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post #10 of (permalink) Old 12-16-2016, 06:00:AM
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Just starting on my Transit but a couple of comments from charging lithium in a Sprinter.
Lithium batteries could easily draw 2 to 3 times the battery size in current. So a 100AH battery could safely use 200 to 300A. Clearly something that would not happen in a Transit or Sprinter. The sprinter alternator cables are only AWG 2 so as the current goes up there is more voltage loss in the wire. At high currents the voltage out of the alternator also goes down. The max I have seen, in a sprinter with a 220A alternator, was 80A. (I use 00 cable to connect to the transfer switch.)
I would expect the same from the Transit. It has a 180A alternator but would only deliver less than 100A due to voltage loss in the wire and the alternator voltage going down to protect itself.
But, when near full charge with the charge current going down the charge voltage goes up. I see 14.2V on a Sprinter. The Transit should be close since this is about the correct voltage for a standard battery. In my system (solar and alternator) I used a switch to disconnect the alternator once near full charge, to keep from overcharging the lithium. My Transit build will automate that function.
In my experience there seems to be very little gain in capacity by charging lithium (Voltronix) past 14V.
The 14.9V, mentioned earlier in this string, should / would never be applied to the battery unless there was some sort of a failure.
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