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NiMH or NiCd?
I once heard that NiMH batteries get hot when charging, but NiCd batteries actually get colder while charging
Quote from: airman00 on April 30, 2009, 09:08:16 PMI once heard that NiMH batteries get hot when charging, but NiCd batteries actually get colder while chargingwow, who would of thought?
Hi,Both NiMH and NiCd heats up when charged.NiCd can supply a much higher current (relative to its capacity). NiMH packs a much higher capacity per cubic measure, but still the NiCds can provide higher surge currents.However, a circuit only draws what current it needs, so unless it was current starved on NiMH, this has no chance in a Hot Place of being the problem.It would be helpfull for most people building robots, to really know their battery technology inside out; how they're charged, the pros and cons of each chemistry etc. as it is what drives your robots in every way - a bad match between battery and load means you're loosing out on something that would be cheap to maximize.
Ahem ahem.....The safe temperature range for a NiCd battery in use is between −20°C and 45°C.
During charging, the battery temperature typically stays low, around 0°C (the charging reaction absorbs heat), but as the battery nears full charge the temperature will rise to 45–50°C.
Some battery chargers detect this temperature increase to cut off charging and prevent over-charging.
The NiCd was only in for 1 sec, so 6V at 1700 mAh = (1700/60) /60 = ~.5 A in 1 sec.The NiMH at 6V 1400 mAh would only be about .3 A in 1 sec...
So as happens with almost every chemistry the battery internal resistance to charging raises when battery gains more and more charge....
I didn't say the when charging a NiCd you better get some of your beers around to freeze...
And hey.... please don't play around with only some of my phrases.... it's kinda irritating.......... really.....
hah,why does this always seems to happen between you guys?
I'm not really sure what you mean here?You're not talking about Ri (Internal Resistance) of the battery, are you? Because that goes down when the battery charges.
Nah, I prefer Whiskey myself
Quote from: SmAsH on May 02, 2009, 04:06:03 PMhah,why does this always seems to happen between you guys? It's in a friendly manner so you don't need to worry.... Arguments exist for the shake of humanity...
Power * time interval (in seconds) = energy required