I understand what you are saying, but the mppt if it is going off voltage would go to the same point each day surely? Not reaching 100% ever but failing by the same amount?
Strange SOC graph
- Thread starter BigDean
- Start date
I understand what you are saying, but the mppt if it is going off voltage would go to the same point each day surely? Not reaching 100% ever but failing by the same amount?
- Apr 19, 2019
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It seems an awfully coincidental thing if it's not the sun. Even if there is plenty of it, it has less energy at an angle.
I agree with Pausim on this one. You guys seem to mix the bmv settings with the charger settings that we don’t know. Peukert value of 1.05 is close, so the coulomb counter is not that much far out because of that. I seen peukert set at 1, 1,02 and 1,03 with no noticeable difference. The peukert accounts for discharge but also for charging as well. If you don’t pull big loads and don’t have a high charge rate, a peukert of 1 is spot on. Since this rates are variable, to cover 0,5C discharges, that’s why is been recommended the 1,05 value. Personally I think is to high.
His OP, real dilemma is to compare the SOC graph with the harvest graph.
Also it mentioned that has days with sun and this does not reflect in the SOC graph. This can be two thing: the deficit is large enough for the solar to catch up, or some settings in the charger is stoping charge to soon. Could be low temp cut off, tail not set, or simply not enough light. Given the float drop at 13,8v should still charge a discharged lfp.
His OP, real dilemma is to compare the SOC graph with the harvest graph.
Also it mentioned that has days with sun and this does not reflect in the SOC graph. This can be two thing: the deficit is large enough for the solar to catch up, or some settings in the charger is stoping charge to soon. Could be low temp cut off, tail not set, or simply not enough light. Given the float drop at 13,8v should still charge a discharged lfp.
- May 16, 2021
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IMO, the comments about the charging being limited by the available solar harvesting I would say is wrong. If you look at the graph, the battery would seem to being charged by just about the same amount each day. That is unusual and would point to a charger being turned off as the limitation. The reason the SOC is dropping overall is the draw is greater than the amount the solar charger is being allowed to provide (due to the premature change to float mode with the too low absorption time).
We shall see now the CV time has been increased to 4Hrs is that is the case or not
(I would not have changed to Adaptive mode though. Just left in the timed fixed mode. The controller will go to float before that time is reached IF the batteries are fully charged anyway)
We shall see now the CV time has been increased to 4Hrs is that is the case or not
(I would not have changed to Adaptive mode though. Just left in the timed fixed mode. The controller will go to float before that time is reached IF the batteries are fully charged anyway)
As I read the SOC graph the battery hasn’t been at 100% since the beginning of October. Each day the solar charging loses a little more ground and the maximum SOC declines accordingly, so that by 18 Oct the maximum SOC has fallen below 90%. All entirely consistent with sun steadily falling lower on the horizon and the daylight hours shortening.
Between September and October the solar angle in Bath has fallen from 39° to 31°, which is bound to reduce charging. Once the angle is below 45° the panels would be better off hung vertically on the side of the van rather than being horizontal on the roof. I think people expect too much of solar in the autumn and winter with the weaker sun and shorter daylight hours.
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So, after making the changes, here is today; which is exactly as I would have expected in the first place. By lengthening the absorption time, it allows the battery to get up to full charge/14.4v, then down to the 13.8v, then tails off at the end of the day when the solar stops producing power.
The jump to 100% is when I reset the SOC on the BMV to 100%.
Will see what happens tomorrow.
Thanks again all.
The jump to 100% is when I reset the SOC on the BMV to 100%.
Will see what happens tomorrow.
Thanks again all.
It will be interesting to see the SOC graph over the next few weeks with the new settings.
If you set a fixed absorbed time, make sure you have some tail current to. Lfp charges with constant current and constant voltage, no absorb. If you set a fixed absorbed time, and no tail current, you will risk in one day to hold those batteries at high voltage unnecessary for duration of absorb time, with full battery.
I have it on adaptive, so should not encounter this? If I still need to set this, what ampage would you recommend? Thanks.
I disagree with you on this one. If you look at Andy the frog, on the tube, you see tests where it can fully charge at 13,4v, but it takes longer. I set to 13,8v with 13,4v in summer, purely because are so much more hrs of sun in the day, and it’s enough time to get charged, and I still have spare power for loads. By raising the voltage all you do is speed up the charging. But, if you charge to 14,4v constant voltage, you have to stop charge when tail reaches 0,05C. No absorb. When you charge with lower voltage, it takes longer, and you can continue till tail current drops to virtually 0.IMO, the comments about the charging being limited by the available solar harvesting I would say is wrong. If you look at the graph, the battery would seem to being charged by just about the same amount each day. That is unusual and would point to a charger being turned off as the limitation. The reason the SOC is dropping overall is the draw is greater than the amount the solar charger is being allowed to provide (due to the premature change to float mode with the too low absorption time).
We shall see now the CV time has been increased to 4Hrs is that is the case or not
There is more than one way to skin a cat, if you understand what you are doing. Also the bmv needs to be in sink with the charger settings. If you change the charger settings, you need to mirror in the bmv as well. Otherwise, it will never sync right the soc.
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Adaptive is wrong setting for lfp. What it does, when it wakes up, based on voltage at that time, it calculates how long to hold in absorb. Max is 8hrs. Since lfp voltage is different, it will wrongly calculate and think the battery it’s full. Then it will work a minimum absorb time.
What is your battery capacity? The tail is based on your capacity.
Thanks for that. 100ah
Set 14,4v, no absorb time and tail to 1% or one amp. If you set tail bigger, and not enough solar, (less than the tail), it will think it’s done and stop charge to soon. This is the very reason victron canceled tail, you get a cloud, current drops under the value set, and stops before its done. Work around that, they set 2hrs absorb but at 14,2v not 14,4v. The bmv setting are dependable on charger settings.
If you not comfortable with this settings, just set victron preset for lfp.
If you not comfortable with this settings, just set victron preset for lfp.
Thanks again Raul, sorry, but as the absorption is now effectively disabled, should it be the float that is 14.4?
No the 14,4v it’s the absorption voltage, but since the absorption time is disabled, it will not spend time in absorb. It will stay there until tail current falls below the set value. If it’s full , it will quickly drop in float, as current tapers off. If it’s not full, it won’t even get to 14,4v.
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- May 16, 2021
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That's ok. We can disagree
Okay..... Have left it for a few days on the new settings. What it does now is hit 14.4v and the immediately drop down to 13.8v and stay at that voltage until the sun stops. That in itself makes sense based on the settings. There is certainly more solar available than it needs (most days....).
What doesn't make sense is the original query I posted. The SOC does NOT hit 100%. It gradually reduces every day. I even put the mains hook-up on to see if that would "force it" to 100%, but if does the same as solar, just keeps it held at 14.4v for longer.
So, I think, everything is working properly, but cannot work out why the SOC max is reducing day by day. The BMV settings are below. Does the Charge efficiency factor cause this?
Any ideas welcome.
Thanks
What doesn't make sense is the original query I posted. The SOC does NOT hit 100%. It gradually reduces every day. I even put the mains hook-up on to see if that would "force it" to 100%, but if does the same as solar, just keeps it held at 14.4v for longer.
So, I think, everything is working properly, but cannot work out why the SOC max is reducing day by day. The BMV settings are below. Does the Charge efficiency factor cause this?
Any ideas welcome.
Thanks
In the bmv you have detection time 3m and the charger 0 absorb but selected fixed. It will not sink.
As you have the settings in the bmv, on the charger you need a absorb value greater than 3m detection time.
Since you have a tail current set, you can have a fixed defined time absorb. The tail will cut it short if needed.
Set absorb on charger greater than your detection time on bmv, and it will sink to 100% soc.
As you have the settings in the bmv, on the charger you need a absorb value greater than 3m detection time.
Since you have a tail current set, you can have a fixed defined time absorb. The tail will cut it short if needed.
Set absorb on charger greater than your detection time on bmv, and it will sink to 100% soc.
Yes
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Have you synchronised since changing the settings. If you leave the mains charger on 14.4V then when the Amps drop off the battery is full, this is when you need to synchronise. That should then accurately set the 100% charge level. You may also need to set the BMV current threshold a little higher if the charging devices are cutting back to 13.8V before the monitor detects the tail current has fallen to the preset level then it will not auto sync. The monitor needs to synchronise every time the battery is full, otherwise the the readings drift further and further off target.
Thanks Raul. It is slowly starting to make sense. I have now set the charger to fixed of 30m.
I am 99% sure I did....
I have made the changes as above, so will see if that makes a difference. If not will increase the BMV threshold, fully charge on mains, set SOC and then see. Thanks Pausim. Every day is a school day....
Big Tail current it only works with even rate from ehu. On solar, at first cloud, tail falls because a drop in sun, and charger thinks it’s done, and cuts short.
This is the reason victron done away with tail current on their solar charge controllers, on lifepo4 presets.
A small tail will work as long as the sun output is greater than the tail current value.
This is the reason victron done away with tail current on their solar charge controllers, on lifepo4 presets.
A small tail will work as long as the sun output is greater than the tail current value.
If you increase the current threshold, it will drop in float even quicker, the aim is to hold constant current long enough to get to 99-100%, ( but not longer than necessary), and stop. Increasing tail works on high fixed charge rate, and 14,6v. You stop at a tail of 0,05C, but charge rate needs to be min 0,2C and fairly constant source, like EHU.
On solar is different, you can’t have a reliable charge rate.
The settings on the BMV will have no effect on the charging devices but do affect the automatic synchronisation needed by the monitor to keep track of the SOC. When the charging devices drop to float is down to their settings which are independent of the BMV and each other.
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You right, my mistake I was talking about the charger not the bmv.
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