Good day power forum guru's

I am in the process of trying to build a solution for our school's network mainly brought about by needing to keep the security camera system online during loadshedding.

We have 2 main network consolidations where the NVR, Server and core switches are located that will require backup power for 200 and 400 watts respectively. Then we have 2 network cabinets in storerooms with 2 switches each that we need to power, both rated at 30W so it would be 60W per cabinet. Then we have 2 8-port POE switches that are in 2 separate classrooms that provide power to some POE Security Camera's that will also need to be powered.

I am looking for something that will fit into the cabinets and still be "aesthetically pleasing" so I am not a very big fan of the Trolly backup solutions as this will likely have to sit next to these cabinets and take up more space where we are already constrained. Added to this it needs to be cost effective because of budget constraints and be something that they won't need to replace batteries, etc. in a year or 2 and ideally have a quick recharge time to get back up to power before the next outage. I am trying to spec this for the Stage 4, 5 and 6 type outages.

Any suggestions on products that out there that anyone has used for a similar scenario.

Really appreciate any input and advice.

If your requirement was for a solution that could be rack mounted then the Rack Mount Axpert King would be a good candidate. That King would need to be paired with a Lithium battery. 

Thanks for the suggestion however would a 5KVA not be overkill cost and function wise for the above loads? It just needs to fit in the cabinet and look neat and tidy. Rack mount would be a bonus but not a requirement. I can also add in additional shelves to cabinets to house the extra equipment.

24v 2.5Kwh Pylontech batteries,3kw axpert-type inverter (non-rackmount)

On 2022/11/13 at 3:05 PM, giggsie said:

Thanks for the suggestion however would a 5KVA not be overkill cost and function wise for the above loads? It just needs to fit in the cabinet and look neat and tidy. Rack mount would be a bonus but not a requirement. I can also add in additional shelves to cabinets to house the extra equipment.

Another thing to consider is the voltage of the system and the load on the battery. A 1kw load on a 24V system will pull 40A from the battery, whereas a 1kw load on a 48V system will pull 20A from the battery.

Don’t forget you need to know how much power those PoE switches are using. If you want to save some money, I would recommend buying a kill-a-watt for R400-R500 and conducting an energy audit. Figure out how much power you are actually using. For example, one of my computers has a 750W power supply, but it only uses about 250W most of the time. If I based my spec on 750W I would end up buying a battery 3x larger than I need, and the batteries tend to be the most expensive part of any such build.

 

Once you know how much concurrent power you need in watts, multiply that by the number of hours you need it for. So say it’s 1000W and you need it for 4.5hrs, that’s 4500Wh or watt hours (aka 4.5kWh). I would add a good 20-30% on top for safety and efficiency losses.

Also consider the difference between how much you’re actually using and how much you could theoretically use. Computers use way more power starting up or shutting down for instance. Your 1000W system might pull 2000-3000W at peak, so make sure to size the inverter accordingly.

I recently did the calculations for Stage 6 myself. It gets a little bit complicated if you are trying to work out the minimum requirement. If you are going off worst-case (ie a full 4.5hr outage instead of 4.1hr or whatever) and you need it to always stay on, you need to figure out the weird parts of the schedule. Particularly where one day ends and the next begins. For example, you will usually have at least 4.5hrs between outages, but every few days (where I live) we get a 4.5hr outage either 2.5hrs before or after a 2.5hr outage. So you have to figure that you either need to be able to recover for or from a 4.5hr outage within 2.5hrs.

 

One method is to get batteries that can charge that fast (honestly most rackmount batteries can do 0.5C which means that they can be charged in 2hrs with a sufficiently powerful charger/hybrid inverter) or to get enough headroom that whether you have 2.5hrs, 4.5hrs or whatever, you aren’t going to be so close to the line that you need to worry. The latter is the more expensive option clearly. Note that most rackmount batteries are 48V, I think the Pylontech UP2500 is a notable 24V exception.

 

Also note that some non-rackmount inverters frequently get placed on their back in a rackmount configuration but that isn’t really ideal as they are designed to be vertical for cooling purposes. If you are going to mount them in this configuration, make sure the room has adequate cooling.

Edited November 15, 20223 yr by Jankzilla

On 2022/11/13 at 3:05 PM, giggsie said:

Thanks for the suggestion however would a 5KVA not be overkill cost and function wise for the above loads? It just needs to fit in the cabinet and look neat and tidy. Rack mount would be a bonus but not a requirement. I can also add in additional shelves to cabinets to house the extra equipment.

The suggestion of 5kW is purely based on two important reasons. The 5kW King rack mountable solution is quality. I don't offer anything less than 5kW because quality of the inverters tend to drop in the sub 5kW range & of course 24V batteries imho also start to get into the lower quality range also. 

As explained above the amps are lower in the 48V range. 

On 2022/11/15 at 8:11 AM, jumper said:

Another thing to consider is the voltage of the system and the load on the battery. A 1kw load on a 24V system will pull 40A from the battery, whereas a 1kw load on a 48V system will pull 20A from the battery.

Great point, Had not considered that.

On 2022/11/16 at 6:15 AM, Steve87 said:

The suggestion of 5kW is purely based on two important reasons. The 5kW King rack mountable solution is quality. I don't offer anything less than 5kW because quality of the inverters tend to drop in the sub 5kW range & of course 24V batteries imho also start to get into the lower quality range also. 

As explained above the amps are lower in the 48V range. 

Thanks @Steve87, great to have experienced input on this. Will try look at the 5KVA 48V option.

So I know I have let this thread run dormant but I decided to reach out to a few people to assist on this, sadly with not much luck. Everyone seem to want to up sell solar or a managed solutions or some form of rent to own. I have met with and spoken to at least 10 different parties and only have 3 quotes none of which match the requirements I provided above anomaly focus on the primary location/Main server rack. So it would seem I am back to where I started 4 months ago.

Before starting this thread, my initial thought was to go for the RCT 3KVA inverter with 24V LFP Batteries (Any brand):
https://www.enway.co.za/Inverter/Off-grid-Inverter/Alfa-3KVA-2.4kW-Pure-Sine-Wave-Inverter-Charger-pwm?limit=100

But since I can't find data on how well this works with LFP batteries I am not willing to take the risk and experiment with money that is not mine. This was also before @Steve87 and @jumper's replies.

So after the messages here I think I will be better served by the Kodak connected to a Pylontech or Dyness 2.4 or 3.6Kw battery:
https://www.solar-shop.co.za/kodak-inverters/581-kodak-solar-off-grid-inverter-with-ups-5kw-48v-rack-mounted.html

Based on the load in the server rack at the primary location I should get a run time 6 hours and up based on a load of 400W. This will also give room to grow as I can expand on the number of batteries if required down the line.

 

For the other locations:

I conducted a test with the facilities manager using his Jackery Explorer 500. This showed that the 2nd location is actually only drawing 100W as we don't need to power the TV for the camera system after hours which will give us the 5 Hours run time and it can be charge back up to 80% capacity within an hour.
https://jackery.co.za/product/explorer-500-portable-power-station/

The down side is that it uses Lithium-ion and not LFP cells and is only rated for 500 cycles.

I then came across the Bluetti EB70 on take-a-lot and thought this would be ideal until I read the comments:
https://www.takealot.com/bluetti-portable-power-station-lifepo4-1000w-716wh-eb70/PLID92530246

Apparently the power Pack is quite noisy and since the 2nd location doubles as an office I don't want to introduce something that will result in a noise complaint. It is a pity as these make use of LFP cells and rated for 2500 cycles. I suspect it will be fine for the Store rooms where we have the AC Network Switches as I doubt the noise will be heard from the outside. So I am back to looking for a solution for the Office/2nd Rack.

 

I found out that the PoE switches for the Camera systems are 4-port and not 8-port like was originally told to me by the installer. So I am looking at these little DC UPS sold by Tech-Buddies which I came across some time back but thought would not work as based on their website they could only run the 8-Port config for approximately 2 hours.
https://tech-buddies.co.za/prestashop/home/39-power-buddie-mini-dc-ups-48v-12v-9v-75wh-poe.html

I have reached out to them to get their feedback on the feasibility of being able to run this load for 4 hours and they feel it should make it but have agreed to come to site to run a test with us like we did with the jackery to make sure it can carry it.

 

So this is where I find myself at this point intime after scouring forums, listening to different points of view and advice from anyone and everyone I can find who has knowledge on this topic.

Again, any insight and advice that can be offered by the members here would be welcomed as I would hate to put this proposal to the school and it fail and be a waste of money. 

12 hours ago, giggsie said:

So after the messages here I think I will be better served by the Kodak connected to a Pylontech or Dyness 2.4 or 3.6Kw battery:
https://www.solar-shop.co.za/kodak-inverters/581-kodak-solar-off-grid-inverter-with-ups-5kw-48v-rack-mounted.html

I think that is a good choice and will be nice and neat as they are all rack mounted. I would personally go for a rack mounted shoto battery because of the C rating (and because it's what I chose), but it is not as 'trusted' as the Pylontech or Dyness and doesn't talk directly to the inverter yet, but that doesn't bother me as much as others. My system is DIY and I don't have a COC, so warranties didn't factor too much into my decision, but it might be more important for your install at a school and as you mentioned you don't want to take a risk with other people's money.

I can't comment on the other solutions as I have no experience with them, but having a chance to test them first is great. If you need something quiet for an office then you need to look for inverters with heat sinks instead of fans, there are a few of them around.

Thanks @jumper, really value the input and guidance. A quick question on the Shoto and Kodak Coms, would using something like SolarAssist help to bridge the gap? 

25 minutes ago, giggsie said:

Thanks @jumper, really value the input and guidance. A quick question on the Shoto and Kodak Coms, would using something like SolarAssist help to bridge the gap? 

Yeah afaik it will work perfectly and also adds all the data, graphs etc. you would ever need. There seems to be some work ongoing in the king firmware for shoto support so it might come in the future. I just run my king on USE mode with voltage settings and it works perfectly. SA will help if you want to control things remotely and run certain things based on SOC.

Another Quick question on the configuration of the Kodak Inverter with Battery to build the UPS, Should this have a configuration have a fuse or any type of breaker switch between for compliance?

3 hours ago, giggsie said:

Another Quick question on the configuration of the Kodak Inverter with Battery to build the UPS, Should this have a configuration have a fuse or any type of breaker switch between for compliance?

Technically there is a fuse in the inverter (200A I think) and usually a way to turn off the battery via a button or switch, but these are expensive to replace and clunky to operate in an emergency (trust me I know), so it is best to have an external fused DC breaker. I can't comment on the compliance aspect, but for safety it is definitely better.

Last Question, is there a way to work out the heat that will be generated by the Battery and Inverter? The question came back from one of the SGB parents as this solution goes into a strong room. There is no aircon to regulate heat.