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Re: [EVDL] Buddy pairs AGM & Floodie

The internal resistance of the AGM and flooded batteries will be
different, and the parallel pairs of different batteries will overwork
the lower resistance battery and underwork the other. Your idea of 2
strings solves this. You could even have two strings, each tied to its
own controller, tied to its own motor, on two separate drive wheels or
two drive axles. Some type of logic or computer could decide on certain
conditions the amount of power that is needed from each set of


-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Michael Barkley
Sent: Wednesday, August 22, 2007 4:00 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Buddy pairs AGM & Floodie

Could you in the case of having a flooded acid string,
and the other string AGM, use blocking diodes on each
pack, so that each pack was isolated from each other,
yet both feeding the controller at the same time.
Seems this would at least eliminate one string
charging/discharging the other. Sure would take some
whopping big diodes to do this, I suppose.

--- Alan Brinkman <[email protected]> wrote:

> Marty,
> I am just guessing here as I have no experience etc.
> with this. I think
> that two batteries of different chemistry or built
> differently would
> charge / discharge each other at the different
> voltages and power use
> rates or charge rates that they would be subject to.
> In certain
> situations wouldn't the batteries fight each other,
> or lose efficiency
> as one discharges into the other, then back and
> forth over the range of
> operation. When you charge or discharge a battery
> you lose a little due
> to the system not being 100% efficient. Enough
> small partial cycles
> back and forth and there is some loss. Is this
> significant? Does the
> benefit of having another battery choice between AGM
> and flooded
> outweigh any loss?
> It would be interesting to set up a test with three
> battery systems.
> 2 flodded batteries in parallel.
> 2 AGM batteries in parallel.
> 1 flooded and 1 AGM in parallel.
> The batteries should be as close in capacity as
> possible or practical or
> available.
> Charge and discharge each set similarly and keep
> data on everything.
> Is the "1 flooded 1 AGM" set better at something?
> What does it do best?
> What does the 2 flooded set do best?
> What does the 2 AGM do best?
> I would think that if the "1 flooded 1 AGM" did turn
> out to work well,
> that you would have a battery with a little of both
> attributes of
> flooded and AGM. Someone needing a tad more range
> than AGM alone, and a
> tad more available power that flooded alone would be
> pleased to have
> another option.
> How would you know if the "1 flooded 1 AGM"
> combination did not work?
> Could you average the results from the other two
> battery sets, and
> expect at least that much performance from the "1 &
> 1"? If you noticed
> a 1 percent loss in performance or a 1 percent extra
> need for charging
> in the "1 & 1" could you say that was acceptable,
> and use this system to
> meet your unique needs between speed and range? If
> you noticed a 25
> percent loss in performance between the "1 & 1" and
> the average of the
> other two systems, could you chalk that up to the
> flooded battery and
> the AGM battery in the mixed set fighting each
> other, or charging and
> discharging each other during a range of use and the
> resulting
> inefficiency of charge / discharge cycles?
> I wish I had the time and equipment to check this
> out, but do not.
> Alan
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On
> Behalf Of Marty Hewes
> Sent: Wednesday, August 22, 2007 6:41 AM
> To: Electric Vehicle Discussion List
> Subject: [EVDL] Buddy pairs AGM & Floodie
> Hi All,
> I'm no battery chemist or charging expert. But I've
> been thinking of
> running two strings in parallel, an AGM string and a
> floodie string,
> figuring the AGM's would get me some acceleration,
> the floodies would
> get me
> more range. But I haven't found much data on how
> the two strings would
> interact with each other.
> Now I'm wondering if it would work better if I
> paired a 12 volt AGM and
> a 12
> volt (or two 6 volt) floodies as a buddie pair, and
> then charged them
> with
> AGM type battery management? If a 12 volt floodie
> were paralleled with
> a 12
> volt AGM, and charged as one battery like an AGM,
> what would be the
> impact
> on the floodie?
> Marty
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