1400 Ah Lithium from cells

[senormechanico]

Originally Posted by kmacdonald

If nothing goes wrong but that hasn't been the case for most installs.

I guess I'm not one of the most installs. No over or under voltage disconnects, just periodic checking of voltages. 4s1p 12v 200aH.
I do have a bms with buzzer, but it never goes off.
Also I added a Cellog 8.
Solar for charging 90% of the year with various small loads 24/7.
13.8 absorb, 13.2 "float".
Going on 5 years or so, and it works.

[CatNewBee]

most installs I know still work flawlessly... very little trouble, some cell balancing modules needed a replacement, the system just shuts down. almost no cell issues known yet.

[kmacdonald]

Another trusted source of info: Assembling a Lithium Iron Phosphate Marine House Bank | | Nordkyn Design

[nebster]

Originally Posted by CatNewBee

Well, Victron, this is what I use in my setup for inverter and charger. 220A charger 5000W inverter, also the smart solar controller MPPT 150/100 and the BMV712. My BMS is from REC - a small startup in Slovenia, the cells are from Winston, the power relays are the one above and the interfaces between all of this stuff are homemade. also some custom programming to my needs by REC - whitch is simply awesome.

This is a great setup, and you obviously put a ton of study in and built up a well-designed system using components from lots of different manufacturers. I guess I am assuming the average cruiser will not want to invest all the effort that you did.

The quattro is fully configurable relating the charger and has 2 digital inputs, that can be programmed to a BMS interface that can be set teither to turn off charging or even better to switch to float. bulk set to 220A, Absorption to 14.0V, Float at 13.5, the rest is done by the BMS., it sends at 3.6V of a single cell a stop charge, the quattro goes to float, the bms actively balances all cells,

I've seen several folks very happy with their REC BMS. Personally I prefer to avoid active balancing and have taken advantage of that to set values such that we never enter the knee of the voltage curve. Do you know at what voltage your BMS begins active balancing?

Also, how big is your pack?

LVP set to 3.0V for the optocoupler output to shutdown inverter at 40% SOC - alternatively you can programm the quattro - or more reliable by the BMV relay.

How did you determine that 3.0v is 40% SOC? Is that under a load? 3.0v at rest with LFP should be closer to 2% SOC.

Also, just out of curiosity, what is your peak load and how much voltage sag do you get at the inverter inputs, if you've had a chance to observe?


Thanks for sharing some of your system. Maybe you should start a thread so we can be sure to give you your due.

[Ip485]

So, in an ideal world, cost aside, and as I am thinking of reworking my house setup, 730AHish of lithium and wanting to charge the bank as quickly as possible what is the largest charger it is worth buying, who makes chargers of this size (off the shelf) and what is the very quickest you could bring the batteries up to 100% from 90%, always given that my limiting factor is an 8KW Genset which I doubt is a consideration.

[nebster]

Originally Posted by Ip485

So, in an ideal world, cost aside, and as I am thinking of reworking my house setup, 730AHish of lithium and wanting to charge the bank as quickly as possible what is the largest charger it is worth buying, who makes chargers of this size (off the shelf) and what is the very quickest you could bring the batteries up to 100% from 90%, always given that my limiting factor is an 8KW Genset which I doubt is a consideration.

Can't say for sure.

1. This is a 12v pack?

2. How did you arrive at 730AH? That's a weird number.

3. Do you want just a charger, or do you want an inverter-charger?

4. Why do you want to go from 90 to 100% all the time? Maintaining LFP at 100% is usually not desirable. It's better to keep them below 95%, or even 90% if possible. The chemistry stays more stable when it's a little backed off of the top. Size your pack up 10% if you have to.

I have charge timing/voltage rise data for SOCs between 10% and about 92% at various C-rates between 0.1 and 0.5. I'm not interesting in charging to 100% and putting my pack at risk or necessitating active BMS hardware. I can't charge at much more than about .3C in real life, so higher rates aren't something I've tested too much, but I'm sure others have that info. Once you get more specific about your pack and cells via the questions above, I can share some specific example data, though.

5. Regardless, topping off the very tip-top of the pack is best done at lower rates. That keeps the voltage rise (above open circuit) down. The last little bit is a very sensitive area. So, go back and see #4.

I think Victron makes the best inverter-chargers for people willing to put in the time to learn them. But DC charging is not rocket science, so if you have another component that can manage charge (coulomb counter, BMS) you can even just use a straight power supply and some control relays. There isn't a single best answer for all circumstances.

If cost is no object, maybe just buy a fully-managed Lithionics pack with Bruce Schwab's dual-bus BMS, or Victron's LFP pack and BMS, and then go with one or two Victron I-Cs. The "right answer" can shift a little depending on whether you need to accommodate 120V, 240V, or split-phase power.

[kmacdonald]

Originally Posted by Ip485

So, in an ideal world, cost aside, and as I am thinking of reworking my house setup, 730AHish of lithium and wanting to charge the bank as quickly as possible what is the largest charger it is worth buying, who makes chargers of this size (off the shelf) and what is the very quickest you could bring the batteries up to 100% from 90%, always given that my limiting factor is an 8KW Genset which I doubt is a consideration.

Charging at 0.5C or 365A would charge it in about 2 hours. I would guess a 365A charger would cost quite a bit and may burn itself up on a LiFePO4 bank. That's one of the problems with large banks, how to charge them quickly with reasonably sized and priced chargers. A more realistic 180A charger or .25C would charge it in about 4 hours. There is no need to get to 100% SOC like LA batteries and is probably best if you don't try to get to 100%. Shoot for 90 or 95% to be safe. It only takes one overcharge or discharge to ruin the bank. There aren't and second chances with them.

There are those that say a BMS will prevent that from hapening. If it works correctly it will but there a plenty of stories of BMS's failing and destroying the bank they were meant to protect. From the threads on LiFePO4 it is obvious that some cruisers are fully familiar with an implementation of LiFePO4 and know the risks, rewards, and everything in between. Then there are those that don't care, have deep pockets, and "Just Want" LiFePO$ because it is the latest and greatest. And then there are the clueless.

Those with a great deal of experience cruising know 6V golf cart batteries offer a lot of bang for the buck and require minimal attention. It's a great entry level house bank and all a lot will ever use.

If you are in the market for a new house bank and LiFePO4 is on the short list, please read all the links in this thread and then some before making a decision. The few anecdotal cases presented here are really meaningless. In fact, I doubt anyone here has gone thru a full life cycle with LiFePO4 except of course the premature disasters.

[kmacdonald]

Originally Posted by senormechanico

I guess I'm not one of the most installs. No over or under voltage disconnects, just periodic checking of voltages. 4s1p 12v 200aH.
I do have a bms with buzzer, but it never goes off.
Also I added a Cellog 8.
Solar for charging 90% of the year with various small loads 24/7.
13.8 absorb, 13.2 "float".
Going on 5 years or so, and it works.

Hmmmmm a Dragonfly. I guess weight wasn't a consideration for choosing LiFePO4. That's what I would consider a reasonably size LiFePO4 bank. Equivalent to about a 400Ah LA bank.

[LoudMusic]

Originally Posted by kmacdonald

Charging at 0.5C or 365A would charge it in about 2 hours. I would guess a 365A charger would cost quite a bit and may burn itself up on a LiFePO4 bank. That's one of the problems with large banks, how to charge them quickly with reasonably sized and priced chargers. A more realistic 180A charger or .25C would charge it in about 4 hours. There is no need to get to 100% SOC like LA batteries and is probably best if you don't try to get to 100%. Shoot for 90 or 95% to be safe. It only takes one overcharge or discharge to ruin the bank. There aren't and second chances with them.

There are those that say a BMS will prevent that from hapening. If it works correctly it will but there a plenty of stories of BMS's failing and destroying the bank they were meant to protect. From the threads on LiFePO4 it is obvious that some cruisers are fully familiar with an implementation of LiFePO4 and know the risks, rewards, and everything in between. Then there are those that don't care, have deep pockets, and "Just Want" LiFePO$ because it is the latest and greatest. And then there are the clueless.

Those with a great deal of experience cruising know 6V golf cart batteries offer a lot of bang for the buck and require minimal attention. It's a great entry level house bank and all a lot will ever use.

If you are in the market for a new house bank and LiFePO4 is on the short list, please read all the links in this thread and then some before making a decision. The few anecdotal cases presented here are really meaningless. In fact, I doubt anyone here has gone thru a full life cycle with LiFePO4 except of course the premature disasters.

Well, considering the expected life span, it'd be hard for someone to "naturally" deplete LiFePO4 cells. They were only invented about 20 years ago, and products took some time to be produced

[nebster]

It is really hard to find good long-term data on LFP. We have to rely mostly on anecdote. Here is a great update on a 7-year-old LFP prismatic pack in an EV, 7.5kWh, discharged up to 6C (!). Fortunately, we are much gentler on our packs as house power systems.

Now BMS free! - DIY Electric Car Forums

[senormechanico]

Originally Posted by kmacdonald

Hmmmmm a Dragonfly. I guess weight wasn't a consideration for choosing LiFePO4. That's what I would consider a reasonably size LiFePO4 bank. Equivalent to about a 400Ah LA bank.

Going to Lithium changed our boat for the better in many ways.
The watermaker outputs more, all the systems work better, charging is quicker, I could go on and on.
NO holes in my levi's or t shirts !

[kmacdonald]

Originally Posted by senormechanico

Going to Lithium changed our boat for the better in many ways.
The watermaker outputs more, all the systems work better, charging is quicker, I could go on and on.
NO holes in my levi's or t shirts !

Yep, they check all the boxes for marine batteries except fault tolerance. My boat lost about 45 pounds when I switched to LiFePO4.
Do you think 100Ah bank would be adequate without refrigeration?

[kmacdonald]

Originally Posted by senormechanico

I guess I'm not one of the most installs. No over or under voltage disconnects, just periodic checking of voltages. 4s1p 12v 200aH.
I do have a bms with buzzer, but it never goes off.
Also I added a Cellog 8.
Solar for charging 90% of the year with various small loads 24/7.
13.8 absorb, 13.2 "float".
Going on 5 years or so, and it works.

What is your algorithm for switching from absorption to float? What solar controller?

[john61ct]

LFP should not get Float, they shouldn't even sit anywhere near Full.

If Float can't be turned off, set below resting V.

[kmacdonald]

Originally Posted by john61ct

LFP should not get Float, they shouldn't even sit anywhere near Full.

If Float can't be turned off, set below resting V.

Resting full is about 13.36 for my bank so 13.2 float is doing nothing. Keeping them fully charged will have an impact on their life but we really don't know how much. I would guess it is significant since the manufacturers say to store them half full but it may or may not matter to some depending how much it reduces battery life. There are a lot of unknowns with LiFePO4 but it appears that they are exactly what cruisers want with the exception of fault tolerance.