Your Lifepo4 just hit 80% depth of Discharge, how were you informed?

[Fuss]

You're sailing along not a care in the world and behind the scenes your Lifepo4 just hit 80% depth of Discharge.


How were you informed?

What procedures now took place?
Were any of these procedures automated?


I am just interested to know how others are handling this....


or is it as simple as, an alarm down below went off and I started the motor and had a bit of a look at the battery monitor for the next few hours and once the capacity was looking better, I switch the motor off and went back to the sailing.

[ThereAndBack]

Umm, forgive me but what does this have to do with lifepo4 batteries?



Any battery that is discharged to the "alarm" threshold will alert. (Provided you have an alarm and have it setup correctly, otherwise you won't know unless you manually check.)



The procedure is the same for all of them. Charge them or stop consuming power until you are able to charge them.

[wholybee]

My Victron BMV is set to alarm at 10% SOC. I've never really hit that though.

[Fuss]

Originally Posted by ThereAndBack

Umm, forgive me but what does this have to do with lifepo4 batteries?



Any battery that is discharged to the "alarm" threshold will alert. (Provided you have an alarm and have it setup correctly, otherwise you won't know unless you manually check.)



The procedure is the same for all of them. Charge them or stop consuming power until you are able to charge them.

Thanks, I am just interested if others have changed their thinking and procedures for Lifepo4 as opposed to the times they had lead acid.

[ThereAndBack]

Originally Posted by Fuss

Thanks, I am just interested if others have changed their thinking and procedures for Lifepo4 as opposed to the times they had lead acid.

Honestly, I've never run my lifepo4 bank down low enough to alert but I wouldn't be shy about running them down to less than 5% honestly. They're not like the old FLA.

[Avionics_Joe]

I don't have a BMS, I have set the Victron multiplus to turn off at a low voltage condition, usually is about 40 %. then I get emails from the Victron Venus then I get redundant alarms for low SOC.

[wholybee]

Originally Posted by Fuss

Thanks, I am just interested if others have changed their thinking and procedures for Lifepo4 as opposed to the times they had lead acid.

Absolutely I have changed my thinking. But diligent management will not let your batteries go too low, not because it will damage them, but because I don't want the lights to go out.

The big change is that I don't worry about getting to 100%.

[SailingHarmonie]

The question as phrased does not compute. The idea that my batteries could drop to a SOC that was so low it triggered the alarm without me being fully aware it was going to happen is just foreign to me. Kind of like being "surprised" by a low fuel light coming on when motoring down the highway. I am pretty tuned in to our batteries, at any point in time--without looking at the gauges--I could probably tell you the SOC within 5%.

But... more in the spirit of the OP's question: When my batteries get down to the lowest "normal" state of charge, the generator starts automatically, and runs until the charge acceptance drops to the point where I know they are about 93% charged. This is not a lithium bank, but my logic would be very similar if they were (although the settings might well be different).

All this is controlled by a Victron Cerbo. The generator is a WhisperPower 3.5kW DC genset that runs through its autostart cycle when the Cerbo closes a relay, and continues to run until that relay opens.

Here is the logic: From 0600 to 1800 the generator comes on if the SOC drops below 65%. In our world this effectively means the generator starts every other day at 0600. Outside those hours, the generator will start if the SOC drops below 55%, I can not remember the last time this happened.

The generator runs until the charge acceptance drops to a level I have found equates with 93% SOC. I use charge acceptance rate, because it is a very accurate indication of SOC for these AGM style batteries. From 93%, a normal solar day takes me to 100% by the end of the day.

This system has worked well for us for almost 3 years. When these batteries die, eventually, I'll probably go with Li, but that is a long way away, and its way too early to predict what will be state of the art at that point.

[LoudMusic]

Victron BMS beeps. Loads continue to draw. I had to manually intervene.

[sailorboy1]

Originally Posted by wholybee

My Victron BMV is set to alarm at 10% SOC. I've never really hit that though.

My is set at 30%, which pretty low considering I haven't been below 50%

Depending what I am doing to would the engine or the Honda, or both

[Pete7]

Not much, as the LFP drops the lead-acid wired in parallel takes over. Eventually the chart plotter will bleep and I suppose its time to start the engine or investigate why the solar isn't keeping up.

Pete

[Maine Sail]

Originally Posted by ThereAndBack

Honestly, I've never run my lifepo4 bank down low enough to alert but I wouldn't be shy about running them down to less than 5% honestly. They're not like the old FLA.

My bank will be 14 years old in May (built in 2009). It has over 2200 cycles most all to at least 80% DoD and 100+ cycles to 0%.... Still delivers 100% of it 400Ah rating...I no longer worry about DoD. Just use them. As long as you are not over charging or hitting the BMS with huge inrush currents They will most likely outlive your boat...

I am currently designing a system for our off-grid farm in Northern Maine. The design will be to cycle to 90% DoD.It will be charged by a massive Solar array and as a back up a diesel generator. The Barn is already solar/battery.

We start clearing stumps etc. for the Array this spring...

[wholybee]

Originally Posted by Maine Sail

My bank will be 14 years old in May (built in 2009). It has over 2200 cycles most all to at least 80% DoD and 100+ cycles to 0%.... Still delivers 100% of it 400Ah rating...I no longer worry about DoD. Just use them. As long as you are not over charging or hitting the BMS with huge inrush currents They will most likely outlive your boat...

I am currently designing a system for our off-grid farm in Northern Maine. The design will be to cycle to 90% DoD.It will be charged by a massive Solar array and as a back up a diesel generator. The Barn is already solar/battery.

We start clearing stumps etc. for the Array this spring...

Sage advice. Thank you.

[SailingHarmonie]

Originally Posted by Maine Sail

My bank will be 14 years old in May (built in 2009). It has over 2200 cycles most all to at least 80% DoD and 100+ cycles to 0%.... Still delivers 100% of it 400Ah rating...I no longer worry about DoD. Just use them. As long as you are not over charging or hitting the BMS with huge inrush currents They will most likely outlive your boat...

If there is ANYBODY to listen to on LiFePO batteries... this is the guy.

[Simi 60]

Originally Posted by wholybee

My Victron BMV is set to alarm at 10% SOC. I've never really hit that though.

And they aren't accurate anyway.
At least our victron isn't.
It always reads quite a bit different to the JBD BMS Bluetooth app