Sunday, March 28, 2010

New UPS Battery

When I moved into the Smart Apartment I was one of the first residents. The power would go off occasionally as building work was done. So I installed a small Uninterruptable Power Supply (UPS). This is a SOLA UPS 305 520. It looks like an oversize power board, with three sockets for equipment protected by the UPS and two ordinary power sockets. It has a small gel lead acid battery (Panasonic UP-RW12200CH1) which can supply power to a typical desk top computer for a few minutes while it shuts down in an orderly fashion (there is a data port on the UPS to tell the computer it is on battery power and should shut down). In practice the UPS would run for about half an hour with my modest computer set-up, longer than most power outages.

Recently the power went off and the UPS failed to operate for more than a few seconds. The battery needed replacing (they last only a few years). There is a separate battery compartment with a cover held n by one screw, so they are reasonably easy to replace. Care should be taken with a UPS, as it can generate dangerous high voltages, even when disconnected.

Gel lead acid batteries are sold by electronics shops, so I thought it would be reasonably easy to get a replacement. Unfortunately the commonly avialable batters are the same dimensions as the Panasonic, but 10 mm longer. As a result the replacement would not fit in the case.

Rather than buy the batter 10mm larger, I decided to buy an even bigger one. The Panasonic unit has no capacity marking on it but appears to be about 4 AH (Ampere Hours). I noted that there was a sweat spot at 7.5 AH: the smaller batteries did not seem to be much cheaper and the larger batteries got significantly more expensive from this point on. The 12 volt 7.5 AH batteries are the size used by many UPS, home burglar alarms and the like.

So I bought a battery from Adelong in Sydney for AU$22.85. This has the same connectors as the smaller battery. I then just need to cut a hole in the side of the battery compartment to fir the larger battery. It will not be elegant, but should work longer than the original.

By the way, you should, in general, not replace a rechargeable battery for one of a different voltage, size or chemistry. Also you need to take care you connect the battery terminals the right way around. The gel batteries have no polarised connectors: you can connect it the wrong way around. If you use the wrong battery, or connect it the wrong way, the result could be an explosion and fire. However, for those with the skills and confidence, replacing the battery in the UPS can save a lot of money.

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Friday, November 13, 2009

Philips Bodygroom Shaver Disappointing

PhilipsNorelco BG2020 Bodygroom ShaverPhilips Bodygroom Shaver claims to to be able to trim and shave all body zones. The TT2021 model I purchased recently doesn't do either very well. The unit cost AU$66.44 at BigW, but I have since seen units offered at the Shaver Shop for AU$49.95 (some with a cash back offer from Philips as well).

As I discussed in December it would be useful to be able to do hair cutting and shaving with one gadget. When travelling, having to carry a razor to shave and electric clippers to trim my hair is an annoyance. Philips Norelco BG2030 Professional BodyGrooming SystemThere are some grooming kits such as the Phillips (Norelco in the USA) BG2030 Professional BodyGrooming System, which have a common motor body with separate clipper and shaver heads. Instead the TT2021 uses the one head for both.

The TT2021 looks like small oscillating electric razor with a trimmer on each side of the foil. It is not a rotary razor, like the usual Philips ones.

This design is a compromise. The foil area is relatively small and so it takes a long time to use it for shaving. The foil is relatively coarse and does not give a close shave (more of a five o'clock shadow look). The cut hair falls from the foil, making a mess and is not retained in the unit as with shavers.

The two trimmers are close to the foil surface and are activated all the time. This is useful as you can use the trimmers to cut longer hairs with one sweep and the adjust the angle of the unit slightly and cut the short hairs with the foil with the next sweep. However, on any concave curve of the body, either or both of the trimmers come in contact with the skin when you don't want them to, causing uncomfortable scraping.

The two trimmers work well on short relatively stiff hair. They do not work well on longer hair, such as on the head. The teeth of the trimmers are finer than those of hair clippers. If the combs are used these become clogged and have to be cleaned frequently.

I found the
TT2021 only useful for cutting longer hairs on my neck before using my regular shaver. I did not find it usable for cutting hair anywhere else on the body. The unit is not suitable for trimming and shaving all body zones, as claimed by Philips. With this unit you will still need a set of clippers for the head and a razor for the face and other parts of the body. Instead of having one all in one unit, you will end up with an extra unit.

The unit has good points, being well shaped to fit comfortably in the hand and water proof so it can be used in the shower. The charger stand works well. The battery life is very long, but I unfortunately found that out this morning when the switch stuck on and I could not turn the unit off. I will be returning the product to BigW for a refund.

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Sunday, June 07, 2009

Aldi Ready to Use Rechargeable Batteries

Aldi Ready to Use Rechargeable BatteriesAldi is advertising AA and AAA Ready to Use Rechargeable Batteries. These are in packs of two for AU$7.99. The AA size are 2000 mAh and the AAA 800 mAh. These appear to be low discharge cells, simialr to SANYO eneloop , Sony Cycle Energy and Duracell Pre Charged. The advantage of these batteries is that they hold a useful charge for about a year and are compatible with chargers and devices which use ordinary nickel metal hydride (NiMH) rechargeable batteries.

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Wednesday, May 20, 2009

Cordless drill used for brain surgery

As reported by the ABC and other media, Dr Rob Carson used a DeWalt cordless drill to a hole in the skull of a 12-year-old boy top relieve bleeding to the brain in Maryborough, Victoria.While obviously an emergency measure, cordless tools would seem to be a good choice for this as they would reduce the risk of electrocution. From the photos shown in the media, the unit used appears to be a DEWALT DC759KA 18-Volt Ni-Cad 1/2-Inch Cordless Drill.

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Saturday, September 20, 2008

Pre-charged Nimh C Cell Batteries

The low self discharge AA batteries I installed in a String Trimmer seem to have lost their charge after just under a year. This may be because they were left plugged into a dumb charger (the batteries are supposed to be disconnected from the cgarged when the are charged and then hold their charge). Or perhaps a year is all that can be expected in a heavy duty application from these batteries. Sub C cells, which the trimmer originally had, should offer more power.

Tenergy are offering
Pre-charged Nimh C Cells on The catch is that they are only 3000mAh capacity. It is likely these are actually AA cells fitted into a larger empty metal cylinder to make them up to C cell size. Other C cells are usually 5,000 to 10,000 mHa.

See also:
  1. Pre Charged NiMH batteries
  2. String Trimmers
  3. glue guns
  4. Battery chargers
  5. replacement battery packs

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Friday, June 27, 2008

Sony Cycle Energy Rechargeable Batteries

Sony Cycle EnergyNi-MH Rechargeable BatteriesSony are now offering "Cycle Energy" pre-charged, low discharge NiMH Rechargeable Batteries. According to the Wikipedia, these are made by Sanyo. Presumably they are identical to the Sanyo eneloop, but cost a few dollars more.


Monday, January 21, 2008

Low Self Discharge NiMH C Cells

Low Self Discharge NiMH C Cells ( "ready to use" or "pre charged" 4500 mAh) are now being offered on Amazon at US$26 for four. These are branded "Accupower Evolution" and are claimed to have a self discharge rate of 2% per month. This is much lower than the rate for regular NiMH cells of 0.5-1% per day and high capacity cells having the highest self-discharge rates.

I have used smaller AAA and AA low self discharge batteries successfully, but have not yet tried the larger ones. Some tests of the smaller cells by users seem to be inline with the maker's claims.

Accupower are also offering Low self discharge D cells (10,000 mAh) but these do not yet seem to be widely available.

The lower discharge rate batteries might allow the use of smaller batteries in some applications, such as solar home lighting for remote areas using small solar panels. The batteries could be used with efficient LED lights, such as Flexible LED Tape Light emitting diodes (LEDs), to provide light where it is needed. The cost of the batteries and LEDs would be much higher than some alternatives, such as lead acid batteries and fluorescent lights, but because the LEDs can deliver the light where it is needed, the overall cost might be lower.

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Friday, January 11, 2008

Solar garden lights an environmental hazard?

Solar garden lightsAccording to a pamphlet I picked up at the hardware store, the rechargable Nickel-cadmium (Ni-Cd) batteries in many solar powered garden lights only last 2 years. Apart from not represeting good value for money, Cadmium is a toxic heavy metal. Ideally a wired light should be used, but failing that, using nickel metal hydride (NiMH) "Pre Charged" would be better.

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Monday, November 26, 2007

Replacing the Batteries in a String Trimmer

Cordless Line TrimmerA few weeks ago I replaced the cells in a mobile phone battery with new "pre charged" ones. This worked so well I have just done the same thing with a String Trimmer. This was not easy, but will be worthwhile, as the new battery should have twice the lifetime.

The "pre charged" (or "Low Self Discharge") rechargeable nickel metal hydride (NiMH) cells are available in AAA and AA sizes. They cost more than regular rechargeable batteries, but are claimed to be able to be charged 1,000 times, twice the usual. Also they have a lower self discharge rate. As a result they can be left for months before use.

Cordless Tool Battery PackThe string trimmer (also called a line trimmer), was a few years old and the battery pack was going flat after a few minutes use. The particular unit uses a Ryobi 12 Volt battery, similar to the battery in many cordless tools.

Repacking battery packs for cordless tools is a lot easier than for cell phones, as they are much larger and use standard size cells. The packs for cordless Drills and Garden Tools commonly contain sub-C cells (as fat as a disposable C size battery, but shorter). Higher voltage tools use more cells in their battery pack (1.2 Volts per cell, so 10 for 12 volts).

AA NiMH Pre-Charged Rechargeable BatteriesThe sub-C cells are commonly available with solder tags attached for making up into battery packs. However, I decided to replace them with the smaller
precharged AA cells. These cost about the same as the sub-C cells. They have about 17% less capacity than cheap sub-C cells, but they should outlast the C cells and retain their charge longer. Also, because they are smaller than the original cells, it is easier to pack them into the original battery box of the tool.

Rechargeable batteries should only be replaced with equivalent types (same chemistry). NiMH ones should be replaced with NiMH. Nickel-cadmium (NiCd) batteries can be replaced with NiMH, but you may need a different charger. The smaller "pre charged" AA cells should work fine in all but very high power drain devices in place of sub-C cells.

Lithium batteries used in laptops and some new power tools require very specialized charging and can explode or catch fire if not charged correctly . Only a
Lithium battery specifically designed for the tool should be used. Do not try substituting Lithium batteries for other types.

In this case the line trimmer came with a 12 volt NiCd battery pack. The trickle charger was rated at 300 mA at 12 volts, so I was reasonably sure that it could recharge the
NiMH batteries, without damage.

The first step should be to ensure the battery is discharged. I forgot to do this and was surprised by sparks when I accidentally shorted the terminals with a screwdriver. The next step is to remove the screws holding the pack together (in this case five). Inside were ten sub-C cells glued together, with connecting cables and straps welded on.

One cell was holding the battery connectors in place and I decided to retain this one (while electrically insulating it from the new cells with tape). Prizing out the old cells took some effort as they were glued in place, as well as being attached to each other. With one cell out it was easier to get the others out. I cut the straps connecting the cells together, being careful not to short the battery terminals.

At this point I discovered a small can with two wires attached, taped to one battery. This is a temperature sensor, used by a rapid charger to prevent overheating of the battery. The simple charger I have does not use this sensor, but I decided to retain it anyway and left it attached to the connector.

Battery HolderThe new set of cells fitted with room to spare. I could have used a battery holder to both hold the cells and electrically connect them, but decided not to (which I regretted later).

To hold the cells together I used high temperature glue from a glue gun. This may not be the best approach, but the cells should not get hot enough to melt the glue. I simply put four cells side by side, glued them, did the same to another four and glued that set on to of the first. The last two batteries went on top. I made the pack with some spacing between the cells, both to provide some room for air circulation to cool the cells and so the cells filled the container and did not rattle around.

Digital MultimeterThen I soldered the batteries in series, using a soldering iron and some insulated wire. At this point I regretted not using a battery box, which would have avoided the need for the soldering, which is difficult on the flat terminals of the batteries. With a battery box I would have just had to install each cell and connect two leads from the box.

I then soldered the two leads from the new battery to the old connector of the battery pack. I had some difficulty fitting everything back in the case, but succeeded after a few attempts. I then tested the battery with a multimeter, to make sure the voltage was correct and I had the batteries wired the right way around. Apart from the tool not working correctly, connecting the batteries the wrong way (negative terminal to positive), may damage the tool, the charger ,or cause the battery to explode.

Replacing the battery in the line trimmer showed it was working. I then tried it out on the lawn and then recharged the battery.

Of course, in the end it might have been easier to buy a replacement battery pack. ;-)

See also:
  1. Pre Charged NiMH batteries
  2. String Trimmers
  3. glue guns
  4. Battery chargers
  5. replacement battery packs

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Friday, November 02, 2007

Replace your battery to save the planet

Pre Charged NiMH batteriesOne of the hidden environmental costs of modern gadgets, such as mobile phones, PDAs, MP3 players and digital cameras are the batteries used. Rechargeable batteries are better than disposable ones, for devices which are used often. But for devices used occasionally, rechargeable batteries can have a short life. Perfectly usable devices are replaced when they just need a new rechargeable battery.

Common nickel metal hydride (NiMH) rechargeable batteries will only last a few years, or about 500 charges. Also the batteries will self discharge even when not used, so for low power devices or ones you only use occasionally you will find the batteries flat when you go to use the gadget.

I bought some "Pre Charged" NiMH batteries (technically known as "Low Self Discharge Batteries") to replace the pack in a mobile phone. These cost a bit more than premium NiMH batteries (and about three times as much as the cheapest). They are claimed to hold a usable charge for a year and to be rechargeable twice a s many times. So far they are greatly extending the life of the phone. Currently these batteries are only available in AAA and AA sizes.

It should be noted that rechargeable batteries should only be replaced with equivalent types (same chemistry and size). The NiMH ones are reasonably compatible with different brands of chargers. However, Lithium batteries used in laptops require very specialist charging. You should buy a battery which is specially made for your device.

Many rechargeable devices which have custom battery packs can be replaced with third party packs, even after no longer available from the original maker. Also your old batter can be "repacked": the plastic case is prosed apart and new cells inserted. I repacked an old Ericsson phone battery myself, but this is something which should be left to specialists.

First I made sure that I had a spare battery pack in case I broke the pack. Then I checked the voltage and polarity of the pack to make sure I would make the new one the right way. The I prised the plastic case to find it had four extended NiMH AAA cells. I bought four AAA precharged cells. These were slightly shorter than the existing cells. I the had to solder the cells to make the battery and attach the terminals on the case and check the voltage and polarity with a meter.

At this point I made the major mistake of using my hot glue gun to stick the cells in the case. I then found the cover would not fit due to excess glue. I then reheated the glue and tried again. At this point I got a little desperate and so first stood on the pack to close it and then applied a hammer a few times (do not try this at home). Eventually the case closed and the battery worked. At least I found the batteries are reasonably robust. ;-)

Repacking battery packs for cordless tools is a lot easier, as they are much larger. These packs commonly use sub-C cells (as fat as a C size battery, but shorter). The sub-C cells are commonly available with solder tags attached for making up into battery packs. However, it may be worth replacing the sub-C cells, with the smaller
precharged AA cells. In theory this will result in a loss of 40% capacity, as sub-C cells are available with 3300 mAh, whereas the AA cells 2000 mAh. However, the cheaper sub-C cells can be as low as 2400 mAh and are of questionable quality. For about the same cost, high quality AA cells will start out with 17% less capacity, but retain their charge better and outlast the cheaper batteries.

See: Pre Charged NiMH batteries

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