Dougiedanger

Done

Good afternoon Vaughan, Compliments of the season to you too. I have a similar setup to you in terms of size and age. My Must 3kva, 24v inverter is hooked up to 4 x 205ah SLA Trojan batteries. These were my second set of batteries, my first set (2 Chinese 280ah) although first use when installed had stood for a few years without any care so didn't last long coupled with my poor understanding at the time of how to use and care for LAs. I went the Trojan route as at the time I couldn't find a decent 24v lithium option and decided to get decent lead acids as a compromise. I installed them with an HA02 balancer and I also purchased a Victron BMV712 which I used as a warning a cut off to ensure the batteries don't discharge more than 40%. I have also taken to adjusting the bulk charge and float voltages twice a year to deal with the temperature fluctuations based on the data sheet for my particular batteries. It was interesting that when I installed the BMV I found a 0.7v difference between what the inverter was reading the battery voltage at and what the BMV saw, the BMV was accurate the inverter was not, so I used that info to adjust the charge parameters accordingly so I got voltages at the terminals in line with the battery data sheet. This set of batteries are coming up on 3 and a half years old now with no significant loss in performance, although they are Trojans and should mange that easily. The next 3 years will tell me if what I have been doing is of use or just a waste of time! Lastly it does take a long time for the batteries to get fully charged, from say 70% SOC it takes probably 5 hours to get to where they are not accepting any further charge.

Love my sonoffs!

I have a set of Trojan AGM batteries that are coming up on 2 years old, I have a HA02 balancer and a bmv on them and am pretty happy with them. Unfortunately I only came across this forum after I had already purchased a 24v inverter and when the first 2 batteries that I got failed(Due to my inexperience), I looked long and hard for an affordable 24v lithium battery before deciding to stick with AGMs and purchase decent ones. My theory was I should get 5 years from them to cover the extra cost, although Zims loadshedding is making them work quite hard these days.

Not sure who has come across this on Supersport? Second round on today and is a very interesting format with some big racing names involved. A electric racing SUV with a difference, amazing how they throw them around and how they perform. The have a 40kw usable battery developed by Williams Advanced Systems. Just thought this would be of interest for some forum members!

Hi @JpPaulKrugerI have a Must which is very similar to what you have and also experienced the same sort of issues. I have set mine up on either SBU or SOL they both seem the same and don't seem to do anything different. I choose to not charge from the Grid and have set my Go to Grid setting to swap to utility when my batteries are at about a 75% SOC. By setting the Go back to battery(Or something like that) setting to a higher voltage, say 28V(on my 24v inverter) this prevents the inverter cycling if the voltage raises slightly after the load is taken off. Not sure if this would work for you however if you can get ICC I think that would be a win, just wish they could get my inverter on their list!

Hi, what sort of load are you drawing on the inverter, ie how many Watts? Do you have panels attached to this setup? How old are the batteries? Unfortunately in my limited experience it is usually a sign of the batteries being on their way out.

If the inverter is set to use Solar when available, it will use solar supplemented by battery power when the solar yield does not meet the demand requirements. That means if it becomes fully overcast the battery will provide most of the demand until it reaches the preset low voltage back to grid value. Yes it should be on the data sheet

Think you would need to be cautious with this from solely a battery point of view. Assuming that is a Pylontech it is recommended to only discharge them at 0.5c, even at 1C you can only draw 2400w max, so if you are distracted when one of those bigger ones is on and it clouds over you would be pushing the battery close to its maximum rated discharge.

Sorry @nelian, I unfortunately learnt the expensive way that lead acids are not properly protected by the average inverter which uses battery voltage to guess at the SOC which is never accurate. Due to also purchasing a 24V inverter (killed my first set of lead acids inside a year, due to similar reasons) and finding that 24V lithium batteries were not readily available to replace them with, I had to stay on the lead acid path so opted for Trojans that have a good track record on handling some abuse and coupled that with a battery balancer and bmv to protect them. So far happy with my decision but had I been on this forum longer when I made the call, I may have thought more about dumping the 24V inverter and upgrading to a 48v one so I can could then explore getting a lithium battery instead of staying with the lead acids which need more attention.

True

@Achmatand myself commenting at the same time, basically your inverter size will tell us how your batteries are setup, either 24v or 48v. That will give you the size of the battery bank, which is basically the same in watts, either 24v x 400ah bank or 48V x 200ah, ie 9600w. As stated never take the batteries below 50% SOC so useable capacity is 4800w, or 10.5 hours at a 450w draw. However note that the lifespan of these batteries will be severely compromised by drawing to this level regularly. Also the inverter will not be able to determine SOC accurately and so it is highly recommended to have BMV to do this and to be honest a battery balancer. The inverter may well run these batteries to a lower SOC than 50% which will cause more or less permanent damage if done several times.

You won't have 800ah, in series add voltage ie 12v x 4 = 48v (if your inverter is a 48v model), then ah stays the same at 200ah.

Please confirm, you say a 5Kva system, is that a 24V system? That would be quite unusual... Just reading into saying you have 4 batteries in total and 2 were purchased bout 6 months ago. I have a similar system but on a 3kva, 24V inverter with 4 x 205ah batteries. That gives me a bank of 410ah. I also draw about the same watts as you at night and my setup will give me 12 hours at that sort of draw to a 50% SOC. I did this last night for the first time due to an unexpected fault. Normally I tend to draw about 30% out of my batteries on a daily basis just to get round poor incoming voltage from Zesa in the early evening. As you will see elsewhere in this forum, you can kill lead acids very quickly by drawing them down too deeply(like I did last night).

It can't hurt. I am in Zimbabwe and have learnt a great deal from this forum which has assisted me and where and when I can help others ask the right questions. It seems that this industry is a great opportunity for average electricians to make a quick buck by selling and installing a system that works ok initially and fails within a very short time but by then they are long gone or by then can hide behind a multitude of reasons that are blamed on the customer. I am not an installer but have enjoyed my solar journey as most have here and am always looking towards what I can do to improve my system, but it does irritate me to see people being advised and sold systems that are so clearly not sized or configured correctly for their requirements.

Hi, have found this data sheet on the web. This suggests that your batteries should be set up very similar to mine, with the exception of the max charging current which is set at 30a. What settings are you currently on for 11, 17 and 18? Is the temperature there more or less 25C where they are installed and do your independent voltmeters differ to the Must screen battery voltage? vision 100ah.pdf

Good afternoon @Dollos1 I will post them below, however you will need to set up your own charging settings as per the data sheet for your batteries 5 - BLU 14. - USE 17. - 28.4 18. - 26.4 19. - 22.8 20. - 24.4 21. - 25.3 Please bear in mind my settings are for Trojan Sagm 205ah batteries and are compensated for the inverter voltage error as well as temperature. My inverter and battery location is generally warmer than 25C. What batteries do you have as set up needs to be specific for their requirements?

Our situation here in Zim every evening at peak demand in the evening, power all the way down to 165v due to us being on an overloaded transformer. Saying that my Must inverter seems to handle it fine in 3 years of use, passes through the low voltage so appliances take stress, however I have no doubt that it is not good for it

Good Morning @Dollos1 This forum has helped me a great deal, a wonderful community to be part of. Coulomb might be able to add more here but basically when the voltage is above the preset value in setting [20]the inverter will disconnect from the grid and use solar and or battery to power the loads. When the voltage drops below that set point it will reconnect to the utility supply if it is available and power loads from that. The batteries will then recharge depending on what you have selected in setting [10], ie either by solar[OSO] the next day or grid immediately [SNU or CSO]. Setting [21] then tells the inverter to go back to using the battery or solar when the battery voltage exceeds this value. I have a couple of personal reasons for this. I had purchased a set of Trojans after I killed my first set of batteries due to my lack of knowledge, Trojans are quite good batteries but expensive, however they have quite a good lifespan according to the data sheet so I have opted to use them relatively gently in order to recover so of their expense through saved power costs. I also have extremely poor low voltage power supply in the evenings from the utility so my using the inverter I keep my power voltage constant and protect my other appliances. My 'sweet spot' is the amount I draw out can be replaced by solar only the next day to get the batteries back to full, without having to use Utility power to achieve that. It also means that I leave about 80ah of emergency capacity to draw down in the case of an unexpected Utility power loss, which wont take my batteries below the 50% SOC threshold (Setting 19 is configured to cut off at this point as well as my BMV) Firstly how do the independent voltmeters compare to the inverter display voltage? I would definitely get a BMV as well as a battery balancer. For me that was sound advice that i got from this forum. Lead acids are very sensitive to abuse and the Must inverter does little to prevent that abuse from happening. The BMV is far more accurate on monitoring the SOC and preventing you over discharging your batteries and the battery balancer will keep each battery balanced which prolongs their lifespan. My first set of batteries barely lasted a year due to my inexperience and not having the setups on the inverter correctly configured. Yes I use the SOL option generally however I do not use the CSO setting as what happens is at night when it reconnects back to the grid, it immediately charges from the grid and therefore defeats me trying to save power use from the grid, so I keep it set on OSO and I have to be aware that when I leave the house in the morning if the weather is looking overcast then I need to reconfigure the inverter to recharge from grid. Not an ideal system but am working with the limited options the Must gives us. Hope this helps...

Good morning Dollos, I have the same inverter and have spent a fair amount of time setting it up to run as best as possible. It will not do the Solar, Mains , Battery configuration that you are requesting, however as Coulomb has pointed out you can configure the back to grid voltage in order to minimize the use of the batteries once solar is no longer available. When power is stable and the chance of faults is low I have set up my batteries to cycle to about 70% SOC daily and to recharge on solar only the next day which I have found is the sweet spot for my setup. I should note that my inverter has about a 0.4v difference between the inverter display and the BMV that I have connected, however 2 other 5kva Must inverters that I have seen are accurate on their voltage reading. That means with mine and possibly yours the setup of the various battery parameters needs to take this variance into account to get it to work with some predictability. Hope you get it set up to a way that works for you, shout if you need anything specific.

This is typical of poor quality equipment from China. I had the dubious honor of overseeing the installation of several Chinese made manufacturing plants in Zimbabwe 3 years ago. In each case Chinese techs were contracted from the supplying company to install these plants and get them to operating condition. In every instance the most requested tools were angle grinders and hammers from the techs to put these plants together and get them working. No manuals were supplied and when we pushed to get bearing numbers, motor details etc in order to purchase spares to put on the shelf the manufacturer asked me to get the number off the machine itself in order to supply. It appears that it is quite common for lower end products to be manufactured with whatever bearings, motors or in your case belts are available at the time of order. I wouldn't be surprised if you get another one exactly the same that several components would be different. Does the SA presence have any details that are actually in SA or not?

A friend of mine asked me to have a look at his system as to why the batteries were not lasting. He has a Must 5kva, 48v inverter, 1800w of panels wired 3s4p and 8 x 100amp Forbatt gel batteries. The system is just over a year old. I said upfront knowing what l have read and learnt on this forum that his batteries had probably been trashed by over depleting them. Anyway had a look today and found several settings that I felt were off... Bulk charge set at 55.7v, data sheet suggests each battery should be 14.4 to 14.7 Float was at 54v, data sheet 13.4 to 13.7 His low voltage cut off was set at 44v. He also had a Bmv 700 connected with capacity at 240ah, charged voltage at 52.8v and tail current at 4%. All these settings above I feel have messed his batteries up but just wanted confirmation. I have corrected the settings in line with the data sheet and my experience with my own bank and as 3 of the batteries were showing only 10.5v under load I have reduced his bank to 4 batteries from the 8. The batteries now are only taking a charge of around 1 amp measured on the Bmv and my test meter. Is this expected? Are they all history or can I do anything to get some additional life out of them whilst they look at a plan to replace them?

Exactly the sort of thing that interests me, unfortunately I have a Must, let me know when you want to trial them! Good luck, hope it goes well

Hi MongooseMan, apologies for poaching on your thread, I had a question on the GX's for Plonkster. Plonkster, thanks for all the advice on here it is most appreciated. Could you clarify for me, I have seen on the Victron site that they say the Venus Wifi and I think BT connectivity is not very good and the Cerbo is much better? I am planning to slowly move into the blue route but my install is located in outbuildings, how bad is the Venus wifi ability as to purchase an extra dongle or run a LAN cable might outweigh spending the extra R500 or so on the Cerbo?

Hi Spike, is this still available?