mtnscott avatar image

Voltage Spikes, System Failure, MultiPlus Absorption Transition During Charging LiFePO4

System Design:

I have 3 Lion Energy UT1300 LiFePO4 105Ah batteries. They each have an internal BMS and are the 'drop in' replacements for deep cycle Lead Acid batteries. They are rated for maximum 100A charge / 150A discharge each and are connected in parallel using 4/0 AWG cables. On the negative terminal I have 12" 4 AWG cable to a BMV 500A shunt and then 24" 4 AWG cable to a Lynx Shunt. On the positive side I have 24" 4 AWG between the battery bank and a BlueSea m6000 disconnect switch, then 12" 4 AWG from the switch to the Lynx Shunt. The Lynx Shunt is connected to a Lynx Distributor. Then I have a MultiPlus 12/3000/120 connected to the Lynx Distributor via (2) 36" 4 AWG cables and a 400A Mega Fuse. The Lynx Shunt has a 800A CNN fuse. The MultiPlus has the voltage sense connected using a fused 20 AWG wire to the battery terminals. I know the 4 AWG wiring is not ideal, I will replace with larger wire in my final installation, I don't know if it is the source of my issue. Here is a crude wiring diagram


I can discharge the batteries fine, the problem occurs during charging. When the MultiPlus transitions from Bulk to Absorption problems occur. They range from interrupted charging (Absorption voltage set to 13.9 - 14.1) to complete shutdown of the MultiPlus (Absorption voltage set to 14.4 - 14.6).

Here is a picture of the PV during charging showing the transition between bulk and absorption. The absorption voltage is set to 13.9, the unit seems to stop charging after the transition to absorption.

Here is the picture of PV when the MultiPlus absorption voltage is set to 14.4 Volts. The drops during the absorption mode represent when the MultiPlus shuts down and then resets itself. During the shutdown all lights are off and AC1 is off. NOTE: The voltage spikes seem to follow the current peaks. The MultiPlus will continue this interrupt cycle indefinitely until I intervene.


1. Has anyone else seen this behavior?

2. Could this be caused by the BMS shutting down during charging?

3. Could this be caused by using 4 AWG cable?

4. Could the MultiPlus design be causing the voltage spike?

5. What would a normal PV chart look like during absorption mode? I have read absorption mode is a constant voltage with reducing current until charging is complete.

Thanks in advance for any help.

MultiPlus Quattro Inverter Chargerbattery charging
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1 comment
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Im a little late on this one but thought I would pass on what I got from Lion. Victron Multiplus settings for Lion UT1300.pdf

4 Answers
mtnscott avatar image
mtnscott answered ·


1. I used the wrong term 'PV' these pictures are actually current & voltage.

2. My wiring diagram had a mistake, the (+) sense lead is actually connected to where the (+) supply is connected. Insignificant to the problem, but I'm updating for accuracy

1585773858054.png (46.5 KiB)
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Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @mtnscott

the answer is:

2. Could this be caused by the BMS shutting down during charging?

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Why would the BMS shutting down cause the MultiPlus to shutdown? This is bad as it disconnects A/C for short periods of time,

Because the battery disconnects, the voltage spikes and the Multi shuts down to protect itself and other connected components.

What you can do:

-first let the batteries balance, charge them for a longer period (1 day? 2 days?) at a voltage where they do not disconnect,

-then slowly raise charge voltage to about 14.2 volt.

What is the advised charge voltage of the batteries? please check the manual of the batteries, that will probably also describe how to balance new batteries.

Jeremy Albrecht avatar image
Jeremy Albrecht answered ·

I'm actually seeing something similar in my Airstream with my newly installed system with Lion Energy UT1300.

I have 6 of the batteries in series connected to a Multiplus 12/3000/120-50, with a SmartShunt doing the monitoring. There's also a SmartSolar 150/85 attached, but it's powered down as the solar panels aren't installed yet. The batteries, Multiplus, and SmartShunt are all connected to each other with 4/0.

It runs fine and happy on absorption and float, but if I draw the batteries down a bit to test and then turn the shore power back on when it nears the end of the bulk phase the Multiplus cuts out, then restarts for about a minute, cuts out again, then comes back online in absorption. At that point it runs fine.

I have my Absorption voltage set at 14.2 and Float at 13.9, with charge current set to 80A max, all per the recommendation of someone else with a similar set up. When I've tested setting absorption voltage or charge current higher the BMS trips every few minutes during bulk.

Diagram attached for reference.

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Hi @jsalbre

I've looked up the user manual of your batteries:

"Before connecting, each battery must be independently fully charged. "

how did you charge the batteries to get them balanced?

Jeremy Albrecht avatar image Jeremy Albrecht Daniël Boekel (Victron Energy Staff) ♦♦ ·


I connected each one to the MP until their indicators showed full + a bit extra.

Ok. what charge voltages are you using?

I think I'd start with charging to..14? volts, for a while, then slowly raising to 'normal' advised charge voltage.

Normally I'd use an adjustable power supply to slowly charge at very low current, until batteries are fully balanced. But it can also be done with the MP.

Jeremy Albrecht avatar image Jeremy Albrecht Daniël Boekel (Victron Energy Staff) ♦♦ ·

Absorption at 14.2 (MFG says 14.6, but that kicks the BMS every few minutes), float at 13.9. It's been running like that for about 5 days, with essentially no draw.


For the best advice you'll have to ask your battery supplier.

The only thing I can advice is to lower and than slowly raise charge voltage until the batteries work properly.

boogymanxxl avatar image
boogymanxxl answered ·

Hallo in der Runde, gibt es zu diesem Problem schon eine Lösung? Ich stelle ähnliches verhalten eines MPPTs innerhalb einer EASYSOLAR 48/3000 fest. Benötige hilfe.

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Hi @Boogymanxxl

1. make sure the battery is fully balanced

2. charge to a lower maximum charge voltage

If the battery disconnects itself, it does so to protect itself, usually one cell is at a too high voltage, when a battery is fully balanced, this shouldn't occur during normal operation. Please read the battery manual on this.

boogymanxxl avatar image boogymanxxl Daniël Boekel (Victron Energy Staff) ♦♦ ·

Hi @Daniël Boekel

ich verwende 4x (neue) AGM 12V/120Ah in einem 48V verbund. Typ SACRED SUN SPG12-120 /SPG12535W

Ich habe beobachtet:

Wenn plötzlich der PV Ertrag von 3000W extrem sinkt (z.B. auf 800W), dass für kurzer Zeit die Last fehlende Last aus den Batterien entnommen wird (2200W), was zu Spannungs- und Stromspitzen führt. Eventuell sogar zur Abschaltung des Multis führt.

Das ganze Problem besteht bei "Ladung" der Batterien,

nicht wenn die Batterien Voll geladen sind.

Hi @Boogymanxxl

what components does the system contain? how many multi's, etc?

Is the system online on VRM?

I'd start with measuring all DC wiring to see if somewhere there are voltage drops.

boogymanxxl avatar image boogymanxxl Daniël Boekel (Victron Energy Staff) ♦♦ ·

Verbaut ist eine Easysolar 48V / 3000

Ja das System ist auf VRM Online Nachvollziehbar.

Was benötigen Sie dazu?

Hi @Boogymanxxl

Ok, I looked up your site trough your email address.
I see you run down your batteries to about 41 volts (at low currents), this is very unhealthy for you batteries.

I'd first do a full capacity test of the batteries, so check if they are still ok. defective batteries can give all kinds of strange errors.

boogymanxxl avatar image boogymanxxl Daniël Boekel (Victron Energy Staff) ♦♦ ·

Bitte schauen Sie sich die Werte ab 28.04. 2020 an. Davor waren schlechte Batterien verbaut. Gerade vor 15min wurde der Multischalter schon wieder ausgeschaltet.