Saturday at home, installing an inverter

[tec0]

I know in older homes if you turn something on like a kettle the lights would "dim" for a second and go normal again. Could it be that turning on the kettle creates a dip in the power flow for a second that causes the beep?

[Justloadit]

You may have a UPS inverter, in other words the load is always supplied by the inverter, and the battery is always on charge/stand by, so effectively the load can then not exceed the UPS rating at any time.

[blackknight72]

You may have a UPS inverter, in other words the load is always supplied by the inverter, and the battery is always on charge/stand by, so effectively the load can then not exceed the UPS rating at any time.

It is an Axpert 3KW MKS plus.

Interesting enough the Inverter doesn't bleep when i use the same kettle in other power points.

[blackknight72]

Interesting enough the Inverter doesn't bleep when i use the same kettle in other power points.

[AndyD]

I'm not sure why that would be.

Did you sort out the problem with the inverter error code indicating overvoltage on the batteries? What was the cause out of interest?

[blackknight72]

I'm not sure why that would be.

Did you sort out the problem with the inverter error code indicating overvoltage on the batteries? What was the cause out of interest?

Yes, it was sorted out after a lot of confusion and unnecessary tension. The inverter was found to be faulty and was replaced with a new one. Afterwards a faulty kettle triggered alarm for overloading. Just finished with the installation this week but we haven't had any load shedding after that. I shall post some pics soon. Many thanks for sharing your experience in tge forum which led me to experiment with the current setup, much against the opinion of local gurus!

[malcolmpearson]

Hi guys

I have been following this thread with great interest, thanks mostly to AndyD...

I am installing one of this RCT 5000, so far the install is:

RCT 5000W Axpert Hybrid Inverter
8 Royal 100Ah Deep Cycle batteries - could not get the 200Ah
Cables to connect the batteries to each other and Inverter - rather more expensive than I thought (R700 with fuse)
100Amp DC fuse for the battery bank

Nothing installed yet, but here is my idea:

The batteries connected with 2 parallel connected sets of 4 in series (basically 12Vx4=48V and then in parallel to the other 4x12V=48V giving me 48V at 200Ah)

Now my question is now the solar panels:
I am looking at the ArtSolar Pinetown Durban produced 250W panels at around R2100 excluding VAT vs the SolarWorlds 260W at R2800 ex VAT. It would be great to hear if somebody is using this locally produced solar panel and how it performs.

The RCT spec on the Solar Panels is as follows:
SOLAR CHARGER
Maximum PV Array Power 3000W
MPPT Range @ Operating
Voltage 60VDC ~ 115VDC
Maximum PV Array Open
Circuit Voltage 145 VDC
Maximum Charging Current 60A
98%
Standby Power Consumption 2 W

My understanding is that I can connect 8 x 250W solar panels to this hybrid = 2040W to be within the 3000W range?

The specs for the solar panels are:
ELECTRICAL DATA @ STC 250Wp
Peak Power Watts - PMAX (Wp) 250Wp
Power Output Tolerance - PMAX (%) 0/+3
Maximum Power Voltage - Vmmp (V) 30.3V
Maximum Power Current - Impp (A) 8.27A
Open Circuit Voltage - VOC (V) 37.6V
Short Circuit Current - ISC (A) 8.85A
Reverse Current - IR (A) 18A

Do I need to concern myself with the open circuit limit or the maximum power current? Are the 8 panels going to exceed the limitations of the hybrid inverter/charger?

[AndyD]

Yes the string voltage will be critical to the performance of the system, it's something you should be concerned about. I don't have the specs of your inverter to hand, does it have a built-in MPPT tracker? If you're not sure I'll see if I've got time tomorrow to find a spec sheet.

[malcolmpearson]

Thanks Andy

Here are the specs as per link - we have the 5KVA - I could not get this PDF to paste properly....here is the link sorry!

http://shop63.co.za/image/data/Documents/RCT-Axpert%20MKS-A4.pdf

[malcolmpearson]

My calculations up to now think I could do 3 parallel connected strings of 3 of the 250W PV panels (9 in total) - that would keep me below the open voltage and below the max amperage and max voltage?

[malcolmpearson]

A question:
I have used a 100amp fuse on each bank of 4 x 100Ah batteries - is this an overkill?

And I see the manual mentions that you should have a manual switch for the batteries from the inverter - is this necessary?

[blackknight72]

Hello Andy,

Last year during the peak of power outage, upon inspired by your thread I installed an Inverter. The input from that thread and the forum members were of great help in this matter. Now I am back with another scenario. I am probably one of those many unfortunate people who installed the inverter and discovered that there is no long shedding. Here in East London we haven't had any outages for the last 8 months or so and I assume that is the same in most towns. My inverter didn't have to kick in even for an hour since installation! Now I am worried that the batteries might get damaged if I do not take them through a discharging process. Hence I switch of the mains once a week to facilitate discharge. Considering that potentially there will be no challenges in the power sector for a while at least I would like to look at a more practical solution to the current situation.

I have two options. I can sell them off. The total investment was around 25 grands. If I am lucky to find a buyer I may retain 50 percent. The other option would be to attach PV panels. My unit is Axpert 3KV MKS plus. The question is will it be a worthy exercise to invest more around this. I have no idea how much expensive it is to install panels. While I am not sure how many of you are caught in the same situation like me,If you or anyone else has insight into this please share with me.

[AndyD]

I think a lot of people are in the same boat where they spent a fair amount of money on back-up solutions only to find they got limited use out of them and I do feel sorry for those who waited a long time before jumping on the bandwagon only to find the load-shedding stopped shortly afterwards. Your particular case is the worst possible scenario and you never even benefited from the outlay and installation. Nearly all of the inverters we've installed have been for commercial clients and mostly with the disruptions to trading they were suffering they'd paid for themselves after the first few episodes of load shedding. I guess you've got to look at it like car or house insurance where it's peace of mind whilst you have it and if you don't claim during the 12 month policy term you wouldn't start regretting the outlay and wishing you'd never bothered.

I have a homemade mains fail counter on mine that records the number of power fails and the total duration of running on battery back-up and since it was installed there have been 88 instances of power fail and the total back-up time is 149.7 hours. A few of these power fails were when we had an earth leakage tripping issue and once every 2 or 3 months I manually trip the power and load test the system so at a guess about 60-70 of them maybe would have been due to Eskom. I used a lot of second hand materials and installed it myself, its capital outlay to me was around R14K so every power outage that I've had back-up power for has cost around R215.00 or R93.00 per hour. Also not cheap but having a home office, if I had to make the same decision today with 20/20 hindsight I'd still have gone ahead with the install.

I use a 5Amp Optimate charger to condition the batteries. Every 6 months I've been removing the batteries, topping them up where necessary, checking the specific gravity of the electrolyte and putting them through a 'conditioning cycle' whereby the Optimate discharges them and recharges them and supposedly 'desulphates' them. Has it worked?..... I don't know TBH.

We recently had a planned power outage for 12 hours whilst local Eskom/Council supply transformers were replaced/upgraded and the inverter ran for about 8.5 hours before shutting down on low battery voltage. During this time all my 2x computers, 2x routers, 2x servers, TV, laptop, printers, phones and various small chargers etc were all running, the espresso machine was used 3 or 4 times being unplugged in between each use and there were 12v LED lights which are direct off the same batteries running throughout the house. This was by far the longest power fail we've encountered and the system performed beyond my expectations and far beyond its design duration so maybe the conditioning charge is working.

I'm going to keep my back-up system, it's resale value isn't sufficient to warrant ripping it out and being without it. That said I'm not going to invest any further money in PV panels etc because there won't be sufficient operational benefit or return on the capital outlay. I can't really advise on what you should do, I'm not even sure how much inverters and batteries are selling for second hand. Part of the 25K you paid was for the installation so really you need to remove that amount from the equation before working out what percentage you'll recover you you sell. I don't see any reason you shouldn't get at least 50% of the new price for your inverter but second hand batteries are a lot more risky and I'm not sure many people will be happy to take that higher risk unless the price was low enough to warrant it.

[SilverNodashi]

I would also keep the system, if you can afford it. Loadshedding isn't over. No until we get new power plants with proper maintenance contracts and electricity prices become more affordable for the masses again. Partial reason for load shedding in many smaller towns are often the fault of overloading a transformer / sub station due to stolen electricity. Just yesterday, the power was off in Witbank, from 9am to 4PM for maintenance. This is probably fine on a Sunday, but imagine it was in the week. Many businesses would have lost R25k right there.

Depending on what batteries you have, you could get away with cycling them every couple months only. Get the datasheet off the internet and see how many months it can be stored without a charge. Then discharge and recharge it, say 2 weeks before that period. The fewer times you discharge the batteries, the longer they will last.

[bergie]

i would keep the system and go the solar panel route. your 3 kva axpert has a built in solar charger. i am doing the same with my 5 kva axpert. i plan to run my pool pump,lights and other light duty appliances in the daytime. i will use the batteries for a short while at night,with a high cut off voltage. with eskom prices going up and up ,it will pay itself off quickly.