[PSUBS-MAILIST] Elco Motors

Tue Apr 22 16:58:48 EDT 2014

Hi Chris,  The problem is the BMS.  They draw off current to charge up and balance the other cells.  When you buy a battery of the cells such as a 12 volt assembly they have about between 4-8 of these BMS boards in them so they are a mess of wires under the cover.  IF they were hooked up to a solar cell charger they might be OK.  Also if you unhook the BMS inside then they should last longer but even doing this you get some cell failures.  You need to hook them up to a computer with a program you can download and then you can see what is happening at cell level.  There are a number of brands and there is a supplier in UK who has a MK 4 BMS version which he sells to the military with a high success rate.  It is a study in itself to get into the do’s and don’ts.  Leave the fancy stuff alone unless you have deep pockets and are a techo.  Thundersky do a simple one that is used by a lot of EV enthusiasts.  Here is an excerpt from a blog 

I have a pack of Thundersky 160ah 40 pieces to give about 128v nominal. 
The've got about 6300+ miles on them now in pretty harsh swedish environment. Last winter I did some close to 2C runs in -28degC and this winter I have run the car in -27degC. I run it every day.
I had one cell go busbar on me, but other then that they work fine.

They DO NOT LIKE the cold here, below freezing is not that fun.
I had a Endless BMS, but I run BMS free now. No LVC/HVC just pack voltage. I have probably overcharged them before I got the charger to work properly. And I can see big differences in Ri. Probably from overcharge. I did not have the cellog when I started using the pack.
Over all really happy. 
Enough to plan a second pack for another car.
I never draw abowe 2C from the pack.

Regards,  Hugh   

From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of Christopher Graca via Personal_Submersibles
Sent: Wednesday, 23 April 2014 8:32 a.m.
To: Personal Submersibles General Discussion
Subject: Re: [PSUBS-MAILIST] Elco Motors

Ken,

do the LiFePO4's have the same problems if they are stored at a lower voltage, and then just recharged while re-balancing the individual cell voltages prior to use?

-Chris

On Tue, Apr 22, 2014 at 3:23 PM, Hugh Fulton via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Ken,  I have had a lot of expense with LiFePO4’s.  Battery management system BMS is critical and they do not like sitting unused.  OK on a daily use vehicle but as they are made in China the individual cell quality is dubious and they need to be matched.  It has cost me a lot and I am not in the water.  Chs  Hugh

From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of Ken Martindale via Personal_Submersibles
Sent: Wednesday, 23 April 2014 1:51 a.m.
To: 'Personal Submersibles General Discussion'

Subject: Re: [PSUBS-MAILIST] Elco Motors

Be nice to use the LiFePo4 batteries for the Sub batteries.

Ken Martindale

From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of via Personal_Submersibles
Sent: Tuesday, April 22, 2014 8:44 AM
To: personal_submersibles at psubs.org
Subject: Re: [PSUBS-MAILIST] Elco Motors

Joe, 

A good idea. Paul M. reckons the dsl/elec hybrid makes for the best psub for the obvious reasons, and so did Captain K. Autonomy is good. If it's 7-8K for the entire system, I would suggest that it ain't bad, considering. Then maybe add a variation on Hank's shaftless coupling, perhaps?

Vance

-----Original Message-----
From: Joe Perkel via Personal_Submersibles <personal_submersibles at psubs.org>
To: personal_submersibles <personal_submersibles at psubs.org>
Sent: Tue, Apr 22, 2014 7:46 am
Subject: [PSUBS-MAILIST] Elco Motors

Very interesting and informative data on Elco's marine website pertaining to sizing, rates of discharge, range, and hybrid matching http://www.elcomotoryachts.com/ep-600.shtml

I don't think its possible to scratch build the reliability of these particular types of products in the electric boat industry, these are fully engineered systems. At 7-8k, its an expensive motor and would have to be inside with a rotating shaft seal arrangement, but coming from an experimental aircraft perspective the price points on these motors is a comparative bargain. I'm looking at these from a long distance surface transit standpoint for the Seehund.

Joe <http://overview.mail.yahoo.com?.src=iOS> 

Sent from Yahoo Mail for iPad

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