UPS battery replacement

Ok, no big rush as I need to save up for a round tuit before I get to work on it.

tm

Time to find the tuit then. Just dragged out the maintenance manual. From the input transformer secondary/bridge and via a diode the battery charge line goes to an LM317T. They use the LM317 as a current-limited voltage source. That's two parameters they could potentially screw up. IMHO they did both.

While they recommend setting the voltage at 14v4 (i.e. 2v40 per cell) many of these instruments are exposed to long period of AC supply and this is above the Hawker/Gates recommended float setting of 2v27-2v35 per cell.

I wanted more than the customary 2-year pack life, so I adjusted R4 to set the float voltage to around 13v8 (i.e 2v3/cell). See below (*) regarding setting this.

Now to deal with recharge current limiting. To quote from the Hawker Cyclon Selection Guide: "There is no need to limit the inrush current to the battery during the initial phase of constant voltage charging. The internal resistance of Hawker Cyclon single cells and Monoblocs allows for large inrush current without damage." The LM317T will internally limit current to around 1.5A, which is puny when you realise these cells have a 5-minute constant-power discharge capability of 45A. Give that useless 0R22 2W current limit resistor the flick. Its only contribution is to unnecessarily slow recharge.

(*) After the voltage divider branch on the 317 output, there is a dirty big diode in series with the battery line, to prevent unwanted backfeed/discharge This has the effect of puuting a slope on the charge I/V curve anyway, so the voltage setting needs to be executed at zero drop across this i.e. measured at the battery terminal point with the battery either fully charged or preferably disconnected (charger O/C).

If you don't have the rather rare maintenance manual, I can send a part schematic to a valid email addie if you wish.

Caveat: this information is provided for educational purposes only and the consequences of applying it in all cases lie with the user.

Scanned IFR manuals and schematics can be found at:

The IFR-1500 charger circuit is worse: Same 14.2V float. I'm using 13.8V for gel cell float voltage.

Thanks much for the details.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

We don't have too many outages in this area. Mostly, they're short term glitches and gaps lasting at most a few seconds. The UPS hardly gets a workout with such short duration runtimes. Mostly, the batteries sit there, do nothing, get warm, and die without ever getting used. Short recharge time is totally wasted on such systems.

The others are big UPS's that are intended to only run for a few minutes while the automatic generator starts, warms up, and kicks in. For those, I may want 10kw, but only for maybe 2 minutes maximum. That's quite a different style of operation, that again doesn't need short recharge times. We occasionally do have long term outages, but that's what generators are for.

The "answer" is that LiIon batteries will self-deteriorate if left on

100% full charge and in a hot box. See above URL. Charging to 4.10V/cell the battery holds about 10 percent less capacity than going all the way to 4.20V. In terms of optimal longevity, a voltage limit of 3.92V/cell works best but the capacity would only be about half compared to a 4.20V/cell charge (3.92V/cell is said to eliminate all voltage-related stresses). In other words, if the LiIon battery were charged to full capacity, it would be dead in a few months, even if it had never experienced any charge/discharge cycles.

However, I haven't been paying attention to new developments. Drop in Lithium Iron Phosphate UPS replacement batteries are available: The claim is that they will last longer and survive more charge/discharge cycles. At the $135/ea price, we're not going to see these in commodity UPS's in the near future, but maybe for critical applications. Personally, I don't see the benefit. If longer life were a problem, just lowering the float voltage on gel cells would accomplish the same thing at much lower cost.

I've been playing with cell phone batteries most of which use a conservative charge cycle. During charging, I haven't seen any heating on new cells. Old cells will get warm. For fun, I charge cycled an obviously bulging battery which finally became warm enough for me to worry about it catching fire. I don't know much about the chemistry involved.

Agreed. New batteries by themselves do not get how when charging. Old batteries are another story.

Agreed. Laptops are a horrible environment for LiIon. However, that also applies to UPS's. The heat from the UPS or the server closet will cause the LiIon batteries to deteriorate more quickly. Keeping the battery at 100% charge (4.1V) will also speed up its destruction. Of course, in order to produce impressive UPS runtime numbers, the manufacturers will set the charge point to as close to self destruction as possible.

That would double the battery costs. Since that seems to be the most expensive part of the puzzle, it's unlikely. Still, it may be a requirement to prevent short battery lifetimes.

Submerge the LiIon battery pack in a water jacket or may anti-freeze? That might just work for larger cells, or maybe a drop in gel cell replacement.

Or, maybe a mess of 18650 LiIon batteries shoved into a finned aluminum tube. Each cell protects itself from over/under voltage with internal circuitry making replacement easy. Hmmmm...

History had demonstrated that this isn't going to happen. Nobody is going to advertise a UPS with a battery that lasts longer. Instead, they're going to advertise that it runs longer.

I doubt the

Yep. If you want to see what it takes, read about what Tesla Motors and A123 did with their battery packs. It has a cooling systems built in which has become a problem. They claim that the new Nanophosphate EXT battery will eliminate the cooling requirement, but I'm not so sure: (Note the reference to telecom backup in the text). If it does work as advertised, it would make a nifty UPS battery that wouldn't get hot during charge.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

Bacvk in the mid-90's I had the end-to-end task from specifying though purchasing/commissioning of a 900 kVA UPS system for a large 'pooting centre (when such centres used "big iron"). This was configured as

3x300 - load was just under 600 - hence 3 units with one redundant. Three diesel-alternator sets produced around 1500 kVA total (1x900 and 2x300). Paralleling was given about 10 seconds after the first set came onto the generator bus. PLC was set to allow bus connect to load with one large or any two, once that time had expired. The diesel reliability was such that we never had an occasion where the UPS battery banks saw a full minute of discharge, although they were sized for about 25 minutes at full 300kVA load. The float voltage was set rather conservatively on that too.

I did note one line in the referenced page which states:

"The author of this essay does not depend on the manufacturer?s specifications alone but also listens to user comments. BatteryUniversity.com is an excellent sounding board to connect with the public and learn about reality."

and that left me uncertain to what extent these numbers are anecdotal rather than the result of testing - and if so, whose testing.

I have a problem with their figures. For me the 90% for 4v10 doesn't sit well with 50% for 3v92. The difference is too wide.

As I mentioned, I'd expect - and this is consistent with our own cycling tests on 18650's - more like low 80% range for 4v10.

I have a problem with that too. Very often I see posts in forums that say Li-Ion last a maximum of three years. What garbage. I have here a BTP-T31 pack (Sony Corp, made in JP, from an AcerNote Lite 370 lappie) date-coded 9637. New it gave a tad over 3 hours. I give it a cycle about every year - when I remember - and it now gives about two hours. I then recharge it (to I presume 4v20 - I haven't measured - and put it back into storage. Again, a sample of one ....

(snip)

aka 4v20 for that geberation of cells ...

Indeed. Even with present-day soho units, the cost of replacing the SLA's is usually not materially different from replacing the UPS.

I recall in one forum a poster was bitching about the cost of new SLA's for his pre-owned UPS. I explained that IMHO there are two rules for soho UPS use - (1) expect to replace the batteries at max 2-year intervals if you want the thing to provide a reliable backup, and (2) if you can't afford to do that, you can't afford to own a UPS.

The cost factor drives a lot of battery decisions. On one small AC-supplied communications site which was critical for an annual event lasting a few days, we used a maintenance-free automotive battery. New one installed each year just before the event. That was cheaper than funding a proper industrial system.

nothing that serious, just kept away from heat sources.

You'd need that individual protection, as you'd need a pretty large stack of 18650's to do much.

The grim truth.

I'm good with a full original, but that will certainly help others.

?? my IFR1200S/A manual shows 14v4 ...

Also, not sure if it is worse. ALthough I am a 317 fan, at least the divided output is compared to a 5v1 zener, potentially (ouch!) a better reference than the 317's internal. Only downside is that 5v1 is the zener value nearest zero tempco, while most SLA manufacturers actually cite a required charge tempco.