Victron Multiplus not giving full charging amps

[jr_spyder]

I’ve just done a conversion to LFP batteries and now out cruising for the first time living with them in the real world. The new system has 6 Battle Born (BB) GC2 100ah batteries and a Victron Multiplus 12/3000/120 inverter/charger. I already had Balmar alternators with MC614 regulators on my engine and genset. Everything is set to LFP and the battery specs defined by BB.

The main goal for me for going to LFP is to reduce charging time, and specifically generator time when on passages or living on the hook.

Right now I am disappointed in that I can’t seem to get the Multiplus to push anywhere near its 120amp charging capacity into the bank, at best I see 79 amps. I monitor everything with a Balmar SG200 Smart Gage.

This morning I’ve done a very careful experiment. Starting at 34% SOC and 12.9 volts on the house bank, and turning off all DC loads on the boat, I plugged into shore power (120 vac). The charger came up and built up to 79 amps but stopped there. It has stayed there for 20 minutes now. It shows that it is in bulk mode as it should, the battery volts show 13.4.

I really expected it to push its full 120 amps under these conditions. The setting are done with the computer app via a usb connection (not the dip switches) and they are all correct. The amp output is set to 120. I don’t see any other settings that would regulate the output.

My dealer hasn’t been much help and talking to their rep doesn’t give me much confidence that he actually went to Victron training. His explanation is that only when the batteries are very low will you get 120 amps. I’m not buying it.

Help!

Any other Multiplus users with better results? Experience?

Thanks.

[rslifkin]

What do you have the AC input amps limitation set to? And do you have any AC loads running through the Multiplus while charging? It could be throttling to avoid exceeding the AC amps setting on the input.

[Texlan]

13.4-12.9 = .5 volt difference.

What awg and how long are the cables between your battery and your multiplus? Voltage drop could be the limiting factor here. The charger may "see" 13.4v on the output but the batteries may only be seeing say, 13.2v.

(edit)
Not sure on the battle born BMS -- can they be and are they connected to the Victron equipment with DVCC turned on? in that case voltage measurement would come from the battery not the multiplus, specifically avoiding the potential voltage drop issue

[noelex 77]

The 120A charge current is specified for an ambient temperature of 75°F ( 24°C). Victron do not indicate the performance at higher temperatures, but the fact that they take the trouble to nominate this temperature limit only for the charging function suggests it may drop significantly at higher temperatures.

79A is a severe reduction and I would be surprised if this is due to temperature alone, unless the unit is located in a hot environment with poor ventilation, but it may at least be part of the answer.

[dksail]

What does the dock supplied AC voltage drop to while charging? If that is dropping below tolerable levels, the Victron unit might be throttling down.

[jr_spyder]

Originally Posted by rslifkin

What do you have the AC input amps limitation set to? And do you have any AC loads running through the Multiplus while charging? It could be throttling to avoid exceeding the AC amps setting on the input.

The limit is at its max 50 amps. My AC gages tell me I’m pulling 11 amps off the dock. I have no other loads, AC or DC, running.

[jr_spyder]

Originally Posted by Texlan

13.4-12.9 = .5 volt difference.

What awg and how long are the cables between your battery and your multiplus? Voltage drop could be the limiting factor here. The charger may "see" 13.4v on the output but the batteries may only be seeing say, 13.2v.

(edit)
Not sure on the battle born BMS -- can they be and are they connected to the Victron equipment with DVCC turned on? in that case voltage measurement would come from the battery not the multiplus, specifically avoiding the potential voltage drop issue

The cables are 4/0 and maybe 8-10’ from charger to bank. This shouldn’t be a problem, and my previous charger could push 120 amps with the same set up.

The BB batteries are drop-ins. There are no external BMS connections or controls.

[dksail]

Check to see what the voltage is from your dock supplied AC. You mentioned 120v, but what happens when you are charging? Does that drop below 110v? At 11 amps ac, you should be seeing something much closer to 100amps dc to the batteries.

[jr_spyder]

Originally Posted by noelex 77

The 120A charge current is specified for an ambient temperature of 75°F ( 24°C). Victron do not indicate the performance at higher temperatures, but the fact that they take the trouble to nominate this temperature limit only for the charging function suggests it may drop significantly at higher temperatures.

79A is a severe reduction and I would be surprised if this is due to temperature alone, unless the unit is located in a hot environment with poor ventilation, but it may at least be part of the answer.

I’m in cool New England and the locker is well ventilated. It certainly starts off cool but still pushes low amps. As it warms up it doesn’t change.

[jr_spyder]

[QUOTE=dksail;3644663]Check to see what the voltage is from your dock supplied AC. You mentioned 120v, but what happens when you are charging? Does that drop below 110v? At 11 amps ac, you should be seeing something much closer to 100amps dc to the batteries.[/

My dock supplied voltage doesn’t budge. I have a 50 amp connection, and I never see it drop even if running heavy AC loads. It’s solid.

[Texlan]

Originally Posted by jr_spyder

The cables are 4/0 and maybe 8-10’ from charger to bank. This shouldn’t be a problem, and my previous charger could push 120 amps with the same set up.

The BB batteries are drop-ins. There are no external BMS connections or controls.

For 20 feet of 4/0 wire at 79 amps, the voltage drop is about .1v.

The batteries are seeing .1v less than the charger is seeing. What voltage is the multiplus seeing on the output?

Also, echoing other comments here -- what AC Line voltage is the multiplus seeing on the input? There is always voltage drop over lengths of cable, whether that be your shore power or 4/0 battery cables. It's just a matter of magnitude. When charging from my quattro over a 50 foot shore power cable, i regularly see 10v drop. Sometimes the quattro will throttle as others say to charge @ only 900 watts, even though I can theoretically charge at almost 4000 watts, again, due to the voltage on the AC input.

If you don't have a Venus device (cerbo, color control gx, raspberry pi w/ Venus, etc) to get this information, you should be able to connect to the multiplus via VE config utility and a MK3-USB VE.Bus to USB interface to get some real time info that should shed some light on the situation.

[ItDepends]

Also, do not forget the Victron battery charger is a constant POWER device, not a constant CURRENT. The 120 Amp rating is at 12 Volts, so 120*12=1440 Watts.

The MAXIMUM current you should expect to see at 13.4V is 1440W/13.4V= 107A Not everything you think are missing, but half of it!

Be SURE to review all the settings. The default current limit for the charger is 80 Amps. Suspiciously close to your actual output. Did you deliberetly increase it to 120? Are you sure? If not...

[CharlieJ]

jr_spyder
I think you have a combination of problem causes:

Temperature related derating:
Victron provides the temperature derating curves at https://www.victronenergy.com/suppor...al-information. Scroll down to "Output rating, operating temperature and efficiency".
If your locker is >75F, then you are losing some of the charging current due to temperature.
A "cool" locker is not quantitative. Take a temperature reading inside the locker after the Multi has been working hard and consult the charts above.

Voltage drop in AC supply
Check the voltage at the MultiPlus AC input with a quality DMM. Panel meters are notoriously inaccurate.

Voltage drop in DC output
With the problems with the SG200 documented on this Forum, I would not trust it for diagnostics. So, using a quality DMM, take a DC voltage reading at the DC terminals inside the MultiPlus and at the battery B+/B- bus.

For those posters discussing interfacing with the BattleBorn batteries with CerboGX, Venus GX, etc. note that the BB batteries do not communicate any information outside of the battery case. They are fine batteries, but not for boats.

[CharlieJ]

...and one more thing...

Use a clamp meter and test the actual current being produced by the Multi by clamping B+ at the Multi.

[Zanshin]

How did you set the limit to your Victron? There are 2 methods - DIP switches inside the unit or via software. With software, there's the method using bluetooth and an app if you have the appropriate devices installed, or by attaching a MK3 adapter to the Victron itself and running the free software on a PC. The latter method gives you the most control and most information.
I just went through the same exercise on a Victron multiplus and by setting the max AC and by turning off the switch for 'wide current' the charge went to the expected maximum of around 120A derated by 10% for temperature.