Wet Lead Acid

I think it is time to have a serious look at using wet lead acid batteries.

If I use Trojan T-105 batteries, It will be about $100 cheapter per 12V and I will get 225Ahr instead of 150Ahrs, all for about the same weight.

I also have the peace of mind that these are proven in ev applications (unlike the chinese AGMs that are the alternative)

If I go that way then I need to do some careful battery box design - here is a good article from EVDL mentioning the use of a sensitive vacuum switch - sounds like a good idea to me

http://www.evdl.org/archive/index.html#nabble-td17693571



Re: Battery box fan
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by Roland Wiench Jun 07, 2008; 12:53am :: Rate this Message: - Use ratings to moderate (?)

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Hell Barry,

I do not use 12 VDC to run my battery box ventilation fan. It's a 120 VAC
120 cfm fan that is inline with a heavy duty 2 inch inside diameter flexible
PVC acid proof flex hose that has 1/4 inch thick walls. The fan and fan
blades are all plastic and the electrical fan wires are seal in totally
enclose compartments at the fan connections.

I now have been running 33 years with out a fan ventilating the battery
enclosure while the EV is moving. There is a 2 inch pvc pipe that goes
below the EV and is elbow forward with a screen and 3M filter material in
it. The forward movement of the EV brings in air into the battery enclosure
and exits out the other side.

This fan is used only when I charge the batteries. I install the battery
box ventilation control system, just like we do in gas fire boiler systems.

First, I must turn on the fan switch which the fan must run first to clear
any battery venting that may be present. A pressure/vacuum switch detects
the movement of air present and it will then turn on a 2-pole DC contactor
that then connects the output leads of the battery charger to the battery.

The pressure/vacuum switches are super sensitive and you can get them from a
heating and plumbing supplier.

When the fan is up and running and the flow of air is present, a fan
indicator lite will come on, a flow air lite comes on. I then turn on the
charger contactor which also gives me a indication, that I am connected.

I then look at the on board charger panel meters which is a AC volt, AC amp,
DC volt and DC amp. The AC volt meter will indicated that my AC main plug
is contacted and the DC volt meter indicates that I have main battery power
present up to the battery charger output contactor.

Before I turn on my charge, I make sure that the charger circuit breaker is
off and the current knob is at 0 amps. I then turn on the breaker, and
while watching the AC and DC ampere, I turn the current up while watching
the indicators meters.

At any time the battery box exhaust fan fails, the fan pressure/vacuum
switch then turns off the DC contactor which removes the charger circuit
from the batteries. A larger second fan maintains a positive air pressure
in a separate totally enclose charger compartment.

The battery box exhaust exits out the bottom of the EV like a exhaust pipe
does. If I park in the garage with the garage door down, I run out a exhaust
hose either under the garage door or use a garage door port, like you see in
gas stations.

My garage maintains a 70 degree temperature a year, so when I am charging
the batteries, the fans pull this 70 degree garage air through a 3-M filter
which I cut out of a large 2 inch thick 3M filter material and insert it
into the air input side of the battery box ventilation system.

You must be care full not to cross feed the battery box exhaust system with
the air input. At one time, I did not have this fan exhaust system install
this way. Could always detect a battery vent order. I went into the garage
where I was charging the batteries and when I turn off the charger, this
ignited some hydrogen in the charger compartment and blew the charger
bridge.

Roland