New Multiplus Goes Crazy in Absorption With New LiFePO4 Battery

DIY
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1

Hi All,

I’ve owned a number of Multiplus 12/3000/120 inverter/chargers since 2003 and have a lot of experience using them with regular flooded and AGM batteries. I even worked with Victron back in 2004 to help them test and debug the Multiplus PowerAssist function to work with the Honda EU-2000 which ended up working great and Victron subsequently advertised it extensively. However, I recently encountered a very strange problem with a Multiplus after upgrading my Lagoon catamaran from 840AH of worn-out Lifeline AGMs to a single 460AH Li Time LiFePO4 battery (I did the original install 10 years ago).

This was my first experience with LiFePO4 so there was a learning curve. The upgrade required a number of changes, including two new Renogy DC-DC chargers, a Victron BlueSolar100/50 charge controller, and a lot of rewiring. The Renogy and BlueSolar chargers worked perfectly all the way to float so I figured a few minutes with VE Configure changing to LiFePO4 and Li Time’s recommended settings would have my 10-year-old Multiplus also working fine but that was not the case.

The bulk phase worked well but only charged at 75-80 amps instead of the specified 92 amps (.2C). However, the moment it reached absorption voltage, it went “crazy”. Instead of holding constant voltage with current gradually reducing to tail current (9.2 amps) as expected, the voltage varied dramatically – spiking to the high 14 volt range and then dropping into the 13s over about 5 minutes. The current was even more bizarre – quickly dropping to zero amps, slowly climbing back to 55-60 amps, and then quickly back to zero in the same 5-minute cycle. Both patterns repeated indefinitely and the unit never reached float. I wondered if Li Time’s recommended absorption voltage (14.6 volts) was too high and causing a BMS disconnect so I changed to Victron’s default LI absorption voltage (14.2 volts) but that made no difference. So I finally came to the conclusion that my old Multiplus was too old to work with LiFePO4 and I needed an upgrade.

When I looked into buying my fourth Multiplus, I discovered that Inverters-R-Us sold them through Amazon for the same price as everybody else plus their “experts” would pre-configure it and provide “expert” technical support so I ordered from them. Fast forward a week and the new Multiplus was installed and operational. Unfortunately, it displays the EXACT same symptoms in absorption as my older Multiplus! I called Inverters-R-Us’ “expert” tech support and soon found they knew less about the Multiplus than I do. After carefully preserving their “expert” settings file, I reviewed the VE Configure options and found there are very few changes in the last ten years. The only change I made was to accept Victron’s default LiFePO4 voltages. I installed a VE.Bus Smart Dongle to see if I could get any insight from Victron Connect but learned nothing new. I also verified that the Multiplus has the current firmware version. At this point, I’m stumped!

The Li Time 460AH battery works GREAT and has more usable capacity than my previous 840AH of Lifeline AGMs did when they were new. As I said before, the other chargers, including the Victron BlueSolar, work perfectly - only the Multiplus has issues. Has anybody else experienced and, hopefuly, resolved these symptoms with a Multiplus working with LiFePO4? If so, I would GREATLY appreciate any help you can provide!

Thanks!
Glen

2

Does the battery have Bluetooth and an app to look what the battery is doing?

My guess is that the battery is disconnecting due to a high cell voltage.

Try to reduce the charging current to give the BMS time to balance the cells.

14.6V is pretty high, I would also recommend to set that to 14.2V

1 Like
3

Hi Mathias,

Unfortunately, the battery doesn’t have Bluetooth capability.

Regarding your suggestions, I completely agree with you! In fact, I said in my post that "
I wondered if Li Time’s recommended absorption voltage (14.6 volts) was too high and causing a BMS disconnect so I changed to Victron’s default LI absorption voltage (14.2 volts) but that made no difference. "

I’m not aware of any way to control charge current in the absorption phase.

The symptoms I’m experiencing are baffling! What am I missing?

Thanks,
Glen

4

If you have a GX device you can reduce the charging current with DVCC.
If not you have to reduce the current in the settings of the MultiPlus with VE.config.

5

I don’t have a GX device. I know Victron has a lot of cool new stuff but I only have what I stated in my original post.

The only current setting I’m aware of in VE Configure is bulk charge current which is set at the battery manufacturer’s recommended 0.2C (92 amps). I have no problem with bulk.

By definition, the absorption phase is constant voltage which is set at the default 14.2V and current should slowly decline - but that’s not what I’m seeing. What am I missing?

6

Probably the battery being new is still a little unbalanced.
Try for a while a smaller voltage, e.g. 14V (3.5V per cell) or even less, 13.8V (3.45V per cell).
Choose the voltage that will not generate those symptoms.
Set the desired voltage for all voltages: bulk, absorption, float.
In this way you’ll prevent some cells to hit the overvoltage trigger and allow the BMS to balance the cells.

1 Like
7

Reduce that current to less than 0.1C and charge the battery slowly to give the BMS time to balance the cells.

Going into absorption can be a side effect of the battery blocking the charging current during bulk.

1 Like
8

As long as the voltage is left to a higher value, a 46A (0.1C) or even 20-30A current is more than enough for the “happy” cells to overshot, because balancing is done with less than 2A. It’s an overvoltage, not an overcurrent, trigger.
And once the (lower) voltage limit will be hit, the current will fall anyway.
Remember, Victron recommended in DVCC to limit the charging voltage, not charging current, for reducing HV alarms… :wink:

Or even better, reduce both current - for slow charging - and voltage - for avoiding HV charging disconnects.

9

Hi Alex,

That’s an excellent suggestion and worth trying. Recall this a 460AH battery and it technically isn’t new anymore as this problem first came up several months ago. I’ve been successfully charging it with solar and the DC-DC chargers so wouldn’t the cells be balanced by now? I need to get the Multiplus working for when I need a faster charge rate and I only recently discovered this forum.

Thanks,
Glen

10

I have just purchased a 24v 3kw Multiplus to replace a 24/1200 Phoenix.

The Multiplus works great, EXCEPT it does not measure the DC voltage correctly, (documented after the system description below.) I also have a 100/30 MPPT and a 500 amp Victron shunt. Voltage / frequency checks are with a Fluke 87 V.

I had originally purchased the 24v 1.2wk Phoenix, based on what I had calculated, (and had measured,) which was about 750 watts constant, with head room for compressor starts and what not.

Battery set up is ‘24v’ 9.6kWh made up of 8 100ah WattCycle LiFePo mini format batteries, WITH Bluetooth so I can monitor the individual batteries.

The purpose of the setup is to run my wife’s medical gear overnight if we get a power outage without having to run a gen set constantly. (Gen is a Honda EU7000i)

I decided I might as well pick up the fridge, freezer and a few LED lights as well. Measured and calculated power budget looked ok for a 1kw inverter to handle, along with compressor starts.

If the outage is extended, run the gen set during the day to recharge the batteries and provide power for the microwave, air fryer, etc.

I decided to basically make it so that the inverter plugs into the gen tran panel in place of the generator for the overnight run.

It initially worked pretty well, BUT, (yeah, here it comes,) it was only after running it for a test run of about 5 hours, it kept over loading. Found out my power budget didn’t know about the DEFROST cycle of the freezer pulling 250 watts, (running is only about 80,) and a few other surprises that didn’t show up until things went through a run cycle or two. Nuts. Plenty of stored kWh, just not enough inverter.

Ok, ok, quit messing around and buy what I should have in the first place…

Since the Multiplus has a UPS mode and more than enough capacity to run the house/medical loads, plus the microwave, or the air fryer, toaster oven INDIVIDUALLY, I’ve rethought it all and decided to run the EU7000i in 120v ONLY mode and supply the inverter with a 30 amp circuit from the house, AND I have a separate 120v 30amp cable that is run in from the generator. House keeps it all up and charged until a power failure, and will recharge it all if power returns before the roughly 12 hour run time of the battery bank. If I need to use the generator, I just have to swap the input connection to the Multiplus. I also have a separate individual 35 amp 24vdc power supply that can be plugged into one of the remaining outlets on the generator to make use of the full 5.5 kw output. (Or a second generator if I were to need to.)

When I put the Multplus through it’s paces, the batteries internal BMS kept kicking out on over voltage when I set the charger to LiFePo AND to the exact same voltages for Absorb and Float as in the MPPT controller.

I finally put the Fluke on the DC terminals of the Multiplus and it was reading 0.4v HIGH as compared to what the Multiplus was indicating on Victron Connect! The MPPT, the shunt and the fluke meter all agree within a few hundredths of a volt.

Ok, temporarily offset the charger voltage down by 0.4 v to see if that helps.

This is the odd part, as the batteries come up to full charge, the MPPT, shunt and Fluke all indicate an OVERSHOOT of the 0.4v plus the set point that the voltage was set at on the Multiplus.

IE: I set the Multiplus to 27.5v, and when static, (no charge or discharge,) the error is the 0.4v.

However, when it’s charging, the voltage overshoots the 27.5v set point by at least 0.3 volts! (The shunt, MPPT and meter are all measuring 27.9v, but when the charger overshoots, it pushes the actual voltage on the battery bank up to 28.3!

That is enough to cause a few of the batteries to go up over the 14.4 volt charge disconnect point of the internal BMS.

Put in a trouble ticket, and the dealer wants me to exchange the unit. I’ve told them to unbox the replacement and put it on a power supply FIRST to see if the replacement exhibits the measured voltage error or not that mine does before I rip my system apart.

I’ve made a bit of a big deal about this because all of the OTHER Victron gear is dead nuts on, and I don’t want a piece of gear being off as compared to everything else in the system.

We’ll see what happens.

Steve

11

I have a 12V ESS system that I have setup to support my 48V ESS system. I have 1050AH of battery capacity. They consist of 2 battery boxes 340AH, 320AH, my trolling motor battery, winch and AUX battery and 50AH battery for my fridge. ALL are connected by Anderson plugs to a Victron power in. I don’t use a shunt and do everything based on voltage and use the multiplus for SOC. I take these batteries out of the system when I go camping or boating. I figure these are going to die from calendar aging before they die from the stated 8000 cycles so I may as well use them. I have had problems similar to those described in some of these posts. I have 2 100/30 and one 100/50 and also use the internal charger which is 50amps. I have this node-red flow to reduce the charge current when the charge controller reads 13.6 - 14.2 and scale back the charge to 0.

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var now = new Date();

// Use local time
var localTime = new Date(now.getTime());

// Get the current local hour and minute
var currentHour = localTime.getHours();
var currentMinute = localTime.getMinutes();

// Define the start and end times (in hours and minutes)
var startTime = { hour: 7, minute: 30 }; // 9:30 AM
var endTime = { hour: 16, minute: 59 }; // 4:01 PM

// Convert start and end times to total minutes for easier comparison
var startTotalMinutes = startTime.hour * 60 + startTime.minute;
var endTotalMinutes = endTime.hour * 60 + endTime.minute;
var currentTotalMinutes = currentHour * 60 + currentMinute;

// Check if the current time is within the allowed range and if the input is a number
if (
currentTotalMinutes >= startTotalMinutes &&
currentTotalMinutes < endTotalMinutes &&
typeof msg.payload === ‘number’
) {
// Get the battery SOC value from global context
var batterySOC = global.get(‘SOC’) || 0;

// Check if battery SOC is greater than 99%
if (batterySOC > 99) {
    // Battery SOC is greater than 99%, send 0
    msg.payload = 0;
    return msg;
} else {
    // Battery SOC is not greater than 99%, let the message pass-through
    return msg;
}

}

// Input is not a number, battery SOC is outside the allowed range, or current time is outside the allowed range, do not let the message pass
return null;