Is putting AGM batteries inside a bus safe?

[belfert]

I have been thinking about putting AGM batteries inside under a bunk.  Craig Shepard is telling me I shouldn't do it for safety reasons.  I didn't really think about it all that much, but even an AGM battery could still catch fire or explode under the right circumstances.  I suppose in the bays gives a few more minutes to escape in case of fire.

Would the rest of you guys put AGM batteries inside a bus or would you put them in a bay for safety reasons?

[captain ron]

Brian, If my memory serves me right you have very large bays. Why would you even think of using up any cabin storage place?  With enough creative thought you could put a lot of your mechanicals in one bay if not all.

[Sean]

Brian,

All of our house batteries, 22kWh worth (eight size 8D) of AGM, are inside.

One of the key benefits of AGM is that they are code-approved for installation in occupancy areas.  They can also fly on commercial planes, unlike, for example, flooded lead-acid batteries.  That said, I have had more than one knock-down, drag-out argument with geezer code officials or fire marshals about this -- usually, I won.

If you set fire to an AGM battery, it will most likely pop the vent and outgas.  But if you set fire to a foam-cushioned sofa, it will also release toxic gases (not to mention burning hotter than hades), yet virtually everyone uses foam-cushioned furniture in RV's.  It's a matter of what, exactly, you are trying to protect against.

If your bus is on fire, you should evacuate.  For much better reasons than that your AGM batteries may vent.

Go ahead and put them inside.  It's legal and very safe -- much safer than many other things you're likely to have inside (with all due respect to my good friend Craig).  Just remember to install proper catastrophe fuses, and set your charger output at an appropriate level for the size of the bank.

-Sean
http://ourodyssey.blogspot.com

[Sojourner]

Amen to Sean! All power chairs for handicaps are equips with AGM battery.....uses around home & stores while charging.

FWIW

Sojourn for Christ, Jerry

[belfert]

Brian, If my memory serves me right you have very large bays. Why would you even think of using up any cabin storage place?  With enough creative thought you could put a lot of your mechanicals in one bay if not all.

Actually, my bays are smaller than even a 40' MCI.  The front bay is 2/3 the width of the rear bays.  The rear most bay is basically completely full with tanks, plumbing, and the generator on one side.  Some posted the size of luggage bays in cubic feet and the Dina was one of the smallest.

On my fall trip we had every inch of the luggage bays full from top to bottom and had some cargo stuffed inside the bus.  If we didn't have a specialized trailer for launching rockets we would have pulled my enclosed trailer for even more cargo space.  Even the launch trailer had some crates of stuff and firewood on it.  I really would prefer not to sacrifice any more bay space if I can help it.

[belfert]

As far as an explosion/fire hazard I was thinking of the battery itself catching fire or exploding.  Not likely to happen unless severe overcharge or someone shorts the terminals.  Even then, a sealed battery might not let enough hydrogen escape to do anything.

I wasn't worried at all about batteries inside until Craig mentioned it.  I wanted to see what others think.  I have seen warnings to still vent AGMs in the rare case they do vent some hydrogen.

Craig is going to look at my bus to see if we can't find a good place to put my flooded batteries so I don't have to spend $1,600 plus tax on AGM batteries.  I could pay someone to build a rack or shelf for the batteries and buy a entirely new set of flooded batteries and come out money ahead.

[Nick Badame Refrig/ACC]

Hi Brian,

You most likely allready know this, but, I thought I would remind ya..

Just remember to keep within the maximun distance between the bank and your inverter.

Nick-

[gumpy]

... Craig Shepard is telling me I shouldn't do it for safety reasons. 

That's not quite what I said. 

You told me you were fixing to spend a considerable amount of money on AGMs to replace a perfectly good set of golf carts primarily because you were having trouble finding a place to relocate them. I said I was not a big fan of large batteries being located in a living space, regardless of their construction. I know it's done. It's just not my ideal method.

One reason I'm reluctant is, as I fully admit, I know very little about AGM batteries. It's just not something I've ever had the opportunity to work with and get educated about.

Another reason is that I thought I recalled having heard that AGMs are somewhat particular to charging profile and easy to damage if charged improperly. I may be all wrong on the charging thing, but I'd sure hate to hear you burned up your expensive batteries because something failed or got unplugged or whatever.

If Sean says it's ok to put them inside, that's good enough for me. I still think before you drop a chunk of change on them we should see if we can't find a better location to put the others first.

I'm also not a big fan of mounting water tanks under the bed, but that's another personal preference with it's own particular reasons...

craig

[belfert]

Any new location for the batteries is almost certainly better for cable length than I have now, and yes I did think about this.  I'm using 4/0 cablle with a 24 volt inverter and I am probably a bit over the length for 4/0.  I should probably be at 350 MCM, but the 4/0 was sold cheap by a friend who had it just sitting in his garage.  He sold me the cable for just about scrap price 18 months ago.

[belfert]

Craig, I'm certainly still open to moving the current batteries.  I haven't settled on new AGMs yet.  The money for the batteries could be better spent on other stuff to get my conversion a lot closer to finished.

Your one email talked about safety and cost and your other email said you're not a big fan of large batteries inside.  I just wanted to see if others would also have safety concerns about AGM batteries inside the bus.

Thanks in advance for agreeing to look at my bus.

[Sean]

Another reason is that I thought I recalled having heard that AGMs are somewhat particular to charging profile and easy to damage if charged improperly. I may be all wrong on the charging thing, but I'd sure hate to hear you burned up your expensive batteries because something failed or got unplugged or whatever.

Craig,

I think you might be thinking of gel batteries (AKA gelled electrolyte batteries) rather than AGM.  Gel batteries, which are a different type of sealed deep-cycle battery, are indeed very sensitive to charge profile.  Gel batteries require chargers with appropriate settings for them, specifically, the maximum charge voltage is somewhat lower than for flooded cells.

AGM's, on the contrary, work just fine on flooded-battery charge profiles.  Thus they can be used as direct drop-in replacements for flooded batteries without any modification to charging systems.  Moreover, AGM batteries actually stand up much better to abuse than flooded cells.  They can also be charged much faster -- flooded cells should be limited to about 20-25% of their amp-hour capacity in an hour (IOTW, charge a 100 aH battery at no more than 25 amps) whereas AGMS are typically charged at 50%-100% of their capacity in an hour.  The only restriction is that AGM batteries should generally not be "equalized" or subjected to equalization settings, so any equalization mode on the charger should be disabled when using AGM batteries. (Most chargers require manual intervention to equalize -- so just don't do it, or change the equalization voltage setting down to be the same as the bulk setting to be safe.)

Brian:

Bear in mind that you will need about 1.6 times the rated capacity in flooded batteries to equal the same capacity in AGM batteries.  That's because flooded batteries should be discharged to at most 50% of rated capacity, while AGM can routinely be discharged to 20% capacity at about the same life cycle.  This is one of the big factors that makes the lifecycle cost calculations for AGM vs. flooded more difficult than it first appears -- it's not a slam-dunk in favor of flooded as many people believe.

If you are limited on space, even if they go in a bay, you might take this into consideration.

I have 920 amp-hours (at 24 volts) of AGM batteries.  They weigh 1,200 lbs and take up all the space available in my battery area.  To get the same usable capacity in flooded cells, I would need 1,470 amp-hours weighing over 1,900 lbs.  I'd have to move them outside, which is a good thing because I don't have room for another four 8D's in my battery area today.

Of course, if you already own a bunch of flooded batteries with good life remaining, the economics probably do not justify changing them out without some other mitigating factor.

FWIW and HTH.

-Sean
http://ourodyssey.blogspot.com

[belfert]

Sean, the only reason for going to AGM batteries would be to move them inside.  My exisiting flooded batteries work okay, but not great.  I think I should be getting more run time out of my 450 AH at 24V, but I don't have an amp usage monitor either.

My batteries are currently on a tray on the engine compartment, but they block access to air compressor and need to be moved.  I really don't want to take up bay space and would spend the money on AGMs before taking up bay space.

[gumpy]

You were right to post your questions here about the safety concerns. As I said, this is an area I don't know a lot about.

Sean is probably correct in that I'm confusing AGMs with gels regarding the charging issues.

I just didn't want people to get the impression that it may be bad just because I express my reservations about it. I find that when I don't know much about something, I usually proceed with caution. That shouldn't be construed as meaning it's necessarily bad.

craig

[Devin & Amy]

Belfert,

I had 4-8D's in a bay and with Mr. Murphy and a bit of inexperience I blew one of them up. I decided to put in AGM's not only for their safety, but also for their ease of use and maintenance.
I put 6 inside my evaporator chamber, deep within the belly of the bus. I did not want ANY hydrogen issues in this location. I installed a small thermostatically controlled "breadfan" to vent the heat and gases from this chamber. If I had stayed with the flooded cells I would not have been able to use this area, it has openings that would allow gas to rise into the cabin, plus the spark factor.
As for the charging issues, I don't know of any. We have been full on the road for the last 7 months with no issues whatsoever. I have my SW4024 programmed as normal for flooded cells but with equalization disabled.
They are heavy though, I don't know how much heavier than golf cart batteries though.
Kinda spendy too, $2400 for mine.
HTH
Devin

[HB of CJ]

You probably can, but I would not.  Lots of bad things can happen with heavy batts inside the coach.  Also lots and lots of dead short potential.  Your decision.