I don't think this is correct. Victron's recommendation is to set the "charge voltage" 0.2-0.3V less than the absorption voltage. It is how I have ours configured.
Mark
How to stop false 100% battery status
- Thread starter Elysium_Van_Isl
- Start date
Mark
I was going by section 5.7.1 of the manual at https://www.victronenergy.com/upload/documents/SmartShunt/9172-Manual_BMV_and_SmartShunt-pdf-en.pdf, saying it should be the float voltage. Section 4.3.2 of the same manual says to set it to 13.2V. Mine is set to 13.1 and works fine.
Looking at the algorithm it seems like the important things are that it’s not so low that the battery reads as “charged” when there is no charging source at all, and that it’s not so high that the charger doesn’t get there when absorbing. That suggests that anything around the float voltage to a bit less that absorption should be fine. The tail current is probably the more important part of the trigger.
Notwithstanding all the foregoing if you want your batteries to live long and prosper you need to
1 Make sure that they get fully charged and not left in a partial state of charge (PSOC)
2 Make sure the water does not get low. Check them regularly and develop a sense for what is needed.
Those flooded Trojans are robust. Mine are in their 7th year including 5 years of live aboard with solar power, and when they die I will almost certainly replace with like and go sailing.
1 Make sure that they get fully charged and not left in a partial state of charge (PSOC)
2 Make sure the water does not get low. Check them regularly and develop a sense for what is needed.
Those flooded Trojans are robust. Mine are in their 7th year including 5 years of live aboard with solar power, and when they die I will almost certainly replace with like and go sailing.
Those batts are not 91% efficient more like 80%. Peukert is closer to 1.3..
Making Your Battery Monitor More Accurate - Marine How To
Program The Ah Capacity This article features the older Victron BMV-602. The 602 has been replaced by the BMV-7oo series (700, 702 & 712). Everything in this article is still relevant to the current series of BMV-7xx battery monitors. WARNING: This article
marinehowto.com
Setting the “Charged voltage“ based on float voltage causes many systems to falsely synchronize early. I believe this recommendation by Victron is based on the assumption of a shore based charging system. They do address this issue in the troubleshooting section of the manual.
“10.3.11. Synchronisation issues
…
It is also possible that the battery monitor synchronises too early. This can happen in solar systems or in systems that have fluctuating charge currents. If this is the case change the following settings:
- Increase the “charged voltage" to slightly below the absorption charge voltage. For example: 14.2V in case of 14.4V absorption voltage (for a 12V battery).
- Increase the “charged detection time” and/or decrease the "tail current" to prevent an early reset due to passing clouds.”
Follow the FB groups for Solar on a Boat, or Lithium Batteries on a Boat, or the Victron Energy Users and you will see nearly weekly posts of someone complaining that their batteries are dead in the morning but the BMV/SmartShunt was showing 100% at sunset.
Good point. Given where the OP’s float and absorption voltages are and the fact he has solar, increasing the charged voltage could be a good step.
Thank you all! Doing some more reading on this.... great thoughts and very appreciated.
RC - I've gone over pretty much everything you put out there... trying my best to follow it despite my limitations!! lol
Yes, that works, but it’s the “old school” way because it only works for “old school” types of consumption. Run a fridge and a few other constant consumers, plus solar charging, and you don’t have time to let everything rest for 3 hours waiting to get a voltage reading.
This will tell you the state of charge, but it doesn't tell you any thing about capacity. A LA battery near death can still look "good" based on voltage alone.
Set charge efficiency to 80%. Set charged voltage to 14.4V.. If they are Kirkland they are JCI batts. If Interstate they are made by Trojan for Interstate..
I may be old and may have some quirks, but worrying about recharging batteries 1-3% to get them to Full is not one of them. Anything over 90% is good to me. My monitoring system is a voltmeter and experience in reading and interpreting the measurements. I do pay attention to having uninterrupted power to meet my needs and regularly receive a battery life of 5+ years on the average. Batteries are sold with a warranty because not even the manufacturers can control their quality or predict a single unit longevity.
Very True, I periodically use a cheap automotive load tester to test for the health of each individual battery. I actually rate them from the best to the worst to monitor their degrading progress. Yes I have had a couple of batteries go bad on me over the years, but they are easily identified and removed from the bank until a replacement is procured. If it is a single battery that went bad, I will just replace it, but if 2 or more are found weak I will replace the whole bank. I am aware that the new battery will degrade down to whatever level the bank rules but if the bank is in fairly good condition it makes economic sense to sacrifice a small portion of a new single battery.
Sure, but resting in a partial state of charge with lead acid batteries increases sulfation and causes capacity loss. A good battery monitor, correctly programmed, can help confirm you are indeed reaching 100%… especially if there is data logging. Also, it’s possible you could notice a loss of capacity if the voltage doesn’t agree with the SOC in certain circumstances.
Guessing at batt capacity is like throwing darts blindfolded. It will make any level of accuracy difficult.
Charge Efficiency 80%
Charged Voltage 14.7V
Peukert 1.35
Charged detection time 5 min
Tail Current 1.5% of Ah Capacity
This article will walk you through the nuances.
Making Your Battery Monitor More Accurate