Repurpose old UPS as Inverter

[ljwobker]

I was thinking about the -3000 as I think I have a line on an old chassis without SLA's in it already. I thought I read that you couldn't just drop in LiFePo's without the charging logic from the UPS screwing things up. Is that not the case? If it's truly drop in, I might just rig up a 2p string to get the runtime I need...

 

[OffGridInTheCity]

I was thinking about the -3000 as I think I have a line on an old chassis without SLA's in it already. I thought I read that you couldn't just drop in LiFePo's without the charging logic from the UPS screwing things up. Is that not the case? If it's truly drop in, I might just rig up a 2p string to get the runtime I need...

My APC UPSs all charge to 27.6v (+/- just a bit) per 24v 'battery'. This is both the APC 1500 and the 3000s.
If you do the lifepo4 voltage math: 3.45v per lifepo4-cell * 4 cells = 13.8v per battery * 2 batteries = 27.6v. This is perfectly matched voltage wise.
Charge wise: APCs have gentle charging as in 2-3a (50-75w) on APC 1500 - e.g. 25-38w per 12v battery - which is very gentle and again I don't see a problem.

 

[SamDeleted]

I've just been converting a 5000va ACP UPS for use as an inverter, got it very cheap. It's 48vdc input


Seems to be going great

 

[Vigo]

Post a thread on that sometime!

(mine is still sitting unused)

 

[A.Justice]

I've just been converting a 5000va ACP UPS for use as an inverter, got it very cheap. It's 48vdc input


Seems to be going great

I'd love pics and details!

 

[Delmar]

I don’t know how I missed this UPS porn thread. I have been messing with APC UPSverters and have learned a few expensive things:
* Many consumer grade UPSs are modified sine. You have to research the model number to determine. Many will have a distortion warning molded into the case.
* The UPSs are sensitive to elevated battery voltage, like charging from solar with minimal loading.
* Most of the small UPSs are designed to overheat soon after the internal battery dies. For temperature protection some will shutdown on time & loading, and ignore the available battery voltage.
* Good APC UPSs are low-frequency and great for starting motors. To get the equivalent LF inverter would require 10x the cost. However the downside are the UPSverters are not very efficient, especially at low loading. And loud with multiple fans that run regardless of loading, and big LF transformers emitting a 60hz hum.

To ensure you are getting a pure sine UPS that is rated for continuous operation, I look for APC “XL” models. They are easy to spot in auction pictures by the rear external battery connector. Below are pics of my 24V 1000XL running my moms TV, and my 3000XL powered by my 48V golf cart and back-feeds my breaker panel during grid down. The HF unit on the far right ignored the extended battery and shutdown on time & loading.

 

[Vigo]

That is good info!!

 

[SilverbackMP]

I’m going the other way…have a couple of older Trace and Outback inverters that I’m going to repurpose as UPSs. Primaryl so I can take down the main system (off grid) for unscheduled maintenance.

 

[SamDeleted]

I'd love pics and details!

5000va 48vdc APC UPS used as inverter

I've been playing with this 5000va 48v APC UPS (sua5000rmi5u) I got it at a great price , it was the biggest I could find in 48v I'm converting it to use as an inverter in my off grid solar system, https://www.apc.com/uk/en/product/SUA5000RMI5U/apc-smartups-5000va-230v-rackmount-tower/ See...

diysolarforum.com

I did post a thread but it got lost in the mist

 

[ko6kL]

I hadn't even thought of this, but I , too, have a couple of battery dead APC1500 UPS.... now you have me thinking...

Older APC ups's work pretty well as cheap short term AC, need to find one that can be started with out the AC cord plugged into the wall... the older ones mostly..., you can also grab a nice network and phone line protector from the parts inside.