Epoch 460AH Marine V2

[Barking Sands]

The updated version of the 460ah Marine battery is out. It is an incremental upgrade over some of the quirks of the V1.

* It has the ability to have OTA (over the air) updates for EMS and BMS software
* charge profile to Victron is supposed to be a more typical 14.2 absorb and 13.5 float (I havent had the chance to test that yet to confirm)
* Ammeter has a .4 amp detection threshold which is a big improvement over the V1 which was 1.4 amps. This should help SOC accuracy over time. For reference the Victron shunts come preset to .1 amps.
* Full charge protection raised from 14 volts to 14.3
* Full charge protection clears at roughly 13.7 volts instead of 13.35
* The bluetooth module is actually mounted in the new remote screen/gauge. This should improve bluetooth issues for campers and larger boats.
* You can now have up to 16 batteries in parallel with comms
* New fuse that is 400A and very slow blow. I dont know the specs but I tested 400-585 amps for around 30 seconds today and the fuse did not blow. My tester was a crude carbon pile load so it was a bit erratic.
* 24 and 48 volt versions out next month.
* Remote on off switch is on a 37 foot lead.

The inside is a masterpiece.

 

[rslifkin]

I'd seen that this was out, but this is definitely the most detail I've seen on what they updated. Definitely sounds like some very helpful changes, especially the lower amp threshold for measurement.

Any thoughts on whether the SOC estimate from 2 or 3 of these in parallel will be good enough (assuming "idle" draw isn't below the measuring threshold) to not need a smartshunt in the system to track the SOC separately?

 

[Barking Sands]

I'd seen that this was out, but this is definitely the most detail I've seen on what they updated. Definitely sounds like some very helpful changes, especially the lower amp threshold for measurement.

Any thoughts on whether the SOC estimate from 2 or 3 of these in parallel will be good enough (assuming "idle" draw isn't below the measuring threshold) to not need a smartshunt in the system to track the SOC separately?

I think I would still use a Victron shunt. The main reason being is that the smart shunt SOC reset to 100% is configurable. The Epoch SOC reset is not. So there are conditions this might come into play, especially on solar. Just my opinion.

 

[Barking Sands]

Amazing

 

[Pprior]

These are definitely on the must purchase list.

 

[Barking Sands]

Experimenting with a pair now.

 

[tiltrider1]

What is the weight?

 

[Portage_Bay]

What is the weight?

The video in post #5 shows the specs. Weight is listed as 97 lbs.

 

[Barking Sands]

Pretty neat. Some things are different. Each batterycomes with a gauge. The bluetooth is contained in the gauge. You only need one gauge if the comms are in use and the gauge will totalize the batteries. So if you buy multiple batteries you essentially have spare gauges.

The decision to put the bluetooth in the gauge is likely driven by many campers and boaters who had batteries located in the bowels of the vessel and could not get signal. Now the gauge can be mounted in a living space and should get good signal. Even though only one gauge is used both batteries show up on bluetooth.

All comm plugs and buttons have been improved and hardened a bit more from the V1. The remote on/off is 33 feet.
The battery is now updateable by way of OTA updates should improvements be required.

The manual is more complete and shows dip settings for comms up to 16 in parallel. Of course at that point you should probably be going 24 or 48v. The 24v 230ah and 48v 100ah that occupy the exact same case will be shipping soon fyi.

 

[BDofMSP]

How long is the bluetooth/gauge wire?

 

[Barking Sands]

Actually I took some measurements in the video. Its kind of hard to explain. But keep in mind it can be extended with regular RJ45 cable/ connectors.
Sorry, had to remove video since they changed the method of doing the OTA. Now there is not long press on the OTA and you just click the OTA

 

[twistedtree]

What is the "Full Charge Protection" that you mentioned in the first post? What does that do and how does it work?

 

[Barking Sands]

What is the "Full Charge Protection" that you mentioned in the first post? What does that do and how does it work?

There are several batteries on the market that have this now. Im sure you know that typical "drop In" batteries have the now standard upper voltage protections of 3.65 cell voltage and 14.6 or 14.7 pack volts. The BMS monitors this and when the pack or cell reaches those limits the charge mosfet is shut off stopping the charge. The problem has been, especially in the camper world, that poor equipment or poor practices have conspired to hold the voltage just under these disconnect points. So, a battery could sit at 14.55 volts for days, weeks, months, years, many times at the dock or in storage. The common RV camper "converter" is one such piece of equipment that is standard on all but the most expensive RV's. When lithium hit the market the camper converters added a "lithium" preset that just outputs 14.6 volts because that was the number thrown around in the early days. No profile at all, essentially a power supply.

So Litime's newest units, Epoch on some of their models and a few others have added two additional monitoring criteria to the mix to monitor for this kind of condition.

On the Epoch V2 it looks like this: charge voltage at 14.3 or more enables the FCP. As charge current falls below 3.6 amps that tells the BMS that its fully absorbed at 14.3 or above. When those 2 conditions are met it will start a short time count of maybe 10 or 20 seconds and then the BMS will shut the charge mosfet. So there is no way to essentially hold these batteries at a excessively high voltage via poor equipment and/or bad set up. Something to note, you can still push the voltage past 14.3 if you wanted to as long as absorption was set to 14.6 or 14.7 because when the voltage passed the 14.3 mark it would still be charging with a much greater amperage than the 3.5 amps to set the second criteria. But once absorbed at whatever the final voltage destination was and amps fell below 3.6 for the time limit, then FCP will engage. The standard 14.6 and 3.65 safeties are still in place as well.

Obviously, this was to protect from warranty claims 2 or 3 or 4 years down the road due to poor practices and bad equipment. In the boat world I have found that the end users are MUCH more savvy and this kind of protection is many times not necessary. But I am sure you still see many discussions where it still is necessary. The camper world and other spaces are more like the wild wild west. There are also many lithium users that are a single use per charge types. Think golf carts, ice fishing, trolling motors etc where they simply use the batteries for a day, go home and plug in the charger where it sits on charge until next use. Depending on the quality of the charger this of course may be less than ideal..lol. We are getting many people buying Epochs to replace their Battle Borns they have had for 2,3,4 years that no longer have capacity. I suspect it's because they have just been around longer, and we may be seeing the first casualties of such abuse. Hard to say with certainty. Some suspect the arrangement and nature of the cells that some parallel strings have lost connections due to vibrations. More people doing a teardown and postmortem would be required to be definitive

On these types of batteries with FCP that are in continuous use it will be imperative to have proper charge parameters set up from ALL charge sources. Inverter/charger, solar, alternator charging etc. In the case of the Epoch V2 the standard 14.2/13.5 is ideal and keeps the BMS clear of engaging the FCP. But the battery will ultimately protect itself in any case. The Victron Comms I believe also use the standard Victron protocol of 14.2/13.5 when run on the BMS-CAN. I have to verify that though. Going to the boat in a few to install these to monitor the details of how it works with the Cerbo in External Control.

 

[Marco Flamingo]

Interesting how the charging parameters for LFP have slowly changed. The excited numbers for how much LFP can accept have changed to what is best practices for longevity and economy. And it turns out my vintage Xantrex Freedom charger/inverter is back in the game even though it doesn't have a dedicated LFP charging program. By removing the battery temperature sensor, it runs a set program for each battery type: lead acid, gel, or AGM. When set to the AGM battery profile, that means acceptance is 14.3V and float is 13.3. Those seem to be basically the "new" numbers for LFP. I'm planning on hooking up a battery and watching the Bluetooth to see just what the Xantrex does when an LFP gets to 100 SOC per the BMS. Could be the old Xantrex will go another decade.

 

[Barking Sands]

Interesting how the charging parameters for LFP have slowly changed. The excited numbers for how much LFP can accept have changed to what is best practices for longevity and economy. And it turns out my vintage Xantrex Freedom charger/inverter is back in the game even though it doesn't have a dedicated LFP charging program. By removing the battery temperature sensor, it runs a set program for each battery type: lead acid, gel, or AGM. When set to the AGM battery profile, that means acceptance is 14.3V and float is 13.3. Those seem to be basically the "new" numbers for LFP. I'm planning on hooking up a battery and watching the Bluetooth to see just what the Xantrex does when an LFP gets to 100 SOC per the BMS. Could be the old Xantrex will go another decade.

I think much of this was driven by soc meters not reaching 100%. But as we all know now..for charging, voltage is the name of the game and soc meters can be easily thrown off. Ben Steins great testing proved that beyond doubt imo.

 

[tiltrider1]

I charge by voltage but I monitor consumption by my SOC. Fortunately my SOC resets everytime my batteries get fully recharged.

 

[tiltrider1]

I like the Epoch 460. At my age I am concerned with my ability to wrestle them in and out of the engine room. I’ll stick with my 260 Ah units for now. If I was in my 40’s I think I would get 3 of the Epoch 460’s.

 

[twistedtree]

There are several batteries on the market that have this now. Im sure you know that typical "drop In" batteries have the now standard upper voltage protections of 3.65 cell voltage and 14.6 or 14.7 pack volts. The BMS monitors this and when the pack or cell reaches those limits the charge mosfet is shut off stopping the charge. The problem has been, especially in the camper world, that poor equipment or poor practices have conspired to hold the voltage just under these disconnect points. So, a battery could sit at 14.55 volts for days, weeks, months, years, many times at the dock or in storage. The common RV camper "converter" is one such piece of equipment that is standard on all but the most expensive RV's. When lithium hit the market the camper converters added a "lithium" preset that just outputs 14.6 volts because that was the number thrown around in the early days. No profile at all, essentially a power supply.

So Litime's newest units, Epoch on some of their models and a few others have added two additional monitoring criteria to the mix to monitor for this kind of condition.

On the Epoch V2 it looks like this: charge voltage at 14.3 or more enables the FCP. As charge current falls below 3.6 amps that tells the BMS that its fully absorbed at 14.3 or above. When those 2 conditions are met it will start a short time count of maybe 10 or 20 seconds and then the BMS will shut the charge mosfet. So there is no way to essentially hold these batteries at a excessively high voltage via poor equipment and/or bad set up. Something to note, you can still push the voltage past 14.3 if you wanted to as long as absorption was set to 14.6 or 14.7 because when the voltage passed the 14.3 mark it would still be charging with a much greater amperage than the 3.5 amps to set the second criteria. But once absorbed at whatever the final voltage destination was and amps fell below 3.6 for the time limit, then FCP will engage. The standard 14.6 and 3.65 safeties are still in place as well.

Obviously, this was to protect from warranty claims 2 or 3 or 4 years down the road due to poor practices and bad equipment. In the boat world I have found that the end users are MUCH more savvy and this kind of protection is many times not necessary. But I am sure you still see many discussions where it still is necessary. The camper world and other spaces are more like the wild wild west. There are also many lithium users that are a single use per charge types. Think golf carts, ice fishing, trolling motors etc where they simply use the batteries for a day, go home and plug in the charger where it sits on charge until next use. Depending on the quality of the charger this of course may be less than ideal..lol. We are getting many people buying Epochs to replace their Battle Borns they have had for 2,3,4 years that no longer have capacity. I suspect it's because they have just been around longer, and we may be seeing the first casualties of such abuse. Hard to say with certainty. Some suspect the arrangement and nature of the cells that some parallel strings have lost connections due to vibrations. More people doing a teardown and postmortem would be required to be definitive

On these types of batteries with FCP that are in continuous use it will be imperative to have proper charge parameters set up from ALL charge sources. Inverter/charger, solar, alternator charging etc. In the case of the Epoch V2 the standard 14.2/13.5 is ideal and keeps the BMS clear of engaging the FCP. But the battery will ultimately protect itself in any case. The Victron Comms I believe also use the standard Victron protocol of 14.2/13.5 when run on the BMS-CAN. I have to verify that though. Going to the boat in a few to install these to monitor the details of how it works with the Cerbo in External Control.

Thanks. This type of battery behavior has been a big topic of conversation with the E-13 standard sub committee. The assertion is that these battery disconnects are blowing out alternators, and hence is behavior that is incompatible with an alternator power source. Several examples of dark ships in precarious situations were cited. I'd be interested in your thoughts on that since you are a boater, and presumably one with an alternator power source. I think everyone recognizes and accepts that it's an effective behavior in many applications, but there is a lot of concern over the exposure it creates for people dropping one of these batteries into a boat not knowing about this subtlety, and it's potentially significant impact on the boat.

 

[rslifkin]

Thanks. This type of battery behavior has been a big topic of conversation with the E-13 standard sub committee. The assertion is that these battery disconnects are blowing out alternators, and hence is behavior that is incompatible with an alternator power source. Several examples of dark ships in precarious situations were cited. I'd be interested in your thoughts on that since you are a boater, and presumably one with an alternator power source. I think everyone recognizes and accepts that it's an effective behavior in many applications, but there is a lot of concern over the exposure it creates for people dropping one of these batteries into a boat not knowing about this subtlety, and it's potentially significant impact on the boat.

I think that issue is what prompted Epoch to raise the voltage threshold for that feature on the V2 batteries. The V1 batteries enabled that feature at 14V IIRC, V2 is at 14.3. So if you never have a charge source feeding more than 14.2V, you should never trigger that feature.

 

[Barking Sands]

Thanks. This type of battery behavior has been a big topic of conversation with the E-13 standard sub committee. The assertion is that these battery disconnects are blowing out alternators, and hence is behavior that is incompatible with an alternator power source. Several examples of dark ships in precarious situations were cited. I'd be interested in your thoughts on that since you are a boater, and presumably one with an alternator power source. I think everyone recognizes and accepts that it's an effective behavior in many applications, but there is a lot of concern over the exposure it creates for people dropping one of these batteries into a boat not knowing about this subtlety, and it's potentially significant impact on the boat.

Please keep in mind I am not an expert and still learning every day.

A charge mosfet disconnect due to Full Charge Protection (FCP) is no different than a charge mosfet disconnect due to hitting the 14.6 pack overvolt or charge overcurrent. The method of the BMS exerting control (charge mosfet disconnect), result and potential damage are the same. The key is to know those parameters and set all charge sources accordingly and that the charge sources sending the voltage are well controlled. I have seen some older, not so great charge sources overshoot by a volt, or have some kind of temp compensation that can't be disabled etc. And in the lithium charging world tight control of voltage and the ability to set the required fields is paramount.

So for the older Epoch 460 V1 details are published to set absorption to 13.8 or 13.9 and then float at 13.5. Doing that steers clear of the FCP and there are no mosfet shutdowns. In the case of Litime, if you go to their facebook page this feature is a complete mystery. The activation criteria are not known (although it's very easy to figure out on your own). There is a constant stream of question regarding odd behavior as a result of this battery entering into FCP. As a result, all manner of solutions are stated.

Drop in battery manufacturers usually list some basic details regarding exceedances:
Cell overvolt
pack overvolt
discharge current limits
Short circuit current limit
Charge current limits
various temp limits etc etc.

Publishing whether or not a battery has FCP, and the criteria at which it engages should be basic information so equipment can be programmed appropriately.
To be fair, Epoch did not publish this in the beginning for the V1. It wasnt until it was clear to users that it was a thing did they make it known in the FAQ section. Ben Stein did a good job of showing the details on one of his videos on Panbo. I have also observed them in the BMS programming. 14 volts or more, amps falling below 3.6, those two parameters 10 seconds. The new V2 is the same but is enabled at 14.3.

Keep in mind though. There still should be no reason for a dark boat. A battery that hits FCP, or even pack overvolt of 14.6 still puts out power just fine. And it should have plenty of power to give because hitting FCP is only at the TOP of capacity ranges. Discharge mosfet is not affected. Also note that when FCP engages on the Epoch V1, charge amps have fallen to 3.5 amps or less, so I would assume the impact of a disconnect at such a low output would be less? Not sure about that since I've never tested vs voltage spike at full output. But as said its best just to avoid it and all other exceedance parameters via programming.

But, running an alternator to direct charge a battery that has FCP is a matter of having a programmable external regulator so you can control the absorption and float as to steer clear of FCP parameters, or any other parameters that might cut out the charge mosfet. Just like you would in order to not hit the 14.6 upper pack voltage that will also cause a charge mosfet disconnect. None of these batteries mentioned have CAN control that is compatible with Wakespeed or Zues that I am aware of. But having CAN control, while desirable, is not a prerequisite for an alternator to deliver a proper charge profile to a lifepo4 battery as long as you can set absorption and float reliably via quality equipment. 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. Wakespeed and Zues can do the same. Rod Collins seems to be fine using an old school MC618 with a safe charge profile set and then adding an alternator protection device. I feel that's fine as well although I use a 50amp Orion Dc2dc since my alternator is only 100 amps that's an easy combo.
Of course, FCP or pack overvolt limits are only one concern, charge current limits of the BMS and temp considerations can also cause a charge mosfet disconnect. All of these need to be considered in external regulator programming to ensure there is not a charge mosfet disconnect. And of course, DC to DC charging is another method to provide the battery with a controlled charge profile.

I dont see anything inherently dangerous with an FCP battery. The parameters just need to be known so you can consider them in programming any and all charge sources for a profile that's suitable,

 

[Barking Sands]

I think that issue is what prompted Epoch to raise the voltage threshold for that feature on the V2 batteries. The V1 batteries enabled that feature at 14V IIRC, V2 is at 14.3. So if you never have a charge source feeding more than 14.2V, you should never trigger that feature.

Epoch raised it mainly because many just didnt like being limited to 13.8 or 13.9 absorption. It does slow down charging as you approach absorption. You can reference Ben Stiens excellent testing on voltage vs time vs measured capacity to see exactly how much between 13.9 and 14.2.
I just got done the first day of testing the V2 in the boat. Its quite a battery and is very sophisticated. It appears it has several features that are SOC driven. The CAN control seems to work very well with Victron. Charge current limit is dynamic based on SOC it would appear. And it appears to have some kind of load sharing control between paired batteries. I'm still figuring things out though.

 

[MV Cricket]

Brand new to the forum!
I have had my two Epoch 460 amp V2 Elites for about a week and a half.
I see that Barking Sands has two of them connected and talking to his Victron setup.
I would LOVE to know how he did that. I cannot get mine to talk to the Ekranos. The "master" I can see but nothing else and hardly any info about the battery. Something is not right.
The DIP switches are set per the manual. The batteries are updated to V2.3 (this might be the problem as I heard from Brian on DYI Tito that the firmware should be V2.5. Anyone know the version of firmware is current?).
I am at a total loss as to what I am doing wrong.
I have the "master" battery wired with the blue comm port running to the Ekranos. That is VE.CAN and set to 500 bit LV. Then the CAN port on the "master" is plugged into the blue port on the "slave". I turn the batteries one and just see, with very limited info, one Epoch battery.
When I click on the Epoch tab, another screen opens but it only tells me the firmware version and some other info. Nothing about the cells.


These aren't very helpful pics but they are set to these settings.



Any help, like what DIP settings are being used, or anything would be great.
Still waiting on callbacks from Victron tech support and have multiple emails and Facebook things out there begging for info.
I wonder if the BMS is bad in my batteries. These just aren't that complicated to hook up. I am missing something easy OR I have a bad battery...
Thanks in advance for any help! Love the forum!

 

[Barking Sands]

Later tonight I'll have time to go over things in more detail.

 

[twistedtree]

I think that issue is what prompted Epoch to raise the voltage threshold for that feature on the V2 batteries. The V1 batteries enabled that feature at 14V IIRC, V2 is at 14.3. So if you never have a charge source feeding more than 14.2V, you should never trigger that feature.

If I'm following Barking Sands, even at 14.3V, once acceptance current has dropped below some threshold, it will still connect and disconnect?

 

[rslifkin]

If I'm following Barking Sands, even at 14.3V, once acceptance current has dropped below some threshold, it will still connect and disconnect?

Yes, but it's not a full disconnect, it just turns off the charge mosfet (discharge is still allowed). But if you never push it up to 14.3V when charging, you'll never run into that protection mode regardless of how low the charge current gets.

 

[MV Cricket]

Later tonight I'll have time to go over things in more detail.

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.

 

[twistedtree]

Please keep in mind I am not an expert and still learning every day.

A charge mosfet disconnect due to Full Charge Protection (FCP) is no different than a charge mosfet disconnect due to hitting the 14.6 pack overvolt or charge overcurrent. The method of the BMS exerting control (charge mosfet disconnect), result and potential damage are the same. The key is to know those parameters and set all charge sources accordingly and that the charge sources sending the voltage are well controlled. I have seen some older, not so great charge sources overshoot by a volt, or have some kind of temp compensation that can't be disabled etc. And in the lithium charging world tight control of voltage and the ability to set the required fields is paramount.

So for the older Epoch 460 V1 details are published to set absorption to 13.8 or 13.9 and then float at 13.5. Doing that steers clear of the FCP and there are no mosfet shutdowns. In the case of Litime, if you go to their facebook page this feature is a complete mystery. The activation criteria are not known (although it's very easy to figure out on your own). There is a constant stream of question regarding odd behavior as a result of this battery entering into FCP. As a result, all manner of solutions are stated.

Drop in battery manufacturers usually list some basic details regarding exceedances:
Cell overvolt
pack overvolt
discharge current limits
Short circuit current limit
Charge current limits
various temp limits etc etc.

Publishing whether or not a battery has FCP, and the criteria at which it engages should be basic information so equipment can be programmed appropriately.
To be fair, Epoch did not publish this in the beginning for the V1. It wasnt until it was clear to users that it was a thing did they make it known in the FAQ section. Ben Stein did a good job of showing the details on one of his videos on Panbo. I have also observed them in the BMS programming. 14 volts or more, amps falling below 3.6, those two parameters 10 seconds. The new V2 is the same but is enabled at 14.3.

Keep in mind though. There still should be no reason for a dark boat. A battery that hits FCP, or even pack overvolt of 14.6 still puts out power just fine. And it should have plenty of power to give because hitting FCP is only at the TOP of capacity ranges. Discharge mosfet is not affected. Also note that when FCP engages on the Epoch V1, charge amps have fallen to 3.5 amps or less, so I would assume the impact of a disconnect at such a low output would be less? Not sure about that since I've never tested vs voltage spike at full output. But as said its best just to avoid it and all other exceedance parameters via programming.

But, running an alternator to direct charge a battery that has FCP is a matter of having a programmable external regulator so you can control the absorption and float as to steer clear of FCP parameters, or any other parameters that might cut out the charge mosfet. Just like you would in order to not hit the 14.6 upper pack voltage that will also cause a charge mosfet disconnect. None of these batteries mentioned have CAN control that is compatible with Wakespeed or Zues that I am aware of. But having CAN control, while desirable, is not a prerequisite for an alternator to deliver a proper charge profile to a lifepo4 battery as long as you can set absorption and float reliably via quality equipment. 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. Wakespeed and Zues can do the same. Rod Collins seems to be fine using an old school MC618 with a safe charge profile set and then adding an alternator protection device. I feel that's fine as well although I use a 50amp Orion Dc2dc since my alternator is only 100 amps that's an easy combo.
Of course, FCP or pack overvolt limits are only one concern, charge current limits of the BMS and temp considerations can also cause a charge mosfet disconnect. All of these need to be considered in external regulator programming to ensure there is not a charge mosfet disconnect. And of course, DC to DC charging is another method to provide the battery with a controlled charge profile.

I dont see anything inherently dangerous with an FCP battery. The parameters just need to be known so you can consider them in programming any and all charge sources for a profile that's suitable,

Thanks, that's very helpful. I haven't experienced any of this myself, and am relaying concerns I have heard voiced. As for alternators, even though a battery acceptance current may be very low, an alternator can still be outputting high current powering DC loads. I think that's where there is still exposure.

E-13 has always had a requirement that a power system design take into account that a BMS can disconnect at any time, and a requirement that it not cause damage. 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 think a lot of the heartache is that many battery manufacturers don't document how their products work, and in this instance a number of people were caught off-guard by disconnects that they weren't expecting.

 

[rslifkin]

Thanks, that's very helpful. I haven't experienced any of this myself, and am relaying concerns I have heard voiced. As for alternators, even though a battery acceptance current may be very low, an alternator can still be outputting high current powering DC loads. I think that's where there is still exposure.

E-13 has always had a requirement that a power system design take into account that a BMS can disconnect at any time, and a requirement that it not cause damage. 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 think a lot of the heartache is that many battery manufacturers don't document how their products work, and in this instance a number of people were caught off-guard by disconnects that they weren't expecting.

In this kind of disconnect scenario the DC loads wouldn't drop because the loads don't disappear and the battery discharge MOSFET is still connected. I'm not sure how much DC load you'd need to absorb any spikes, etc. and prevent alternator damage though. The biggest risk would likely be if the partial disconnect happened with minimal load on the DC system.

Personally though, I'll likely end up doing DC-DC converters from the start batteries for LFP house charging. It's the simpler way to prioritize start battery charging over house in my application without getting into mounting a second alternator on each engine.

 

[twistedtree]

In this kind of disconnect scenario the DC loads wouldn't drop because the loads don't disappear and the battery discharge MOSFET is still connected. I'm not sure how much DC load you'd need to absorb any spikes, etc. and prevent alternator damage though. The biggest risk would likely be if the partial disconnect happened with minimal load on the DC system.

Personally though, I'll likely end up doing DC-DC converters from the start batteries for LFP house charging. It's the simpler way to prioritize start battery charging over house in my application without getting into mounting a second alternator on each engine.

That's a really good point. The answer with all of this fried-alternator-due-to-BMS-disconnect stuff is "it depends". It's very system specific, load specific, etc.

 

[Barking Sands]

That's a really good point. The answer with all of this fried-alternator-due-to-BMS-disconnect stuff is "it depends". It's very system specific, load specific, etc.

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.