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

[OceanSeaSpray]

Originally Posted by Maine Sail

This was simply an improperly installed and poorly engineered system.... The BMS should be able to take ANY and ALL charging sources off line and do it safely so damage does not occur to that equipment when doing so..
...
Sadly stories like this are what will get LFP a black eye... Not the fault of the LFP bank but rather the fault of the owner....

100% correct. Overvoltage protection from the alternator was not taken into account in this installation. Note that the blame went to the right place, but it is still another story of destroyed lithium batteries.

The only safe way of preventing this is interrupting the supply to the alternator field, i.e. wiring to the slip rings. Cutting the supply to the regulator is more uncertain, because some alternators self-excite after start-up and can carry on anyway and a destroyed regulator can easily energise the field in an uncontrolled way.

[goboatingnow]

Originally Posted by OceanSeaSpray

100% correct. Overvoltage protection from the alternator was not taken into account in this installation. Note that the blame went to the right place, but it is still another story of destroyed lithium batteries.

The only safe way of preventing this is interrupting the supply to the alternator field, i.e. wiring to the slip rings. Cutting the supply to the regulator is more uncertain, because some alternators self-excite after start-up and can carry on anyway and a destroyed regulator can easily energise the field in an uncontrolled way.

The simplest most effective way to implement HVC protection on an alternator is to switch in a alternative load and disconnect the battery. ( using a make before break changeover switch ) . A decent power resistor will do. This allows all the switching to be controlled in the battery compartment with no modification to the alternator.

Dave


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[hellosailor]

Suede, there's no "vanadium phosphate" to replace "lithium".

The URL you supplied makes it clear that company is using vanadium to replace the manganese or iron in a lithium battery, so this is still very much a "lithium" battery.

Two red flags that I see though. First, they quote a 2010 conference. OK, that's 3-1/2 years ago and still no product. Second, their home page has an INVESTORS tab on the top, and I've noticed in the last 10+ years that whenever a company is trolling for investors that way, the company is trolling for investors, not selling product. Seems like they invariably don't make it to market, either.

Sixfold capacity gain would be nice, but the battery business did run on dead ends for most of a hundred years before "lithium" was found, and 20? years later, lithium still is highly debated and lead hasn't gone away yet.

Besides, home thermonuclear piles are going to obsolete all batteries anyway. I know that because Reddy Kilowatt promised it to us in the early 60's, and a nuclear power industry mascot couldn't lie.

[goboatingnow]

Originally Posted by hellosailor

Reddy Kilowatt promised it to us in the early 60's, and a nuclear power industry mascot couldn't lie.

Thats not what Greedy Kilowatt said,

[NahanniV]

Originally Posted by goboatingnow

The simplest most effective way to implement HVC protection on an alternator is to switch in a alternative load and disconnect the battery. ( using a make before break changeover switch ) . A decent power resistor will do. This allows all the switching to be controlled in the battery compartment with no modification to the alternator.

Dave


Sent from my iPad using Tapatalk

I see a lot of manual switches with this functionality. Can you point me to an electrically operated one ?

Thanks,
JM.

[OceanSeaSpray]

Originally Posted by goboatingnow

The simplest most effective way to implement HVC protection on an alternator is to switch in a alternative load and disconnect the battery. ( using a make before break changeover switch ) . A decent power resistor will do. This allows all the switching to be controlled in the battery compartment with no modification to the alternator.

Dave

It is also one of the most stupid way of doing it without destroying anything - for a start - and it would take one massive resistor. If the system goes over-voltage and you dump the resulting excess power instead of addressing the root cause - something has gone very wrong - you open the road for much more damage including fire.
If the regulator fails shorted, alternator output becomes proportional to engine revs. Happy cooking.

Definitely NOT the way of addressing a regulation failure issue.

[OceanSeaSpray]

Originally Posted by Maine Sail

Remember your HVC is at 14.2V this means you really want all charging sources at 14.0V or less because the voltage resolutiuon is pretty inaccurate so -0.2V is a safe bet to stay out of HVC trips.

The HVC is a very short term cut and rebounds and re-energizes when voltage falls back to safe levels.. Dimitri has put a little more hysteresis in there but still not much.

For an alt you only need a small normally closed relay to break the regulator power / B+ lead. You NEVER, EVER open B+/OUTPUT of the alternator. To safely stop an alternator you open field or power to the regulator.

The HVC should be at a level where damage to the batteries is still prevented and the alarm at a level where voltage is abnormal for the system. This means that HVC could even be around 14.4V or so, and alarm would sound from say 14.2V with normal charging at 14.0V. It would not be a bad idea to trip if the alarm keeps going for too long either.

In my view, a HVC is the result of a system fault and it should not reset, and certainly not quickly, otherwise it becomes a regulation mechanism, not a protection system. A small time-delay on HVC is a better way of preventing nuisance trips due to short voltage spikes and response in regulation.
A LV trip could auto-reset once some decent charge has gone back in.

For an alternator, you should use a normally open relay to break the field circuit, otherwise the system is not fail-safe. If the BMS "disappears", you don't want to be charging blindly, so you want to energize the relay to charge.

[Jd1]

Originally Posted by Jd1

Has anyone used or heard anything about FBC Lithium cells ?

Lithium Prismatic EV Car Battery 200Ah, 3C, 3.2V, FBC Model: BP-HZPP-200 LiFePO4

These are priced pretty good but I am not clear if that is FOB the USA or China.

<bump> .... anyone ?

[Viking Sailor]

Here is an article on LiFePO4 batteries from the good folks at MIT.

Seeing how a lithium-ion battery works | MIT News Office

Enjoy,

Paul

[Hkalan]

Good Morning,

I believe most of us understand that LifePO4 is best to have a regulated 14v or 28v as a happy SOC. The BMS is "Protection" so it does not go over a max 28.8v (14.v) if your cells are 3.6v as a max... some cells are 3.8v, but the majority I see here are 3.6v max.

I have 8 cells, and have set the main SOC to be at 28v for the solar charger and alternator. 28v and no more... the BMS is my own "personal Jesus" to protect the cells. That means the BMS has a "warning alarm HVC trigger", and a "system max HVC trigger". Two different voltages and 2 different methods to cut all power to the cells...

Warning Level HVC = 28.4v
System Max HVC = 28.8v

These are the protection voltages of the BMS... this is NOT saying to continuously maintain your bank at these voltages. It is the protection voltages of the BMS that most of us are talking about. BMS cut off voltages.

I have relays on both the warning voltages, and should they fail, then the system MAX will trigger the relays and cut off any charge to isolate the bank completely.

On my House Power BMS, I have a Yellow strobe and siren alarm that also goes off at the warning voltage levels with the relays... so if the bank that is normally sitting happy at 28v, and it would for some crazy reason reach 28.4v, I have lights, sirens, and relays cutting off charge, and I go see why it is not at 28v.

I have a battery isolator off my port engine 24v alternator, and one output goes to a voltage regulator just for the LifePO4 bank, and the other out goes to the emergency back up house bank... and should the HVC relays cut any charge (disconnecting the load) if something is amiss, the alternator is still under load with the emergency Lead Acid bank, all managed by the alternator voltage regulator for a Lead Acid bank. I still have the siren and lights grabbing my attention from the LFP bank, and then even the Lead Acid is safe.

I know some of my replies have been a bit lacking in the full details, but I hope the drawing of my BMS fills in some blanks where I have missed.

One thing that is not in the drawing, is the Cell-Log-8. I have the LVC alarm of that wired into the inverter, so if the LVC relay of the House Power BMS does not function, then the Cell-Log-8 is the back up. Note: The Cell-Log-8 is powered on the USB input.

As I have 12v on the Genset start and for all NAV gear, 32v on each Detroit Diesel (I know I should change over to 24v), and the 24v house banks. I monitor all of them with the Victron Blue Power Panel, with a VE.Net Battery controller at each bank to monitor all banks from one location at my main breaker panel. I also have alarms from that....

I live on my vessel, so I am truly a man of redundancy !

Thanks,

Alan

[OceanSeaSpray]

Alan,

Thanks for taking the time to document this. Your diagram should give food for thoughts to a few of your earlier commentators.

You are ok because of the presence of the lead-acid bank acting as a base load for your 70A alternator through the blocking diodes and with all the alarms going off you would normally do something before those get damaged.
You would still be better off interrupting the circuit at the slip rings of your alternator and leaving its output connected, this way you protect the entire installation from an alternator fault and it saves one of those large contactors.
Same principle with the charger, I would cut its AC mains supply rather than the heavy current coming out of it.

You seem to drop the load on a HV condition as well as LV, but this can be a design choice.

Regards,

Eric

[Hkalan]

Hi Eric,

I did have the relay on the AC side, I recently put it the dual coil on the DC side because I ordered several more single and double pole relays to stow, and will have the AC side relay back in by the end of next week. All relays will match and from the same factory. (the ac side relay was a local purchase and was not confident in it).

I was reading on another forum how an El-Cheapo-Charger short circuit, and even when the AC side was cut, the DC was back feeding into the charger that started a minor fire (don't understand how)... so for all safety sake I will cut both AC and DC sides. Cant hurt !

Alan

[goboatingnow]

Originally Posted by NahanniV

I see a lot of manual switches with this functionality. Can you point me to an electrically operated one ?



Thanks,

JM.

Omron do one , Shrak , TE. Mostly special order

Also easy enough to rig up two simple NO NC dP relays with a small time delay between then to ensure MBB action

Dave

[KASHMIR]

I am after some information on the settings that would suit LiFePO4 cells being charged by a Balmar MC614. I would assume that setting the battery type to AGM will give suitable voltages, but should I also adjust the Bulk/absorption/float times and or voltage as well? If so what would the experts recommend?

[T1 Terry]

Originally Posted by KASHMIR

I am after some information on the settings that would suit LiFePO4 cells being charged by a Balmar MC614. I would assume that setting the battery type to AGM will give suitable voltages, but should I also adjust the Bulk/absorption/float times and or voltage as well? If so what would the experts recommend?

Are you serious? As a commercial member who is fitting up lithium batteries you should have the R&D behind you to know this information, if you don't, you shouldn't be fitting up lithium batteries as a commercial venture. Are you really going to put it all on the line using information you gained from a forum???? If I gave you a set of figures what makes you think I'm not setting you up for a major fall?

T1 Terry