Portable Power Stations

[wingnut771]

this one sounds like the one

Geewiz 2200W Portable UPS Power Station Kit - 2000Wh LIFEPO4 / Pure Sine Wave / 2HR Quick Charge - 3x SA Sockets - 3500 Cycles Lithium LifePO4 (2 YEAR WARRANTY)

Pure Sine Wave - AC Output: Provides continuous and stable power for your equipment Dual-Fan Cooling: Optimal heat dissipation with two cooling fans Multiple Safety Features: Protects against short-circuiting, overheating, over-current, over-voltage, and more Quick Charge: 2-hour charging from...

www.geewiz.co.za

That gives me Déjà vu feelings.

 

[leon.davibe]

I'm actually thinking of using the old (inefficient) UPS to charge the new (efficient) Geewiz during long power failures, as a safe option.
I was just wondering if one could bypass the losses, by using the old UPS batteries to charge the new UPS through DC input, but it looks like the risks aren't worth it....

@leon.davibe thanks for your valued and considered inputs, as always!

yea if it was an old device but even then if you use a buck converter you may find 85-93% efficiency so lets say you have load of 400w. looking at 28-60w anyways so adding complexity for almost and maybe even same losses

 

[wingnut771]

yea often there is a reason as much as i hate these all in ones

maybe bought with camping dual purpose or manageable size for the wife to be able to cart around too

Yeah, I would sell the 2 x 100Ah LFP's and use that money for some PV panels.

Still don't know what was wrong with the 1000W 2.5kWh setup.

 

[wingnut771]

I'm actually thinking of using the old (inefficient) UPS to charge the new (efficient) Geewiz during long power failures, as a safe option.
I was just wondering if one could bypass the losses, by using the old UPS batteries to charge the new UPS through DC input, but it looks like the risks aren't worth it....

@leon.davibe thanks for your valued and considered inputs, as always!

What makes you say this?

 

[wingnut771]

yea if it was an old device but even then if you use a buck converter you may find 85-93% efficiency so lets say you have load of 400w. looking at 28-60w anyways so adding complexity for almost and maybe even same losses

Lets leave buck converters out of this thread and keep things "simpler".

 

[Bundu]

What makes you say this?

I measured it

 

[leon.davibe]

Lets leave buck converters out of this thread and keep things "simpler".

can just imagine what you will say about my MacGyver car charger thanks to JUST CHLOR donor device
i have a lekker beefy car charger that can charge any battery from 3v to 16v thanks to 10 step voltage selector

so could charge a 2.3v LTO cell on its lowest setting and could actually push 5A on a close to full 4s lifepo4 , none of this taper down of the amps, if it tapers down to low for my liking i just dial up the next voltage setting

 

[wingnut771]

I measured it

Measured what?

 

[wingnut771]

can just imagine what you will say about my MacGyver car charger thanks to JUST CHLOR donor device
i have a lekker beefy car charger that can charge any battery from 3v to 16v thanks to 10 step voltage selector

so could charge a 2.3v LTO cell on its lowest setting and could actually push 5A on a close to full 4s lifepo4 , none of this taper down of the amps, if it tapers down to low for my liking i just dial up the next voltage setting

TLDR

 

[Bundu]

Measured what?

yes

 

[Zuner]

yes

lol, i agree with Wingnut, this seems like drastic overkill.
What are you powering ? cause the 2x12v100ah batteries aren't exactly low capacity, that a few watts of ineffiency warrants this response.
rather would have bought 2 more of them and parralel them all up and forget about loadshedding.

back to the question, I would not try this without proper precautions as leon.davibe said. normally i fire from the hip, but R20k is a lot to burn.

 

[maumau]

LOLZ at @wingnut771 enjoying his Saturday evening

 

[Bundu]

lol, i agree with Wingnut, this seems like drastic overkill.
What are you powering ? cause the 2x12v100ah batteries aren't exactly low capacity, that a few watts of ineffiency warrants this response.
rather would have bought 2 more of them and parralel them all up and forget about loadshedding.

back to the question, I would not try this without proper precautions as leon.davibe said. normally i fire from the hip, but R20k is a lot to burn.

my trolley is only 1000VA, so it tripped when I put my fridge and freezer on it. Starting current on fridge can be around 9A. Old fridge.
The new Geewiz handles both easily and TV, PVR, Laptop and lights, as well as a small heater.
The Geewiz is compact enough to take with me on holiday and is extremely quiet.
My trolley was a bad buy

 

[Zuner]

my trolley is only 1000VA, so it tripped when I put my fridge and freezer on it. Starting current on fridge can be around 9A. Old fridge.
The new Geewiz handles both easily and TV, PVR, Laptop and lights, as well as a small heater.
The Geewiz is compact enough to take with me on holiday and is extremely quiet.
My trolley was a bad buy

Okay i see, I don't think the trolley is as bad as you think, only that it doesn't meet your needs.
Bare minimum to test is a fast blow fuse, and as leon.davibe mentioned a breaker to kill the connection if need be. don't count on the breaker to act as a fuse.

But realistically I think it's too much effort and risk. If it were me, i would just use the 1000va to charge the compact, the losses aren't so bad vs the effort. You have plenty of battery capacity to last many hours.

 

[leon.davibe]

Okay i see, I don't think the trolley is as bad as you think, only that it doesn't meet your needs.
Bare minimum to test is a fast blow fuse, and as leon.davibe mentioned a breaker to kill the connection if need be. don't count on the breaker to act as a fuse.

But realistically I think it's too much effort and risk. If it were me, i would just use the 1000va to charge the compact, the losses aren't so bad vs the effort. You have plenty of battery capacity to last many hours.

@Bundu plus the losses mentioned is standby losses (which can be avoided by just switching the device off /unplug once fully charged lithium doesn't need to be floated to stay full, sure the voltage will settle making some think it has lost charge which isn't the case), inverting losses still has to be calculated though but most likely they will be same ball park

 

[Park@82]

...

I would reckon the item will charge as if a solar panel is connected the max amps of what the charge controller can handle

If trying it for the first time i would use a breaker to be able to cut the connection quick

i would think using a buck converter that can limit the current to not exceed the max amps specified. May also be a nice insurance ...

As I understand it, volts are pushed and current is pulled by the load.

So if the provided volts falls within the maximum that the device can accept I don't see any problem.

Lets take my Ecoflow River for example, it supports 200W, 10-25V, 12A of solar input.
I connect a 12V 50A (Max Discharge Current) LFP to it and I get up to around 140W from it IIRC.

12V x 12A = 144W.

With solar panels on these portable power stations one can exceed amps but one should never exceed VOC. Is this wrong and why?

 

[leon.davibe]

As I understand it, volts are pushed and current is pulled by the load.

So if the provided volts falls within the maximum that the device can accept I don't see any problem.

Lets take my Ecoflow River for example, it supports 200W, 10-25V, 12A of solar input.
I connect a 12V 50A (Max Discharge Current) LFP to it and I get up to around 140W from it IIRC.

12V x 12A = 144W.

With solar panels on these portable power stations one can exceed amps but one should never exceed VOC. Is this wrong and why?

No agree with you on most

Not sure how they will behave if you intensionally exceed the amps

Exceeding max voc tends to blow most charge controllers , i do understand some have safety measures to disconnect the panels in the event of over voltage i think victron does this not sure if others do the same

On a pwm the pwm controller just connects the panels to the batteries in pulses

If you exceed the amps i think on a pwm controller it may blow the controller too especially with lithium batteries as they can chomp amps

As far as i understand Lead acid has its limits in accepting amps limitless quantity so you may be lucky not to blow a controller in a lead acid scenario

With mppt the amps gets converted and the mppt acts like a buck converter and may limit the current design dependant

I know just enough to be dangerous ie don't know to much about circuit design to tell someone to risk 20k equipment for a saving of 30c per shedding

If the design has current limiting yes it will work

Some batteries have current limiting ie if exceeding the amp pull of the bms it can direct flow over a current limiting circuit
And thus supply only a constant 10A for example

So what might work for one person because he happened to have devices that have current limiting design may cause device loss for another because they don't

Found an example on another forum where someone blew his fronius due to over current , but when current limiting it works

So since in this case the guy has a risk free option with little cost in overhear i would rather play safe go that route

 

[Bundu]

@Bundu plus the losses mentioned is standby losses (which can be avoided by just switching the device off /unplug once fully charged lithium doesn't need to be floated to stay full, sure the voltage will settle making some think it has lost charge which isn't the case), inverting losses still has to be calculated though but most likely they will be same ball park

yes, I've decided to keep the trolley as a backup for the portable UPS.
When the portable is discharged, I'll use the trolley AC output as backup, or use the AC output to charge the portable UPS.
The trolley will be switched OFF when not being used

 

[Park@82]

No agree with you on most

Not sure how they will behave if you intensionally exceed the amps

Exceeding max voc tends to blow most charge controllers , i do understand some have safety measures to disconnect the panels in the event of over voltage i think victron does this not sure if others do the same

On a pwm the pwm controller just connects the panels to the batteries in pulses

If you exceed the amps i think on a pwm controller it may blow the controller too especially with lithium batteries as they can chomp amps

As far as i understand Lead acid has its limits in accepting amps limitless quantity so you may be lucky not to blow a controller in a lead acid scenario

With mppt the amps gets converted and the mppt acts like a buck converter and may limit the current design dependant

I know just enough to be dangerous ie don't know to much about circuit design to tell someone to risk 20k equipment for a saving of 30c per shedding

If the design has current limiting yes it will work

Some batteries have current limiting ie if exceeding the amp pull of the bms it can direct flow over a current limiting circuit
And thus supply only a constant 10A for example

So what might work for one person because he happened to have devices that have current limiting design may cause device loss for another because they don't

Found an example on another forum where someone blew his fronius due to over current , but when current limiting it works

So since in this case the guy has a risk free option with little cost in overhear i would rather play safe go that route

I'm sure that Ecoflow has a MPPT controller, I'm note sure if the Geewiz has.
I would be willing to risk trying a 24V LFP battery on my River but I don't currently have one.

I read that post on the other forum but what exactly happened it isn't clear to me. He connected a battery to a Micro-inverter https://powerupco.com/site/wp-content/files/Inverters/Enphase/Enphase M215 Manual.pdf which I know nothing about. Maybe the microinverter pulled more current than the battery could supply.

One good idea from that forum may be to wire a fuse in so that it will blow the fuse if it tries to exceed a certain current.

 

[leon.davibe]

I'm sure that Ecoflow has a MPPT controller, I'm note sure if the Geewiz has.
I would be willing to risk trying a 24V LFP battery on my River but I don't currently have one.

I read that post on the other forum but what exactly happened it isn't clear to me. He connected a battery to a Micro-inverter https://powerupco.com/site/wp-content/files/Inverters/Enphase/Enphase M215 Manual.pdf which I know nothing about. Maybe the microinverter pulled more current than the battery could supply.

One good idea from that forum may be to wire a fuse in so that it will blow the fuse if it tries to exceed a certain current.

Agree with the fuse idea

The micro inverters tend to be low ie few hundred watt items

And probably has no current limiting circuitry as a panel has a current limit so no need to limit the current that has a natural limit