Re: (ET) Vacuum running, man does it draw power.

["David Roden" <etpost drmm net>]

On 27 Oct 2019 at 17:18, Chris Zach wrote:

> However I can see the value of T105 cells in this case, with 180ah of
> capacity they would probably handle this load a bit better. Then again
> my BB600's are probably 20 years old with another 80 years of life
> left.... 

If you're running a 90ah battery flat in 30 mins, your load is 180 amps!  
That's HUGE.  Lead batteries do NOT like that kind of load.  Not onlly 
does 
their cycle life go down, old man Peukert steps in to clamp down on just 
how much energy you can really get from those batteries.  (Hint: it's not 
180 amp hours.)

But just for grins, let's see how Trojan T-105s would do for you.

A T-105 is 225ah at C20, and has a reserve capacity of 115 minutes at 75 
amps.  Using Uve Rick's handy-dandy battery calculator here

http://www.evdl.org/uve/battery.html

We see that at 180 amps, a T-105 will give you about 117 amp hours.  So 
you'd gain about 30% runtime.  But wait!  For decent cycle life (and at 
180 
amps you're going to get less of that regardless), you shouldn't draw a 
lead battery down past 20% SOC.  So let's use 80% of 117ah, which is about 
94ah.

I don't know how much T-105s cost these days, but I'm pretty sure they're 
not the $65 or so I recall them being 25-30 years ago.  Is an increase of 
4% runtime worth it?  Especially when you consider the much shorter life?


David Roden - Akron, Ohio, USA

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = 
Note: mail sent to the "etpost" address will not reach me.  To send 
me a private message, please use the address shown at the bottom
of this page : http://www.evdl.org/help/
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =