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

[ColdEH]

Just pulled them out of the box , there are barcode stickers on them but no date code . They are banded , may be on the sides.

Regards

[ColdEH]

Here's a question, how long can I leave them in the box without a charge? I may not get them in the boat for another 6 months , in the spring .

Regards

[deckofficer]

At 3.29 volts, should be good for those 6 months. I'd check cell voltage once a month though.

[Lagoon4us]

Originally Posted by deckofficer

Lagoon4us, I'm glad you got new stock, nicely balanced cells. That does make them plug and play. If you remember a year back on this thread I wasn't so lucky, getting 3 year old cells. They are tight now though.

Indeed i do, yes mine are consecutive build numbers and they were date stamped 5 weeks prior to purchase flown out via Aeroflot as they don't fuss about energy devices etc....
The Chinese said they are all computer charged and ready to use, i connected them then left them for a week to normalise, there was no voltage difference to 3 decimal points.
Today they may go to within 9/1000th of a volt when charging, no issues at all.
Cheers Frank

[deckofficer]

Old stock or new stock, once balanced they are amazing batteries. I've never had a battery that doesn't sag under heavy load or capacity de-rated.

Lead is dead.

[Lagoon4us]

Strongly recommend unbolting the cells connections and polishing the connections every 3 months or so, it's copper on ally with SS bolts, 'not a great mix'!!!!

A light sand and bolt back together can't hurt.

Cheers

[ColdEH]

Originally Posted by Lagoon4us

Strongly recommend unbolting the cells connections and polishing the connections every 3 months or so, it's copper on ally with SS bolts, 'not a great mix'!!!!

A light sand and bolt back together can't hurt.

Cheers

Thanks for the good advice , but they are not connected together as yet , they are just strapped together. I will remember that when I get them installed.

Regards

[T1 Terry]

Hunt down a product called Alminox so you have it ready for when connect the cell links. Use one of those plastic pot scrubber material buffing disks on a drill and polish off the oxidised material on each post till it's shiny, los of Alminox, make sure the link plate is also clean, then bolt them up. You should not need to do it again in under 12 mths but more likely 2yrs or more if you applied plenty of Alminox.

As far as storing the cells, I agree with Frank, leave the links off till you are ready to use the cells. They will sit at 3.2? volts for 3yrs or more. Do not discharge the cells before you fully charge them and do not use them before you have fully charged them, it will shorten their cycle life if you do.
Are you planning to build 2 x 300Ah 12v batteries for seperate applications or one 600Ah battery? Don't try to build 2 x 300Ah batteries and link them in parallel, that will end in tears and a damage wallet.

T1 Terry

[ColdEH]

Actually I was hoping to build up one big 12 volt back of 600 Ah. That was my plan from the get go , I could have got 4 bigger cells to make one bank but if I lost one cell I would lose all of it so I broke it up .

What should I do , I really want one bank of 600Ah. ???

Regards

[deckofficer]

I don't like series/parallel for any battery chemistry. At 12 volts even if all I need is around 400 a-hr, I've used L16 two in series. I also don't like to have any single battery heavier than I can move by myself, and at 125 lbs those L16s were too heavy so before we had LiFePO4 I used 2 volt cells both flooded and AGM for the desired capacity. If you wanted 600 a-hr, then you should have saved some money and used the Winston 700 a-hr cells at $565 that were on sale at Balqon. In your case with the (8) 300 a-hr cells, I would just make two separate 300 a-hr 12 volts banks and use a battery selector switch and don't use the "both" position. Voltage sag is so minimal on these cells, it won't make a difference.

[ColdEH]

What happens if I put the two banks in parallel. Would I damage one of the banks ?

Regards

[goboatingnow]

I don't see the issue of parallel and series banks to get 660 Ah. I mean if you cell monitor its the same issues as any series set.

I would reccomend the bigger bank as a general rule , all Li 12v configure are series / parallel sets anyway

dave

[ColdEH]

The bigger bank would be much easier for me to charge and monitor and much less switching .

Regards

[T1 Terry]

All Li prismatic cells are parallel connected to build capacity, the connections are simply out of view inside the plastic case. You are far better off building capacity by paralleling cells and then voltage by linking these groups together. With a single 600Ah cell you can't clean a dirty parallel contact, you can't mix and match cells that charge faster with cells that charge slower, the more cells you have in parallel the closer they will stay in balance. I have 8 x 90Ah cells in parallel with 4 sets in series, this builds a 720Ah bank, I even went as far as separating each set of 8 in parallel by building 4 cells in each group and linking with a cable, just to see if I could create an issue with the pack going out of balance. We are now at 27 mths cycling every day, 200Ah plus out over night and rely on solar only to recharge, a few times down to 2.8v per cell, one or two times even lower than that, they are still within an acceptable balance at the end of charge, 3.45 to 3.50v, yet some members of our motorhome group with single large capacity cells regularly need to rebalance, well 3 mthly or so anyway.
Using a cell logger and recording a long graph, say a week at 30 sec sampling, will tell you if you have any issues with cell connections, the problem parallel group will read high when charging and low under load, you can fix it if the connections are outside, you can't if they are in the plastic case.

T1 Terry

[Cotemar]

This LiFePO4 Batteries thread is 195 pages with 2924 posts.

Would it be better and easier to get specific information if we started using LiFePO4 categories?

LiFePO4 Batteries
1) LiFePO4 battery abbreviations & definitions
2) Where to buy LiFePO4 batteries
3) Connecting LiFePO4 batteries, series & parallel
4) Balancing LiFePO4 batteries
5) Testing LiFePO4 batteries
6) Battery management systems (BMS) for LiFePO4 batteries
7) Using LiFePO4 as a house bank
8) LiFePO4 Battery Chargers
9) Shore charging LiFePO4 batteries
10) Alternator charging LiFePO4 batteries
11) Solar charging LiFePO4 batteries
12) LiFePO4 Low & High voltage shut off
13) Managing LiFePO4 house bank & Lead acid start battery