Battery fuse? I'm con-fused.

[asianflava]

So are guys saying that the 4ga that I used is overkill?

[Chuck Craven]

cracker39
Yes
There should be a main fuse. It should be rated just above the full draw of the battery.
So 30 amps for the inverter, + 10 amps for other things would be 40amps but you should us a 50 amp main fuse. This main fuse should be as close to the battery as possible.
The wire from the battery to the fuse box / distribution box should handle the max 50 amps it is fused for. Then each circuit wires from the dist./fuse Box needs to be able to handel that circuits current draw.

Chuck

[cracker39]

Chuck, there are no "other things". The battery feeds directly into the converter, as does the 110VAC line. The converter has a 25 amp reverse battery protection fuse, not a main fuise. Then, it has three 12V circuits with fuses and pos and neg wires to the battery. So, I'll probably put a 30 amp fuse inline between battery and converter.

[Chuck Craven]

OK
Lets see if I got it now! You are using the battery for just the inverter. Right?
The Inverter does the charging of the battery!
Then all you need is a fuse at the battery just in case the wiring would short and keep the battery from blowing up. That fuse needs to be say 10 to 15 amps larger than the normal current draw so that when the inverter starts up it will not pop the main fuse from inrush current.
Chuck

[Sonetpro]

I'm putting a fusible link on the wires that go to the battery. You can't fuse it any closer. And if it burns out the link I will have serious problems that will need to be fixed before I need that repaired.

[Chuck Craven]

SteveT
You do not want to use an open fusible link next to the battery. Most batteries produce oxygen and hydrogen when being charged and discharged and if a fusible link would burn open it will at least it will start a fire or explode the gasses. Should use a fuse-cartage or a circuit breaker just outside the battery box in open air.
Chuck

[Larwyn]

If batteries were as explosive as we are led to believe, we would all still be hand cranking our cars. Use caution, but most of all use common sense.

To hear some of the warinings you would think that if we really wanted to win a war we would strafe the enemy with deep cycle batteries......

[Sonetpro]

I'm using sealed AGM battery's. Fusable link doesn't burn open it just melts the wire if too much current is run through it. Chances are your car has a fusable link going from the battery to the fuse box, most manufacture's do so you wont burn up the wireing in case of a short.

[Chuck Craven]

Larwin
Most batteries in cars are in the open and air is pushing the gasses out from under the hood. Many of the pictures I have seen of tears, people are putting the batteries in closed spaces or making battery boxes fairly close up. Which levees the gasses in with the battery, fuses, converter and chargers. Well any spark will set off the gasses if not well vented. Oxygen mixed with hydrogen makes one big bang and all it takes is a spark.
Remember the Hindenburg it did not have oxygen to make it go bang. Just hydrogen and it melted aluminum in seconds. That whole air ship burnt up in just 10 minutes.
Chuck

[Nitetimes]

Oxygen mixed with hydrogen makes one big bang and all it takes is a spark.
Remember the Hindenburg it did not have oxygen to make it go bang. Just hydrogen and it melted aluminum in seconds. That whole air ship burnt up in just 10 minutes.
Chuck

The hydrogen didn't start the fire either, nor did a battery. Didn't explode either, just burned up.
I've had one battery explode on me and it was due to a direct short somewhere and there was no real explosion just a loud bang, a quick flash and acid all over me.
All that is neccesary is a little common sense and a vent and there shouldn't be any problems.

[Chris C]

I had one blow up when starting my brand new '76 T-Bird. Turned the key and BANG.........it was all over. No fire.........just battery acid all under the hood. What a mess. I haven't decided whether to put the battery on the tongue on in the galley, so this is all very interesting.

[cracker39]

OK
Lets see if I got it now! You are using the battery for just the inverter. Right?
The Inverter does the charging of the battery!
Then all you need is a fuse at the battery just in case the wiring would short and keep the battery from blowing up. That fuse needs to be say 10 to 15 amps larger than the normal current draw so that when the inverter starts up it will not pop the main fuse from inrush current.
Chuck

Chuck, you keep saying inverter. I don't have an inverter. I have a convetter. Inverters convert 12VDC to 110 VAC. Converters convert 110VAC to 12VDC. When I have shore power, my converter will provide the 12VDC for my TTT and charge the battery if it needs charging. Otherwise, my battery will provide the 12VDC current, through the converter. My whole TTT won't use more than 7 or 8 amps of 12VDC power, so I won't need more than a 30amp main fuse between the battery and the converter.

[Larwyn]

I'm using sealed AGM battery's. Fusable link doesn't burn open it just melts the wire if too much current is run through it. Chances are your car has a fusable link going from the battery to the fuse box, most manufacture's do so you wont burn up the wireing in case of a short.

Steve

I too am using an AGM battery. It will be in the galley and have one small vent near the top of the battery compartment, because as we all know, hydrogen is lighter than air.

The main reason I am using the AGM is to eliminate the possiability of battery acid splashing out in the TD. The glass mat is only 95% saturated with acid, it cannot leak, even if the case is broken open. And it will handle the neglect that it WILL recieve and still hold it's charge.

Hydrogen gas is considered hazardous when it reaches a level of 4%, that is a huge amout, even in a small space.

[Chuck Craven]

Well a vent at the top will let out the hydrogen gas only if you have a vent on the bottom to let in air for displacement of the lighter gas. A led acid battery 1 year old under a quick charge will produce ½ leader of out gas in one hour. Which is 70% hydrogen and 30% oxygen. It would not take long to get to 4% to go boom in a small space like a cupboard or a battery box. Oh by the way a fusible link gets hot and melts but makes a spark when it opens.
The more tired the battery gets the more it outgases. Then other gases are produced which can kill you. Even the sealed gel-cell out gasses.
If it is led acid it has to out-gas.
Chuck

[Larwyn]

Well a vent at the top will let out the hydrogen gas only if you have a vent on the bottom to let in air for displacement of the lighter gas. A led acid battery 1 year old under a quick charge will produce ½ leader of out gas in one hour. Which is 70% hydrogen and 30% oxygen. It would not take long to get to 4% to go boom in a small space like a cupboard or a battery box. Oh by the way a fusible link gets hot and melts but makes a spark when it opens.
The more tired the battery gets the more it outgases. Then other gases are produced which can kill you. Even the sealed gel-cell out gasses.
If it is led acid it has to out-gas.
Chuck

Seems to me that if you fill a glass with hydrogen it would simply rise, the heavier air would displace it. I'm sure it would not fill with a vacuum.

I'm a bit confused how a vent at the bottom would allow the heavier air to rise to the occasion........

EDIT: Never mind, it would be pressure equalization. I do see the point in the lower vent now.....thanks for kick starting my thoughts there...