Epoch 460AH Marine V2

[Barking Sands]

Thanks for replying!
Here is a response from Ben S at Panbo that I got today.

It doesn't sound to me like you've done anything wrong. The V2 batteries are designed to create a single virtual battery composed of all the batteries in a bank. In that bank, you should (but currently can't) see bank details including total capacity, highest and lowest voltage cells, temperatures, etc. There is a communication issue with the battery and that's preventing that information from making it to Venus OS. So, for now all you see is summary data for the bank like SOC, voltage, and current. To confirm, the current values measured for the battery named Epoch should reflect your entire load on the batteries, not half as it would if only one battery were communicating.



I recognize this is frustrating and I'm working with Epoch on getting these issues resolved. I believe 2.3 is the current firmware version but I'm not near a battery right now to confirm.



-Ben S.

Ben is right. On my old v1 it would show 2 of 2 online and totalized AH etc. For this battery it makes one large battery and I doubt that info will appear because its compiled and transmitted as a single battery. There is quite a bit of info in the cerbo but the one thing I dont see is the highest a lowest cell voltage. But of course that info is present in the app in much greater detail than just highest/lowest. The warnings for all these items are present. The good news is that since the battery now has OTA capabilities all changes can be uploaded in the future. BTW..in your picture, click the battery line. That will open up to additional information shown in the pics below.

Be sure you have DVCC on, controlling BMS set to Epoch, Battery monitor set to Epoch, set Limit max charged voltage in DVCC to 14.2. Dont be surprised if on the first few cycles you get the red light next to the dip switches and overvolt warning in the Cerbo. It usually takes 2 to 3 charge cycles to get these larger batteries cells aligned. If you get that just do a heavy discharge to clear the warning which will rest around 13.8 volts as it falls quickly.

The battery appears to have some neat features. Some I am still trying to wrap my head around. Some of the operation is SOC targeted. CCL (charge current limit) is dynamic based on conditions and SOC it appears. So if you are at say 50% SOC on your parameters page you will see max charge current limit maybe 460 amps for a pair, I cant remember. But as the battery gets charged to near full 99% SOC CCL will be pulled back until 14.2 is hit and then CCL will go to 0. Even though CCL is at 0 the battery is still fed a small current and held at 14.2 for some amount of time. Then the battery appears to have a slow draw down to around 98%. If SOC gets to 90% it appears CCL is raised and charging begins again. So on first appearance it would seem the battery should stay between 99% and 95% most of the time after a full charge cycle. But I still need to do some more testing. This is just initial observations, and it may be more dynamic that that.

One other thing that is new, and again I have to confirm this, is that when networked, with or without cerbo, the batteries appear to have active load sharing. It appears that the batteries are managed in such a way that it either targets the 415.5/460ah monitor from each battery to keep them well aligned, or its managing load sharing well enough that it held those parameters exactly the same in a 230 ah round trip down and up. As I monitored the 2 batteries in the app it would inevitably show one battery with a slightly higher current than the other, but after a few seconds this scenario would flip flop and the other battery would have a slightly higher load. The batteries would bounce back and forth the entire trip up and down discharge and charge.

 

[MV Cricket]

Ben is right. On my old v1 it would show 2 of 2 online and totalized AH etc. For this battery it makes one large battery and I doubt that info will appear because its compiled and transmitted as a single battery. There is quite a bit of info in the cerbo but the one thing I dont see is the highest a lowest cell voltage. But of course that info is present in the app in much greater detail than just highest/lowest. The warnings for all these items are present. The good news is that since the battery now has OTA capabilities all changes can be uploaded in the future. BTW..in your picture, click the battery line. That will open up to additional information shown in the pics below.

Be sure you have DVCC on, controlling BMS set to Epoch, Battery monitor set to Epoch, set Limit max charged voltage in DVCC to 14.2. Dont be surprised if on the first few cycles you get the red light next to the dip switches and overvolt warning in the Cerbo. It usually takes 2 to 3 charge cycles to get these larger batteries cells aligned. If you get that just do a heavy discharge to clear the warning which will rest around 13.8 volts as it falls quickly.

The battery appears to have some neat features. Some I am still trying to wrap my head around. Some of the operation is SOC targeted. CCL (charge current limit) is dynamic based on conditions and SOC it appears. So if you are at say 50% SOC on your parameters page you will see max charge current limit maybe 460 amps for a pair, I cant remember. But as the battery gets charged to near full 99% SOC CCL will be pulled back until 14.2 is hit and then CCL will go to 0. Even though CCL is at 0 the battery is still fed a small current and held at 14.2 for some amount of time. Then the battery appears to have a slow draw down to around 98%. If SOC gets to 90% it appears CCL is raised and charging begins again. So on first appearance it would seem the battery should stay between 99% and 95% most of the time after a full charge cycle. But I still need to do some more testing. This is just initial observations, and it may be more dynamic that that.

One other thing that is new, and again I have to confirm this, is that when networked, with or without cerbo, the batteries appear to have active load sharing. It appears that the batteries are managed in such a way that it either targets the 415.5/460ah monitor from each battery to keep them well aligned, or its managing load sharing well enough that it held those parameters exactly the same in a 230 ah round trip down and up. As I monitored the 2 batteries in the app it would inevitably show one battery with a slightly higher current than the other, but after a few seconds this scenario would flip flop and the other battery would have a slightly higher load. The batteries would bounce back and forth the entire trip up and down discharge and charge.

Great info here! Thanks!
Now I just have to find the "Controlling BMS" option in the Ekranos. That might pop up when the Victron sees the batteries. Have to wait till I get to the boat to find that out.

 

[Marco Flamingo]

So in my book a power system that can fry an alternator is non-compliant. One way or another the designer needs to deal with it. They can use clamping diodes, DC/DC converters, parallel LA batteries, early warning alternator shutdowns.... take your pick of these and unimaginable other ways. But you have to do it.

I'm sure that the vast majority of fried diodes precede LFP batteries. Even today, I would guess the 1/2/Both/Off switch is still the winner for fried diodes. Yet I've never heard that the traditional switch is ABYC non-compliant.

I think that, given the range of possible electrical disasters onboard, fried diodes aren't that problematic. Improper fusing (leading to fires), improper galvanic isolation (leading to sinking), etc. are much bigger concerns. For many boats, not charging because of blown diodes isn't much of an issue. No AC (whaaat?) Icecream melts in the freezer (whaaaa!). Maybe those are "problems" until back in port, assuming no spares/repairs onboard. A definite inconvenience for most diesel coastal cruisers.

With my solar, I think I could cruise three days, including three starts, without needing the alternator if the diodes blew from LFP overcharge of the bank. I once went two days with no charging until I could get into Uclulet for an alternator repair and that was with only 2 group 27 lead acid. Just takes a little electrical belt-tightening (not the alternator belt, yuk yuk).

The concerned language about BMS faults and the possible diode problem always seems to assume an LFP battery, not a bank of LFP batteries. If one cell in one battery hits overcharge, and that battery's BMS shuts down, is there any effect on the remaining batteries that would be a precursor to them shutting down? If not, that would mean the diode protection of having LFP batteries in parallel is similar to the protection afforded by "lead acid batteries in parallel." I guess I'll find out.

 

[guy with a boat]

… Many are using basic Balmar MC618 programmed to 13.8 absorption (13.8 for a bit extra room) and 13.5 float for the Epoch v1. Provided the regulator is working then FCP is never hit. …

Why do these numbers differ from the Epoch website recommendations?

This is from the Epoch website charging instructions for V2:

• To properly charge your Epoch Batteries, you will want to verify that any charging component in your system is capable of being programmed for the following specifications. Charging components can include, but are not limited to converters, inverter chargers, solar charge controllers, DC to DC chargers, etc.
• Bulk/Absorption: 14.2V – 14.6V
• Absorption Time: Two batteries in parallel connections require 30 minutes 200Ah
• Float: 13.4V – 13.8V

 

[Barking Sands]

Why do these numbers differ from the Epoch website recommendations?

This is from the Epoch website charging instructions for V2:

• To properly charge your Epoch Batteries, you will want to verify that any charging component in your system is capable of being programmed for the following specifications. Charging components can include, but are not limited to converters, inverter chargers, solar charge controllers, DC to DC chargers, etc.
• Bulk/Absorption: 14.2V – 14.6V
• Absorption Time: Two batteries in parallel connections require 30 minutes 200Ah
• Float: 13.4V – 13.8V

I was talking about a v1. It also depends on how you use them. It gets complicated on one battery vs multiple in parallel vs multiple in series or if it's a continously cycled system such as a boat or camper in constant use vs a single use per charge such as golf carts or trolling motors. Despite what many websites say about charging voltages...best practices can be very use case specific. Also Epoch has many battery lines/models that are slightly different in requirements.

 

[guy with a boat]

I was talking about a v1. It also depends on how you use them. It gets complicated on one battery vs multiple in parallel vs multiple in series or if it's a continously cycled system such as a boat or camper in constant use vs a single use per charge such as golf carts or trolling motors. Despite what many websites say about charging voltages...best practices can be very use case specific. Also Epoch has many battery lines/models that are slightly different in requirements.

Okay; I guess I lost track of which version was being discussed at that point.

For a V2 460AH, do you agree with the website settings? Its seems the upper limit recommended of 14.6v would trigger the charge shutoff being discussed. Just trying to understand all of this a little better.

Thanks for all the good writeup and discussion.

 

[Barking Sands]

Okay; I guess I lost track of which version was being discussed at that point.

For a V2 460AH, do you agree with the website settings? Its seems the upper limit recommended of 14.6v would trigger the charge shutoff being discussed. Just trying to understand all of this a little better.

Thanks for all the good writeup and discussion.

Yes...if using CAN control you would set 14.2. If using standard charge profiles 13.8 to 14.2 absorption and 13,4 or 13.5 float. If you had this battery in a cart that was going to be carted out for ice fishing it would be charged with any dumb charger up to 14.6 and it would cut the charger. No harm no foul there. But for a continuously cycled system that needs to operate in a completely consistent way we would need 14.2 as the upper limit.

 

[guy with a boat]

Yes...if using CAN control you would set 14.2. If using standard charge profiles 13.8 to 14.2 absorption and 13,4 or 13.5 float. If you had this battery in a cart that was going to be carted out for ice fishing it would be charged with any dumb charger up to 14.6 and it would cut the charger. No harm no foul there. But for a continuously cycled system that needs to operate in a completely consistent way we would need 14.2 as the upper limit.

Great info that makes sense. Thanks for the explanation.

 

[Barking Sands]

Great info that makes sense. Thanks for the explanation.

No problem. And for more clarity..apply it from the other direction. You have an ice fishing cart and a single use charger for your Lithium battery...and someone told you to use 14.2 absorption and 13.5 float. You would have no idea what that meant and that info would be pretty much useless. So, Manufacturer recommendations cover various uses.

 

[twistedtree]

I would sum it as: each lithium battery has a safe operating envelope. All charge sources must adhere to that safe operating envelope. Most people I have dealt with that have alternator issues or other issues had no idea any such envelope existed.

Very interesting. So E-13 is pretty explicit about operating envelopes and designing the system to stay within them. And it's explicit about BMS disconnects and the need to accommodate them. This would make the alternator problems you know of all non-compliant installations.

E-13 is a safety standard. It is definitely not an installation or design guide. There are installation and design requirements, but it's intentionally silent on HOW to accomplish things to not constrain implementations.

Although it's tempting to use a standard to address common installation issues and product field failures, it's really not the roll of a standard to do that. Especially when the installation error is already in violation of the standard.

 

[twistedtree]

The concerned language about BMS faults and the possible diode problem always seems to assume an LFP battery, not a bank of LFP batteries. If one cell in one battery hits overcharge, and that battery's BMS shuts down, is there any effect on the remaining batteries that would be a precursor to them shutting down? If not, that would mean the diode protection of having LFP batteries in parallel is similar to the protection afforded by "lead acid batteries in parallel." I guess I'll find out.

I think that's true for self-contained battery+BMS. But not true for battery packs plus an external BMS.

 

[rslifkin]

I think that's true for self-contained battery+BMS. But not true for battery packs plus an external BMS.

I'm not sure it's entirely true in any case, as some fault conditions (like a runaway alternator regulator) could potentially trip all of the batteries offline nearly simultaneously.

 

[Barking Sands]

I'm not sure it's entirely true in any case, as some fault conditions (like a runaway alternator regulator) could potentially trip all of the batteries offline nearly simultaneously.

Just a clarification. It could trip all the batteries charge mosfets to shut off, probably not simultaneously but in a fairly rapid cascade. Maybe 10 seconds, maybe 2 minutes. All discharge mosfets remain on and power to the ship remains uninterrupted.

 

[Barking Sands]

More on the V2 operation. I am still not 100% sure of anything.
* Absorption: 14.2 (still need to derive absorption time)
* Float: Not completely sure. It may be 98% soc float and not voltage driven, voltage/current throttle up and down to maintain 98% SOC? Ill have to determine more long term to see if SOC is held or if it drifts.
* Re-bulk: 90% SOC. ( CCL is raised to full values at 90% SOC)
* There seems to be battery to battery load management during charge/discharge. The voltage and amperage seems to be throttled between batteries to align SOC. Note in pic #5 the 457.2/460 and the 457.7/460 are not aligned. As discharge happens the voltage and amperage between batteries is varied to align those 4xx.x/460 parameters.

I am still trying to derive whats going on. It does seem quite a bit different.

 

[DDW]

I don't see the fact that it shuts down only the charge mosfets as a comforting safety feature for the alternator. In a battery only system, the charge amperage would be at a low level when it disconnects and the field flux also, so the regulator may be able to react fast enough to dump the energy. But in a more typical system there are other loads, and perhaps quite heavy loads. As a scenario, you are running your microwave to cook lunch, the battery is at full charge and so it shuts the charge circuit off. The alternator continues to put out near maximum current to keep the microwave going. Then the microwave shuts off suddenly. To the alternator, this is the same thing as the battery charge circuit disconnecting at very heavy battery charge.

So the full charge protection may protect the battery but destroy the alternator and anything else connected to it. You still need another place to dump the energy.

Does anyone have specifications on a DC-DC charger that suggest it can perform this function? You would need to know the dynamic input regulation characteristics, not something I've ever seen published. If it does not ramp its demand fast enough, the spike resulting from a BMS disconnect may well take it out along with everything else.

 

[Barking Sands]

I don't see the fact that it shuts down only the charge mosfets as a comforting safety feature for the alternator.

Its not a comforting safety feature...its just a feature to be known and addressed for via system set up.

In a battery only system, the charge amperage would be at a low level when it disconnects and the field flux also, so the regulator may be able to react fast enough to dump the energy. But in a more typical system there are other loads, and perhaps quite heavy loads. As a scenario, you are running your microwave to cook lunch, the battery is at full charge and so it shuts the charge circuit off. The alternator continues to put out near maximum current to keep the microwave going. Then the microwave shuts off suddenly. To the alternator, this is the same thing as the battery charge circuit disconnecting at very heavy battery charge.

A proper charge profile should not allow this to happen without some additional failure such as an external alternator regulator failure. Is the blame of the failure of an external regulator now to be shifted to the battery?
Alternator regulator failures of that nature would affect every battery negatively in some way. All of these scenarios require a safe operating envelope. I just see it that some of those envelopes are just a bit fuzzier than others.

So the full charge protection may protect the battery but destroy the alternator and anything else connected to it. You still need another place to dump the energy.

FCP lithium batteries are no different than any other lithium battery that has limitations such as 14.6 pack and 3.65 cell overvolt, temps and charge current limits. All of those parameters being exceeded will result in the same action: Charge mosfet disconnect. FCP is planned for and controlled for in exactly the same way provided those details are known.

 

[Marco Flamingo]

The most common scenario for the alternator to send bad juice to an LFP battery, resulting in a BMS shutdown, would be if the alternator's diode bridge was malfunctioning/blown. Even though I've yet to read a credible report of a BMS shutdown/blown diodes issue, if a case were reported, it is most likely caused by the diodes being shot before a BMS shutdown, not caused by a BMS shutdown. I would guess that the BMS will get the blame from now on. The good news is that LFP batteries can save themselves from a diode failure and/or regulator malfunction. Not always the situation with lead, but we seem to have gotten used to dangerous lead acid failures even though they are more common, messy, and unhealthy than a BMS shutdown.* Personally, I'd rather blow the diodes.

Diode failure doesn't "destroy the alternator." Diodes are serviceable just like the alternator bearing, brushes, etc. When bearing, brushes or diodes fail, and they are all long-term wear items, the prudent plan is to rebuild all at the same time, leading to the common claim that replacing diodes is expensive. Just a diode bridge for my alternator is $80 and supposedly a DIY repair. But I can't imagine a situation where I would want to undertake field triage instead of simply taking it to a rebuild shop.

* I have no idea if this is true, so it fits right into a discussion of the dangers of LFP batteries.

 

[twistedtree]

I'm not sure it's entirely true in any case, as some fault conditions (like a runaway alternator regulator) could potentially trip all of the batteries offline nearly simultaneously.

Yes. Also high current loads which are fine spread across two batteries, but overload when only one battery is left online. There are a variety of cascading disconnect possibilities.

 

[DDW]

A proper charge profile should not allow this to happen without some additional failure such as an external alternator regulator failure. Is the blame of the failure of an external regulator now to be shifted to the battery?
Alternator regulator failures of that nature would affect every battery negatively in some way. All of these scenarios require a safe operating envelope. I just see it that some of those envelopes are just a bit fuzzier than others.

Regulator failure in an LFP system is likely to have much greater consequences than in an LA system, and yes, the blame lies with the battery (or BMS). The failure is slower progressing, and more graceful with LA. The bits are part of the whole, and you'd like it to be as robust as possible. A runaway alternator will drive the system voltage high very quickly in an LA system, but you can catch that and electronics can catch that. I've seen in happen. No way you are going to catch the spike from a BMS disconnect, and that spike is potentially much more damaging.

Outside of a complicated system with all charge sources interconnected to the BMS, the only reliable safeguard seems to be to have an LA battery in the system on the same power bus. Avalanche diodes - by the manufacturer's own documentation - may not do it, DC-DC chargers might or might not - no one knows.

 

[Barking Sands]

Regulator failure in an LFP system is likely to have much greater consequences than in an LA system, and yes, the blame lies with the battery (or BMS). The failure is slower progressing, and more graceful with LA. The bits are part of the whole, and you'd like it to be as robust as possible. A runaway alternator will drive the system voltage high very quickly in an LA system, but you can catch that and electronics can catch that. I've seen in happen. No way you are going to catch the spike from a BMS disconnect, and that spike is potentially much more damaging.

Outside of a complicated system with all charge sources interconnected to the BMS, the only reliable safeguard seems to be to have an LA battery in the system on the same power bus. Avalanche diodes - by the manufacturer's own documentation - may not do it, DC-DC chargers might or might not - no one knows.

I am not opposed to a LA battery inline, but ABYC currently forbids that?
A full CAN controlled system can still be overvolted by malfunctions or bad programming. So it looks like we are all back to lead because we need more than just good practices and must protect and plan for failures after failures.
Well I'm not going back!

edited...I still blame a runaway alternator on the runaway alternator.
I am ok with good practices, good equipment and an APD.

 

[rslifkin]

I am not opposed to a LA battery inline, but ABYC currently forbids that?
A full CAN controlled system can still be overvolted by malfunctions or bad programming. So it looks like we are all back to lead because we need more than just good practices and must protect and plan for failures after failures.
Well I'm not going back!

They don't allow it in parallel, but it's fine to feed the alternator to a lead acid start battery and then use a DC to DC charger to charge the LFP bank.

 

[Barking Sands]

They don't allow it in parallel, but it's fine to feed the alternator to a lead acid start battery and then use a DC to DC charger to charge the LFP bank.

Thats how mine is now

 

[NoRain]

This the problem though - all my charging sources go to the house bank, and then ACR to the start bank and thruster banks. Currently all AGM (lead carbon) but house going to Lithium, probably Epoch shortly. The reason for the above is that the house bank is where I need the amps….as many as I can jam in. So I do NOT want to short-change my house charging by having to use a DC-DC charger with say 50A charge current, vs my 2 x MultiPlus - 240A or my heavy duty alternators (rated at 200A each. And will run at 150A all day happily). The alts are controlled by Balmar 614’s with a centre fielder so I can push many many amps into the house while running. And this is the key point - I don’t want to - and don’t see why I should have to - run my gen to do major charging when I have almost free 300 A while running from one anchorage to another. That’s a lot of “free” power that would not get utilized in the scenario in #52 & 53 above. Even though it is not totally free, it’s a whole hell of a lot better to have the house charged when I drop anchor and not have to run gen (diesel, noise etc etc) to charge. No solar yet, future project.

So I’m happy to de-tune the alts so they don’t smoke, and take measures to ensure they don’t get smoked by a BMS disconnect, and replace my ACR’s with DC-DC for start and thruster banks.

By the way, I think this would be a preferred configuration for anybody in a similar situation, except for the complications introduced by the factors discussed in this thread and others - mostly unintended BMS disconnect (redundant I know ) frying alternators and possibly compromising ship’s systems (eg “black” ship syndrome).

 

[Barking Sands]

NoRain...the main reason I run and Orion 50 amp DC2Dc is because it a good match for my 100 amp alternator. if I had large alternator I would be running it in the reverse as well (lfp first)

 

[NoRain]

Roger that, big difference in configurations indeed. Thx for the reply.

 

[DDW]

The uncertainty in behavior of the DC-DC in the event of a disconnect argues for a simple diode or FET bridge. The alternator can charge the LFP house bank directly, and still have a very simple and reliable path to dump energy if a disconnect occurs.

 

[twistedtree]

Regulator failure in an LFP system is likely to have much greater consequences than in an LA system, and yes, the blame lies with the battery (or BMS). The failure is slower progressing, and more graceful with LA. The bits are part of the whole, and you'd like it to be as robust as possible. A runaway alternator will drive the system voltage high very quickly in an LA system, but you can catch that and electronics can catch that. I've seen in happen. No way you are going to catch the spike from a BMS disconnect, and that spike is potentially much more damaging.

Outside of a complicated system with all charge sources interconnected to the BMS, the only reliable safeguard seems to be to have an LA battery in the system on the same power bus. Avalanche diodes - by the manufacturer's own documentation - may not do it, DC-DC chargers might or might not - no one knows.

The other way to deal with this is to use batteries that have some sort of Allow-to-Charge signal, either via discrete wires, canbus, or whatever. That should trigger well before a battery gets into trouble and does any disconnect, and can be used to turn off any charging sources well before there is any problem. It would seem pretty simple for drop-ins to add a terminal with a couple of connections, and completely solve this problem. But for whatever reason, they don't.

 

[twistedtree]

Just a clarification. It could trip all the batteries charge mosfets to shut off, probably not simultaneously but in a fairly rapid cascade. Maybe 10 seconds, maybe 2 minutes. All discharge mosfets remain on and power to the ship remains uninterrupted.

Assuming that's how the battery is designed/built.

 

[twistedtree]

I don't see the fact that it shuts down only the charge mosfets as a comforting safety feature for the alternator. In a battery only system, the charge amperage would be at a low level when it disconnects and the field flux also, so the regulator may be able to react fast enough to dump the energy. But in a more typical system there are other loads, and perhaps quite heavy loads. As a scenario, you are running your microwave to cook lunch, the battery is at full charge and so it shuts the charge circuit off. The alternator continues to put out near maximum current to keep the microwave going. Then the microwave shuts off suddenly. To the alternator, this is the same thing as the battery charge circuit disconnecting at very heavy battery charge.

So the full charge protection may protect the battery but destroy the alternator and anything else connected to it. You still need another place to dump the energy.

Does anyone have specifications on a DC-DC charger that suggest it can perform this function? You would need to know the dynamic input regulation characteristics, not something I've ever seen published. If it does not ramp its demand fast enough, the spike resulting from a BMS disconnect may well take it out along with everything else.

That's a good example. Also consider an alternator that is charging batteries at full output, and the BMS trips because of a cell over temp....

All that said, I know that 5 or so years ago when working on T-13, and then E-13, alot of people (me included) were very worries about all sorts of unexpected BMS shutdown scenarios, dark ships, blown alternators and electronics, super-nova fires, specialized fire fighting apparatus, etc. In reality, very little of these fears have panned out, and what does exist, is was less frequent, and way less severe that everyone feared. A lot of this is because 99% of boat batteries are LFP which are very stable, and no more of a fire threat than a LA battery or your fuel tank. Some even argue that the BMS requirement in E-13 are excessive for LFP batteries. I don't mean to be cavelier about any of this, but I do think that if you put together a system that meets the E-13 requirements, it will be pretty darn safe.

Where people get into trouble is when they didn't make acommodations as they should have, or, as exposed by Ben Stein and some others, BMSes are disconnecting to provide charge control, not just to provide a safety backstop. It isn't necessarily incorrect behavior, but for many it is unexpected and messes up how their system was supposed to work.

 

[DDW]

The other way to deal with this is to use batteries that have some sort of Allow-to-Charge signal, either via discrete wires, canbus, or whatever. That should trigger well before a battery gets into trouble and does any disconnect, and can be used to turn off any charging sources well before there is any problem. It would seem pretty simple for drop-ins to add a terminal with a couple of connections, and completely solve this problem. But for whatever reason, they don't.

Definitely agree that this would be preferable, and adds very little complication since most external regulators already have a shut-down input. Instead we have the more sophisticated batteries with CAN interfaces to computers, to more serial com, to complex regulators. That is a lot of code and electronics from multiple vendors thrown at a simple problem, and does not make it more reliable.

I appreciate that in a well set up charging system the disconnect *should* never occur. However whenever possible systems should be made so that failure is graceful with little collateral damage. Old LA systems were better at this, and in that respect LFP are a step backwards. If you had a runaway regulator it might drive the voltage to 17V, most electronics can stand that for awhile. A battery switch disconnect could wreak havoc, but you can prevent that by not doing it, and at least know what happened if you did. The current drop in BMS are opaque black boxes, you don't really know what it is going to do or why it did it. They ought to at least have a logging function.