27 Dec. 2012
SETI League
PriUPS Project

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Today we eschew further reportage about larval cereal infestation and take up a couple of PriUPS issues.  This isn't any particular anniversary of the PriUPS project itself, but I made an interesting and surprising discovery about my long-neglected UPS (Uninterruptible Power Supply), which is, after all the UPS part of the PriUPS name.  The UPS I use to power the house is a large, computer room unit.  Unlike the typical home UPS which can run your computer for a few minutes to give the computer time to shut down gracefully, this UPS can power a house for the better part of an hour even without recharging by the Prius.  How does it do this?  Batteries.  Lots and lots of batteries.  Here's a page from the PriUPS portion of this site with some pictures.  The first picture under "Let's Do Some Tests" shows the battery compartment of the UPS.  It has four trays, each of which holds 10 lead-acid batteries, each of which is rated at 12VDC at 7.5Amp hours.  Adding them all up, they can supply 240VDC at 15A for one hour, or given the typical inefficiencies of conversion and fast discharge, about 3kWh of energy at 240VAC. 

But only if they are good.  Unfortunately, as we all know, lead-acid batteries, such as are used in most automobiles, have limited lifetimes.  One will typically change a car battery, depending on weather and driving conditions, after anywhere from 3 to 6 years of use.  I bought this UPS on eBay.  It was four years old when I got it in 2005, and I was pleased and surprised that the batteries were in good condition.  Having to replace 40 batteries would have more than doubled the final cost of the unit, so I was hopeful that I wouldn't have to do so for at least another year.

A year passed.  And another year, and yet another.  And the batteries did, indeed, get worse and worse.  But they deteriorated so slowly that it was only recently that I felt the problem had to be addressed.  In other words, these batteries with a nominal 5-year lifetime were still pretty good after twice that long.  I did not contemplate changing them with equanimity.  They may be expensive, but at least they're heavy and hard to get at.  Get at them I did, though, and after removing the first battery tray, I made an interesting discovery.  All but two of the 10 batteries seemed good!  I replaced those two, tested the remainder for voltage and current, and replaced the tray in the UPS.  The next tray yielded 3 bad batteries, and the same result after replacing them.  In other words, most of the lead-acid batteries appeared to exceed their expected lifetime by more than a factor of two!  Same amount of heavy lifting, but a lot less heavy paying. 

A major failure mechanism for lead-acid batteries is the process of sulfation, where the lead sulfate forms large crystals and cannot be used by the battery.  Lead sulfate crystals, PbSO4, somehow failed to ruin the large majority of my UPS batteries, a Pleasant Battery Surprise indeed.

A Commercial Inverter, Semi-Hoorah!

When I started the PriUPS project, I practically pleaded with existing manufacturers of inverters to offer one that would work with the Prius.  Although I and others with some electronic knowledge were able to find appropriate units on eBay, most Prius owners would be a lot happier if they could just buy a product that was guaranteed to work for a reasonable price.  I did have talks with a couple of prospective manufacturers.  Nothing came of the talks, almost certainly because they felt that the potential market was too small.  Now with the large number of hybrid vehicles on the road, at least one manufacturer seems to be making an effort to sell an off-the-shelf inverter.

I received an email from Jack Chen, who is offering a unit on eBay at present: 


I don't imagine this link will be good for more than a few days, so I'll try to remember to replace it with something more enduring.  I must mention (and emphasize with italics) that I have neither seen nor used nor tested this product.  But reading the specs, it looks like a partial solution to the lack of a commercial inverter. 

  • It will connect directly to the traction battery.

  • It provides 2000W continuous and 3000W surge power.

  • It appears to be light and compact, and can easily be installed in the car.

  • There are sample installation photos in the eBay listing.

  • Although it's not mentioned in the listing, I see no reason why you couldn't install two in parallel to double the power.

  • The price is $595.

Its main flaw is that, despite some ambiguity in the listing that implies otherwise, it only supplies 115V, so it can't be used with 230V appliances such as a well pump motor.  Due to the ambiguity, I contacted Mr. Chen and he replied with this helpful note: 

"Yes, this inverter is for 120VAC output only. It doesn't supply 240VAC. But if this kind of product has market, we will supply 4KWH dual phase 240VAC/120VAC inverter in the future."

I hope he receives enough custom and/or encouragement to make one.  If you purchase the one currently on offer, please let me know how the installation and testing goes.

Follow-up 21 Dec. 2013

I received an email from Doug who noted the following:

[I was] told about the Toshiba 1600EP, which after some searching I’ve also found under the Alpha brand name and at least one other, but most hits are on the Toshiba name so they are likely the original manufacturer.  The more modern replacement of that line with the same specs is the 1600XP.  Toshiba groups models with varying specs under the one model number so you must be careful to look at the kVA capacity to get the right ones.  The 3.6 and 6 kVA versions have a nominal DC voltage of 216 volts, with an alarm at 192 and shutdown at 170.  I estimate an upper voltage of at least 270, so they would be perfect for some of the Prii.  The 8 kVA and above are spec’ed at 288 nominal, 246 alarm, 227 shutdown, with an estimated upper limit of at least 360, so these should work with the Highlander, possibly the Volt, and possibly some of the other Prii.  Unfortunately as well-suited as these are there are two downsides.  From everything I’ve read they can’t be cold/black started from the DC input, so without a temporary AC “jump start” they would be useless (the APCs can do a cold/black start).  And while they can natively output 120/208/240, that is because they have a transformer built-in which makes them very heavy even without batteries, like the old Liebert Smart-UPS line.  With batteries they are around 475 pounds.  They would be fine permanently installed in a garage, just don’t plan on taking one on the road for portable power.

 I also found one version of their model 1000 line that might work with the Prius, the 6 kVA version, with a 240 nominal DC voltage.  AC output is 208/240 with a weight of around 150 pounds with batteries – no transformer or 120 volt output (same as the APCs).  So an external transformer will be necessary for portable power or sub-panel connection.  I do not know if this can be cold/black started or any other specs.

His email prompted me to check on the eBay UPS I mentioned above.  It is still on eBay after a year with a good quantity left.  The price has been substantially reduced, presently on offer at $395

Hostess Twinkie Update

2012 info:  It seems that the strike was NOT settled and Hostess IS closing.  Read about it here.

2013 update:  And being noted here since I did the late 2013 follow-up above, some news more stale than a Twinkie could ever be:  Hostess has gone through bankruptcy proceedings and Twinkies and other products are now available under new management.

"Supreme Court Justice" Should Be a Good Clue

I asked Siri "Where did Supreme Court Justice Elena Kagan go to school?" and Siri favored me with this reply: To be sure, if I had just asked "Where did Elena Kagan" go to school, that would be a perfectly reasonable "misunderstanding."

I've been very impressed by how well voice recognition is working on Apple, Android, and Windows products.  I'm less impressed by the logic used to respond to simple queries such as this.  Please let me know when Watson is available for my cell phone.

"Natchez Trace"
Pavlov's Dog




For once I actually attended the advertised event and won the shirt by answering a question about computer programming.  (Which reminds me that I owe this blog a diatribe about modern software.)

VEE is a program that allows graphical programming of test equipment.  Fun!

Agilent VEE Days T-shirt
© 2012
Richard Factor

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