I have a Multiplus Compact and smart lithium 230Ah setup. The multiplus enters floating mode when the smart lithium shows that voltage is only 13.37V, even though the charging config of the multiplus has floating voltage set at 13.5V.
The screenshots shows the voltage reading from the smart lithium itself and the multiplus charger config.
How should I investigate this and prevent the charger from prematurely entering float mode?
Thank you.
Check your cabling - any loose or dirty connection between the source (the MP, or the MPPT) will cause a voltage drop, and therefore the source will see a significantly higher voltage than the battery does in charge, and a significantly lower voltage under discharge.
Check your voltages from the charger to the battery - report back on what voltage the charger terminals are, what the breaker terminals are, what the busbar terminals are, what the battery terminals are. Basically test every exposed piece of metal. If any of these points are more then a few mV less than the previous one, investigate that connection. Some installers polish their lugs to make sure they get a super-low resistance connection.
What is that notification about (bottom right of your screenshot)
Here’s a fault I once found;
This is a typical lug (aka “Compression lug”, “crimped lug”), unfortunately i don’t have a pic of the faulty lug.
A lug like this had a metal spur or spike, probably caused by the manufacturing process where the curved nose of the lug was sheared off (close to where the “12” is stamped).
The spur meant that the lug was only contacting the busbar in 2 places; the spur, and the heel of the lug opposite the “12”. Most of the time the lug was cool and no fault developed, but at higher currents the lug got hot and the voltage drop meant that the inverter (a 12v 2000w) complained of low voltage.
The customer (not our customer) first spent weeks blaming and testing their panels and battery before calling us - this is understandable, the fault would look like the controller is not charging properly, or the battery is faulty.
After instructing the customer to do a check of the voltages between the controller and the battery, the biggest drop was found to be between the busbar and the inverter. At this point it can only be 4 things - the lug at the busbar, the cable, the lug at the inverter end, or the inverter itself.
The busbar lug was the issue.
The customer said the spur looked like a lump of galvanising slag, but as far as i know these lugs are tinned rather than galvanised, but either way, the bottom surface must be flat to make a good contact with its opposite surface.
The lug was filed and reinstalled, and the fault went away.
As i mentioned in the last post - some installers file, sand, or polish the contact face of the lugs.
Hi @pupu79
One of your pics shows the battery in ‘Imbalance’ state. Maybe give it some time to sort itself. I’m not familiar with the Victron bms’s, but if it really is at 100% SOC, then it won’t be pushing much current anyway, probably shut off…
Thank you for the advice. This is exactly the problem. I found a poor connection.
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