24 volt battery charger

[Frithiof Andreas Jensen]

A robust charger takes lots of planning. Just ask Dell or Apple. ;-)

Note that I know (I think) all the pitfalls of a charger, and when I
needed one for home use, I just bought one off the shelf. ;-) Full uP
control and most of the protection I mentioned. Some manufacturers
(boards and chip level) put in protection modes not on the datasheet.
There are reasons not to mention the extra protection modes, but that
would be a paragraph or two more.

I just did that - DKK 200,-- yet again the manufactured product is
cheaper than the parts!

This One "AT1206" to be exact:
http://www.nordicpower.se/pdf/aviotec01.pdf (it is always nice but
sadly a rare event to be able to refer to an item on a web site - so I
shall take the opportunity).

 

[RHRRC]

They should, but also have enough battery capacity so that even in the
worst case, the voltage never drops to 1 V per cell.

The worst case is pretty easy to determine; it often isn't. The worst
case is the maximum time it would take to evacuate the building. If it's
empty, emergency lighting is not required. Some idiots specify that the
system capacity must be enough for 12 or 24 hours!

Yes that is correct.

It is absolutely imperative that none of the standards, code of
practice (not to mention legal requirements) appertaining to emergency
lighting are referred to when designing such equipment

It is, for example, far better to have a mickey mouse low battery drop
out circuit operating at a level determined by the local hippie
community rather than that given in the standard for the construction
of emergency lighting.

Sod the necessary slog of competent design - just get a good lawyer

 

[RHRRC]

They should, but also have enough battery capacity so that even in the
worst case, the voltage never drops to 1 V per cell.

The worst case is pretty easy to determine; it often isn't. The worst
case is the maximum time it would take to evacuate the building. If it's
empty, emergency lighting is not required. Some idiots specify that the
system capacity must be enough for 12 or 24 hours!

Yes that is correct.

It is absolutely imperative that none of the standards, code of
practice (not to mention legal requirements) appertaining to emergency
lighting are referred to when designing such equipment

It is, for example, far better to have a mickey mouse low battery drop
out circuit operating at a level determined by the local hippie
community rather than that given in the standard for the construction
of emergency lighting.

Sod the necessary slog of competent design - just get a good lawyer

 

[Frithiof Andreas Jensen]

Sod the necessary slog of competent design - just get a good lawyer

Exactly - for similar reasons one usually does *not* do any patent/IPR
searches as part of a design because it is cheaper if we accidentially
step over some toes than delaying product. That's the legal deparments
advice anyway - they all drive nice cars, probably ;-)