Re: (ET) Elec-trak Digest, Vol 15, Issue 41

["Robert" <euclid delhitel net>]

Dave,
My off grid system runs L/A Rolls batteries, it's over 10 years old and 
still working although not to the level it once did so I know long term 
battery care.

First, my recommendation for the ET is AGM batteries, not lithium and not 
open L/A. Lithium's advantage is in power to weight, in a tractor weight is 
in your favor so the extra expense has little benefit.
AGM's done right will give you a good run time and long life, they are more 
expensive, per watt/hour than L/A but worth it in my opinion, especially 
after just rebuilding two ETs and replacing most of the acid etched 
housings!
AGMs charge in a two or three phase cycle with current and voltage limiting. 
I do a lot of work with uCs and tying them to voltage and current control is 
something I've done before. When my charger is done I'll post it, talk is 
cheap so I figure I'll just put out the circuits and let everyone have at 
it, same with the motor control circuits.

Rob

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From: elec-trak-request cosmos phy tufts edu
Sent: Sunday, May 21, 2017 8:17 AM
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Subject: Elec-trak Digest, Vol 15, Issue 41

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Today's Topics:

  1.  Battery care (was Elec-trak Digest, Vol 15, Issue 39)
     (David Roden)

----------------------------------------------------------------------

Message: 1
Date: Sun, 21 May 2017 04:49:22 -0400
From: "David Roden" <etpost drmm net>
To: elec-trak cosmos phy tufts edu
Subject: (ET) Battery care (was Elec-trak Digest, Vol 15, Issue 39)
Message-ID: <59211C52 29015 625FFDC5 etpost drmm net>
Content-Type: text/plain; charset=US-ASCII

On 20 May 2017 at 18:33, Robert wrote:

> I disagree. I'm about to build AGM chargers for my batteries and ...
> it's simply a matter of reading the manufacturers data sheets and
> contouring the algorithm to their battery.

Good for you!  I wish you success.

My point was that the chargers for lots of mass-market rechargeable gadgets
don't do even that much.  Battery life just isn't a priority for the
companies' management.  Most of the chargers overcharge.

One of the benefits of the wider use of lithium ion batteries is that the
manufacturers HAVE to build in some charging smarts. Lead, NiCd, and NiMH
batteries can tolerate overcharging for a while, but a lithium battery with
little or no charging control will fail (maybe dramatically - remember the
hoverboards?) in relatively few cycles.

That said, I stand by the statement that charging batteries isn't a trivial
task.  I'll give you an example.

In a way, batteries are like people.  If they're not exercised regularly,
they lose strength (capacity).  But work them until they drop, and you'll
wear them out fast.  They need to be fed (charged) regularly and properly -- 
too little and they starve from sulfation, too much and they get fat from
grid corrosion.

I may be over-anthromorphizing here, but feeding a battery is also kind of
like feeding a person.

When you're a teenager, you can pretty much live on pizza, burgers, and
beer.  As you get into your 30s, you have to watch your diet or you gain
weight.  In your 40s and 50s and 60s, it's time to keep an eye on your
cholesterol and blood pressure, and choose your foods accordingly.

Batteries' needs also change with age.  The datasheets may tell you what to
do for a new battery, but charge an old battery by those standards, and
you'll accelerate its demise.

GE's ET charger is on the crude side.  However, I have to give their
engineers credit for taking battery age into account, even though it's not
automatic.


David Roden - Akron, Ohio, USA

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