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

[exMaggieDrum]

Originally Posted by JBPohle

Regarding CALB cells. I mentioned it before, but the guys at EVTV were great. Ordered 16ea CALB CA180FI's came in a week all at exactly 3.28volts. They can seem to get them as needed here in the US. Nice guys and the braided connectors are really nice. We're now customizing the hold they will live in. Next up I think we are going to go with a new Victron 230V, 5kw inverter and an auto transformer. Still planning where all of this equipment will be mounted.

Good luck ExMaggieDrum at some point you will just need to pull the trigger and get started. I've been circling the drain for year and just got started.

Sent from my iPad using Cruisers Sailing Forum

Thanks JB, I am going to contact Voltronix today and see if I can get cells. I'm ready to go. I understand your drain circling.

I know I have been somewhat of a pain with my many long posts and my confusion to the rest of you. My apologies if anyone has been annoyed. I was told by Winston in China that there were zero distributors for their cells in the US so it was easy for me to get mixed up on Maine Sail's previous note that Voltronix was actually selling Winstons with their label on them. For some reason, my extensive searches for lithium cells never showed them.

I'm going to go dark now while I get these cells ordered. I'll post my success and then go dark again while I install them.

Thank you all for your help!!

Joe

[rfadler]

Joe,

If you end up going with Voltronix send me a PM. I just bought four 700Ahr cells and am trying to figure the most economical way to ship them to Seattle. I see you are in Anacortes. Perhaps we can work together on shipping and save some $$.

[exMaggieDrum]

Originally Posted by rfadler

Joe,

If you end up going with Voltronix send me a PM. I just bought four 700Ahr cells and am trying to figure the most economical way to ship them to Seattle. I see you are in Anacortes. Perhaps we can work together on shipping and save some $$.

Rick, I had a great conversation with Brennan yesterday. He offered to sell me 16 used 100Ah cells for $100 each. They were in automotive service for 2 years and on the shelf some time. New ones are $135 each. That is quite a big savings. He does not have new ones in stock and says there is a 8-12 week lead time. The savings from new and used are certainly significant. I asked him about whether he knew if they had ever been abused and he said absolutely not. I am nervous about that though. He did say he would swap a bad cell for another used one if need be. That would be quite a hassle to rebalance the cells then but I am thinking about it. I am disappointed he does not have new ones in stock. I will keep you posted after I make a decision and get a lead time on delivery (if new). The used ones are available for immediate shipment. I'll know soon.

[CarstenWL]

Hi,

I will finally install my 400Ah Winston cells soon (4S). Have been playing with the cells 'here in the office' for some time.

I will use a Victron MultiPlus 12/3000/16 Charger/Inverter as my charging source when in port (or powered by a portable generator as a back-up at sea) and a alternator/Serpentine kit with MC-614 on my engine when motoring out of a port / into a port.

What is the best way to 'deactivate' the alternator/MC-614 when the LiFePO4 battery is fully charged (and I still have to motor) or if I do not want the alternator to charge because I am still at a high percentage of SOC?

What is the best to do in a HVC event?

Sorry if these questions were answered b4 and I overlooked this.

Thanks for a possible reply,

regards

Carsten

[ScottMeilicke]

Originally Posted by CarstenWL

Hi,

I will finally install my 400Ah Winston cells soon (4S). Have been playing with the cells 'here in the office' for some time.

I will use a Victron MultiPlus 12/3000/16 Charger/Inverter as my charging source when in port (or powered by a portable generator as a back-up at sea) and a alternator/Serpentine kit with MC-614 on my engine when motoring out of a port / into a port.

What is the best way to 'deactivate' the alternator/MC-614 when the LiFePO4 battery is fully charged (and I still have to motor) or if I do not want the alternator to charge because I am still at a high percentage of SOC?

What is the best to do in a HVC event?

Sorry if these questions were answered b4 and I overlooked this.

Thanks for a possible reply,

regards

Carsten

I haven't done this yet, but my plan was to set float as low as I could, basically trying to turn off charging. I think the trick is to set bulk and accept first, then you can set float low. Mainsail has this documented on his pbase.com blog/posts. And/or maybe a simple switch on the field wire to really turn off the alternator? Not sure if you could damage something with that or not.

-Scott

[transmitterdan]

The best way is to remove DC power from the regulator. Without power it will then remove the field current thus safely shutting down the alternator voltage. There is no need to set up a strange float voltage. Just use the HV cut circuit of the battery monitor to remove DC from the regulator with a small relay.

[CarstenWL]

... thanks! In the case of the MC-614-H this means just cutting the

2. POWER INPUT - Supplies power to operate the regulator
and deliver field current to excite the alternator.
RED wire included in Ford-style plug.

than I guess?

Carsten

[transmitterdan]

Yes, that should work.

[Anjin]

Originally Posted by CarstenWL

What is the best way to 'deactivate' the alternator/MC-614 when the LiFePO4 battery is fully charged (and I still have to motor) or if I do not want the alternator to charge because I am still at a high percentage of SOC?

What is the best to do in a HVC event?

Carsten, all of the suggestions sound right but are you also charging a starting battery in addition to the lithium "house" battery? If the lithium battery is your only battery then the suggested answers are probably the only right path.

In my installation my two alternators are each tied to the house and to their respective AGM start battery (the house and start batteries are separated by isolators that allow them to charge together but not discharge each other). My plan is when the lithium pack reaches 13.8 volts (measured at the pack) I will disconnect the charging sources from the pack (an HVC event). The start batteries will provide a sink for the alternator current which will protect the alternator diodes; the alternators will simply start to tail off their current flow to the much more limited current acceptance rate of the AGM start batteries.

Please don't take this as gospel; this is all part of my upgrade plan but it is not yet implemented. The batteries are on order as are most of the rest of the components and I hope to have it fully implemented over the next 90 days. It all sounds correct to me and is based on what I've read here, and I believe at least one other user (Rolf "roetter") is doing the same thing. But it's still just hypothetical for me. But it is another option to consider if you are charging that second battery.

- Art

[OceanSeaSpray]

Originally Posted by Anjin

Carsten, all of the suggestions sound right but are you also charging a starting battery in addition to the lithium "house" battery? If the lithium battery is your only battery then the suggested answers are probably the only right path.

In my installation my two alternators are each tied to the house and to their respective AGM start battery (the house and start batteries are separated by isolators that allow them to charge together but not discharge each other). My plan is when the lithium pack reaches 13.8 volts (measured at the pack) I will disconnect the charging sources from the pack (an HVC event). The start batteries will provide a sink for the alternator current which will protect the alternator diodes; the alternators will simply start to tail off their current flow to the much more limited current acceptance rate of the AGM start batteries.

Please don't take this as gospel; this is all part of my upgrade plan but it is not yet implemented. The batteries are on order as are most of the rest of the components and I hope to have it fully implemented over the next 90 days. It all sounds correct to me and is based on what I've read here, and I believe at least one other user (Rolf "roetter") is doing the same thing. But it's still just hypothetical for me. But it is another option to consider if you are charging that second battery.

- Art

What is going to happen if you disconnect at such a low target voltage while charging at fairly high current is that you will never charge your lithium bank properly with the engine (which may or may not matter to you of course). Lithium batteries have an absorption phase just like other batteries.
You would be far better off taking them until they hit at least 14.2V before disconnecting (and they still won't be fully charged). With a significant amount of charging current, a LFP bank can show elevated cell voltages (even 3.6V and over) long before the cells are "full".
If you are not going to absorb, then all considerations about absorption voltage are out the door.

Programming low "float" voltages on regulators effectively turns charging off, because once charged, the voltage on a LFP bank takes time to come back down. "Float" is the wrong term anyway, it is more a holding voltage and it needs to be 13.35V or less (less will cause the battery to start discharging again while the engine is still running). The benefit is that it happens automatically and reliably each time, unlike with a switch (and all other undesirable human-assisted systems).

By the way, someone was asking earlier about the origin of the recommendation of not using cells larger than 200Ah in marine installation. It came back to me directly from the Sinopoly factory in response to technical queries I had made and they were categorical. Their advice was to use 100Ah cells and they said 200Ah was still acceptable, but not preferred. Not enough mechanical strength in the larger cells to withstand motion.
Rolf recently reported two ruined banks that were made from 700Ah Winston units after some passage-making and I would expect the same to happen to 400Ah cells if the vessel was bashed at sea in heavy weather. Don't be a fool and design for the average conditions only or claim that "it won't happen".

[rom]

Originally Posted by OceanSeaSpray

You would be far better off taking them until they hit at least 14.2V before disconnecting (and they still won't be fully charged). With a significant amount of charging current, a LFP bank can show elevated cell voltages (even 3.6V and over) long before the cells are "full"

I thought you experts had a consensus ... so what about that ?
http://www.powerstream.com/lithium-phosphate-charge-voltage.htm

Interesting thoughts on the max. Ah capacity for marine application though. thanks for sharing.

[OceanSeaSpray]

Originally Posted by rom

I thought you experts had a consensus ... so what about that ?
http://www.powerstream.com/lithium-phosphate-charge-voltage.htm

Interesting thoughts on the max. Ah capacity for marine application though. thanks for sharing.

"This" is what happens when you fully absorb at a given voltage, the exact opposite of what was proposed here. It takes about 3.4V/cell only to reach full charge with LFP, but it would take a long time holding at that voltage before it happens: this is absorption.

Without absorption, it is not going to reach full charge, even if you let the voltage rise much more - UNLESS the charge current is low. But this is not what happens with alternators.

I charged 400Ah of new LFPs at 180A with two alternators until they reached 14.4V (all cells at 3.6V). Do you think they were full? We shut an engine down and the current dropped to 90A: the cell voltages were now 3.5V only. We kept charging at 90A until they were back up to 3.6V and it took over 30 minutes. Do you think they were full then? Nope. We cut the revs back and they kept charging at that voltage for some time longer.
We stopped when we were idling and they started showing balance problems and then top-balanced in parallel at low current. Then we got them full.

There is no magic charging voltage. The whole voltage discussion erupted from people who weren't terminating the charge in the first place and thought they could "compensate". It doesn't work that way. There is no correct voltage if you don't terminate the charge. If you do, then the voltage is not that big a deal. It needs to be high enough to charge within a reasonable time, but there is no point stressing the cells either.
One key reason for limiting voltage on our systems is that even minute imbalance issues tend to show way too much and cause grief if and when the battery happens to get near full (often by lack of timely termination) if the maximum voltage is too high.

14.0V is no problem, 14.2V can get a little touchy (especially as cells drift apart a little over time) and 14.4V would be downright cranky, but only after near-full absorption.

LFPs are not lead-acids that can keep bubbling slowly forever at some carefully chosen voltage after being fully charged.

[Anjin]

Originally Posted by OceanSeaSpray

Without absorption, it is not going to reach full charge, even if you let the voltage rise much more.

I'm not really concerned about reaching "full" charge. My experience charging these packs is that when the pack reaches 13.8 volts, assuming cells are reasonably well top balanced, terminating the charge will cause the cells to drop back to around 3.35 or 3.4 volts per cell. At 3.3 volts per cell we are well into the "knee" above which there is no substantive charge - they will continue to accept current and the voltage may climb, but you've already got most of what you're going to get in capacity. See the attachment that shows the discharge curves for my CALB cells. And even if I am missing the top 2-5%, that's ok with me if it means my (rather expensive) cells stay out of the high charging "knee". There aren't a lot of certainties yet with LiFePO4 but there seems to be a growing consensus that cell life gets shortened by spending unnecessary time in that knee.

Originally Posted by OceanSeaSpray

There is no correct voltage if you don't terminate the charge. If you do, then the voltage is not that big a deal. It needs to be high enough to charge within a reasonable time, but there is no point stressing the cells either. One key reason for limiting voltage on our systems is that even minute imbalance issues tend to show way too much and cause grief if and when the battery happens to get near full (often by lack of timely termination) if the maximum voltage is too high.

Agree. That's why all of my charging sources are being programmed to charge just slightly higher than 13.8. When the pack reaches 13.8 it is likely that they will be in constant voltage (i.e. in "absorption") mode - if not I can tweak that figure a bit. But when the pack reaches 13.8, all charging is terminated at the pack and not restarted until the pack reaches some substantial level of discharge. I will refine that number as I gain experience with the CALB CA180fi cells but somewhere between 12.8 and 13.1 seems a good place to start - others have used higher numbers but my instincts from the literature say that a deeper cycle may be healthier.

Thanks for sharing your thoughts!

- Art

[Anjin]

Originally Posted by OceanSeaSpray

By the way, someone was asking earlier about the origin of the recommendation of not using cells larger than 200Ah in marine installation. It came back to me directly from the Sinopoly factory in response to technical queries I had made and they were categorical. Their advice was to use 100Ah cells and they said 200Ah was still acceptable, but not preferred. Not enough mechanical strength in the larger cells to withstand motion.
Rolf recently reported two ruined banks that were made from 700Ah Winston units after some passage-making and I would expect the same to happen to 400Ah cells if the vessel was bashed at sea in heavy weather. Don't be a fool and design for the average conditions only or claim that "it won't happen".

Thanks for clarifying where that recommendation came from. I knew that Rolf had experienced some difficulties but I also know that several GBS banks based on less than 200AH cells also suffered some substantial capacity losses in a few short years. I also know that Maine Sail has had a 400AH cell 4S battery that has suffered virtually no capacity loss in over 5 years use and more than 500 cycles. Not a lot of consistent data to build on.

In my case I made the decision to use CALB 180AH cells for different reasons. They are now and I expect will continue to be more available than larger cells - that means that it's easier to get sequential serial numbers now and will likely be easier to get replacements if I have problems. And if one goes bad it may be harder to find in the pack but it will be cheaper to replace.

But mostly I did it because there appears to be an economic anomaly with LiFePO4: There is no economic benefit of scale - i.e. from using one large cell vs two smaller cells. Unlike flooded lead acid or AGM cells, the price per amp hour remains consistent - or even a little higher for larger cells. I suspect that reflects a difficulty in manufacturing, perhaps a lower yield. In any event, I couldn't justify using the larger cells when I could achieve the same thing with smaller ones at the same or lower cost. Yes, I will have to connect more cells and do it carefully lest those connections become a source of trouble, but that's made up by the small unit weight and size that gives me more ease and flexibility in placement.

"Ya pays yer money and ya takes yer chances."

Cheers -

- Art

[evm1024]

Way back a few pages (post 5057) I made a comment about the voltages on my Winston 700 ah bank being some 60 mV different from the published voltage and that I "should" do some testing. Well, I did do some testing, And here is what I found.

I charged my bank up to what I thought was 100% (but now realize was only about 80% as explained in post 5127). I have not ever run a full capacity test on the bank and generally cycle around 60% to 40%.

Starting the test I charged the bank up until it reached 13.750 volts at around 30 amps. Then letting the bank rest for a day I measured a pack voltage of 13.358 volts. The cells were (3.340, 3.339, 3.338, 3.341)

Then I would run a space heater drawing 100 amps or so for the length of time that it took to drop the bank by 70 AH (as measured on a victron BMV-602s). Then let the bank rest 24 hours measure the voltage again then draw another 70 AH.

0 AH 13.358v (3.340, 3.339, 3.338, 3.341) Assumed 100% SOC
-70 AH 13.257v (3.317, 3.308, 3.310, 3.321)
-140 AH 13.202v (3.302, 3.299, 3.300, 3.301)
-210 AH 13.185v (3.296, 3.295, 3.295, 3.295)
-270 AH 13.152v (3.290 3.284, 3.283, 3.291)
-350 AH 13.036v (3.262, 3.253, 3.254, 3.266)
-420 AH 12.890v (3.226, 3.214, 3.216, 3.232)
-490 AH 12.090v (3.090, 2.937, 2.924, 3.143) Terminate test

Based on post 5127 and on fitting the data above to the open circuit voltage curves I would say that I was only charged up to around 80% and that the curves I've seen fit the published curves closely in the 20% to 60% SOC range with my (used) cells rising faster above 60% SOC.

I did note that the charge voltage did rise significantly at higher charge rates (100 a) as I got to the 80% SOC area. This of course defines the transisition point from CC to CV.

I do not have a power supply that can do more than 30 amps in CV so I was manually adjusting my inverter/charger to mimic a CV charger. I did this with a 3.5v max cell voltage. It there a better cell voltage to use for the CV range? Cell #3 was at 3.475v while cells #1 and #4 were at 3.408v. This was at 30 amps or so.

Regards!