question

Best that you contact your Installer and he will explain it all to you and answer your questions, as he has setup the system for you.

@Guy Stewart (Victron Energy Staff); @WKirby; @Boekel; @Margreet Leeftink (Victron Energy Staff)

Hi Victron Staff, There is a sense of increasing concern and even borderline disillusionment on many of the sailing vessels that I am in close contact with and many of them have Victron equipment on board. This includes sailing cats (catamarans) from countries as far away as South Africa.

That is not to say that Victron equipment is necessarily at fault but as my reply above indicates there are a number of us who are having a range of 'difficulties' getting (or keeping) our systems operational and this in part relates to getting 'definitive' answers in respect of the software configuration aspects. I understand the variations can make this 'complex'. I am a little stressed as this is not a motor-home or other installation where I can simply park-up or ring and have someone visit to get a solution; our vessel safety and navigation systems entirely rely on DC power and indeed our lives can be in jeopardy if loss of DC occurs at an inopportune time. I tried writing up this query but this site now seems to have 'lost' its carriage return capability and I can only write on one line (string). Can someone contact me so that I can give a detailed query; In particular I need to know what the 'Muti' settings, Lynx Shunt 1000 settings; Venus with DVCC enabled settings should be for our system. Finally I have spoken to dozens of boat owners and they (we) almost all relay on State of Charge as a basis for making decision on charging (generator usually) and load management (discretionary dump loads) etc. and wish to operate our battery on the basis of 'extending the life' (for LFP); I need some guidance from Victron as to WHY my system when DOWN with 74% SoC? Thanks.

@Paul B, thanks for the lesson in Ohms Law and it is refreshing to see the 'hose pipe' example used to explain this. I think I first heard that at university (Canterbury Engineering School - Christchurch) in 1975 when doing my airforce degree (day 1, lesson one in DC Theory I recall).

I understand all you have said - that being said I do not necessarily agree with the interpretation of the simplicity.

Note the first reply exceeded the 2000 characters limit so this is an abridged version. Excuse the brevity.

Point 1a.

extract from Victron documentation. Note comments in pink are my PDF edits.

How do you double the life of your battery if you cannot rely on this SoC. Victron themselves refer to the SOC (Depth of Discharge) in their guidance on the 'Cycle Life'. From an operational perspective it is almost impossible to 'manage' [DC] systems on a variable [voltage] that changes extremely quickly, as you correctly say. SoC is at least manageable, if accurate.

How do you manage your longevity (battery cycles)?

Point 1b. Reference LiPo charge voltage.

You appear to be unhappy with 28.6 V; see Victron battery documentation. At 28.6 V this is within the tolerance given by Victron).

Why do you suggest 28.2-28.4 V?

By being 'too high' what do you understand I am doing or missing?

Point 1c. By charging 'fully' are you actually stressing the chemistry and reducing battery life. What is your understanding? Perhaps you can advise me what settings you have on the 'Charger' page (Ve.Configure) of your Multi?

Point 2. For clarity I am trying to get a clear (absolute if possible) understanding of how our system will perform under stress because we are on a blue-water sailboat and I must be able to understand how the system will perform in the worst of weather (stormy and raining for days) - which leads directly to high use of autopilot hydraulic pumps and sail winches combined with little solar and absolute necessity of keeping the navigation equipment up and running.

I have regularly charged the batteries so with the batteries at >90% for long periods including 100% for numerous hours on numerous days as shown by the VRM output below;

Further I had previously seen the SoC down to 6% as per following screen shot on 16 March.

Assuming for a moment that it is not just the 'get your battery fully charged' scenario); What goes into the 'setup' that makes the SoC (sample of two occasions) so variable?

[Note. What is not shown is that shortly after the 6% the BMS also gave a low voltage shutdown (sample 1) - a deliberate system test to see if the VE.Bus BMS was actually configured and wired correctly].

Point 3. Given the above history of charge state combined with previous SoC levels - Why would I not be able to rely on it now (ie. the difference between 74% and 6% is a significant 'discrepancy' and clearly at 6% (an actual reading) they system was 'working'.

I am at a loss to understand what is actually different (i.e. no deliberate setting changes). Further VRM reports (nil) battery low voltage alarms???

Point 4. Your suggestion about another 'installer' is based on what? I am happy to provide any necessary detail as to the configuration - perhaps also your assumption is that this is the 1st installer - (not correct); and that he is on his own (also not correct); ALL are Victron 'resellers' by the way - hence this post.

With respect to our 2 x 200 AH (total 400 AH) 24 V LiFePO4 batteries using a Multi 24/5000 with a 4.5 KVA generator to charge them; can someone suggest what settings they would use in their system.

Can someone also advise what they understand is meant by 'charged voltage' @ 28.4 v in this instance. (Lynx Shunt 1000 settings).

With respect to the following Venus settings - is there anything that stands out as wrong or needs attention?

Thanks in advance.

With respect to the Venus.local and Lynx Shunt - Battery settings as shown below.

Can someone give guidance as Sync SOC. When the charger has been on float for how many minutes/hours do you consider that LiPo are 100%?

How often would you 'sync' the SOC?

Reference 'Calibrate Zero current. I have switched off all loads except the VE.Bus BMS and Venus. I press the 'Press to set to 0' button and also on the keypad I press the 'space' bar. There does not appear to be any reaction; no resetting or other indication.

Can someone advise if there is any 'feedback'?

How often would you do this action?

Can it be confirmed that if this is done in error (i.e. pressed when indeed there is a current (load) that this will affect the SoC calculation?

Hi @Michael Riley

sorry I can't comment on all issues at once, but some observations:

You don't seem to have the VE.bus assistant installed in the Multi, that's one of the errors.

This can also explain the incorrect SOC, what is set in VRM as 'battery monitor'?

About SOC: remember that at 24V your batteries are almost completely empty ('running on fumes')

Also I wouldn't worry too much about the amount of SOC you use with LiFePO4 batteries, I'd use 80% of SOC without any worries, they have a very different lifespan compared to 'regular' Li-ion batteries (those last longest when not fully charged for example)

@Boekel. Thanks very much for your time to respond. The 'reply' button was not visible to your post so I respond here. I have separated your comments and itemised - trust this is acceptable.

[Boekel] You don't seem to have the VE.bus assistant installed in the Multi, that's one of the errors.

[Riley] - incorrect. See attached. Assistant is loaded.

For a system with Lynx Shunt, Mutiplus, MPPT, VE.Bus BMS, and Venus with DVCC enabled:

1. Q1 How many assistants in the Multi should there be? If more than the VE.Bus assistant what is the title as seen in VE.Configure?
2. Q2. Is there anything in DVCC that may add to this problem. I note a few comments ( incl from Victron) about the solar currents and voltage. What are your thoughts in respect of the DVCC settings. Can you give me a brief list.

[Boekel] What is set in VRM as 'battery monitor'?

[Riley]. The Lynx Shunt. See attached. I am not sure why you refer to the VRM site. Let me explain - to be specific there are 'results' I see on VRM which are total wrong (i.e. my generator production hours showing up as 'solar' generation) so there can be a difference between VRM and 'reality'. The 'Battery Monitor' logo on VRM also shows up as a BMV?

This is also an area with a few options. See two screen shots below from my Venus - Settings - System Setup - Battery Monitor / sub options are: Automatic, MultiPlus, No battery monitor, Lynx Shunt VE.can on VE.can. I have selected the last option - the Lynx Shunt. This is shown on the screen prior and on VRM.

[Boekel] Comment "About SOC: remember that at 24V your batteries are almost completely empty ('running on fumes')".

[Riley] Understood. The System Overview - DC System graph is included above. For brevity I have expanded this to the last few days and included below. In any case the lowest 'voltage' I have seen is 25.21 V and this graph covers the period of the 'black out'. Why do you mention 24Volts? Am I missing your point?

[ADDENDUM] Went looking for the reason for Boekel's comments re 24V. I now see that the Bluetooth login result for both batteries shows the 24 V reference and have added this addendum. This value was missed by me and it does not show up anywhere else. Is this another issue or a clue?

Note: On VRM I still do not see any 'low voltage' alarms in the 'Battery History' so I do not entirely rely on VRM as a source of facts.

[Boekel] Comment "Also I wouldn't worry too much about the amount of SOC you use with LiFePO4 batteries, I'd use 80% of SOC without any worries, they have a very different lifespan compared to 'regular' Li-ion batteries (those last longest when not fully charged for example)"

[Riley]. A little confusing. My interpretation. You use from 100% down to 20% SOC (i.e. you use 100-20 = 80% of bank capacity) without worries.

Happy that you are not worried but what is your expected life cycle value. i.e. are you looking for 5,000 cycles? Are you saying that the Victron LiFePo4 (new format 24 v 200 AH) is different from 'other batteries'. I was using the Victron datasheet for these batteries to get my 'cycle' information.

What do yo recommend for my batteries as the SoC range you would use if you had them (or do you - have the same?).

I also am 'happy' to use a significant amount of capacity - but this is becoming the key aspect of this post I believe - i.e. we are both referring to SoC and this is now what appears to be the problem I need to resolve. Meaning getting a more accurate reading. Given your incorrect assumption about the assistant above and the reference to the SoC therefore being wrong - what would be your next suggestion be as to the cause. I believe it is something to do with the 'Zero current' button.

On this issue.

1. How do you get 'zero' current when the device you are using to set it is part of a system that is consuming electricity and which includes (to the best of my knowledge); Lynx Shunt, BMS, 2 x BP and Venus still as 'consumers'. I am reasonably confident that I can remove all other 'loads' being: Multi (turned off using Digital Remote connected to BMS and switch on front of Multi also off), MPPT and panels (isolated), and Loads (DC Load isolators turned off). Note that the Multi and MPPT are still physical wired to the Lynx Distributor.
2. Do I need to 'remove fuses' in the Distributor to get this achieved?
   <Note in my past I was working as a test engineer for Hughes satellite power supplies at one time (Morebank - Sydney-AU) and we were measuring very small amounts in clean rooms etc. As the head of Philips Test and Measurement supplying equipment to the Hughes Laboratory , I am used to seeing '0' current as 0 not something close by - but I acknowledge that this is a different application> I believe the above questions will assist me in getting some context in this application.

Once again thank you for your time so far.

@Boekel, Thank you for the response. For anyone else reading this entry this is what we now understand (6 days later); SUMMARY

a. First up - my fault in inadvertently letting the battery voltage get critical. As a newly installed system this was a test that I was intending to do at some stage, but anyone using LiFePO4 really need to understand the battery voltage(s)/cell. As stated above - this is one of the only 'truths'.

b. the VE.Bus error is 99% likely because the MultiPlus shut down. Will need to look into the sequencing as to what shut down first (if possible) as I would have understood that the VE.Bus BMS initiated this (correctly protecting the battery) but should have also shut down the Venus at the same time - so how did it record the error?

c. Assistants - only one needed. The LiFePO4 assistant - for the functions of just 'running' the batteries. I will also load the Start/Stop Generator assistant now as this functionality can be used have a more sophisticated battery charging arrangement when on shore power/MPPT etc. (Tks Boekel for that on another post).

d. SOC. Whilst there are many who say you should manage LiFePO4 on the cell voltage [only] - this is not practical in my opinion for our operation. I need something that has more predictive capability. In addition PROVIDED you can get the 'ZERO Current' accurate then the SOC should be more accurate. Given that there is still a 'discharge' across the shunt, which is what one is 'calibrating', by the very equipment that are 'setting the zero-point' then the SoC will always be a little optimistic. That is to say that the battery actual SOC will be lower than the measured one - for any one cycle - being until the next 100% resync and you should do this, say, monthly to balance the cells in any case. I disconnected every load that was practical to do so and then pressed the space bar (in the Venus display) as well as using the mouse to press the button. No visual or aural response noticed. As of this time no-one from Victron has deemed to respond to the above query about button press 'feedback', which in my opinion is important to have.

Now monitoring battery cell voltage regularly; SOC seems great but have not had the same load on the system as previously and the solar is topping up early - have lost faith in the system a little and can re-iterate that there are 'gaps' in the information available (just look at the posts on this site) for any contemporary configuration. Thanks to all above who responded.