Electric Starting Without a Battery

Electrical and electronic topics for small boats
jimh
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Electric Starting Without a Battery

Postby jimh » Thu Feb 16, 2017 11:09 am

With an emphasis on the "small" in SMALL BOAT ELECTRICAL, I want to mention a new technology that has been introduced by Bombardier Recreational Products (BRP)--not in their EVINRUDE line of outboard engines but in their SKI-DOO line of snow-mobiles (or snow sleds or snow machines, as they are variously called, depending on where you live).

SKI-DOO calls this new technology their SHOT STARTER. It allows a smaller engine, typically about 850-cc displacement, to be started with an electric starter motor without using a conventional lead-acid storage battery as the source of the electrical energy. The electrical energy is provided by an ultra-capacitor--an assembly of many conventional electrolytic capacitors in parallel to create a very large capacitor that can store a considerable amount of electrical energy. The electrical energy that is stored on the ultra-capacitor is generated by the engine when it was last running. To start the engine when it has not been running for more than about an hour, a conventional pull start method is used. Attempting to start with the ultra-capacitor drains all the energy from it, so the engine has to run for a while to replace that lost charge, before it can be electrically re-started again. But if making frequent starts and stops, the engine can be re-started electrically, reliving the rider of having to pull start the engine. Several additional technologies are employed to make this possible.

The electric starter motor on the SKI-DOO is not a convention electric motor; the motor is actually the permanent magnet alternator (PMA), working in reverse as a motor. This saves the weight of a separate starter motor. I suspect that the PMA starter motor might operate at a higher voltage than 12-Volts, which would also be efficient as it would allow the ultra-capacitor to store more energy at the higher voltage.

Probably the more important related technology for enabling the SHOT STARTER is the engine: it's an E-TEC derivative engine, using direct fuel injection, and, like the E-TEC outboard, able to be started without needing any battery power. But most importantly, the engine can start with very little mechanical rotation. The SKI-DOO engine is said to be able to start in as little as one-third of a revolution of the crankshaft. This is likely very important because the ultra-capacitor won't have enough electrical energy storage to crank the engine over for very long.

Whether this technology will be attractive to boaters remains to be seen. On the snow sleds there appears to be quite an incentive to save weight, and elimination of a small lead-acid storage battery that might weight 25-lbs and perhaps 5 to 10-lbs of starter motor must be seen as having a direct benefit to performance. In boats, even in small boats, I am not so sure that losing 25-lbs in battery weight is at the top of the list. A lot of boaters I know could lose 25-lbs themselves if they wanted to improve their boat's performance. Also, I think the total weight of a snow sled is probably much lower than the total weight of most boats, even small boats that might have a small outboard. That makes the weight saving less significant.

As is typical for products from BRP, there is a highly informative and beautifully produced promotional presentation that describes the SHOT STARTER technology. See it at

http://www.ski-doo.com/technologies/e-tec-shot-starter.html

I don't know if this technology will become useful on boats, but at least one aspect of it could easily be transitioned to outboard engines. The combination of the PMA and a starter motor into one device could be something we'll see. However, as I mentioned, I think part of that technology might be use of higher voltage, which would then require using more than 12-Volts as the storage battery. That would not lead to widespread adoption, as boats--like cars--seem to be forever tied to 12-Volt power.

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Don McIntyre - MI
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Re: Electric Starting Without a Battery

Postby Don McIntyre - MI » Fri Feb 17, 2017 9:28 am

Interesting about the starter motor acting as a charging device; they've taken a page from the turbine installations in light rotary wing aircraft. Switch to starter to wind up the turbine to the ignition point, then switch to generator to provide power.

Regards - Don