question

h-copter avatar image
h-copter asked

BSLBATT voltage too low

Hi, I have a newly installed MP-II 48/5000 with 3 x BSLBATT B-LFP48-100-RM in ESS configuation. The system is working, but isn't performing well as it goes into Sustain mode when at around 50% SoC with only a modest discharge current due to voltage dropping below 48V.

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When freshley charged, the battery is only just hitting 51V, and quicjly drops down. I am not convicned my Charger settings are correct, they are:

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and accoring to the Victron manual they should be

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Should I change the charger settings to match Victron's manual?

Many thanks

Multiplus-IIbslbatt
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5 Answers
JohnC avatar image
JohnC answered ·

Hi @h_copter

Why would you hesitate? The BSL manual (linked by Victron) says the same.

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Alexandra avatar image
Alexandra answered ·

@h_copter

If it is going into sustain mode, then you also need to adjust the ESS assistant values. Your poor batteries are being chronically undercharged.

Just follow the manual. It literally spells out what to do. Dont forget the mppts as well.

I have several systems with BSLBATT 7.0s working well using the recommended settings. And the systen work mostly offgrid these days with the blackouts.

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h-copter avatar image
h-copter answered ·

@Alexandra @JohnC Thanks - will apply the recommended settings with confidence now! One other question, how should I get the batteries back to full strenght? Should I switch the MP to 'charge only' mode for a while to ensure they get a full 100% charge? Thanks

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Alexandra avatar image Alexandra ♦ commented ·
@h_copter

In the ESS menu, set the system to keep batteries charged.

In the VRM have the widget for the battery bms cell voltages. You may see one or two high voltage warnings for a bit.

As long as they are not alarms don't stress about them. Let the battery sort itself out for a few days. Then start cycling them again.

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h-copter avatar image h-copter Alexandra ♦ commented ·

@Alexandra The plot thickens. Apologies for the long post, but I'd be grateful if you would review.

To confirm: I have B-LFP48-100-RM batteries. Here is the link to the supplier's page which gives this code and confirms they are 15cell batteries. However, BSL site quotes model number 'B-LFP48-100E'. I can't find a model 'B-LFP48-100-RM' but I assume this is the same battery as it also quotes 15cells. However, confusingly, the data-sheet that is linked from the BSL site says '51.2V (16S)'. Is it possible that the battery used to be a 16cell/51.2V battery, but it's now 15cell?

If so, that might explain the issue I am seeing. This is the Victron BSL manual, which refers to 'B-LFP48-100E' and says the charge voltage to set in VE.Config is 55V

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But then the Cerbo-GX manual says the charge voltage is set dynamically by BMS and so "setting up charge voltage or charge profiles in VEConfigure is not necessary and will also have no effect." I have no idea why Victron are giving contradictory adivse between two documents. But it does explain why the charge voltage of 55V I set was ignored and the Cerbo shows it set to 51.5V

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I believe the Victron BSL manual was written for a 16cell battery. This is because it shows an example of cell voltages being 3.34V and the battery being 53.4V.

So, if my battery is 15cell, then the CVL of 51.5V looks good and it doesn't matter that VE.Config is being ignored. HOWEVER, the Dynamic cut-off voltages set in VE.Config ARE NOT BEING INGORED: the Victron BSL manual specifies them to be 47V, which I presume is way too high for a 15cell battery.

Is my analysis correct? If so, what should I change the Dynamic cut-off (and Sustain) voltages too? How do I get Victron to take note of this and amend their documentation to include my battery?

Many thanks

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Alexandra avatar image Alexandra ♦ h-copter commented ·

@h_copter

Had a look. If it is 15s and they use the same charged voltage as all their other batteries at 16s, then absorption is 51.6V and float is 51.4V.

In all honesty I thought all BSLs in the domestic was 16s? I could be incorrect. but I can only find that battery you have on one (the one you linked) website. Not even on the BSL website.

The real question is - are you using the higher voltages (recommended ones) and is the system sending high cell voltage alarms? Have the widget loaded in advanced and watch the bms cells voltages. and watch the CCL one as well.

It also may be worth checking with supplier if they made a typo on their page?

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nickdb avatar image nickdb ♦♦ h-copter commented ·
Assuming you are in SA, get off grid are the sole importers. Give them a call and get some clarity. BSL used to only do 16 cell batteries, but if that is what the BMS is sending then either it is incorrectly set, or it has fewer cells and the config would need to change accordingly.
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h-copter answered ·

@Alexandra Monitoring cell voltages would be great, but currenlty I can only see the min/max through the Cerbo. What is the BMS cell voltage widget you refer to, and how do I install it?

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Alexandra avatar image Alexandra ♦ commented ·

@h_copter

That is perfect for local monitoring and for what you need to check.

But you can on the VRM in advanced you can add a widget there, if you have it set up there.

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stroller avatar image
stroller answered ·

@h_copter I to have these same batteries and have had same sort of issues as you with them...

Mine have mostly gone now but not completely. I have also struggled to find any definitive charging, absorb and float values for these batteries. BSLBATT's two websites are woefully lacking with any detailed and specific data for these values and what there is appears to change from one document to another.

Happy to chat on here or offline somehow to work together to gain the definative data needed.

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h-copter avatar image h-copter commented ·

@Stroller If we can work together to get to the definative answer that would be good. Can we chat? Call me on +447980 800615

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