So If You Want To Ventilate The Battery Box .......

[William_H]

Hi Dave a simple VSR can be made from a few components.
Use a TL731 as a comparator and voltage reference. http://www.alldatasheet.com/view_datasheet.jsp?Searchword=TL431
It has a voltage of 2.5 volts ( less in some variants) when it starts to conduct current. So we set up a voltage divider 2 resistors in series with a connection between the 2 that goes to the reference pin such that at a voltage of about 13.5 going in to your divider (battery voltage) you get 2.5 volts which switches on the TL431. Actually you use a variable resistor with fixed resistors to give you adjustment over a limited range.
Now for one fan you could connect the fan between battery pos and the cathode of the TL431 with anode connected to negative. (these names will seem wrong because the device is meant to emulate a zener diode which has pos to cathode and begins to conduct at a set voltage in a breakdown in reverse so is wired in the non conductive direction for a diode) It will take a max .1amp.
Ok you could fit a small relay in the cathode to pos circuit or use a resistor in place of relay or fan. Connect the cathode to the base of an NPN power transistor collector to supply emitter to fans.
As a VSR this will not have the hysteresis built in to VSR for battery connections but that does not matter for our purposes.
It would help to have a variable voltage power supply so you can set up the actuation voltage at home.
PM me if you want more help. olewill

 

[vyv_cox]

I read somewhere (possibly on this forum) that hydrogen is pretty nippy stuff, and will readily find its way through modest openings

Indeed it is. Refinery hydrogen compressors are very carefully designed and specified to control the very small molecular size. A flanged casing that will suffice for modest pressures with other gases cannot be used, as no gasket or bolted joint can prevent the gas from leaking out. One-piece barrel casings that would normally only be specified for high pressures are standard for hydrogen, along with very special sealing technology.

 

[PaulRainbow]

Indeed it is. Refinery hydrogen compressors are very carefully designed and specified to control the very small molecular size. A flanged casing that will suffice for modest pressures with other gases cannot be used, as no gasket or bolted joint can prevent the gas from leaking out. One-piece barrel casings that would normally only be specified for high pressures are standard for hydrogen, along with very special sealing technology.

So my sofa won't contain it then Vyv ?

 

[JumbleDuck]

Still, not the sort of thing you want going on in the battery box under your bunk at 2am.

Indeed. It was more of a chemical quibble.

 

[JumbleDuck]

A thing that has occasionally puzzled me is that if hydrogen is given off during charging, presumably the battery needs to re-absorb hydrogen again when it is being discharged. Is this true? And if so, does the comparative reduction in hydrogen in the remaining air around the batteries have any notable qualities or issues?

The hydrogen and oxygen produced at the plates when charging come from the water in the battery. In old fashioned batteries they were vented to air, which is why car batteries used to need topped up. Nowadays most (I think) batteries contain a recombinant catalyst which joins them together into water again and tops up the cells for you. By the way, it was probably failure to take recombination into account which led Fleischmann and Pons to make such fools of themselves with their cold fusion claims.

There is negligible hydrogen in the atmosphere because, like helium, it is light enough to escape into space from the upper atmosphere. You need a very big gravitational pull (helloooooooooooo, Jupiter) to maintain a hydrogen atmosphere.

 

[Plevier]

Will an oxygen-hydrogen mixture explode (ie detonate - supersonic propagation, high overpressure)? I thought it would only deflagrate (subsonic propagation, low overpressure) but I could be wrong. I've blown up a balloon full of the stoichiometric mixture loads of times in shows, and that's a deflagration. Still pleasantly loud, though.

In my working days with a battery company I went to examine a 48V 2000Ah telephone exchange battery that had gone up with a bang when some clown dropped an uninsulated spanner on the main busbars while the battery was being equalise charged with the vent plugs out - that's a big no-no as the plugs include a flame arrestor, Davey lamp style. If you get external ignition, it can flash back into the container and ignite the very reactive stoichiometric gas mixture inside, and that happened here.

There were shards of 8mm thick SAN from the cell containers stuck in the plasterboard ceiling.

That's explosive enough for me! Are you being a bit picky about terminology?

 

[Plevier]

The hydrogen and oxygen produced at the plates when charging come from the water in the battery. In old fashioned batteries they were vented to air, which is why car batteries used to need topped up. Nowadays most (I think) batteries contain a recombinant catalyst which joins them together into water again and tops up the cells for you. By the way, it was probably failure to take recombination into account which led Fleischmann and Pons to make such fools of themselves with their cold fusion claims.

There is negligible hydrogen in the atmosphere because, like helium, it is light enough to escape into space from the upper atmosphere. You need a very big gravitational pull (helloooooooooooo, Jupiter) to maintain a hydrogen atmosphere.

Catalytic recombining vent plugs have been tried but never with much success. They degrade very quickly.
VRLA batteries, whether AGM or gel, do not use catalysis. Recombination depends on mobility of nascent gas through the unsaturated microporous separators in AGM or micro cracking in the gel type.

 

[Plevier]

See. http://rollsbattery.com/wp-content/uploads/batteries/S12-240AGM.pdf

You’ll have to wait some time (hopefully) for empirical feedback

A very ambitious claim. What are the warranty terms?

Who is it that you say claims 1500 cycles to 95%?

Have you noted that (in common with Trojan) the cycles Vs depth curve corresponds to a constant no of Ah from the battery over its lifetime?

This conflicts with the common view that deep discharges are proportionately more damaging than moderate discharges.

 

[JumbleDuck]

In my working days with a battery company I went to examine a 48V 2000Ah telephone exchange battery that had gone up with a bang when some clown dropped an uninsulated spanner on the main busbars while the battery was being equalise charged with the vent plugs out - that's a big no-no as the plugs include a flame arrestor, Davey lamp style. If you get external ignition, it can flash back into the container and ignite the very reactive stoichiometric gas mixture inside, and that happened here.

There were shards of 8mm thick SAN from the cell containers stuck in the plasterboard ceiling.

A chap I used to work for had, in his apprentice days, to tidy up the aftermath when some dropped a spanner into the bank of ex-submarine batteries used to power magnets at the GPO research labs (precursor of Qinetic) in Malvern. More a case of sweeping up shrapnel than trying to recover usable stuff, I gather.

That's explosive enough for me! Are you being a bit picky about terminology?

I'm a university lecturer. "Picky" is what I do. But there are significant differences between detonation and deflagration, and I'd be innterest to know if a H-O mixture ever does detonate.

 

[JumbleDuck]

Catalytic recombining vent plugs have been tried but never with much success. They degrade very quickly.
VRLA batteries, whether AGM or gel, do not use catalysis. Recombination depends on mobility of nascent gas through the unsaturated microporous separators in AGM or micro cracking in the gel type.

Thank you very much.

 

[Plevier]

A chap I used to work for had, in his apprentice days, to tidy up the aftermath when some dropped a spanner into the bank of ex-submarine batteries used to power magnets at the GPO research labs (precursor of Qinetic) in Malvern. More a case of sweeping up shrapnel than trying to recover usable stuff, I gather.



I'm a university lecturer. "Picky" is what I do. But there are significant differences between detonation and deflagration, and I'd be innterest to know if a H-O mixture ever does detonate.

Submarine batteries are pretty mighty things. As you can imagine everything is done to avoid explosions so GPO must have mismanaged them in some way.

I'm sure you are more capable than me of answering your question but a bit of reading suggests to me that it's deflagration. However as Collins dictionary says deflagration is an explosion anyway - am I bovvered?

 

[Dave100456]

A very ambitious claim. What are the warranty terms?

Ans
You'll need to look this up in the link http://rollsbattery.com/public/docs/user_manual/Rolls_Battery_Manual.pdf or on their website. From memory there are warranties for 3 to 5 years depending on the type 4000, 5000 etc.

Who is it that you say claims 1500 cycles to 95%?

Ans
I think this related to lithium, sorry can't find the link.

Have you noted that (in common with Trojan) the cycles Vs depth curve corresponds to a constant no of Ah from the battery over its lifetime?


This conflicts with the common view that deep discharges are proportionately more damaging than moderate discharges.
Ans

No, I hadn't noticed but would agree with your last point about deep discharges.

 

[Plevier]

Rolls warranty http://www.rollsbattery.com/wp-content/uploads/warranty/Warranty.pdf - 2years full plus 3 years pro rata, but I can't find their definition of failure to qualify for replacement.

Yes lithium will give more cycle life, not a fair comparison. Many times the price.

 

[JumbleDuck]

Submarine batteries are pretty mighty things. As you can imagine everything is done to avoid explosions so GPO must have mismanaged them in some way.

As I understand it, they had a great bank of the things and a substantial spanner shorted the lot. Not good.

I'm sure you are more capable than me of answering your question but a bit of reading suggests to me that it's deflagration. However as Collins dictionary says deflagration is an explosion anyway - am I bovvered?

The detonation/deflagration distinction is not something I'd worry too much about if I was going to be caught up in a substantial example of either ... I think, though I'm not at all sure, that to set off a detonation you need to create a shock wave with a detonator but that to set off a deflagration you just need heat, like a spark. Maybe. I think my Google search history is already quite dodgy enough for one evening.

 

[Dave100456]

Rolls warranty http://www.rollsbattery.com/wp-content/uploads/warranty/Warranty.pdf - 2years full plus 3 years pro rata, but I can't find their definition of failure to qualify for replacement.

Yes lithium will give more cycle life, not a fair comparison. Many times the price.

Apols if I did not make myself clear.

I wasn't trying to make a fair comparison and appreciate they (Lithium-ion) are different which is exactly the point I was making in relation to a previous poster's comment about "abusing" a battery.

I used an example of an extreme DoD and extreme cycle to try and illustrate that a 70% DoD can not be regarded as abuse unless you know the characteristics of the battery being subjected to that DoD.