Thanks for the good word! I wish you success on this if you go forward with a similar project.
Quote:
Originally Posted by cbaber
... Just to get things straight, are you going to add in the 40AH 12.8V LiFePO4 pack to the system separate from the main battery or in parallel?
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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.
Quote:
Originally Posted by cbaber
... When you switch the alt. off everything but the starter is still powered through the Lifepo4, right? So assuming the specs are accurate you could drive on good enough voltage for your whole trip without having to recharge the battery or use the alt. and then charge it overnight at home, right?
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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.
Quote:
Originally Posted by cbaber
... I am curious as to whether this method is better than just adding a second car battery in parallel? It seems like you can EOC for as long as you need to with that setup but can it last the entire trip without using the alt?
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Should be better. The 2nd battery in parallel does solve the problem of EOC running down the main battery voltage. But the alt does still have to ultimately recharge the batts, one way or another it is still providing the current I'm using, and that energy comes from my gasoline.
By hopefully running the whole car off the Li pack (except the starter), I can disable the alt electrically. That way the alt will present almost no mechanical load to the engine, and that's where I expect to gain some mpg. California98Civic has done it with a smaller single battery but he has a much shorter commute. Regardless of the size of the battery, you'd need to charge it when not driving, unless you can get a satellite to beam power down to you while under way.
Yes there is solar recharging but from what I've read you won't get power as fast as you'd need it to keep things charged up.