Re: Got 4Ah, not 5Ah, battery 18V (20V) - done right thing?

On 5/17/2024 5:56 PM, Jim Wilkins wrote:

"Bob La Londe"  wrote in message news:v28jc3$2cs45$1@dont-email.me...
 On 5/17/2024 2:41 PM, Jim Wilkins wrote:

...

 I think its more likely adjustment of the internal BMS depending on how
the larger battery is configured to make it larger.  For instance if it
has an extra bank of cells it can 100% certainly deliver more current.
Just like tying two car batteries in parallel gives you more current
capacity.  I expect larger cells might also be capable of more current
if the conductors are sized accordingly.
Bob La Londe
CNC Molds N Stuff
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Beyond the BMS limits, the capacity and internal resistance depend on details of the chemical formulation and physical structure, such as particle size, which may be trade secrets. I've read that they can be traded off depending on the intended load current, higher resistance for greater capacity and vice versa.
https://www.linkedin.com/pulse/what-does-c-mean-lithium-ion-batteries-bruce-feng
 Marine batteries are similar, the high capacity deep cycle ones for trolling motors aren't recommended for engine starting current.
  

I think you are over thinking it.  Sure changes in technology can make a difference, but often larger battery packs are just larger.  Quite often when you dig into various mid to good quality battery packs you find they have the same cells from the same manufacturer.  Assembly quality is an issue, as is the choice and programming of the BMS, but the cells are the same.
I have a bit more experience with marine deep cycle lead acid batteries, and I don't think its as big of a deal as you think.  I've even run combined usage with the base ground battery doing double duty as the cranking battery and the ground battery for the trolling motor.  I've done it for years, and other anglers I know have done it for years before me.  Its a way to run a larger trolling motor when battery space is limited.  I did run four batteries in my current 20'10" bass boat because I have the room for them.  In my newest smaller acquisition there is no space for 4 batteries, but I noticed it has a 36V trolling motor on the bow.  They have just been running it on 24V.  Runs fine. Just less power.  I'll be converting it to the dual usage cranking battery configuration as soon as I have enough play money to buy all new matching batteries for that one.  Could they get better life if configured differently.  Maybe.  That all is a bit of a tangent though.
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Bob La Londe
CNC Molds N Stuff
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