[M] Redefining personal energy security - Page 3

 
Thanks, John, that reference is nicer than the ones we have. Mine  
measured 10.00222 on the seller's Agilent 34401A at 21C. It came with  
loose clips to hold a 12V A23 battery (which is below AD584 spec) but  
they don't line up well with the battery slot and were difficult to  
bend correctly and hold in place to solder.

  <ads> wrote in message  

You could measure electrolyte specific gravity if you recorded it at a  
known full charge. I've noticed that manufacturers tweak it to balance  
lifespan against maximum current, for example a deep discharge AGM  
might intentionally run out of acid before the plates are fully  
depleted. There are distinct differences among their recommendations  
for parameters like max charging current. Trojan says 10~13% of  
20-hour AH capacity, East Penn and many others allow 30%.
https://www.trojanbattery.com/tech-support/battery-maintenance/  

East Penn emailed me their battery charging instructions which I don't  
have permission to post.

 On Sun, 31 Mar 2019 10:15:17 -0400, "Jim Wilkins"


I do check the specific gravity of the few flooded batteries I have
and I record that.  Having sealed AGMs as the primary battery bank is
nice because there is no acid or hydrogen to deal with and they can
live in "people space" but you do lose the ability to check a key
parameter - the specific gravity.

 <ads> wrote in message  

I keep looking for good cheap AGMs. I don't have a source for decent  
used ones above 12V,18AH, and according to data sheet DOD-vs-life  
graphs even the cheaper flooded batteries cost more in depreciation  
than they save from free electricity, so my system is for power outage  
backup where storage life matters more. The battery makers admit that  
a -maintained- flooded battery can last longer than a  
maintenance-proof AGM.

Week-long outages are rare enough here that I don't think the lifespan  
loss from operating below full charge during one is that significant,  
as long as the battery is equalized afterwards. Power wheelchair  
batteries suffer the same problem of a too-brief indoor charge while  
the owner sleeps and may last a year or two.
https://batteryguy.com/kb/knowledge-base/how-long-should-an-electric-wheelchairscooter-battery-last/  
"An 8 hour overnight charge is usually not enough to return the  
battery to fully charged."
"Golf Carts which use a similar design to electric wheelchairs and  
scooters are known for using the same batteries, but achieving total  
life spans up to twice as long."

Don't ask me how he expects the disabled owner to swap heavy  
batteries.

 On Mon, 1 Apr 2019 09:30:28 -0400, "Jim Wilkins"


I have the six 90AH 12HX330FR batteries because I check the nearest
city's Craig's List site a couple of times each day.  New ones from
DataSafe are $
00 each, aftermarket brands are $
70 each (and up). I'm
retired and living on a (personally chosen) fixed income (I don't want
to outlive my money).  Had I known a little more about the batteries,
I would have squeezed my wallet much harder thaat month and bought
more of the used batteries at $
5 each (that's about $
0 more than the
scrap value at the time, 2 years ago).  

I've taken the battery bank apart a couple of times and let all the
batteries sit at rest for several days and all but one of the now 6
year old batteries was still in the voltage range of 100% SOC - the
one that missed it was about 0.05V low.  That would might be a good
match of batteries that were much newer.

In retrospect, getting 18 of the batteries would have been ideal, as
that's all that will fit on the shelving I'm using ;-)  Having 1620AH
would extend my "Wait until daylight" time out to a maximum of 3 days.
We all have 20/20 hindsight...

This week Craig's List has three J185 AGM batteries, 200AH at the 20
hour rate.  They are 2 years old and the seller is asking $
00 each
(new is  about $
50).  If I had the extra cash, I might start the
offer at $
00 each and go up to $
50 each.   However, these are a bit
heavy to handle alone at 122lbs each.

In response to the Battery Guy link:
I think the thing to understand is that the wheelchair/scooter makers
save money by including a charger that's barely adequate instead of a
somewhat more expensive charger plus an AH monitor on the device so
the charger A) could charge at a 4 hour rate if needed and B) know how
much charge was needed.  The sensors and microprocessors to do the
work are out there, they just add to the initial cost - but probably
not as much as the cost of one set of replacement batteries and
certainly not the cost of having a service tech replace the batteries
at whatever they use for "List" price plus labor.

I'm a battery miser, getting long life out of most of the rechargeable
batteries I own (from AA cells to 700 CCA vehicle batteries).  The OEM
battery on my truck lasted 6 years and I only replaced it because of
its age and winter being a month away.  I replaced that battery at 5
1/2 years because the starter sounded a little slower than normal (if
you drive a vehicle 10+ years, you should be attuned to the sounds it
makes).  With some TLC, that 5 1/2 year old Group 24 battery is now
part of my stable of lead acid batteries used for testing solar charge
controllers.  I don't want to trust it for 700 amps in January but
it's fine for longer term, lower power uses (last test was a 100 watt
incandescent bulb on a 1000 watt modified sine wave inverter for 2
hours.  That's was an 8.8 amp load for 2 hours, so almost 17.6AH which
is about a 20% discharge of a battery with a 130 minute RC at 25 amps
(that RC translates to a 79AH to 86AH equivalent).