[AusNOG] EOL Battery Strings

[Curtis Bayne]

Cheers to everyone who has sent me information thus far. I've yet to find
anyone who is actually willing to supply me the batteries, but I have some
good leads to chase up.

For others interested in the same thing, I'd like to echo Ross' comment
that batteries are a hazardous material. Sulphuric acid and lead are both
toxic and should no be handled without suitable, AS-compliant PPE (not the
cheap stuff you bought off eBay).

Also, batteries can deliver insane amounts of current. Ask any sparky who
was worked in telephone exchanges and they will tell you stories of
wrenches dropped across bus bars which melt in a second - batteries deserve
as much (if not more) respect than LV (240V) grid power. Just because
they're ELV (<100VDC) does not make them inherently safe. If you don't
understand the implications of even seemingly minor details (such as not
using the correct arc-suppressing DC-rated breakers, or buying mislabed
Chinese garbage) then you're probably going to cause a fire.

I wasn't expecting to get so many responses and I'm anxious about raising
the noise floor on the list any higher, so I think it would be pertinent to
take this off list now so long as there are no objections.

Many thanks again,

-C


On Tue, Sep 2, 2014 at 1:35 PM, Ross Wheeler <ausnog at rossw.net> wrote:

>
> Cripes, you guys are all weirdos!
> I didn't expect to get innundated with requests... forgive me please
> moderators, for this semi-off-topic post. All those who emailed me
> directly, I'll try to get back to you and your individual questions and
> requests as soon as I can.
>
> For those who didn't ask already, or who have - perhaps this will address
> most of the more common questions!
>
> Cells seem to be removed from service after a given time, regardless of
> how many cycles they have (or have not) done.
>
> Cells typically lose capacity due to internal sulfation buildup on the
> plates and/or loss of electrolyte. Sealed cells can still dry out,
> especially if they are floated at too high a voltage.
>
> When buying ex-data-centre cells, it's a gamble what you'll get.
> Recovering AGM cells is an inexact science and no guarantees you'll get
> any good cells out the end of it. They are however generally pretty cheap.
>
> For anyone wanting to go "off-grid" for their home, I'd strongly suggest
> doing a REAL cost-benefits analysis for your specific site. It is almost
> certainly cheaper to use the grid. If you MUST or REALLY WANT TO go it
> yourself, you'll almost certainly underestimate the capacity you will need.
> AGMs are sensitive, finniky things that are easily destroyed with
> over-charging, over-discharging or simply cycling too deeply. Flooded
> lead-acid cells (traction batteries, forklift packs etc) are far more
> forgiving of abuse.
>
> I've lived 100% offgrid for almost 10 years now, and been through a few
> cells. Because my home and office is underground, venting FLA cells is
> problematic. To get decent cell life, plan on a MAXIMUM discharge of 20% of
> the batteries claimed capacity. (Eg, 2V/500AH cells, plan to discharge them
> no more than 100AH. In a 48V bank, that's under 5kWh usable capacity
> between sundown and sunup (best case, clear weather, solar panels on
> tracking frames, etc... for most of you, that 5kWh will be from
> mid-afternoon to mid-morning, and that's a BIG ask!)
>
> I've recently replaced 2 banks (48V/1000AH) of AGM with 300AH or LiFePO4
> which are about 1/8th the space and 1/10th the weight of the AGMs they
> replace, with slightly more usable daily watt-hours capacity).
>
> Batteries are NOT a "buy, connect, forget" investment. You will need to be
> dedicated and committed to them to get a decent life from them. You will
> need to adapt how you use power. But if you can/do, the benefits of being
> self-sufficient are substantial. (I've had zero power-failures in the
> almost 10 years I've been here... it was rare to go a few months without a
> power fail while I lived in town on-grid).
>
> Again, sorry for the off-topic post, and I'll try to get to all the
> private emails soon.
>
> RossW
>
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