hawk14 avatar image
hawk14 asked

Battery capacity dropping with Generator on

Forgive me ahead of time as I'm bit new to Victron and the components. We have the following components in a Marine setting on a sport fishing boat:

  • MultiPlus 12/3000/120-50 120V (firmware 506)
  • Lynx Shunt 1000A VE.Can (firmware v1.10)
  • All systems are under 1 year old
  • 3x 12V Batteries in our House Bank
  • 2x Starting Batteries (one for each engine)

Issue is as follows:

Before leaving the dock, we turn generator on and move from shore power to generator. Almost immediately after disconnected, the Capacity on the Remote console starts to drop. We notice as the capacity decreases that the system is still on "Float" mode and there is no charge going to the Batteries (see first picture below):


Notice after a period of time the battery capacity at 87% (although 14V) and there appears to be no flow moving to the battery. What I mean by this is that usually we see small dots that move from Shore to Inverter and Inverter to Battery icon above. Also notice the system is still on "Float" at 87%. We've seen this drop all the way down to ~53% and it never moves off of "Float". Inverter Switch setting is set to "On".

After reviewing some other posts in the community, we "Reset" the device from the following area: Menu => Inverter => Advanced => System Reset

After "Resetting" the system, Inverter will move to Bulk then shortly after to Absorption, then Battery will charge back to 100%. See next picture just shortly after "Resetting":


Notice that the system went to Bulk and then to Absorption and we then see the "dots" back flowing to the batteries. The system will charge back up to 100% within about 10-15 mins and stays at Float. Then, it seems like the process starts all over again shortly after a small load is turned on. I then "Reset" it, and go through the process. During all of this, the battery voltage never drops below 13V.

I did some further research and noticed someone discussing possible issues with a firmware version. So, I updated the Lynx Shunt, but did not update to latest firmware that was recommended for the MultiPlus as I want to be sure I understand a bit more.

In my opinion, knowing its a brand new system from the boat factory, I assumed that this would be fine tuned. However, I'm finding myself digging deeper as there has yet to be resolution on the situation. Not something you really want to be thinking about when your in middle of the ocean.

I read a few of the articles in the community regarding Bulk/Absorption/Float, but not sure if they apply to this situation. This lead me to think maybe the system is looking at voltage and not the total capacity or something. Knowing the batteries never hit below 13V, maybe it thinks it can still be in "Float" or something? However, then why would it start to charge after "Resetting"

Overall, I'm leaning to believe I should update the firmware on the MultiPlus, or there is some setting that I need to modify to get this working properly.

While I plan on engaging a Victron partner if not resolved, I'd sure like to better understand if its something I can just modify and get resolved.

Any help you all can provide would be greatly appreciated.

battery chargingmultiplus ve.buslynx shuntfloatmarine
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Justin Cook avatar image Justin Cook ♦♦ commented ·

When you reset it, it resets the charge logic, so forces it back to the beginning of its 4-stage charging logic.

It looks like what you're experiencing is a result of the "rebulk voltage offset" which means that the inverter won't automatically kick back into Bulk until the battery voltage has dropped 1.3v below Float voltage if set to a Pb charging profile or 0.2v below Float voltage if set to a Lithium charge profile.

While this voltage offset is not user-configurable, as it exists to protect the battery bank, you can change its behavior by raising your set Float voltage or by otherwise changing the charge profile with that behavior in mind, or you can force the unit to Absorb by following the procedure in section 3.3.3 of the manual, screenshot below:


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force-to-absorb.png (96.0 KiB)
hawk14 avatar image hawk14 Justin Cook ♦♦ commented ·

3 questions for you:

  1. In regards to changing the "Float Voltage", would that have have any negative impact on a possible overcharge or otherwise negatively impact the batteries? I'm noticing my settings in VECConfigure have it set for 13.6v, but default in system is 13.8v. The battery spec, at 77 deg F, have it at 13.3v +/- .1v
  2. I'm assuming by "Charging Profile" you mean the Charger Settings in VECConfigure, right?
  3. Knowing the Generator is "on" when this happens, why wouldn't the batteries just stay at close to the 100% capacity just as they are when they are on Shore power? Seems like the capacity only starts to drop when we move from Shore to Generator Power.

I'll review specs from Batteries during this process as well.

Again, thank you for the quick response.

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2 Answers
hawk14 avatar image
hawk14 answered ·

@Justin Cook

We were able to resolve the problem this weekend.

You had mentioned that it was a possible connectivity issue in your answer, which was the problem.

In summary, I have 3 batteries in the "House" bank on the vessel. Battery 1 was connected properly. However, on Battery 3, there was a ground wire going from the black battery post to the ground. We ended up removing that and placing that from the shunt to the ground.

After doing that, all started working properly... capacity is reading properly and now all is running by design.

Really appreciate the brainstorming here.

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Justin Cook avatar image
Justin Cook answered ·
1. Possibly. It depends entirely on your battery manufacturer's recommendations - some batteries are more sensitive to charge voltages than others; a recommendation of 13.3v sounds a lot like Lifeline batteries which do present their own challenges (lots of threads about that here and on other forums as well). Depending on whether you need temperature compensation or not, it may be a better practice to switch to Lithium mode in your case, which would disable temperature compensation but would lower the offset voltage differential to only 0.2v below Float, which could be useful.

2. Yes. Personally I use VictronConnect for programming 98% of VE.Bus devices instead of the old VEConfigure (still through an MK3 of course) but if you're comfortable with VEConfigure then by all means use that!

3. The MultiPlus itself doesn't know the difference between the generator and shore power, since it only has 1 AC input; all it sees is "AC input present" or "no AC input present", it can't differentiate between different sources of that AC input. In both of your photos though I notice that your battery voltage is showing quite high relative to the reported SOC - 14.xx volts wouldn't typically be seen at the battery when it's reporting <90% SOC, and since battery voltage is what the MultiPlus is looking at to determine its charge state, it makes me wonder if there isn't something else entirely going on in the system that's leading to the behavior - whether a misconfigured battery bank capacity in the system, or a load or charger that's bypassing the shunt, or something of that sort I can't say. I can only say that indeed, I would not at all expect a MultiPlus to kick into Bulk charging when measured battery voltage is at 14.xx

I'd certainly suggest either grabbing the multimeter and just checking everything in the system, and all wiring and programming, or engaging an experienced and reputable systems installer in your area to check everything over, as that just doesn't look right to me.

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hawk14 avatar image hawk14 commented ·
Interesting idea on setting the mode to Lithium to account for change of .2v rather than 1.3v.

You are correct. The batteries are the Lifeline 8D AGM batteries. Just noticed what you said about others talking about similar issues.

One of the individuals in another forum stated the resolved the issue by updating to the latest Victron firmware and then updated to lithium profile and all working as needed.

I'm going to reach out to Lifeline and see what they say about the float/charge settings to see if I can get a more accurate setting as their float range is appears to be very dependent on temperature.

I'll reply back here after speaking with them and update it. Looks like there are several others in the community here that are looking for a similar answer.

I'm also going to get a multi-meter on it tomorrow and see if I can discover if we're missing something else.

More to come...

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hawk14 avatar image hawk14 commented ·

I have spoken with a Lifeline technician and they provided me with some good information. I'm also wondering about the AC input current setting. Its currently listed as 30A, but I thought I had 120V/50A.

I've attached an excel spreadsheet of the current config as well as some recommendations that Lifeline had. There 2 sheets in this spreadsheet... one with settings for the Inverter and one for the Shunt... both have recommendations from Lifeline.

20240427 - Inverter Settnigs - Victron.xlsx

I'm hoping this may provide a deeper dive into current settings against some recommendations that Lifeline had.

They also stated that something isn't plugged in right if capacity is at 87% and voltage was showing 14V.

Hopefully this attachment will help shine some more light on it.

Any feedback would be helpful!

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VictronConnect VE.Bus charging manual  

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Lynx Shunt VE Can online manual

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