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Old 02-16-2012, 12:41 AM   #67 (permalink)
3dplane
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Quote:
Originally Posted by brucepick View Post



Separate is my plan. Heavy power lead from bat to starter and then to alt will be connected to existing original battery. Smaller lead that goes to fuse box and maybe elsewhere, will go to the LiFePO4 pack. So the whole rest of the car is powered by the Li pack. Both batteries will be grounded to chassis. That way the old lead battery will only be starting the car.

I'm not fully certain that within the alternator, there is no crossover of voltage/current between the two systems but I think/hope it is so. Hopefully the "system" voltage to the field coil windings and the voltage regulator do not cross over into alt's output.



Exactly, that's the plan. Except it's not switching off the alt that causes the car to be powered by the Li pack. It will be because the Li pack will be wired to the main system, and only the starter + alt will be connected to the lead acid battery.


I think as long as you keep the original battery,starter and the alternator's heavy positive circuit in their own separate loop and not allow a lead to go to your fuse box where it can share the positive with the lithium you should be good.

I'm thinking from the three phase windings out through the rectifier diodes,main output stud it SHOULD be really self isolating.( However who knows if they made some monitoring circuit within the regulator that ties in to one or more of the diodes etc.)
Now the voltage regulator might be sampling from the "fuse box" circuit and will try to control the alt based on that voltage (Li-pack) but other than that it should not be able to interfere in my opinion.
It will be interesting to see how things turn out!
Barna
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