Voltage scaling, even to say 5V over 3.3V, seems to double the price per Farad or more...
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?
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.
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.
"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. "
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.
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, 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
As I mentioned in my first post, every two or three years I seem to be replacing my lead acids.
QuoteAs 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.
What brand/model UPSs and batteries do you feel are high quality?
QuoteAs 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.
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?
What brand/model UPSs and batteries do you feel are high quality?
QuoteAs 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).
I see the models for the batteries you recommend but not for the UPSs. Both companies make a broad range of products.
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?