Hi All,
Is it possible to set up a ups backup power system using lithium batteries and a multi?
How do you get around cycling the battery regularly to extend the lithium battery life?
Any suggestions
asked
Victron UPS with Lithium Battery
Hi Riaan. Yes you can do that.
Just wire the multi in to the circuit(s) you want covered. It will operate in passthrough while you have grid, and of course top up the batts at the same time. When the grid fails the inverter should fire seamlessly to cover the loads from the batts.
It won't cycle the batts while the grid is up.
Hi John,
Thanks for the rapid response, I would, however, like to cycle the batteries from time-to-time to is there a setting that I could use to accomplish this?
Thanks
Riaan
Hi Riaan. Yes it is possible to do that, provided the Multi is set up correctly around your lithium battery. To enable periodic cycling, one solution that jumps to my mind is to set up ESS, set it to “optimized without battery life and set the minimum SOC to your desired level of discharge. Then, using scheduled charge to keep it charged for 6 days and a bit, and let it discharge a few hours. That way it will cycle once a week. Alternatively, just flip the AC in breaker every now and again. If you have a decent lithium with a good BMS, cycling it wont necessarily extend it’s life
Riann - maybe "cycle the batteries" the wrong word or thought here. To really "cycle the system", you would need to cut power to it and let the UPS function do it's thing (pick up the load).
I setting the multi, if you choose the LiFePO4 as the battery, look at the charging curve characteristics -- charges fast until full, drops off rapidly, then every 7 days it gives a charge spike to the batteries.
https://www.victronenergy.com/upload/documents/Manual-MultiPlus-3k-120V-(firmware-xxxx4xx)-EN.pdf Appendix E
or here - https://docs.victronenergy.com/veconfigure.html#charger-settings and the explanation below it.
And that time is selectable.
I have just finished a 25kW UPS using Plyon x2 US2000C batteries and an MP II 3000VA GX for our editing and storage servers. Pictures click for pics
I am now trying to find a way to schedule so the pylon batts don't just sit at 100% all their lives. I will reduce the max charge voltage in the DVCC setting to around 85% and give then give them a full cycle every month. (down to 30% ish I think)
I might just put a timer plug on the system and switch the power off once a week for 5 hours to get it to 50% :)
Thanks, Simon
live link here https://vrm.victronenergy.com/installation/408637/share/ba0dace3
System build pics https://photos.app.goo.gl/ueyPGggBd4Uix5jv5
Nice, doing a similar thing for telecom mast sites albeit with AGM batteries. No potential BMS glitches which can knock out the system if the battery shuts down.
To cycle the battery you could enable ESS on the Multiplus then setup a target SoC if 100% for all but a brief period every week. Question is it really necessary??
