Hello,
We have installed many Quattros but usually with batteries we are familar with and have had no issues. We recently installed a 24/5000/120 Quattro on a boat with very recently installed by owner 10 x 130Ah Giant Brand 12 volt lithiums in series parallel to provide 5 x 24 volt series strings giving 650 Ah at 24 volts.
We normally set the absorption voltage at 29.2 volts with float at 27.2 volt for the Batteries we sell. We set lithium mode and configure Smartshunt accordingly.
On this installation, we checked battery recommendation. Sticker on battery says "Bulk charge 14.4 - 14.7 volts." "Float charge 13.6 - 13.8 volts." On that basis we thought 2 x 14.7 volt = 29.4 volts so our setting of 29.2 volts should be ok.
Soon after installation with these parameters the Quattro would shut itself off and then spontaneously restart. Occasionally the Quattro would provide a "DC Ripple" warning.
A DC Ripple warning denotes 100 hz AC on the DC buss resulting from slightly high resistance supply cables to the Quattro. This would surely normally be in sympathy with high DC load such when the Quattro is inverting and supplying a heavy AC load. In our case this was not so. The "DC Ripple" warning appeared with no easily observable correlation with High DC current. Exhaustive checks were made to ensure that the DC cabling to the Quattro was VERY low resistance in keeping with the conventional wisdom of resolving DC Ripple warnings..
We enlisted help from our Australian Victron supplier who logged onto the VRM and very helpfully noted an unusually high variation on the Battery and Quattro DC voltages. With very little current variation quite radical voltage variations were apparent. It was about 1.5 volts of variation versus a "normal" at rest system that may exhibit say 100mV of variation.
We tested the Quattro on an AGM engine start bank on the boat and proved the Quattro was stable when using "normal" batteries.
We then investigated the "Daly 100 amp BMS" that was individually installed within each battery. It has an overvoltage sense at 3.75volt per cell. Four cell per battery gives us an overall battery voltage of 15 volts if they are all balanced before overvoltage sensing starts disconnecting cells or the battery.
12 volt batteries in parallel may not be a problem but two in series may allow one battery or the other on many strings to be slightly out of balance enough to cause havoc. No load balancing between batteries is employed.
We reduced the Absoption voltage to 27.6 volts and the Float voltage to 27.0 volts. We reduced the bank from 10 batteries to 6 just for testing and reduced charge current to 40 amps instead of the original 120 amps.
It has now run for two days without incident. Next week we will bring the other 4 batteries back into the bank and set the charge current higher. Hopefully the issue is resolved.
As I write this note it all seems very logical and easy to resolve but I confess it has taken some effort to get here.
I make the following observations that may or may not be correct. I would be appreciative of any comments to support or debunk the following theory.
These batteries in series/parallel reacted very strangely and caused a DC Ripple warning that was clearly not really DC Ripple. It also caused the Quattro to simply stop working (Turned off) and then restart and on two occasions the Quattro entered a "Fault" state and did not spontaneously turn back on. It looked very much like we may have had a Quattro fault as the previous Magnasine inverter charger did not have this problem.
It seems to me the following may help others who may experience similar.
1. Battery BMS systems can cause variations in terminal voltage that the Quattro reports as "DC Ripple". It may be a variation in terminal voltage but it is not "DC Ripple" if DC Ripple is defined as an AC waveform in sympathy with the AC output of the inverter. The DC Ripple warning in this case does not correlate with high DC current. In this case the DC Ripple warning has nothing to do with the integrity of the battery cabling.
2. The BMS induced voltage variation can cause the Quattro to simply stop with no error warning. It restarts and the cycle begins again. It would be wonderful to have a Error log saying why the Quattro turned off.
3. Occasionally the BMS induced problem causes the Quattro to shut down with a fault condition. Once again it would be nice to have an error warning relating to the fault condition.
4. Lowering the Absorption voltage allows the BMS to remain dormant and not cause terminal voltage variations. I hope this has resolved the issue.
5. I imagine problem is increased when creating 24 volts from 2 x 12 volt batteries in series. We don't typically do that but the client had already installed the bank.
6. It may be useful for Victron software to bandpass limit the DC Ripple parameter so real "DC ripple" can be separated from "DC variation". DC variation may become more common with the greater use of cheap BMS controlled Lithium batteries.
7. This problem would be EXTREMELY difficult to diagnose without VRM.
Maybe this may help someone. Any comments most welcome.
Trevor
