Electric Outboard battereies

AntarcticPilot

AntarcticPilot

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Joined
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Location
Cambridge, UK
www.cooperandyau.co.uk
Has anyone got any suggestions or warnings about buying batteries for an electric outboard? I have recently purchased an electric outboard, and need to obtain batteries for the same.

Specification I have in mind is:

  1. About 50Ah, to give about an hour's operation per battery
  2. Sealed or Gel Cell construction
  3. Deep Cycle
  4. As LIGHT AS POSSIBLE
  5. Maximum weight 10-15 kg each.

Maplins seem to do a reasonable range, and I've seen what seem to be good bargains on sites dedicated to mobility scooters. But I may well be missing a trick, so it seems like an opportunity to probe the gathered wisdom of the forum!
 
AntarcticPilot said:
It is a Manta MX 54 (54 lb thrust). Previous owner states that he got plenty range on a 65Ah battery.
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He also said that the secret was using it on half-speed. If you look at this earlier post of his, he claims to have used an 85Ah battery, not a 65Ah (and to have paid £140 for the motor, not £200). So I'd be wary of claims.

An electric motor with 54lb thrust will use around 50A at max speed. Max speed isn't very high. If you're using it in tidal conditions, you'll need the max speed. A 50Ah battery won't last an hour at 50A - it will be flat much sooner. Just how soon depends on the type of battery. You need one with a low value for Peukert's exponent, and AGM batteries are pretty good in this respect.

So, probably your best route would be to buy a decent deep-cycle AGM battery which meets your weight criteria, then see how long it will run the motor for.
 
Dave_Seager said:
I run mine (Minn Kota Endura Pro 32) on an ordinary car battery of about 85Ah. It is probably not worth buying a special battery unless weight or size is an issue for you.
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I bought an electric outboard precisely because weight is an issue, and also to avoid having additional fuels on board. I am happy to carry two batteries - it is not total weight I am worried about, it is having conveniently manageable "lumps". While I can lift 20 kg I can't lower 20 kg vertically downwards into a dinghy from the deck (Capricious has a pretty high freeboard) and my wife, who is very petite, certainly can't.

I don't expect to use this outboard in strong tidal streams; if it can push the dinghy along at a few knots, that will be fine.
 
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