danielsantos
Member
- Joined
- Oct 20, 2013
- Messages
- 15
My 2013 Leaf is down to 8 bars and I'll surely loose another come summer. Having recently sold my house, I finally have the money to either replace/upgrade batteries or buy a new car. I'm excited about the prospect of a 40kWh LiFePO₄ battery pack from EVs Enhanced, but it's not ready yet. Since I was already looking at 48V LiFePO₄ battery packs as a possible solution to my in-car 110V AC supply, I started thinking about larger adjunctive battery packs serving as an supplement to the main battery pack.
I do a fair amount of electrical engineering at my job as a firmware engineer, but I don't do a lot of power electronics and have never actually worked on high voltage circuits, so I'll have a lot to learn in this endeavour. This isn't a particularly efficient idea, because we'll need a current-limiting boost converter to match the voltage of the main battery pack, and then the car's inverter will chop it again with each conversion incurring an efficiency loss, but I believe the idea should work.
(I'll still need to work out how to make sure we don't accidentally charge the main battery pack -- this is an area I'm not that experienced with. But speaking naively, sticking a big fat diode on the main battery would only waste about 0.4% of the total power and dissipate 400W of heat in the very worst case.)
There will need to be a CAN bridge (with computer) in between the main battery pack and the system CAN bus. Adjunct battery pack(s) will need to report their current consumption/expenditure so that all current data can be aggregated and properly reported to the system CAN bus, leaving the rest of the system to see a single battery pack.
Has anybody worked on anything similar to this before? It would be nice to have a $1-2k USD way to reliably extend an old Leaf's range by at least a small amount. Perhaps it could even serve as the sole (if temporary) power source when having a battery pack rebuilt or such. If LiFePO₄ batteries indeed reach $56/kWh this year, then it should be possible to add 12kWh to the trunk (theoretically, 55L of the 679.6L of trunk space) for $672 + hardware, controller, some thermal management, boost converter, maybe a bit of crash safety hardware, etc.
Of course, I would still want to be able to draw from it for other uses (110 inverter, etc.).
I do a fair amount of electrical engineering at my job as a firmware engineer, but I don't do a lot of power electronics and have never actually worked on high voltage circuits, so I'll have a lot to learn in this endeavour. This isn't a particularly efficient idea, because we'll need a current-limiting boost converter to match the voltage of the main battery pack, and then the car's inverter will chop it again with each conversion incurring an efficiency loss, but I believe the idea should work.
(I'll still need to work out how to make sure we don't accidentally charge the main battery pack -- this is an area I'm not that experienced with. But speaking naively, sticking a big fat diode on the main battery would only waste about 0.4% of the total power and dissipate 400W of heat in the very worst case.)
There will need to be a CAN bridge (with computer) in between the main battery pack and the system CAN bus. Adjunct battery pack(s) will need to report their current consumption/expenditure so that all current data can be aggregated and properly reported to the system CAN bus, leaving the rest of the system to see a single battery pack.
Has anybody worked on anything similar to this before? It would be nice to have a $1-2k USD way to reliably extend an old Leaf's range by at least a small amount. Perhaps it could even serve as the sole (if temporary) power source when having a battery pack rebuilt or such. If LiFePO₄ batteries indeed reach $56/kWh this year, then it should be possible to add 12kWh to the trunk (theoretically, 55L of the 679.6L of trunk space) for $672 + hardware, controller, some thermal management, boost converter, maybe a bit of crash safety hardware, etc.
Of course, I would still want to be able to draw from it for other uses (110 inverter, etc.).