[Oeva-list] Lee Harts Battery Balancer

John RA Benson jrab at e-m-w.com
Sun Mar 4 21:01:05 PST 2007

Well, you know I'm in!

If you look at the alternatives, there isn't much there at a reasonable
price point. Powercheqs are $58.00 from
http://www.evsource.com/tls_powercheq.php, but aren't really good for long
battery strings (12+). Rudman regs are $75. The mk2's are being phased out
at only $45. So from a purely financial standpoint, $30/battery would be
fantastic. $50/battery would still be pretty good. They all have their
advantages and disadvantages, of course. What I like about Lee's is that
it's not dumping energy away, and it's easy to monitor the voltages. If you
put good batteries in the vehicle, I hope it pays to take care of them.


On 3/4/07 1:56 PM, "Theoldcars at aol.com" <Theoldcars at aol.com> wrote:

> Hello Tim
> I want to state right off I am not an expert on electronics or manufacturing
> them. My profession for over thirty years has been collision repairs. My
> automotive hobby has been stock and modified 1955 Chevrolets. I have always
> been a car nut but only four years ago did I take a serious look at electric
> vehicles. 
> I considered building an electric vehicle but decided not to for several
> reasons. After adding up the cost I could buy a factory made vehicle for less
> than I could buy the parts. I would have an electric vehicle right away
> instead of who knows how long it would take to finish. Plus not knowing
> anything about them I felt it would be a good way to start.
> In the last four years I have learned a lot about batteries and the factory
> electric vehicles. Using the factory service tools with the BMS has shown me
> how difficult it is to keep from killing lead acid batteries. Lee's balancer
> would solve some of the major challenges I have seen with Lead acid and NiMH
> batteries. If I could buy the balancer already done I would be using it.
> Right now I am not up to speed enough on electronics. I rely on everyone who
> knows more about this than I do. From the feed back it sounds like if I backed
> building 100 of the balancers I might still have most of them 5 years from
> now. I think a price range of 25 or 30 dollars a battery on a 12 battery pack
> might be in reach if a high enough number was built. This is just a wild guess
> with no research as to how many would really take to reach that price.
> The size of the run would depend on the price breaks. If it makes sense to
> manufacture 10 or 1000 would come down to two factors. How much is it going to
> save and are there enough EV drivers who see the value of it. Can the price be
> brought down to what most people consider affordable? I wonder how many EV
> drivers understand the value of the balancer? Without being able to see all
> your batteries voltage under power demands how would an EV driver ever know?
> There are a couple of EV drivers out there who have made battery monitors but
> not very many.
> The power supplied by Lee's balancer would make a real difference. Trying to
> get by with 1.5 amps would too much of a compromise. I have observed the out
> of balance in a pack is greatest in higher states of discharge under load. As
> the load on the batteries increases the greater the balance difference between
> batteries. As the pack ages this condition occurs more and sooner. The 1.5
> Amps is not going to be enough on older batteries.
> If you or anyone else would like to work with me on moving forward with Lee's
> balancer let me know.
> Thank you
> Don
> In a message dated 3/4/2007 7:04:16 AM Pacific Standard Time,
> oeva-list-request at oeva.org writes:
>> Message:  3
>> Date: Sun, 4 Mar 2007 07:00:41 -0800 (PST)
>> From: Tim Kutscha  <tim_kutscha at yahoo.com>
>> Subject: Re: [Oeva-list] Battery  Balancer
>> To: oeva-list at oeva.org
>> Cc: sorefeets at yahoo.com
>> Message-ID:  <955498.63905.qm at web36913.mail.mud.yahoo.com>
>> Content-Type:  text/plain; charset="iso-8859-1"
>> Hi Don,
>>   Thanks for the  excellent feedback you forwarded from Lee Hart regarding
>> the flying capacitor  balancer.  Having years of experience can provide
>> valuable information  that a theoretical or prototyped approach would not.  I
>> think all of  Lee's points are correct.  The charge transfer as the batteries
>> get  closer together in voltage becomes very slow.  There are definite losses
>> in the FETs, caps and batteries.  What I liked about the design was its
>> simplicity (no STAMP controller or DC-DC converter).
>>   My main goal is  to make something effective that costs around $10 per
>> battery.  The  modification that Paul Compton did sounds very interesting to
>> me.  If we  could upgrade the single DC-DC converter to 20-Watts, then we
>> might transfer  1.5 amps instead of 0.3 amps.
>>   I'd be happy to help you do research  on this.  Do we have access to the
>> plot files for the boards?  How  do you plan on creating the PC-boards?  Are
>> you planning any  modifications from the original design?  When you say
>> "large run," how  many are you thinking of?
>> Regards,
>> Tim
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