clearance height for batteries

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Glenn Brooks
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clearance height for batteries

Post by Glenn Brooks »

Hello All,

I’ve run into a simple design question for battery powered locomotives. But can’t find any specifications on line.

Anybody know if their is a recommended minimum clearance height for heat disaptation or other safety issues for stacking 12 v lead acid batteries on top of each other?

The circumstances are that I’ve built a battery box to hold four 12 v batteries to drive a 48v motor. I wish to stack two batteries on the bottom and 2 batteries on top. What Should be the minimum open space between each layer ? Iam thinking maybe 2” for ventilation and wiring clearance... but haven’t found any recommendations on line,,, or determined even if this matters...

Thanks,

Glenn
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Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

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Harold_V
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Re: clearance height for batteries

Post by Harold_V »

I suspect your 2" clearance is adequate. What's far more important is that you provide proper ventilation, so hydrogen doesn't accumulate. That can ruin your whole damned day!

H
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John Hasler
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Re: clearance height for batteries

Post by John Hasler »

Two inches will be adequate. With only four batteries just make sure that there *is* ventilation and you'll be ok.

Hydrogen only comes off during charging. I did the electronics for a medical standby power unit that had four turck batteries in a stainless steel box. The project engineer was concerned about hydrogen accumulation so he did the calculations, He found that something like a 1/2" opening at the top would prevent an explosive mixture from accumulating even under severe overcharge.

Cooling is rarely a problem with lead-acids due to their low power density. Even forklift batteries usually have no special cooling.
Glenn Brooks
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Re: clearance height for batteries

Post by Glenn Brooks »

Harold and John, thanks for your prompt replies. This will help greatly in finishing off the battery boxes this afternoon.

Should have asked, Would this matter if I latter converted to lithium? (Possible future plan.)

BTW, I had a battery blow up once, on my fishing boat. Fortunately it was completely enclosed in a heavy fiberglass battery box, with a proper lid. So no external mess. Just A big, deep throated WHOOMP, while underway. And half dozen pieces of the battery laying in the box. Quite a surprising experience. In the fishing industry, there is a larger risk of the battery vent itself becoming clogged through corrosion and marine particulate build up, causing the battery to explode from within, rather than hydrogen exploding externally - assuming you have a ventilated compartment.

Glenn
Moderator - Grand Scale Forum

Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....
John Hasler
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Re: clearance height for batteries

Post by John Hasler »

>Should have asked, Would this matter if I latter converted to lithium? (Possible future plan.)

Yes. With lithium cooling is a major consideration.
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NP317
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Re: clearance height for batteries

Post by NP317 »

But Lithium batteries are also likely to be a smaller package for more storage capability,
= more cooling volume.
And by the time you wish to use Lithium batteries there will be another chemistry available with more energy density,
lower internal resistance, and far faster charge times. Prototypes are already being tested.
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neanderman
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Re: clearance height for batteries

Post by neanderman »

John Hasler wrote: Mon Aug 30, 2021 12:21 pm
Yes. With lithium cooling is a major consideration.
But a couple of muffin fans should be sufficient.
Ed

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John Hasler
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Re: clearance height for batteries

Post by John Hasler »

With lithiums don't rely on "should be sufficient". Do the calculation.
Glenn Brooks
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Re: clearance height for batteries

Post by Glenn Brooks »

Yes, the lithium world is rapidly changing. A local guy now supplies used Gen 2 battery packs out of Nissan’s Leaf. Comparable in price to lead acid, for the equivalent power density you get. Also, lots of import DIY battery cells available. Bit I need to learn more about the chemistry and fairly sophisticated battery management systems before I convert.

One interesting aspect- the added weight of old school lead acid batteries improves traffic effort. Lithium is half the weight on drivers, so actually a bit of a negative for locomotive performance.

I’ve been planning on a fan or fans for the battery compartment cooling. compartments, actually, I have two on the But have added louvers for cooling. Also,learned lithium cells also need wall support, as the cells swell when in use. Sometimes can rupture, if not properly supported.

The local EV enthusiasts recommend fan cooling on their vehicle conversions, but so far no one has mentioned calc’s or a formula to determine needed air flow. Something definitely to look into...

Glenn
Moderator - Grand Scale Forum

Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....
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