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

[Maine Sail]

Originally Posted by T1 Terry

Google is only your friend when you work out how to sort the wheat from the chaff.
If Winston LYP cells really do have this problem I guess you should contact the manufacturer because they don't seem to have a clue.
Used as house batteries the cells are never likely to subjected to the discharge or charging currents an EV on take off or max regen can demand. Even then, a few mins light load or charging will warm the cell internals sufficient to accept quite solid charging and discharging currents.

T1 Terry

My Winston LYP manual states a charging range of 0/75C on page 15. Use range is to -45C but charging begins at 0C....

[goboatingnow]

Originally Posted by Maine Sail

My Winston LYP manual states a charging range of 0/75C on page 15. Use range is to -45C but charging begins at 0C....

Yes the issue is the electrical conductivity/ ion mobility , at freezing , not the freezing itself. , charging at these low temps causes plating , Li can be charged at sub zero , by using very small ( 0.5%) charge currents. Or by warming the cell of course. ( heat blankets etc , as EV makers do )

Dave

[diugo]

Originally Posted by T1 Terry

If the load is 5C then the same 2.8v limit applies, reduce the load to maintain 2.8v min

Doing so misses the whole point of a constant current drain test---the constant current part. LFPs routinely experience sub 2.8V cell voltages under high load, especially at low SoC. The key phrase here is, under high load. There's a difference between the cell's resting voltage---the one at which damage occurs---and the internal resistance effect on voltage simply measured across its terminals under high current. The paradox is, it's quite hard to estimate resting voltage when a cell is not at rest, which means smart LVDs need to do more than just measure voltage.

The simplistic equation "below 2.8V, the cell dissipates tremendous power equal to I(2.8-V)" might look good at high current---but completely falls on its face at low currents where the real damage occurs without any fanfare whatsoever.

[senormechanico]

Originally Posted by georgec

I was looking for the flexibility of installing the cells on their side and asked Balqon that question just last week. Here is their answer:
"We do not recommend using cells laying on the side for long periods of time due to safety and reliability reasons."

HiPower says any orientation other than upside down is ok.
My boat's HiPower cells are mounted on the narrow edge, i.e. sideways.
2 years and no problems.

My home's Winstons are "right side up".

[diugo]

It turns out that there is a right way and wrong way for laying a Winston (aka Thunder Sky) cell on its side:

For more info see: http://forums.aeva.asn.au/forums/lfp...topic3854.html

[dlentz]

Originally Posted by goboatingnow

At the end of the day Li technology is the same across all Li -ion variants

Dave

Google your friend may not be telling you the "whole story" here. Try googling "Why Winston switched to the LYP (yttrium)". You might find it had to do with better temperature performance. Was it just for the upper end? Or could their specs be correct?

PS: Moot point for me, if my batteries are below 0C, I'm looking for a plane to get where it's warm!

[sabray]

I am technically deficient and trying to catch up. For a grand I can stuff in some freedom lifelines. They will last 8 years if they are like my first set.
For a bunch more bucks that I haven't considered I could go lithium.
New technology. Requires that my charge system is replaced. So I'm looking at new controllers and a separate battery monitor/safety with relays contractors , led lights etc.... .
I will get more usable energy. Can charge even faster but need to upgrade to higher charge equipment. The suppliers are on cutting edge and may not be consistent in what they have supply and support. Great for people playing around but not really accessible for the low budget need reliable gear guys .
Is there a cheaters guide to installing this next gen battery?

[roetter]

Originally Posted by T1 Terry

(1) Best not to mount them upside down, it makes it very had to do the terminal bolts up, apart from that there is no restrictions... as long as you can protect the exposed terminals from anything conductive touching across them, not a good look when that happens and a change of clothing is required (2) If you do not use some form of solid plating across the larger faces of the end cells and compress them together you will loose capacity as the cells will bulge. Has nothing to do with the rate you discharge or charge them, it is all to do with the cell voltage at any given time. Exceed the magic 2.8v and 3.4v limits for any period of time and the electrolyte will start to boil off the lighter vapours. Just like the coolant in the car, the higher the pressure with in the cooling system the higher the temp before vapour is released. Banding the cells with solid end plates stops the case from expanding and allowing the pressure to remain low. Even on the shelf cells in warm climate will start to bulge the cases just sitting there, that is why they are so well packaged in the boxes when they come from the factory. If your cells have bulged, don't panic, in a warm environment simply use the solid end plates, 3mm aluminium will do, a using a "G" clamp or sash clamp, compress the pack back together, then strap it or make a battery box that the ends can be mechanically pressed against the cells larger face, the other end solid enough not to bulge under the pressure, and squeeze them up till all the cells sit flush with one another. (3) If at all possible, use multiple cells in parallel to build capacity, connect these is series to build voltage. Only one 12v battery for a 12v system, far too hard to control cell balances between multiple 12v Li batteries in parallel, it makes herding cats look like child’s play. T1 Terry

Balwinder Samran from Balqon told me that banding is not required to prevent bulging under normal conditions. He said when the pressure builds due to some fault than there is no holding them even with banding. I was going to order banding for time 8 700ah cells. So he questioned how I would be lifting them. I told him I thought banding was required,for long life. He said it is not required.

[goboatingnow]

Originally Posted by dlentz

Google your friend may not be telling you the "whole story" here. Try googling "Why Winston switched to the LYP (yttrium)". You might find it had to do with better temperature performance. Was it just for the upper end? Or could their specs be correct?

PS: Moot point for me, if my batteries are below 0C, I'm looking for a plane to get where it's warm!

Winston switched to Lyp to sidestep a patent issue.

All Li the is the same basic processes , with the same basic advantages and disadvantage. It's already been established that the battery manual for Winston is consistent that batteries can't be recharged at or below zero , no basic Li cell can be.

Dave

[boatpoker]

Mainesail ... as I said I have a long way to go to understand this technology but I am trying. I had a tour of Metalcraft last week with a bunch of other SAMS surveyors. Metalcraft are very much into lithium batteries of all types and have an electrical engineer on staff who seems very much up to speed. When told of several people on this forum (who also seem to know what they are talking about) advocating against BMS they could not think of any installation in which they would agree. Can you summarize the main points against using a BMS.

[Maine Sail]

Originally Posted by boatpoker

Mainesail ... as I said I have a long way to go to understand this technology but I am trying. I had a tour of Metalcraft last week with a bunch of other SAMS surveyors. Metalcraft are very much into lithium batteries of all types and have an electrical engineer on staff who seems very much up to speed. When told of several people on this forum (who also seem to know what they are talking about) advocating against BMS they could not think of any installation in which they would agree. Can you summarize the main points against using a BMS.

I personally advocate for a BMS using it for over voltage protection and over discharge protection. I am not convinced you need a BMS for cell balancing provided you keep the bank above the low floor and don't push charge voltages above approx 14.0V... To me a BMS used for LVE & HVE is an inexpensive insurance policy for a very expensive bank.

[boatpoker]

Mainesail , Thanks for your response.
ABYC is currently working on a standard for these batteries and their installation but in the meantime can you think of any particular aspect that should be reported on as part of a pre-purchase survey that is not covered by E-10.

[Maine Sail]

Originally Posted by boatpoker

Mainesail , Thanks for your response.
ABYC is currently working on a standard for these batteries and their installation but in the meantime can you think of any particular aspect that should be reported on as part of a pre-purchase survey that is not covered by E-10.

Yes I am involved in those discussions but I can assure you they are moving at a snails pace and will likely start out life as a technical advisory before becoming a standard..

[boatpoker]

Originally Posted by Maine Sail

Yes I am involved in those discussions but I can assure you they are moving at a snails pace and will likely start out life as a technical advisory before becoming a standard..

Thanks Rod, does your reponse mean you can't think of anything in addition to E-10 that I should be looking at ?

[Maine Sail]

Originally Posted by boatpoker

Thanks Rod, does your reponse mean you can't think of anything in addition to E-10 that I should be looking at ?

Use E-10 as a guide + OCP (Class-T), hold downs, battery cover to prevent shorts etc.. The problem is I have no idea where anything will land yet so hate to give advice that may not be accurate. Use E-10/E-11 as a guide because that is the only thing we have at this point.....

I know Charlie J. is also involved so perhaps he knows something I don't...