"Larry Jaques" wrote in message
news
On Sun, 21 May 2017 19:49:32 -0400, "Jim Wilkins"
wrote:

..................
http://www.trojanbattery.com/pdf/Tro...UsersGuide.pdf
Diagram 4 gives 1-3% for flooded, Diagram 5 gives 0.5% for AGM.

I've downloaded both guides you've mentioned in the past several
days
and will have to compare them. Each one will have tidbits of info
the
other doesn't. That's the true benefit of research: gleaning
tidbits.


As mentioned, the current rises in older batteries and is an
indicator
of declining condition.

That sounds like something I should pay attention to.

I suspect it means that the self-discharge rate has increased and they
may need more frequent topping off. I don't know how it relates to
remaining capacity.


The second one matches other ammeters to 1 or 2 digits and I use
both
in series for discharge loads up to 10A. Together they each make
up
for the deficiencies of the other. The 12V,12Ah battery is
discharging
on them at 0.5A.

I forgot to ask what you meant by that. Are they drawing half an
amp
or showing that discharge rate?

I kept the current from the battery close to 0.5A by tweaking the
rheostat load. Surplus phone chargers power the meters and the relay
independently from the battery, since I won't be wasting my backup by
running these discharge tests into a dummy load during a power outage.

Some of my homebrew test equipment runs on AC power for better
accuracy, some on DC from the battery being tested or the solar panels
so it will still show demand or charging rate during a power outage.
The load current varies too much for accurate measurement and battery
remaining life prediction, but all I really need to know is if the
batteries can run the fridge overnight.

The box whose components I tested this morning will have a switch for
internal or external power. The meters have to be on external power to
measure single 18650 Lithiums to their discharge endpoint which is
below the minimum supply voltage..

The two of these I bought match the Fluke 8800A to 1mV. YMMV.
https://www.amazon.com/DROK-Digital-.../dp/B01BXZNK0C

Did I ever ask you why you didn't use a real battery for that? g
(real being 12v 35-275Ah) I set one up for use with the 45w HF
trio
of panels and was able to power a 14" electric chainsaw with the
2kW
modified sine wave inverter, also from HF. It would have taken
days
to recharge it (or more panels if needed for continued use.)

I do have "real" batteries that will run the fridge for about 20
hours. Once I'm satisfied with my discharge testing setup I'll get
to
them. For now I'm testing and risking smaller, older, less valuable
jumpstarter and UPS AGMs.

Smart.


These tests are too long to watch and if the
low voltage disconnect fails the battery could be drained flat
before
I notice.

That wouldn't be fun. How often do the disconnect programs (or
hardware/relays) fail?

How often do brakes fail?