Should we get more home battery capacity?

[johnb80]

Clearly Terry has had previous bad experiences in the past, I havent had any such experiences using more modern equipment etc. Active balancers are in use across the board and the power supplies / chargers I have used do have voltage adjustment as described in my setup description when the house batteries are at 75% adjust the output voltage to get the desired current out of the supply.

I think we've probably done this to death now so I'll say G'Day blue to Terry and crawl back under my stone regressing back to my 'Some Bloke In Lincolnshire' title.

Thanks everyone, have a great day.

 

[T1 Terry]

Clearly Terry has had previous bad experiences in the past, I havent had any such experiences using more modern equipment etc. Active balancers are in use across the board and the power supplies / chargers I have used do have voltage adjustment as described in my setup description when the house batteries are at 75% adjust the output voltage to get the desired current out of the supply.

I think we've probably done this to death now so I'll say G'Day blue to Terry and crawl back under my stone regressing back to my 'Some Bloke In Lincolnshire' title.

Thanks everyone, have a great day.

Over 12 yrs and over 200 off grid system installed, all built from cell level up, you get to see everything that can go wrong, generally, owner inflicted.
Some absolute horror stories, but I won't bore members with those .....
I have enjoyed our to and fro @johnb80, hope I didn't over step the mark anywhere, never mean to offend anyone

T1 Terry

 

[johnb80]

Over 12 yrs and over 200 off grid system installed, all built from cell level up, you get to see everything that can go wrong, generally, owner inflicted.
Some absolute horror stories, but I won't bore members with those .....
I have enjoyed our to and fro @johnb80, hope I didn't over step the mark anywhere, never mean to offend anyone

T1 Terry

No offence taken here at all, I'm used to people saying I'm wrong (even though it's untrue), I can live with that!

Take care everyone.

J

 

[Everest]

@johnb80... LOL, but you're not wrong.

but your understanding of LFP battery/cell behaviour is letting you down

Hmmm, having built my own 16S home storage battery system in 2022 and monitored it virtually daily, looking at BMS values for charging, individual cell voltages, temperatures and cell voltage deltas, I don't think so. Sure you can't tell LiFePO4 SOC from voltage alone due to their flat discharge curve - I've even posted about that on here in 2024 (see below). My point was that John's method of setting an external supply to a slightly lower voltage than a pack at 100% SOC is a sound one if your cells are reasonably balanced. With a balanced pack, it's unlikely at low charge current for an individual cell to get to 3.65V - that would need a delta of 250mV. If that did happen, then the BMS would trigger its cell-over-voltage-protection and cut off charge current.

Over and out

Post in thread 'MG4 LFP Battery state of health'

Dec 5, 2024

What I understand from what you said (please correct me if I'm talking nonsense) it is healthier not to charge a cell above 3.4V in terms of battery life. 3.4 x 125 x 104 = 44.2 kWh. Taking this value as reference, charging a lithium-ion battery with LFP cathode to 80% instead of fully charging it (excluding monthly balancing) will not charge a cell above 3.4V

I don't concur with that - for a number of reasons...

With regard to the capacity calculation... the kWh capacity of a battery pack is measured at the 'nominal' voltage of the cell, which for LFP is 3.2V. An LFP cell has a...

• Everest

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