[LINK] Why a battery ? [Was: Re: Batteries again [Was: Future of Telecommunications in Canberra]]

Harry McNally harrymc at decisions-and-designs.com.au
Thu May 19 11:14:42 AEST 2011


Hello Tom

On 19/05/11 06:48, Tom Worthington wrote:

> Having technicians replace the batteries in FTTP equipment should make 
> recycling easier. The replacement can be scheduled (with the option of 
> the network reporting on current battery health) and old batteries put 
> through a recycling scheme in bulk. This is better than customer 
> installed batteries where you cannot be sure what they do with the old 
> batteries.

Good point but I wonder if battery health monitoring electronics is specified
for the NTU. Battery life will depend on a number of factors including float
voltage, cycles, depth of discharge, and ambient temperature. Measuring SLA
battery health needs more than the voltage and trickle current.

There would be a cost trade-off between periodic replacement of all batteries
based on typical lifetime and labour costs for access to single premises to
change batteries sensed as end of life.

> A bonus might be that the network could provide some smart grid 
> functions. If the system reports when mains power fails, then this can 
> be used to plot problems with the electricity grid. As Robin Eckermann 
> pointed out in a Smart Grid talk, at present the power company only 
> finds out a customer has no power when the customer calls to complain. 
> The company then has to send people out in a truck to drive along the 
> transmission line to see where the break is: 
> <http://blog.tomw.net.au/2011/03/smart-grid-energy-revolution-for.html>.

The power companies presently install a private wireless network from customer
"smart" metering to the substation. With the NBN plans, has any utility
considered metering over VPN on the NBN ?

>> ... landline is not our only (nor, in an emergency, 
>> our best) option, is the convenience worth those costs?  ...
> 
> The average householder is going to expect that their new NBN
> connected phone service is at least as good as the service it
> replaced. In theory a combination of mobile phone and land line without
> backup could be as reliable (or better), but dealing with the political 
> consequences would not be easy. It would only take one dead pensioner, 
> found with a non-functioning NBN phone in their hand, for an expensive 
> retrofit of battery backup to be ordered by the government.

Is a battery the best solution ? If customers have UPS to keep computers etc
alive during power outage then they can also accept responsibility to power
the NTU with the UPS. The NTU mains wiring would need to allow this. The
customer maintains their computer UPS health to whatever standard they choose.
Why maintain NBN services if there is no mains power ?

In the absence of mains power, the NTU could drop back to very low power and
only operate the landline. This could be done with a smaller longer life
battery (different chemistry) or possibly a supercapacitor. The extent to
which operating power could be reduced is for electronics in the NTU to power
down to a single part which supports a very low bit rate protocol over the
fibre for voice only and the exchange equipment adapts to that protocol when
it is sensed. Power consumption of a standard POTS phone may be the limit on
how small the backup battery/supercap could be unless landline handsets are
also upgraded.

All the best
Harry



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