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Battery Explosions

bruce morgans

Joined: 21-01-05

Topics: 6

Replies: 18

Posted: Mon 19th May 2014, 9:00pm
Battery Explosions

Hi Does anyone have any experience/knowledge of battery explosions due to either overload/short circuits or over charging when connected in parallel with a motor generator/alternator and if so what advice can they offer to prevent such an occurrence.

Regards Bruce
 

Replies To This Post

Xz

Joined: 1-01-92

Topics: 17

Replies: 244

Posted: Sat 24th May 2014, 9:22am

I have no experience of battery explosions, but I do know it's never a good idea to charge two batteries in parallel, as even identical makes will have minorly differing internal resistances and the weaker one will overcharge and the higher one not enough. This has been dealt with properly by the caravan people.
 

ivanhewlett

Joined: 1-01-85

Topics: 8

Replies: 53

Posted: Tue 27th May 2014, 11:47am

Hi Bruce

First of all I would say that I totally understand your concerns, a battery, particularly of the size we use, is a dense store of energy and it must be treated with respect, however....
Modern batteries are very safe, I have a story I can tell you if we meet of a recent event that proves this.
I am afraid that in this case, I do have to disagree with Xz regarding paralleling of batteries, from practical experience with my 5 year old 24 volt P/E. I have 4 batteries in series parallel combination connected to a 24 volt alternator without any problems.
The heavy cables from each battery pair (I use jump leads) are taken directly through 60 Amp mains rated MCB's for short circuit protection. I also leave the batteries paralleled at all times (except when in my trailer) and also leave a 5 Amp mobility charger connected to them when not in use.
The batteries are leisure types and were all bought new at exactly the same time and are still working well at present.
I am happy to provide more info. if you wish ?

A comment I would make in respect of Xz's comments is that caravanners have done a lot of work on the subject, but it is likely that this would not be with permanently connected batteries of similar age and size etc. Whereas in our use for locomotives we can typically ensure that this is the case.

Cheers, Ivan.
 

rogerbrown

Joined: 1-01-85

Topics: 6

Replies: 35

Posted: Tue 27th May 2014, 10:15pm

Hi Ivan

It may be worth speaking to Paul Middleton as he has commented to me about certain types of batteries and if my poor old memory serves me correctly it was lithium Ion bateries going Kaboom in certain circumstances and apparantly there are clips on U tube of it happening.

Regards

Roger
 

ivanhewlett

Joined: 1-01-85

Topics: 8

Replies: 53

Posted: Wed 28th May 2014, 9:46am

Hi, Roger, Bruce and all

Fair point Roger. I should have made it clear that I was talking purely about traditional lead acid batteries and my comments are not applicable to other technologies.
My projects are all based around automotive, leisure or marine electrical equipment and at present this means alternators designed to work with lead acid batteries.
An alternator is really a three stage device, the generator - stator and armature, the rectifier - diode packs and the regulator - a voltage controller.
It is very possible to make an alternator capable of charging Li-Ion or other battery types, but this would require a very different regulator and I think you would struggle to find one set up as such, although it would be quite possible to construct one.

However at present unless you really know what you are doing it is safest to assume that a typical alternator will work perfectly with the correct value of lead acid battery stack. By battery stack I mean for a 12 volt alternator a single 12 volt battery, for a 24 volt battery two 12 volt batteries in series.

As an aside it is always advisable to have batteries connected whenever the alternator is being spun to avoid overvoltage failure risk - I stand to be corrected on this point though ?

A 12 volt battery is only nominally 12 volts, at rest if in good condition and fully charged somewhere around 12.4/12.5 volts might be expected. When charging the voltage may rise to around 14.4V, or higher. So when putting two batteries in series don't worry if you see 28 or 29 volts reached while charging.
This additional voltage means that you get a little bit more power out of your traction motors when it's needed.
The next voltage step up from this is three batteries in series, nominally 36 volts, but in this case the measured voltage on charge can be as high as 44 Volts under perfectly normal conditions.

If anyone is experimenting with Li-Ion as a traction battery - or any other chemical technologies - I would love to hear, but unless you are very confident then as Roger says, be careful.

Cheers, Ivan
 

Puffernutter

Joined: 1-01-70

Topics: 0

Replies: 1

Posted: Tue 3rd Jun 2014, 10:07pm

Not directly connected with miniature locomotives, but I have had two lead acid car batteries fail when on charge. One I think was due to an internal short circuit and it made a reasonable mess, the other just cracked across one end and not only let the smoke out, but the acid as well!
Cheers
Peter
 

ivanhewlett

Joined: 1-01-85

Topics: 8

Replies: 53

Posted: Thu 5th Jun 2014, 11:21am

Hi Peter
That's interesting reading.
I am beginning to think that there are a lot of similarities between the batteries in an electric locomotive and the boiler on a steamer.
They are both the energy store mechanism and they both benefit, or suffer, from their treatment and other factors.
For example some people prefer to leave their boilers empty, while others fill to the brim, likewise some people prefer to keep their batteries on permanent charge ( me for one ) while others top up occasionally.
I would be interested in knowing which method was applicable to your batteries and also whether you used a 3 stage charger, or a simpler type ?
I am not looking to pass judgment, or say that one way is better than another, but simply to try and set Bruce's, and others, minds at rest that actually lead acid batteries are a relatively safe and easily maintainable source of energy for miniature locomotives.
Any learning on this subject is valuable and in fact with the increasing availability of Li-Ion and other battery types, with a much higher energy storage density, understanding how to maintain them safely is increasingly important.
Indeed there is at least one commercial supplier offering a supercapacitor option for electric traction and this is very interesting, but I have personally witnessed much smaller electrolytic capacitors explode and it is not something I would wish to experience in my model. Perhaps these capacitor systems relate more directly to flash steam boilers ?
All perfectly manageable and safe if treated correctly and I guess that is my point in this response.
Cheers, Ivan.
 

George

Joined: 27-01-10

Topics: 0

Replies: 20

Posted: Thu 5th Jun 2014, 6:18pm

Hi all,
As for charging batteries, one should allways use a proper battery charger. With that I mean a 3 stage or 4 stage suited to your battery. There are seperate charger for gel (AGM) or wet batteries. It should be set correctly for your end of charge, for this see the datasheet of the battery. When charging from an alternator keep a check on your fluid level from time to time. One main thing, try to stay away from the cheap chargers and if you have to use them don't leave them on. With a 3 or stage charger you can happily switch them on and leave and with the trickle charge they will keep them in optimum condition especially the gel batteries. Wet batteries allways need extra care.
Regards
George
 

alan

Joined: 23-10-04

Topics: 0

Replies: 9

Posted: Tue 21st Oct 2014, 1:56pm

hello,to you all;I have some experience gained on the heavy duty battery banks used in picture house emergency lighting installations,fork lift trucks,solar generation,large scale fire alarms and the like:
Regarding parallel connection of batteries,it is generally held to be bad practice;all batteries have an internal resistance,this varies on a lead acid cell with state of charge and ageing,eventually one cell will loose charge by discharging through the lower resistance of a neighbouring cell,resulting in poor performance,and premature failure;the position is made worse by uneven charging due to the different resistances. If parallel operation is unavoidable,then arrangements should be made to open circuit the batteries when off duty,and preferably charge each battery with a separate charger of appropriate specification.Series connected sets will benefit from this type of charging too. Note the manufacturers advice should be followed to the letter,some batteries like constant current,some constant voltage etc.and charging currents are generally specified.
some'Open'lead acid batteries like a 'gassing' charge(a short overcharge making all cells bubble)from time to time,this slows the sulphation that ages the battery,restores performance and extends life,but it should be strictly controlled,and again,be to manufactures spec.
At no time should a battery be left in a discharged condition,and they should be protected from frost.
Explosions:the only explosions I know of in large lead acid batteries have been due to the charging gasses (a handy mix containing mainly hydrogen and some oxygen) being ignited ,possibly by careless charging connection,or in one case,when a metal bar was dropped across the terminals,either case is dangerous,hot acid flying around the room etc.
please remember there are many types of lead acid battery,all made for different duties,and all requiring their own particular maintenance schedules,and Ivan,you are correct,as a large power storage device,there are similarities with boilers and air receivers,batteries should be treated with equal respect, a sudden release of the power within can be devastating.
In my view,although expensive,the 'trojan' range of traction batteries are hard to beat for our sort of application.
remember,'very few batteries die of natural causes,most are murdered'
hope this helps....Alan 3651
 
 
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