Victron 100/50 seems to skip Absorb stage of charge

bigbillsd · October 2018

I just finished my second night of dry camping. Yesterday morning my batteries were down a bit below 70% SOC prior to sunrise in the New Mexico desert. By about 11:30am there was a steady 30+ amps going into the battery and based on my Trimetric were close to 80% SOC, close to moving to the Absorption stage. At 12:15pm, 45 minutes later I checked the controller and it was in Float putting in an amp or 2. Based on Victrons chart for Absorption times, it should have run for 4 hours. I see no way to tell if it ran for 5 minutes, 30 minutes or skipped it completely.

Consequently the batteries never got up to 81% SOC even though I had almost 6 more hours of bright 5000' elevation sunshine. I have the controller set to 6 hours for Absorb, but I think that is just the max and the length of that stage is controlled by the starting voltage of the batteries in the morning for what the manual states. I'm starting to wonder if there is something wrong with this controller or just made a horrible decision buying a Victron controller.

Is there a way to force the controller into absorb? The float stage won't even keep the amperage coming from the batteries even, as we are drawing more than its charging.

Help!

Photowhit · October 2018

How are you measuring the State of Charge?(SOC)

How large of a battery bank do you have? and what type? at 80% SOC lead acid batteries start reducing the amount of current they will absorb. Also other factors can reduce or turn off the charging. Battery Temperature Sensor (BTS) may have found the batteries where getting very hot and reduced the voltage running to the batteries.

...and of course it may also be that the capacity setting on the Trimetric may be wrong. You say the Trimetric was "...close to moving to the Absorption stage". This stage will be determined by the charge controller. Once the voltage starts (running away) it will limit the voltage at this point you have reach absorb. If you were running an air conditioner perhaps you would have used a lot of energy over night, but 30 amps at 14.5 volts for a couple hours would replenish a battery bank running an efficient fridge and fans over night.

Even setting a charge controller to run for 6 hours in absorb, most will shut down when they sense the batteries aren't taking more than 1-2% of their battery capacity, an indicator that the battery is fully charged.

bigbillsd · October 2018

Photowhit said:

How are you measuring the State of Charge?(SOC)

How large of a battery bank do you have? and what type? at 80% SOC lead acid batteries start reducing the amount of current they will absorb. Also other factors can reduce or turn off the charging. Battery Temperature Sensor (BTS) may have found the batteries where getting very hot and reduced the voltage running to the batteries.

...and of course it may also be that the capacity setting on the Trimetric may be wrong. You say the Trimetric was "...close to moving to the Absorption stage". This stage will be determined by the charge controller. Once the voltage starts (running away) it will limit the voltage at this point you have reach absorb. If you were running an air conditioner perhaps you would have used a lot of energy over night, but 30 amps at 14.5 volts for a couple hours would replenish a battery bank running an efficient fridge and fans over night.

Even setting a charge controller to run for 6 hours in absorb, most will shut down when they sense the batteries aren't taking more than 1-2% of their battery capacity, an indicator that the battery is fully charged.

My battery bank is 520 AH comprised of 4 each 6v Crown 260 AH LA batteries. I double checked the Trimetric settings, they are still good. I had to run the genny last night to get the batttery back up to 95% SOC prior to 10pm, my Magnum 2812 showed the batteries were still accepting a hefty charge of about 10amps in Absorb when I had to shut it down for quiet time. The Trimetric had the battery at 79% when I looked at it around 11:30am while the controller said it was pushing in 30+ amps. 45minutes later, controller in Float and the batteries were at 13.5 volts, the absorb voltage is set to 14.5 volts per the manufacturer.

Yes, I understand that my 6 hour setting is max, not what will run, that is based on the voltage at startup according to the manual.

Thanks, Bill.

Estragon · October 2018

Although I find my Trimetrics to be useful for day-to-day monitoring, the SOC readings alone can be misleading. This is especially the case if the bank spends much time in what the TM thinks is a partial SOC.

Your TM settings may seem good, but there are a lot of variables (eg. definition of "full", battery charge efficiency, etc) which are difficult/impossible to accurately set. Efficiency, for example, can only be set to an average value, but actual efficiency varies a lot at different states of charge (near 100% at low SOCs, near zero at very high SOCs).

10a may seem like a "hefty" rate, but at ~2% of your 520ah capacity, it indicates a nearly full SOC.

Estragon · October 2018

Also, you may want to check out TM history values, H8 in particular, to get a better sense of what was happening for the CC to go to float after the apparently too-short absorb.

bigbillsd · October 2018

That 10 amps was after three hours of genny charging. 125 amps were going into the battery bank for the first hour on generator while the Magnum was Bulk.charging it back to 80%. I see no evidence to think the Trimetric is wrong. The Victron was putting in its full power available from the panels while in Bulk from 8am till almost Noon. Why would it go from Bulk charging for many hours, then to Float in a few minutes. That makes absolutely no sense at all unless I have something setup wrong or its broken. The setup looks correct to me. So I still have to think the controller is broken or some other factor is at play. It was warm yesterday, but not that warm. I checked the temp compensation setting, its 16.20mV/C I need to look up to determine if that is a correct setting, that appears to be the default. -Bill

Dave Angelini · October 2018

As Photowhit asked you to check or verify. What is the end amps set for in Absorb?

Estragon · October 2018

Also, what amperage was "it's full power available from the panels"? What time was the temp-compd absorb voltage reached?

The controller doesn't care what the TM thinks the SOC is. To diagnose a possible problem with the CC, you need to know the values it does care about.

bigbillsd · October 2018

Dave, there isn't a setting to adjust Amperage on the victron controller, just voltage which I mentioned is 14.5 volts per my battery manufacturer. There is a setting to enable the 50 amp charger or disable it.

Dave Angelini · October 2018

We are talking amps not volts right?

You should read the manual or ask Victron what algorithm they use to transition from absorb to float.

Photowhit · October 2018

So it looks like there is no BTS for this charge controller. Are the controller and the batteries in the same temperature area?

From the manual;

https://www.victronenergy.com/upload/documents/Manual-BlueSolar-charge-controller-MPPT-100-50-EN-NL-FR-DE-ES-SE.pdf

Image: https://us.v-cdn.net/6024911/uploads/editor/r8/unieg1e3he6k.jpg

Looks like the ending current is 2 amps, so that shouldn't be a problem, What are your loads during the day?

Also what and how is your array configured? Was this a 12 volt system setup with a PWM with all panels in parallel and switched to MPPT?

bigbillsd · October 2018

I figured out what happened. It appears a circuit breaker on the battery side of the controller popped but did not move to show it opened the circuit, so I did not see it. And for some reason the controller showed float and about .4 amps going to the battery, but that must be false as there was no battery connection after the breaker went. I found it when trying to figure out why I wasn't doing anything but Float this morning too. I discharged the batteries about 30% overnight so still showing float at 10am was more cause for concern.

When I touched all the breakers, one lever moved showing it had popped, probably yesterday.

I was able to reproduce the issue just now. I used the toaster via the inverter. It appears when there is a large load, like the toaster pulling 85 amps the power output from the controller drops to almost nil, and somewhere in that minute of two the same battery side 50amp breaker blew, the one that connects the controller to the battery cables.

Now that is a quandary. I guess I will start another post to figure out why the breaker pops and why the output goes to nil when their is a large load from the inverter.

It seems to work as I expect when there is just a low load on the inverter. With most things running on the inverter i will normally see a 10-11 amp draw from the batteries via the Trimetric meter. When the panels are producing, that negative draw lowers slowly as the power from the controller goes up, around 10 am it starts to go positive, currently its a positive flow into the batteries at 22 amps, the controller says its putting out 33.5 amps so the 11 being used plus the 22 amps flowing into the batteries is very close the the reported controller output. Is the inverter trying to pull those 85 amps from the controller instead of the batteries as the controller is a shorter path than the batteries?? Although only 6 guage cable vs 4/0 to the batteries.

This is a new 640watt system all serially connected to keep the panel amps low for 35' wire runs to the controller.

-Bill

Estragon · October 2018

I think current will want to go between points with the highest potential voltage difference. The difference would be higher at the controller while charging, so current would flow from there to the extent available. I'm a bit surprised enough current would be available through the controller to flip a 50a breaker though. 50a@12v=600w

Note that with the battery breaker open, the controller sees only panel string voltage, and being 12/24v, it may get confused if it wakes up in the morning with no battery voltage.

bigbillsd · October 2018

Yes, I was concerned that the controller would have been damaged once I figured out what happened. It does not appear to have received any problems yet. Still in bulk at 3:40 in the afternoon. Controller says battery voltage is at 13.80 volts. I am not sure how the controller knows when to move to Absorb, my Absorb setting is 14.5, will bulk charging continue to happen till it hits that Absorb voltage setting in the controller? I have not seen an explanation on how that works anywhere. Anyone know of a good write up? I wonder if Victron works similar to anyone else that has a write up. -Bill

Photowhit · October 2018

Here's a real simple explanation I use with a Facebook group;

To run through your original post, The voltage you are seeing is the system voltage and not the battery voltage. If you are connected to charging or a load it will effect the system voltage.

During charging, there are basically 3 stages of charging, Bulk, Absorb, and Float.

BULK;
First thing when charging starts you will be in bulk, the voltage rises from what ever the system voltage was to a set point, around 14.5 volts. At that point the Charge controller stops the voltage from rising. Higher voltage can damage sealed batteries.

ABSORB;
Once the battery hits the preset point the charge controller keeps it at that point. Your batteries are roughly 80% full. Flooded batteries will start accepting less current at 80-85% full AGM/Sealed may go a little longer before accepting less current.

On many controllers you can set this point, Some will have different presets for Flooded, and sealed batteries, or flooded, AGM, and sealed batteries.

The charge controller has a couple ways to know when to switch to float, Most inexpensive Charge controller are just timed for 1.5-2 hours. Some will also see less current flowing through the charge controller and shut it down when minimal current is flowing through the controller. On more expensive charge controller. You can set battery capacity to give the Controller a better idea of when to stop. you can also set a longer Absorb time. Or set 'end amps' a amount of amps flowing through the charge controller to stop Absorb and switch to the final stage.

FLOAT;
Once the Controller has determined the battery is fully charged it reduces the voltage to a point where very little current is flowing to the battery. This will prevent the battery from over charging and heating up.

While in 'Float' the charge controller watch for voltage drop, which would indicate a load. If the voltage begins to drop the charge controller will allow as much current to flow from the panels/array to compensate and maintain the voltage. If the voltage can be maintained, the load will in essence be running directly off the array/solar. If the voltage drops below the preset float voltage, the controller may start a whole new cycle if it stays there for a period of time.

The system voltage drop you see at night when the sun goes down is the charge controller moving into a resting mode with no energy to contribute to the system.

The morning voltage may reflect a load present that is effecting the voltage level. With sealed batteries, you would want to disconnect the battery from the system and allow it to 'rest' for a while to get an accurate idea of it's SOC (Sate Of Charge) from the voltage

Estragon · October 2018

The controller isn't likely to be damaged, but could get confused. With some CCs, if it sees pv voltage but not bank voltage, it could think 24v nominal. In many cases, it would likely just throw a low battery cut-off error when connected to a 12v bank in 24v mode. If not though, it could expose the bank (and any connected DC devices, like inverter input) to higher voltage than they can handle.

Victron 100/50 seems to skip Absorb stage of charge

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