋碧樹。獨上高

组别:中级工程师

2007-08-31 09:32 | 只看楼主

树型| 收藏| 小中大 6

4. Charge Acceptance at temperature
The effect of temperature on charging efficiency(the increase in cell capacity per unit of charge input)is one area of difference between nickel-metal hydride and nickel-cadmiumcells. Specifically charge acceptance in the nickel-metal hydride cell(as shown in Figure 18)decreases monotonically with rising temperature beginning below 20 Celsius and continuing through the upper limits of normal cell operation. This contrasts with the nickel-cadmium cell which has a peak in charge acceptance in the vicinity of room temperature. With either cell type, the drop in charge acceptance at higher temperatures remains a significant concern to product designers who are mounting the cells in close proximity to heat sources or in compartments withlimited cooling or ventilation.

08 31 2007 9:31AM

古今之成大事業、大學問者，必經過三種之境界： [color=ff0000] "昨夜西風凋碧樹。獨上高

℡Кāì¤ ( 离线 ) 组别:中级工程师	2007-08-31 09:32 \| 只看楼主树型\| 收藏\| 小中大 7 5. Rate Effect on Charge Acceptance Figure 19 indicates that the charge acceptance efficiency for the nickel-metal hydride cell is improved as the charging rate is increased. 08 31 2007 9:32AM 古今之成大事業、大學問者，必經過三種之境界： [color=ff0000] "昨夜西風凋碧樹。獨上高

℡Кāì¤ ( 离线 ) 组别:中级工程师	2007-08-31 09:33 \| 只看楼主树型\| 收藏\| 小中大 8 08 31 2007 9:32AM 古今之成大事業、大學問者，必經過三種之境界： [color=ff0000] "昨夜西風凋碧樹。獨上高

组别:中级工程师

2007-08-31 09:33 | 只看楼主

树型| 收藏| 小中大 9

6. Overcharge Detection
Determining when overcharge has occurred is critical to charging schemes that minimize the amount of time spent at high charge rates in overcharge. In turn, these efficient charging techniques are a key to maximizing cell life, as will be discussed later. Primary charge control schemes typically depend on sensing either the dramatic rise in cell temperature illustrated in Figure 20 or the peak in voltage show in Figure 21. Charge control based on temperature sensing is the most reliable approach to determining appropriate amounts of charge for the nickel-metal hydride cell. Temperature-based techniques are thus recommended over voltage-sensing control techniques for the primary charge control mechanism.

08 31 2007 9:33AM

古今之成大事業、大學問者，必經過三種之境界： [color=ff0000] "昨夜西風凋碧樹。獨上高

组别:中级工程师

2007-08-31 09:34 | 只看楼主

树型| 收藏| 小中大 10

7. Recommended Charging Rates
Today＇s trend to faster charge times requires higher charge rates than the 0.1 to 0.3C rates often ecommended for many nickel-cadmium charging systems. Both Figures 20 and 21 indicate that fast-charge rates serve to accentuate the slope changes used to trigger both the temperature and voltage-related charge terminations. A charge rate of 1C is recommended for restoring a discharge cell to full capacity. For charging schemes that then rely on a timed "topping"charge to ensure complete charge, a rate of 0.1C appears to balance adequate charge input with minimum adverse effects in overcharge. Finally a maintenance(or trickle)charge rate of 0.025C(C/40) is adequate to counter self-discharge and maintain cell capacity.

08 31 2007 9:34AM

古今之成大事業、大學問者，必經過三種之境界： [color=ff0000] "昨夜西風凋碧樹。獨上高

电池论坛电池技术交流镍镉电池/镍氢电池 [转帖]Ni-MH battery

[转帖]Ni-MH battery

[转帖]Ni-MH battery