Can't find the error in my system. BMV perhaps?

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missy asked May 14, '20

Can't find the error in my system. BMV perhaps?

Hi!

I have a Victron BMV-712, the shunt is correctly wired as per its instructions. It worked fine when it was monitoring the drain on the house batteries from the loads, and the charge to the batteries from the Victron mppt 150/45.

My problems started when I added a Victron Orion tr 12/12-30. I set up it's charging profile using the data from the battery manufacturer (Photonic Universe).

Bulk/abs 14.20 Cond. 13.85 Float 13.50

The Orion would never stay in Bulk for more than a couple of minutes, regardless of how little battery percentage I had left. I was at 65% and still it went straight to float, or sometimes absorption for a few minutes then float.

Now I'm parked in one spot I've been plugged in to the mains most of the time. The other day the BMV showed 64% - sounds reasonable, I had been unplugged for several hours, it had been cloudy on and off, and I had used my laptop for gaming which does use a lot of power. I couldn't plug in the next day, so I ran down to 56% - but my heater still turned on. My heater doesn't work unless the battery is at 75% or higher!

So I'm wondering if the Orion is working correctly, but perhaps we often have more battery power than the BMV is showing?

Please note that the "starter battery" on the BMV is not the starter. It's simply connected to my battery bank.

Here are screenshots of everything on my app today as I drove. I had been unplugged for only 10 minutes or so.

I also include a drawing of my system. The positive and negative feeds from the mppt and the Orion originally went to the positive and negative bus bars respectively, but when trying to get the Orion to do something other than float, I took advice to move them to their current positions on the house batteries.

Thanks for any help or guidance you can give me, I'm completely lost now and way out of my sphere of knowledge!

battery charging

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Answer 1 · 2020-05-14T14:17:23Z

JohnC answered · May 14, 2020 at 02:17 PM

Hi @missy

Your negative wires are all messed up. You have a neg bus with the BMV shunt hanging off it, yet you've bypassed the shunt twice and gone direct to the batts. So those items won't be counted in the SOC. Reroute them to the neg bus. The positive wires won't matter.

Ignore your SOC, as it will be wrong, probably very wrong. For now, just use V and assess your batts manually.

I'm not sure what your Orion is actually doing, re which way it's actually charging, but if it's pushing to the 'starter' batt, then it's doing you a favour going to Float early.

Your screenshots have confused me too, as you haven't captioned them, but what I can easily glean, maybe all ok. Aside from the BMV/SOC.

But please come back..

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missy commented · May 14, 2020 at 02:42 PM

Thanks! That makes sense.

Re the Orion, the input cables come from the starter to the Orion and the output cables come from the Orion to the house batteries.

So I'll move the Orion and mppt negatives from the house batteries back to the negative bus.

Wait till I'm fully charged then manually set the soc to 100%?

Thanks very much!

Missy

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JohnC ♦ missy commented · May 14, 2020 at 02:58 PM

@missy

Yeh, charge up and then sync. Then see how it comes together. Just one neg cable from the shunt to the batts you want monitored, hey..

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missy commented · May 24, 2020 at 11:51 AM

Hi!

I've moved the negative cables (mppt and Orion) from the battery to the negative bus, and left the positives on the battery as shown in my original post.

While driving today, when I left I was at 86%, having reached 100% yesterday then unplugged.

My solar was in bulk charge, but the Orion was in absorption again! If they are using the same charging profile, should they not both be in the same stage?

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JohnC ♦ missy commented · May 24, 2020 at 12:21 PM

@missy

Your Orion is pushing a different V. You'll need to find out why that is?

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missy JohnC ♦ commented · May 24, 2020 at 03:33 PM

Sorry, pushing a different V to what?

The Orion is pushing 14.7V

The house battery is at 13.49V

I've never understood the settings - the Orion is set at:

Ab 14.70

Float 13.80

Rebulk Voltage offset 0.40

If the higher the voltage, the "fuller" the battery, why is absorption a higher voltage than float?

The above suggests that the Orion should be in bulk until it reaches 14.70V then absorption until 13.80 then float. That doesn't make sense!

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JohnC ♦ missy commented · May 25, 2020 at 04:36 AM

@missy

What I was getting at there is that both the BMV and mppt are showing 13.49V (maybe even sharing that via networking), and the mppt is in Bulk phase (as it should be).

Yet the Orion shows 14.7V on it's output, presumably feeding the same batts. Now it's always possible that it's faulty, but far more likely to be caused by a fault in wiring or a bad breaker. ie, it's not actually connected properly to the batts. So it's trying to push current against a brick-wall, quickly reaching the target V on its side of the fault, and backing off.

A cheapo $10 multimeter could find this or confirm a fault in the Orion.

Btw, 14.7V is quite a high Absorb setting, and it's unusual to have 2 chargers set that far apart. But you may have a reason for doing this.

The length of Absorb phase may be set by an algorithm or to a fixed period. Once achieved, it will revert to a lower Float setting, and the charger(s) will back off to maintain that to 'top off' the batts with a less aggressive V.

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missy JohnC ♦ commented · May 26, 2020 at 02:35 PM

Thanks!

I'll find my multimeter and have a look see.

I've been advised by a friend to disconnect the cable from my negative bus to the negative of the starter battery. I had it there to ground my system, but he's suggesting it may be causing the problem.

Could that be it?

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