Small inverter / UPS backfeed to input?

lightpixel said:
I will need to look at the wiring. I will check my other model also.
Click to expand...
So when the incoming mains cord is unplugged, you are getting 8V DC backfeeding from 12VDC batteries back down the incoming 230VAC power supply cord?
 
Optimistically said:
Hello - is it normal for the input power cord (the cable from the 230VAC mains) to a small inverter / UPS to remain live after you unplug it (or after the grid drops)? In other words, for the inverter to backfeed 230VAC to its power supply cord in addition to its output outlet? If so, does it only do so temporarily or whenever the inverter is delivering 230VAC?
Click to expand...
how big are the ups units .pic
 
Optimistically said:

GeeWiz 2400VA (1440W) Inverter Battery Charger (UPS) - Intelligent Fan (Modified Sine Wave) 3 Stage Charger - GeeWiz

GeeWiz 2400VA (1440W) Inverter Battery Charger (UPS) - Intelligent Fan (Modified Sine Wave) 3 Stage Charger for sale online at the Best Prices! Door to Door and Overnight Delivery
www.geewiz.co.za www.geewiz.co.za
Click to expand...
a bit of bleed back on a big unit is probably normal ,diodes can allow 7 volts back easy ,but there will probably be no current on it so it will just pull dead if you stick it in your eyeball .edit out of curiosity put a small globe on it ,like a park light 5 w globe and see what it does ,if it stays lit then it may become a hazard
 
Last edited:
Optimistically said:
Agree - seems a no-brainer. But was wondering if the BMS built into the BlueNova batteries might do it automatically? More than R15k these days to replace two Li batteries…sadly…!

Will try to ask BlueNova for their advice also…
Click to expand...
The bms in the batteries only balance the cells in that battery ie the 4 cells that make it a 12v battery

I would not leave a permanently on balancer on a lifep04 battery

The balancer can't damage the batteries per se if permanently on it can however move power around in the flat portion of the graph incorrectly

You can use a balancer like this from time to time to get them in balance when batteries are over 13.8v each

Edit: keep at high voltage switch balancer on once balanced switch it of

Or buy the victron balancer that does this

That is where you balance lifep04 when cells are over 3.45v per cell anywhere else in the voltage range you are fooling yourself
 
Last edited:
soulie said:
a bit of bleed back on a big unit is probably normal ,diodes can allow 7 volts back easy ,but there will probably be no current on it so it will just pull dead if you stick it in your eyeball .edit out of curiosity put a small globe on it ,like a park light 5 w globe and see what it does ,if it stays lit then it may become a hazard
Click to expand...
It did give me a bit of a zap when I touched the plug inadvertently…
 
Optimistically said:
It did give me a bit of a zap when I touched the plug inadvertently…
Click to expand...
its not ideal and should be mentioned to the distributor ,the back feed could become more than expected and should have a circuit to prevent it ie a resistor to bleed it off , i wouldnt be comfortable with that , without a valid reason why , and a plan to rectify it .you may also have an internal insulation resistance thats failing and could cause the whole item to become live .
 
It now becomes a necessity problem , send it back and sit without for 3 months or buy a loose socket outlet for R100 and plug it into that when unplugged and keeping an eye on it .I think you should also measure from the plugs earth to live and neutral and see what you get .you may have stumbled onto the reason why so many earth leakages trip when power is restored .
 
leon.davibe said:
The bms in the batteries only balance the cells in that battery ie the 4 cells that make it a 12v battery

I would not leave a permanently on balancer on a lifep04 battery

The balancer can't damage the batteries per se if permanently on it can however move power around in the flat portion of the graph incorrectly

You can use a balancer like this from time to time to get them in balance when batteries are over 13.8v each

Edit: keep at high voltage switch balancer on once balanced switch it of

Or buy the victron balancer that does this

That is where you balance lifep04 when cells are over 3.45v per cell anywhere else in the voltage range you are fooling yourself
Click to expand...
Thanks - I thought the point of a balancer between two 12/13V units in series making up a 24/26V system was that it needed to be kept in place permanently to balance the voltages?
 
It is not backfeeding anything. The shock you get from touching the terminals of the plug is just the energy that is still in the capacitors and transistors that is being released when your hand provides it with a completed circuit to escape.
 
Optimistically said:
Hello - is it normal for the input power cord (the cable from the 230VAC mains) to a small inverter / UPS to remain live after you unplug it (or after the grid drops)? In other words, for the inverter to backfeed 230VAC to its power supply cord in addition to its output outlet? If so, does it only do so temporarily or whenever the inverter is delivering 230VAC?
Click to expand...
It happens, I was once zapped by the plug, it's usually temporary though.
 
Optimistically said:
Thanks - I thought the point of a balancer between two 12/13V units in series making up a 24/26V system was that it needed to be kept in place permanently to balance the voltages?
Click to expand...
Yes, this is true, the balancer must always be connected, the point leon was making is that with the flat curve of LFP, there is no point in balancing below the peak (13.6V), so the cheaper balancers that are "always on" actually put the batteries out of balance when they are balancing below 13.6V. I don't think its a big deal, as there are plenty of these balancers out in the field and they do the job, it just might be more practical to go for the victron one that only balances above a certain voltage.
 
Optimistically said:
Thanks - I thought the point of a balancer between two 12/13V units in series making up a 24/26V system was that it needed to be kept in place permanently to balance the voltages?
Click to expand...
Lifep04 batteries top balanced actually stay in balance for a few months quite easily
Edit or even way way longer if you happen to have batteries with similar internal resistances

And only needs to be balanced from time to time to address any drift

As wingnut says most likely the balancer wont make to much of a difference

if the batteries are charged full regularly ie every time it is fully charged it will pull them back in balance easily

For People however using the notion of 20-80% as many believe

I would not leave it on, but use it maybe once every 2-3 months and do full charge to check balancing
 
Last edited:
You must log in or register to reply here.
Back
Top
Sign up to the MyBroadband newsletter
X