LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[fxykty]

Originally Posted by blondjohn

Hi Don,

Thanks for your questions and comments. The TAO BMS will be mounted next to the batteries. Each group of "4P" will be treated as a single cell by the centralized BMS. The solenoids are "Blue Sea ML-RBS 7713 Remote Battery Switch with Manual Control Auto-Release" and draw 13mA when on. I intend to have 3 in the system for 39mA parasitic draw. That is less than one amp per day. The Balmar Duocharge is keeping the engine bank full by trickle charging from the house bank while preventing the engine bank 2 from being drawn down by house loads. I already own the Duocharge so I decided to see how it performs in the new system before I consider replacing it with a larger and more sophisticated DC to DC converter. The BMS is centralized and does not carry any house load current. We typically use about 300 A per 24 hrs at anchor. More at sea. We have been spending years at a time in places where it is very difficult if not impossible to get batteries shipped in. The house bank is sized to allow individual cell failure and still have adequate capacity. It is also sized to continue providing adequate power for an extended period as the batteries approach end of life and begin to lose capacity. And finally, in what should really should be a separate discussion, there is a lot of data showing that LFP battery life is extended by limiting charge level and depth of discharge. I'm still studying, but it looks like cycling between 80% and 40% SOC could provide significantly longer service life than running between 100% and 20% SOC. Remember I'm trying to optimize for extended service life, not weight or cost per total amps provided during the service life of the batteries.



Thanks again for your time to question my system design.

We have two Balmar DuoChargers that provide charge current to our two AGM start batteries, set so that they only do so when LFP battery voltage is >13.40V. Work as expected with no issues.

Regarding LFP longevity, if you’re willing to charge up to 80% SOC regularly then there is no issue discharging down to 20% SOC. Other factors affecting long term capacity are current limits (stay well below 1C) and battery temperature (try to keep it below 30*C and even better below 25*C).

There’s lots of theories about frequent cycling when on shore power and whether that’s bad or indifferent, and whether setting the shore power charging voltage to something equivalent to 50% SOC is best (so around 13.2V). https://nordkyndesign.com/charging-m...battery-banks/ provides some thoughts on this issue.

Thankfully you have a TAO BMS - that simplifies your life as you can use its charge profile feature to start/stop charging at particular SOCs (with voltage-based triggers as a backup). If you also have the TAO Monitor then you can define multiple charge profiles, as well as to use CANBUS to control Victron equipment via a Cerbo. Do post your installation on the TAO forum https://www.taoperf.com/forum/ - Philippe is very responsive and helpful.

[newhaul]

Originally Posted by blondjohn

Hi Don,
Thanks for your questions and comments. The TAO BMS will be mounted next to the batteries. Each group of "4P" will be treated as a single cell by the centralized BMS. The solenoids are "Blue Sea ML-RBS 7713 Remote Battery Switch with Manual Control Auto-Release" and draw 13mA when on. I intend to have 3 in the system for 39mA parasitic draw. That is less than one amp per day. The Balmar Duocharge is keeping the engine bank full by trickle charging from the house bank while preventing the engine bank 2 from being drawn down by house loads. I already own the Duocharge so I decided to see how it performs in the new system before I consider replacing it with a larger and more sophisticated DC to DC converter. The BMS is centralized and does not carry any house load current. We typically use about 300 A per 24 hrs at anchor. More at sea. We have been spending years at a time in places where it is very difficult if not impossible to get batteries shipped in. The house bank is sized to allow individual cell failure and still have adequate capacity. It is also sized to continue providing adequate power for an extended period as the batteries approach end of life and begin to lose capacity. And finally, in what should really should be a separate discussion, there is a lot of data showing that LFP battery life is extended by limiting charge level and depth of discharge. I'm still studying, but it looks like cycling between 80% and 40% SOC could provide significantly longer service life than running between 100% and 20% SOC. Remember I'm trying to optimize for extended service life, not weight or cost per total amps provided during the service life of the batteries.

Thanks again for your time to question my system design.

What we have figured out is low rates of charge and discharge are better for long life try to keep the majority of charging between .2C and .5C.
The slower the charge the less heat and longer the life . same for discharging . there was actually a very long running discussion on the subject.

[blondjohn]

Originally Posted by fxykty

We have two Balmar DuoChargers that provide charge current to our two AGM start batteries, set so that they only do so when LFP battery voltage is >13.40V. Work as expected with no issues.

Regarding LFP longevity, if you’re willing to charge up to 80% SOC regularly then there is no issue discharging down to 20% SOC. Other factors affecting long term capacity are current limits (stay well below 1C) and battery temperature (try to keep it below 30*C and even better below 25*C).

There’s lots of theories about frequent cycling when on shore power and whether that’s bad or indifferent, and whether setting the shore power charging voltage to something equivalent to 50% SOC is best (so around 13.2V). https://nordkyndesign.com/charging-m...battery-banks/ provides some thoughts on this issue.

Thankfully you have a TAO BMS - that simplifies your life as you can use its charge profile feature to start/stop charging at particular SOCs (with voltage-based triggers as a backup). If you also have the TAO Monitor then you can define multiple charge profiles, as well as to use CANBUS to control Victron equipment via a Cerbo. Do post your installation on the TAO forum https://www.taoperf.com/forum/ - Philippe is very responsive and helpful.

Hi Foxy Kitty,

Thanks for sharing your thoughts. Happy to hear about your good experience with the Balmar Duocharge.

I have seen data that strongly support your position to operate LFP between 20% to 80% SOC to achieve excellent longevity. I also recall seeing data that suggested even longer life with a higher SOC discharge limit. Sorry I don't have a reference at hand to support that. I need to build a better library.

I've seen multiple data sets on high temperature degradation of LFP capacity and cycle life and I intend to install a fan in the battery compartment and run it constantly in the tropics.

Nordkyndesign.com is an excellent resource. I don't doubt that with careful control LFP can be safely used with float charging on shore power, but I like the idea of isolating and storing the LFP and not even thinking about it when we are in the boatyard on shore power.

Philippe, creator of the TAO BMS, has been extremely generous with his time helping me along the learning curve. I did buy the full TAO kit with the monitor. Phil has unfortunately had to temporarily suspend sales due to supply chain problems and lack of components, But he should be back up and selling product in a few months. I would highly recommend anyone looking for a new BMS look at the TAO Performance BMS.

[goboatingnow]

Originally Posted by Simi 60

Not just LFP
I killed off two large frame continuously rated alts hooked up to our old AGM bank
Didn't even bother with alt charge on the new LFP bank

Sorry this is nonsense. Alternators can be regulated like any charge source do it right and there is no issue charging Li batteries from them. Sure connect up the crappy car regulator in the stock alternator and watch it fry . Li is a complete system rework.

Why people treat alternators as if they are untouchable is beyond me

[Q Xopa]

Originally Posted by Simi 60

Not just LFP
I killed off two large frame continuously rated alts hooked up to our old AGM bank
Didn't even bother with alt charge on the new LFP bank

I have Temp Regulation on my Alternators and I dont have problems.

[Simi 60]

Originally Posted by goboatingnow

Sorry this is nonsense. Alternators can be regulated like any charge source do it right and there is no issue charging Li batteries from them.

Yeah, if I spend another $1000 to make it work
(24v system)

Sure connect up the crappy car regulator in the stock alternator and watch it fry

Did you not read the bit where I said it was AGM - NOT lifepo4
You quoted it.

And it was a large frame continuously rated truck alt, , about 10kg heavier and not exactly stock
I mentioned that to, and you quoted it.

. Li is a complete system rework

Not always
All our wiring, charger, inverter, mppt stayed the same
Just had to reprogramme the charge settings

Why people treat alternators as if they are untouchable is beyond me

Well for us it was a large frame continuously rated truck alt on a 14 litre Cummins engine.
And it was using the same wiring and VSR setup that the previous owner had installed.
Only difference now was we had 8 vs 6 220ah AGM

[goboatingnow]

Originally Posted by Simi 60

Yeah, if I spend another $1000 to make it work
(24v system)

Did you not read the bit where I said it was AGM - NOT lifepo4
You quoted it.

And it was a large frame continuously rated truck alt, , about 10kg heavier and not exactly stock
I mentioned that to, and you quoted it.

Not always
All our wiring, charger, inverter, mppt stayed the same
Just had to reprogramme the charge settings



Well for us it was a large frame continuously rated truck alt on a 14 litre Cummins engine.
And it was using the same wiring and VSR setup that the previous owner had installed.
Only difference now was we had 8 vs 6 220ah AGM

It doesn’t matter if it’s AGMs you still need a better regulator as the charge acceptance for AGMs is high and this stresses the stock alternator.


My point is people are spending $$$ on Li systems often with all new surrounding wiring charge systems etc. yet there’s seems to be an reluctance to properly deal with the alternator. With a proper regulator and temp control charging Li direct is straightforward and this typically provides the remote disconnect which the Li BMS can use. Even without that appropriate surge suppressors can eliminate the disconnect issue anyway.

The workaround of leaving a small LA battery in circuit promotes inefficiency and results in incorrect charge profiles being supplied to one bank or the other

[mitiempo]

Originally Posted by goboatingnow

The workaround of leaving a small LA battery in circuit.....and results in incorrect charge profiles being supplied to one bank or the other

Not with a proper DC to DC charger set to the correct voltages for lithium.

[rgleason]

Originally Posted by goboatingnow

The workaround of leaving a small LA battery in circuit.....and results in incorrect charge profiles being supplied to one bank or the other

Originally Posted by mitiempo

Not with a proper DC to DC charger set to the correct voltages for lithium.

I very nice simple solution, but wouldn't that remove the simple alternator spike protection of having a small FLA battery in the LFE House Bank - Alternator circuit? Maybe this battery should just be considered a throwaway battery, a cheap starter battery just big enough to mitigate and protect those infrequent occasions when the BMS disconnects the LFP.



Of course having that FLA in the circuit also means there are other points of failure and maintenance, like checking for fluids and making sure there are no shorts. It is just acting like one side of a big capacitor that is getting charged up. Would this really provide good protection to the Alternator Diodes and Electronics?

[newhaul]

Originally Posted by rgleason

Originally Posted by goboatingnow

The workaround of leaving a small LA battery in circuit.....and results in incorrect charge profiles being supplied to one bank or the other

I very nice simple solution, but wouldn't that remove the simple alternator spike protection of having a small FLA battery in the LFE House Bank - Alternator circuit? Maybe this battery should just be considered a throwaway battery, a cheap starter battery just big enough to mitigate and protect those infrequent occasions when the BMS disconnects the LFP.



Of course having that FLA in the circuit also means there are other points of failure and maintenance, like checking for fluids and making sure there are no shorts. It is just acting like one side of a big capacitor that is getting charged up. Would this really provide good protection to the Alternator Diodes and Electronics?

No not at all an issue that is my setup I have a grp 24 start fla battery and a 60 amp b2b to charge my lfp bank .

[rgleason]

I re-edited the post below past time allowed: Sorry

Originally Posted by goboatingnow

The workaround of leaving a small LA battery in circuit.....and results in incorrect charge profiles being supplied to one bank or the other

Originally Posted by mitiempo

Not with a proper DC to DC charger set to the correct voltages for lithium.

It is a very nice simple solution, but wouldn't that remove the simple alternator spike protection of having a small FLA battery in the LFE House Bank and Alternator circuit? Maybe this battery should just be considered a throwaway battery, a cheap starter battery just big enough to mitigate and protect those infrequent occasions when the BMS disconnects the LFP, and maybe just big enough to start the engines once or twice. (I've gotten into the habit of starting with my house battery bank.)

Of course having that FLA in the circuit also means there are other points of failure and maintenance, like checking for fluids and making sure there are no shorts which will quickly draw down the LFP and cause a disconnect. Wouldn't this provide good protection to the Alternator Diodes and Electronics? As a backup the Balmar APM Alternator Protection Module could be used, (because it indicates failed condition with a red led and a beep unlike diodes)

I am thinking of a system that has a very simple Battery BMS with no advance disconnect communication
The next level of protection would be BMS with advance communication to disconnect the Alternator blue wire (field)

The alternator would, of course, in any case, have an external regulator programmed for LFP, with battery and alternator temperature sensing and belt manager.

The above configuration would just be relying on the FLA and Balmar APM for alternator and nav equipment protection. For more definitive protection it would probably be better to have the BMS shut down the alternator in advance, thus requiring communication with the regulator.

This is the advantage of the Wakespeed WS500 Regulator or the earlier VSR Smart Alternator Regulator. It will have current sensing and canbus communication with opportunity for the a BMS with canbus communication to interrupt the blue wire (field current) to shut down the alternator in advance of BMS disconnect. However the BMS used has to be able to communicate with these regulators.

Question: How important is it to have this level of protection if you have the FLA battery and Balmar APM? This actually then turns into the question, Can I reliably use Closed LFP BMS Batteries with no external signal for the alternator?

I believe there is another BMS configuration possible, using some of the Victron BMS mosfet isolators in a simple configuration, which will work with non Victorn LFP Batteries but, their BMS with ve.bus requires Victron LFP batteries.
If someone could clarify that situation it would be helpful.

[mitiempo]

Originally Posted by rgleason

I re-edited the post below past time allowed: Sorry

Originally Posted by goboatingnow

The workaround of leaving a small LA battery in circuit.....and results in incorrect charge profiles being supplied to one bank or the other

It is a very nice simple solution, but wouldn't that remove the simple alternator spike protection of having a small FLA battery in the LFE House Bank and Alternator circuit? Maybe this battery should just be considered a throwaway battery, a cheap starter battery just big enough to mitigate and protect those infrequent occasions when the BMS disconnects the LFP, and maybe just big enough to start the engines once or twice. (I've gotten into the habit of starting with my house battery bank.)

Of course having that FLA in the circuit also means there are other points of failure and maintenance, like checking for fluids and making sure there are no shorts which will quickly draw down the LFP and cause a disconnect. Wouldn't this provide good protection to the Alternator Diodes and Electronics? As a backup the Balmar APM Alternator Protection Module could be used, (because it indicates failed condition with a red led and a beep unlike diodes)

I am thinking of a system that has a very simple Battery BMS with no advance disconnect communication or even a BMS with advance communication to disconnect the Alternator blue wire (field)

The alternator would, of course, in any case, have an external regulator programmed for LFP, with battery and alternator temperature sensing and belt manager.

The above configuration would just be relying on the FLA and Balmar APM for alternator and nav equipment protection. For more definitive protection it would probably be better to have the BMS shut down the alternator in advance, thus requiring communication with the regulator.

This is the advantage of the Wakespeed WS500 Regulator or the earlier VSR Smart Alternator Regulator. It will have current sensing and canbus communication with opportunity for the a BMS with canbus communication to interrupt the blue wire (field current) to shut down the alternator in advance of BMS disconnect. However the BMS used has to be able to communicate with these regulators. Question: How important is it to have this level of protection if you have the FLA battery and Balmar APM? This actually then turns into the question, Can I reliably use Closed LFP BMS Batteries with no external signal for the alternator.

I believe there is another BMS configuration possible, using some of the Victron BMS mosfet isolators in a simple configuration, which will work with non Victorn LFP Batteries but, their BMS with ve.bus requires Victron LFP batteries.
If someone could clarify that situation it would be helpful.

If one wants to spend the money for a Wakespeed reg and a Balmar or similar alt that works.

But remember that we a re talking about sailboats. Do you really want to run the engine just to charge the battery bank?

The inexpensive solution is a Fla start battery - group 24 and either sealed or Agm. A DC to DC charger - Victron the best choice - between the start battery and the LiFePo4 bank properly programmed. Simple, not expensive, and whichever alt you have it will not suffer.

Main charging solar.

[newhaul]

Originally Posted by mitiempo

If one wants to spend the money for a Wakespeed reg and a Balmar or similar alt that works.

But remember that we a re talking about sailboats. Do you really want to run the engine just to charge the battery bank?

The inexpensive solution is a Fla start battery - group 24 and either sealed or Agm. A DC to DC charger - Victron the best choice - between the start battery and the LiFePo4 bank properly programmed. Simple, not expensive, and whichever alt you have it will not suffer.

Main charging solar.

Actually the cheap option is a 100 dollar. 1000 watt generator and a 75 amp battery charger .

[mitiempo]

Originally Posted by newhaul

Actually the cheap option is a 100 dollar. 1000 watt generator and a 75 amp battery charger .

Actually, whatever the price of the generator ($100?), a 75 amp quality charger that can be set properly would be more expensive than the Victron Orion DC to DC charger.

[rgleason]

Do you really want to run the engine just to charge the battery bank?

Yes, I do because:
Cruising: We enter and leave harbors about .5 - 1 hour per day.
Solar: now (2) 50w on dodger, future (2) 100w on stern with (2) Victron 75/15 controllers.
Alternator: Faster charging with modified Delco Remy 12vdc 28SI 160amps belt managed down to 80-100 amps. (almost finished modification).
Regulator: ARS-5 has alt & batt temp sensors, belt manager LFP advance programming. Early WS500 VSR Alt Regulator available.
Want faster charging for at sea. DC-DC requires two or three 30amp. and very little room for that that I have found so far.
Absolutely no room for any generator and I don't want that complication.
Where do you put it when running? On deck? That's insane while at sea.


I had some questions below.