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

[CharlieJ]

#7666

Quote:
Question: How important is it to have this level of protection (advance shutdown communication between the LFP BMS and the Regulator) 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?
Answer: Not very important. Yes you can use closed LFP BMS batteries reliably.

"Closed LFP batteries", aka drop in batteries such as Battle Born, do not communicate outside of the battery case and therefore will not be in compliance with ABYC E-13 Lithium Batteries when it is published July, 2022.

[goboatingnow]

Originally Posted by mitiempo

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

Yes but this then leaves the more powerful alternator charging a battery that doesn’t need it or an expensive powerful dc dc battery charger

[mitiempo]

Originally Posted by goboatingnow

Yes but this then leaves the more powerful alternator charging a battery that doesn’t need it or an expensive powerful dc dc battery charger

It is one or the other.

High output alt, Wakespeed or Balmar reg and DC to DC to charge the start battery - but expensive.

or

Stock alt to start battery and DC to DC charger for Lfp bank. Much less expensive and if you have relatively small loads as I do a good solution.

[rslifkin]

Originally Posted by mitiempo

It is one or the other.

High output alt, Wakespeed or Balmar reg and DC to DC to charge the start battery - but expensive.

or

Stock alt to start battery and DC to DC charger for Lfp bank. Much less expensive and if you have relatively small loads as I do a good solution.

Or the third option: 2 alternators. 1 externally regulated to charge the LiFePO4 bank and 1 (whatever regulation you want) to charge the start battery.

[mitiempo]

Originally Posted by newhaul

But it is a charger insofar as it converts the 24v output to what ever voltage you program to allow 70 amps charging .read the specs. Settable from 10 to 15 volts so set at 14.2 it will do its job as a cc/cv charger.

It is a single voltage setting converter. Without a charging profile, much less an adjustable one, it is not a charger. Victron agrees.

[mitiempo]

Originally Posted by rslifkin

Or the third option: 2 alternators. 1 externally regulated to charge the LiFePO4 bank and 1 (whatever regulation you want) to charge the start battery.

Yes that is yet another option, also expensive.

If you have heavy loads and wish (need?) to run the engine often just for charging these solutions can make sense.

[rgleason]

Questions rephrased:

How important is it to have BMS advance shutdown signal to the regulator, if the FLA battery is charged by a 30 amp DC-DC Charger and the regulator has a Balmar APM installed?

Answer: Not important, the Alternator and electronics will be protected.

Can I reliably use sealed drop in LFP/BMS Batteries with no external BMS signal for shutting down the alternator?

Answer: Yes. You can use sealed LFP BMS batteries reliably with:

• External regulator programmed for LFP, with belt manager, alt & bat temp sensors.
• 30a DC-DC charger from LFP to FLA
• Balmar APM installed

Are the answers given above, correct?

If the system works, why is ABYC compliance necessary?

When will sealed drop in LFP batteries with Canbus external communication become available?
These battery manufacturers are ridiculously slow.

[newhaul]

Originally Posted by rgleason

Questions rephrased:

How important is it to have BMS advance shutdown signal to the regulator, if the FLA battery is charged by a 30 amp DC-DC Charger and the regulator has a Balmar APM installed?

Answer: Not important, the Alternator and electronics will be protected.

Can I reliably use sealed LFP Batteries with no external BMS signal for shutting down the alternator?

Answer: Yes. You can use sealed LFP BMS batteries reliably with:

• External regulator programmed for LFP, with belt manager, alt & bat temp sensors.
• 30a DC-DC charger from LFP to FLA
• Balmar APM installed

Are the answers given above, correct?

If the system works, why is ABYC compliance necessary?

ABYC compliance is never required. The ABYC is not a regulatory agency.

[goboatingnow]

Originally Posted by mitiempo

It is one or the other.



High output alt, Wakespeed or Balmar reg and DC to DC to charge the start battery - but expensive.



or



Stock alt to start battery and DC to DC charger for Lfp bank. Much less expensive and if you have relatively small loads as I do a good solution.

If you have small loads why have Li at all.

Powerful dc dc with Li charge profiles are expensive.

External alternator regulators are quite cheap.

Fit a balmar alternator protector for HVC protection.

Anyway HVC should never happen in a properly set up Li system

[newhaul]

Originally Posted by goboatingnow

If you have small loads why have Li at all.

Powerful dc dc with Li charge profiles are expensive.

External alternator regulators are quite cheap.

Fit a balmar alternator protector for HVC protection.

Anyway HVC should never happen in a properly set up Li system

Why have lfp with my relatively low loads?
Charge profile, consistent voltage curve ( no voltage sag when I run my rice cooker)
The biggie is 250ah bank for $600 all in and an expected cycle life of 6,000 to 8,000 cycles.

A full cycle on my boat would take 3 or 4 days . Let's say 3 days . That's 12,000 to 16,000 days or a minimum of 95 years . Even at 2 days it's still way above 60 years . Even a daily cycle is over 30 years.

With a daily cycle it comes out to be 20 bucks a year.
Daily full charge with 200 watts solar.

Show me any lead based that can meet all or even any of the above.

Last but not least . I wanted it so I got it.

[PaulCrawhorn]

Originally Posted by mitiempo

It is a single voltage setting converter. Without a charging profile, much less an adjustable one, it is not a charger. Victron agrees.

All that is needed is a reliable HVC

[donradcliffe]

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.

Been too busy to delve further into your equipment until now.

The latching relays did address one of my concerns. They seem to be compatible with the TAO BMS.

The TAO BMS doesn't seem to have a high current alarm or disconnect. Probably because it doesn't have Mosfets to protect, but I liked that feature in the standard BMS.


The Duocharge seems to have a parasitic draw of 500 milliamps. You will need to cut it off completely if you store the boat without charging.

I hope you will carry a spare BMS. It seems to me a couple of spare battery cells would also add a lot add to system reliability.

I would not be confident of the passive alternator protection system unless I tested it a few times at max alternator current, which in your case might be over 200 amps. Of course those might be expensive tests. I assume you will hook the alternator regulators to one of the many output controls of the TAO and terminate charging well before a disconnect.

I'm starting to get the feeling that people are overthinking maximum battery life. If you get 10 years out of your pack, there will be better and cheaper replacements. Heat and cold seem to be the biggest enemies of battery life. Keep the batteries out of the engine compartment and prevent charging when under 32 degrees F.

Enjoy your system.

[rgleason]

I found this very interesting. The problem is not as simple as I thought.

“lithium” versions of the Genasun GV-5 / GV-10 solar MPPT controllers: these little marvels of engineering and efficiency respectively deliver up to 5A and 10A at a steady 14.2V output… forever! There is no way to adjust anything and no way to turn them off without seriously hacking the circuit boards. These are the best lithium plating controllers on the market.

Fortunately my Genasun fried after 6 years due to a bad panel short circuit.

According to Nordkyn (read down to "Approximating the Solution" and the comments at the end) we need to prevent unnecessary cycling, and any BMS should keep track of LFP state of charge due to all the charge sources, and all charging devices should be properly controlled with current and voltage sensing.

https://nordkyndesign.com/charging-m...battery-banks/

Since we do not use shore power generally, there are only two charge sources: Solar and Alternator. These two charge sources may overcharge the LFP if not properly controlled and accounted for (columb counting?). LFP is very sensitive to overcharging, so the solar controller and alternator regulator have to be precise. In our case, the solar regulator should be completely adjustable to allow disabling absorption and float, and the alternator regulator should use a current and voltage sensing pair to determine when to stop charging completely. He advises there should be a load on the system so the LFP starts to discharge to establish the cycle and protect the LFP.


Can the Victron SmartSolar MPPT 75/15 be adjusted to shutdown the absorption and float stages so there is no charge? https://www.victronenergy.com/upload...WM-or-MPPT.pdf I find this information:

Programmable battery charge algorithm See the software section on our website for detail

The Software is https://www.victronenergy.com/solar-...00-20#software but I can't find the charging information.

[rgleason]

SmartSolar MPPT 75/15

https://www.victronenergy.com/upload...-20_48V-EN.pdf

Self-consumption – load on 12V: 19 mA 24V
Self-consumption – load off 12V: 10 mA 24V: 8 mA
Charge voltage 'absorption' 14,4V / 28,8V (adjustable
Charge voltage 'float' 13,8V / 27,6V (adjustable)
Charge algorithm multi-stage adaptive
Temp. compensation -16 mV / °C resp. -32 mV / °C
Max. continuous load current 15A
Low voltage load disconnect 11,1V / 22,2V / 44,4V or 11,8V / 23,6V / 47,2V or Battery Life algorithm
Low voltage load reconnect 13,1V / 26,2V / 52,4V or 14V / 28V / 56V or Battery Life algorithm
Protection Output short circuit / Over temperature Temperature compensation -16 mV /°C

Still unclear if absorption and float can be "turned off".
I believe I would need that to avoid overcharging the LFP.

[jordanbigel]

Originally Posted by rgleason

When will sealed drop in LFP batteries with Canbus external communication become available?
These battery manufacturers are ridiculously slow.

They already exist - look at "Lithionics".

I did not buy these due to the high cost, but they have CANBUS and work with the Wakespeed, etc., etc. They also have a Bluetooth enable mobile app allowing visibility to the BMS data. Crazy $$$.

I bought BestGo (Elec Car Parts Company) which do not have CANBUS but do have signal relay warnings which indicate low/high voltage, low/high current and low/high temp which I've wired to a relay connected to my Balmar regulator's ignition wire to shut down alternator when batteries raise a warning condition (which happens before the BMS actually shuts down), and also to my Victron MP2 and to a relay which cuts off solar panels as well.