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post #29 of Old 02-08-2014
Maine Sail
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Re: Repowering with an electric engine?

Originally Posted by whippet99 View Post
Thanks Maine Sail

Good research and questions. I will try to get more info from vendors and those that have gone electric.

BTW, yes you are correct about 48V assumption.

Are you the famous Main Sail that did the great job on Stuffing Box maintenance photos? A cult hero in various forums
I don't know about the "famous" or "cult hero" but yes, same guy...

The only thing I can say to help you keep everyone around you honest in this endevour is to:

Trust Ohm's Law - Many here and elsewhere try to re-wire it, but as of yet no one has been successful.. For your use a useful calculation is below...

Convert Watts to Amps at fixed voltage:

Watts Volts = Amps

5000W 12V = 417A
5000W 48V = 104A

Never Forget Peukert - When dealing with high load applications such as e-boats one simply can not ignore Peukerts Law when dealing with lead acid batteries..

A 100Ah lead acid battery is only a 100Ah battery when used at and loaded at 5A at 80F, when new or just broken in.... Every other load & temp range either above or below the 20 hour rate at 80F results in CHANGES the batteries 20 hour rated Ah capacity! Cycle life and DOD also impact Ah capacity.. Anyone telling you otherwise is really not qualified to be doing so.

LiFePO4 cells have minimal Peukert's corrections but they are still not a Peukert of 1.0..... A 100Ah battery with a 1.0 Peukert would provide 100Ah at a 300A load and conversely 100Ah at a 0.5A load. This simply does not exist in the real world... The reality is that it might provide about 80Ah at 300A and 115Ah at 0.5A..

Do that with a flooded lead acid 100Ah battery:

100Ah Battery 300A Load = 33Ah
100Ah Battery 0.5A Load = 186Ah

-Maine Sail / CS-36T

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