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Honda is using a Li-ion battery (12V, 4.5Ah, 80 CCA) for their premium vehicles like Honda CBR1000RR Fireblade SP and Honda CBR1000RR Fireblade SP2.

  • Fun fact - my collegues started regular car engine using LiPo batteries from airsoft guns. They connected them together creating 14V package. Not safe but that was their only way out ;) – Mark Mar 21 '17 at 10:02
  • CCA is what matters – agent provocateur Mar 22 '17 at 19:40
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The capacity (indicated in Ah) isn't that important. A battery's ability to start a car is indicated as CCA (cold cranking Ampere), i.e. the maximum current a battery can supply for 30 seconds.

A 1 kW starter motor (pretty big for a bike engine) draws 80 A, that times 30 seconds is only 0.7 Ah. So a 4.5 Ah battery can start the bike several times. These motorbike battteries have CCA values in the region of 80-150.

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Then yes, but not for long... due to the small capacity. How - with a starter designed to match the load and gearing.

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    I suspect the capacity is plenty, assuming the charging system works properly. So it doesn't matter if it can't run the starer for a minute or so continuously. It is enough to just start the engine once, after which the charging system takes over to ensure next start will be successful as well. – juhist Mar 21 '17 at 13:18
  • @juhist That philosophy is fine when the engine always starts first or second time. But when the battery is low because you have left the lights on and you've run out of fuel etc and it is not happy starting it can be a different story. – Solar Mike Mar 22 '17 at 15:12
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Yes, it is perfectly useful for starting a 1000cc engine. For example, consider the Omega Mechanix IJS-6000D jump start kit: https://www.amazon.co.uk/Omega-Mechanix-IJS6000D-Intelligent-Charger/dp/B00YWU4RM6

It is only 6000 mAh = 6 Ah. It can start a gasoline engine up to 5 liters in size.

So, if you scale this down, 4.5 Ah battery should be able to start 3750cc engine. Your tiny 1000cc engine is nowhere close to this.

The reason the batteries are typically larger than this is that you cannot run the electrical loads such as lights with the engine turned off for any useful length of time using such small batteries. Also, batteries degrade as they age, so even if a 6 Ah battery will start a 5000cc engine when new, it may have difficulty doing that for ten years multiple times per day. But considering that 4.5 Ah will start 3750cc engine, and that the engine is only 1000cc in size, there is a huge safety margin that will ensure the system will continue to work even as the battery degrades.

  • Batteries don't scale like that. The crucial data is the amount of current the battery can deliver (the CCA rating), see my answer. If I put 8 D cells in series, I've got a battery that can deliver 4.5 Ah at 12V. But it won't be able to start a motorbike, much less a 3.7 litre engine. – Hobbes Mar 21 '17 at 14:57
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    @Hobbes True, but D cells are not starter batteries. Alkaline batteries are awful at supplying high currents. If you have 6 Ah starter battery that can start 5000cc engine, a 4.5 Ah starter battery using the same technology should be able to start a 3750cc engine. The scaling is linear, assuming technology is the same. – juhist Mar 21 '17 at 19:40
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    Fair enough, but that still means specifying a battery' capacity is not enough to know if it can start a vehicle. You'll also have to know details about its internal construction. Or you can do it the easy way and specify the CCA rating. – Hobbes Mar 22 '17 at 16:21

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