Battery Ventilation when ‘Fast’ Charging

[capt lar]

Gord said - By way of comparison, a small 3" Bilge Blower would be capable of venting about 100 cfm, in a typical installation.

My Bristol came with a similar set up for another purpose, propane HW heater. The heater is now going, replaced with an Isotemp, but the vent in the bilge may remain. It is an easy way to move air thru the bilge, which is useful for a number of reasons, including Sean's batteries.
As to the batteries, and despite the thread on SSCA, I am changing over to AGM's. My electrician says, if I monitor and maintain, they are still better in many ways, and I can increase my amps without rebuilding boxes. We will see. Since the boat came with a big acid burn on the sole, I was motivated to move away from wet.

Larry

[Andina Marie]

This site has a battery vent fan that fits in a 2" PVC pipe plus an automatic controller that turns it on when the battery is charging and runs it for an additional 15 minutes after the charger goes into a float mode.

Battery vent fan and other items

[GordMay]

My previous advise, to not worry about venting, was based upon the use of a typical Bilge Blower Fan. These units are large, noisy, & power hungry, requiring a minimum of 3" dia. vent pipe.

I take it all back - and, once again recommend installing a Batt’ Box Vent Fan.

Thanks to Andina Marie, for the heads up ion the Zephyr Vent Fan!

The manufacturer’s website has a lot more information at Zephyr Industries Battery Box Ventilator:
http://zephyrvent.com/

I’ll be returning to this subject (soon ?), with a more detailed statement and recommendation.

Sorry for waffling (flip-flopping) ...

Gord

[JGI417]

I agree with the corrosive issure, depending where they are located I think this could cause problems.

[coot]

Originally Posted by ssullivan

Question: I'm not sure what I'm missing regarding the Trojan T-105's. I did a lot of research. I read that the 6V T105's are each rated at 225ah. I assumed that they retained that rated when I hooked them up in series to produe 12V. This isn't true?

It is true that each battery has the same capacity, but...

In a typical boat, everything is a 12 volt system, so you can get away with talking about amp-hours. The thing that is getting you is this: amp-hours is only meaningful when everything has the same voltage. You cannot compare the 6 volt amp-hours with the 12 volt amp-hours.

The real physical entity is watt-hours. watts = volts times amps. watt hours = volts times amps times time.

Your T-105 contains 225 AH at 6 volts, for a total of 6 * 225 = 1350 watt-hours. Use two batteries and you have 1350 * 2 = 2700 watt-hours.

But how do you draw the power out? In series, you draw 12 volt power. 2700 watt-hours / 12 volts = 225 AH at 12 volts.

( In parallel, you draw 6 volt power, and 2700 watt-hours / 6 volts = 450 amp-hours at 6 volts. )

If you have four of them, you probably have two banks of two batteries in series, for a total of 5400 watt-hours, which comes to 450 AH at 12 volts. If you sized your charger for 900 AH (and it sounds like you did), you can put another two or another four batteries, for 675 or 900 AH respectively.

[ssullivan]

Thanks, Mark. I don't know where my brain was during that post. I was exhausted. We are very close to being done with the boat, and this week's early season charter is going well!

I will be finishing everything up by the end of April and will have many MANY photos to post as soon as the gallery is back.

Thanks again for all your help with the charging situation. It appears to be working well... but I have yet to fully test it (by unplugging the unbillical cord..)

Originally Posted by coot

It is true that each battery has the same capacity, but...

In a typical boat, everything is a 12 volt system, so you can get away with talking about amp-hours. The thing that is getting you is this: amp-hours is only meaningful when everything has the same voltage. You cannot compare the 6 volt amp-hours with the 12 volt amp-hours.

The real physical entity is watt-hours. watts = volts times amps. watt hours = volts times amps times time.

Your T-105 contains 225 AH at 6 volts, for a total of 6 * 225 = 1350 watt-hours. Use two batteries and you have 1350 * 2 = 2700 watt-hours.

But how do you draw the power out? In series, you draw 12 volt power. 2700 watt-hours / 12 volts = 225 AH at 12 volts.

( In parallel, you draw 6 volt power, and 2700 watt-hours / 6 volts = 450 amp-hours at 6 volts. )

If you have four of them, you probably have two banks of two batteries in series, for a total of 5400 watt-hours, which comes to 450 AH at 12 volts. If you sized your charger for 900 AH (and it sounds like you did), you can put another two or another four batteries, for 675 or 900 AH respectively.