Author Topic: UPS Supercapacitor Conversion  (Read 5276 times)

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Offline joeqsmith

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UPS Supercapacitor Conversion
« on: June 20, 2018, 03:07:11 am »
We lost our power a couple of times last week and my UPS is on the blink, again.  Most power dropouts in my area only last a second or so and I am thinking to setup a UPS using super capacitors rather than lead acid.   UPS requires 4 cells.  Cost is about $60/ea and they can last up to a couple of years.   

I ran some numbers on what I need for capacitance and started looking on Digikey.    I am really tempted to go with some of these ultra cheap caps and suspect they are like cheap CAT III rated handhelds and 10,000 mAH 9v transistor batteries.   

What's been your experience with cheep supercaps?   
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Offline DaJMasta

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Re: UPS Supercapacitor Conversion
« Reply #1 on: June 20, 2018, 03:15:45 am »
Are there such things as cheap high voltage supercaps?  Voltage scaling, even to say 5V over 3.3V, seems to double the price per Farad or more... I can't imagine trying to make a high voltage array with them.


I think the usual approach for high voltage large cap arrays is to have lots of much smaller high voltage caps in parallel with some sort of load balancing mechanism.  Each cap is probably only going to be 1-10mF, but with a large array you can get a fair bit of capacity.  I guess first things first, though, how much charge do these things need to store?  How much power is used up in the couple seconds it would take to switch on, regain input power, and switch off gracefully?  Would you still need a UPS for longer outages?

Also worth noting that "conversion" is not realistic.  This would be a totally new build.  Some bits of the UPS may be the same as the new one, but the response and charging mechanism for a lead acid cell is totally different from a capacitor array and when dealing with this sort of energy, they will not be compatible to just swap in caps.

Offline ConKbot

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Re: UPS Supercapacitor Conversion
« Reply #2 on: June 20, 2018, 04:18:37 am »
Voltage scaling, even to say 5V over 3.3V, seems to double the price per Farad or more...

51 percent more voltage, E=1/2CV^2 so 128 percent more energy at 5V than 3.3 for the same capacitance, so the cost per joule stored remains about the same  ;)
 

Online wraper

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Re: UPS Supercapacitor Conversion
« Reply #3 on: June 20, 2018, 05:06:16 am »
I ran some numbers on what I need for capacitance and started looking on Digikey.    I am really tempted to go with some of these ultra cheap caps and suspect they are like cheap CAT III rated handhelds and 10,000 mAH 9v transistor batteries.   

What's been your experience with cheep supercaps?
Dunno what numbers you calculated but it's not possible to replace lead-acid batteries with reasonably sized supercapacitors and retain reasonable capacity at the same time. Not to say that charge circuit in UPS is completely unsuited for this. Maybe it will somewhat work out if you attach pre-charged supercapacitors. As of discharge, after consuming relatively small part of already inferior capacity, UPS will detect that battery is empty and will cut off as voltage will drop with discharging unlike on battery which will hold around the same voltage until almost depleted.
« Last Edit: June 20, 2018, 05:09:11 am by wraper »
 

Offline joeqsmith

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Re: UPS Supercapacitor Conversion
« Reply #4 on: June 20, 2018, 08:39:35 am »
Are there such things as cheap high voltage supercaps?  Voltage scaling, even to say 5V over 3.3V, seems to double the price per Farad or more... I can't imagine trying to make a high voltage array with them.

I think the usual approach for high voltage large cap arrays is to have lots of much smaller high voltage caps in parallel with some sort of load balancing mechanism.  Each cap is probably only going to be 1-10mF, but with a large array you can get a fair bit of capacity.  I guess first things first, though, how much charge do these things need to store?  How much power is used up in the couple seconds it would take to switch on, regain input power, and switch off gracefully?  Would you still need a UPS for longer outages?

Also worth noting that "conversion" is not realistic.  This would be a totally new build.  Some bits of the UPS may be the same as the new one, but the response and charging mechanism for a lead acid cell is totally different from a capacitor array and when dealing with this sort of energy, they will not be compatible to just swap in caps.

Keep in mind, you are the one who mentions high voltage.   If it could hold my loads for 5 seconds, that would cover the vast majority of drop outs I see.  If it is out for days, I am running a genset.   Looks like someone has tried it.




I ran some numbers on what I need for capacitance and started looking on Digikey.    I am really tempted to go with some of these ultra cheap caps and suspect they are like cheap CAT III rated handhelds and 10,000 mAH 9v transistor batteries.   

What's been your experience with cheep supercaps?
Dunno what numbers you calculated but it's not possible to replace lead-acid batteries with reasonably sized supercapacitors and retain reasonable capacity at the same time. Not to say that charge circuit in UPS is completely unsuited for this. Maybe it will somewhat work out if you attach pre-charged supercapacitors. As of discharge, after consuming relatively small part of already inferior capacity, UPS will detect that battery is empty and will cut off as voltage will drop with discharging unlike on battery which will hold around the same voltage until almost depleted.

It seems you missed the second sentence:   
Quote
"Most power dropouts in my area only last a second or so and I am thinking to setup a UPS using super capacitors rather than lead acid. "
Obviously I am not looking for it to run for several minutes.  It's very rare our power drops out for more than seconds.    The calculations I have done are just to get an idea on the size I need to pull this off with my loads. 

Again, what I am asking is peoples experiences with these cheap caps.   If I buy a cap from a name brand supplier, I expect it will perform to their datasheets.  I have my doubts about these cheap caps I see.   I can see buying a 1000F cap and receiving a 10F part.   
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Offline james_s

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Re: UPS Supercapacitor Conversion
« Reply #5 on: June 20, 2018, 08:52:05 am »
Well I know the supercaps used in some of the Fluke multimeters and Davis weather stations are a known weak point. Failure with a leaky mess seems to be fairly common.
 

Offline DaJMasta

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Re: UPS Supercapacitor Conversion
« Reply #6 on: June 20, 2018, 09:15:25 am »

Keep in mind, you are the one who mentions high voltage.   If it could hold my loads for 5 seconds, that would cover the vast majority of drop outs I see.  If it is out for days, I am running a genset.   Looks like someone has tried it.


Fair, but what voltage do you actually need?  I'm not used to seeing UPSs lower than 12, and 12V is a fair bit for a supercap... and when I hear UPS, I generally think of mains output, in which case your DC storage voltage would not be too low.  If you mentioned what the output or the load was, it would be easier to tell what sort of application you're looking at  ;)

Regardless, if you're using an array with integrated charge controllers and your UPS doesn't need to last for any duration, then you're probably still losing out on recharge speed using the UPS's charging circuit, but maybe that isn't much of a problem.  I'd look for caps with a brand name on the cheap end, rather than just unnamed or unspecified, then just derate a bit for voltage.  Supercaps are always going to be less tolerant of ripple currents and heat, have a much higher ESR, and don't have the same long lifespan ratings as their electrolytic counterparts, so if your output can draw spikes of current it may be worth adding some standard electrolytics to effectively bypass the array to reduce ripple.  You can measure the capacitance yourself with a lab power supply with a current limit (or a voltage source and a resistor), a stopwatch, and a multimeter to verify the rated claim.  Maybe doesn't help pick a brand if you're buying them for a one-off all at once, but you can at least be sure you get what you paid for.

Offline joeqsmith

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Re: UPS Supercapacitor Conversion
« Reply #7 on: June 20, 2018, 09:31:32 am »
Ok, I've just never considered 12V or even 120V high voltage.  Yes, the caps are rated for a lower voltage but it's not a problem gang them up.  That's not really my concern, nor is how to evaluate their performance.  I am really interested in hearing about the experiences people have had buying cheap brands.   Some of these are a third the price.  Hard to believe they would perform very well.    Are there cheap brands people have had good results with, ones that should be avoided.   

Some of the new Eaton parts look interesting. 
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Offline T3sl4co1l

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Re: UPS Supercapacitor Conversion
« Reply #8 on: June 20, 2018, 09:50:24 am »
This is precisely the range where supercaps shine: time constants of seconds. :-+

Batteries are probably cheaper, smaller even, despite not being suited to such short durations -- probably just because they're a bigger commodity.  So, you never(?) see supercaps here.

Batteries are fine: it works just like electrolytic bypass of a much faster example, a switching supply.  A 10mJ electrolytic won't handle a 10us switching cycle, it'll have far too much ESR to do the job, or to do it without overheating.  But 1J together will.

Likewise, a 1kJ lead-acid won't handle a 1s dropout, but 100kJ together will.  As a bonus, it'll keep you propped up for minutes, not just seconds, on the off chance that you need such.

To put it another way: you're fundamentally worsening one performance metric of your system: support time.  What are you getting in return for that?  You aren't gaining efficiency, because this isn't one of those places where you only need what you use -- while that would be soothing to the OCD, :P the real need is availability, and if you aren't saving money or space on supercaps, why bother? :)

Now, if you're getting these drops so frequently that they're doing substantial damage to a battery that therefore needs frequent replacement, then you've got such a motivation: reliability.  You might still want to ask if it's worthwhile to sacrifice the support time by going to supercaps, versus just getting a bigger battery (that therefore can handle the surge demand better -- again, short time demands get distributed better and better over larger reservoirs).  Or getting a different chemistry, like a LiPo or LiFeP that can handle the demand with better life.

So, yeah, fundamentally, you're right in the sweet spot for supercaps. :) I just wonder if that's a sufficient cause, though, or if there may be other considerations that make you think, "oh, well, I suppose... oh well".  :-//

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Offline joeqsmith

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Re: UPS Supercapacitor Conversion
« Reply #9 on: June 20, 2018, 10:30:07 am »
This is precisely the range where supercaps shine: time constants of seconds. :-+

Batteries are probably cheaper, smaller even, despite not being suited to such short durations -- probably just because they're a bigger commodity.  So, you never(?) see supercaps here.

Batteries are fine: it works just like electrolytic bypass of a much faster example, a switching supply.  A 10mJ electrolytic won't handle a 10us switching cycle, it'll have far too much ESR to do the job, or to do it without overheating.  But 1J together will.

Likewise, a 1kJ lead-acid won't handle a 1s dropout, but 100kJ together will.  As a bonus, it'll keep you propped up for minutes, not just seconds, on the off chance that you need such.

To put it another way: you're fundamentally worsening one performance metric of your system: support time.  What are you getting in return for that?  You aren't gaining efficiency, because this isn't one of those places where you only need what you use -- while that would be soothing to the OCD, :P the real need is availability, and if you aren't saving money or space on supercaps, why bother? :)

Now, if you're getting these drops so frequently that they're doing substantial damage to a battery that therefore needs frequent replacement, then you've got such a motivation: reliability.  You might still want to ask if it's worthwhile to sacrifice the support time by going to supercaps, versus just getting a bigger battery (that therefore can handle the surge demand better -- again, short time demands get distributed better and better over larger reservoirs).  Or getting a different chemistry, like a LiPo or LiFeP that can handle the demand with better life.

So, yeah, fundamentally, you're right in the sweet spot for supercaps. :) I just wonder if that's a sufficient cause, though, or if there may be other considerations that make you think, "oh, well, I suppose... oh well".  :-//

Tim
I could care less about weight, size or efficiency and I've been clear about the lack of need for long uptimes.    Since I have been using a UPS, the number of times I have needed more than 5 seconds of up time is maybe a handful.  This is over the course of many years.

As I mentioned in my first post, every two or three years I seem to be replacing my lead acids.   I do have one now that has been in service for about five but it's rare.  The power where I have lived has always been generally stable.  It may drop out 4 or 5 times a year where it would have effected something I was doing.   

I mentioned what it costs per battery.  I just checked pricing and it seems on par with the last set I bought.  There could be a break even assuming the super caps don't prematurely fail but it was not really my goal to save money.   

Based on my personal experience with the mains, I am looking for a solution that gets me out of the battery swapping mode.   It's a perfect time to look into it as I mentioned in my first post, I currently need to replace them.
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Re: UPS Supercapacitor Conversion
« Reply #10 on: June 20, 2018, 10:55:04 am »
Quote
As I mentioned in my first post, every two or three years I seem to be replacing my lead acids.
Either you buy crap batteries or charging circuit in your UPS sucks. Good long life batteries easily last 5+ years in a decent UPS. BTW if by chance you buy original batteries from APC, usually they are a cheap Chinese crap with very expensive APC sticker slapped on top.
 

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Re: UPS Supercapacitor Conversion
« Reply #11 on: June 20, 2018, 11:05:47 am »
Quote
As I mentioned in my first post, every two or three years I seem to be replacing my lead acids.
Either you buy crap batteries or charging circuit in your UPS sucks. Good long life batteries easily last 5+ years in a decent UPS. BTW if by chance you buy original batteries from APC, usually they are a cheap Chinese crap with very expensive APC label slapped on top.
I think there's a lot of truth in that.
We see lots of ppl replacing UPS batteries on what seems like too regular basis of 1-3yrs and we all know a properly cared for SLA can last much longer than this.
Personally I think UPS designers universally cock up by setting charging voltages for cyclic use instead of standby usage and by doing so just the additional few hundred mV shortens SLA life dramatically. Do they do this to artificially inflate their UPS specs, who knows ?
Add to this that SLA do not like being deep cycled and it's no wonder their life is often shortened in UPS usage.

In the only basic knowledge I have of UPS it seems one solution might be to use a modern Cadmium lead automotive battery that can withstand slightly higher charge voltages.
« Last Edit: June 20, 2018, 11:07:29 am by tautech »
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Offline joeqsmith

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Re: UPS Supercapacitor Conversion
« Reply #12 on: June 20, 2018, 11:31:37 am »
UPS have been APC and Tripp lite.  Panasonic batteries for the most part.   Although I tried some from battery plus or something that lasted about as long.   I have an early APC that was the first one I bought.  I later bought a larger APC.  Battery life has been about the same between them all. 

I use Odyssey AGMs in the race bikes.  These are a total loss system (no charging system)  and the batteries get charged between runs.  These take a lot of abuse but about 2 years is what I expect for a service life.  My street bike typically does much better but no where near what I see with my car or truck batteries.  These seem to last about six.  The longest use LA battery I have in use looks to be 8 years old now.  It charges from the solar panel and runs the lights in my trailer.  This is a deep cycle marine battery.   

What brand/model UPSs and batteries do you feel are high quality?
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Re: UPS Supercapacitor Conversion
« Reply #13 on: June 20, 2018, 12:20:32 pm »
What brand/model UPSs and batteries do you feel are high quality?
UPS's, I have no idea and I base some of my previous comments on being given a APC 1000 that liked eating SLA's too. After some investigation, measurements and tests I came to the conclusion the charging circuitry was entirely responsible for battery life and all this was some years back. Of what I've seen online about UPS's since hasn't changed my view one iota.

Batteries, well SLA's are the most convenient for small portable UPS's and you can't get around that unless you go down the path of your Supercap proposal Joe or look at deep cycle LA's.
If we look at proper 'off grid' solutions, large flooded cell LA's are the traditional power storage solutions and are usually matched to charge capability and load conditions in order not to deep cycle them.
But Li Ion is starting to gain a foothold in solar installations as technology improves to manage them properly and obtain good life.
However campers and marine use also needs deep cycle capabilities and marine further mechanical strengthening to withstand the banging about they can get.
My buddy uses those Odyssey's too but not as total loss.

My overall preference of high capacity battery brands is Optima bar none and I've had 10yrs+ on occasion for agricultural/commercial use. (red top)

However for UPS it's still the charge voltage and deep cycle abuse that need be accounted for and properly managed. I'd be ripping the charging system down and making some adjustments as it may be the cheapest and best investment of your time.

Thinking out loud.... if the charge voltage sense divider resistors are some shit 10% part could that throw the sense circuit all out of whack compared to a prototype ?
Of course it could and the plonkers that build these things don't even insert a trimmer so they can be corrected within the proper range so to not f**k SLA's, one set after the other.  ::)
If these twits also have shares in a battery supply company, well that's pure genius !  >:D
« Last Edit: June 20, 2018, 12:39:39 pm by tautech »
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Offline ArthurDent

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Re: UPS Supercapacitor Conversion
« Reply #14 on: June 20, 2018, 01:03:29 pm »
I hate sealed lead acid batteries. It seems you never know they have died until you go to use them and they are absolutely dead, even when they have been on float charge all the time. Wet type NiCad batteries seem to last forever and I love them but are very expensive and aren’t suited for all applications. 

 I recently bought the same cheap 6 supercap bank (6 x 500F @16.2V/82F) shown in the previous video just to see if it would be usable for long term backup (2 days) on a piece of equipment I’m building that only draws about 40 ma at around 15 volts. After doing some testing like charging, discharging, and just letting them self discharge I found that of the six 500F/2.7V caps in the bank, 2 would not hold a charge that well but 4 had fairly low leakage. The 2 with high leakage were not useable for more than several hours before dropping to around .8 volts but the other 4 would stay at 2.6 volts for days. I removed the 2 bad supercaps to make sure it was the caps leaking and not the protective circuitry causing the discharge and it was the caps.

Even the 2 caps with high leakage were still able to produce high current output and when I tried draining the remaining .5 volt from one by shorting it with a resistor lead the lead got extremely hot and I had to drop it. Judging from how long it takes each cap to charge the capacity of all caps is probably within reason but it is leakage causing the self-discharge.

I also am not too sure of the protective circuit across each cap as it should put a load (2.5 ohms) across the cap when its voltage gets too high to try to keep the voltage across the cap under about 2.7 volts. It seems that when charging the bank some caps could charge above 3 volts and the resistors were not getting hot because the circuit had not turned on. A couple of circuits did work and the resistors got quite hot to the touch indicating the load had been put on the cap to discharge it to a safe voltage. As to charging the supercapacitor bank I have charged it at a rate as high as 5 amps with no problem.

If you are basically going to use these supercaps in a UPS which is always keeping them on charge and only using them for seconds or minutes every so often, I think they would work great for that application.  I would do a few charge/discharge cycles and measure the voltages on each cap to make sure you don’t have any defective caps like I found but other than that I think your plan should work.  You would still need 4 banks even though 3 of the 16.2 volt banks would be close.
« Last Edit: June 20, 2018, 01:10:55 pm by ArthurDent »
 

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Re: UPS Supercapacitor Conversion
« Reply #15 on: June 20, 2018, 02:57:01 pm »
What about lipo kept charged at 4-4.1V/cell?
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Re: UPS Supercapacitor Conversion
« Reply #16 on: June 20, 2018, 04:45:07 pm »
Quote
As I mentioned in my first post, every two or three years I seem to be replacing my lead acids.
Either you buy crap batteries or charging circuit in your UPS sucks. Good long life batteries easily last 5+ years in a decent UPS. BTW if by chance you buy original batteries from APC, usually they are a cheap Chinese crap with very expensive APC sticker slapped on top.
Something nobody has mentioned yet is the Achilles heel of lead acid batteries - TEMPERATURE. The ups next to my work computer has the battery at easily 30deg C. I’ll bring in the temp probe tomorrow and see. The 13.65V charging voltage is only relevant at 20 deg C and should decline with increasing temperature.

The optimum operating temperature for the lead-acid battery is 25°C (77°F). As a guideline, every 8°C (15°F) rise in temperature will cut the battery life in half. VRLA, which would last for 10 years at 25°C (77°F), will only be good for 5 years if operated at 33°C (95°F). Theoretically the same battery would endure a little more than one year at a desert temperature of 42°C (107°F).

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Online wraper

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Re: UPS Supercapacitor Conversion
« Reply #17 on: June 20, 2018, 06:35:51 pm »
UPS have been APC and Tripp lite.  Panasonic batteries for the most part.   Although I tried some from battery plus or something that lasted about as long.   I have an early APC that was the first one I bought.  I later bought a larger APC.  Battery life has been about the same between them all. 

I use Odyssey AGMs in the race bikes.  These are a total loss system (no charging system)  and the batteries get charged between runs.  These take a lot of abuse but about 2 years is what I expect for a service life.  My street bike typically does much better but no where near what I see with my car or truck batteries.  These seem to last about six.  The longest use LA battery I have in use looks to be 8 years old now.  It charges from the solar panel and runs the lights in my trailer.  This is a deep cycle marine battery.   

What brand/model UPSs and batteries do you feel are high quality?
Panasonic and others have different battery series. The same company may have series which are rated for 2 or 3 times longer life than others. Say compare first one with the last one (the last one is for extreme temperatures).

http://www.csb-battery.com/upfiles/dow01524110112.pdf
http://www.csb-battery.com/upfiles/dow01524110240.pdf
http://www.csb-battery.com/upfiles/dow01520317548.pdf
http://www.csb-battery.com/upfiles/dow01520318304.pdf

In my experience Riello UPS are very good. Very reliable, silent, batteries inside or in separate enclosure stay cool and last a long time. APC IME is a turd, not reliable at all. Supplied batteries likely will be some crap like Kung Long. Eaton is reliable, but fans were extremely loud the last time we bought those (9130 series).
I buy long life CSB batteries for UPS used at my job. They are affordable and quiet good. They also often come in decent UPS like Riello and Eaton. BTW Hitachi bought them 2 years ago, brand remains the same though.
« Last Edit: June 20, 2018, 07:00:31 pm by wraper »
 

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Re: UPS Supercapacitor Conversion
« Reply #18 on: June 20, 2018, 07:19:34 pm »
You could always try some Enersys Cyclon cells (cylindrical wound SLA). They tend to have very long life (I've got a few 20yr old ones), high energy density and low self-discharge, also very low internal resistance. They're about as reliable as it gets in SLA technology.

https://www.enersys.com/EMEA/CYCLON_Batteries.aspx?langType=1033
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Offline joeqsmith

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Re: UPS Supercapacitor Conversion
« Reply #19 on: June 20, 2018, 07:45:18 pm »
What brand/model UPSs and batteries do you feel are high quality?
Panasonic and others have different battery series. The same company may have series which are rated for 2 or 3 times longer life than others. Say compare first one with the last one (the last one is for extreme temperatures).

In my experience Riello UPS are very good. Very reliable, silent, batteries inside or in separate enclosure stay cool and last a long time. APC IME is a turd, not reliable at all. Supplied batteries likely will be some crap like Kung Long. Eaton is reliable, but fans were extremely loud the last time we bought those (9130 series).
I buy long life CSB batteries for UPS used at my job. They are affordable and quiet good. They also often come in decent UPS like Riello and Eaton. BTW Hitachi bought them 2 years ago, brand remains the same though.
[/quote]

I see the models for the batteries you recommend but not for the UPSs.  Both companies make a broad range of products.
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Offline joeqsmith

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Re: UPS Supercapacitor Conversion
« Reply #20 on: June 20, 2018, 07:59:05 pm »
Quote
As I mentioned in my first post, every two or three years I seem to be replacing my lead acids.
Either you buy crap batteries or charging circuit in your UPS sucks. Good long life batteries easily last 5+ years in a decent UPS. BTW if by chance you buy original batteries from APC, usually they are a cheap Chinese crap with very expensive APC sticker slapped on top.
Something nobody has mentioned yet is the Achilles heel of lead acid batteries - TEMPERATURE. The ups next to my work computer has the battery at easily 30deg C. I’ll bring in the temp probe tomorrow and see. The 13.65V charging voltage is only relevant at 20 deg C and should decline with increasing temperature.

The optimum operating temperature for the lead-acid battery is 25°C (77°F). As a guideline, every 8°C (15°F) rise in temperature will cut the battery life in half. VRLA, which would last for 10 years at 25°C (77°F), will only be good for 5 years if operated at 33°C (95°F). Theoretically the same battery would endure a little more than one year at a desert temperature of 42°C (107°F).
Good point.  My home lab will get well into the 90s F (30s C).  The UPSs internals will raise that.   

My one APC UPS must be well over 25 years old now.  UL and CSA listed.   The only thing I ever do with it is replace the battery.   
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Re: UPS Supercapacitor Conversion
« Reply #21 on: June 20, 2018, 08:02:31 pm »
I see the models for the batteries you recommend but not for the UPSs.  Both companies make a broad range of products.
I think all Riello models we have are 8kVA or more. They have like 20y difference in age. Probably new models came out anyway since we bought the last batch. I don't recall a single one to fail. While APC were pain in the ass, even expensive 10 kVA.
EDIT: It's not that I recommend all of those batteries. It was more like for comparison. I would avoid GP series which are cheapest but have relatively short life and would go for at least GPL series. And would prefer XTV if they will be placed in hot environment.
« Last Edit: June 20, 2018, 08:18:00 pm by wraper »
 

Offline joeqsmith

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Re: UPS Supercapacitor Conversion
« Reply #22 on: June 20, 2018, 08:03:42 pm »
Quote
GP series are what often comes in UPS from a factory (cheapest). As you can see in the datasheets all of them are rated for standby service. Do you really think that batteries used in UPS have written "for UPS" in the datasheet. Some of them may have but it's basically the same as "for audio" electrolytic capacitors.
BTW, check again:
Quote
    Design for Standby Power Applications

Quote
    Design for Standby Power Applications at Extreme Temperatures

« Last Edit: Today at 07:57:04 pm by wraper »

Which Riello models are you recommending?
How electrically robust is your meter?? http://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Online wraper

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Re: UPS Supercapacitor Conversion
« Reply #23 on: June 20, 2018, 08:04:37 pm »
Which Riello models are you recommending?
Already deleted before you posted, understood your post wrong. To recommend something, requirements are needed first.
 

Online David Hess

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Re: UPS Supercapacitor Conversion
« Reply #24 on: June 20, 2018, 08:48:48 pm »
I have messed around with this idea a bit in the past and found that some UPS charge circuits become very unhappy with the low impedance load presented by a discharged capacitor bank.  So besides charge balancing, some type of charge control should be added.
 


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