Is there a formula for how many cubic inches a vent hole (or holes) need to be based on the size of the box? x^3" per x^3 ft. of interior space?
Tips on Battery Box Build
- Thread starter GonzoF1
- Start date
Gonzo,
There may be in Calder's writeups, but aren't we really dealing with a kinda Catch 22 here?
Closed box to keep fluids/acid from migrating, then vent holes for air!!!
Guess the trick is to vent the holes at the top, eh?
Also don';t forget to ventilate the part of the boat the boxes sit in, too!
Always somethin', ain't it?
There may be in Calder's writeups, but aren't we really dealing with a kinda Catch 22 here?
Closed box to keep fluids/acid from migrating, then vent holes for air!!!
Guess the trick is to vent the holes at the top, eh?
Also don';t forget to ventilate the part of the boat the boxes sit in, too!
Always somethin', ain't it?
Not trying to back yall into a corner, but I will take a look in the book. It is actually sitting right next to me
when ventilation is needed, more is usually better... and positive ventilation is better than passive ventilation.
hydrogen (battery gas) rises and it should be vented to the outside of the boat (or cockpit).
there are many more boats that lack any outside ventilation for the batteries, than there is those with ventilation... and for boats over 15years old, the majority of them dont even have a dedicated battery space, but have the batteries secured on a shelf near the engine or setting in a locker inside the living space of the boat.
if the ventilation is passive, it should be bigger, and if its positive, a smaller vent tube is fine.... the difference is, with a passive system, the gas exits at its own leisurely time and needs a larger vent to do so, where the positive ventilation will force clean air in and push the gas out thru a smaller vent line...
this positive ventilation can be accomplished simply with two clamshell style cowl vents, with the lines running to opposite corners of the box.
but unless the box is well sealed, some of the gas will undoubtedly escape to the space within the boat, so in that case I would argue that it may be easier to create positive ventilation in the space with an engine compartment blower fan to bring fresh air in, and keep the sparks to a minimum when equalizing the batteries.... as long as you have fresh air coming in faster than the batteries are creating the gas at explosive levels, there will be no problems....
and short term breathing of hydrogen is not so hazardous as long as the concentration does not reach the level where it displaces the amount of oxygen that is needed to sustain life, OR, as long as the concentration does not get so high that it could explode in you.
deaths to consumers by explosive gases is commonly due to them inadvertently breathing the gas into their lungs, and when the explosion/concussion occurs, the air/gas in their lungs is pushed out, ignites in the explosion, and the small amount of gas left inside them is still enough to flash burn, at a very intense heat... and interior nose, throat and lung burns are almost always fatal.
hydrogen (battery gas) rises and it should be vented to the outside of the boat (or cockpit).
there are many more boats that lack any outside ventilation for the batteries, than there is those with ventilation... and for boats over 15years old, the majority of them dont even have a dedicated battery space, but have the batteries secured on a shelf near the engine or setting in a locker inside the living space of the boat.
if the ventilation is passive, it should be bigger, and if its positive, a smaller vent tube is fine.... the difference is, with a passive system, the gas exits at its own leisurely time and needs a larger vent to do so, where the positive ventilation will force clean air in and push the gas out thru a smaller vent line...
this positive ventilation can be accomplished simply with two clamshell style cowl vents, with the lines running to opposite corners of the box.
but unless the box is well sealed, some of the gas will undoubtedly escape to the space within the boat, so in that case I would argue that it may be easier to create positive ventilation in the space with an engine compartment blower fan to bring fresh air in, and keep the sparks to a minimum when equalizing the batteries.... as long as you have fresh air coming in faster than the batteries are creating the gas at explosive levels, there will be no problems....
and short term breathing of hydrogen is not so hazardous as long as the concentration does not reach the level where it displaces the amount of oxygen that is needed to sustain life, OR, as long as the concentration does not get so high that it could explode in you.
deaths to consumers by explosive gases is commonly due to them inadvertently breathing the gas into their lungs, and when the explosion/concussion occurs, the air/gas in their lungs is pushed out, ignites in the explosion, and the small amount of gas left inside them is still enough to flash burn, at a very intense heat... and interior nose, throat and lung burns are almost always fatal.
Thanks for the input everyone...
So what I have done is mock-up all the boxes in standard sheathing plywood to get an idea of fit and size in the compartment. Once that is done, I am going to take a couple of sheets of marine grade plywood over to a local waterjet cutting business and let them precisely cut it to spec. I think it will make for a far superior, better sealing, longer lasting box. Below is a picture of two of the 2-up boxes. There are two 2-up, one 4-up, and one 3-up for the start batteries. Each house bank box is a 12V "cell" that will be combined at a heavy duty buss bar.
My question now is how to attach them? In the other two pictures are the port and starboard sides where the boxes will go. The port side shows the empty shelf where I have already removed the big 8D plastic box. These are/were attached by 16 large screws - four in each corner.
Now, remember this is a motoryacht. I don't really need to worry about blow-over. If I ever experience it, I'd have much bigger problems than worrying about the batteries. However, at 22 MPH top speed, in rougher seas, they will probably take a pretty good beating. I was considering (first filling the old holes with epoxy) going back to the original screw-thru-the-bottom idea, PLUS throwing a single strap over the smaller boxes and two over the bigger one. But TBH, I have yet to work out where and how to attach them. That is part of the test fit I suppose.
Any ideas?
So what I have done is mock-up all the boxes in standard sheathing plywood to get an idea of fit and size in the compartment. Once that is done, I am going to take a couple of sheets of marine grade plywood over to a local waterjet cutting business and let them precisely cut it to spec. I think it will make for a far superior, better sealing, longer lasting box. Below is a picture of two of the 2-up boxes. There are two 2-up, one 4-up, and one 3-up for the start batteries. Each house bank box is a 12V "cell" that will be combined at a heavy duty buss bar.
My question now is how to attach them? In the other two pictures are the port and starboard sides where the boxes will go. The port side shows the empty shelf where I have already removed the big 8D plastic box. These are/were attached by 16 large screws - four in each corner.
Now, remember this is a motoryacht. I don't really need to worry about blow-over. If I ever experience it, I'd have much bigger problems than worrying about the batteries. However, at 22 MPH top speed, in rougher seas, they will probably take a pretty good beating. I was considering (first filling the old holes with epoxy) going back to the original screw-thru-the-bottom idea, PLUS throwing a single strap over the smaller boxes and two over the bigger one. But TBH, I have yet to work out where and how to attach them. That is part of the test fit I suppose.
Any ideas?
Attachments
the base to which the box will set on could be questionable, but as long as it can support some dynamic loading without collapsing, there should be no worries
attaching the box should be done with 5/16" or 3/8" stainless or galvanized bolts/lag screws, and if possible it should be bolted down to a very solid base, AND lagged or bolted securely to a bulkhead... it will never move.
remember when building the box, before doing the final finish work to it, to place it in the boat and find out where the bolts/lags will be located, and then recess these spots with a forstner bit so the heads dont interfere with the battery..
attaching the box should be done with 5/16" or 3/8" stainless or galvanized bolts/lag screws, and if possible it should be bolted down to a very solid base, AND lagged or bolted securely to a bulkhead... it will never move.
remember when building the box, before doing the final finish work to it, to place it in the boat and find out where the bolts/lags will be located, and then recess these spots with a forstner bit so the heads dont interfere with the battery..
This is the original battery position, so I am pretty sure it will hold, but I may put a layer of ply over it before... Just for that extra little bit.
The underside has little or no access, so thru-bolting would be a challenge. But I may lag or do what the factory did and use a lot of prett good size screws.
Good tip on the forestner bit... THANKS!
The underside has little or no access, so thru-bolting would be a challenge. But I may lag or do what the factory did and use a lot of prett good size screws.
Good tip on the forestner bit... THANKS!