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• On the back of a pack of fags..

  tim.addison • 08/14/2015 at 04:04 • 0 comments

  So I worked out the power numbers; to be able to endure a multi day transit you need to know how much power to bring. I'm planning on using a trolling motor in phase 2+ so I started with the MinnKota website. It states the max current draw for a motor with 33lbs is 30 Amps at 12 V.

  Today in BC the day / night split is roughly 14 hr/ 10hr. So over night you'll be need 3600 watt hours of power. Converted to joules that's 12.96 MJ. The wiki battery chemistry page will tell you battery power density in MJ/kg for various battery chemistries.

  So if I go for lead acid I'd need 92.6 kg of batteries, oh my! damn thing will never float.

  NiMH is considerably better, only 36 kg

  Lithium Ion is best (and most expensive) at 28 kg.

  I did some thinking and found this video of a 55lbs motor current draw. At power setting 4 he's pulling about 16 amps which would be a safe bet, you wouldn't run at full throttle all the time. That cuts down the batteries considerably.
  

  I've been reading up on various chemistries, NiMH looked promising. Toyota uses NIMH in the Prius but further research shows NiHM is a pain to charge.

  Tesla uses Lithium Ion and apparently they are a little more forgiving to charge.. LiFePO might be the trick, it's the chemistry that A123 is using and happens to be available on Alibaba in 10 and 20 Ahr packs. More tolerant to over changing too. Battery University has tonnes of info.

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