Drop in lithium batteries

[a64pilot]

IF a drop in had separate posts, it could disconnect either charge and or load independently.

Only reason I could see that a disconnect would happen at high charge levels is overtemp, and that is exceedingly rare, and can be of course an emergency, in that event, you want it to disconnect even if it harms a charger, cause it disconnects to prevent a thermal run away.

How do the current home made systems work? Do they communicate with charge sources and shut down the chargers?

[Maine Sail]

Originally Posted by a64pilot

IF a drop in had separate posts, it could disconnect either charge and or load independently.

If it had a communication port to communicate with the charge devices to shut them down properly this is now a much better design. Course now it is no longer a "drop-in" it becomes a system integrated LFP battery similar to a Lithionics OPE-Li3, Mastervolt or Victron. All similar well engineered systems for cruising boats. The current crop of drop-in LFP's (two terminals only Batt + & Batt -) don't have this ability.

I suspect before long, or when the ABYC standards get nearer, some drop in manufacturers will begin to offer external communication as at least an option. Some manufacturers are already beginning to revisit the ridiculously low BMS mosfet switch current ratings and improving them. An external comm port that can be used to disable charging or discharging, more safely, is simply good sound design for an off shore cruising boat.. Of course many of these drop-ins were never designed for our type use to begin with. For a bass boat trolling motor, who cares if the battery open circuits on low or high voltage without warning.

Originally Posted by a64pilot

Only reason I could see that a disconnect would happen at high charge levels is overtemp, and that is exceedingly rare, and can be of course an emergency, in that event, you want it to disconnect even if it harms a charger, cause it disconnects to prevent a thermal run away.

Sure, pretty rare with 4 well matched cells & a BMS that does not allow for voltages up to 15.6V to 16V before the protection kicks in, but when you have a bank with a hundred or more cells, of unknown origin, with no documentation on initial cell matching, capable of getting to 15.6V to 16V probably not as rare as one might think.

Originally Posted by a64pilot

How do the current home made systems work? Do they communicate with charge sources and shut down the chargers?

Any well engineered one does...

[SV THIRD DAY]

Originally Posted by Maine Sail

I suspect before long, or when the ABYC standards get nearer....

Ding...ding....
The dirty little truth is that I've seen several insurance companies DENY coverage to vessels with LiFePO4 battery banks. Now is that crazy stupid in my opinion yes but then again we are talking about Insurance Companies here folks. So before you get too far down the road on your LiFePO4 dream, you might want to make sure your insurance company will continue to insure you....if that matters to you anyway.

[arsenelupiga]

Originally Posted by SV THIRD DAY

Ding...ding....
The dirty little truth is that I've seen several insurance companies DENY coverage to vessels with LiFePO4 battery banks. Now is that crazy stupid in my opinion yes but then again we are talking about Insurance Companies here folks. So before you get too far down the road on your LiFePO4 dream, you might want to make sure your insurance company will continue to insure you....if that matters to you anyway.

dirty truth no 2 - insurance firms do not pay, ever, unless is somehow advertising them as good guys. If you not connected or youtube star, save money and insure third party only.

They have something like 'tiny print' and they can disqualify your claim any day. You have prrof - bills - all electric work ever on your boat has been done with approved electrician , etc, etc

[Maine Sail]

Originally Posted by SV THIRD DAY

Ding...ding....
The dirty little truth is that I've seen several insurance companies DENY coverage to vessels with LiFePO4 battery banks.

I have had numerous readers of my site tell me the same. Funny thing is one of them who was denied had the same underwriter as another customer but different isuing groups. One did not allow LFP yet the other did but both policies were underwritten by the same backing insurer.

[a64pilot]

So what chargers are there that can be controlled by a BMS?

On edit, cause I suspect few do, and to be well engineered means buying all new charge sources for most people?

[newhaul]

Originally Posted by SV THIRD DAY

Ding...ding....
The dirty little truth is that I've seen several insurance companies DENY coverage to vessels with LiFePO4 battery banks. Now is that crazy stupid in my opinion yes but then again we are talking about Insurance Companies here folks. So before you get too far down the road on your LiFePO4 dream, you might want to make sure your insurance company will continue to insure you....if that matters to you anyway.

mine didn't even ask about batteries
Full coverage agreed value .
Not even a haulout.

[a64pilot]

Originally Posted by newhaul

mine didn't even ask about batteries

Full coverage agreed value .

Not even a haulout.

They probably didn’t ask about a dozen other things that they could deny paying you for either, like age of thru hulls and or lord knows how many other things.
However you had a survey to insure, right? Did the surveyor point out the LFP system in the survey? Or did you modify the electrical system after you obtained coverage?
I’m not at all saying you did anything untold or underhanded, heck I never told the Insurence company about any of the mods I did to my boat from generator, Watermaker, Davits etc either.

[Maine Sail]

Originally Posted by a64pilot

So what chargers are there that can be controlled by a BMS?

On edit, cause I suspect few do, and to be well engineered means buying all new charge sources for most people?

Drop-In Catastrophic Protection - This is not controlling the charging it is about stopping it to prevent damage to the cells. It is a last ditch effort with drop-ins. We have a 40A Xantrex in the shop right now that I yanked off a boat two weeks ago. It no longer has a voltage regulation limit. Plug it in and the thing will push the batteries well over 17V. Stuff happens. Lucky for the customer he noticed the smell of cooking batteries before he let it do any other damage. Any AC charge source can be shut down on the AC input side including that Xantrex that ran away. Only a BMS that can externally trigger a relay can shut it down on the input side..

Day to Day Charging - For controlling voltage and current, a charger or charge source used with LFP should have user adjustable voltage and an absorption voltage duration that can be set to a bare minimum or to comply with the charge guidance.

For example Charge to 14.X Volts and allow current to taper to 0.05C (very few do this) or charge to 14.X Volts and absorb for 0-15 minutes (more can do this). Too many charge sources simply continue to absorb the batteries and this can be detrimental to the longevity of LFP.

[newhaul]

Originally Posted by a64pilot

They probably didn’t ask about a dozen other things that they could deny paying you for either, like age of thru hulls and or lord knows how many other things.
However you had a survey to insure, right? Did the surveyor point out the LFP system in the survey? Or did you modify the electrical system after you obtained coverage?
I’m not at all saying you did anything untold or underhanded, heck I never told the Insurence company about any of the mods I did to my boat from generator, Watermaker, Davits etc either.

no survey and it doesn't need one for me . Recall I am a retired shipwright and can do my own survey quite nicely.
Also I paid a grand for the boat and the 2015 9HP suzuki electric start . Which will be for sale as soon as I install the diesel.
So I got the boat for free by buying the motor.

[a64pilot]

OK so instead of disconnecting at the low voltage side, you do so at the high voltage side, so you need a relay for each charge source as opposed to just one relay.
Following that same logic than the alternator “problem” is easily solved, put the relay in the field circuit as opposed to the output circuit, that way you can shut down the alternator without harm?

Is there a decent “how to” on system design or planning?
This nuggimg it out individually is silly, makes for a lot of posts, but if there is a comprehensive how to, even if it’s one you buy, it might be worth obtaining.

Cause to be honest, most of the different “U tube” experts don’t know anymore about most stuff than I do, they read one source and regurgitate it as. If they did the design.

[a64pilot]

Why have absorption voltage adjusted it bare min? Why not adjust both absorption and float voltage to the desired voltage? Then terminate charging by removing power from the charger?

[a64pilot]

You know if you move to Fl, You would have much nicer weather and have more work than you would believe I think.

[Delfin]

Originally Posted by Maine Sail

It is not controlling the charging it is about stopping it to prevent damage to the cells. I have a 40A Xantrex in my shop right now that I yanked off a boat two weeks ago. It no longer has a voltage regulation limit. Plug it in and the thing will push the batteries well over 17V. Stuff happens. Lucky for the customer he noticed the smell of cooking batteries before he let it do any other damage. Any AC charge source can be shut down on the AC input side including that Xantrex..

For controlling, any charger used with LFP should have user adjustable voltage and an absorption voltage duration that can be set to a bare minimum or to comply with the charge guidance. For example Charge to 14.0V and 0.05C or charge to 14.0V and absorb for 0-15 minutes. Too many chargers simply continue to absorb the batteries and this can be detrimental to LFP..

What do you prefer for absorption voltage, set to minimum duration? I generally disconnect charging when pack voltage reaches 28 to 28.2, but I have the Balmar 624 set to 27.2 for 12 minutes (minimum), then float at 26.7. Sound ok?

[Maine Sail]

Originally Posted by Delfin

What do you prefer for absorption voltage, set to minimum duration? I generally disconnect charging when pack voltage reaches 28 to 28.2, but I have the Balmar 624 set to 27.2 for 12 minutes (minimum), then float at 26.7. Sound ok?

27.6V - 28V @ 12 minutes should be fine. 27.2V is a bit low and will have some absorption time if charge rate is high. Float at 26.7 is 3.33V which should also be fine for an alt regulator but not for prolonged duration such as shore charging etc.....