Jump to content

Batteries for Mecer 5KVA inverter


optics
 Share

Recommended Posts

I am new on the forum and new in this field. Please have mercy on a retired person.

I need help with a system that my son uses at home. It is a Mecer 5KVA inverter that he uses as a backup for load shedding. It is connected to the utility supply and takes over automatically. When in use it is supplied by four 200A/h gel batteries. No solar panels involved. The system is in use for two years now and the batteries has packed up. I suspect that the batteries discharged to low. When the system is in use, it supplies a fridge, freezer, two fans, three 40" TV's, modem, 2x decoders and PS4 with monitor for about 4.5 hours when the batteries were still fine. During load shedding all these appliances runs full time. Load shedding does not last 4.5 hours anymore but only 2.5 hours in general.

He wants to replace this batteries now with a 3.5KW/u Lithium ion battery. First I want to know if this battery will be compatible with the inverter. Secondly, how does this battery compares with the 200A/h gel battery. (How many hours will it be able to supply and how many years will the battery last in comparison in general.) Thirdly are there any settings that we should take note off for this inverter that should be specific for this battery. He is currently looking at a Pylontech battery.

I've read some stuff about this on the forum but to me as an old mechanical noob it doesn't make sense at all and I would appreciate any understandable advice from our learned friends on the forum.

Thanks very much for your time in advance.

 

 

Link to comment
Share on other sites

Hi optics

It would help to know the average power drawn by all the loads - this is the best way to know how many kWh have to be supplied by the battery for the time required...

For instance, if the average draw is 2kW, and loadshedding is active for 2.5hrs, you would need 5kWh from the battery, which would need a 6.25kWh battery at least, assuming you use 80% of its capacity.

The LA batteries he had were 9.6kWh in total, but you can only safely use 40% (3.9kWh) of their capacity without them degrading fast...

One issue he might face regarding Li battery size: they can only supply a set maximum current, for several reasons. If he uses the full 5kW of inverter capacity, the battery will need to supply ~110A. This might not be doable with a single unit. He might need 2 or 3 in parallel.

It would make a lot of sense to quantify the power draw before proceeding, as it will determine the batteries needed.

Cheers

Ian

Link to comment
Share on other sites

@Ian Thanks very much for the reply. I assume it makes sense to get the load first. I will get them to tally the amount of W usage at a time. This is all Greek to me. I will come back with more information.

Yes it is a 48V system.

Link to comment
Share on other sites

@Ian our calculation for the appliances excluding the fridge and the freezer, comes to 916W. The fridge and freezer will be excluded from the backup system in future.

From what I understand is that this 1Kw can be easily manage by the 5Kv inverter as it doesn't use the full capacity of 5Kw from the inverter. None of the appliances have a huge startup requirement. From what I can make out from your calculation is that if the load shedding last for two hours we will need a 2Kw supply. If it last for 2.5 hours then we need 2.5Kw supply.

With 3.5Kw lithium battery and a useful capacity (80%) of 2.8Kw it seems that it might make it for two and a half hours. Please correct me if I do not understand this.

You also brings 110A into the argument that only complicate things for me. :)

Will the battery be compatible with the 5Kv inverter. keeping in mind it doesn't use the full capacity of the inverter. It doesn't matter if it will not last for the two hours.

If yes, are there any specific settings in the inverter required for the setup.

Thanks again for your time.

 

Link to comment
Share on other sites

Hi Optic

The current issue is a tricky one - best to check the specs of the battery that he's looking at, or supply the model number here. I know some manufacturers are sticky re warrantees if the inverter can overtax the battery, but hopefully there are other members here that can add more info. If the battery disconnects internally if overloaded then it should put that to bed at least.  The inverter might also be able to be set to limit battery draw. but that's also something for the members here with experience to answer. 

Regards, Ian

Link to comment
Share on other sites

13 hours ago, optics said:

First I want to know if this battery will be compatible with the inverter.

Yes

13 hours ago, optics said:

how many years will the battery last in comparison in general

10yrs warranty

13 hours ago, optics said:

Thirdly are there any settings that we should take note off for this inverter that should be specific for this battery

image.png.6433ee473f2d99bc64125bcd1decf3dd.png

 

5 hours ago, optics said:

With 3.5Kw lithium battery and a useful capacity (80%) of 2.8Kw it seems that it might make it for two and a half hours. Please correct me if I do not understand this

Correct 

FYI Lithium batteries need to used daily irrespective of loadshedding or not (if memory serves me correct by 20%) if not used warranty will be come void

IMO 2 x US3000C Modules would be safer as to not void warranty on battery and I would leave the fridge/freezer, inverter serves as protection from surge as well

I would get pi with ICC and pylontech BMS cable (https://iccsoftware.co.za) to manage SOC of battery correctly

Link to comment
Share on other sites

12 hours ago, Ian said:

Hi Optic

The current issue is a tricky one - best to check the specs of the battery that he's looking at, or supply the model number here. I know some manufacturers are sticky re warrantees if the inverter can overtax the battery, but hopefully there are other members here that can add more info. If the battery disconnects internally if overloaded then it should put that to bed at least.  The inverter might also be able to be set to limit battery draw. but that's also something for the members here with experience to answer. 

Regards, Ian

Hi Ian

Do you mean overcharging by the inverter or overload by the load drawn from the battery.

Thanks for the rest of your reply.

Link to comment
Share on other sites

9 hours ago, Quwatush Shams (Suly) said:

Yes

10yrs warranty

image.png.6433ee473f2d99bc64125bcd1decf3dd.png

 

Correct 

FYI Lithium batteries need to used daily irrespective of loadshedding or not (if memory serves me correct by 20%) if not used warranty will be come void

IMO 2 x US3000C Modules would be safer as to not void warranty on battery and I would leave the fridge/freezer, inverter serves as protection from surge as well

I would get pi with ICC and pylontech BMS cable (https://iccsoftware.co.za) to manage SOC of battery correctly

Hi Quwatush Shams

Thanks for the advised settings. This is precisely what I need as this is not my field.

Program 29 setting of 46.5/46 is that the voltage where the inverter will switch off or wants to go back to utility? What % DOD will that gives me?

From what I understand from your post is that Lithium batteries needs to be used daily. This system will only be used for backup in times of load shedding. Other times, load will be supplied from utility via inverter. In this case the batteries will not be used at all. Does he have to switch off the inverter everyday and let it drain the battery by about 20%. Do I understand this correct?

Do you suggest that we leave the fridge and freezer part of the system? But then the load might go higher than the 1Kw. Can I assume that the load might then not hold for two and a half hours. He does plan to get another module in the future.

I will certainly look into the ICC option. Currently he is using Watchpower to check the system but I am not sure what ICC can or cant do?

Thanks for everyone's patience with me.

Regards

Link to comment
Share on other sites

2 hours ago, optics said:

Program 29 setting of 46.5/46 is that the voltage where the inverter will switch off or wants to go back to utility?

Switches off

2 hours ago, optics said:

What % DOD will that gives me?

Don't know

 

2 hours ago, optics said:

Does he have to switch off the inverter everyday and let it drain the battery by about 20%. Do I understand this correct?

Yes.Thats why I suggested ICC so that you can automate the process (setup once and than it does it by itself there after)

 

2 hours ago, optics said:

Do you suggest that we leave the fridge and freezer part of the system? But then the load might go higher than the 1Kw. Can I assume that the load might then not hold for two and a half hours. He does plan to get another module in the future.

Yes and he needs to start with 2 Modules

 

2 hours ago, optics said:

Currently he is using Watchpower to check the system but I am not sure what ICC can or cant do?

Automate change from utils to battery and back to utils

2021-01-28.thumb.png.03dadc4158af97505182f1264786df95.png

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...