48V - 6000w Aims inverter shuts off in the middle of the night.

[rizon]

Hello, I'm very new here. I am a master electrician by trade (solar is not my forte), and I recently purchased a customized off-grid solar "kit" online and I wanted to pick everyones brain on an issue I'm having with the 6000w Aims inverter. I will start with the system. I am running a 48V system, with 8 - 100 Ah Battle Born Lithium batteries, wired in series and parrallel. I have verified with the BB people that I have the batteries connected correctly, however that is not the issue. (see pictures for the setup) I also have a Victron - MPPT TR 150V 70A 12/24/36/48 solar charge controller, and, as mentioned already, an Aims power 6000W Pure Sine inverter charger. As far as the panels, I have (12) - 305W panels (S-energy 3m305M-10T) wired in strings of (4) ea back to a factory installed combiner box.
I am using the Victron BMV-712 battery monitor to monitor my battery voltages and battery life.

The problem: Long short of it is, I installed a manual transfer switch on the panel that feeds my inside electrical panel (lights and plugs). The batteries charge flawlessly to 100% with no problem. Like I said I'm new to this, but I set up the Victron solar charge controller and battery monitor as per the Victron online setup instructions for battle born batteries, so I am confident that this part of the system is setup correctly. I have noticed that when the battery bank is fully charged, the battery voltage is like 56.6V and as the batteries drain, that voltage begins to decrease.
My first two nights in a row, I'll go out a check the battery life with the Victron battery monitor app, after the sun goes down (around 9pm) Keep in mind, I am only running a few lights and plugs (about 1200W max) on the inverter. The battery monitor will show like 83% of battery capacity left. I may be reading the Victron monitor app wrong but it will show, at the current load, there is XX amount of battery life left. Which in my case showed about 1 day and 6 hours left, however when the battery bank voltage drops below 48V, my inverter shuts off as well as the power in my home. It seems as though I'm not maximizing the amount of time I can go without the batteries being charged. Not sure what to check or correct, or, is this about right, 4-5 hours of use @ 1200W to drain the 83% remaing battery life? This happened the first few days and nights we used the system.
My question is do they make a better inverter, or inverter/charge controll system that may prolong how long I can use the inverter power?
Questions? comments? any help will be much appriciated. I will include pictures of my setup.

 

[rmaddy]

Those 8 batteries would roughly be 10,240Wh. With a 1200W load (ignoring any inefficiencies) would give you 8.5 hours if the batteries ran from 100% to 0%. So starting at 83%, pulling 1200W for 5 hours gets you down to about 2500Wh which is about 25% SOC. Though 48V indicates closer to 10% SOC.

I don't see how the BMV is showing 30 hours remaining during a 1200W load when the most you can get is just over 8 hours.

Is the BMV setup correctly for your battery bank? What capacity did you setup using VictronConnect? You have a 48V 200Ah setup. It sounds like you may have told the BMV you have 800Ah.

 

[rizon]

Ok, I'll check the settings, I did set it at 800 Ah because each battery is 100 Ah? is that correct? Victron has a website page specifically for battle born batteries. Maybe the monitor was showing 30hrs before i connected the load? I don't remember. Wow only 8 hours, is that good or bad? As far as upgrading, what are some options that I have? Also, I noticed that when the inverter is in use with a load, the charger doesn't seem to be charging the batteries at the same time?

 

[Bob B]

Ok, I'll check the settings, I did set it at 800 Ah because each battery is 100 Ah? is that correct? Victron has a website page specifically for battle born batteries. Maybe the monitor was showing 30hrs before i connected the load? I don't remember. Wow only 8 hours, is that good or bad? As far as upgrading, what are some options that I have? Also, I noticed that when the inverter is in use with a load, the charger doesn't seem to be charging the batteries at the same time?

Batteries in series increase the voltage but the AH remains the same ..... so ... 4 100 batteries in series = 48V at 100 AH.

In parallel, the voltage remains the same but the AH doubles .... so ..... 2 48V 100 AH in parallel = 48V 200 AH.

 

[Bud Martin]

4 100Ah batteries connected in series will give 100Ah capacity, so two 100Ah battery strings in parallel = 200Ah capacity.

 

[rmaddy]

Maybe the monitor was showing 30hrs before i connected the load?

It's showing 30 hours under load because you told the BMV you have 800Ah instead of the actual 200Ah capacity.

Wow only 8 hours, is that good or bad?

It's bad if you need it to last more than 8 hours. It's good if you don't.

As far as upgrading, what are some options that I have?

If you really need a constant 1200W and you need it to last more than 8 hours then you need to add more batteries. 4 more batteries will add roughly 4 more hours.

Also, I noticed that when the inverter is in use with a load, the charger doesn't seem to be charging the batteries at the same time?

Solar input will go to the load first. If the load needs more than the PV input then the load will get the balance from the battery. If the load needs less than the PV input then the extra PV input will go to the battery.

A 1200W load at 48V is about 25A. With the 150/75 SCC you should, in theory, be getting up to 75A but that is under ideal conditions with just the right set of panels. What PV battery current are you seeing during the day while the system is under load?

 

[kenryan]

If you really need a constant 1200W and you need it to last more than 8 hours then you need to add more batteries. 4 more batteries will add roughly 4 more hours.

One lesson from this example is that it illustrates the importance (desirability) of conservation. Unfortunately the cost of storage frequently means that we cannot consume as much as when connected to the grid.

 

[rizon]

S

4 100Ah batteries connected in series will give 100Ah capacity, so two 100Ah battery strings in parallel = 200Ah capacity.

 

[rizon]

So I have changed the BMV now to 200Ah instead of 800Ah, thanks for all the help. As far as upgrading: other than adding batteries, is it possible or beneficial to run (2) inverters, or should I upgrade to a specific brand of charge controller/inverter unit, What about more panels, ect. I, like all of you, just want to be prepared in case I need to rely on the system when the grid goes down!!

 

[rizon]

Batteries in series increase the voltage but the AH remains the same ..... so ... 4 100 batteries in series = 48V at 100 AH.

In parallel, the voltage remains the same but the AH doubles .... so ..... 2 48V 100 AH in parallel = 48V 200 AH.

Hey Bob, thanks for the reply, so my question would be, if I went with a 24V inverter and re-tapped the batteries would I be able to get 400AH instead of 200Ah @48V? What would be the disadvantage of that? Less ampacity?

 

[rmaddy]

It's all about battery capacity, power needs, and the ability to recharge batteries. The inverter and charge controller aren't really the issue.

You need to do a proper power audit to know how many watt hours you need in a day. Consider what you don't really need during a power outage (less TV for example). Once you know your real needs then you can size the batteries. Take into account that during a bad storm you may not have any useful solar for a couple of days so your batteries might need to support your power needs for 48 or 72 hours (another good reason to cut out certain things during a power outage (no hair dryer).

Another thing to consider is that if this is a setup you plan to only use a few days per year when the power goes out then you might want to forget all of this and get a gas/diesel generator. Why spends many thousands of dollars on a system you will hardly ever use?

But let's say you really, really need 1200W of power per hour. Over 48 hours that's 57.6kWh. One 12V 100Ah BB battery is 1.2kWh so you need 48 of those batteries to support 57.6kWh! Spending $50,000 just on batteries to support 1200W an hour for two days doesn't sound like a good plan. Find a way to use half that much power and you need half as many batteries. Again, this assume there is no sun or power over 48 hours to help recharge the batteries.

 

[rmaddy]

my question would be, if I went with a 24V inverter and re-tapped the batteries would I be able to get 400AH instead of 200Ah @48V? What would be the disadvantage of that? Less ampacity?

It makes no difference. 8 batteries is 9.6kWh. It doesn't matter how they are configured. It would be 12V @ 800Ah, 24V @ 400Ah, or 48V @ 200Ah. Those are all the same: 9.6kWh. And a 1200W load will last 8 hours either way.

 

[Bob B]

Hey Bob, thanks for the reply, so my question would be, if I went with a 24V inverter and re-tapped the batteries would I be able to get 400AH instead of 200Ah @48V? What would be the disadvantage of that? Less ampacity?

If you keep the same batteries and just configure them differently .... you will still have the same amount of power available .... just at a different voltage level.
If you drop from 48V to 24V ... you will need twice as much current to give you the same amount of power.

edit .... rmaddy beat me to the point.