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

[transmitterdan]

Originally Posted by goboatingnow

A note , if your using a lab power supply, check that it has over voltage protection. Most don't like being connected to batteries otherwise


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Charging a single LiFePo cell with a bench supply will usually be ok. However, some cheap power supplies do not have protection for charging high voltage series connected batteries. If the OVP utilizes a crowbar SCR it can be seriously damaged from the huge current the battery can supply.

There are design differences between battery chargers and bench supplies. The manual for the bench supply should be consulted before using it to charge battery banks.

[OceanSeaSpray]

Originally Posted by matureee

...
I am considering building myself a cell top balancer, this will bring one cell at a time up to a known state of charge. The known state of charge is defined as a fixed voltage somewhere on the steep dv/dSOC curve (upper knee) at a fixed charging current.

It will consist of a 5V wall wart capable of supplying 5-10A a constant current source a voltage sensor and a latching relay. Plug it in and led1 comes on (rule one in electronic engineering:- it does not matter what it does make sure it has plenty of pretty flashing lights) connect it to the cell and led2 comes on press the button which engages the relay and a constant current is fed to the cell (led3) when the cell voltage hits (insert favourite number here) V the relay disconnects and led 4 comes on and a buzzer sounds. Repeat with all cells. All in this is about $10 worth of electronics and is much easier to lose somewhere on my boat than a lab power supply.

Why one cell at a time?. When cells are paralleled we have no control over the current into individual cells the approach has been to hold the voltage until the current drops to close to zero then we know the current in each cell. I believe that holding a high voltage on these cells is detrimental to their health and want to minimize this.

This seems too easy have I missed any snags with this?.

It is not a bad idea and I do more or less this for the very reason you highlight and I usually use solar panels as power source. There are a few flaws in your reasoning, first of all constant current is senseless and you don't need to hold a high voltage on the cells no matter what.

All you need to do is feed current, any current, to the cells and limit the maximum cell voltage allowed. Charging one cell or multiple cells in parallel makes no difference either as long as you eventually charge them up into the upper knee where they can equalise.
If you just switch on and off (and you don't need an expensive latching relay for that), charge them until they hit 3.6V (and that will be very brief) and then recharge again if they drop below 3.5V at rest, and repeat until they eventually hold at 3.5V or more at rest. They are very close to full then. By the way, this switching regime is what Terry was proposing a while ago already.

Alternatively, use a voltage-regulated source limited to anything between 3.45 and 3.55V and disconnect once the current has tapered down to near zero. They will be fully absorbed. You don't need high voltages at all to charge them to 100% SOC, you can trade voltage for a little more time and it is easier on the cells.

The challenge for you could be finding that low voltage power source that won't overload and trip when you connect it to a load that is holding the voltage down to 3.3V for hours or days. This is why I use solar panels and then the whole process can be done on board.
I use the same electronics for initial balancing that I later use for bank protection, just connected differently.

[goboatingnow]

Just to avoid nomenclature errors Li is charged firstly by CC then by CV. The CC s because typically the charger cannot supply enough power fast enough so it's must be designed to limit.

Dave


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[Ex-Calif]

I periodically jump in here to see the latest conversations.

It would be nice to have a (separate) thread with - Here is my "fully" installed and operational system and here is how it is performing for me.

This thread is great (vitally important?) for the science and the experimentation but the "after" pioneers really want a bill of materials and some setup instructions.

I know it is in here but it's like extracting pepper from fly sh!t.

Maybe some of you that are done could do that. "Sample LiFeP04 Setups"


Carry on men...

[GoingWalkabout]

Originally Posted by Ex-Calif

I periodically jump in here to see the latest conversations.

It would be nice to have a (separate) thread with - Here is my "fully" installed and operational system and here is how it is performing for me.

This thread is great (vitally important?) for the science and the experimentation but the "after" pioneers really want a bill of materials and some setup instructions.

I know it is in here but it's like extracting pepper from fly sh!t.

Maybe some of you that are done could do that. "Sample LiFeP04 Setups"


Carry on men...

[qwerty_steve]

Originally Posted by Ex-Calif

I periodically jump in here to see the latest conversations.

It would be nice to have a (separate) thread with - Here is my "fully" installed and operational system and here is how it is performing for me.

This thread is great (vitally important?) for the science and the experimentation but the "after" pioneers really want a bill of materials and some setup instructions.

I know it is in here but it's like extracting pepper from fly sh!t.

Maybe some of you that are done could do that. "Sample LiFeP04 Setups"


Carry on men...

I'm almost at the point of diving in, I found Maine Sail's guide to be very informative:

LiFePO4 Batteries - Thoughts & Musings Photo Gallery by Compass Marine How To at pbase.com

If you're prepared to do your homework you can do this yourself, if not probably best to get an expert on board.

[hellosailor]

"I know it is in here but it's like extracting pepper from fly sh!t."

You mean, there are objective, repeatable, widely agreed upon standards for setting up and charging a lithium (presumably LiFePO4) battery, that will ensure optimum charging life?

Including what % SOC the battery can be cycled through, min to max, that will produce optimum total battery life?

Or, why some folks say that the batteries don't lose capacity simply by aging, while other folks say they've seen significant drops? ({Presumably, that charging and cycling factor being another invisible cause.)

I'm reminded more of Schrodinger's Pony. You know, like the cat in the box that might be dead, might be alive? Except with the cat, you don't have to dig through a whole pile of * just to find out whether there's any pony in it.

[T1 Terry]

Originally Posted by hellosailor

"I know it is in here but it's like extracting pepper from fly sh!t."

You mean, there are objective, repeatable, widely agreed upon standards for setting up and charging a lithium (presumably LiFePO4) battery, that will ensure optimum charging life?

Including what % SOC the battery can be cycled through, min to max, that will produce optimum total battery life?

Or, why some folks say that the batteries don't lose capacity simply by aging, while other folks say they've seen significant drops? ({Presumably, that charging and cycling factor being another invisible cause.)

I'm reminded more of Schrodinger's Pony. You know, like the cat in the box that might be dead, might be alive? Except with the cat, you don't have to dig through a whole pile of * just to find out whether there's any pony in it.

Love it :lol: A bit of humour never goes astray. There will always a gulf between those that do hands on testing and those that just read about it and then try to type themselves smart... love that saying of Jack Rickard's There is no value in trying to adapt knowledge from electric vehicle use or tests on little cylindrical cells and apply it to house batteries, same cells but the use pattern is worlds apart.

T1 Terry

[CynthiaP]

I am a Cruiser using LiMgFePO4 ( Valence ) batteries that were installed by Maz Ocean for my house and engines. This has acually changed the way we live on the boat and our actual energy management. We have found it is easier to live on the boat. We have a Catamaran and each engine has its own 40 Ah battery. the house Bank is 880Ah 12V. The change of Batteries from lead acid:

1) Loss of 240 Lbs.
2) Faster charging due to no or little Float
3) 80 - 95 percent Discharge giving me 800Ah available
4) In the same space as 6 (110Ah) lead acid I was able to put 8 (110Ah LiFePO4)
5) Very important each battery has its own fuse. Nigel Calder States "Each Lead acid battery and should be fused" which is not common on most if not all boats.
6) Consistant voltage for my electronics
7) Ability to leave the boat without hooking up to shore power and leave the frig and Freezer on.
8) I was replacing my old Lead Acid batteries regularly due to poor performance and now I think that I have a better platform for circumnavigation and we have less stresses on the boat.

if this is not the best thing that we did for our Boat It is very close to the best thing we could have done for the boat.

[nimblemotors]

This thread is useless for extracting information, and really should be closed.
I won't post to it anymore, because posting is spending your time helping people and not just the OP question, but people who search (and isn't everyone scolded to search first???) can find the 'answers' (i.e. opinions)

There was another thread started I think title (for the rest of us) or something, but this one continues to get new posts and the experts continue to reply here.

Originally Posted by Ex-Calif

I periodically jump in here to see the latest conversations.

It would be nice to have a (separate) thread with - Here is my "fully" installed and operational system and here is how it is performing for me.

This thread is great (vitally important?) for the science and the experimentation but the "after" pioneers really want a bill of materials and some setup instructions.

I know it is in here but it's like extracting pepper from fly sh!t.

Maybe some of you that are done could do that. "Sample LiFeP04 Setups"


Carry on men...

[senormechanico]

Then don't click on this thread !

Pretty simple really.

Our single 200 aH LiFePo4 bank runs everything on our boat and has for several years.

Shore power? Not since I installed them.

[nimblemotors]

Oh thanks, that was brilliant. Hey, you don't need to read my posts either.

Originally Posted by senormechanico

Then don't click on this thread !

Pretty simple really.

Our single 200 aH LiFePo4 bank runs everything on our boat and has for several years.

Shore power? Not since I installed them.

[GoingWalkabout]

Originally Posted by nimblemotors

This thread is useless for extracting information, and really should be closed.
I won't post to it anymore, because posting is spending your time helping people and not just the OP question, but people who search (and isn't everyone scolded to search first???) can find the 'answers' (i.e. opinions)

There was another thread started I think title (for the rest of us) or something, but this one continues to get new posts and the experts continue to reply here.

Why on earth close this thread? It is not useless for extracting information as you say. Just because the information doesn't concur with your last century world view. Im not meaning that as an insult but just an observation.

[goboatingnow]

Originally Posted by T1 Terry

Love it :lol: A bit of humour never goes astray. There will always a gulf between those that do hands on testing and those that just read about it and then try to type themselves smart... love that saying of Jack Rickard's There is no value in trying to adapt knowledge from electric vehicle use or tests on little cylindrical cells and apply it to house batteries, same cells but the use pattern is worlds apart.

T1 Terry

So if I replicate such use in cylindrical cells you'd still disagree.

Given the cells are all the same chemistry. Nothing I have tested or read says large prismatics are any difference

Dave


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[nimblemotors]

Originally Posted by GoingWalkabout

Why on earth close this thread? It is not useless for extracting information as you say. Just because the information doesn't concur with your last century world view. Im not meaning that as an insult but just an observation.

huh?? So you suggest someone interested in lithium batteries read through 4,300 posts to find out about them? When you search it shows a thread. Great a thread with 4,000 posts, how helpful.
Did you read ex-calif post?? So go bitch at him, not me then if you think he should read 4,000 posts.