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MPPT 100/30 float issue

Hi all,

I've had a look through the masses of previous questions and unfortunately couldn't find any that were quite the same as mine.

Recently I have noticed that my SmartSolar 100/30 completes it's bulk and absorption stages and enters float mode. When in float it will match any current draw from the battery for roughly an hour and then will suddenly no longer keep matching the battery and it will then start dropping down from 100%.
It says it is in float mode, there is plenty of sunlight and panel voltage present, however it doesn't output any charge to the battery. No other chargers connected to the battery.

I have the float voltage set to 15.8V and even when the loads connected to the battery increases it does not kick it back into bulk.

I then have to reset the controller by disconnecting the solar, then battery and reconnecting, which it will then it go back into bulk mode, absorption mode and then eventually into float again.

Has anyone else experienced this issue? Is it potentially a firmware issue?






ksmith asked
klim8skeptic commented ·

13 Answers

250/85 going to float 150/70 x 2 still in absorb

I just expanded an existing installation by adding a 250/85 to an existing system with 2 x 150/70 charge controllers . All wired up this afternoon, but the new charge controller is just sitting in float rather than charging as well. The old chargers are in absorb and the new addition goes straight to float, meaning the new array is not doing anything . Is there a fix for this ? One thought I had is the the 150/70s are using the adaptive charging ( which I cant change) and the new one I have set to fixed absorb time . The 250/85 didn't even run through its full absorb time before going to float

thanks in advance

jdm asked
mjs500 answered ·

3 Answers

Multiplus II shows wrong DC Voltage -> State „float“ prevents charging

My system is an ESS with Multiplus II, Cerbo CX and two MPPT 250/70 and the smart shunt 500 in an 48V System LiFePO4 (no BMS).

The problem is, that due to any reason the DC Voltage shown / measured by the Multiplus is higher than the real DC-voltage. The shunt shows the correct voltage (checked with a voltmeter). The result of this mismatch is, that the Multiplus „thinks“ the batteries are full (state „Float“) and therefor the MPPTs are not charging .

When I switch off the Multiplus, the MPPTs are still not charging. But after rebooting the Cerbo both MPPTs are charging now to the proper voltage and SoC.

The system ran fine for more than half a year. Then one day this problem showed up. Updating to the latest firmware did not solve the problem. After increasing the Float Voltage from 54V to 54.3V it worked a while very good. But now the phenomenon started again.



Are there any ideas how to solve this?

tomw asked
tomw answered ·

3 Answers

SoC jumps upwards when it shouldn’t be.


ESS GX system, 5kW MP-II, 3kW SmartSolar, just 5kWh LFP battery (no networked BMS).

The battery has a high internal resistance and as soon as charging at over 20A, it’s voltage peaks to the bulk set voltage, hence percentage jumps from whatever calculated value to the set percentage as set on “State of charge when Bulk finished” by VEconfigure on the MP-II.

Is there a way to disable this adjustment of percentage?

I’ve adjusted “State of charge when Bulk finished” to 60% (because that’s roughly where it really is), but now SoC jumps all the way to 100% for some reason half an hour later, while the battery still sips 1kW of power for at least two hours.

Only thing I can think of regarding the 100% jump, is that the BMS kicks in and cuts off charging for a blink, so Victron translates this as full. Depending on your perspective, that could make sense, so I will be trying to cap charge current a bit and see how it goes.

However, SoC with no adjustments could also be an option. Is it really that difficult to leave SoC alone and only adjust it according to the measurements made by the interal MP-II coulomb meter?

thanar asked
thanar edited ·

3 Answers

Float/Absorption signal on Venus GX


I want to use the float/absorption signal to control an external device (geyser) Js this signal available on one of the Venus GX external terminals?

I am making useof the extra power after the batteries arefully charged, hence "float" despite some kWh would still be available.

Any other way to pick up that signal.

Thanks a lot


Walter Gygax asked
usernamepasswordbs commented ·

1 Answer

Getting multiplus to float

I have my off grid setup working quite well now but I am having a problem getting the multiplus 2 to come out of absorption and go in to float, I can get the MPPT to go to float, I have a feeling this may be something to do with the tail current size which is not adjustable on the multi and the size of my battery pack, the only thing I can think of to get over the problem is to drop the absorption time further on the Multi.
Anyone have any better ideas ?
Setup is 48v 930ah (C5) traction battery
Victron 48/8000/110
Fronius 8.2-1
250/100MPPT ve can
Smartshunt 500
Cerbo GX
Thanks for any help

scraggs asked
kevgermany commented ·

1 Answer

Victron Multiplus 12/3000/120-50 wont hold float voltage

I have a Victron Multiplus12/3000/120-50 configured with 3 SOK 206ah Lithium batteries. The charger is configured to hold a float voltage of 13.8 volts. I recently installed a Victron 30amp DC to DC charger, and notice that the Multiplus no longer will hold the 13.8 volts in float. It now only holds 13.5 volts. If I reset the Multiplus, it will go back to bulk and recharge the batteries, but the situation occurs again. How can I diagnose, troubleshoot and fix this issue?

garysclark asked
kevgermany answered ·

1 Answer

Float / Bulk on Orion DCDC question.

Hi there, my Orion DCDC seems to be on float as my battery is slowly discharging. At what point will it kick in again for a Bulk charge?

My Victron Smart Solar charger just goes straight to Bulk.

Battery is sitting about 75%

Charging profile is Factory default for LiPo4

richardc asked
kevgermany answered ·

1 Answer

Centaur charger does not switch to float

My Centaur 24/40 charges 12 2V units and has suddenly stopped switching to "Float" and only charges "Bulk" to the maximum of about 28.5V at about 6Amp. Any ideas? Can it be fixed?

vacent24 asked

0 Answers

How an inverter works in "External Control" mode?

I'm trying to understand how "External Control" mode works in case we have shore power.

Setup: MultiPlus 48/5000 + Cerbo GX +(over CAN Bus)+ LFP battery (similar to this one).

I'm struggling with OverVoltage and DisbalanceVoltage errors on the battery.

And I have some doubts regarding (VEConfig 3) settings changes which I'm trying to play with.
For instance, I noticed limitation: the battery does not allow me to use Charge Current more than 30A.

I'm playing with different settings, e.g. Absorption/Float Voltage.


(DVCC➡Maximum Charge Voltage: 55.3)

In my understanding, the inverter shall go to Float after full charge battery. But it does not (I mean, the light "Float" does not light up).

Before I connected CAN bus to the battery – "Float" was working.


  1. How to figure out which settings are applicable in "External Control" mode?
    1. Does an inverter has some influence or BMS controls most of things?
  2. If there are limits, how to deal with OverVoltage and DisbalanceVoltage errors on the battery?

kirby asked
nickdb answered ·

1 Answer

24v Battery Bank in Float Before Bulk Charge Volts Reached

I have a 24v bank of fla's comprised of twelve 6v 235ah making a bank of 705ah. They are Rolls so I have set the charge voltage to 30 and float to 27 which is recommended. I've been charging this week to get a full deep charge accomplished in this new bank as it's been about a month now and we haven't done a full float on it. So, lots of charging. Right now though, the system shows that the volts is under the 30v that the charge is set to, but above the 27v that float charges at.

QUESTION: Did I wrongly assume that it would do a bulk/absorb charge to reach 30v, then switch to float to finish for an hour? Not sure why I'm seeing what I'm seeing. Is something wrong here or is something right here:


allswell asked
allswell commented ·

4 Answers

State of Charge not exceeding 25% even thought Charge Controller on Float?

I'm advice on a 24v Easysolar Unit, Charge Controller 150/35 and BMV712.

Our SOC (on all devices) does not exceed 25% even though the MPPT Charge Controller & Easy Solar are getting to float every day.

We recently replaced the batteries so I dont think it's those.

It feels to me like perhaps the unit is not setup correctly? Perhaps as a 48v system or something?

Any ideas?

Screenshot 2022-11-08 192958.pngScreenshot 2022-11-08 193010.pngScreenshot 2022-11-08 193029.pngScreenshot 2022-11-08 193231.pngScreenshot 2022-11-08 193538.pngScreenshot 2022-11-08 193550.png

james09 asked
klim8skeptic answered ·

2 Answers

float - Lithium manufacturer says no?


Our installer just installed a Victron Phoenix Smart 50 amp 3 bank charger to new 2 lithium battery banks (4 total). We didn’t know what to do about the float setting, as Victron’s website suggested 13.2V however the manufacturer's website said that a constant float charge will degrade the battery. See excerpts below.

Can the float setting be zero? What happens if I’m not on the boat for an extended period, but it’s connected to shore power?

Thank you for any help you can offer.

From Victron:

6.4. Lithium batteries

Lithium Iron Phosphate (LiFePo4) batteries do not need to be fully charged to prevent premature failure. The default lithium (and recommended) settings are:


12V system

24V system

48V system

Absorption voltage




Absorption time




Float voltage




From the manufacturer:

Should I use float chargers or battery maintainers for my lithium battery?

No, LiFePO4 batteries should be disconnected from the charger when fully charged. Float charging, or maintainers are not good for lithium batteries. Keeping a constant float charge or topping off charge also can cause metal plating and will reduce the lifespan of lithium batteries. Dakota Lithium batteries also have a low self-discharge rate of <5% a month. This low self-discharge rate makes a battery maintainer for long term storage un-necessary (for more on battery storage see section below).

jpcirig asked
Daniël Boekel (Victron Energy Staff) answered ·

4 Answers

What should I set Lithium Battery Absorption Time to?

They say that Lithium batteries don't need to be charged in absoption mode. I've heard that when charging Lithium you should go from Bulk straight to Float. Will setting the absorption time to zero achieve this? What about setting the absoption voltage to a really low voltage that is never achievable? What do others on this forum know of this? What settings do others use when charging their caravan Lithium battery? MPPT Bluesolar 100/30, Sentry 300AH Lithium, 300W solar.

redrover asked
zoneblue edited ·

6 Answers

Why isn't my smart BMV going into float?

I have 300 w of solar on my rv and a 335ah battery bank and I can't seem to get them in float mode. I realized the other day that the state of charge wasn't synchronized to 100%. It's possible that happened a month ago when I took it in for service and they may have disconnected the batteries momentarily without me knowing. So it was reading 100% at 11.7 volts and charging accordingly. It hasn't been in float mode for 30 days at least and absorbtion only a few minutes of a few days. I turned off all the loads and waited for a sunny day to try to synchronize it, get it up to absorption and then float. Today it went into absorption for exactly 2 hours but then directly back to bulk. Am I missing something? I have set the charging parameters for the centennial batteries for their website. This is all new to me so any advice is appreciated!

Bmv 712 monitor

Mppt 100/30 controller



annie-314 asked
annie-314 commented ·

6 Answers


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