Inrush current on LiFePO4

[lateral]

Searched but couldn't find. Battery EVE LF280K BMS JBD 200A
Bearing in mind this is a KIS system with user monitoring.
For emergency start and capstan use I want to have access to house bank.
Could a house bank sustain the inrush for a DC motor that draws 80A in running mode, considering that the inrush could be 10x that for several seconds? My fluke measured 150A inrush on 3GM30 start. Although I suspect for msec it is much higher.
I was considering a circuit that has the secondary of a contactor direct to the
Lithium battery with the primary switched to load side of the BMS and forgo over discharge current protection. Battery spec is 2C for 30sec. Starter motor the same
Argofet and SLA for start. Three switch. Im aware of not paralleling Lithium and discharged SB.
Curious how people dealt with this.
Electrodacus are currently not available.

[GordMay]

Yes.
Cranking Amps [MCA @ 32°F, or CCA at 0°F] is the discharge load in amperes that a new, fully-charged battery can deliver for 30 seconds, while still maintaining terminal voltage equal to or higher than 1.20 volts per cell [7.2 v @ 12V nominal].
Even smaller batteries have a CCA of at least 600 A [±800 MCA].

[PaulCrawhorn]

delete brain fart

[lateral]

Apologies for the incoherent post above.
Thanks Gordon, but you are talking about LA, right?
Without the voltage sag with Li, is the inrush even higher?

All I need to know is whether LiFePO4 tolerate inrush from inductive motor loads in a sailboat installation.

[Mike Banks]

Just put a big bank of capacitors across the circuit. That will help the inrush thing.

[Moontide]

Have to check the specs on the BMS. That is where most issues arise since many are not designed to handle the big inrush loads. MarineHowTo.com has a good white paper on this.

[boatpoker]

Originally Posted by Moontide

Have to check the specs on the BMS. That is where most issues arise since many are not designed to handle the big inrush loads. MarineHowTo.com has a good white paper on this.

Rod Collins superb article goes into inrush issues. A must read for anyone contemplating LiFePO4.
https://marinehowto.com/drop-in-life...H32DJ8ou31yVsc

[team karst]

I have my nitpicker out
From the battery view, it is an outrush current. Or, an inrush load.

[goboatingnow]

Originally Posted by team karst

I have my nitpicker out
From the battery view, it is an outrush current. Or, an inrush load.

Loads determine currents , not sources , hence its always an inrush current

[CatNewBee]

Originally Posted by lateral

Searched but couldn't find. Battery EVE LF280K BMS JBD 200A
Bearing in mind this is a KIS system with user monitoring.
For emergency start and capstan use I want to have access to house bank.
Could a house bank sustain the inrush for a DC motor that draws 80A in running mode, considering that the inrush could be 10x that for several seconds? My fluke measured 150A inrush on 3GM30 start. Although I suspect for msec it is much higher.
I was considering a circuit that has the secondary of a contactor direct to the
Lithium battery with the primary switched to load side of the BMS and forgo over discharge current protection. Battery spec is 2C for 30sec. Starter motor the same
Argofet and SLA for start. Three switch. Im aware of not paralleling Lithium and discharged SB.
Curious how people dealt with this.
Electrodacus are currently not available.

The power logic defines the maximum current, LFP batteries with internal BMS have usually small-ish FET transistors to disconnect the cells for protection, they are the weak point. REC, ELECTRODACUS VICTRON etc create BMS with external logic, you can choose eithe FET / SSR or solenoids that suit your power needs. The cells itself can handle 3C charge/discharge continous, and up to 10C for 10 seconds.

So 100Ah could deliver 1000A for 10s without sweat, but the FET inside of the internal BMS can handle only 50A or 100A. Thats why I call drop-in LFP crippled batteries.

If you want high inrush, build from cells and choose external BMS and solenoids.

It is not the lithium cell, but the electronics put inside.

You can parallel lithium batteries without issues, but not all can be set up in series, the FET have voltage limitations and the balancers work in a very small operation range. Serial configurations need a high voltage range on the BMS to not freak out.

You can even bypass the protection circuits during crancking the engine if you want to use SSR / FET for the BMS to control normal loads / charge sources by going straight from the cells to the starter.

[Simi 60]

The 200 amp JBD BMS we are using on our install are solenoid not FET
EVE LF280k @ 24v X 3 for 840ah @ 24v

[CatNewBee]

Originally Posted by Simi 60

The 200 amp JBD BMS we are using on our install are solenoid not fet

Then you can upgrade to 500A solenoids easily. Or bypass it for starting if necessary.

[Moontide]

Lateral - ck the article from HowTo Marine. Someone posted the link earlier in the thread. Addresses your question directly, including the issue of small/not enough FET's in most BMS's

[lateral]

My system is going to be KIS. It has higher user participation and inherent risk.
4x EVE LF280k's, SLA start, Argo fet, between. MC614 alt charge control.
JBD 200A bms. SG200 BM with audible alarms.

The emergency start and windlass circuits (Solenoids) will have manual HC switches direct to +- ve terminals of LiFePO4 by passing BMS and will be off 99.9% of time and slow blow fused at 140% of run current. Possibly with "T" class upstream.

Please, offer up suggestions to improve this proposed choice.
Don't need the improbables, bullet proof, esoteric stuff.
I know of LiFePO4 being used with factory alts,no bms and a cheep V/A meter.
Definitely hands on system.
Sorry repeating myself, as first post was unco.

[lateral]

Originally Posted by Moontide

Lateral - ck the article from HowTo Marine. Someone posted the link earlier in the thread. Addresses your question directly, including the issue of small/not enough FET's in most BMS's

Yep have done and will again. Electrodacus are not available so besides relying
on the supposed 200A supporting FETs in the JBD bms, I dont know how to limit the no more than 2C for 30sec spec of EVE without major expenditure/electronic overkill..