UPS Conversion

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Tristao

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Can a Mecer 10000VA ON-LINE UPS be converted to LiFe batteries?
 
Lifepo4 batteries have a voltage that is similar curve as lead acid that is where the drop in replacement comes from

I assume 1000va and that the 10k is a typo

With the extra capacity it will naturally take double as long to charge full

And with extra runtime it will overheat. Can add a fan to keep things cooler

And naturally try and keep the load as low as possible

These items would not run for long before the lead acid was flat

So heat soak wasn't really a problem , but adding extra capacity makes it a problem

Had a lifepo4 on a pc ups as my first backup plan just for tv/media pc

It popped the first day i tan it without the fan (forgot to switch it on)
 
leon.davibe said:
Lifepo4 batteries have a voltage that is similar curve as lead acid that is where the drop in replacement comes from

I assume 1000va and that the 10k is a typo

With the extra capacity it will naturally take double as long to charge full

And with extra runtime it will overheat. Can add a fan to keep things cooler

And naturally try and keep the load as low as possible

These items would not run for long before the lead acid was flat

So heat soak wasn't really a problem , but adding extra capacity makes it a problem

Had a lifepo4 on a pc ups as my first backup plan just for tv/media pc

It popped the first day i tan it without the fan (forgot to switch it on)
Click to expand...
The 10kVA is not a typo. It is a UPS with 16x12V 7Ah batteries (192V)
 
Tristao said:
The 10kVA is not a typo. It is a UPS with 16x12V 7Ah batteries (192V)
Click to expand...

often the small batteries are paired with cheap bms that often can't be run in series (remember seeing some listings that state that)

Another edit
running 12v lifepo4 in series will land you on the wrong nominal voltage ie if running 16x 12v lifepo4 in series you land at 204.8v have to change the config to 15 batteries to land at the same 192v as 15 x 4s would land you on perfect 60s x (3.2v nominal per cell)

so if you get a battery that is fine with series connection the balancers will be pricey
you will need 5x 48v balancers (need to overlap them) , or forego the balancers for cost and then manually intervene if needed , not easy if the batteries are in a tray where you can't access them, so a shutdown needed

or go diy battery and buy 60cells with 3x 20s bms's ie build 3x 64v batteries
capacity you need ?

edit
oh and forgot load plays into it too small battery has 7a bms so can only use 1.3kw before it trips a battery
so would need a pack with a beefy bms and high drain cells if not going for 10kwh capacity 55ah cells that would deliver the 52a needed ie just under 1c

you would need a 52a bms to use the 10kw
so yea diy battery is only option if going lifepo4

Buying 16x 50Ah @3.5k means R56k for 9.6kwh plus the need for 4.5k of balancers

Buying 60 x R500 55ah cells plus 3x 20S bms's R36k for 10.56kwh

Balancing is the tricky part as i don't know if any balancer exists for balancing. 3x 64v batteries

having 6 wires rooted outside to ad resistance to draw down if any pack is higher than the others is a cheap option

Going for voltage to find balancers easier ads extra bms cost , finding most economical balance while being happy with drawbacks
 
Last edited:
Another option is getting 4x 48v 4.8kw 15s batteries not 51.2v which is 16S

Pylontech / shoto also has some 15S packs
That has a nominal voltage of 48v, others do too

4 of those in series would yield the 192v

67k ouch

But yea googling isn't easy as many 51.2v packs are advertised as 48v packs so googling for 48v gives you tons of 51.2v packs

This one states 48v 15S tend to be 4.8kwh (100ah)/2.4kwh(50ah) while the 51.2v packs tend to be 5.12kwh(100ah)/2.56kwh(50ah)

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Tobo 48v 4.8kWh Lithium ion Battery LifeP04 Battery Pack | bobshop.co.za

Buy Tobo 48v 4.8kWh Lithium ion Battery LifeP04 Battery Pack for R16,800.00
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Hi Tristao, I will buy that UPS for R4k if not too far away. I am in Centurion. If you can get more, grab it...
Application is for a backup to a backup to a backup power to my house. (No typo.. ;-)
Those high-voltage UPS's cannot be economically maintained but I build lithium-ion 18650 battery packs running off native PV solar volts without BMS or charge controller and use them as backup. (I don my BMS hat once in awhile and weed out bad cells, but am retired and see it as a hobby)
 
Hello Travis, yes and no. Eaton PX9 still backing up my backup to Eksdom, but not for the novice.
No problem with the 1802 x 18650 cell powerwall, which is remarkably stable. The bloody Eaton takes some fiddling to come online sometimes. Unhappy with some internal PCB power supply, display absent or erratic. Have to rely on muscle memory to cancel error.
Someone on a forum grabbed a 10 kW 210 VDC UPS given away before I could dibs, wonder if that is even in use now?
If you are not scared of a spanner or high voltage DC, I can help.
Many techies are falsely afraid of high V DC, forgetting their high school knowledge, "if you do not complete the circuit, it can not shock"
 
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Thanks for coming back on this. It looks like if i stick with the lead acid, I cannot just use one string, but need both, so 32 batteries. I cannot find online whether I can put in cheaper 12V 7.2ah batteries instead of 9ah. I just need it to deliver 1kW for 15 minutes occasionally before it's set to cut out.
 
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