LFP Ext. Regulators: Why do Volts and Amps need to be sampled?

[Statistical]

That was a long winded non-explanation. It is paralleling LFP and lead acid. Not sure there is an ABYC requirement against that but it is not a good idea. Saying there are similar products misses the point. Yes products to parallel house and start battery have existed for decades. They predate lithium house batteries.

[s/v Jedi]

Originally Posted by rgleason

I need to correct something I said with regard to the X2 BMS by BatteryBalance
Mikael Garten , US Sales BatteryBalance wrote back in response to my questions


rgleason wrote:Mikael Garten BatteryBalance wrote:

https://www.victronenergy.com/upload...-BMS-V2-EN.pdf

From Mikael's highly detailed (not included) response, I have learned a more nuanced understanding about what is considered "paralleling LFP and FLA" and what is not.

Thank you Mikael. I apologize for any misleading statements. It appears to me that the X2 BMS should be considered for Marine LFP. In fact I like a number of features in this system.

It is a flawed design. It is impossible to correctly charge different chemistries when they are connected in parallel.

An arduino is an advanced PIC microcontroller. I find a lot of blah blah algo 100+ conditions blah blah. Name them or shut up. The diagram shows a weird DC negative as well.

No, I don’t get a warm fuzzy feeling.

[hjohnson]

Originally Posted by Statistical

That was a long winded non-explanation. It is paralleling LFP and lead acid. Not sure there is an ABYC requirement against that but it is not a good idea. Saying there are similar products misses the point. Yes products to parallel house and start battery have existed for decades. They predate lithium house batteries.

Also seems overly complicated compared to just using a DC->DC battery charger, which will keep your starting battery happy no matter what.

People are needlessly scared of a possible HVC destroying their alternator. No matter which regulator and BMS combo you use, if it’s ABYC compliant, you can integrate enough to make it a non-issue. In my system, before you get to an actual HVC, the BMS will issue a warning, then alarm message on the CAN Bus, which will cause the Wakespeed to stop driving the field. So, even if there were to be a disconnect, it’s no big deal as there’sno field current. In my humble opinion, this system further reduces the probability of a HVC, since the regulator knows not only what the alternator is doing, but is also fully aware of the battery (voltage, current, temperature) and is being fully controlled by the battery.

Similarly, if you’re using a balmar regulator, there’sa control line to enable charging. Connect that to the warning/alarm circuit, and the BMS should be able to shutdown the Balmar regulator before it gets to an HVC.

In a well designed system, no matter how tightly integrated, be it with digital communications, or simple relay signals, an HVC should never occur, and if it does, the alternator shutdown in advance of the HVC actually occurring.

[rgleason]

Just to be devils advocate here, why would Victron show such a design, and is it ABYC compliant?
Fortunately, I am just an Architect with questions, but learning slowly.
I think he says the relay is controlled so the batteries are not "paralleled".


PS: It is pretty clear you all don't like the design, but is it worthwhile trying to understand why two manufacturers would show this and at least one says it is compliant with ABYC.

[Statistical]

Originally Posted by rgleason

Just to be devils advocate here, why would Victron show such a design, and is it ABYC compliant?
Fortunately, I am just an Architect with questions, but learning.
I think he says the relay is controlled so the batteries are not "paralleled".

All selectively parallel battery circuits (i.e. AVR) are controlled I mean that is the whole point.

As for ABYC complaint I have never seen anything indicate batteries of mixed chemistries can't be in parallel either always or as needed for charging/starting. It is just a dumb thing to do because you will either be under charging your lead acid battery or overcharging your LFP but I haven't read anything that indicates ABYC prohibits it. There is a lot of dumb things that aren't prohibited.

[flightlead404]

Originally Posted by s/v Jedi

I have nothing against CAN bus but it simply isn’t needed for keeping a battery safe and healthy. There is no negative effect at all by leaving it out and was never used for BMS systems until people started flipping and being proud of their batteries, willing to spend a thousand bucks for a BMS with shiny precious parts.

Remember that there are plenty sailing for 10 years or more with LFP cells and no BMS at all. It doesn’t need much to create a good BMS.

So what I like is simplicity without giving up safety and lifespan, plus I want full control and nothing beats tweaking the firmware yourself by hooking up a laptop to the BMS and trying out new features in seconds

and in fact you don't need most of the extraneous stuff on the Arduino either.

Once you've got your sketch and hardware working correctly, you can simply build the entire thing around the appropriate Atmel microcontroller and program it directly without all the other stuff the Arduino gives you.

[rgleason]

can-i-connect-dissimilar-batteries-in-parallel
https://www.optimabatteries.com/expe...es-in-parallel


This sounds like a manufacturer trying to sell more batteries, but the image is funny.


AI Chat

How do I parallel two different types of batteries?

Searching for: How do I parallel two different types of batteries?

Generating answers for you…

You can connect two batteries in parallel by connecting the positive terminal of one battery to the positive terminal of the other, and the negative terminal of one battery to the negative terminal of the other. The total voltage of the parallel circuit is the same as the voltage of each battery. However, different types of batteries (flooded or AGM) can have different charging and discharging characteristics, with some accepting a charge or delivering current faster than others. That can be true even if the batteries are the same size. Different types of batteries also can have different charge/discharge characteristics


Can LFP and FLA batteries be paralleled

Searching for: Can LFP and FLA batteries be paralleled

Generating answers for you…

Yes, LFP and FLA batteries can be paralleled. However, you have to be careful and watchful because the Low Volt disconnection for FLA versus LFP and of course you should never take FLA below 50% DOD. High current diodes could be used to separate your two chemistries since each have their own charging system12
https://diysolarforum.com/threads/ca...r.14573/page-2
https://diysolarforum.com/threads/ca...nverter.14573/
https://diysolarforum.com/threads/fl...-if-any.19288/


So what happens when you want to take your LFP down below 50% SOC? - It is disconnected from the FLA

What happens when LFP reaches 20% SOC and it needs to be recharged - do the LFP and FLA get reconnnected again? What happens?

[s/v Jedi]

Originally Posted by rgleason

Just to be devils advocate here, why would Victron show such a design, and is it ABYC compliant?
Fortunately, I am just an Architect with questions, but learning slowly.
I think he says the relay is controlled so the batteries are not "paralleled".


PS: It is pretty clear you all don't like the design, but is it worthwhile trying to understand why two manufacturers would show this and at least one says it is compliant with ABYC.

I’m sure ABYC allows a switch to be used to -temporarily- connect batteries in parallel. We all have had these since forever and also the automatic ones.

But you can’t charge two different chemistries by connecting in parallel and using one charge source. No matter the existence of automatic parallel switches. These were developed for battery isolation where they were the same chemistry.

Originally Posted by flightlead404

and in fact you don't need most of the extraneous stuff on the Arduino either.

Once you've got your sketch and hardware working correctly, you can simply build the entire thing around the appropriate Atmel microcontroller and program it directly without all the other stuff the Arduino gives you.

Yes, this is the idea with the Arduino V3 with the PIC as a DIL package in a socket so you can pull it and mount on your own circuit board. You can even buy the boards for that.

But if you like to keep tinkering with it, you can buy the small Arduinos like a Nano and put that in a socket (make with headers) so you can keep hooking up a laptop and tinker with code. You can even hard code things that would be settings otherwise, to make it simpler and use less hardware.

There are even nicer options that I didn’t mention yet, like this all in one gadget that is compatible with Arduino IDE: https://www.amazon.com/gp/product/B08CKJKP9Y

[Battery Balance]

Originally Posted by Statistical

That was a long winded non-explanation. It is paralleling LFP and lead acid. Not sure there is an ABYC requirement against that but it is not a good idea. Saying there are similar products misses the point. Yes products to parallel house and start battery have existed for decades. They predate lithium house batteries.

Regarding parallel LFP and SLA..
Please note there is no such guidance from ABYC.
ABYC has guidance for Lithium batteries only in chapter 13 (E13) and they describe different chemistry of lithium. Appendix describe terminal runaway (valid for NMC chemistry only).

There is a misunderstanding about how to interpret the statement about not mixing chemistry (13.6.6.2) attached below.

What this is about, is to not mix different lithium chemistries in the same battery bank. (E13 is only discussing lithium)
LFP cells must not be mixed with NMC. They are also addressing 12 V or 24 V battery packs, mentioned in previous page (E13).
24 V of NMC battery pack must not be paralleled with 24 V of LFP. (LFP and NMC have different voltage for both cells and battery pack and must be charged by different voltage).

NMC has 3.7 V , LFP has 3.3 V and SLA has 2.1 V.
Four cells series of LFP and six cells series of SLA require same charge voltage: 14.2 - 14.4 V.

That's why LFP and SLA can be charged by 14.2 V (Bulk) via splitter or via voltage relay (Cyrix or X2).
However, LFP and SLA have different float voltage. Actually, the best is to not float charge lithium nor absorp charge lithium. X2 BMS is the only system on the market which has as standard to disconnect lithium when it’s fully charged to avoid float and absorp charge (valid for all chargers with or without remote). X2 system will allow all chargers to float charge SLA.

[Battery Balance]

Regarding compliance with ABYC...
- Will a homemade "Arduino BMS" comply with ABYC?
If you as an amateur designer claim that it does?
- Will the insurance company approve such device / lithium system?
Another consideration may be how you convince a buyer of a homemade BMS for the lithium system, when time to sell the boat.

Some other comments regards to discussion in this thread:
X2 BMS Pro has CAN (two RJ45 ports). However, despite this feature, we agree to the comment that CAN is not needed to control the regulator. You can simply control via remote (high/low signal to shut down the regulator), but if the system is dual (= incl charge relay), the AFD must pre-disconnect before the charge relay opens. Valid for all triggers such as voltage and temperature. (ABYC requires that the BMS has temperature protection).

Regarding cell balancing, the cells require recurring balancing, especially if high current is used during charging or discharging. (Our experience of several hundreds system sold since 2017 - at the beginning without balancing feature).
Note that the cell voltages only differ by +/- 0.005 V even if the battery is strongly unbalanced when you measure when the voltage is not at its highest. We have noticed that 99% of users do NOT measure when peak voltage (14.2 V for 12 V systems) and then report that the battery only has 5 mV delta (measured at 13.3 - 13.8 V for the battery).

Lithium batteries should not be stored fully charged but at a lower SOC.
Keeping a battery at elevated voltage (like 13.8) when fully charged is even worse than storing fully charged. A float voltage of 13.8 V will shorten the lifespan. It is better to set it to 13.4 V (Victron has 13.5 V as standard). However, the best charge is to turn off the charger when battery is full and let the voltage drop and also top off a few amphours.

We hope these comments contribute to the discussion. However, we will not answer any follow-up questions.

[s/v Jedi]

ABYC is crystal clear: different chemistries is LA vs LFP.

You are not to mix LA with LFP in the same battery bank.

Also, not sure if you addressed me, but I am not an amateur, I am a retired electronics engineer and micro electronics designer, i.e. I designed what is inside microchips.

[Battery Balance]

You are wrong regarding different battery chemistry. You have not read E-13 and therefore misunderstand what Note 3 is referring to. If the question is whether Lead-acid and LFP are different chemistries, then it is very clear that they are different. But it is crystal clear that the Note 3 refers to lithium only (and there are more than ten different lithium chemistries).

I will explain further on and referring to the ABYC definitions:

ABYC Note 3: "Mixed battery chemistries are not suited for installation in the same battery bank"

Means that the same battery bank should not consist of different chemistries.

ABYC defines Battery Bank: "-two or more batteries connected in series to provide higher voltage, or in parallel to provide increased capacity"

The same Battery Bank is NOT a lithium Cell Pack and a Lead-Acid battery (often placed in a different compartment). These are two different battery banks according to ABYC definition.

Note 3 means that a lithium Cell Pack eg 3P4S as same battery bank must consist of cells of the same chemistry (actually also the same brand and size).
Note 3 can also mean that the 12 V drop-in (defined as block according to ABYC) must consist of the same chemistry in the same battery bank (actually also the same brand and size).

ABYC definitions and standard 13.6.8, attached below

Definition stated in the E-13 LITHIUM ION BATTERIES standard:
13.1.1 This standard addresses selection and installation of lithium ion batteries on boats, lithium ion battery system design (e.g., house battery bank, cranking, propulsion), and manufacturer safety information
13.4.2 Battery - a collection of cells (or blocks) wired in series (or series/parallel) and constituting a single physical unit.
13.4.3 Battery Bank - two or more batteries connected in series to provide higher voltage, or in parallel to provide increased capacity.
13.4.5. Battery Cell – a single unit device which converts chemical energy into electrical energy that is the fundamental building block of a lithium ion battery.
NOTE: A battery cell is designed to be rechargeable by way of a reversible chemical reaction.
13.4.6. Battery Management System (BMS)-a system designed to protect a lithium ion battery battery bank from hazardous situations such as overcharging or overdischarging, charging or discharging in high and low temperatures, etc

13.6.8. Battery Bank
13.6.8.1 Series and paralleling installations for battery banks shall comply with the battery manufacturer’s recommendations.
13.6.8.2. If a battery manufacturer specifies a voltage deviation limit between individual battery voltages, it shall be met before the batteries are paralleledor connected in series to prevent excessive battery to battery current.
NOTES:
1. If batteries are paralleled in an unbalanced state, extremely high paralleling currents can flow. If used, automatic paralleling devices should have an appropriate current-limiting capability. Manual switches, (e.g., a 1, 2, both switch or on/off switch) and automatic paralleling devices may not be appropriate.
2. Special attention to balancing is very important in larger battery banks.
3. Mixed battery chemistries are not suited for installation in the same battery bank

[Statistical]

ABYC defines Battery Bank: "-two or more batteries connected in series to provide higher voltage, or in parallel to provide increased capacity"

Yeah like putting a LFP and lead acid battery in parallel.

Arguably I see no good from parallelling a LFP and lead acid battery. Aside from that the BMS looks interesting with lots of useful features.

[Battery Balance]

Jedi, the amateur wording is aimed at any "non-professional" designing a BMS. (Amateur means not professionally designing and selling BMS).

Feel free to answer the questions about an Arduino BMS that you or someone else designs will comply with ABYC? What do boat insurance companies say about home-built Arduino BMS? What does a potential boat buyer say regarding lithium battery with homemade Arduino BMS?
I ask the questions because this thread has concerned systems that will comply with ABYC.

[Battery Balance]

Originally Posted by Statistical

Yeah like putting a LFP and lead acid battery in parallel.

Arguably I see no good from parallelling a LFP and lead acid battery. Aside from that the BMS looks interesting with lots of useful features.

I agree, LFP and Lead-Acid must not be connected in the same battery bank.

What I am trying to explain is what ABYC means by chemistry in Note 3. To understand, the whole standard must be read. However, it appears that no one commenting has read the entire Standard E-13.

Also note that ABYC in the standard E-13 Lithium Batteries does not mention Lead-Acid battery with a single word. However, other lithium chemistries are mentioned several times.