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Old 25-06-2020, 10:49   #1
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Solar charge and dc loads problem

I have 1120 watts of solar, split between 4 panels earth with its own Victron MPPT controller. Not plugged into shore power, but I have an inverter/charger supplying AC (very low loads, at any given time maybe 1 amp120v. So total dc loads are 6-18 amps/12v. Strange thing is, as the solar output increases so does the load watts leaving a decreased balance amps going Toto the battery bank (700 ah Winston LiFePO4). REC-ABMS is controlling the Victron MPPTs. Click image for larger version

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What am I missing here. No sun, “DC power” is around 60-70 watts with a corresponding 5 amp DC load. With sun, only 500-600 watts solar output, 20 amps into the bank and 300ish out as “DC load” and there are no additional loads other than the original 5-6 amps DC.
Looking forward to your insights. Thanks.
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Old 25-06-2020, 13:13   #2
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Re: Solar charge and dc loads problem

Your batteries are nearly charged (91%) and can only accept the 20 A they are getting. The excess 300 A is diverted to load 'cause it has nowhere else to go.

If your batteries were more discharged (under same sun conditions) there would be more amps going to the batteries.
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Old 25-06-2020, 13:42   #3
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Re: Solar charge and dc loads problem

Makes sense, but I haven’t seen that as the case. Earlier this week the pack was down to 50% and the results were very similar. Also, panel output should be close to 1000 watts.
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Old 25-06-2020, 13:42   #4
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Re: Solar charge and dc loads problem

Quote:
Originally Posted by jamhass View Post
Your batteries are nearly charged (91%) and can only accept the 20 A they are getting. The excess 300 A is diverted to load 'cause it has nowhere else to go.

If your batteries were more discharged (under same sun conditions) there would be more amps going to the batteries.
No. This system does not have a diversion load... that's not how MPPT controllers work. And the batteries are Li, so they should take more than 20 amps at 90%...

How is the DC output power being measured? Is there a shunt? or is it doing it by subtraction? or is it reported from the BMS?

If you have a shunt, are you 100% sure that ALL the power input/output to the batteries go through the shunt? NOTHING bypasses it and is connected directly to the batteries? That would explain a lot of the inconsistencies in the presented data.
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Old 25-06-2020, 17:30   #5
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Re: Solar charge and dc loads problem

Correct, no diversions load. LFP so yes, should easily take high amps right up to upper knee. All loads are through the shunt. Positive cause I re-wired the batteries/charger/BMS/solar/controllers.
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Old 25-06-2020, 18:38   #6
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Re: Solar charge and dc loads problem

Ok. Here's a couple hours later.
PV charger = battery acceptance + DC Power (?).
Where the heck are those watts going?? Only thing connected is the Xantrex 3012 charger/inverter, which is pulling only 1 amp (120 volts). I can turn the inverter off and it has little effect on the "DC Power". Strange. Will explore further.
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Old 25-06-2020, 20:52   #7
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Re: Solar charge and dc loads problem

Unless you have a load shunt. I don’t see how it would even know the dc loads. Is it guessing based on solar - battery net?

You need to get a clamp meter and confirm the readings of everything going in and out.
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Old 25-06-2020, 21:03   #8
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Re: Solar charge and dc loads problem

Is there an idle load from the inverter?
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Old 26-06-2020, 05:27   #9
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Re: Solar charge and dc loads problem

Not being insulting but...are you absolutely certain that the only connection to the high side of the shunt is the battery B- and all sources' and loads' B- are connected to the low side of the shunt?

I ask this because I have corrected this miswiring of shunts many, many times on clients' boats.
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Old 26-06-2020, 11:58   #10
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Re: Solar charge and dc loads problem

There is a small draw from the inverter, but does account for the numbers evident.

Re: loads not included, I’ll quadruple check. Not insulted at all. Would be a major oversight on my part, but possible. The only negative that does not pass through the shunt is the starter negative, but that of course is not drawing a load. I’ll check again.
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Old 27-06-2020, 05:12   #11
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Re: Solar charge and dc loads problem

Following. Curious and learning.
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Old 27-06-2020, 07:14   #12
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Re: Solar charge and dc loads problem

[QUOTE=SVHarmonie;3171872]No. This system does not have a diversion load... that's not how MPPT controllers work. And the batteries are Li, so they should take more than 20 amps at 90%.../QUOTE]

Good point on the Li batts.

But

Many MPPT controllers DO have a diversion load. My Blue Skies does. Allows the controller to send excess power (that the batts and house loads can't accept) to something "useful" such as a water heater, etc. Some use the diversion as a second bank charger.
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Old 27-06-2020, 12:20   #13
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Re: Solar charge and dc loads problem

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Originally Posted by gscriba View Post
The only negative that does not pass through the shunt is the starter negative, but that of course is not drawing a load. I’ll check again.
You might disconnect that starter negative temporarily just to see if the DC load is affected. It's possible something else is tied to your engine/starter ground somewhere, in which case the starter negative lead could provide a path for other "sneaker" loads that wouldn't be measured across the shunt.

Also, do you have a Victron BMV and associated shunt, or is the battery amperage shown on your CCCV coming from the BMS, or somewhere else? If a BMV, and with the starter negative disconnected, that battery bank voltage/amperage shown on the CCGX should be the most accurate of the figures you see on the screen. The "DC Loads" figure is not measured anywhere, and is calculated by subtraction. The Victron documentation explains this, and that the reported DC load is therefore "approximate". Still, it shouldn't be off by that much.
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Old 27-06-2020, 12:39   #14
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Re: Solar charge and dc loads problem

Ah, I gather that the REC-ABMS will be directly connected to a shunt, and report the amperage it calculates to the CCGX. The REC can use different size/resistance shunts.. are you sure the REC has been configured with the correct coefficients for the exact shunt you have? If not, it would report incorrect current into/out of the bank, and the CCGX calculated DC loads would also be incorrect.
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Old 27-06-2020, 12:52   #15
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Re: Solar charge and dc loads problem

Quote:
Originally Posted by gscriba View Post
I have 1120 watts of solar, split between 4 panels earth with its own Victron MPPT controller. Not plugged into shore power, but I have an inverter/charger supplying AC (very low loads, at any given time maybe 1 amp120v. So total dc loads are 6-18 amps/12v. Strange thing is, as the solar output increases so does the load watts leaving a decreased balance amps going Toto the battery bank (700 ah Winston LiFePO4). REC-ABMS is controlling the Victron MPPTs. Attachment 218059

What am I missing here. No sun, “DC power” is around 60-70 watts with a corresponding 5 amp DC load. With sun, only 500-600 watts solar output, 20 amps into the bank and 300ish out as “DC load” and there are no additional loads other than the original 5-6 amps DC.
Looking forward to your insights. Thanks.


Hey gscriba

I wrote another post, but it seems to be lost.

I take it you do have Li?

1. Your controllers will match their output to the load. What are the settings on your controllers? You can see/change it on the Victron Connect app.

2. The 100% value is somewhat calculated, so you have to check the voltage of your battery.

3. What is the status of your controllers? You can check that on the CGX or on the Victron Connect app.

4. What does the VRM tell you. Much more info there.

HTH
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