James said: “We typically do not recommend 6 volt batteries because there is no way to manage them”
What do you mean by this exactly? Maybe you’re meaning something different than I’m hearing you say, but 6volt batteries in my estimation are easier to manage than 12v. Sure, you need more external battery interconnects, but when it comes to battery management, it matters little whether you’re managing it at the 6v or 12v level---either can be multi-stage charged and either can be given an equalization charge. For many years, the most common battery of choice in EV conversions (and golf carts) was the 6v golf cart battery---tried and true. There are battery balancers available for them and one can even make a simple diode/bulb passive bypass balancer. Until Hawker AGM, then lithium options appeared on the scene, many if not most EV conversion folks raced EVs used 6v batteries.
As for the safety of paralleling batteries, I don’t think even the pure lead batteries are technically safe. If paralleling lithium cells is considered patently unsafe, then there are a lot of TESLA, THINK and other cars on the road (a much more stressful dynamic environment than a boat) with paralleled cells & strings that are at high risk---didn’t the Tesla Roadster lithium pack actually consist of individual cylindrical lithium cells tack welded as a 12P config or so? It is a concern---I’m still nervous about my current arrangement of the 21kwh of Enerdel cells on my boat in a 7P(2P(12S2P)) 48v arrangement. The Enerdel batteries themselves are 12S2P. Ultimately soon I will have all the fusing in place that will at least ensure that if one of the 12S2P should short a cell, a local fuse will blow isolating the rest of the pack from high rate discharge into that battery string.
YMMV-
-MT
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com]
Sent: Tuesday, February 16, 2016 8:53 AM
To: electricboats@yahoogroups.com
Subject: Re: [Electric Boats] battery bank question
Hi Dominic,
Thanks for your inquiry. We typically do not recommend 6 volt batteries because there is no way to manage them. Over time, all batteries go our of balance and if this becomes significant it will ruin the battery bank and you would have to replace all of them at the same time.
We recommend Pure Lead Batteries. These batteries can be paralleled. We do not recommend any other type of battery to be paralleled for safety reasons.
Locating the batteries in different positions on the boat is no problem. You will want to run the positive and negative cables in the same bundle on the way to and from the remote battery to prevent any Electro Magnetic Interference with compasses etc aboard the boat.
The Electroprop Sailor is perfect for a Tartan 30C.
Let me know if I can be of any further assistance,
thanks,
James
James Lambden
The Electric Propeller Company
625C East Haley Street,
Santa Barbara, CA
93103
805 455 8444
james@electroprop.com
www.electroprop.com
On Feb 16, 2016, at 7:53 AM, philip.l.probert@gmail.com [electricboats] wrote:
I have a Tartan 30C that I'm converting to electric. I've removed the old A4 and am in the process of modifying the engine compartment for the the batteries. The problem is that, however I configure things, all of the batteries are not going to fit in this space. Right now, I have a plan to use 6V batteries for my 48V system but one or two batteries would need to be placed in a different location. The total distance (cable run) away would be about 50". With the proper size cable, is this acceptable? Thanks for any help.
Also, if anyone has any experience with a Tartan 30 electric conversion I'd love to know what prop you're using.....
Posted by: "Myles Twete" <matwete@comcast.net>
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