Discuss: Batteries in Plastic Boxes or Open?

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TimK

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Apr 25, 2008, 1:31:12 PM4/25/08
to Civic EV Kit
Hi all,

Another question to pose to the group as we design battery racks
and boxes:
Which batteries should be enclosed in a polypropylene box and which
can sit
out in the open? In general, I've seen the nine batteries in the rear
trunk enclosed
in a polypropylene box with a vent fan, while the batteries under the
hood are
left open, probably due to the immediate venting to the outside air.
My concern is that while giving the battery pack a balancing charge,
the
batteries under the hood would probably "boil" a bit and generate some
acid
spray on the chassis, causing damage. I've heard that using bayonet
caps may
solve this issue.
Putting batteries in polypropylene boxes can save acid splash, but
can also
take up precious space when cramming all the batteries in and they
also cost
additional money to cut and weld. The professional EV conversion kit
I got from
ElectroAuto for the Porsche 914 had all batteries in boxes, but this
was also
a higher end kit. The open-source Civic EV project is targeted at
people wanting
a practical, economical design.

Is putting the rear nine batteries in a box and leaving the front
batteries open with
bayonet caps good enough? What are people's thoughts on this?

Cheers,
Tim

Chris Brune

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Apr 25, 2008, 2:36:16 PM4/25/08
to civic-...@googlegroups.com
Hi Tim,
For me personally I would never want to own another EV that has flooded batteries.  I don't like the watering, and I don't like the lack of performance.
I had been meaning to ask what you had in mind for batteries.
Regards,
Chris


Hi all,

Cheers,
Tim


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Rob Connelly

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Apr 25, 2008, 3:59:12 PM4/25/08
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Tim,

I agree completely. I was nearly turned off of the concept of the EV
conversion when I read about the flooded cells and their maintenance. I
elected to go for 12 Optima 31 AGMs for that very reason. They are costly,
but so much less hassle.

As such, I don't have battery boxes in my installation at all -- either
under the hood or in the trunk. Is that a good idea or not? I don't know.
I would be interested in opinions from the group.

- Rob

TimK

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Apr 25, 2008, 10:02:06 PM4/25/08
to Civic EV Kit
Hi Rob and Chris,

Thanks for your input regarding the Optimas. I've just uploaded a
file (BatteryAnalysis.xls) where I've compared some of the
characteristics of the flooded lead-acid and the optima 34M and group
31 batteries. Please let me know if I got anything wrong.

I agree with both of you that flooded batteries have lower
performance, but you just can't beat the price. With my garden
sprayer, I don't find watering the batteries that much of a hassle.
I'm looking into pricing for the automatic battery watering systems
put out by Flow-Rite: http://www.flow-rite.com/pro-fill/index.html?open_menu=0&sub_menu=1

I'm really intending for this kit to be economical, so I'm still
tending towards the flooded cells. Of course, the kit is flexible and
upgrade options and modifications are always welcome. Perhaps we
could have a low-cost high-maintenance system and a high-cost high-
performance system.

What do both of you use for battery balancers? Flooded batteries do
have the advantage of "overcharge and boil" to balance them.

Cheers,
Tim


On Apr 25, 12:59 pm, "Rob Connelly" <r...@finelineprototyping.com>
wrote:

Chris Brune

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Apr 26, 2008, 8:27:45 AM4/26/08
to civic-...@googlegroups.com
Hi Tim,
I certainly understand the advanatages of flooded. I'm just not willing to go there.

I have individual battery chargers thus battery balancers are not necessary.

Rob Connelly

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Apr 26, 2008, 8:52:06 AM4/26/08
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Tim,

That might be a good approach to call out two different systems. People can
decide for themselves.

I used the full suite of equipment from Belktronix (www.belktronix.com) for
my EV. It was designed especially for AGM's and as such it has individual
battery monitors to protect against over-voltage during charge, and
undervoltage during discharge. I plug in the whole car, and the system
takes over. As each battery reaches it upper limit, the current is shunted
around it so that the others can continue charging until they reach their
upper limit. Then, the system switches into float mode to top them off.

As you are driving, if any cell drops below the lower limit of voltage, the
system dials back on how much current it draws so that a cell does not get
damaged.

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