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

[Simi 60]

Originally Posted by wholybee

Which provides no warning of a cell level over or undervoltage issue. I am perfectly happy using a victron battery monitor, but it is not acceptable according to the standard because it only monitors the complete battery, not cells.

True but as a responsible full time cruiser and operator I monitor the batteries and individual cells several times a day anyway.

[wholybee]

Originally Posted by hjohnson

I would argue that the job of a BMS is to control your charge sources and loads so that a disconnect will never occur. My BMS sets the voltage and current limits which are in turn used by my alternator, MPPTs, and Inverter/Charger.

I argue that different. With properly setup charge sources, a disconnect will never occur, and the BMS isn't even necessary. It is there as a "last resort" in case a charge source fails somehow. I am 2 years on LFP, and not a single disconnect.

IMHO, having the BMS control everything adds unnecessary complexity, and doesn't offer greater reliability or cell life. The only "control" it should have is to stop the alternator before a disconnect. That has worked well for me, ymmv.

I don't even monitor my BMS anymore, just check it once a month and see still no disconnects, and my cells are still balanced. LFP is a world apart from lead. All those habits of monitoring your battery everyday can die just as lead is dead.

[Simi 60]

Originally Posted by wholybee

I argue that different. With properly setup charge sources, a disconnect will never occur, and the BMS isn't even necessary. It is there as a "last resort" in case a charge source fails somehow. I am 2 years on LFP, and not a single disconnect.

IMHO, having the BMS control everything adds unnecessary complexity, and doesn't offer greater reliability or cell life. The only "control" it should have is to stop the alternator before a disconnect. That has worked well for me, ymmv.

Same for us
And we don't use alt for charging
But mppt and charger on Genset are set to shut off charge first.

I don't even monitor my BMS anymore, just check it once a month and see still no disconnects, and my cells are still balanced. LFP is a world apart from lead. All those habits of monitoring your battery everyday can die just as lead is dead.

Old habits die hard

[rgleason]

Quote from an earlier post:

I would like to know if anyone uses Dakota Lithium Batteries.

https://dakotalithium.com/prod...2v-...cycle-battery/

This battery is quoted at 277 amp hours and is in an ideal case size,...

----

This hits all the needs for a majority of boaters, except it is too expensive and it has no advance shutdown signal!

Why are the manufacturers so thick?
They should grab the opportunity, make an ABYC compliant dropin that can properly signal an LFP designed regular to shutdown before LFP shutdown!

They are not listening to the market and are thereby causing unsafe installations. Bad installation of Dropins could become a black eye on use of LFP.

[s/v Jedi]

Originally Posted by wholybee

Which provides no warning of a cell level over or undervoltage issue. I am perfectly happy using a victron battery monitor, but it is not acceptable according to the standard because it only monitors the complete battery, not cells.

That can be argued. If you have a model with the AUX input, normally used to measure voltage of a start battery, you can instead connect that to the battery midpoint, i.e. the middle cell like cell 2 positive in a 4S 12V battery. Then in setup you configure it for midpoint monitoring and set alarms for how many mV is acceptable.

Now you monitor cel balance. You don’t know the exact voltage of each cell, but you know if they are out of balance or not. I’m pretty sure you can configure the BMV relay to trigger on such an alarm and there you are: compliance with ABYC.

The catch: you need access to cell terminals or at least the balance wiring.

[newhaul]

Originally Posted by rgleason

Quote from an earlier post:

I would like to know if anyone uses Dakota Lithium Batteries.

https://dakotalithium.com/prod...2v-...cycle-battery/

This battery is quoted at 277 amp hours and is in an ideal case size,...

----

This hits all the needs for a majority of boaters, except it is too expensive and it has no advance shutdown signal!

Why are the manufacturers so thick?
They should grab the opportunity, make an ABYC compliant dropin that can properly signal an LFP designed regular to shutdown before LFP shutdown!

They are not listening to the market and are thereby causing unsafe installations. Bad installation of Dropins could become a black eye on use of LFP.

A couple things. First the link is broken on Dakota side
Second what ABYC standard ? Remember these batteries were designed and all parts ordered and prepared a year or so ago. Takes time to retool a production line.
Now when did the ABYC issue a definitive recommendation?

[goboatingnow]

Originally Posted by newhaul

A couple things. First the link is broken on Dakota side

Second what ABYC standard ? Remember these batteries were designed and all parts ordered and prepared a year or so ago. Takes time to retool a production line.

Now when did the ABYC issue a definitive recommendation?

Recently approved standard E-13

[newhaul]

Originally Posted by goboatingnow

Recently approved standard E-13

Not really approved standard but yes several recommendations no requirements .
Issued on August 8th 2022 and E-13’s recommendations take effect for systems manufactured or installed after July 31, 2023. So any installs done before that date are grandfathered in .
BTW you realise my post was in direct reply to rgleason and his question why manufacturers have not already done this . We'll lastly it is a recommendation not a requirement.

[goboatingnow]

Originally Posted by newhaul

Not really approved standard but yes several recommendations no requirements .

Issued on August 8th 2022 and E-13’s recommendations take effect for systems manufactured or installed after July 31, 2023. So any installs done before that date are grandfathered in .

BTW you realise my post was in direct reply to rgleason and his question why manufacturers have not already done this . We'll lastly it is a recommendation not a requirement.

Fully agree ABYC E-13 isn’t well thought out and conflates all forms of Li. If it can be ignored , I’d ignore it.

[newhaul]

Originally Posted by goboatingnow

Fully agree ABYC E-13 isn’t well thought out and conflates all forms of Li. If it can be ignored , I’d ignore it.

Since my system is safe and well designed for my vessel and my use and will be grandfathered in and my insurer doesn't care i have no worries.

[goboatingnow]

Originally Posted by newhaul

Since my system is safe and well designed for my vessel and my use and will be grandfathered in and my insurer doesn't care i have no worries.

Yes I think that’s best

[Mongo_at_sea]

Hi All, attached is a diagram of a simple system I am in process of installing. The idea is lead acid and LIFEPO4 are totally isolated, except that either source (but not both at the same time) can power house loads. Only lead acid is connect to engine.
any comments? Switch 1 is always left ON except for maintenance work. Switch 2 always left as LIFEPO4 as source, except at dock when house loads can be powered by charger through Lead Acid battery.

[CaptainRivet]

Originally Posted by wholybee

I argue that different. With properly setup charge sources, a disconnect will never occur, and the BMS isn't even necessary. It is there as a "last resort" in case a charge source fails somehow. I am 2 years on LFP, and not a single disconnect.

IMHO, having the BMS control everything adds unnecessary complexity, and doesn't offer greater reliability or cell life. The only "control" it should have is to stop the alternator before a disconnect. That has worked well for me, ymmv.

I don't even monitor my BMS anymore, just check it once a month and see still no disconnects, and my cells are still balanced. LFP is a world apart from lead. All those habits of monitoring your battery everyday can die just as lead is dead.

Your charge sources only know the total voltage of your bank which can be catastrophic eg one cell defect and others overcharged still makes your 13.8V but your BMS knows the voltage,amps load,charge amps and SOC of each cell so it is the masterbrain in your System and MUST Control load and charge. It doesn‘t add complexity, it actually makes it simpler eg my Electrodacus just switches on/off all the charge sources and loads (based on SOC if I want) based on the BMS Parameters that are the same for all charge sources. mine are all Victron so I use the factory tested remote on/off functionality so the source itself gets switched (not on the high amp side) without any expensive additional Relais.
Only the Legacy load side is switched via a Victron battery protect. All charge sources own control parameter are used as 2nd security fallback in case BMS or remote functionality fails (switched on always on high, so If cable gets disconnected or any other contact interruption the source is and stays off).
As I keep lead starter/service battery anyhow, solar is main charge source I opted for Victron DC2DC for alternator charge which BMS can also easily switch off.
The whole loads can be switched with one switch from the Lithium to the lead…this has 2 functions 1)backup in case lithium disconnects and 2) if I leave the vessel for longer I switch all loads to the lead (so eg bilge pumps work) and Discharge LFP to approx 40%SOC with inverters and then disconnect the Lithium battery completely. So nothing can happen to LFP bank but still all necessary stuff works, in worst case cheap lead is dead. Means also LFP just works when I am on board and able to monitor it personally and can take actions in case of problems.

[CaptainRivet]

Originally Posted by Mongo_at_sea

Hi All, attached is a diagram of a simple system I am in process of installing. The idea is lead acid and LIFEPO4 are totally isolated, except that either source (but not both at the same time) can power house loads. Only lead acid is connect to engine.
any comments? Switch 1 is always left ON except for maintenance work. Switch 2 always left as LIFEPO4 as source, except at dock when house loads can be powered by charger through Lead Acid battery.

Due to your drawing you need a seperate connection between starter and lead with the switch 1.
Switch 2 connects directly to the lead, not to the switch.

But you don‘t have the LFP house as emergency backup, which you should have.
does your BMS have enough amperage so you can start from the LFP…you need minimum 400A, better 600A peak and the often FET based cut off Relais can be damage by the surge of the starter. One of main reasons I choose Electrodacus BMS as it’s no current caring as I will soon throw out Lead completely and start from the LFP.

[newhaul]

Originally Posted by CaptainRivet

But you don‘t have the LFP house as emergency backup, which you should have.
does your BMS have enough amperage so you can start from the LFP…you need minimum 400A, better 600A peak and the often FET based cut off Relais can be damage by the surge of the starter. .

Why ?
My system will not be setup for the lifepo4 bank to start the engine if the lead is dead
I have 2 of these on the boat for emergent needs .
https://www.ebay.com/itm/20000mAh-Ca...edirect=mobile