Cruisers Forum
 


Showing results 1 to 25 of 500
Search took 0.01 seconds.
Search: Posts Made By: OceanSeaSpray
Forum: Lithium Power Systems 06-05-2020, 16:50
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

Last year, I also attempted capacity recovery on my then 5.5-year old 4S bank, 77% usable capacity against nominal, first by cycling deeply and recharging to a higher 3.58V/cell and lower 0.01C tail...
Forum: Lithium Power Systems 25-07-2019, 15:50
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

That would all depend on what the controlled charge routine would look like. At the moment, I see no benefit in breaking up the pack or taking the BMS out.
My bank appears quite happy to keep...
Forum: Lithium Power Systems 25-07-2019, 14:27
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

SOC in this case is indeed an indication of SOH, but it doesn't mean that it can't be improved. It hasn't proven to be intractable yet, because there is a couple of approaches that I need to try. It...
Forum: Lithium Power Systems 24-07-2019, 19:16
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

"Return" current is meaningless. That is all the difference.
Forum: Lithium Power Systems 24-07-2019, 00:41
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

Residual current. No, charge voltage and residual current don't determine SOC, it depends too much on the charging history and age of the battery. It is only a termination condition.

1/...
Forum: Lithium Power Systems 22-07-2019, 04:14
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

A battery is close to 100% when it settles at an OCV also saying so following charging. Mine charges up to ~75% of nominal SOC according to Coulomb counting and the OCV then indicates about the same:...
Forum: Lithium Power Systems 21-07-2019, 20:01
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

My cells get into absorption starting at about 0.65C around 60% SOC. Then they stay in absorption for 1.5-2 hours to reach ~75% SOC and by then the current is down to C/40 and voltage at 3.5V/cell....
Forum: Lithium Power Systems 20-07-2019, 01:56
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

It is quite clear for me. When I have charged up to 76%, the voltage is up to target and the current so far down that it is taking forever to continue, so classic termination has been reached. The...
Forum: Lithium Power Systems 20-07-2019, 01:23
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

C/3?? You must mean C/30. In all cases, definitely not once the memory effect has deeply set in. I have tested raising the voltage and there is no easy answer in this direction. The battery is too...
Forum: Lithium Power Systems 29-06-2019, 16:10
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

The problem is not with the lithium you can move, that one is easy to shift and will give high currents, but with the one that won't shift.
Below this point, it is almost like operating a normal,...
Forum: Lithium Power Systems 29-06-2019, 15:49
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

Everybody knows that lithium cells require absorption. MaineSail has done 10 years of cycling with termination based on voltage and residual current with no memory effects.
"If properly...
Forum: Lithium Power Systems 27-06-2019, 16:46
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

It is all one and the same here. It initially shows as a small bump, but when left unchecked it leads to what we are experiencing. At least, the title differentiates from capacity loss due to loss of...
Forum: Lithium Power Systems 27-06-2019, 07:38
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

Today I increased the absorption voltage so the highest cells would reach 3.65V - I see some imbalance ranging from 3.51V to 3.65V when charging, but none after the cell voltages settle - and charged...
Forum: Lithium Power Systems 25-06-2019, 20:42
Replies: 7,525
Views: 1,374,802
Posted By OceanSeaSpray
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Only Victron and junk Chinese ones on Alibaba as far as I have seen. From a BMS electronics point of view, it is much easier and cheaper to switch the ground because you do it using N-channel MOSFET...
Forum: Lithium Power Systems 25-06-2019, 20:23
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

No. I was hoping that you would think about it. When something looks silly, sometimes it is because it is. So here we go:

"The cell voltage should still be holding above a certain value after a...
Forum: Lithium Power Systems 25-06-2019, 20:03
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

Coulomb counting (CC) = charged passed in Ah
Charge acceptance rate, i.e. residual current = charge current in A

The two are completely different. CC is based on the recent history of the cell,...
Forum: Lithium Power Systems 25-06-2019, 16:46
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

Yes, it is by definition reversible, once you manage to do it. What we are currently investigating here is what is required to achieve that once it has deeply set in over years of partial cycle use....
Forum: Lithium Power Systems 25-06-2019, 16:00
Replies: 7,525
Views: 1,374,802
Posted By OceanSeaSpray
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

The BIG missing point is charge termination, the higher the voltage, the more quickly you do damage when not terminating properly.

The other one is that you will quickly find that, in...
Forum: Lithium Power Systems 25-06-2019, 00:07
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

Delfin, what is your resting cell voltage 4 hours after termination with no load? This is what would give you a real idea of how high your cells recharge.

It is not because you do "this and that"...
Forum: Lithium Power Systems 24-06-2019, 15:12
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

The OCV curve I am using at has a datapoint for 78% SOC at 3.344V following a charge. It is consistent with the previous figures you posted, maybe just slightly higher.
When I attempted a second...
Forum: Lithium Power Systems 24-06-2019, 03:10
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

That strong dependency between the cell voltage and current is a sign of high internal resistance to charging. This is exactly what I have also observed.



Keep in mind that the longer you rest...
Forum: Lithium Power Systems 23-06-2019, 21:43
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

Great data. This kind of resting OCV after charging suggests cells in the 75-80% SOC range only, but note that you were definitely not fully absorbed with 0.07C at the end.

0.04C residual current...
Forum: Lithium Power Systems 20-06-2019, 12:35
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

I think that the general idea is sound. If you charge LFP cells at any "charging" voltage (i.e. >=3.4V/cell) and keep going, the current eventually goes down to zero, which is undesirable because the...
Forum: Lithium Power Systems 20-06-2019, 12:30
Replies: 7,525
Views: 1,374,802
Posted By OceanSeaSpray
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

I will now move to LFP memory effects thread - Cruisers & Sailing Forums (https://www.cruisersforum.com/forums/f14/lfp-memory-effects-thread-219814-post2912531.html) for further discussions.
Forum: Lithium Power Systems 20-06-2019, 11:48
Replies: 202
Views: 20,698
Posted By OceanSeaSpray
Re: LFP memory effects thread

I am reposting a summary of what I had in the other thread for the benefit of switching to this dedicated - and hopefully less "noisy" - thread. Thanks to evm1024 for creating it.
This below was...
Showing results 1 to 25 of 500

 
Forum Jump


All times are GMT -7. The time now is 20:37.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2022, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2022, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.