UPS Battery Backup for Segway "Top-up"

[hotpink]

Hi All,

I run a beachfront boardwalk Segway tour with about 15 Segways and need to move our Segways to the beach side of the boardwalk between tours, where their are no electric outlets. I am wondering if I can get some UPS battery backups (usually used for preventing computers from crashing if the electricity shuts off) to "top off" the Segways charge between tours (quieter than a generator). Anyone have any idea of how many Battery Backups I would need and what size each of them would have to be?

Thanks for your help!

[jgbackes]

I think you will find that a Honda 2000i generator is so quieter than you think. It's been computed before, but as I recall it takes 8hrs from the Unofficial Segway Battery FAQ...

A fully drained Segway has been reported to consume about 0.8 kWh during a 12 hours charging cycle so to compute the number of amps needed simple math...

If you want to charge 15 of them at a time...

.8kWh / 12h = 66.666kW
66.666kW / 110VAC = .6060 amps

So, you need about .6 amps per Segway or 15*.6a * 110VAC = 990Watts

For every hour you want to charge the Segways you'll need about 1KiloWattHour of power.

A Honda 2000i generator has about twice that capacity, but has an economy mode that only runs the engine has hard as required. It is VERY quiet.

It looks like for the same money you can purchase an "APC Smart-UPS 1500" Don't forget you're going to have to plug the UPS into the main power every evening to charge it up.

Personally I'd go with a generator and convert it to run on propane, but that's just me.

Propane Conversion Kits

[KSagal]

I found that when charging from my car via inverter, that charging two machines at the same time had some start up characteristics I was not expecting.

I know that charging from an inverter in your car is not exactly the same as being asked, but I found that the machines seemed to draw a larger amperage/wattage at startup, enough to confound my inverter.

If I just plugged in both machines and started the inverter, a 400 watt inverter would be overloaded. However, if I staggered the start of the charge cycle, even if only by several minutes, that same inverter had no problem.

The conversions I saw here seemed to indicate a flat line power draw for 12 hours, but I did not find that to be entirely accurate. Of course, I offer no proof to my observations, just my often faulty memory.

Any thoughts? Contradictions, confirmations, anyone?

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Originally Posted by hotpink

Hi All,

I run a beachfront boardwalk Segway tour with about 15 Segways and need to move our Segways to the beach side of the boardwalk between tours, where their are no electric outlets. I am wondering if I can get some UPS battery backups (usually used for preventing computers from crashing if the electricity shuts off) to "top off" the Segways charge between tours (quieter than a generator). Anyone have any idea of how many Battery Backups I would need and what size each of them would have to be?

Thanks for your help!

You really didn't supply enough information about how much "top off" would be required, but I made some guesses, and here's the approximate "bottom line".

You would need 15 UPS units, of the largest size "portable" UPS you could get. For instance, APC model BR1500G. These cost about $250 each retail, and weigh about 30 pounds each. [Alternatively, fewer UPS units and a number of external batteries]

Of course, you're presumably going to have to move all of that stuff to and from the beach side each day.

The alternative, of course, is a generator and associated fuel. Aside from a bit of noise, you'll probably get comments about greenhouse gas emissions.

You could explore solar panels. I'm guessing that roughly 100 square feet of panels would be needed - but that's a very rough guess based on no information about your tour characteristics, weather, hours of operation, etc.

I suspect that the above doesn't help a lot.

[Bob.Kerns]

I'm afraid the response aren't quite what you need, because nobody is addressing some basic questions that you need to answer.

(Despite that, there's helpful information in those responses!)

Here's the thing to consider: what does "top off" mean? So long as your UPS can supply power at a sufficient rate to operate at all, you can basically put however much energy you have in UPS's into your batteries, and gain that much range. When depleted, your UPS will no longer function, but you'll still have that gain. The question isn't how much UPS power you'd need to charge a Segway, or even to operate for a particular period of time. Rather, how much additional charge is worth it?

I don't recall the exact details, and I'm not willing to search for them today,but hopefully, this will give you enough of a lead to find them yourself, or you can perform some simple measurements with an inexpensive load meter and work it out yourself:

The Segway starts off at a full charge rate, and then backs off to an intermittent mode. So you'll need to be able to handle the full power demand of each Segway -- I think that's around 100-120 watts. But by "handle", I don't mean you need a 120W supply; at best, that would work only briefly. I would guess a 200W supply would work, but it would depend on how optimistic the rating is, whether it would handle that on a sustained basis. My experience with consumer UPSs is they tend to be a bit over-optimistic

But in calculating, it is important to realize that the Segway, when charging from an empty battery for 8 hours, does not spend that entire 8 hours charging at full rate. For some period, it charges at full rate, and then backs off. This means your UPS will drain faster than you would expect, from calculating the entire Segway energy budget and dividing by 8 to get charge per hour.

But it also means, if you have sufficient energy available, 1 hour of charging will accomplish much more than you would think, dividing by 8. Rather than 24/8 = 3 miles of range per hour of charge, you'll get quite a bit more benefit.

Rather than the 6.060 average amps that Jeff cites, your current draw will be more like 1A, because you're in the main part of the charging cycle, at least initially.

The approach I would take is to measure. Get a Kill-o-Watt meter (cheap and useful!), run a Segway through your typical regime, plug it in through the Kill-o-Watt meter, for the expected charging period, and collect the following information:

1) Initial charging current (amps) and power (watts). You will use this in designing the power output requirements for your solution. As I point out above, and as Karl's experience relates, you'll want some headroom on this.

2) Total energy consumed (KWh). This will tell you how much battery capacity your UPS solution needs, to charge for this period of time. Be aware that lead-acid batteries don't like deep discharge; it will live longer -- and you'll have more flexibility -- if you add some extra capacity here.

Then I'd unplug the Segway, and ride around on it, until it gets down to around the original state of charge, before you plugged it in. Unfortunately, this won't be a very precise measurement. You can refine it if you bring it down to, say, 50%, and plug it in just as the info key display switches from one level to the next, but it still won't be very precise. You could average a number of trials as well...

What this will tell you, is how much additional range you got by plugging it in. I would expect each additional mile of range to require no more than 15 minutes, and probably more like 10 minutes. I'd be suspicious of any numbers outside this range.

But based on this, you can decide whether you need the full capacity for the available time, or if you would settle for less capacity, allowing the UPS to deplete before the time available runs out. But again, this will reduce the life of the UPS! But you could allow extra capacity, and put them on a timer.

Or you could simply accept the reduced life, spend less money, and have a lighter-weight solution. A good UPS should protect against over-discharge anyway, so you shouldn't get into really damaging situations. I haven't tried operating a UPS in this mode! But it strikes me as a reasonable tradeoff to make.

One final caveat -- if you do decide to charge for a reduced period of time, I would re-measure the total energy consumption, over that period of time. Since the power consumption is different at different times in the charging process, you may get inaccurate results if you charge for half the time, and assume you will only consume 1/2 of the energy.

[KSagal]

Just to toss in some more anecdotal information, I used to glide a bit, and I have a friend who lives about a 1/2 mile from my home. In years past, (before LiIons) I would glide and find myself wondering if I would make it home. Last bar was blinking, and sometimes already out, when I would pass this man's house.

Often times, I would stop, and we would chew the breeze for 15 minutes or so. I would plug into his garage when we spoke. I do not think I ever plugged in for even a half hour.

I would often increase at least a bar and often two or more from this 15 minute charge.

Back in those days, I attributed a significant portion of that gain to the display of a surface charge, (an increase of voltage due to lack of load) but once under way again, the bars or most of them did remain.

Surely, if the 15 minutes of charge were part of a linear 8 hours of charge time, it would only account for 1/32nd of the charge, or some very minimal increase, less than the display could show. It never was that small, and the machine always showed the impact of this short charge time...

[vantramp]

My thoughts would be to skip the UPS. In my Roadtrek, we have 2500 watt Pure-sine inverter/charger and 220ah of 12V AGM deep cycle batteries. We found the inverter used for $350 (Xantrex Prosine 2.5) on CL and it has worked perfectly for the last 3 years.

I know that pure-sine inverter/chargers are coming down in price and decent sized units can be had for well under a grand new these days. If you were to mount one in your transport vehicle with a decent battery bank(sized according to your requirements), you could charge the bank overnight from a plugin at home, and even tie the system into your vehicles charging system as well(for replenishing on longer drives). You should be able to charge your Segs as needed that way and with no generator noise.

Figuring the math for battery bank and inverter size is pretty easy, but plan on double the battery bank size as taking them to more than 50% DOD (Depth of discharge) will reduce their lifespan. Also you would want to account for inverter overhead which is usually listed in the specs of decent systems.

The Kill-O-Watt mentioned is an excellent idea for figuring actual draw. We have one as well and it can be quite an eye-opener!

The side benefit of a system like this is if there if the power goes out and you need use of a microwave etc.

Hope that gives you some more ideas.

-Mike

[Bob.Kerns]

Originally Posted by vantramp

My thoughts would be to skip the UPS.

That's a very good point. A UPS is a battery, charger, and inverter, plus control circuitry, surge protection, monitoring circuits and software, etc -- overkill for this application.

I presume the attraction is that they are plentiful, easy to get, and easy to put into service. There's nothing wrong with that thinking, but don't be locked into that idea. You may find that all those extras don't give you the most bang for your buck, compared to batteries + inverter.

Do be careful with large charged batteries. They need to be well secured, and well protected against accidental contact and short circuits. It's not hard to get molten metal flying every which way, if you, say, drop a wrench in the wrong place. And they're dense and heavy -- not something you want flying around in a passenger compartment in a vehicular accident.

A UPS deals with some of the safety issues for you, but you'll still want to secure them.

Dealing with the safety issues isn't hard; it just needs a little thought and ingenuity.

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Originally Posted by hotpink

Hi All,

I run a beachfront boardwalk Segway tour with about 15 Segways and need to move our Segways to the beach side of the boardwalk between tours, where their are no electric outlets. ...

Why do you need to "recharge"?

I'm actually asking for some details about your need. How long (distance) is one tour, how much (percentage) of the battery charge is used per tour, and how many tours per day? And do you take the Segways back somewhere over night, where they can get a full recharge?

[vantramp]

Originally Posted by Bob.Kerns

Do be careful with large charged batteries. They need to be well secured, and well protected against accidental contact and short circuits. It's not hard to get molten metal flying every which way, if you, say, drop a wrench in the wrong place. And they're dense and heavy -- not something you want flying around in a passenger compartment in a vehicular accident.

Agreed! Attention to details really is important for this type of project. Solid installation, proper fusing, correct cable type & gauge to handle the amperage etc. Still very well within the capabilities of most folks if they take their time and do proper research.

I detailed my installation (with pictures of course) on my blog if anyone ever wants to see what's involved.

-Mike