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

[s/v Jedi]

Originally Posted by Battery Balance

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.

No, you stated that they mean different types of Lithium chemistries and that it is okay to parallel LFP and LA and you were wrong.

You can ridicule Arduino all day but your BMS with PIC microcontroller… is just the same microcontroller as the Arduino family uses. Also, there are no testing and compliance requirements whatsoever for BMS’s. Don’t say I didn’t read ABYC documents because I am normally the one citing them here on the forum. I know exactly what is in them.

I also know that you are lucky that I don’t market/sell BMS’s

[CarlF]

I still don’t understand the ABYC’s safety concern about paralleling an LFA house bank and LA start battery. I realize that the LA battery might have a reduced life from a lower than ideal absorption charge voltage and that the start battery could be drained accidentally if no VSR relay is included. But this really isn’t a safety issue - which I thought was at the core of all ABYC standards.

Am I missing something?

[s/v Jedi]

Originally Posted by CarlF

I still don’t understand the ABYC’s safety concern about paralleling an LFA house bank and LA start battery. I realize that the LA battery might have a reduced life from a lower than ideal absorption charge voltage and that the start battery could be drained accidentally if no VSR relay is included. But this really isn’t a safety issue - which I thought was at the core of all ABYC standards.

Am I missing something?

It isn’t easy to make sense of what ABYC does. Most of the “volunteers” who work there are sent by their employers who have a stick in the fire.

That said, their recommendations are for “best practice”, not just to avoid certain death

[hjohnson]

Originally Posted by CarlF

I still don’t understand the ABYC’s safety concern about paralleling an LFA house bank and LA start battery. I realize that the LA battery might have a reduced life from a lower than ideal absorption charge voltage and that the start battery could be drained accidentally if no VSR relay is included. But this really isn’t a safety issue - which I thought was at the core of all ABYC standards.

Am I missing something?

What I don’t understand is why people go through all those machinations with VSRs and what not to maintain their starter, when an 18A Orion-Tr can be hard for less than $200. An 18A charger is more than enough to keep virtually any starter battery in its happy place. Does the VSR really save that much money, especially since the Lead Acid won’t be as well maintained?

[s/v Jedi]

Originally Posted by hjohnson

What I don’t understand is why people go through all those machinations with VSRs and what not to maintain their starter, when an 18A Orion-Tr can be hard for less than $200. An 18A charger is more than enough to keep virtually any starter battery in its happy place. Does the VSR really save that much money, especially since the Lead Acid won’t be as well maintained?

I think it is a form of unwillingness to agree with something and instead propose an inferior alternative which guarantees unlimited arguing

[Battery Balance]

Originally Posted by hjohnson

What I don’t understand is why people go through all those machinations with VSRs and what not to maintain their starter, when an 18A Orion-Tr can be hard for less than $200. An 18A charger is more than enough to keep virtually any starter battery in its happy place. Does the VSR really save that much money, especially since the Lead Acid won’t be as well maintained?

For most installations, the lead-acid battery will mainly serve to start the engine (12 V) or as an auxiliary for 24 V.
However, the lead-acid battery has other important tasks in the X2 system:

• Backup battery and will supply power together with all chargers
• Pre-charge to avoid damage the charge relay
• Protect from load dump, from chargers connected to charge bus (i.e. avoid transient voltage spike)
• Supply controllers with input power; to manage wind and hydro and not damage when BMS disconnect lithium.
• Allow chargers to show voltage when they are ON and thereby allow X2 BMS sensing charge.

If connect DC/DC like Orion Tr, you will not have these benefits.
DC/DC will charge by the alternator only (and optional by shore power charger if 2nd output). Consider how to keep the starter fully charged during winter storage. In a X2 system, the starter will be charged by all chargers including solar and other chargers like Wind and Hydro.
X2 system will use the charge relay to control X2 so no extra cost (spend $200 on a good BMS instead).

[Battery Balance]

Originally Posted by CarlF

I still don’t understand the ABYC’s safety concern about paralleling an LFA house bank and LA start battery. I realize that the LA battery might have a reduced life from a lower than ideal absorption charge voltage and that the start battery could be drained accidentally if no VSR relay is included. But this really isn’t a safety issue - which I thought was at the core of all ABYC standards.

Am I missing something?

You are right, LFP and lead-acid is not a safety issue.
The ABYC's safety concerns is about not charging between the lithium batteries (or cells) in the same battery bank (Note 1 regarding paralleling).

Another safety concern is if LFP chemistry is mixed with NMC chemistry in the same battery bank. Reason is that LFP and NMC must be charged with different voltage (note 3 regarding mixing chemistry). Another fact is that LFP and NMC can charge each other (Note 1 and 3).
ABYC spending two pages at NMC chemistry and concerns regarding terminal runaway (NMC can be used for 48 V, but not for 12 V and rarely for 24 V)

Please note the fact, that 12 V (or 24 V) drop-in batteries (blocks) have internal BMS that can disconnect each individual battery. If such event, when a battery disconnect and then reconnect, the other paralleled lithium batteries can charge the reconnected battery (Note 1). Lithium can easily charge Lithium but rarely lead-acid. Drop-in batteries normally have internal resettable fuse as protection but will still create an issue when triggered.

What happens if paralleling a lead-acid battery with lithium (LFP block) in the same battery bank ie. sitting in the same compartment and no relay / isolation in-between? The answer is “nothing” as long as lithium is not discharged below 20% SOC. The lead-acid will always be fully charged due to lithium has higher voltage in the range of SOC 20 - 100%.

ABYC's 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

[s/v Jedi]

I had to dig it up but here is the diagram for the DIY BMS I designed. All these parts are off the shelf Amazon.com available.

[hjohnson]

Originally Posted by Battery Balance

For most installations, the lead-acid battery will mainly serve to start the engine (12 V) or as an auxiliary for 24 V.
However, the lead-acid battery has other important tasks in the X2 system:

• Backup battery and will supply power together with all chargers
• Pre-charge to avoid damage the charge relay
• Protect from load dump, from chargers connected to charge bus (i.e. avoid transient voltage spike)
• Supply controllers with input power; to manage wind and hydro and not damage when BMS disconnect lithium.
• Allow chargers to show voltage when they are ON and thereby allow X2 BMS sensing charge.

If connect DC/DC like Orion Tr, you will not have these benefits.
DC/DC will charge by the alternator only (and optional by shore power charger if 2nd output). Consider how to keep the starter fully charged during winter storage. In a X2 system, the starter will be charged by all chargers including solar and other chargers like Wind and Hydro.
X2 system will use the charge relay to control X2 so no extra cost (spend $200 on a good BMS instead).

I guess I really just don’t see most of those as significant benefits in a well designed system.

* My BMS knows when the charging sources are on, because it commanded them to be on.
* A disconnect is highly unlikely because it will command the charging sources to turn off, including the alternator, before it actually triggers the disconnect.
* The precharge for the inverter is handled by a simple precharge circuit based on what amounts to a 555 timer and a high power resistor.
* I don’t have wind/hydro generators, but as long as they have an enable input, the BMS OK circuit can enable/disable them as need be.

Yeah, I don’t have automatic failover to my lead acid battery, but if I really had to I do have a 2AWG cable I can install between my alternator and starter solenoid to achieve it. In that mode, my solar and alternator will operate in limp mode and get me home. Hell, if my BMS takes a dump, I can override the contactors (thanks to the knob on the 7713) and just manually keep an eye on the lithium as I head home.

I get that it comes from a different philosophy, but it seems to me to not have kept up with the technology.

[rgleason]

Guys, I have been following this and will read it all again later, but I have a few comments/questions.


1. hjohnson I do get your point about failover and that it is very infrequent or never, and you know my thoughts about dealing with a boat blackout while moving (night, navigation, storm) when there are other things that need to be dealt with. I don't want find myself in this position. This is why I designed the modified 3way switch to be able to shift all loads over to the SLA battery easily.


2. jedi Thank you for posting your reference diagram for diybms. In looking at it I see that I have most of the parts except what I think is a small screen for showing historical cell data? The wiring diagram looks pretty straight forward, and the only issue for me would be getting started and programming. I might want to add an emergency switch for quick blackout response.


3. BatteryBalance I need to review the BatteryBalance wiring diagram again, but separate charge and load buses each with an appropriately controlled relay plus a third emergency relay to shift the loads onto the SLA are another approach to prevent blackout. I believe the nav instruments and lights will have a brief interruption in any case. The BMS controlled heavy duty relay between LFP and FLA/SLA with some form of equalizing capacitor inside the BMS to reduce sparking when voltages differentials are high (and for inverters), seems like a reasonable response to the issues of paralleling different batteries, but is this a reliable approach over the long term, for paralleled batteries? This is also used in the REC BMS and TAOS BMS but only for the inverter turning on. These 3 BMS have a reasonably sizeable price range, with BatteryBalance being highest and REC BMS lowest, of course equipment needed is somewhat different.


4. The way things stand now, ABYC has standards that insurance companies would like to follow and the BMS's are manufactured to some standard, but with no independent certification that they are ABYC conformant, leaving it up to the boat owner to make the right choices for equipment. I actually don't think this situation is that different than a sound DIY BMS install reviewed by a knowledgeable Marine LFP Technician, but the insurance co's might not see it that way. The Insurance Co's are relying on some "expert" in both cases.

[Statistical]

Originally Posted by rgleason

3. BatteryBalance I need to review the BatteryBalance wiring diagram again, but separate charge and load buses each with an appropriately controlled relay plus a third emergency relay to shift the loads onto the SLA are another approach to prevent blackout. I believe the nav instruments and lights will have a brief interruption in any case. The BMS controlled heavy duty relay between LFP and FLA/SLA with some form of equalizing capacitor inside the BMS to reduce sparking when voltages differentials are high (and for inverters), seems like a reasonable response to the issues of paralleling different batteries, but is this a reliable approach over the long term, for paralleled batteries? This is also used in the REC BMS and TAOS BMS but only for the inverter turning on. These 3 BMS have a reasonably sizeable price range, with BatteryBalance being highest and REC BMS lowest, of course equipment needed is somewhat different.

There is no separate third emergency relay that I can tell. Just a load & charge relay meaning the LA is paralleled all the time except when the charge relay is open.

https://batterybalance.com/download/...24-fact-sheet/

I can't link to the user manual because it is password protected which is just a huge red flag to me. I have never seen any marine company prohibit non-customers from reading owners manuals.

Personally I just want a starter battery to be a starter battery. It has one job which is start the engine. Charging it by a simple DC to DC charger keeps that entire subsytem super simple and simple is good. Last thing I would want is some computerized system "helping" and draining the starter battery which wouldn't power household loads for very long so now I have no electrical power and no functional engine.

[s/v Jedi]

Originally Posted by Statistical

There is no separate third emergency relay that I can tell. Just a load & charge relay meaning the LA is paralleled all the time except when the charge relay is open.

https://batterybalance.com/download/...24-fact-sheet/

I can't link to the user manual because it is password protected which is just a huge red flag to me. I have never seen any marine company prohibit non-customers from reading owners manuals.

Personally I just want a starter battery to be a starter battery. It has one job which is start the engine. Charging it by a simple DC to DC charger keeps that entire subsytem super simple and simple is good. Last thing I would want is some computerized system "helping" and draining the starter battery which wouldn't power household loads for very long so now I have no electrical power and no functional engine.

And you are absolutely right. If one needs a battery to absorb a surge (caused by improper operating procedures imho) then just use an additional small AGM battery like the ones used in alarm systems or even a motorcycle.

[rgleason]

Perhaps that idea of using a small sacrificial motorcycle FLA which will degrade over time is a good one. I just wonder a little about how quickly it will develop an internal short.


The use of a small FLA battery might simplify the system and reduce the need to have the BMS provide an interrupt the regulator field. This might be a cheap way for Drop in LFP to work. Would ABYC have a problem with that approach? Every 3-4 years you just replace the LFP battery.

[s/v Jedi]

Originally Posted by rgleason

Perhaps that idea of using a small sacrificial motorcycle FLA which will degrade over time is a good one. I just wonder a little about how quickly it will develop an internal short.


The use of a small FLA battery might simplify the system and reduce the need to have the BMS provide an interrupt the regulator field. This might be a cheap way for Drop in LFP to work. Would ABYC have a problem with that approach? Every 3-4 years you just replace the LFP battery.

I have a cheap Chinese AGM motorcycle battery in my dinghy where it has been abused for years, receiving zero love and only a bit of charge when the outboard runs. It’ll be flat first time I start the outboard again so I’ll pull the cord instead, but like every year before I expect it to start the motor when I head back aboard.

Considering that leaving AGM discharged in a hot dinghy for months on end is the worst treatment possible, while being fully charged is the best treatment possible, I think it will do well

But I see zero reason for it. Stop the charging when the BMS warns about it instead so that you can prevent the HVC event instead of having to deal with the damaging effects of it. I don’t see why this even needs so much reasoning as I thought it to be something completely clear to everyone

[rgleason]

S/v Jedi. I agree, Thanks for the example.

but if someone wants to use somethimg like Battleborn drop-ins, an agm motorcycle battery to help protect a balmar or wakespeed external regulator would be better. Would that meet ABYC?

- Not something I want to do because I would like to charge at .5C at times.