PAS 63100 vs BS 7671 A721

AJJewsbury said:

A case in point is the position of the main battery fuse (or CB) - traditional caravan rules prohibit this entirely from the battery locker - presumably on the assumption that lead acid batteries are liable to liberate hydrogen gas and a fuse (especially the open automotive types) or a circuit breaker is very likely to create an arc when opening the circuit - and arcs and explosive hydrogen aren't a good mix. Maybe there's also a worry of acidic vapours from the battery corroding contacts. BS 7671 A721 agrees with that (A721.533.1.8). PAS 63100 on the other hand seems to take the opposite approach

Some good points made in the discussion, but one topic has been missed so far.

PAS63100 does not include systems using open vented lead-acid batteries within the scope of the document, Section 6.4 stipulates the applicable standards for cells/monoblocks which for lead-acid they have to be compliant with BS EN 61056-1; and BS EN 61056-2, which are standards for valve regulated lead acid cells (VRLA).

So open vented automotive lead-acid batteries which are releasing moisture and hydrogen during normal operation wouldn't be permitted under PAS63100. 

But strangely, they do include vented NICAD batteries (BS EN 60623) within scope. Which seems a rather bizarre choice.

For lead acid cells at least .the charging regime has to be more tightly controlled for the VRLA as there is no easy means to replace the lost water - and actually drying out is often a failure mode of smaller sealed cells in alarms and some emergency lihts.where they spend a long time on 'float' charge.

Circuits for vented cells at least historically have tended to approach full charge at a higher current for rapid cycling, and not bother too much about a degree of overcharging and a bit of gas.

The VRLA circuits ensure  that the charging current falls away to almost nothing as full charge is approached and far less gas is produced, unless the charging circuit is faulty or te battery overheats (the voltage per cell falls with temp so if the cell is hot, the charger behaves as if it is flatter than it is, and tends to overcook it.)

NiCd cells and the more modern but related Ni/MHs have the ability to catalitically  recombine the O2 and 2H2 back to water if they are constructed correctly, and can safely be constant-current over charged slowly, say 10-20 hour rate, almost for ever, and only gassing if badly abused by huge over current or voltage.

I suspect the apparent anomaly relates to the way the different cells are typically charged, and how much gas they then produce.

Mike

PS the humble car battery is more or less sealed for life these days, because of the improved all electronic regulation inside  the modern alternator - anyone old enough to have suffered a mechanically regulated dynamo will recall topping up the battery and checking the acid density was a regular fortnightly ritual. folding beck the current as full charge is reached avoids that conversion of water to gas then having to replenish it, 

mapj1 said:

NiCd cells and the more modern but related Ni/MHs have the ability to catalitically  recombine the O2 and 2H2 back to water if they are constructed correctly, and can safely be constant-current over charged slowly, say 10-20 hour rate, almost for ever, and only gassing if badly abused by huge over current or voltage.

I believe you are referring to sealed cells, which are a different design to vented NiCads, to BS EN 60623 these are akin to the wet / flooded lead-acid batteries, with liquid electrolyte, large plates, in a plastic case with a vent. 

The small Ni XX cells certainly only vent if distressed and cannot be refilled, I agree, but as far as I know the modern vented cap type cells as seen on some forklifts etc can also be trickle charge indefinitely at low constant current without significant gassing or needing topping up.

It may be a deliberate decision to fast charge I suppose and then suffer the penalty of the top up routine -I'm really not too sure what is done in a mains connected battery storage units - Ive only seen Lithium in newer sets and lead in older ones.

M

TurboGen said:

PAS63100 does not include systems using open vented lead-acid batteries within the scope of the document, Section 6.4 stipulates the applicable standards for cells/monoblocks which for lead-acid they have to be compliant with BS EN 61056-1; and BS EN 61056-2, which are standards for valve regulated lead acid cells (VRLA).

Correct ... are there any standards for VLA batteries for stationary secondary battery purposes?

The reason I ask, is that BS 7671 (and hence, by reference to BS 7671, PAS 63100) requires 'electrical equipment' which by definition includes batteries, to conform to a relevant British or Harmonized Standard, and it's an 'intended departure' if the equipment does not conform to such a standard, or is used outside the scope of its product standard (e.g. traction secondary battery repurposed as a stationary secondary battery until such time as there's a standard of repurposing the relevant battery).

gkenyon said:

Correct ... are there any standards for VLA batteries for stationary secondary battery purposes?

Absolutely, vented lead acid stationary secondary batteries are still relatively common in some industries, they are typically used for standby/UPS purposes (as an alternative to VRLAs) to provide secure supplies to critical systems and equipment. They come in very large capacity sizes and are more robust and durable than VRLA types, but are typically more expensive and require more space, they also require some maintenance. These are batteries specifically designed and specified for stationary operation, they are not re-purposed automotive batteries.

BS EN 60896-11:2003 Stationary lead-acid batteries. General requirements and methods of test Vented types. General requirements and methods of tests

BS 6290-2:1999 Lead-acid stationary cells and batteries - Specification for the high-performance Plante positive type

BS 6290-3:1999 Lead-acid stationary cells and batteries - Specification for the flat positive plate type

gkenyon said:

The reason I ask, is that BS 7671 (and hence, by reference to BS 7671, PAS 63100) requires 'electrical equipment' which by definition includes batteries, to conform to a relevant British or Harmonized Standard, and it's an 'intended departure' if the equipment does not conform to such a standard, or is used outside the scope of its product standard (e.g. traction secondary battery repurposed as a stationary secondary battery until such time as there's a standard of repurposing the relevant battery).

As above, there are standards but I was making an assumption that the authors of PAS63100 had consciously excluded vented lead acid cells after weighing up their suitability for energy storage in domestic dwellings - the presence of liquid electrolyte which can leak, venting hydrogen during charging, need for periodic maintenance and top-ups, all of which combine to arguably making them unsuitable for use, in significant quantities, in domestic applications by unskilled persons.

It was those same factors which made me rather surprised to see PAS63100 included systems with vented NiCaDs within scope. 

[Edit] I should add, this topic is largely academic, realistically I doubt any home energy storage products intended for domestic dwellings would be designed with vented cells, they're almost certain to be entirely sealed cells, currently lithium-ion and probably sodium-ion in the future. More due to the considerations of energy density, cost, and suitability for long term operation at partial states of charge.

gkenyon said:

Correct ... are there any standards for VLA batteries for stationary secondary battery purposes?

Absolutely, vented lead acid stationary secondary batteries are still relatively common in some industries, they are typically used for standby/UPS purposes (as an alternative to VRLAs) to provide secure supplies to critical systems and equipment. They come in very large capacity sizes and are more robust and durable than VRLA types, but are typically more expensive and require more space, they also require some maintenance. These are batteries specifically designed and specified for stationary operation, they are not re-purposed automotive batteries.

BS EN 60896-11:2003 Stationary lead-acid batteries. General requirements and methods of test Vented types. General requirements and methods of tests

BS 6290-2:1999 Lead-acid stationary cells and batteries - Specification for the high-performance Plante positive type

BS 6290-3:1999 Lead-acid stationary cells and batteries - Specification for the flat positive plate type

gkenyon said:

The reason I ask, is that BS 7671 (and hence, by reference to BS 7671, PAS 63100) requires 'electrical equipment' which by definition includes batteries, to conform to a relevant British or Harmonized Standard, and it's an 'intended departure' if the equipment does not conform to such a standard, or is used outside the scope of its product standard (e.g. traction secondary battery repurposed as a stationary secondary battery until such time as there's a standard of repurposing the relevant battery).

As above, there are standards but I was making an assumption that the authors of PAS63100 had consciously excluded vented lead acid cells after weighing up their suitability for energy storage in domestic dwellings - the presence of liquid electrolyte which can leak, venting hydrogen during charging, need for periodic maintenance and top-ups, all of which combine to arguably making them unsuitable for use, in significant quantities, in domestic applications by unskilled persons.

It was those same factors which made me rather surprised to see PAS63100 included systems with vented NiCaDs within scope. 

[Edit] I should add, this topic is largely academic, realistically I doubt any home energy storage products intended for domestic dwellings would be designed with vented cells, they're almost certain to be entirely sealed cells, currently lithium-ion and probably sodium-ion in the future. More due to the considerations of energy density, cost, and suitability for long term operation at partial states of charge.

TurboGen said:

Absolutely, vented lead acid stationary secondary batteries are still relatively common in some industries, they are typically used for standby/UPS purposes (as an alternative to VRLAs) to provide secure supplies to critical systems and equipment. They come in very large capacity sizes and are more robust and durable than VRLA types, but are typically more expensive and require more space, they also require some maintenance. These are batteries specifically designed and specified for stationary operation, they are not re-purposed automotive batteries.

Those applications, though are:

• Not domestic (i.e. outside the scope of PAS 63100); and
• Outside the scope of Chapter 57 of BS 7671, as with those applications, the larger 'system' is covered by other standards, see scope of Chapter 57, and scope of BS 7671 in general.

TurboGen said:

As above, there are standards but I was making an assumption that the authors of PAS63100 had consciously excluded vented lead acid cells after weighing up their suitability for energy storage in domestic dwellings - the presence of liquid electrolyte which can leak, venting hydrogen during charging, need for periodic maintenance and top-ups, all of which combine to arguably making them unsuitable for use, in significant quantities, in domestic applications by unskilled persons.

Indeed, given the scope is domestic. The applications, as above, are probably also mostly outside the scope of Chapter 57.

TurboGen said:

BS EN 60896-11:2003 Stationary lead-acid batteries. General requirements and methods of test Vented types. General requirements and methods of tests

BS 6290-2:1999 Lead-acid stationary cells and batteries - Specification for the high-performance Plante positive type

BS 6290-3:1999 Lead-acid stationary cells and batteries - Specification for the flat positive plate type

So, those standards really should not appear in PAS 63100, and would rarely, if ever, be considered for battery systems within the scope of Chapter 57?

gkenyon said:

Those applications, though are:

• Not domestic (i.e. outside the scope of PAS 63100); and
• Outside the scope of Chapter 57 of BS 7671, as with those applications, the larger 'system' is covered by other standards, see scope of Chapter 57, and scope of BS 7671 in general.

You asked specifically if there were standards for VLA cells for stationary secondary battery purposes - there are, and I listed some, the standards relate to the cells, not the application.

gkenyon said:

So, those standards really should not appear in PAS 63100, and would rarely, if ever, be considered for battery systems within the scope of Chapter 57?

Personally I would not include them, as I would judge vented lead-acid cells as inappropriate for use in domestic BESS applications by unskilled persons, due to a combination of the quantity of hazardous liquid electrolyte in the installation, venting of gases during normal charging and need for maintenance. The technical performance of lead-acid cell chemistry is also questionable given the operational requirements for a BESS type system to operate at partially charged states.

But following that same logic, I would question why the authors of PAS 63100 included within the scope vented NiCads "BS EN 60623 Secondary cells and batteries containing alkaline or other non-acid electrolytes. Vented nickel-cadmium prismatic rechargeable single cells", which are the NiCad equivalent of the vented lead-acid cells, so share many of those same hazards as VLAs, so personally I would not have included BS EN 60623 within PAS 63100. But again, I think it unlikely that vented NiCads would ever be considered, despite their inclusion in the PAS.