Hello,
this new 100/30 is set to "User defined" battery profile with 13.9V absorption for 1 minute and 13.4 V float (equalization not used but set to 14.0V) however every morning it brings the LFP batts from around 13.0V o 13.1V to 13.4V but never tries to get them to 13.9V as can be seen on the graph.
I read in a different post here that it needs a minimum drop of 0.1V for LFP before it rises to absorption. What is the required drop for this "user defined" profile then?
I’m no expert but maybe the Absorbtion Stage is not long enough. I think I’ve read on this community that absorbtion should be set to 30 minutes and you have it set to 1 minute.
But as I say, I’m no expert.
Thanks Steve, it was deliberately set to 1 minute to effectively turn the absorption phase off, since you don't want that with LFP batts.
I’ve misunderstood your question; i thought you were trying to get the MPPT to push absorbtion voltage :)
Hi, try increasing absorption time; and, measure at the mppt terminals. And check what the mppt itself is measuring; and what state it is in.
I really cant see a reason for it to go from bulk (which normally ends once the voltage has risen to absorption voltage) before it has done so.
I’m not sure what the 0.1V drop is referring to.
Lastly: check temperature compensation.
Thanks for the reply, the graph shows the voltage and current directly at the output of the MPPT terminals as that's where the producer controller is situated. That controller then send the data back to the database and web server.
I can try to increase the absorption time to see if it makes any difference, but if it does, it sounds like there is bug in the firmware, doesn't it?
I haven't touched the compensation setting, but will check that, too.
The 0.1V drop I mentioned was referred to in another thread: It suggests that the bus voltage has to drop by some value first before the MPPT changes from float to bulk mode. Can you confirm that?
Say the batts get fully charged by 11AM, MPPT goes to float, then comes a big load which draws the batts down to, say, 70% SOC by 1PM. At some stage, the MPPT should decide to go back in bulk mode rather than just trying to hold the float voltage, correct?
Hi; no I don’t think there is a bug.
Forget about that 0.1V; I dont know what it is; but know for sure that its not related.
The unit switches from bulk to absorption once voltage has rised to absorption voltage. There are no other conditions.
Unit switches from float to bulk on voltage as well. Search the documentation to find the threshold. Either mppt victronconnect manual or the mppt manual itself.
The unit switches from bulk to absorption once voltage has rised to absorption voltage. There are no other conditions.
That's how I understood it, too. But I'm only an EE, so what do I know?
Search the documentation to find the threshold. Either mppt victronconnect manual or the mppt manual itself.
I did go through all the doco I could find online, more than once: The manual for the MPPT (Manual-BlueSolar-charge-controller-MPPT-75-10-75-15--100-15-EN-NL-FR-DE-ES-SE-ul) the VE.Direct-Protocol-3.25.pdf, the Victron-Blue-Solar-Charge-Controller-MPPT-75-10,-75-15-&-MPPT-100-15-EN and the Whitepaper-Data-communication-with-Victron-Energy-products_EN but no luck.
Where is the "MPPT manual" itself on the web site?
Only after I couldn't find the info in any doco I looked here in the forum and it seems only one guy had the same question.
Either way, I'll change absorp time today and test again.
Thanks for your help.
Hi; with regards to your question about when the device switches from float to bulk; this is what I found in the mppt manual:
“When the battery voltage drops below float voltage during at least 1 minute a new charge cycle will be triggered.”
It needs to drop 100mV below.
You say "the graph shows the voltage and current directly at the output of the MPPT terminals ". Does your measuring equipment connect to the actual terminals of MPPT 100/30? And how do you measure the current coming from the 100/30?
I would suggest the following:
Yes, will try another measurement today.
The voltage is measured both, directly at the MPPT by the producer controller and directly at the batteries by the batt controller. It's a SharksHead.com BMS.
The current is measured via a calibrated shunt in the producer controller and then a separate shunt at every batt, so I can see which batt actually takes the charge.
Do you have the result from an increased absorption time? And it would be good to have the voltage and current again from the beginning of charge all the way through to the end of absorption time.
As mentioned, the MPPT never reached absorption voltage, hence those values don't exist. Now that I've set the profile to LFP it doesn't cut off the charge current anymore once it reaches float. That's float at 13.2V, it doesn't charge to absorb at 13.9 V.
Measured the MPPT output voltage today as 13.3V and the batt voltage at 13.2V, all confirming the numbers from the graph and all in line with the voltage on the Victron app. Also measured the output current with a UNI-T clamp meter and compared that with Victron app, it was the same. Compared the current with the sharkshead current and again, it was confirmed by 3 sources. Now I've changed the profile to LFP and I'm sure the voltage will rise tomorrow as expected.
Only I don't want to leave the LFPs on the LFP profile while I'm not living on the boat at the absorb and float voltage are too high for LFPs that are not in regular use.
