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

[Jd1]

Originally Posted by campr

Jd1,
using a contactor, rather than a relay in combination with the cellog8. Once it triggers, manual action is required to flip the contactor back to normal operation. I would not want it to automatically switch everything on again. I am using two cell-logs. One for the consumers, and one for the generators. If a cell-imbalence is detected, both will trigger. I have one set up for HVC and one for LVC connected to the generators/consumers respectively.

The issue is what the Cellog is used for. In your case you use the Cellog to monitor for a danger situation but in my case I would attempt to use it for complete control. In other words, the charge relay for example is de-activated when the battery is full as part of the normal charge cycle. I would have a secondary Cellog with higher HVC and lower LVC to do protection service (that has to be manually cleared) for a fault condition. Normal HVC and LVC would not be considered a 'fault' but rather a normal operational response.

[OneTwoSail]

Originally Posted by NahanniV

Campr,

I would be interested to know what contactor you are using, also the details of how you have it connected to the CellLog.

Thanks,
JM.

Be careful of leaving the cellog's connected to the pack full time. They have a very uneven draw of power from the cells. I'm not sure how much difference you'd see in the short term on a large pack, but I saw a noticeable change on my bicycle's 20AH pack over a few days.

[Maine Sail]

Originally Posted by patrickza

Be careful of leaving the cellog's connected to the pack full time. They have a very uneven draw of power from the cells. I'm not sure how much difference you'd see in the short term on a large pack, but I saw a noticeable change on my bicycle's 20AH pack over a few days.

This is only an issue on packs of more than 5 cells. Been discussed here... A 12V bank will be a max of 4 cells to monitor.

That said I am not a fan of the Cell Log 8 (I own tow of them) but do consider it a good toy for monitoring voltage visually.... I would not persoanlly use one to control anything on my bank other than perhaps an audible alarm that is already backed up by something else.. Just my .02...

[NahanniV]

Originally Posted by patrickza

Be careful of leaving the cellog's connected to the pack full time. They have a very uneven draw of power from the cells. I'm not sure how much difference you'd see in the short term on a large pack, but I saw a noticeable change on my bicycle's 20AH pack over a few days.

Ii am not seeing this on my 400AH cells. It's a 12v pack, so 4 cells in series. The CellLog has been connected continually for over a year. It has not caused any imbalance; I only ever balanced the cells once when I first got them.

My understanding is that cells 7 & 8 are not used to power the device, so not a problem with a 4 cell string.

Is your pack 24V ? Which Cells are discharged ?

Cheers,
JM.

[campr]

I am in no way endorsing these suppliers or products, but it's what I'm using.

How to wire it up to a celllog 8:
lithium & solar power LiFePO4, The alarm output for CellLog One of the Cell...

The contactors:
EV-Power | DC Contactors

I am using 5 contactors for the generation side (4 panels and the field coil in my alternator)

I am using 2 contactors for the consumption side, 600A for the inverters (2x 3000W watts) and one for the rest of the electrics on the boat (200A)

Why 2x3000W? I am hoping to get a dive-tank compressor and am using electricity (induction) to cook.

[campr]

There is an article on 'fixing' the cellog8 here:
Endless-sphere.com • View topic - CellLog 8 hacking

Along with a diagram of how it works (measures).

[roetter]

JD1 - that's why I am using the Lightobject programmable voltmeter. It has programmable hysteresis settings for high and low alarms. I use the Junsi only to visually check up on any cell drift.


Rolf

[Jd1]

Originally Posted by roetter

JD1 - that's why I am using the Lightobject programmable voltmeter. It has programmable hysteresis settings for high and low alarms. I use the Junsi only to visually check up on any cell drift.
Rolf

Yes, that makes sense. I will be using the Cellog (Junsi) the same way now. I placed an order for the House Power BMS as it covers both cell imbalance as well as the pack voltage. Are you using anything to automatically monitor the cell voltages with or are you doing this manually? I would imagine that manual operation should be ok since nobody seems to experience cell drift but I don't have the balls to bet my battery pack on me remembering to check the Cellog.

[roetter]

On my mono (short trips only) I used to have the Junsi hooked up but do not bother now. I just measure once in a while ( every month) with a multi meter. I probably bring the Junsi to the boat again and record a few cycles for fun.


Rolf

[Jd1]

It has likely been mentioned but searching this thread is a monumental task .... so forgive me for asking this again:
What do you use for corrosion protection on the cell inter connecting strips? The Balqon strips are 4 layers of pure copper with no tinning and I would rather keep that shiny and not with a funky green patina on the interconnections.

[CharlieJ]

Buff the terminals with a ScotchBrite pad, apply NoOx, torque the fastener, spray the exposed inter-connects with Boeshield T9.

[Jd1]

Originally Posted by CharlieJ

Buff the terminals with a ScotchBrite pad, apply NoOx, torque the fastener, spray the exposed inter-connects with Boeshield T9.

Thanks Charlie! What kind of store carries NoOx - would Home Depot / Rona have that or is it something only the electrical wholesale places have ?

[ColdEH]

Originally Posted by Jd1

It has likely been mentioned but searching this thread is a monumental task .... so forgive me for asking this again:
What do you use for corrosion protection on the cell inter connecting strips? The Balqon strips are 4 layers of pure copper with no tinning and I would rather keep that shiny and not with a funky green patina on the interconnections.

I actually bought a set of these .

EV Works Braided Cell Interconnector 55-12 55mm nominal pitch, 12mm holes

They are tinned and don't stress the terminals if there is any expansion or shifting. Got them from Australia and didn't take long at all.

Regards

[hellosailor]

In the States we call those "tinned ground straps". They are sold in auto stores, typically in longer lengths, and the material itself can also be bought by the roll. It is sometimes flat ribbon, sometimes actually tubular so it can be used as an RFI shield as well. Crimping on end terminals, or fashioning them, is left to the buyer when you buy it by the roll.

The advantage is that they easily adjust to any length between two posts, and with "known" spacing on battery terminals they're probably just a needless expense compared to copper slugs, for most people.

[Jd1]

I am gradually making progress with my lithium install. The batteries are in the boat and set up for initial testing. I have set up the House Power BMS and the little cell boards. Yesterday I finished a top balancing. When I left, all four cells were in shunting mode indicating they were above 3.65V but below 3.8V. This morning I was expecting to see all batteries around 3.65 or so volts.
Instead, I have the following result:
3.596V
3.576V
3.599V
and
3.383V !!!!!
The first three cells are in the range I was expecting but what is going on with cell #4?
This is not the first time that cell #4 behaved odd - it was doing a similar thing while I was in the process of balancing but I wanted to verify this behaviour after balancing - which I now have.
I am unable to do a full load test at this time as I am still waiting for my order of battery cables to come in.
Another bit of trivia - the cell that is acting up has marks on the case left by allthread rod as if it was previously installed. I was assured by Balqon that the cells are all new but that some cells out of every batch are tested and the marks might be from that. IMHO the marks are wayy too deep for that unless the have some gorilla of a guy strapping them into the test setup ... but that is only my opinion.
Question: Is the behaviour I am seeing an indication of battery age or previous use or should I ignore this issue until I have my cabling set up for a full capacity test ?
Has anyone else run into this kind of issue ?
I will be doing a full capacity test one way or another but I am getting concerned and wanted to see if other people have run into this kind of behaviour.

Thanks