Lithium Batteries (for the rest of us)

[dlentz]

Originally Posted by dlentz

Maybe a clue is the remote monitor for the charger. It labels the charge cycles as "Conditioning" when charging and "Ready" when in float. So maybe "float" is a misnomer in this particular instance. When in the "ready mode" the charger is set at a lower V potential than the pack, so I see no way to move electrons into the pack at that point. But why/how could the fridge cycle from the charger and not the pack?

What am I missing?
Dwain

Upon further reflection, I don't mean that a "name" someone puts on a piece of equipment means anything, just that perhaps in this case the equipment is truly sitting in a "ready mode", not supplying any voltage or current (therefore not a traditional "float or trickle" charge, maybe off )but ready to in the event voltage drops to the set point.
Plus, if I'm charging to 13.8v (pack) 3.45v (cells) I'm well below the knees and have plenty of charge capacity left at the top, so in that case would a "float charge" have the same effects as if the pack was closer to "full"?
I'm pretty sure a lot of this is virgin territory, there is little firm data on the use of these large prismatic cells in a house bank application, and, only my opinion, but from what little I can gather is that in this application we are putting these cells under Very LITTLE stress. So if a float charge is diminishing capacity by a small amount (how much? 20%,10% 2% over time) in a large bank used in house service, is the end of the world near? That being said it would always be prudent to care for your bank in the best ways that are reasonable. Yes, you can make this complicated, but where do the economics fall, ie: decent available programmable charge sources VS custom built PLC controls and chargers. Most people will need to make choices of whats the absolute best and what will work with perhaps some loss of performance.
Dwain

[dlentz]

Originally Posted by vRUN

Easy explanation for your observations ???

The battery bank is at 13.3 Volt most likely via a (silicon) diode connection to the house (fridge)
and house is at charger voltage i.e. at 13.2V to the fridge.

HOUSE: 13.3V +(-0.7V) = 12.6V battery vs. 13.2 V charger

... the battery won't supply, it can't be charged from house against the diode...
... charger does it all...

Your "intelligent!" charger did notice that no current was flowing into the battery --> no bulk cycle.
Your "intelligent! Pb charger" also noticed that the battery voltage was too low
while current was needed which it had to supply all alone
--> so the "defunct Pb battery" is "conditioned".

Seems all very (ILL-) Logical to me ...
...but what do I know about your system, especially the "Sterling Ultra 60"

At least maybe we need a schematic

Maybe it's just me, but HUH?
Dwain

[goboatingnow]

Originally Posted by vRUN

Thanks for the "power path" explanation. Big words for something seemingly obvious. (and yes I did google but found only things like the microchip "power path reference design" - which I <ahem> thought "bs")

Now I get it: "System Power Path Management allows end-users to charge their batteries without interruption." <eek>

Together with your above comment I can "dig" quite a few discussions (&vocabulary) I see in this thread. Li batteries are so very much closer to an immediate storage medium than a Pb battery. All those "intelligent" Pb chargers in parallel with a Li battery plus on top a Solar charger connected to the varying (ship) load do make for some really nice and unexpected ideosyncrasies.

Good thing my Pb charger is charging Pb batteries...
it will stay that way

Power path switching is a TI term, but its used throughout the Li charging IC industry.

Essentially it isolates from load sharing where , the power source can meet all the load requirements, Further more it isolates the charging circuit from the load sharing, removing float cycles and parallel load sharing that result in lots of mini charge /discharge cycles, which has proven to be detriment to long life.

yes you are right , PB chargers are designed for just just. Pb charging, everything else is a compromise.

Dave

[ebaugh]

Originally Posted by goboatingnow

The correct way to share a Li battery and a load, is often referred to as Power Path Switching. For longest life, the Li battery should supply the load via a Diode sharing path ( either ordinary or MOSFET ideal) Once the power supply/charger load current is within the limits, No voltage is impressed on the Li battery. If the load is greater then the charger, both charger and battery share the load, with the battery slowly discharging.

Separately , behind the diode splitter, a Li charge circuit kicks in at a predetermined voltage threshold to recharge the battery and then disconnect. That recharge point should ideally be set at the low discharge point.

Dave

Dave,

Is the attached what you are suggesting?

[Lagoon4us]

Once again a thread has become way too technical and somewhat argumentative, i'm enjoying the beer cooled by my fridge, powered by our simplistic Lithium cell arrangement, charged by the sun, goodnight Zeus and thank you.......What would i know?
Cheers all.

[chala]

Originally Posted by vRUN

….
Without adding resistors and stuff and only being able to measure voltages (which it sure is) you can access:
….
You will not be able to access a single cell

@chala: If you want to measure single cells you could add resistors and use Kirchhoffs law ...The current entering any junction is equal to the current leaving that junction. i2 + i3 = i1 + i4

Thanks. Do you know of any?
cell logger (that) read the voltage of individual cells when they are in parallel ( by) adding resistors and stuff.

[deckofficer]

Originally Posted by Lagoon4us

Once again a thread has become way too technical and somewhat argumentative, i'm enjoying the beer cooled by my fridge, powered by our simplistic Lithium cell arrangement, charged by the sun, goodnight Zeus and thank you.......What would i know?
Cheers all.

So your an early adopter for the convenience of the technology instead of the technical tangibles?

Can't blame you for that, as all the technical is scaring folks away from the upgrade that will make their life easier. Nobody likes to lug batteries every couple of years or have them exhausted in remote areas.

What it boils down to is no battery chemistry tolerates overcharging or running flat. It is just because of the initial cost of the lithium cells folks want to protect their investment. If you always have treated your batteries well by not over charging or running flat, then the LiFePO4 is pretty much plug and play replacements for lead. The voltages are that close. Automatic systems that keep the cells from too low or too high voltages is good for all who have abused any battery in the past.

[transmitterdan]

Originally Posted by ebaugh

Dave,

Is the attached what you are suggesting?

Thanks for posting the picture. Now it makes sense what GBN (Dave) has been saying. Sorry for being dense.

If the relay is closed anytime the battery needs charging or when the charger is powered off this circuit will avoid floating the battery. But it still allows the house voltage to remain at the charger's float voltage without discharging the battery at all.

Does anyone know if a company makes a device that does this automatically? It would seem such a device if it incorporated one additional relay to handle HVC and LVC features would make simple LI packs usable by most all ordinary charging systems. That's something many people would like to have I think.

[ebaugh]

Originally Posted by Lagoon4us

Once again a thread has become way too technical and somewhat argumentative, i'm enjoying the beer cooled by my fridge, powered by our simplistic Lithium cell arrangement, charged by the sun, goodnight Zeus and thank you.......What would i know?
Cheers all.

Maybe? But I'm enjoying a cold one while I study the problem, and hope to learn something, maybe even figure out how to squeeze a few more cycles and use the savings to replenish the cold ones...

If my observed 15% capacity fade after 1 year doesn't stop on it's own (it may) and/or an operating adjustment is made to slow the the aging, the case for LFP is reduced.

[chala]

Originally Posted by Lagoon4us

Once again a thread has become way too technical and somewhat argumentative, i'm enjoying the beer cooled by my fridge, powered by our simplistic Lithium cell arrangement, charged by the sun, goodnight Zeus and thank you.......What would i know?
Cheers all.

Is this too (argumentative)?

Originally Posted by vRUN

I do not own a Junsie (so should probably refrain from commenting but...).

The short look inside "revealed" an ATMEL uP (Microprocessor) is used internally. The Atmel voltage reference is described here. (page 5)
Since you probably do not want to read all that stuff let me summarize as:
Even under ideal conditions I expect +20 to -40mV difference
(and don't you engineers bash me for being inaccurate )
My imax B6 charger ("junsie that can charge") does work in that region, so does my (Atmel based) LiPo Voltage Checker and Balancer (all are "copies"?).

3.85 V (may be 3.87 or 3.81) (and 3.80 or 3.90 readings wouldn't shock me )

I find it more a reason to enjoy (the beer).

[chala]

Originally Posted by ebaugh

If my observed 15% capacity fade after 1 year

Can you indicate to me the post (posts) that relate to that observation?

Originally Posted by ebaugh

the case for LFP is reduced.

May be the case for LFP in parallel is reduced.

[vRUN]

Originally Posted by dlentz

Maybe it's just me, but HUH?
Dwain

Just look at the schematic posted ... Is this your circuit ?

...and add (in case you didn't know:
Every bipolar silicon p-n diode has a voltage drop of about 0.7Volts)

So again:
Seen from the HOUSE voltage
(1) your battery-path has the low voltage.
(2) the charger has a high voltage & supplies all current.
(3) the battery cannot be charged from House, Diode prevents it!

READ AGAIN!

[vRUN]

Originally Posted by chala

Thanks. Do you know of any? cell logger ...

Sorry I am too new to Li Boat House Banks to be of any help in what's available on the market ... newbie... but you knew that
But...and a big BUT at that... the practical experience by T1, Maine etc. etc. seems to say "not relevant anyway".
BTW: In my practical experience with smaller LiPo Batteries it is much easier to identify a bad cell by the heat it generates or even worse, seeing it starting to blow up its bag.

Originally Posted by chala

I find it more a reason to enjoy (the beer).

Hope I wasn't too detailed or explaining "above your's and Lagoon4us's head".
Again (in layman's terms): If you read 3.85 Volts accept it as being somewhere between say 3.80 and 3.90 Volts

Junsie: $12 actually is a sales price with a good margin (uP+parts maybe $6)
I cannot guess the sales price of the equipment Lagoon4us mentioned but believe me there is a serious amount of "rare equipment engineering" together with "very price insensitive market" included

[vRUN]

Originally Posted by Lagoon4us

Once again a thread has become way too technical and somewhat argumentative, i'm enjoying the beer...

SORRY?
I promise to be quiet ... at least until monday

Meanwhile you may have (a beer on me / mine as well) whatever pleases you more. You are in Greece now - correct? If I look out the window it does rain

[dlentz]

Originally Posted by vRUN

Just look at the schematic posted ... Is this your circuit ?

...and add (in case you didn't know:
Every bipolar silicon p-n diode has a voltage drop of about 0.7Volts)

So again:
Seen from the HOUSE voltage
(1) your battery-path has the low voltage.
(2) the charger has a high voltage & supplies all current.
(3) the battery cannot be charged from House, Diode prevents it!

READ AGAIN!

There is NO diode involved. (Your assumption). There is a House Battery Bank, and a common, readily available, programmable shore charger connected directly to the common Positive Buss (all fused properly). The charger is set at 13.8v and 13.2v. The House battery bank stays between 13.3-13.4 for the vast majority of the discharge cycle. When there is a current draw on the house bank(fridge) the charger steps up and handles it even though it's set at a lower voltage. There is no noticeable charge or discharge out of the House Battery bank at that point. I would have expected the House battery bank to run the draw (fridge) until it reached the float/ready setting of the charger, that is what I am surprised at.
Anyway I'm with Lagoon , my fridge is happily working away, while I'm away. Simple.
Dwain