question

ben avatar image
ben asked

Why won't my Quattros deliver rated charging power?

Over the last year, I've had three different Quattros installed with my LiFePO4 off grid system:

Quattro 48/15000/200,

Quattro 48/3000/35 120V,

and just today, a new Quattro 48/5000/70 120V.


I can make none of these Quattros charge my battery at their rated values (200A, 35A, 70A respectively).

The new Quattro 48/5000/70 120V is the latest example of this. When it is started up, cold, it ramps from 0A to 61A, but it will never attempt any higher. Shore current limit is set to 50A, and this is a 53.5V battery that is being charged, so there should be 50A * 120V / 53.5V = 112A of shore capacity.

The battery in this case is well below the absorption threshold, and the Quattro is configured for maximum charge current (70A) in VEconfigure.

The ambient air temperature around the Quattro is roughly 10C today.

The delta between the Vsense pair and the charging cables is 0.20V at the peak 61A charging, so the stated 1.0V maximum delta is not being reached. (Calculated cable resistance is 5mOhm.)

It even takes the Quattro a few minutes before the fan spins up to cool the unit. At no point will it attempt its rated value.


I observe a slightly different, but similar, phenomenon with my 15KVA unit. That unit is rated to 200A, and when it is cold and enters bulk charging, it will begin at 190A for about four minutes. It then drops suddenly and in a characteristic curve to a stable charging current of roughly 150A, which is only 75% of its rated value. A sample graph of the charging current is here:


In summary: my units don't deliver their rated charge under any normal conditions, and I can't figure out why. Is this simply what we should expect in terms of performance from these units? Should I consider returning the Quattro 48/5000 120V since it will seemingly never even attempt to charge at 70A?

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4 Answers
Johannes Boonstra (Victron Energy Staff) avatar image
Johannes Boonstra (Victron Energy Staff) answered ·

Hi Ben,

For your information, the charger is limited by a few things, and not only the AC input limit. This AC input level is by the way not exactly how you calculated this as there is a margin used the of about 80% of the A setting. So when set at 50A it actually is targeting at around 40A. Beside this there is an efficiency factor which is in charge also 0,85. So not that it will change much in your situation but at a 50A setting the actual energy which is going to be used for charging (when there is NO ACoutput current at all) is 120x40x0,85 = 4080Watt/53,5Vdc=76A maximal.

Beside this the ACinput voltage plays a role, when this enteres the AClow connect level the charger is limited the charger is reduced.

Also the DCripple limits the charger (when above 0,8V also the charger is reduced). ANd of course the temperature in the unit, so the unit needs a high airflow (no blocked airintake/outlet due to installing to tight to wall/otherproducts ect.)

Weak AC setting, (make sure this is de-selected) This will reduce the charge power as the charger will use only a part of the sinewave. (maximal power is then around 70% of Inominal)




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ben avatar image ben ♦ commented ·

Thank you for these suggestions. I am afraid none of the ones you have mentioned would apply in the cases I am observing. Let me go one by one through each:

This AC input level is by the way not exactly how you calculated this as there is a margin used the of about 80% of the A setting. So when set at 50A it actually is targeting at around 40A.

I do not observe this in my tests. When I set shore current limit to 20A, the unit moves to within 1A of that limit. When I change it to 30A, it moves up to 30A. This is in Charger Only mode. I do see it being more conservative when in PowerAssist when inverting. But I am having this problem in Charger Only.

And, anyway, I can set the unit to 80A input and it still won't reach the rated charge current. So this is not the problem.

Beside this there is an efficiency factor which is in charge also 0,85. So not that it will change much in your situation but at a 50A setting the actual energy which is going to be used for charging (when there is NO ACoutput current at all) is 120x40x0,85 = 4080Watt/53,5Vdc=76A maximal.

Yes, I understand that efficiency is at play. But, as you note, this is not what is causing my units not to reach their rated charge.

Beside this the ACinput voltage plays a role, when this enteres the AClow connect level the charger is limited the charger is reduced.

My input is not sagging or coming close to the AClow level. It is stable at 122V (or 240V, for the 15kVA scenario).

Also the DCripple limits the charger (when above 0,8V also the charger is reduced).

I am seeing essentially 0 DC ripple while simply charging this battery. I do not think this is a factor.

(cont'd)

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ben avatar image ben ♦ commented ·

ANd of course the temperature in the unit, so the unit needs a high airflow (no blocked airintake/outlet due to installing to tight to wall/otherproducts ect.)

This is what I originally thought was the problem, but I am seeing this issue when the units are very cold and just as they start up. The behavior is different between the units: 15kVA does what you see in the graph above, actually reaching the rated current for a while and then giving up. The 5kVA unit never even attempts the rated current!

Weak AC setting, (make sure this is de-selected) This will reduce the charge power as the charger will use only a part of the sinewave. (maximal power is then around 70% of Inominal)

This is deselected in all of my units.


So, to be clear: I still do not know why none of my Victron Quattros are meeting their rated values.

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Alexandra avatar image Alexandra ♦ ben ♦ commented ·

@ben is it possible the batteries are limiting the input current?

Some battery management systems do this also with dvcc checked.

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ben avatar image ben ♦ Alexandra ♦ commented ·

Good idea, @Alexandra. Unfortunately, I don't have DVCC or a BMS commanding current limits. It's just a raw battery from the point of view of the Quattros.

And, I still have no idea why they don't operate to spec.

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ejrossouw avatar image
ejrossouw answered ·

@ben What is the LiFePO4 and BMS specification? Could the bms limit the charge current the battery receives?

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ben avatar image ben ♦ commented ·

There is no BMS in the circuit to apply any limiting. Just a 52V LiFePO4 array with wiring designed for 300A continuous.

I can charge it at close to 300A if I put both of the Quattros and my solar chargers on all at the same time.

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Paul B avatar image
Paul B answered ·

Hi Ben this is one of my sites it has 3 x multiplus 48/5000-70 units and it holds 210amps (well close enough) until it warms up and the temp is always starting at 30 Deg C.

these units are running off a Generator/ Grid Tie inverters during the days, I was only getting 150 out of them and I added extra Fans under them to get more air flow and this bumped them up quite a bit.

Now in your case you are way lower in temp so you may even get more than there max output.


Have you considered Power Factor as a possible cause for the lower output, maybe some Caps to bring it back into alignment ????


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twistedtree avatar image
twistedtree answered ·

I don't see an answer from Victron on this. I see the same thing in the Quattro 24/8000 installations that I have. They NEVER operate at rated output for more than a very brief time at startup. According to Victron's documentation, these should operate at rated output in a 25C ambient, which all mine are within. It don't see any of these products meeting specifications, or even coming close. The documented behavior suggests that there is inadequate internal heat dissipation to operate at the rated ambient temps.

What gives?

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