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From: Bob La Londe <none@none.com99>
Newsgroups: rec.crafts.metalworking
Subject: Re: Got 4Ah, not 5Ah, battery 18V (20V) - done right thing?
Date: Sat, 18 May 2024 12:46:42 -0700
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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
> 
> -------------------------------------
> 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.



-- 
Bob La Londe
CNC Molds N Stuff


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