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Kodak King & BMV-700


DeeJay
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Hi guys,

I have a client that insisted on working with deep cycle batteries instead of lithium.

I installed a 5kW King and solar panels on his roof.

We installed the 4x 102Ah deep cycles and connected them up to the inverter.

In order to monitor the installation remotely, I installed the ICC hardware as well.

So, once installed, we ran a test, and performed a shutdown in the evening (no solar).

The batteries lasted 1h15min with an average of 500w load.

Now, my calculations show that 48v @ 102Ah would give you roughly 4900w of usable power. Lets assume the inverter caps that low end of the batteries at 50%, then we should still get 2450w of usable power, which, at 500w/h should equate to roughly 4-5h of autonomy.

Well, 1h15min is nowhere close, so I purchased a Victron BMV-700 to show exact state of charge of the battery bank.

I calibrated it correctly and it showed 100%.

We reran the test and still, it shut down after 1h15min, even though the BMV showed 78% remaining.

This leads me to believe that either one of the batteries is faulty, causing the battery bank to fail, OR the BMV is not sending its data to the inverter properly, thus the inverter is still controlling the shutdown based on the voltage across terminals (very inefficient), OR the BMV is not wired into the install correctly (why would it then show the correct SOC and draw while on batteries?).

I have wired the BMV up exactly as it shows in the manual. It's not rocket science.

It seems to me that the inverter is not getting the info from the ICC module. I have spoken to the guys at Centurion Solar, who manufacture the ICC hardware, but we have not been able to find a solution.

Is it possible to connect the BMV-700 directly to the King so that it can see SOC correctly?

If not, then what exactly is the point of the BMV? Just for me to see whats happening?

At the end of the day I need the inverter to monitor the batteries based on the BMV's SOC.

Has someone done this before, and if so, how do I set this up?

Many thanks

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@DeeJay,

The purpose of the BMV is to tell ICC what is going on with the battery. As you know, the King/Axpert/Infini's doesn't do a good job of that, so hence the addition of the BMV.

It would be interesting to know what the voltage of the bank was when the SOC was still @ 78% and the shutdown happened. Then compare that to the setting on the King that talks to Low Voltage cutoff. If I remember correctly (via one of @Coulomb's posts, there is a offset between the 2, so you could try and adjust that parameter so that the cutoff happens @ roughly 50% SOC. Taking a linear approach, that should give you another 1:15 hours, taking the total to 2.5 hours, right as you predicted. The missing 1:15 is still in the batteries, you just haven't got access to it, with your current settings, it seems.

The shutdown of the inverter is done on the values the inverter reads directly from the Batteries, and not the BMV. The BMV merely reports all its info to ICC.

I have a suspicion the latest version of ICC can "switch" on BMC SOC, but I'm still a few versions behind, as one looses your info during the upgrade, as it is a new image.

Maybe if someone has documented a procedure to dump the database and import it, that would be super to share.

Edited by Sidewinder
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3 hours ago, DeeJay said:

Now, my calculations show that 48v @ 102Ah would give you roughly 4900w of usable power. Lets assume the inverter caps that low end of the batteries at 50%, then we should still get 2450w of usable power, which, at 500w/h should equate to roughly 4-5h of autonomy.

48 V x 102 Ah ≅ 4900 Wh; volts times amp·hours = watt·hours. Is it possible that the battery isn't getting fully charged, e.g. due to the premature float bug?

3 hours ago, DeeJay said:

Is it possible to connect the BMV-700 directly to the King so that it can see SOC correctly?

No.

3 hours ago, DeeJay said:

If not, then what exactly is the point of the BMV? Just for me to see whats happening?

It's so that ICC can take over some of the decisions that the inverter would otherwise make based solely on battery voltage. You can tell ICC to switch to grid at 50% SOC (as reported by the BMV), rather than say 49 V. But for that to work, the inverter's settings have to be "out of the way" so that the inverter doesn't switch prematurely to grid. I don't know if you have to do that yourself, or ICC does that for you.

I note that the BMV has to be told what the amp·hour rating of the battery is, via some of its own settings (though maybe ICC can tell it that). Is this set to 102 Ah? There are a few other settings, e.g. tail current and Peukert factor, that need to be set up properly for the BMV to accurately estimate the SOC of the battery.

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3 minutes ago, Coulomb said:

It's so that ICC can take over some of the decisions that the inverter would otherwise make based solely on battery voltage. You can tell ICC to switch to grid at 50% SOC (as reported by the BMV), rather than say 49 V. But for that to work, the inverter's settings have to be "out of the way" so that the inverter doesn't switch prematurely to grid. I don't know if you have to do that yourself, or ICC does that for you.

I note that the BMV has to be told what the amp·hour rating of the battery is, via some of its own settings (though maybe ICC can tell it that). Is this set to 102 Ah? There are a few other settings, e.g. tail current and Peukert factor, that need to be set up properly for the BMV to accurately estimate the SOC of the battery.

@Coulomb
Thanx for the reply.
I also thought that this is what was supposed to happen...BMV reports to ICC and then pushes this data to the King so that it can work on those readings instead of is own battery voltage readings.
@Bloubul7

I have set the cutoff voltage all the way down to 42v to try and get it out of the way, but it doesn't seem to help.
I have set up the BMV based on the 102Ah rating, and waited until the batteries were fully charged before inputting this data and commissioning the BMV, so I believe the BMV is reading SOC correctly.

@Sidewinder

Voltage was at 45v when the shutdown occurred...
 

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2 minutes ago, DeeJay said:

BMV reports to ICC and then pushes this data to the King so that it can work on those readings instead of is own battery voltage readings.

Actually, the inverter will still display its wild guess for SOC, so just ignore that. What I believe ICC does is to send commands to trigger a change to grid mode when it reads the appropriate SOC value from the BMV.

3 minutes ago, DeeJay said:

Voltage was at 45v when the shutdown occurred...

Ah. Then it seems that the battery is either low capacity, or isn't being charged fully.

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2 minutes ago, DeeJay said:

Back to Grid is at 44v. Does this need to be lowered?

No. You don't want a lead acid battery going under nominal volts, i.e. 48.0 V. So that should be fine.

You need to find out what voltage the inverter is charging the battery to, and how long it stays there.

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3 minutes ago, Coulomb said:

No. You don't want a lead acid battery going under nominal volts, i.e. 48.0 V. So that should be fine.

You need to find out what voltage the inverter is charging the battery to, and how long it stays there.

On ICC I've got bulk charging set to 56.4v and Float at 54.0v

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23 hours ago, DeeJay said:

On ICC I've got bulk charging set to 56.4v and Float at 54.0v

Sorry, I wasn't clear. You need to find out how long the battery spends around the 56.4 V area, before it goes to around 54.0 V. With the premature float bug, it can go to float too early, sometimes never even reaching anywhere near 56.4 V. This leads to chronic undercharging of the battery, which can prematurely age the battery, and of course you get less run time from the battery (both as a result of the lack of proper charging, and over time, as a result of the battery losing capacity even in those situations (such as a completely cloudless day) where it does charge properly.

A graph of battery voltage on an intermittently cloudy day will show whether this problem is happening. 

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15 minutes ago, DeeJay said:

Heres a screenshot of what it looks like today. Rainy miserable weather...

Huh. At the end is a near-textbook linear ramp down of charge current, to about 5 A, then transition to float. Just as it should be.

See if you get reasonable run-time tonight.

Are you battery modules AGM? If so, they probably need a higher charge voltage than 56.4 (14.1 V per 12 V module).

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