DIY LiFeP04 UPS - worth it or not?

[derMaaster]

I have several Mecer ME 2000VU UPS's and obviously their lead acid batteries did not last. We naively bought LiFeP04 batteries to replace them (12.8v 7Ah FreedomWon)

But that does not work and is not stable - I am not expert but the charge voltage and full charge and minimum voltage obviously is wrong.

I have looked at trying to change those levels, also with the networkupstools.org open source software, but alas to no avail.

I now have 6 of those batteries and I am wondering if anyone has built their own UPS with such batteries?
Is it worth the cost and effort?

Regards,

 

[DIYrich]

The 7ah batteries max discharge rate is 90w, well below the 2000va/1200w of the UPS. Best you can get from wiring all 6 batteries together (1s6p or 2s3p) is 540w. Not even close to making one 1200w ups.

You need 100ah of battery per ups.

If all the computers are in one area, you can build a 5kW system to power them all for about $3,000, including battery, and get almost 1 hour run time. Generating a signal to shutdown the computers is tricky. You can use the two wire generator control wire to ????

 

[wpns]

Commercial LFP UPS boxes aren't really a thing (see other threads on this subject, LFP output power, float issues, etc), but you can certainly build an UPS yourself, though not cheaply, and then you still have float-charging issues.

 

[BarracudaBob]

I have been pondering this idea for a long time. My internet & network equipment on a UPS so I can monitor alarms, cameras, and solar system. In the event something goes wrong with the solar I don't want to loose my network.

I have plenty of inverters and commercial UPS's made for SLA and I can turn off the charging ckt. How do you connect LPF with a trickle charger or float charger.

Like many other solar addicts I have an abundance of LPF batteries to use.

 

[Wibla]

I've seriously considered a Victron MultiPlus 12/800/35 (the compact one) instead of trying to retrofit an old UPS for LFP.

 

[BarracudaBob]

I've seriously considered a Victron MultiPlus 12/800/35 (the compact one) instead of trying to retrofit an old UPS for LFP.

I have commercial 19" rack inverters with built in fast transfer switching. I also have a spare EG4 3K I could use but this is also in the "TV Room" so fan noise would be an issue.

Considering taking one of my Victron charge controllers and feeding DC into it. Maybe put it on a timer so most of the time it is off.

Cost is a factor and I have a bunch of parts and equipment I would like to use.

 

[Wibla]

IIRC Victron recommends against using MPPT as a DC-DC charger, but it will work. If you have a 48V lifepo4 battery and a 12/24V UPS setup, that should work just fine. Not sure you'd have to put it on a timer either.

 

[BarracudaBob]

IIRC Victron recommends against using MPPT as a DC-DC charger

I didn't know that. I haven't tried it yet. I didn't think it was a good idea to float LPF over long times but if it was at a reduced level it may be ok.

 

[hardtop]

The DIY route I went with is a UPS. All my gear pulls from an inverter from the battery and then a 2nd Anderson connector allows a charger to re-supply power to the battery in parallel. Its pretty sweet so when I do backups, if I'm not sure if there is enough battery then I just plug in the charger. If I forget about the generator and it dies (no gas/oil), all my gear stays up.

 

[mbesto]

I have a ~180w worth of homelab equipment running on a battery and inverter:

- 800w Ampinvt Inverter/charger with https://a.co/d/duuqbFu - $155 (less than 10ms transfer time)
- 100ah Seikon battery - https://a.co/d/jfqVmwb $145
- Cabling ~$100
$400 total, 1200 Wh gives me ~6hrs of backup

Alternatively:
EcoFlow DELTA 3 for $649 for 1024 Wh

EcoFlow DELTA 3 Plus Portable Power Station | EcoFlow US

Get next-level battery safety & performance with X-Core 3.0 Technology. Fast-Charge using Solar, Grid, 800W Alternator Charger, Inverter Generators.

us.ecoflow.com

 

[BarracudaBob]

I have a ~180w worth of homelab equipment running on a battery and inverter:

- 800w Ampinvt Inverter/charger with https://a.co/d/duuqbFu - $155 (less than 10ms transfer time)
- 100ah Seikon battery - https://a.co/d/jfqVmwb $145
- Cabling ~$100
$400 total, 1200 Wh gives me ~6hrs of backup

Alternatively:
EcoFlow DELTA 3 for $649 for 1024 Wh

EcoFlow DELTA 3 Plus Portable Power Station | EcoFlow US

Get next-level battery safety & performance with X-Core 3.0 Technology. Fast-Charge using Solar, Grid, 800W Alternator Charger, Inverter Generators.

us.ecoflow.com

800w Ampinvt is a nice little unit. The wife would plug a coffee maker or something into it. I would need to run at least 1500W out of it as most kitchen appliances pull that much.

Perhaps this could do it

 

[Jmhai3]

This is mostly what my system was made for.
UPS function and backup that currently can last for up to 12-24 hours depending on load.
Wired to different rooms in the house powering TV's, refrigerator, computer/Wi-Fi, and CPAP day and night.
EG4-3k with two EW server rack batteries.

It has been going for two years now with just a once-a-week cycle to exercise the batteries and covering the random power outages we get sometimes and over two weeks straight after hurricane Helene came thru.

Going to buy a timer for the system so I can cycle it more often. Not sure if daily or not is recommended to mimic solar but will see what info I can find when that time comes.

This was also a way to learn so can incorporate in another property in the future for use with solar.