Jump to content

Recommended Posts

Hi Guys, 

 

I am new to this forum, mainly registered since reading a bit and want do download the axpert manual,but need atleast 5posts. So let me introduce myself. 

I am a qualified Millwright,working on Dragline control systems for a big company, been in the industry for 5 years and programming PLCs the past 2 years. Learning a lot about power factor etc. 

I recently decided to buy a small system due to load shedding we will soon start to experience. Recieved it this week and will start to install on sunday. 

It consists of:

Axpert 5000mks

2x 260w JA solar panels

4 x 105ah 12v batteries

 

also requested a quote on another 4 batteries and 2 panels to expand a bit

 

Any installation tips,calculations etc you guys can assist me with? Whats it good for and what not. At first I wanted to use it on all plugs and lights with the utility bypass function. But after reading a bit it seems it wastes more power when bypassing

 

current daily usage of about 40kw per day. Between 5-7 people in the household. Big swimming pool. And electric geyser. 

Share this post


Link to post
Share on other sites

The main aim will be to reduce electric bill a bit and also have a battery backup to operate my tellies and computers and fridges. 3 tellies,2 computers(max 300w each) and 3 fridges

Share this post


Link to post
Share on other sites
9 hours ago, Anarchy05 said:

current daily usage of about 40kw per day

If at all possible, spend some money to get this down. This is where I started too. I almost halved it and now, with the water restrictions where I live and significantly reduced hot-water usage, I'm at less than half that, averaging around 18kwh a day now.

Look at those three fridges as a start. Those things can use deceptively large amounts of energy. If they are anything like mine, you'll find they use up to 3kwh each per day. I replaced both of mine with energy efficient models that cut the consumption into a third.

9 hours ago, Anarchy05 said:

The main aim will be to reduce electric bill a bit

Don't want to throw too much water on the fire, but I learned some unsettling things over the years. I found out, for example, that my small 200ah bank (at 24 volt) can suck up a good 1kwh a day just for float-charging. In other words, with only 500Wp on the roof (as you state), and a similar capacity (48V@100ah), you may find that of the 2.5kwh you make you lose almost half on float charging. What little energy remains, I would use to run my freezer and fridge during daylight hours. At night, stay on the grid.

I started with just 300W on the roof, upgraded it to 450, then 900, then 1500, and last week to 1800. I now make 10kwh a day, which is about a third of my consumption.

Share this post


Link to post
Share on other sites
23 hours ago, Anarchy05 said:

2x 260w JA solar panels

4 x 105ah 12v batteries

I would recommend a minimum of 1 panel per battery for a reasonable balance to the system, so get 2 more panels before you add battery capacity - and then add panel capacity at the same time as batteries if you want to expand your system further. Your current system will use all available PV energy to charge your batteries with no capacity available to run your loads during the day.

Get an HA-02 battery balancer (read up on the forum and then approach ChrisR) - you wont notice the difference if you have one, but you will notice if you dont!

The Axpert inverter together with the Victron BMV-702 and controlled by ICC works beautifully, without the BMV and ICC the Axpert will attempt to control Grid_Mode/Battery_Mode switching using battery voltage which is dodgy to say the least.

Share this post


Link to post
Share on other sites

Hi Plonkster. Thanks for the reply. I already have energy effecient fridges. My whole house idles around 500w when the geyser is not running and the pool pump. I am not too sure but I think in my power usage the biggest culprits are washing machines, the big 200L geyser , and the swimming pool pump. 

 

I already bought a contactor etc to wire the geyser onto a smart timer. That will be my first attempt at reducing cost. And my poolpump already only runs 2.5hrs a day. 

 

Share this post


Link to post
Share on other sites
5 minutes ago, pilotfish said:

I would recommend a minimum of 1 panel per battery for a reasonable balance to the system, so get 2 more panels before you add battery capacity - and then add panel capacity at the same time as batteries if you want to expand your system further. Your current system will use all available PV energy to charge your batteries with no capacity available to run your loads during the day.

Get an HA-02 battery balancer (read up on the forum and then approach ChrisR) - you wont notice the difference if you have one, but you will notice if you dont!

The Axpert inverter together with the Victron BMV-702 and controlled by ICC works beautifully, without the BMV and ICC the Axpert will attempt to control Grid_Mode/Battery_Mode switching using battery voltage which is dodgy to say the least.

Will read up a bit on that thank you, so when adding an extra 2 panels provide a bit of extra solar that will not be used for charging, thus can be used to pull loads?

Share this post


Link to post
Share on other sites

A 105Ah battery will store, 105x12 = 1.26kWh of energy, if you are discharging to the recommended 50% SOC then you will have used 0.6kWh which must be replaced. If you are replacing battery energy with grid power then in my view you may as well not have the PV system, so if you set the Axpert to charge batteries using Solar Only you will require 0.6kWh of PV capacity per battery - plus any additional energy required to run your selected loads.

1 x 260w panel will produce about 1kWh per day (we all wish and dream for more, but sadly it just doesn't happen very often) - so one panel for 2 batteries would barely be able to recharge batteries from 50% SOC with no additional capacity available. One panel per battery would give you somewhere around 0.5kWh spare capacity to run loads during the day.

You could have more panels than batteries (of the type that you are using) and that would be great, but not more batteries than panels.

Note that the above is an opinion - others may differ.

Share this post


Link to post
Share on other sites
8 minutes ago, pilotfish said:

A 105Ah battery will store, 105x12 = 1.26kWh of energy, if you are discharging to the recommended 50% SOC then you will have used 0.6kWh which must be replaced. If you are replacing battery energy with grid power then in my view you may as well not have the PV system, so if you set the Axpert to charge batteries using Solar Only you will require 0.6kWh of PV capacity per battery - plus any additional energy required to run your selected loads.

1 x 260w panel will produce about 1kWh per day (we all wish and dream for more, but sadly it just doesn't happen very often) - so one panel for 2 batteries would barely be able to recharge batteries from 50% SOC with no additional capacity available. One panel per battery would give you somewhere around 0.5kWh spare capacity to run loads during the day.

You could have more panels than batteries (of the type that you are using) and that would be great, but not more batteries than panels.

Note that the above is an opinion - others may differ.

Thanks for the great explanation, I was under the impression I would yield more from a panel than that, good thing I stumbled upon this forum during my quest for knowledge!

The batteries I mainly want as a backup and to supply when the load is slightly more than that the panels can supply. But since the yield is so little I think I should rather look at getting more panels instead of the 2 and more batteries. To have excess during the day which can be consumed on loads. 

I have read up on the HA02,it seems it balances the charge between batteries on the bank. Any idea on pricing from ChrisR?

Also the Victron BMV is very pricy but seems to be usefull. Any idea on a well proced supplier for that? I had a look at sustainables site

 

thank you

Share this post


Link to post
Share on other sites
2 hours ago, Anarchy05 said:

Can I mix panels or would it be better to stay with the same panels?

I would suggest that you stick to very similar panels - 260w panel is probably 32v peak whereas 300w panel is probably 36v peak, your MPPT tracker will go a bit cross-eyed trying to optimize power from a mixed bag like that.

 

Share this post


Link to post
Share on other sites
8 hours ago, pilotfish said:

not more batteries than panels

I agree. Well, again there might be cases where having more battery is warranted, but then you'd be charging using the grid too, after an outage.

A conceivable use case for more battery is where you have long outages. In these cases, when the grid returns, you will bulk-charge the batteries (ie up to absorption voltage) using the grid, and conceivably even after that, up to around 85% SoC. At that point you'll stop charging with the grid and let the PV panels do the rest. The motivation behind this is that the inefficient last 15% is then done using the cheapest energy (the PV panels). The system is designed not to save money, but to provide backup. During "normal" operations you'll run only a few small loads to utilise the PV power, after the batteries are full.

For self-consumption cases -- where you want to use most of your energy yourself -- I agree with @pilotfish, you want more panels and less battery.

Share this post


Link to post
Share on other sites
8 hours ago, Anarchy05 said:

Can I mix panels or would it be better to stay with the same panels?

It depends how you'll be connecting them. If you're going to put them all in series, then preferably the same panel, or within 10%. If you're going to add them in parallel, then you want the Vmp (on the back of the panel, the voltage at which it makes Max Power) to be closely matched. Also keep in mind that there is a maximum input voltage on the MPPT (145V I think?) and the Voc (Voltage Open Circuit, also on the back of the panel) needs to add up to no more than this. For the Axpert, that usually means 3 panels in series, because the 260W panels are likely 60-cell modules, so their Voc is around 32V, and three of those puts you around 100V.

300W panels are usually 72-cell modules, make up to 48V open circuit... and... well you probably don't want to mix 60-cell and 72-cell modules in parallel or in series.

If they are on a separate MPPT, well then the only limit is not to go over the max charge current for the battery, which in your case would be 20 ampere (100Ah, at C5, is around 20 amps... preferably slightly less, 15 amps is better).

Edit: Come to think of it, two 60-cell modules in series puts you at around 60V normal operation. Now as I recall the Axpert MPPT wants about 5V or so above the peak battery voltage, which really means 60V is on the low side. So my advice would be to either use two 72-cell modules, or 3 60-cell modules for a start.

Share this post


Link to post
Share on other sites

Now I am totally baffled. Lol

this is a lot to take in. Well the main reason I got this is the area I stay in will start to get loadshedding in early november, so the 4 batteries would be for the basic lights and tv during that time of +-4 hours each evening. I then started reading up and thinking I might aswell spend a bit more to reduce ny electric bill. Thinking maybe to run my pool pump for short whiles off the system or so during the day as the batteries would only be for backup. I have since then learnt that my panels would be insufficient for that purpose. And also that I would need a battery equalizer and the BMV702 as the axpert struggles with the switchover. I will now be looking at getting some more panels and the abovenentioned equalizer and bmv as a start to my small system. Still need to construct everything anyways. So might aswell do it right from the start. 

Any suggestions as to what else would be needed? My pump is 1.1kw running 4hrs a day currently on eskom

Share this post


Link to post
Share on other sites
45 minutes ago, Anarchy05 said:

he 4 batteries would be for the basic lights and tv during that time of +-4 hours each evening.

You said your load is around 500w. For 4 hours, so that's 2kwh. The batteries therefore needs a minimum storage of double that, that is 4kwh. Your 4 x 100ah batteries gives you 100 * 48 = 4.8kwh. So on the face of it, it looks okay.

Now things get a little more tricky. There is this thing called he Peukert effect, which basically says the battery "shrinks" if you work it too hard. Technically this is not true, it's a bit like myself doing athletics at school. I'd do 5km with no problems, if you let me go slow, but force me to go twice as fast and I'm paste by 800 meters. Technically the inherent energy in my body has remained the same, but I'm just not built to run fast. Now batteries are rated at their C20 (ie when discharged over 20 hours) rate. At 500W you're discharging them at more than double that rate, so you're not going to get the full 100Ah out of them. I'd therefore say you want to drop your load to around 350W or so, if you can, during load shedding.

Now you need to get that energy back into the batteries the next day. Keep in mind that the round trip efficiency is around 70%, so you need to put back around 2.8kwh. Assuming the standard 5 hours of equivalent peak sunshine, you need 2800/5 = 560W worth of PV. Lets say 600W.

If you want to run the pool pump for 4 hours, you need another 1.1*4 = 4.4kwh, add 10%, that's a cool 5kwh. You'll need at least another 1000W or so (in my experience) to make that. So you're looking at at least 6 of those 260W panels.

Now the voltage matter I also brought up. The PV voltage needs to be higher than the highest battery voltage. Those batteries charge up to almost 59V during absorption (look at your specific battery's spec sheet for details), and you ideally want the lowest PV voltage to be about 5V above that. Keep in mind that on cloudy days or days with thin cloud, the voltage where it makes the peak power drops. If you have only two panels in series, you may sometimes only have 60V peak to work with. So I think two panels aren't enough in ANY case. You therefore need at least three of them (or panels with a higher output voltage). And if you ask anyone here who knows the Axies well, they really work best with three in series. And since I already said you need 6 panels to do this, that will leave you with a cool two strings of three panels each (2x3 arrangement) which should work perfectly wired to the existing MPPT controller inside the inverter.

@Chris Hobson, that about right?

Share this post


Link to post
Share on other sites
9 hours ago, plonkster said:

You said your load is around 500w. For 4 hours, so that's 2kwh. The batteries therefore needs a minimum storage of double that, that is 4kwh. Your 4 x 100ah batteries gives you 100 * 48 = 4.8kwh. So on the face of it, it looks okay.

Now things get a little more tricky. There is this thing called he Peukert effect, which basically says the battery "shrinks" if you work it too hard. Technically this is not true, it's a bit like myself doing athletics at school. I'd do 5km with no problems, if you let me go slow, but force me to go twice as fast and I'm paste by 800 meters. Technically the inherent energy in my body has remained the same, but I'm just not built to run fast. Now batteries are rated at their C20 (ie when discharged over 20 hours) rate. At 500W you're discharging them at more than double that rate, so you're not going to get the full 100Ah out of them. I'd therefore say you want to drop your load to around 350W or so, if you can, during load shedding.

Now you need to get that energy back into the batteries the next day. Keep in mind that the round trip efficiency is around 70%, so you need to put back around 2.8kwh. Assuming the standard 5 hours of equivalent peak sunshine, you need 2800/5 = 560W worth of PV. Lets say 600W.

If you want to run the pool pump for 4 hours, you need another 1.1*4 = 4.4kwh, add 10%, that's a cool 5kwh. You'll need at least another 1000W or so (in my experience) to make that. So you're looking at at least 6 of those 260W panels.

Now the voltage matter I also brought up. The PV voltage needs to be higher than the highest battery voltage. Those batteries charge up to almost 59V during absorption (look at your specific battery's spec sheet for details), and you ideally want the lowest PV voltage to be about 5V above that. Keep in mind that on cloudy days or days with thin cloud, the voltage where it makes the peak power drops. If you have only two panels in series, you may sometimes only have 60V peak to work with. So I think two panels aren't enough in ANY case. You therefore need at least three of them (or panels with a higher output voltage). And if you ask anyone here who knows the Axies well, they really work best with three in series. And since I already said you need 6 panels to do this, that will leave you with a cool two strings of three panels each (2x3 arrangement) which should work perfectly wired to the existing MPPT controller inside the inverter.

@Chris Hobson, that about right?

Now that was a good explanation!

so I would be looking at adding 4 more panels,voltage equalizer and also BMV702. 

Is the BMV necesary if I am only going to use batteries during loadshedding times? Not enabling to switch between ac and battery?

Basically if it is to be used completely off grid

Share this post


Link to post
Share on other sites
10 hours ago, plonkster said:

Chris Hobson, that about right?

Jip I'm  happy with your take on the Axpert. Three 60 cell panels in series or two 72 cell panels in series. I know several folk have three 72 cell panels in series but that is just too risky for my conservative approach.

58 minutes ago, Anarchy05 said:

Is the BMV necesary if I am only going to use batteries during loadshedding times? Not enabling to switch between ac and battery?

Basically if it is to be used completely off grid

You are going to use your batteries a bit anyway when your consumption is more than what your panels are producing. If your batteries are going to only be for backup then I would not get a BMV yet but I would make sure I have one of @Chris-R's HA-02s as my feeling that they are essential. 

11 minutes ago, Anarchy05 said:

According to what I have read just now in the Axpert manual I would still need the BMV it seems otherwise it seems the axpert is not to smart on the battery SOC

Yes  but if you not really cycling your batteries a BMV become a bit of an overkill.

Share this post


Link to post
Share on other sites

Thank you very much to all for the assistance, 

I am not too clued up on the install, would ask if somebody has extra time if they could provide me with a drawing of what a proper install would look like as I still need to get some extra stuff. Not sure what I need. The install will be

4x 105ah batteries in series for 48v

4kw inverter

6 x JA 260w panels 2 strings of 3x panels(in series + to - I would guess?)

and then I am not too sure as to should I fit some fuses and an extra db etc?

Thanks again

Share this post


Link to post
Share on other sites
5 hours ago, Anarchy05 said:

I am not too clued up on the install, would ask if somebody has extra time if they could provide me with a drawing of what a proper install would look like as I still need to get some extra stuff. Not sure what I need.

I think a good start would be to inform others where are you based, or have I missed that here?

Share this post


Link to post
Share on other sites
49 minutes ago, Riaanh said:

I think a good start would be to inform others where are you based, or have I missed that here?

Oh sorry, didnt think that will make a very big impact. I am based in Witbank MP, one of THOSE municipalities that reach the news very often regarding owing Eskom a bunch,think its a few billion,apparently if we dont pay 4mil each day we are going to have loadshedding starting early nov,from 6am to 10am mornings and 4pm-8pm evenings. 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×