LiFePO4 reference diagram

[zurk]

heres mine.

[s/v Jedi]

Originally Posted by Baronkrak

So you adapt. Scenario: on the Reference Diagram, one cell in one of the LiFePO4 battery trigger a load disconnect and open the switch associated with that battery. Then how do you recharge that battery, the switch is in an open state?

I remove the loads, then switch the battery back on the bus manually, then charging starts automatically from solar, dc-dc etc.

The only time I did this was during a simulated test, because it never happens for real.

[newhaul]

Originally Posted by zurk

heres mine.

What is this spider web? Seems you have loads and charging sources going everywhere. Can you clean it up so it's actually readable?
Now do it using a single engine as the charging source .
Unless this is specific to your vessel then please give a writeup that I can use to do my job as a mechanical engineer and actually make it work .
In your own thread please

[Baronkrak]

Originally Posted by newhaul

Can you clean it up so it's actually readable?

There is nothing wrong with the presentation.
Searching “Victron lynx 500" may help.

[newhaul]

Originally Posted by Baronkrak

There is nothing wrong with the presentation.
Searching “Victron lynx 500" may help.

When one does an installation diagram for others to reference one should not be required to look at any other data just to decipher the diagram .
You would likely really hate my wiring setup if I were to draw it out . But at least it would be easy to understand at a glance .
And no I don't have it drawn out . No desire to either .

[Baronkrak]

Originally Posted by newhaul

When one does an installation diagram for others to reference one should not be required to look at any other data just to decipher the diagram .

One needs to be competent.

Originally Posted by zurk

mine is designed by an electrical engineer.

[goboatingnow]

Originally Posted by Baronkrak

Can you quote the value of that very low cell voltage?

Under 20%SOC ( true SOC ) , Li needs a prequalifying charge at typically < 0.01C until approx 20 % Soc normal higher C charge can then recommence

( LVE is defined in the ISO spec as a situation where the voltage is at or below the minimum allowed by the manufacturer )

My view as expressed many times is LVE and HVE are extremely unlikely ,

but when they do happen they are serious safety trips.

Charging sources should have long before LVE started recharging. Similarly loads should be disconnected in order of priority long before LVE

equally with HVE , charge sources should have stopped well before this point

Hence if these events are tripped I’m of the professional opinion that the battery should be inspected before any charge source or load is automatically reconnected ( or remains connected )

[Baronkrak]

Originally Posted by goboatingnow

Under 20%SOC ( true SOC ) , Li needs a prequalifying charge at typically < 0.01C until approx 20 % Soc normal higher C charge can then recommence

( LVE is defined in the ISO spec as a situation where the voltage is at or below the minimum allowed by the manufacturer )

My view as expressed many times is LVE and HVE are extremely unlikely ,

but when they do happen they are serious safety trips.

Charging sources should have long before LVE started recharging. Similarly loads should be disconnected in order of priority long before LVE

equally with HVE , charge sources should have stopped well before this point

Hence if these events are tripped I’m of the professional opinion that the battery should be inspected before any charge source or load is automatically reconnected ( or remains connected )

A voltage value if possible.

[goboatingnow]

Originally Posted by Baronkrak

A voltage value if possible.

Typically 2v or less

[s/v Jedi]

Huh? <20% SOC equals < 2.0V ?

At 20% SOC a lfp cell has 3.2V

At 0% SOC a lfp cell has 2.5V

[Baronkrak]

Originally Posted by goboatingnow

In particular LVC should not be designed as a charge start point. This should happen way before LVC.

When the voltage alarm (cell voltage adjustable between 2.6V and 2.8V) is set at 2.8V could this setting be used as a charge start point?

https://www.solacity.com/how-to-keep...tteries-happy/

https://www.evworks.com.au/page/tech...-lithium-batt/

https://cleversolarpower.com/lifepo4-voltage-chart/

[Kit_L]

@ s/v Jedi (love the Yoda quote),

Thinking aloud here; Eric Bretcher and others claim that LiFePO batteries last the best when discharged from full to 10% charge or so, then recharged. Many systems recharge these batteries long before the 10% level is reached. I am wondering whether your two-bank system can allow for this, if this claim is accurate. Is this any kind of problem in your view?

Then I was wondering if having a fully charged, but modestly sized FLA system might provide the emergency backup that will be needed if the Lithium BMS detects a fault and disconnects the system. I know you have mentioned an alarm scenario, in advance of this happening, but I wonder if an alarm plus automatic switching over to the backup FLA system might obviate the need for the second LiFePO bank?

[goboatingnow]

Originally Posted by Baronkrak

When the voltage alarm (cell voltage adjustable between 2.6V and 2.8V) is set at 2.8V could this setting be used as a charge start point?



https://www.solacity.com/how-to-keep...tteries-happy/



https://www.evworks.com.au/page/tech...-lithium-batt/



https://cleversolarpower.com/lifepo4-voltage-chart/

I would have the LVE well below the charge start point

[goboatingnow]

Originally Posted by Kit_L

@ s/v Jedi (love the Yoda quote),

Thinking aloud here; Eric Bretcher and others claim that LiFePO batteries last the best when discharged from full to 10% charge or so, then recharged. Many systems recharge these batteries long before the 10% level is reached. I am wondering whether your two-bank system can allow for this, if this claim is accurate. Is this any kind of problem in your view?

Then I was wondering if having a fully charged, but modestly sized FLA system might provide the emergency backup that will be needed if the Lithium BMS detects a fault and disconnects the system. I know you have mentioned an alarm scenario, in advance of this happening, but I wonder if an alarm plus automatic switching over to the backup FLA system might obviate the need for the second LiFePO bank?

90% DoD severely eats into battery life for Li

[goboatingnow]

Originally Posted by s/v Jedi

Huh? &lt;20% SOC equals &lt; 2.0V ?



At 20% SOC a lfp cell has 3.2V



At 0% SOC a lfp cell has 2.5V

Yes it’s a typo wasn’t paying attention as I said around Soc of 20% or less a low C prequalifying charge should be applied to bring the batteries to 20 %