Starter Batteries for Gen-Set

[jbond]

I believe that when batteries are charged, they produce Hydrogen Gas (I am talking of the common electrolyte batteries used in trucks etc).

If these batteries are being used for a starter motor on a gen-set, and if the batteries are located right next to the gen-set itself, and if they have a local isolator switch nearby on the cabling, then I presume that there is a Hazardous Area risk (risk of explosion) correct?

I've had a little bit of H.A. training before, so I know that I could make that isolator H.A. rated. However, those batteries are right next to the switch and the alternator. A better approach for me, would be to change the battery for a different type that doesn't produce hydrogen gas (for example the 3rd generation batteries called "AGM" - I don't know what that means but 2nd generation was gel and they are bigger in size usually whereas these AGM batteries are smaller and lighter) however this will cost more, and if management aren't happy with it then I will need an alternative solution.

Alternatively, I can determine the size of the H.A. boundary so that I ensure all electrical equipment posing as an ignition source is located outside of that boundary. However, this isn't easy to determine, because how much gas is produced? The guy working for the company that makes the batteries doesn't even know - its dependent on how much you are overcharging the battery and I guess what type of ventilation you have.

Does anyone here have any experience in this? Or have any comments or suggestions for me? I'd really appreciate it.

Thanks,
Matt.

 

[itsmoked]

mhumble: The amount of hydrogen normally produced is so low and as hydrogen is MUCH lighter than air does not easily collect nor hang around the engine. The concentrations rarely get anywhere near high enough to warrant H.A. rated switch gear.

Cars have batteries under the hood with lots of solenoids, starter motors, alternator brushes. etc. etc. The last several billion vehicles have not had problems with this.

Now if you have a tightly enclosed area there could be concern but generally you can't have an internal combustion engine in a tight space.

 

[mc5w]

Ideally, this application should not use sealed batteries. What you need are conventional batteries or maintainable "maintenance free" batteries that are of low water consumption.

If the battery tops are kept clean so that there is very little self discharge, the batteries need to be equalized about 2 to 4 hours per month. This is a deliberate overcharge that gets brings up cells that have self discharged more than some others. Typically, for a 12 volt 50 ampere hour lead acid battery you need 15 volts and a few amps tapering off to 16 volts and 1/4 amp to equalize. This does generate some hydrogen and oxygen and uses some water.

You should only add water when the battery is fully charged. The electrolyte volume is greatest when the battery is fully charged. If you overfill the battery the electrolyte tends to bulbble up onto the top surface and then causes excessive self discharge.

 

[alehman]

Vented batteries mounted on racks next to the engine is a nearly standard configuration. So far as I know (I've been involved with over 100 installations), there has never been a problem with hydrogen. I did come across one local building official who questioned it, but he was eventually convinced there was no problem.

Lead-acid and nickel-cadmium are both used commonly. Low-maintenance (calcium alloy) lead-acid or nickel-cadmium have the lowest hydrogen production.

 

[ccjersey]

I would recommend always have the batteries in a battery box with somekind of lid but with plenty of ventilation/blast holes in the box. I just recently had 1 of 2 12V 960 CCA lead acid batteries explode while I was starting a 24V backup generator. Judging from the surviving one, the electrolyte was very low. There was a heavy curtain between me and it, but it was still impressive from about 3 feet away. Wouldn't want to be in the blast zone. This is actually the second one for that generator in about 10 years.

Jim

 

[mc5w]

Come to think of it, you could permanently install some jumper cable that would use a big knife switch ( enclosed or open ) between adjacent 24 volt batteries.

I know that with some of the generator sets that Cummins makes have a way to put the electric starter motor on either side of the generator. This would make your permanent jumper cables rather short. How this can be done is that the engine has 2 places for hooking up a starter motor so that you can use both an air starter and an electric starter on the same engine.

If you go with air motor as an alternate starting method you could use a gasoline or diesel air compressor as the backup source of compressed air. You need to have a rather large air tank for this application and a rather large main pipe from the air tank to the generators. I have been told that air starters sound like an an incoming artillery shell exploding.

 

[itsmoked]

mc5w; They sound great indeed.

ccjersey; Sounds like fun. What happens is the electrolyte gets low. The plates dry out and then the conductive plate material falls across the cell shorting it out. When the huge starter current comes ripping thru that plate material literally explodes like a flash bulb. This sets off the hydrogen around it inside the cell. Case fails.

 

[DGCYS]

We use many L.A. batteries here for inverter testing. They are subject to high amp rapid charging. We constructed plywood boxes around them and use 2" pvc pipe to vent them outside.
a small fan could be added for long distance

DGCYS

 

[mc5w]

One purpose of a battery box is to provide extra electrical insulation for protection against dropped metal bojects such as wrenches. The lid should be in hinged sections to that you can work on 1 battery at a time with teh others protected.

Shorting out a 12 bolt car battery can be quite spectacular. The kind of 24 volt starting battery for a big diesel generator can also produce explosive short circuit.

If you are using batteries in parallel such as for a big diesel generator you might want to think about putting in some 2 pole switches ( 1 pole hot other pole in grounded side ) so that you can isolate a series string when servicing it such as when taking apart and cleaning the terminals. This would limit the available short circuit hazard and keep you from becoming a part of a high current circuit if the engine should start.

Barehanding 24 volts in the rain has a bit of a sting to it. I have also allowed enough perspiration salts to build up on my hands that a 1.5 volt D cell would give me a nasty shock.

 

[ScottyUK]

mc5w,

You need to see what happens when a 1430AH 110V flooded cell battery gets shorted. Electrolyte boiling, white light coming out of electrical panels, conductor insulation on fire...

We tend to use a PVC shroud designed to fit closely over the cell terminals and the interconnecting busbar. It provides good protection from the dropped wrench problem and reduces the chance of a shock to ground if the battery has a standing ground fault.

On big batteries the dropped wrench problem is best avoided by using insulated tools.



----------------------------------

If we learn from our mistakes,
I'm getting a great education!

 

[itsmoked]

I wanna see! I wanna see! (from a distance).

Now think diesel electric submarine. Man!

 

[ScottyUK]

Up close it is just plain scary. Trust me.


----------------------------------

If we learn from our mistakes,
I'm getting a great education!

 

[mc5w]

It does not hurt if the battery box provides redundant insulation in addition to the covers over the battery terminals and cell connecting straps.

1 good material for a box cover is ultra high molecular weight polyethylene. It is very acid and abrasion resistant. Plexiglass is about the worst material and in fact we used plexiglass scraps from the school shop for lighting fires back in Boy Scouts.

Also, if you are using circuit breakers for isolation and overcurrent protection for a battery bank there should be a common trip pole in the grounded conductor between the battery and the bond to the equipment grounds and grounding electrodes. This way, a ground fault in the battery bank will be sensed and disconnected and the bank will be less hazardous when servicing it.

ScottyUK,

One of the things that I would do with a 60 volt or higher voltage battery is to have some removable links for breakingit into 24 volt or 36 volt pieces. This makes servicing a lot less hazardous.

 

[ScottyUK]

mc5w,

Yes, I agree it is good practice.


----------------------------------

If we learn from our mistakes,
I'm getting a great education!

 

[ruggedscot]

Gel batteries series / parallel combination supplying 480/500v dc to power a UPS set. Diesel engine with two starter motors and two 24v highcurrent batteries one located each side of engine. Nothing like a good well thought out UPS set.

Loss of power = Game over......

Rugged