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Did some light reading and some math, a sealed 3 cuft battery box with 2-6v batteries charging at 30 amps will reach LEL in 2.4 minutes, could be off. Math is not my strong point, slept most of the time :)

This calculator say I need an air exchange every 11-12 minutes for a 3 cuft box, to meet the LEL standard of 1%. I currently use the van as the battery box so I have to do an air exchange every 1492 minutes (every 24 hrs is close enough).
Battery Room Hydrogen Gas Ventilation Calculator by SBS Battery

So a genius would have to figure out the diameter of a hole in the top and bottom of the battery box for the hydrogen flow freely. And that's not me:)
Hi Phil,
I looked around a bit and did not find anything to say exactly what size the vent exit hole on the top of the battery box should be.

There are some mentions of H being 14 times lighter than air and that a pocket of H will rise up through air at 45 mph -- so it really wants to get out.

Did find some links that talk about the subject a bit...

A discussion a boating forum about venting batteries...

This formula is proposed for H produced:
A = (0.045 x N x I) / V

Where:
N = Number of cells in the battery
V = Volume of compartment in cubic metres
I = Charge rate in Amperes

It seems to agree pretty well with your calculator.

Several opinions expressed in the discussion, but one takeaway is that some people are just not sealing their battery boxes and relying on leakage to ventilate -- and they have been doing this for decades.

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An article from Home Power magazine on designing battery boxes for off grid PV systems...
These have a lot more batteries than an RV would, and it looks like 2 inch PVC is used a lot for the vent piping.

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This guy actually measured H concentrations in a large battery box...
Its a two part video where the first part just shows the setup he used and 2nd part shows the actual measurements.
I guess you could say that it makes an argument for the idea that if you carefully seal up the battery box, then H concentrations will build to a bad level without some form of ventilation.

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Hard to reach any definite conclusions from the above, but it seems like...
  • It seems like 2 inch diameter would be very conservative
  • Something smaller (1 inch?) is probably fine?
  • Even just leaving battery box unsealed might work fine -- just use the leakage and fact that H really wants to go up to do it?
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I used 1 inch PVC on mine with a line from the top of the battery box to the sidewall of the van to vent the H outside. I have an opening low on the battery box that just goes to the inside of the van.

After using your calculator, it looks like it would be fine to just provide an opening through the top of the battery box and let the H vent into the van itself would have been fine and less work and one less hole in the van skin. It seems like the van provides enough volume that just normal air exchange with the outside would be plenty to prevent any significant H buildup. On my van, any H would just rise up the the Maxxfan in the van roof and leak out -- even if the lid was closed.

Gary
 

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I have done that in the past even with the 19 six volt batteries my home system that was run off my 114 V DC Dunlite wind generator. (30+ amps @ 114 V)! H2^
 

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OK can I help anyone? "I’ve been doing some hard travel’n” as Bob Dylan would say and now I am in AZ and available. You are all correct about the electrical. KOV keeps us using the forum in a way that lets questions get answered a few times not every day. I for one don’t want to answer over and over.
Some comments:
I didn’t think I would ever use the shore power part of the WFCO but have a few times in 4 plus years and in those times I REALLY needed it. I’d say buy the full featured WFCO and put a plug on the back of the van for the day you do.
This plan is plug and play BUT your needs and desires may vary so no one is going to do this exactly.
People complain about this forum? It makes me wonder what forum they like. My quick look at the Sprinter site and Transit site made me return here with relief.
We all have our quirks. In time you learn what sets people off. Avoid it and don't plan to win if an argument ensues. And if you get in deep with one of the moderators you can find yourself complaining about this forum on one of those other sites.
Rhetorical questions and answers are hard to defend. I have been there and now try to post my experience. If someone goes off and suggests something foolish suggest a simple alternative. My conflicts have been in this area as I feel simple is better, cheaper is often sufficient, and experimenting in new technology should be presented as such. These precepts led me to post the current thread and to request (along with others) it be a sticky.
As for the venting:
View attachment 58508
First; Thanks RD for this thread - Much Appreciated

Second; Do you have some photos of where/how this tube is vented to the exterior of your van. I did read thru the thread, but have missed this if you have provided it.

Thanks
 

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BatteryVent2.JPG BatteryVent.JPG
Vent on the left shore power plug on the right.
Inside:
BatteryBox.JPG
 
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RD

Thanks for those photos & showing the exterior battery cabinet vent. If I understand correctly the bottom of your battery cabinet is open to interior van air & the idea the lighter (possible hydrogen gas) vents from the battery box up and out?

Didn‘t want to hijack your electrical system thread, but appreciate showing this
 

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You are right about the bottom opening. Hydrogen is the vented gas to be considered and is so much lighter than air it rises relentlessly. I taught Chemistry so I could add a lot more but this is sufficient.
 
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Sounds like the H2O electrolysis process. I liked teachers like you when I was a kid when we would reverse the process with a flame and put 2 H’s back with an O

I would think if the bottom of your battery box and the remainder was sealed other than your large pipe to atmosphere, hydrogen could still escape to the exterior of your van, as your inlet is at the top of your box where hydrogen would collect, a tube with one 90 degree bend, & a large vent to atmosphere. To equalize battery box pressure I would think “make up” air from the exterior would finds its way via snorkel action. Kind of reverse of a propane locker with a bottom vent that would let any leaking propane out & exterior air in thru the same pipe if “pressure equalization” is required.

IIRC from a previous read, you used that large flex as it was left over equipment, thus larger than you figured need be. If you were using this vent tube for hydrogen exhaust & exterior air equalization, maybe it is already the correct size with a factor of safety
 

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I used to have a day the students called "explosion" day which I had to pre-warn the whole school due to the exuberance of some chemical combinations. You are right about the H2 escaping. I vented for that but also for other emissions that can have an odor and cause corrosion. None of these are serious if the venting is to the van in my opinion. The flex pipe was part of the vent kit I bought. Hydrogen is 7% the weight of air at STP. It will rise and disperse rapidly. However it can combust if at 4% concentration.
 

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Many here have developed the electrical system for their van and purchased too little, too much, or bought components that are technically sophisticated and expensive. I will give you some guidance here for a basic 200 watt solar, 200+ Amp Hour storage, with basic interconnection to the van and to shore power, plus an inverter. Many of these components I have used in my van or used in previous RV’s or have worked with others who have them. This system will run a 3 cu ft compressor refrigerator, a 700 watt microwave, LED lights, chargers for all your electronic stuff, 14 volt TV and lots more. It will connect to the van’s alternator, can be plugged into an outlet at a campsite or at your home, and can provide sufficient power when boon-docking for unlimited days IF the sun shines, if not run the van to charge.

1. Batteries- 2- 6volt flooded Lead acid golf cart batteries from Sam’s club 215 Amp Hour rating made by West Penn a very reputable firm. $84 each I suggest you vent them. Duracell Golf Car Battery - Group Size GC2 - Sam's Club
Alternative- 2 similar AGM batteries- the cost will be $600 and they are not quite as long lived but you do not need to vent them. Venting saves $400

2. Solar- 2- 100 Watt Renogy monocrystiline Kit PWM controller which will be fine, kit includes lead in and connectors, [ame]Amazon.com : Renogy 100 Watt 12V Monocrystalline Solar Bundle Kit With 30A PWM Charge Controller : Garden & Outdoor
Buy a 3’ length of 2” angle aluminum at Home Depot to mount them.
Alternative- buy 2 similar panels and a Tracer MPPT controller. You can add a third panel if you later find it is needed but I betting it won’t be.

3. Shore power/ breakers/fuses for 12 volt circuits- WFCO power center, get a 20 foot HD extension cord to lead in to it, buy breakers at H-D [ame]Amazon.com: WFCO WF-8735-P Black 30 Amp Power Center: Automotive

4. Interconnection to your van starting battery- Stinger 80 amp battery isolator. [ame]Amazon.com: Stinger SGP38 80-AMP Battery Isolator and Relay,BLACK: Automotive
I recommend a small switch to deactivate the interconnect most of the time.

5. Wire- http://assets.bluesea.com/files/resources/newsletter/images/DC_wire_selection_chartlg.jpg
THHN off the spools at H-D run in smurf tube (blue flex non-metalic conduit) when possible. To the other battery and to the power center run 4 AGW, to your refrigerator, lights and most low draw appliances use the Blue Sea chart.

6 Inverter- 1500 watt modified sine wave inverter- good for every thing you need- upgrade to sine wave if you must have a low watt induction cooktop. Some induction tops may run on this. Your risk. This comes with cables and a remote. [ame]https://www.amazon.com/KRIËGER-Inverter-Installation-approved-standards/dp/B00DNL05GW/ref=sr_1_12?ie=UTF8&qid=1510365966&sr=8-12&keywords=1500+watt+power+inverter[/ame]

7. Fuzes and such. Use the Blue Sea chart to install fuses that protect the wires, that is they need to be no larger than the wires can carry. [ame]https://www.amazon.com/s/ref=nb_sb_noss_2?url=search-alias=automotive&field-keywords=80+amp+fuses&rh=n:15684181,k:80+amp+fuses[/ame]
Fuse BOTH ends of the Positive Battery wire AT EACH battery, fuse the inverter AT THE Battery, fuse the other wires with the WFCO. Follow the WFCO instructions concerning grounding the shore line as it doesn’t get grounded to the chassis!

OK It’s a bit over $700, but I did get you to consider it. I often say solar is $500 and it is, the above is a complete system exclusive of a few USB and cigar outlets, some small switches, a bit of wire and some connectors. I can’t know what you will need exactly.

Take the money you save and go CAMP, visit good bars and restaurants that serve great food and drinks, take some pictures, renew your relationship with your SO, find the winter sun in the South, and remember the sunsets. If you have enough, doing is always better than having more.
Thank you so much for the great write up! After going for a few shakedown trips and reading this I have decided to greatly downsize my build. I had already purchased wiring / outlets / usb ends and such but had not spent the $$$ on the lithium batteries and high end power components. This was well over half of my proposed build budget. After using the van a few times I really cannot see that we would ever reap the true benefits of the high end system, plus there are many things about the lithium that had me worried I would burn up a very expensive system. I do have a question about the amount of solar... I had already carved out space on the roof rack for 3 panels and being that at this point the overall cost of a solar panel is not the most expensive part would I be doing any harm having 400 or so Watts of solar with this setup?

Thanks again.
 

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No problem, but each 100 watts is $100 of money that can be used elsewhere or for camping. My build had an Espar diesel furnace that cost more than my entire electrical system and a refrigerator that cost nearly as much. I argue for spending the money where it is needed. I hope you look back and found you made the right choice.
If you don’t buy the extra panel at least buy a solar controller that can handle it if you feel the need later.
 
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No problem, but each 100 watts is $100 of money that can be used elsewhere or for camping. My build had an Espar diesel furnace that cost more than my entire electrical system and a refrigerator that cost nearly as much. I argue for spending the money where it is needed. I hope you look back and found you made the right choice.
If you don’t buy the extra panel at least buy a solar controller that can handle it if you feel the need later.
Good point on the controller, my best bet right now will be to ensure proper controller size and leave the space open on the roof if I need it.
Thanks,
 
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