I am getting rid of two old 12v batteries and upgrading to 4 6v batteries. Two will replace the originals, but 2 will be placed back in a compartment near where the inverter is installed.I am convinced that I would like to ventilate the space, but the dealership wiring the batteries did not have any suggestions.I have done some looking, and it seems ignition shielded bilge blowers would be ideal, if not on the large side.In addition to finding a fan, I think I also need some kind of speed control and a thermostat. Going down the same road as a bilge blower I found a marine-grade unit for about $1k.I am looking to do the right thing, but on a budget. Has anybody added ventilation for a project like this, or does anyone have any suggestions? Thanks in advance for your thoughtful answers.

welcome to the forums!absolutely batteries need ventilation. if your compartment is sealed, or you can put a sealed battery box inside it, most of those don't have active ventilation, just tubing to dump the acid vapor and hydrogen gas outside the rig... that I've seen anyway.bigger issue, if your four batteries can't be next to each other, that will cause problems with balance down the load. The two near the inverter are going to get beat up while the other two wherever-else are slacking off.is there any way to mount all four near the inverter, or separate into two banks with a bank selector switch (blue sea for example)

Do not place batteries in the same compartment as the inverter.Do wire in series (oem space to additional).Do wire in a balanced manner.

There is no way to get 4 batteries in the original tray, but I can separate them with a A/B bank selector.Is there a recommendation for a fan/speed-control/thermostat for this kind of installation where at least some of the batteries are going to be in a compartment that requires ventilation.

Yes, they should be ventilated.No, you don't need a blower...but if you are going to get a blower, it should cost anything close to $1k. You can get a marine blower for $20...but again, it's not needed.Go to the local dealer and look at what they use on new units. It's typically a sealed box with a 2" hose leading to an outside area with no fan.PS: Boats are trying to vent gasoline fumes which are heavier than air and settle in the bilge and stay there until blown out. Batteries vent hydrogen which is lighter than air and will float away on it's own.

pianotuna wrote:Do not place batteries in the same compartment as the inverter.I did. Inverter right beside a Group 31 AGM which allowed me to connect the two with short 18" heavy gauge cables for minimal voltage drop under heavy load. No issues, no need to vent the battery, perfect solution to voltage drop. :B

Do extra batteries need ventilation? | Good Sam Community

GordonThree
Explorer
Apr 24, 2019
welcome to the forums!

absolutely batteries need ventilation. if your compartment is sealed, or you can put a sealed battery box inside it, most of those don't have active ventilation, just tubing to dump the acid vapor and hydrogen gas outside the rig... that I've seen anyway.

bigger issue, if your four batteries can't be next to each other, that will cause problems with balance down the load. The two near the inverter are going to get beat up while the other two wherever-else are slacking off.

is there any way to mount all four near the inverter, or separate into two banks with a bank selector switch (blue sea for example)
pianotuna
Nomad III
Apr 25, 2019
Do not place batteries in the same compartment as the inverter.

Do wire in series (oem space to additional).

Do wire in a balanced manner.
ja99er
Explorer
Apr 25, 2019
There is no way to get 4 batteries in the original tray, but I can separate them with a A/B bank selector.
Is there a recommendation for a fan/speed-control/thermostat for this kind of installation where at least some of the batteries are going to be in a compartment that requires ventilation.
valhalla360
Navigator
Apr 25, 2019
Yes, they should be ventilated.
No, you don't need a blower...but if you are going to get a blower, it should cost anything close to $1k. You can get a marine blower for $20...but again, it's not needed.

Go to the local dealer and look at what they use on new units. It's typically a sealed box with a 2" hose leading to an outside area with no fan.

PS: Boats are trying to vent gasoline fumes which are heavier than air and settle in the bilge and stay there until blown out. Batteries vent hydrogen which is lighter than air and will float away on it's own.
SoundGuy
Explorer
Apr 25, 2019
pianotuna wrote:
Do not place batteries in the same compartment as the inverter.

I did. Inverter right beside a Group 31 AGM which allowed me to connect the two with short 18" heavy gauge cables for minimal voltage drop under heavy load. No issues, no need to vent the battery, perfect solution to voltage drop. :B
azrving
Explorer
Apr 25, 2019
You can place the batteries farther away but use large gauge cable. Balance the connections. It may seem like a waste of wire but it will even up discharge/charging.
GordonThree
Explorer
Apr 25, 2019
SoundGuy wrote:
pianotuna wrote:
Do not place batteries in the same compartment as the inverter.

I did. Inverter right beside a Group 31 AGM which allowed me to connect the two with short 18" heavy gauge cables for minimal voltage drop under heavy load. No issues, no need to vent the battery, perfect solution to voltage drop. :B

X2 I have four G31 AGM and a Magnum in the same bay. My space is much smaller, so I've added vents and a temperature controlled fan.

I was guessing the OP bought wet cell batteries?
beemerphile1
Explorer
Apr 25, 2019
ja99er wrote:
There is no way to get 4 batteries in the original tray, but I can separate them with a A/B bank selector.
Is there a recommendation for a fan/speed-control/thermostat for this kind of installation where at least some of the batteries are going to be in a compartment that requires ventilation.

Since batteries only really need vented when charging I would connect an AC fan that would be powered from the same source as the charger.

If you charge with solar you could power a DC fan on the load side of the solar controller.
naturist
Nomad
Apr 25, 2019
Do note, regular lead acid batteries must be ventilated lest really bad things happen. AGM batteries, not so much.

Regular batteries give off hydrogen, an explosion hazard, thus the ventilation and also why not in the same compartment with an inverter. AGMs, on the other hand, do not, thus are not the explosion hazard.
myredracer
Explorer II
Apr 25, 2019
Sealed vented MTS Products battery box. Commonly used in FWs. Vent should be min. 6" above top of box. Can tee the hoses so you don't need 4 grilles. These are kinda tall and may not fit in some spaces.

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