What battery is best for living off the grid?

[PP]

Hey HB, Aren't those the bats that the phone company used back in the 60's and 70's for their remote switching stations? Probably even before then, I just remember a large heavy 'Alkaline' battery that required a lot of them in series to generate 120V DC for their equipment. I could be mistaken, mind isn't what it used to be LOL Will

[Sean]

Hey HB, Aren't those the bats that the phone company used back in the 60's and 70's for their remote switching stations? Probably even before then, I just remember a large heavy 'Alkaline' battery that required a lot of them in series to generate 120V DC for their equipment.

Phones are 48vdc.  All phone company facilities run on this voltage, even the 20+ story towers in major cities, not just remote sites.  And they all run on the batteries all the time, it's not a standby-type system like a UPS.

Most facilities use conventional lead acid batteries.  When the offices were built, properly segregated and vented rooms were incorporated for the batteries.  Nowadays, AGMs are used almost exclusively, because they have a lower lifetime cost of operation than any other type (flooded or gelled), and as the flooded batteries are retired, they get replaced with AGMs when practical (you pretty much need to change out the whole battery room in a matter of a few days, without ever disconnecting the power).

Remember, phone installations are a "float/standby" applications -- the batteries spend almost their entire lives on float, and they discharge deeply only on the rare occasions when commercial power is lost.  That's a different battery construction than the sort of deep cycle usage needed on a coach.  NiFe or NiCd are actually poor choices for this type of service; they need to be discharged completely on occasion to maintain their capacity, and do not tolerate constant float well.

The exception in the telecommunications world are remote off-grid installations, which are usually solar-powered.  These installations often use AGM batteries, but you will also find gel, NiCd, NiMH, and Li-ion in the field as well.  You won't find NiFe, as that technology was phased out of existence in most of the world years ago; I believe only China still manufactures NiFe batteries.

This whole thread has inspired me to write on the topic; look for my article on battery technologies in the January issue of BCM.

-Sean
http://OurOdyssey.BlogSpot.com

[luvrbus]

I read about how great the AGM batteries are on this board and no one ever seems to have a problem with AGM battries but me.
I am still working on my battery compartment where one vented taking out the other 5.
I have found out they do have problems sometime with the AZ heat and charging, I saw another RV that had one vent SAT at the RV dealer.
I like the idea of no corrosion and adding water but they just don't work for me and all the 300amp Lifeline I have had seem to hesitate till they have a full load and I am not the only one that notices that talking to the guys at Copper State and AZ Wind and Sun that is a common topic among  RV owners with 2 or 4 of the AGM .
Mine either vented and blew up or blew up and then vented but it was a mess and still is.



good luck

[uncle ned]

Sean

must have been a few years since you were in a central office.
now all are computer run with standby battery for the processor.

A 1,000 port non-blocking switch runs off a 200watt power supply.

uncle ned

[Sean]

I read about how great the AGM batteries are on this board and no one ever seems to have a problem with AGM battries but me.
I am still working on my battery compartment where one vented taking out the other 5.
I have found out they do have problems sometime with the AZ heat and charging, I saw another RV that had one vent SAT at the RV dealer.  ...

Clifford (and all):

I did not include this in the article, and in hindsight perhaps I should have, but it is unequivocal that one potential drawback to VRLA batteries (that includes both AGM and gel) is the possibility of a condition known as "thermal runaway."  When a VRLA battery undergoes thermal runaway, it basically explodes, and I would guess this is what happened in your case.

The most common root cause of thermal runaway is excessive charge voltage/current under high heat conditions.  This is one reason why it is recommended that you have a temperature-compensated charger, with a temperature sensor properly positioned on the batteries.  Also, battery compartments for VRLA batteries should be temperature-controlled; whereas flooded batteries should always be outside the personnel space for gassing safety, VRLA batteries are often better off inside the personnel space to take advantage of the climate control.

Constant float is another factor that can "prime" a VRLA battery for a thermal runaway.  Studies have been done on this:
http://www.springerlink.com/content/v337108736332440/
http://telephonyonline.com/wireless/mag/wireless_thermal_runaway/

This should be a consideration for anyone who spends a lot of time connected to a power outlet, where the batteries are on constant float (as opposed to away from power, where the batteries are regularly cycled).

I advise anyone, whether they have VRLAs or not, to disconnect the main battery charger when storing their coach, and, instead let the batteries cycle down, then top them up every couple of weeks to a month.  Constant float is generally not good for batteries; in applications such as telecom where it is unavoidable, the batteries are watched religiously, and have different construction to tolerate this service (I do not recommend telecom batteries for bus conversions for this reason).

must have been a few years since you were in a central office.

A few, but not many, and I am still well connected.

now all are computer run with standby battery for the processor.

At the risk of derailing this thread, the most common class-5 offices (for the lay folks, those are the telephone switches at the end of your home phone line) are the Lucent #5ESS (a product on which I worked when I was at the labs), the Northern DMS-100, and the GTE GTD-5 EAX.  All three of those switches, while "computer" controlled (we called them "processors"), are 48 VDC battery powered.  Remote modules for those systems, which comprise now the majority of rural end offices, are also 48 vdc powered, including the computer controls.

The 5ESS, BTW, is controlled by a computer that AT&T briefly tried to sell as a stand-alone general purpose computer, the 3B20D (redundant duplex model; 3B20S was the simplex version).  We had to create 208-vac power supplies for them for this purpose -- the 3B20 is a 48-vdc system.  Now that's 25+ years ago, but most of those switches are still in service, and the 5E's made today are still based on a 3B processor.

A 1,000 port non-blocking switch runs off a 200watt power supply.

Sure.  And in a "real" certificated carrier's facility, it will be a 48VDC supply.

Even modern "Internet" switching hardware, such as ATM switches and gigabit ethernet devices are available with 48-vdc supplies for installation in carrier facilities.  When I was still working, deploying major network infrastructure nationwide for DSL networks, we ordered all our Cisco equipment with 48-vdc supplies.

You can, and some do, buy modern digital POTS switches with 120-vac supplies.  But  generally speaking, you don't find them in major carrier class-5 offices of, say, 20,000 lines or more.

-Sean
http://OurOdyssey.BlogSpot.com

[luvrbus]

Thank you Sean you are the 4th person to explain that to me the LifeLine rep told me that they should never be mounted in or near the engine compartment unless they are design for starting.
FWIW I did have temperature probes on mine when it happen. 



good luck

[Len Silva]

Central offices, back in the day, also usually had a group of smaller batteries in a 130 volt string for carrier repeater supply.  That may be what Will remembers seeing. That was my bailiwick for many years.

[Sean]

Central offices, back in the day, also usually had a group of smaller batteries in a 130 volt string for carrier repeater supply.  That may be what Will remembers seeing. That was my bailiwick for many years.

Again, I did not want to derail the thread with a bunch of (potentially uninteresting to most here) minutiae about telephone offices, but yes, there is also a 130vdc supply, as that also happens to be, among other things, the required voltage for the "coin collect" signal for payphones.

Working in the telecom industry develops one's battery knowledge and skills -- I still have tools with scorch marks on them 

-Sean
http://OurOdyssey.BlogSpot.com