DIY Electric Car Forums banner
1 - 4 of 4 Posts

·
Registered
Joined
·
1 Posts
Discussion Starter · #1 ·
Hi everybody, i am designing a theoretical system for an hybrid campervan, in this system i would have a 144v 10kw 18650 battery pack to power a pair of 15Kw motors, as the motors would work at an average consumption of 5Kw (assisting the combustion engine). Is it possible to inject power from a 12v source into the battery? Thank you in advance.
 

·
Registered
Joined
·
2,155 Posts
it is possible of course, but it is terrible. you are going to use a %65 efficient alternator on an idling engine (what %10 efficient idling) for a conversion efficiency of maybe %6.5, lets knock off another %20 for the 12-144v conversion, so %5 efficient?

so assuming 100 amp alternator, and that you meant 10kwH, it would take 10.5 hours to recharge fully. And it isn't "free", assuming 115,000 btu per gallon, it will take 6 gallons to recharge. and it might save you a gallon in the first hour of driving, and will also hurt your mileage if charging while driving.

just dump 5 gallons on the ground and save yourself the trouble.

edit, actually it is worse, I'm not taking charging/discharging and motor/controller losses into account, but you get the idea.
 

·
Registered
Joined
·
7,346 Posts
Charging a battery of any voltage from a source of any voltage is possible, but always involves loss of power due to conversion inefficiency. The real problem is that charging from 12V implies a desire to use the engine's conventional alternator as the electrical power source (the generator), and it's just not suitable for the task (as dcb explained).

The proposal sounds like a parallel hybrid: the engine drives the vehicle without using the electric system, and the electric motors can drive the vehicle, so the two drive systems are in parallel. Since this has not been expressed as a plug-in hybrid, I assume that all of the energy comes from the engine, so all of the energy in the battery comes from the engine (by driving a generator) - this is a "traditional" or "non-plug-in" hybrid design. In vehicles of this design, the same machine is normally used as the generator and as the drive motor (or one of the drive motors), because it is efficient and suitably sized for the task.

Where are the 15 kW motors planned to be? One per wheel of the axle which the engine drives? One per wheel of the opposite axle from the one the engine drives? One on each axle? This matters to whether or not you can efficiently use one or both of the motors as generators.
 
1 - 4 of 4 Posts
Top