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APC Back-UPS Connect BGE70 Product Review

Rating: Two and a half star rating.

Sometimes you wonder why anyone would buy a certain product.

Sometimes you wonder how it is a product works as well as it does despite severe corner cutting in its design.

Sometimes you wonder why a company designs something in the way that they did.

Here's a product that begs all three questions, and maybe a few more besides.

Product Image: APC Back-UPS Connect BGE 70

APC's BGE70 Back-UPS Connect is an ultra tiny uninterruptible power supply made for use with low power loads, such as wireless routers and VoIP gateway devices. It may also come in handy for use with other types of networking equipment. Two other models besides the BGE70 exist in this particular product category, a BGE50 and a BGE90. The primary difference is in their capacity just as the model numbers would suggest. The BGE50 uses a lithium ion battery, while its siblings use conventional lead acid batteries. For the two largest models, APC claims that when running on battery, that the output waveform is a square wave. Going by the specifications, BGE50 is again the outlier, with a claimed modified sine wave output and, rather surprisingly, three pin grounded outlets!

Manufacturer suggested retail price on these units starts at a downright astonishing $140 for the BGE50 and $50 for the midrange BGE70. They ought to turn up cheaper in other places with some looking, and I definitely suggest that you do some looking around for the best price, if you really want one of these. Retail price for my example was around $30, and much less after stacking up some coupons and other discount offers.

All of these products are marketed as a way to keep your Internet connectivity equipment, and a few other "essential" low power draw devices online throughout power outages. Even the most miserly of computer systems are likely to far exceed any of these units' capability, and that's assuming you could even plug them in. APC includes only two pin outlets on models other than the BGE50ML, and I can only guess that their intention was to stop people from majorly overloading these units by expecting a computer of any kind to operate from one when the lights go out. Unfortunately, this decision also limits their utility. Some networking devices that would fit comfortably within the power available from these units have three pin grounded electrical plugs. And that's that--without resorting to floating the safety ground by misuse of an "adapter" or by simply cutting it off, you can't plug any such device into these units.

Floating the safety ground of any electrical device, outside of some very isolated and controlled scenarios, is a bad idea. No, really. It is. It doesn't matter that people do so "all the time". People do lots of things that really aren't good ideas and a surprising number get away with it for a very long time.

It can happen, and is more common than you might think, for a device to develop a short circuit to ground. If ground is properly connected as it should be, a circuit breaker will trip and a fuse will blow almost instantly. Without safety ground being hooked up, it's possible for a malfunctioning electrical device to develop a live cabinet. Consider for a moment that anything standing on a more or less direct connection to the Earth is in fact grounded. It may not be a very good ground, but what is there is a ground nevertheless. It doesn't have to be a good ground for someone to come along, touch a malfunctioning or miswired device with a live cabinet and end up dying from the experience. It only takes a few milliamps across the human heart to stand a pretty good chance of stopping it.

Another question brought to mind by the lack of a ground connection at either the outlets or line cord on the 70 and 90 models is that of surge protection. APC claims these units have surge protection capability. An inspection reveals a lonely single MOV in line with the power input. MOVs, or Metallic Oxide Varistors, are common, cheap and passably effective surge suppression devices. They have the benefit of fast surge clamping time at a very low cost. MOVs work by turning into a short circuit under surge energy conditions and divert as much surge energy as they can to ground. Whatever's left over is clamped to a level still high above normal line voltage, with the hope that an attached device can withstand voltage in excess of its normal rating for a moment or two.

Only there's no ground here, at least not a proper Earth ground. Here in the United States, homes and small businesses with "split phase" power coming into the premises have a neutral that is connected to the center tap of a pole mounted utility transformer. At the same time, that center tap is bound to Earth ground--both at the power pole and at the location where electrical service enters a building's primary electrical panel. Or, again, it's supposed to be. Despite the presence of a nationwide electrical code, there is no restriction here in the United States (at least not on a federal government level) as to who can buy or install electrical equipment for a residential setting. A lot of particularly old but otherwise sufficient electrical wiring remains in service that may not have been done to current standards. And things do degrade over time.

This is also why devices sold as surge suppressors sometimes come with a notice stating that they must be connected to a grounded outlet. Otherwise they aren't very effective.

I can only suppose that APC intends the MOV inside these units to shunt as much of an incoming surge as possible through the neutral side of the power line, hoping that it'll ultimately get to ground. There's really only one problem with this: electricity always takes the path of least resistance! Chances are very good that your means of connection to the outside world IS properly grounded somewhere along the way, and even if the energy from a surge had to jump a few circuit traces over to reach that ground, it would be more likely to do so than to go through a much longer pathway all the way back to your building's grounding rod or that of the utility transformer.

(December 2015 update: Since writing the above, I researched the matter by looking at some MOV data sheets. This revealed that it is possible to place an MOV across the hot and neutral conductors of the AC power line and that some protection will be afforded by doing so.)

MOVs do have the unfortunate habit of decaying over time to the point where they are no longer useful. As they are by far and away the most common means of surge protection in almost any surge suppressor offered for sale, APC gets a pass on using them here. As with many power protection devices, you will not receive a warning when the MOVs are no longer functional.

Rather curiously, there is no provision on the BGE70 for network, coaxial or telephone line surge protection. Of course, without a safety ground, there would no place for surges coming in via these cables to go.


APC Back-UPS Connect BGE70 Circuit Board (scaled, click to see larger)

Click the above picture to see the 2.3 MB high resolution (2288x1712) original.

The primary (in actuality, only) circuit board is held in only by friction and one molded guide channel within the case. Rather surprisingly, APC included a disconnect for the built in outlets. Release it, and the circuit board is more or less free to come out for inspection. Be careful of the attached circuit breaker, which is also held in only by the relation of the top and bottom case panels.

There's not really a whole lot to say here. What's here looks like your average inexpensive low output capacity standby-type uninterruptible power supply. There is no voltage buck (reduction) or boost capability, not that you could expect such things at this kind of price point. Every electrolytic capacitor on the board is made by one of three companies: OST, CapXon or Chang. All of these companies are well known for having produced poor quality capacitors that vent electrolyte and subsequently fail. It is questionable as to whether or not their quality has improved since those times. At least some of them are 105C rated parts...

The battery charging circuit has a transformer isolated output and is based around a Power Integrations TNY274P highly integrated low cost regulator. Other portions of this circuit, particularly the controller IC, are directly connected the AC line. Its peak charging current is somewhere around 300mA, which drops to nearly zero when the battery is fully charged. Perhaps a state of charge test, a small amount of current is periodically drawn from or sent to the battery.

The circuit board is marked as part number 640-4219A-Z and as revision 1. It bears a code name of Mt,Whistler
[sic]. Exactly what this references is unknown. (Author's note: Since writing this I have come to know that some APC products were code named prior to release after various mountains. Other code names that I found were McKinley (CS350/500), Cerro Torre (BR1500), and Vail (BR800).)

A little bit of hot glue does wonders to quiet the onboard beeper down. If you really don't care in the slightest about having a warranty, and don't want to know when this unit goes on battery or reaches a critically low level of battery charge, you could simply remove the beeper. Be sure you disconnect all sources of power before tinkering inside the unit, and don't do anything if you're not sure or lack experience in electronics repair.

Setup and Installation

There's very little involved in placing the BGE70 into active service. APC provides fairly decent basic instructions to help you connect the battery, connect whatever equipment you wish to protect and ultimately get everything connected to power. While nothing is foolproof, those who can't get this unit set up might want to consider a different occupation.


I was curious as to what kind of runtime this unit might offer under a nearly fully loaded condition, and if it would remain in a safe operating situation under high load. APC claims these units will shut down when overloaded. The rating given for the BGE70 is 75 watts. I found a 65 watt plant light bulb in a portable fixture, plugged that into the unit and pulled the BGE70's plug. Runtime was approximately 21 minutes before a low battery alarm sounded, and 28 minutes before a shut down due to an exhausted battery took place. These figures will decline over time as the battery wears out.

Having connected an oscilloscope meter to the BGE70 while it was running on battery, I discovered that its output waveform is actually the usual "modified sine wave" type, at least until the battery starts to get weak. When that happens, the inverter's output gradually reaches a point where it does become a (somewhat sloppy) square wave.

APC Back-UPS Connect Normal Stepped Waveform Output APC Back-UPS Connect Squarewave Output (at a critically low battery level)

Click either picture to see it larger.

Other Issues

As the BGE70's battery drained, I noticed that its output voltage kept going up (tested with a true RMS meter). What started out as a perfectly reasonable 114 volt output soon rose to 121 odd volts AC. As the battery became critically low, however, behavior of the inverter became much more unstable. Output voltage rose to 130 volts AC and my Kill-A-Watt meter's display began to flicker in a rather unnverving way, suggesting a (very) poorly filtered output. This could cause damage or erratic operation of an attached device -- exactly the kind of thing that a power protection device is supposed to prevent! All this was present while driving a simple resistive load. Just how bad does an inverter have to be that it can't maintain stability under such a straightforward situation? What might it do in the face of highly inductive loads that are much more difficult to drive?

The BGE70 uses an APC RBC153 replacement battery. Searching around online did not reveal a generic source for this 12 volt, 4.2 amp-hour battery, as it has an unusual form factor. At best this leaves you paying a highly inflated cost for a new battery. At worst it could mean that a time will come when you can't actually buy a replacement battery. I choose to be optimistic here by thinking that third party battery suppliers will produce a compatible replacement at a fair price.


I feel as though the limitations of this product outweigh its benefits. It lasted surprisingly well under heavy load and only uses its alarm beeper sparingly. Two pin outlets preclude its usefulness with some very common pieces of network equipment. A battery of unusual shape and size locks you buying a replacement from APC at their very inflated prices, at least as of this writing in late 2015. Instability of the inverter as the battery level dropped has the potential to cause problems with some devices. I'm not sure the surge protection capability will actually function as intended, unless there is some aspect to its design that I am not aware of. There's also the matter of a power LED that's brighter than the sun.

Every product has compromises in its design. I feel the BGE70 has far too many compromises of a serious nature to recommend buying it.


If cost is a concern, my first recommendation would be to pick up a used uninterruptible power supply. Perfectly serviceable examples (possibly with worn MOVs, but that's a minor nit in my view) are being tossed out all the time for want of a replacement battery. Buy the battery yourself on the secondhand market (there isn't any significant difference in the brand), install it and enjoy many years of reliable service. Most of the time you can get the UPS for nothing and the batteries for less than $20. Sometimes you can even modify a unit to work from a cheap lawn tractor or car battery, so long as you know how to do so safely and don't massively overload the unit!

If bringing a rejected UPS back to life with a replacement battery isn't what you want to do, or doesn't fit into your lifestyle for some other reason, save up a little money and buy something bettter. A 500 volt-amp or ideally better UPS will run small loads for a VERY long time, much longer than these small purpose built units could ever manage. They'll have proper three pin grounded outlets and many models offer supplementary surge protection for communication lines and even the capability to communicate with a computer or other device so that an intelligent, graceful shutdown may be performed. And when the time comes, they'll take a standard, inexpensive replacement battery.

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Review Copyright 2015-2016 by William R. Walsh. Some rights reserved. Please view the terms and conditions, available from the top level page of this server, to see the terms governing the use of this material. Initial draft written around September 25th, 2015. Final review edited and published November 25th, 2015. Updated November 30th, 2015 with pictures of output waveforms and the internal primary circuit board. Updated again on December 10th, 2015 with additional MOV surge suppression related information. Charging circuit technical details updated on January 3rd, 2016. Possible explanation of code names added January 4th, 2016.