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Super Capacitor

The supercaps in parallel allow you to use a smaller battery bank than you otherwise would.

eg, if you have a 200a surge load and have batteries that can’t exceed 1c, you need a 200ah pack.
with a supercap in parallel you might only need a 100ah pack.

You can use a 25ah lifepo4 pack in parallel with a supercap to start a truck engine.
 
@toms thank you. I have attached the two batteries I use. 2 banks 48V about 37-38kw each, 2V x 24S and 8V x 6S x 6P. Could you have a look at the max surge load for these? Thank you
 

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From the data sheets, the 800ah have a 6000a for 5 second surge rating.
The 135ah have a 1350a for 5 second surge rating. (7.5C / 10C)

Now it’s up to you how much you trust the manufacturer.

I limit the discharge current of my LiFePO4 to 1C
 
The supercaps in parallel allow you to use a smaller battery bank than you otherwise would.

eg, if you have a 200a surge load and have batteries that can’t exceed 1c, you need a 200ah pack.
with a supercap in parallel you might only need a 100ah pack.

You can use a 25ah lifepo4 pack in parallel with a supercap to start a truck engine.
This is a good example of a response I was formulating. In Physics 101 (back when we solved complex mathematics with paper and pencil) we learned there was no free lunch, and every machine (electrical, hydraulic, mechanical, electronic) loses some energy as waste heat. Work factor I believe we called it. Efficiency is the more modern term.

So, the OP might be able to function with a smaller battery bank (or a battery bank with a lower "C" discharge rating) by adding capacitors on the DC side of his inverter, but when the day is done, he has used no less energy (in fact a bit more) due to the added capacitors.
 
I should point out that the Internet, Websites and Forums such as this are not exclusively U.S.A.-centrtic. We in other continents and countries have had access for some time now.

As of today 29/07/2020 in S.E. Asia, currency exchange puts 3,000f Ultra-caps @ approx. US$150.00 per six pack = $300 for twelve. Prices vary of course on volume. A balancer is so cheap in comparison, not worth any concern.

If the asking price is US$700 - $800 I would strongly suggest looking for another source.

View attachment 18707
Other countries use OUR internet? Say it isn't so!

Sorry to jump off topic, but you reminded me of a pair of Bolle sunglasses I bought at a French gas station (petrol station to you) for 30 Francs (maybe USD 6.00 at the time). Back in the good old USA, those were $100 sunglasses.
 
Any one using super capacitors for devices with large start up requirements? In my case a 1.5 hp deep well pump. It takes a heap of energy to start, about 4 times the energy required to run. It appears that a correctly designed super capacitor should make this task more efficient in terms of actually starting the pump, time to start pump and load drawn from battery bank. I have made the calculations and ready to build, but can't find anyone who's actually done it for comparison. It seems that super capacitors implemented in solar systems is an area that is currently under explored. Perhaps I haven't looked thoroughly. Thanks in advance.
I have a Maxwell 83F supercapacitor bank connected to the DC side of an 8KW inverter to take the hit from my well pump startup. It does help the voltage drop on the batteries for the motor startup. Our well pump in over 300 feet deep! It's 220 volt on a 30 amp AC breaker. Upon startup I've watched the DC current hit 800 amps, but that is with other household lighting, fridge, TV on at the same time. I haven't put a shunt between the super cap to measure the ratio between the caps and battery bank when a high current appliance kicks on. Now that I said that....interested to see how the caps discharge in the few seconds of inrush. The super cap bank is capable of discharging around 250 amps if I'm not mistaken, I have started my diesel truck with those capacitors which is really awesome.
 
Not where I am, S. E. Asia, far cheaper than batteries or a bigger inverter (very expensive here, solar is a relatively new tech in my area). I only need enough voltage to match my 24v batteries. Cost is diy @ au$20.00. Don't know offhand what this in us$.
Just be aware that there are two very different kinds of "supercapacitors."

The first kind are intended to supply power to very low power circuits for hours, or days, usually for ram memory backup, programmable digital equipment that might forget settings during a power outage. These are dirt cheap, and have a very high internal resistance and are totally incapable of supplying any surge power to an inverter. You can tell, because they have really skinny wires for connection.

The other type of supercapacitor have huge current potential and stored energy, and have large bolted connections, they are also horribly expensive.

I doubt if anything you can buy for $20.00 will start any kind of pump, or even a small toy hobby motor.
 
Starting AC motors is the same as starting DC motors, they need the power now. A 3000F capacitor has @ 3watts capacity , a ac capacitor 45uf to 100uf less that. But on line voltage it has a lot of punch to melt a 16 penny nail .

Back before most of you were a twinkle in your fathers eye , they used a ac capacitor to start heavy loads. A soft start is nice but can be costly.
A simple 45uf to100uf oil run capacitor with a 20a circuit breaker in a metal box will do the job quite nicely and simply cheap to repair .
A run capacitor
https://www.ebay.com/itm/124252751950?hash=item1cee0a884e:g:lr8AAOSwwYpfBhte
Saw mills use this tech before the soft starts came out. Putting large starting loads thru a inverter is not necessary way to go . Charging the
capacitor takes only a fraction of a second.

Just a possible suggestion

Jim jr
 
Capacitors on AC motors provide phase shift, either for a bit more torque or to improve power factor.
DC motors (and brush-type universal AC/DC motors) might draw lots of current and start fast if voltage holds up, but also can start/run on reduced voltage. They have phase shift by design so provide good torque even when turning slower.

Midnight did a demo of their "Rosie the Inverter" starting four De Walt compressors simultaneously.
That is apparently a pretty capable inverter, but also those are brush-type motors.
A different test was a single induction motor water pump.
Figure an inverter can start about 1/4 as much induction motor as brush-type motor.


True soft starts (as opposed to hard-start kits) are quite costly, several hundred $$. I haven't used them, but people here who do report dramatic reductions in start-up current, a factor of several times. It allows large A/C on RV to start with a modest generator.

The AC capacitor and suitable breaker should help for on-grid. Powered by an inverter, you can't get any more than the inverter can deliver, and that varies considerably between brands.
 
Capacitors on AC motors provide phase shift, either for a bit more torque or to improve power factor.
DC motors (and brush-type universal AC/DC motors) might draw lots of current and start fast if voltage holds up, but also can start/run on reduced voltage. They have phase shift by design so provide good torque even when turning slower.

Midnight did a demo of their "Rosie the Inverter" starting four De Walt compressors simultaneously.
That is apparently a pretty capable inverter, but also those are brush-type motors.
A different test was a single induction motor water pump.
Figure an inverter can start about 1/4 as much induction motor as brush-type motor.


True soft starts (as opposed to hard-start kits) are quite costly, several hundred $$. I haven't used them, but people here who do report dramatic reductions in start-up current, a factor of several times. It allows large A/C on RV to start with a modest generator.

The AC capacitor and suitable breaker should help for on-grid. Powered by an inverter, you can't get any more than the inverter can deliver, and that varies considerably between brands.
(not to be argumentative )

You provided a more technical answer than me , but the old farts before us got the job done with a limited amount of power also, whether it comes from grid tie or inverter , 1.5hp pump is still @ 1140 running watts , well within the 4kw inverter . Its just a matter of response time to get the pump going. A ac capacitor can provide a quicker response time or "boost" without going thru the inverter. I may not have the education you have , but I know what has worked in past decades before the solid state transistor .
 
Starting AC motors is the same as starting DC motors, they need the power now. A 3000F capacitor has @ 3watts capacity , a ac capacitor 45uf to 100uf less that. But on line voltage it has a lot of punch to melt a 16 penny nail .

Back before most of you were a twinkle in your fathers eye , they used a ac capacitor to start heavy loads. A soft start is nice but can be costly.
A simple 45uf to100uf oil run capacitor with a 20a circuit breaker in a metal box will do the job quite nicely and simply cheap to repair .
A run capacitor
https://www.ebay.com/itm/124252751950?hash=item1cee0a884e:g:lr8AAOSwwYpfBhte
Saw mills use this tech before the soft starts came out. Putting large starting loads thru a inverter is not necessary way to go . Charging the
capacitor takes only a fraction of a second.

Just a possible suggestion

Jim jr
Jim,
This makes a lot of sense to me, small capacitors at line voltage pack-a-punch, use the leverage!
 
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