Hi All

Hoping someone can assist, at my mothers house, which is off grid (No Eskom power allowed) had to install a new inverter as the old one burnt out (Gecko in inverter fan caused it to burn out). The electrician installed a new Sunsynk 5kw hybrid inverter a few days ago. With the new inverter she installed 8 x 535 (Haitai HTM 535 ~ 555 M115 - 72 Panel) solar panels as her old panels where out of spec for the new inverter apparently.

She is using the same AGM battery bank that was originally in place, however the electrician had to change the wiring so that the batteries where 48V.

She has 24 x 2 volt 900ah batteries in place in series i believe giving 48 Volts. What should the charge/discharge settings be on the Sunsynk inverter to ensure full charge is achieved , what other settings can i check to ensure the system is operating optimally? Reason i ask is that the system was re-commissioned 3 days ago and each night she runs out of power?

The settings are most probably correct and i have nothing bad to say about the electrician however for peace of mind id thought i would ask on the forum to ensure all is ok with her setup as she cant afford to replace batteries at this stage so want to ensure all settings are correct and cause no damage and are working optimally.

Ive attached some readings off the inverter from yesterday 5pm. as well as pic of the battery bank.

Any help will be greatly appreciated. 

59 minutes ago, SheldonB said:

same AGM battery bank that was originally in place

Are you sure its AGM and not plain flooded cells? Best would be to get specifications from the cell manufacturer, since these also have a variable, based on temperature...

Looking at flooded cell data from this location, a fully charged flooded cell battery consisting of 24 cells should sit at 2.11V * 24, so 50.64V for 100% SOC, however, there is always a temperature co-efficient one also has to take into account with these types of cells... and the AGM cells would have a slightly higher Voltage, 2.15V * 24, so 50.6V for 100% SOC, which still does not tie in with your 87% SOC and 50.76V, but then I have not taken into account the 25degC temperature.

Either way, I would try and get cell data from the actual manufacturer of the cells, confirm what they are exactly and base the inverter settings on those...

You don't say how old these are, also note, if one cell is iffy, then the battery will not perform well, ideally one should verify every cell's internal resistance and ability to take and supply energy...

Thanks Kalahari Meerkat for the feedback, really appreciate it.  Too be honest batteries could be flooded cells ?? We fill them with battery water, so im assuming they would then be flooded cells? The number on the batteries is ST MIL25 FG, (They are 2 Volt 900ah apparently)and they are 2 years old. The previous installer that we got them from unfortunately passed away so i cant ask him, ive searched everywhere on the net and can't find any details on this battery.

Thank you for that link you sent much appreciated and of great help. If i assume they are indeed normal flooded cells then fully charged as you say should be 2.11Vx 24 = 50.64Volts, ive attached a picture from earlier today where at 99% SOC its sitting at 50.79V, which is close to the 50.64V according to that website you sent , further more earlier this morning at 74%SOC it was sitting at 49.73V, once again pretty close to what the website sais (2.05Vx 24 = 49.2V for 70% charge).

I called someone at First National battery and hopefully they can provide the specs of the batteries or point me in the right direction as too who made them? Will update spec sheet if i manage to get it. 

Just want to ensure the charging voltage etc and maximum discharge voltage (Low Battery Cutoff ) etc is setup correctly on the inverter.

Sorry another question the house is completely off grid as i mentioned earlier, and my mother does not have a generator so why does the one screen indicate that Generator use has been 12.7 hours?

@SheldonB,

Could be that the installed configured the Aux port as GEN Input, with Timer Mode On (check is GEN Charge is ticked), and when the batteries go below the set limit (seeing your off grid), it will provide the Gen charge signal, even though you don't have a Genny connected.

As you don't have a Genny and are Off-grid, then Timers seem pretty pointless, as you only have PV as an alternative source. 

If the above isn't the case, then the hopefully someone else here can shed some light on it.

 

PS. I intrigued by your system reporting that the Battery Temperature is 25 Deg. How does the inverter know this? In my mind you/installer should have installed a battery temp sensor on no. 1  & 2 of the pin connector, as per Installation manual. As mentioned above by others, temps on Flooded Bats do play a roll, and hopefully the Sunsynk control software compensates for this when you run a Voltage based setup like yours.

PPS. I would like to believe that after 2 years, those flooded cells should still be OK. They are known to last very long, provided they are looked after. I'm sure you know the drill..... Measure each cells SG with a hydrometer and record in a logbook (monthly). If you don't have a SG meter, at least measure the voltage of each cell during charging and discharging cycle, so that you can pick up if a cell is going bad. If you do find one one day, and can't find a replacement, just run you "pack" as 23 cells, and adjust your voltage settings x 23, instead of x24

Edited June 3, 20242 yr by Sidewinder

Also, I couldn't help but notice the following in the battery photo:

1) Between the first set of 6 cells, and the 2nd set of 6 cells, the link cable seems to be of a much smaller gauge that the inter cell links.

2) Same with the top left last cell, the wire (that goes to the inverter) also looks smaller. Can't see the opposite end of the battery pack (photos is cut off).

You should aim to have the same gauge wire throughout you installation. The thicker, the better - less voltage drop.

 

19 hours ago, SheldonB said:

Sorry another question the house is completely off grid as i mentioned earlier, and my mother does not have a generator so why does the one screen indicate that Generator use has been 12.7 hours?

Like @Sidewinder wrote, you probably have the GEN input configured and the inverter has been signalling a non-existant generator...

One more thing, though, please tell me that the inverter is in another room away from those 2V cells, since they *will* gas some during charging and the gas is as corrosive as it gets...

Hi Sidewinder thanks for the input, ive asked the electrician to double check whether the Aux port is set as Gen input (I believe it mustve been as he said he'd fix it), i have no idea how the inverter knows batt temp im assuming its a default value? I have asked Electrician is he installed a temp sensor and if not if he can add. We do check the batteries all the time and top up as required! the last set lasted 12 years believe it or not they where also 2 volt batteries (Willards). With regards to the wire gauge all wires are the same gauge (Picture angle makes the gauge look smaller).

for the past 3 days the system has been working well and the batteries Voltage and SOC % seems to line up with the chart on the website that Kalahari Meerkat sent (Thanks again).  Unfortunately the inverter is in the same room (No other option), the room is well ventilated and although not ideal its all we have to work with.

Thanks for the input guys has been really helpful ,