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

[gscriba]

Looking at these as a possibility for my "new to me" Tayana 52. Thoughts?
Balqon Electric Vehicle Manufacturer

[44'cruisingcat]

Originally Posted by OceanPlanet

I don't know of any marine Li installations that are 10yrs old. However I know Genasun has an 1800Ah x 24V system on a Gunboat 90 cat that I think is about 6yrs old. Last year they started getting pesky HV alarm/cutoffs, and they contacted us. A couple calls and a BMS log file later, a cell board module turn out to be corroded (that pack was by a vent that was bringing in wet air). Sent a new board, boat captain installed it, and all good to go.

Thanks for the feedback.

[exMaggieDrum]

Originally Posted by gscriba

Looking at these as a possibility for my "new to me" Tayana 52. Thoughts?
Balqon Electric Vehicle Manufacturer

I've been looking at this website for weeks now. Sent them an email. Found others who tried to contact them a couple of years ago - no response. Their stock (BLQN) is still listed but it is a penny stock and no activity on it. It seems to me they are defunct. If you manage to contact them let us know.

In any case the product is way too high for the spots I have.

[exMaggieDrum]

Originally Posted by CarstenWL

I can not see how this can be the best option. If I look at Winston cells (I have 4x400Ah) the price for 4x400Ah is slightly lower than 16x 100Ah. Than think about cell connectors, Cell monitoring, ... for 16 cells.
Carsten

Thanks for you thoughts Carsten. I did consider that and I totally understand the extra connections, cell monitoring, wiring, etc. for 16 cells. I would not have considered that at all initially but after I saw the installation on Entropy (see posts) and his reasoning for it, it started to make more sense to me. And it will fit in the space of one 8D plus a little longer (1.4"). Height is the same and the width is slightly less.

The 400Ah, and the 200Ah and the 130Ah cells are all too big. I'd rather combine the 16 cells than rebuild a location for the batteries. Believe me, I like KISS.

Amazing the amount of power that can be stored in the space.

[exMaggieDrum]

Originally Posted by mbartosch

In my own installation I finally chose 16 * 100 Ah instead of the 200 or 400 Ah cells. IIRC the price difference to the larger cells was not significant (that was about 9 months ago)

This is S/V Entropy. I should have used his CF name.

[senormechanico]

Originally Posted by OceanSeaSpray

Maybe it was wrong. I was talking to a guy who had just fried his boat electrical system using a Mickey Mouse BMS combined with issues in this area just recently.
The BMS dropped the bank and it left the charging system directly connected to the loads on board. Voltage spike out of the MPPT as the battery disappeared and then solar voltage for everyone.

That could happen on a lot of installations I have seen diagrams for by the way.

Keep your engine battery and it can be quite small. It is a completely independent power source to start the motor and redundancy is the reason for having it.

Short of seeing a diagram of what you have/want to do, it seems a bit problematic to take this further.

I don't like battery switches on dual bus lithium systems. Opening both the load and charge bus contactors effectively performs a disconnect. Also I like to see the alternator output tied to a battery, not to a switch, and I like to split the alternator output with blocking diodes. No combiner switches, VSRs etc.

Eric

The above problems are exactly why I have ONE bank (200 Ah) and a BMS but with no disconnects. (I am working on an alternator disconnect but there are more important things on my plate at the time)
I have had lifepo4's for several years and have had no problems at all.
I just keep a general eye on max, min voltages on my BlueSky IPN solar controller.

Just for testing, I've run the bank down to 20% and started the engine on them. Like I said, this is the only bank on the boat. I could not tell any difference in cranking speed. Engine started as if they were full.
Don't worry, be happy. (Where have I heard that before?)

[senormechanico]

Originally Posted by gscriba

Looking at these as a possibility for my "new to me" Tayana 52. Thoughts?
Balqon Electric Vehicle Manufacturer

There are some very interesting changes in the charge/discharge numbers from previous lifepo4 listings.

http://www.balqon.com/wp-content/upl...GUIDE-2015.pdf

Specifically, no more 3C charge/discharge. It's now 1C.
I've never exceeded that anyway, but it's interesting.

Next, the charge numbers.
13.8 bulk/14.3 abosorb, 13.5 float.
I don't remember exactly, but those WERE NOT the numbers.
I've used 13.8 bulk and 13.4 float for a long time with no problems.
At first, I charged them to 14.2 but could not see any benefit.

I've had these lifepo4's for several years and imho they're still like new.

BTW, I have a neighbor who purchased a 700 aH 48 volt backup bank for his house's 72 solar panel grid tie.
He never got any documentation with the 4 foot by 4 foot by 4 foot bank in a big grey metal box.
It works, but the BMS is a nightmare.
Balqon has not answered any of his emails asking for documentation and / or instructions.
His professionally installed grid tie works, but doesn't play nice with the backup bank.
He's constantly messing with balancing while mine just sits there fat and happy.

I'm really glad I did my own backup system's design. Balqon 700/24 volt battery, but the rest of the system is mine.

[44'cruisingcat]

Originally Posted by senormechanico

............................
I've had these lifepo4's for several years and imho they're still like new.
.......................
.

When did you install them, and what's your useage? ie, do you live aboard full-time etc.?

I'm very interested to read about people's long term experiences with LiFEPO4.

[tsmwebb]

Originally Posted by mbartosch

BTW, cell monitoring is identical regardless how many you arrange in parallel.

I recently looked at a failed 8s9p li-nmc battery. One cell went bad and the BMS didn't notice it until the whole bank it was in was problematic. By that point the bad cell had gotten very hot. Temperature monitoring was via a thermistor a couple banks away in the battery and it didn't trip an alarm. I suspect the voltage alarms and balancing feature we defeated / delayed by the strength of the other cells in the bank. Is the monitoring of each cell less exact with more parallel cells in a bank?

[mcarling]

Originally Posted by exMaggieDrum

In any case the product is way too high for the spots I have.

What are the dimensions of your space?

[OceanSeaSpray]

Originally Posted by tsmwebb

I recently looked at a failed 8s9p li-nmc battery. One cell went bad and the BMS didn't notice it until the whole bank it was in was problematic. By that point the bad cell had gotten very hot. Temperature monitoring was via a thermistor a couple banks away in the battery and it didn't trip an alarm. I suspect the voltage alarms and balancing feature we defeated / delayed by the strength of the other cells in the bank. Is the monitoring of each cell less exact with more parallel cells in a bank?

Yes. Of course. You only have one voltage for each whole parallel group and you can't see the currents flowing between cells. If one goes bad, it can start sinking large amounts of energy and heating up before the voltage difference gets very noticeable.
You can fuse each cell etc like in automotive packs, but it is not always that easy to size these fuses.
Having a few thermistors scattered in a pack is not good enough. Temperature can be the only early warning you get in large parallel configurations. Any differences developing between sensor readings should be a real concern, even if it is not "hot".

More commonly, a bad cell causes much more moderate discharge and the first warning you get is a balance problem when recharging. Cell voltages and temperatures are important.

The DNV-GL guidelines for large marine battery banks state:

"Temperature sensors must be placed in such a way that temperature differences between any cells exceeding 5°C for more than 5 minutes are detected".

[OceanSeaSpray]

Originally Posted by senormechanico

The above problems are exactly why I have ONE bank (200 Ah) and a BMS but with no disconnects. (I am working on an alternator disconnect but there are more important things on my plate at the time)
I have had lifepo4's for several years and have had no problems at all.
I just keep a general eye on max, min voltages on my BlueSky IPN solar controller.

Just for testing, I've run the bank down to 20% and started the engine on them. Like I said, this is the only bank on the boat. I could not tell any difference in cranking speed. Engine started as if they were full.
Don't worry, be happy. (Where have I heard that before?)

Well, having no disconnects just means having no protection, so... In the end it is not that hard to disconnect properly, it just takes two distinct disconnects, not one. Boats are not EVs: they get used while charging and this means that the engineering has to be different.

Having had "no problems" just means nothing. I haven't had any problems either. Is it enough to suggest that nothing can happen? It just means nothing has happened so far. And things sometimes happen.
Same old story, knock something up together for your own use, take whatever risks and maybe face the consequences. Start building stuff for people or advise them, different story.

Of course it will crank at low SOC. So what?

Split the alternator output to also charge the cranking battery (not very well, but it will bulk charge if ever needed) and add a small solar source or a DC/DC boost charger to top it up. It can spend its whole life happy and fully charged and there is redundancy in the system. It is not hard. And you don't get voltage sag and transients in the boat electrical system each time with cranking.

[exMaggieDrum]

Originally Posted by mcarling

What are the dimensions of your space?

I have 3 8D's (Lifeline). Two are in a difficult spot to get to and the custom welded mounting frame is almost exactly the same footprint as the batteries. They are at different orientations (one 90 degrees to the other). There is NO extra headroom. I don't really want to have batteries here at all.

The other 8D is under the Nav seat and is easier to get to and has more room. There are about 3" extra room in the length and several in the width. About an inch more headroom than the battery.

A Lifeline 8D is 8.6H x 11W x 21L inches. So I have room for about 9H x 14W x 23L.

Winston and CALB 100Ah cells in a 4p4s configuration (like mbar..... has) are 8.7H x 10.6W x 22.4L. So almost the same for H. W is 0.4 less. L is 1.4 more. Excluding a frame to bind the cells. So I need space on at least two opposite sides for frame hardware, and I need room for cables to the battery.

Sinoply cells are "skinnier" in the 4p4s configuration by 1.4" and still 1.4" longer than the 8D. Not sure of the reason why the Sinoplys are narrower than the Winstons which means their exterior volume is less for the same Ah's.

I really want to fit the battery in this spot if at all possible. Cooler, dry, easy access, room for fuses and buses. It will be tight with the fuses and all but doable with some creativity.

I'd still like to get some feedback from anyone who has Sinoply cells in use, the longer the better. The prices for 200Ah cells is somewhat better than for 100Ah cells but I just don't have the spot for them, and especially not for a 400Ah cells. They are too tall and the 400Ah are too tall and too long.

Any ideas are welcome.

[exMaggieDrum]

Originally Posted by OceanSeaSpray

Yes. Of course. You only have one voltage for each whole parallel group and you can't see the currents flowing between cells. If one goes bad, it can start sinking large amounts of energy and heating up before the voltage difference gets very noticeable.
You can fuse each cell etc like in automotive packs, but it is not always that easy to size these fuses.
Having a few thermistors scattered in a pack is not good enough. Temperature can be the only early warning you get in large parallel configurations. Any differences developing between sensor readings should be a real concern, even if it is not "hot".

More commonly, a bad cell causes much more moderate discharge and the first warning you get is a balance problem when recharging. Cell voltages and temperatures are important.

The DNV-GL guidelines for large marine battery banks state:

"Temperature sensors must be placed in such a way that temperature differences between any cells exceeding 5°C for more than 5 minutes are detected".

Would this imply the need for a temp sensor for each cell, e.g. 16 for a 4p4s configuration? Is there any other way to monitor the temp differences between cells otherwise?

[exMaggieDrum]

I'll ask simply and point blank: Is there any direct knowledge by anyone that Balqon Corp is still in business? Their website does not give a phone number nor an email address, only a contact form. I sent them the contact form and I have not received a reply two weeks later.