Solar switching to absorption and float with low SOC

[Delboyarapaho]

I have 2 x 90ah lithium batteries with 290w solar on top connected through a victron 100/30 mppt.
I monitor what charge I get through the victron app and my SOC through my battery app (super B).
My SOC started in the high 90%s and I ran the kettle a few times bringing the Soc down to about 70%. We went out all day and when we returned the Soc had only recovered to 76%. The solar produced 540wh of energy that day but spent only 28% (4 hrs 30) on bulk. The rest of the time it was on absorption (4hrs) and float (8hrs). Next couple of days the same is repeated with upto 700 wh generated but we now have a 48% Soc and I am getting very concerned that the Soc isn’t being recovered by the solar. I have nothing on (alde off 24/7 and inverter only on to use it) and thinking there is something wrong with this set up because if this was winter with short days poor sunlight and the heating on our batteries would have been down to zero by now.
I wonder why the victron is switching to absorption and reducing the charge amps when the Soc is so low and is there a setting that can be changed to enable the full benefit of the wh to be converted into amp hrs?

 

[Steve and Denise]

We have just had the very same problem Victron and 300ah lithium,
Long story short the controller was fitted where Carthargo say but the battery was in the rear of the van the output cable 6 Sammy was to long at 5mtrs, our answer was to move the Victron closer to the battery no more problems

 

[Delboyarapaho]

We have just had the very same problem Victron and 300ah lithium,
Long story short the controller was fitted where Carthargo say but the battery was in the rear of the van the output cable 6 Sammy was to long at 5mtrs, our answer was to move the Victron closer to the battery no more problems

That’s interesting. My solar controller is right at the back of the van and batteries just behind drivers seats so certainly more than 6m cable run.
What I don’t understand is why I get some charge but nowhere near as much as I should?

 

[Steve and Denise]

Ours was doing the strangest of things all down to the distance between the regulator and the battery, we tried all sorts added heavier cables all the settings nothing moved the controller everything works as it should, took me some getting my head around

 

[Delboyarapaho]

Thanks for that sounds most peculiar I will discuss that with the dealer as it’s still under warranty

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[Steve and Denise]

Ours was all over the place for no good reason when we used the dealers pre wiring but then I asked Victron and took their advice problem fixed,
Your dealer probably has less idea than you and will give you some bullshit but if they fitted it they should do it Victron specifications

 

[Delboyarapaho]

Ours was all over the place for no good reason when we used the dealers pre wiring but then I asked Victron and took their advice problem fixed,
Your dealer probably has less idea than you and will give you some bullshit but if they fitted it they should do it Victron specifications

Yes that’s my concern

 

[Steve and Denise]

Who is the dealer ? Keep well away from Premium

 

[Steve and Denise]

Sound familiar Dave Ditcha

 

[Raul]

Can you post your solar charger settings? Without knowing the settings is hard to pinpoint the cause of premature float, also the wire length and size is important for voltage drop. It should be almost no drop from controller to battery, otherwise it will never charge to the settings parameters.

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[autorouter]

The problem with long cables is the voltage drop. The controller on its own can only measure the voltage at the start of the cable, not at the far end. So it might think the battery voltage is quite high when in fact it's actually on the low side.

The solution is to find a way for the controller to know the true voltage at the battery terminals. Victron do a device called Smart Battery Sense that literally sticks on the side of the battery, with a couple of wires to the terminals. It sends accurate battery voltage and temperature data to a Victron SmartSolar controller by Bluetooth.

It's cheaper than a Victron SmartShunt which does the same but also measures amps and state of charge. The solar controller already knows what amps it is sending, so doesn't need that measurement.

Victron Energy Smart Battery Sense Voltage and Temperature Sensor Long Range 10m SBS050150200 - Low Energy Supermarket

Smart Battery Sense is a wireless battery voltage and temperature sensor for Victron MPPT Solar Chargers.With voltage and temperature sense in place, batteries will be better charged; improving charging-efficiency and prolonging battery life.

lowenergysupermarket.com

 

[The Wino]

I recon it's likely your solar regulator is set to the wrong battery type and is stopping the bulk charge at too low a voltage for lithium

 

[Steve and Denise]

The problem with long cables is the voltage drop. The controller on its own can only measure the voltage at the start of the cable, not at the far end. So it might think the battery voltage is quite high when in fact it's actually on the low side.

The solution is to find a way for the controller to know the true voltage at the battery terminals. Victron do a device called Smart Battery Sense that literally sticks on the side of the battery, with a couple of wires to the terminals. It sends accurate battery voltage and temperature data to a Victron SmartSolar controller by Bluetooth.

It's cheaper than a Victron SmartShunt which does the same but also measures amps and state of charge. The solar controller already knows what amps it is sending, so doesn't need that measurement.

Victron Energy Smart Battery Sense Voltage and Temperature Sensor Long Range 10m SBS050150200 - Low Energy Supermarket

Smart Battery Sense is a wireless battery voltage and temperature sensor for Victron MPPT Solar Chargers.With voltage and temperature sense in place, batteries will be better charged; improving charging-efficiency and prolonging battery life.

lowenergysupermarket.com

I fitted a smart shunt still not right until I moved the controller then all was perfect

 

[Delboyarapaho]

Ok thanks to everyone who commented today and here’s some feedback. Called the dealer (go European who I have always found to be very responsive and good) and explained the problem they said they would look at it straight away given I was in the area.
Went there this afternoon and they admitted they didn’t have an answer. Between us we called a victron U.K. rep and he made several suggestions.
1) the cable length between the charge controller and batteries is too long (probably 10m)
2) the diameter of the cable used by carthargo is too small (4 to 6mm used)
3) my panels are connected in parallel rather than in series so I am not getting as higher voltage as I might.
Debated the options for what to do and either replace the cable or move solar controller.
We have agreed to move the controller next to the batteries and we are booked in for a few weeks time.
I believe they are going to link the panels in parallel at the same time.
Explanation given by victron rep was the set up will be ok in cloud and full conditions but voltage drop would impair ability to gain higher amperage’s and parallel wiring brings down the voltage so we are losing out both ways.
I did reset the voltage on the controller for absorption to 14.6 and victron man said it would be ok to increase the normal 2 hours absorption time to 4 hours to at least force the set up to remain in absorption longer rather than going to float until the set up is changed.
Thanks again to everyone

 

[Raul]

10m is way to long. Very bad practice. Move the controller near battery, and I did a calc for you, at full load 290w 12v, 1m long 6mm2 cable will have a loss of 0,2v 1,6%. Acceptable but will help if you fit a smart batt sense and network that with the charger. Then the charger will receive the data from it, and adjust accordingly.
The parallel it’s better option, if your panels output 18-19v when it starts, that’s all it needs.
The 4 hrs absorb without tail current is really really bad for your batteries. The most degradation takes place in the time you spend at high voltage. I would put at least 1A tail current for anything above 2hrs absorb.
Maybe you don’t have enough solar to harvest what you take out in one day, hence you may work in deficit. Even at 13,5v, if the battery is not full, it will gobble amps in, if available.

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[Delboyarapaho]

10m is way to long. Very bad practice. Move the controller near battery, and I did a calc for you, at full load 290w 12v, 1m long 6mm2 cable will have a loss of 0,2v 1,6%. Acceptable but will help if you fit a smart batt sense and network that with the charger. Then the charger will receive the data from it, and adjust accordingly.
The parallel it’s better option, if your panels output 18-19v when it starts, that’s all it needs.
The 4 hrs absorb without tail current is really really bad for your batteries. The most degradation takes place in the time you spend at high voltage. I would put at least 1A tail current for anything above 2hrs absorb.
Maybe you don’t have enough solar to harvest what you take out in one day, hence you may work in deficit. Even at 13,5v, if the battery is not full, it will gobble amps in, if available.

Thanks. Agreed with dealer to move the controller so it’s next to batteries.
Change to 4 hours is temporary until the controller is moved but thanks I will change the tail figure
I really think I have enough solar as my previous van had only 100w and most days it fully recovered. This week I have had the alde off and couldn’t have used less 12v (out every night)
I need to look into the smart battery sensor. Are you able to provide me a link to some data please?
Victron advised series as the voltage would be lower in parallel. Today v max was 21.5v but frankly I don’t know which is best. Reading victron own data suggests we get highly v if we can be mainly in the sun/not in shade, which I think applies to us.

 

[Raul]

Here is a link,

Smart Battery Sense - Victron Energy

Improve the charging-efficiency and prolong the life of your batteries with the Smart Battery Sense. Find a dealer near you.

www.victronenergy.com

The 21v is plenty, that’s not you cause of premature float charge. There are pros and cons for series vs parallel. You could try and see what’s best for you. Generally, for long distance to the panels, not in your case.

 

[Delboyarapaho]

Many thanks