Quote:
Originally Posted by Fidd
142. Battery-heating after full charge?
This is surmise on my part. In theory, there'd be some form of battery protection that cracked in once you'd reached a little above 9.3Kah, in order to prevent over-charging, with the rate of recharge affecting how quickly this protection - howsoever arranged - came on.
This has implications for a current technique whereby when matching a convoy speed, the e-motor is put "on charge" and then the exact required rpm is maintained watching the e-motor shaft rpm gauge, and moderated using the e-motor speed controller.
So, either a battery temperature gauge, (with it tripping on reaching a max temp) or, the battery "tripping" a rate-dependant trip, would seem to me to be a worthwhile addition. The problem is, I don't know precisely how this aspect was actually handled. Perhaps Stosstrup or Decaf' could comment? The latter is my preferred solution, as it would allow the emotor moderated system for matching convoy speeds, but perhaps not for extended periods?
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Hi Fidd,
The charging of the batteries followed the same three phase principles by which lead acid batteries are charged even today. Charging began with a high voltage charge at a high level of current to deliver a high level of power (kW hours) to the cells, until the cell voltage reached roughly 2.4 V, or 149 V per bank. This is known as the so-called “gassing voltage”, above which electrolysis of water occurs and formation of hydrogen gas, high heat and the boiling off of the water in the electrolyte can occur in large amounts. And so at this point during the charge, the charging current is gradually tapered off (the “second phase”) while maintaining a bank voltage of 149 V, until the current has been reduced to roughly 400 or so amps, at which point the charge is then stopped.
The above are the steps for typical daily charging. Once a week and once a month, you would perform an equalization charge, taking the charge into a third phase (constant current at 400 A or so) much longer to boost the bank voltage up to roughly 170 V, which ensures that A) a good part of the lead sulfate that has formed on the electrodes gets converted back into sulfuric acid, and B) it helps distribute, or “equalize”, the sulfuric acid in the electrolyte throughout the individual cells. Consequence of this type of charging of course is that you do end up with gassing, and a boiling off of water in the electrolyte. And so monthly, the distilled water would need to be replenished. A necessary evil - if not done, you end up with lead sulfate that can’t be removed, shortening the life of the cells unnecessarily.
And so the charge was purely a function of monitoring voltmeters and ensuring the proper procedure was performed. And monthly, adding an inspection of cells to measure electrolyte density and replenishment of the distilled water in the electrolyte. There were no battery temperature gauges, or anything of that nature, and these were not needed as long as the proper procedure was followed (electrolyte temperature was indeed measured by hand during monthly maintenance).