Subject: Re: [Shop-talk] AGM batteries: Protect from freezing?

From: Philip Ethier <[email-masked]>
Date: Fri, 14 Nov 2025 01:55:48 -0600

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On Fri, Nov 14, 2025 at 1:34=E2=80=AFAM Philip Ethier <[email-masked]> =
wrote:

> Absorbed Gas Mat batteries:
>

OOPS. Absorbent glass mat

>
> If you leave a vehicle outside all winter in a cold climate without
> charging the AGM batteries, will they be ruined by the cold?
>
> I know that regular lead-acid batteries can freeze up, but I don't know
> about AGM batteries.
>
>
> --
> Phil Ethier, West Side, Saint Paul Minnesota, USA
> 2006 Gulf Stream Conquest Super C, 8.1, white
> 2011 Cayman 2.9 PDK, white
> 2021 Ford F-150 3500cc twin turbo, white
> 1991 Caterham 1700 Super Sprint, not white
> www.mnautox.com
>
>

--=20
Phil Ethier, West Side, Saint Paul Minnesota, USA
2006 Gulf Stream Conquest Super C, 8.1, white
2011 Cayman 2.9 PDK, white
2021 Ford F-150 3500cc twin turbo, white
1991 Caterham 1700 Super Sprint, not white
www.mnautox.com

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<div dir=3D"ltr"><div dir=3D"ltr"><div dir=3D"ltr"><div class=3D"gmail_defa=
ult" style=3D"font-family:monospace"><br></div></div><br><div class=3D"gmai=
l_quote"><div dir=3D"ltr" class=3D"gmail_attr">On Fri, Nov 14, 2025 at 1:34=
=E2=80=AFAM Philip Ethier &lt;<a href=3D"mailto:[email-masked]" target=
=3D"_blank">[email-masked]</a>&gt; wrote:<br></div><blockquote class=3D=
"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(2=
04,204,204);padding-left:1ex"><div dir=3D"ltr"><div><div style=3D"font-fami=
ly:monospace">Absorbed Gas Mat batteries:</div></div></div></blockquote><di=
v><br></div><div class=3D"gmail_default" style=3D"font-family:monospace">OO=
PS.=C2=A0<span style=3D"color:inherit;font-size:inherit;font-style:inherit;=
font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inheri=
t;font-family:&quot;Linux Libertine&quot;,Georgia,Times,&quot;Source Serif =
4&quot;,serif">Absorbent glass mat</span></div><blockquote class=3D"gmail_q=
uote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,2=
04);padding-left:1ex"><div dir=3D"ltr"><div><div style=3D"font-family:monos=
pace"><br></div><div style=3D"font-family:monospace">If you leave a vehicle=
 outside all winter in a cold climate without charging the AGM batteries, w=
ill they be ruined=C2=A0by the cold?</div><div style=3D"font-family:monospa=
ce"><br></div><div style=3D"font-family:monospace">I know that regular lead=
-acid batteries can freeze up, but I don&#39;t know about AGM batteries.</d=
iv><br clear=3D"all"></div><div><br></div><span class=3D"gmail_signature_pr=
efix">-- </span><br><div dir=3D"ltr" class=3D"gmail_signature"><div dir=3D"=
ltr"><div dir=3D"ltr"><div dir=3D"ltr"><div dir=3D"ltr"><div><span style=3D=
"color:rgb(0,0,0);font-size:12.8px;background-color:rgb(255,255,255)"><font=
 face=3D"monospace">Phil Ethier, West Side, Saint Paul Minnesota, USA</font=
></span></div><div><span style=3D"font-family:monospace;color:rgb(0,0,0)">2=
006 Gulf Stream Conquest Super C, 8.1, white</span></div><div><span style=
=3D"color:rgb(0,0,0);background-color:rgb(255,255,255)"><font face=3D"monos=
pace">2011 Cayman 2.9 PDK, white</font></span></div><div><span style=3D"col=
or:rgb(0,0,0);background-color:rgb(255,255,255)"><font face=3D"monospace">2=
021 Ford F-150 3500cc twin turbo, white</font></span></div><div><span style=
=3D"background-color:rgb(255,255,255)"><font face=3D"monospace">1991 Caterh=
am 1700 Super Sprint, not white</font><br style=3D"color:rgb(0,0,0);font-fa=
mily:verdana,geneva,lucida,&quot;lucida grande&quot;,arial,helvetica,sans-s=
erif"><a href=3D"http://www.mnautox.com/" style=3D"color:rgb(0,24,57);font-=
family:verdana,geneva,lucida,&quot;lucida grande&quot;,arial,helvetica,sans=
-serif" target=3D"_blank">www.mnautox.com<br></a></span><br></div></div></d=
iv></div></div></div></div>
</blockquote></div><div><br clear=3D"all"></div><div><br></div><span class=
=3D"gmail_signature_prefix">-- </span><br><div dir=3D"ltr" class=3D"gmail_s=
ignature"><div dir=3D"ltr"><div dir=3D"ltr"><div dir=3D"ltr"><div dir=3D"lt=
r"><div><span style=3D"color:rgb(0,0,0);font-size:12.8px;background-color:r=
gb(255,255,255)"><font face=3D"monospace">Phil Ethier, West Side, Saint Pau=
l Minnesota, USA</font></span></div><div><span style=3D"font-family:monospa=
ce;color:rgb(0,0,0)">2006 Gulf Stream Conquest Super C, 8.1, white</span></=
div><div><span style=3D"color:rgb(0,0,0);background-color:rgb(255,255,255)"=
><font face=3D"monospace">2011 Cayman 2.9 PDK, white</font></span></div><di=
v><span style=3D"color:rgb(0,0,0);background-color:rgb(255,255,255)"><font =
face=3D"monospace">2021 Ford F-150 3500cc twin turbo, white</font></span></=
div><div><span style=3D"background-color:rgb(255,255,255)"><font face=3D"mo=
nospace">1991 Caterham 1700 Super Sprint, not white</font><br style=3D"colo=
r:rgb(0,0,0);font-family:verdana,geneva,lucida,&quot;lucida grande&quot;,ar=
ial,helvetica,sans-serif"><a href=3D"http://www.mnautox.com/" style=3D"colo=
r:rgb(0,24,57);font-family:verdana,geneva,lucida,&quot;lucida grande&quot;,=
arial,helvetica,sans-serif" target=3D"_blank">www.mnautox.com<br></a></span=
><br></div></div></div></div></div></div></div>
</div>

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_______________________________________________

[email-masked]
Archive: http://www.team.net/pipermail/shop-talk http://autox.team.net/archive

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From: DAVID MASSEY <[email-masked]>
Date: Fri, 14 Nov 2025 12:42:29 +0000 (UTC)

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It all depends on the level of charge.=C2=A0 A fully charged battery will f=
reeze at about -70 deg F but a fully discharged battery will freeze at 32 d=
eg F.=C2=A0 At 50% charge it will freeze at about -15 deg F.=C2=A0 An AGM b=
attery is a bit lower.=C2=A0 Below is a curve from USBattery.com

Since you live in an area that can expect sub-zero (F) temperatures at some=
 point over the winter leaving it out with a state of charge less than 60% =
is risky.
Dave=20

=20

    On Friday, November 14, 2025 at 02:39:12 AM CST, Philip Ethier <pethier=
[email-masked]> wrote:  =20

=20

OOPS.=C2=A0Absorbent glass mat

If you leave a vehicle outside all winter in a cold climate without chargin=
g the AGM batteries, will they be ruined=C2=A0by the cold?
I know that regular lead-acid batteries can freeze up, but I don't know abo=
ut AGM batteries.

--=20
Phil Ethier, West Side, Saint Paul Minnesota, USA2006 Gulf Stream Conquest =
Super C, 8.1, white2011 Cayman 2.9 PDK, white2021 Ford F-150 3500cc twin tu=
rbo, white1991 Caterham 1700 Super Sprint, not white
www.mnautox.com

--=20
Phil Ethier, West Side, Saint Paul Minnesota, USA2006 Gulf Stream Conquest =
Super C, 8.1, white2011 Cayman 2.9 PDK, white2021 Ford F-150 3500cc twin tu=
rbo, white1991 Caterham 1700 Super Sprint, not white
www.mnautox.com

[email-masked]
Archive: http://www.team.net/pipermail/shop-talk http://autox.team.net/arch=
ive

[email-masked]

 =20
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<html><head></head><body><div class=3D"ydp6a9917dayahoo-style-wrap" style=
=3D"font-family:Arial, Helvetica, sans-serif;font-size:16px;"><div><div dir=
=3D"ltr" data-setdir=3D"false">It all depends on the level of charge.&nbsp;=
 A fully charged battery will freeze at about -70 deg F but a fully dischar=
ged battery will freeze at 32 deg F.&nbsp; At 50% charge it will freeze at =
about -15 deg F.&nbsp; An AGM battery is a bit lower.&nbsp; Below is a curv=
e from USBattery.com</div><div dir=3D"ltr" data-setdir=3D"false"><br></div>=
<div dir=3D"ltr" data-setdir=3D"false"><img title=3D"Inline image" alt=3D"I=
nline image" src=3D"cid:[email-masked]" cla=
ss=3D"yahoo-inline-image" draggable=3D"false" style=3D"max-width: 555px; wi=
dth: 100%;" data-id=3D"&lt;[email-masked]&g=
t;"><br><span></span><br></div><div dir=3D"ltr" data-setdir=3D"false">Since=
 you live in an area that can expect sub-zero (F) temperatures at some poin=
t over the winter leaving it out with a state of charge less than 60% is ri=
sky.</div><div><br></div><div class=3D"ydp6a9917dasignature"><div style=3D"=
color: black; font-style: normal; font-size-adjust: none; font-weight: norm=
al; font-stretch: normal; font-size: 12pt; line-height: normal; font-family=
: Arial, Helvetica, sans-serif;"><div style=3D"color: black; font-style: no=
rmal; font-size-adjust: none; font-weight: normal; font-stretch: normal; fo=
nt-size: 12pt; line-height: normal; font-family: Arial, Helvetica, sans-ser=
if;"><div><font size=3D"4">Dave <br></font></div><div><span style=3D"font-s=
ize:10.0pt;font-family:sans-serif;color:black;"><br></span></div><br></div>=
</div></div></div>
        <div><br></div><div><br></div>
       =20
        </div><div id=3D"ydp504f502yahoo_quoted_3864829564" class=3D"ydp504=
f502yahoo_quoted"><div class=3D"ydp504f502yahoo-style-wrap" style=3D"font-f=
amily:Arial, Helvetica, sans-serif;font-size:16px;">
            <div style=3D"font-family:'Helvetica Neue', Helvetica, Arial, s=
ans-serif;font-size:13px;color:#26282a;">
               =20
                <div class=3D"ydp504f502quoted-text-header">
                        On Friday, November 14, 2025 at 02:39:12 AM CST, Ph=
ilip Ethier &lt;[email-masked]&gt; wrote:
                    </div>
                </div><div style=3D"font-family:'Helvetica Neue', Helvetica=
, Arial, sans-serif;font-size:13px;color:#26282a;border-left: 1px solid #cc=
c;padding-left: 8px;margin: 0px 0px 0px 8px" class=3D"ydp504f502inline_repl=
y_quote_container" data-split-quote-node=3D"true">
                <div><br></div><div><br></div>
                <div><div id=3D"ydp504f502yiv7157825480"><div dir=3D"ltr"><=
div dir=3D"ltr"><div dir=3D"ltr"><div style=3D"font-family:monospace;" clas=
s=3D"ydp504f502yiv7157825480gmail_default"><br></div></div><br><div class=
=3D"ydp504f502yiv7157825480gmail_quote"><div dir=3D"ltr" class=3D"ydp504f50=
2yiv7157825480gmail_attr">On Fri, Nov 14, 2025 at 1:34=E2=80=AFAM Philip Et=
hier &lt;<a href=3D"mailto:[email-masked]" rel=3D"nofollow" target=3D"_=
blank">[email-masked]</a>&gt; wrote:<br></div><blockquote style=3D"marg=
in:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1e=
x;" class=3D"ydp504f502yiv7157825480gmail_quote"><div dir=3D"ltr"><div><div=
 style=3D"font-family:monospace;">Absorbed Gas Mat batteries:</div></div></=
div></blockquote><div><br></div><div style=3D"font-family:monospace;" class=
=3D"ydp504f502yiv7157825480gmail_default">OOPS.&nbsp;<span style=3D"color:i=
nherit;font-size:inherit;font-style:inherit;font-weight:inherit;font-family=
:Georgia, Times, Serif serif;">Absorbent glass mat</span></div><blockquote =
style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);pa=
dding-left:1ex;" class=3D"ydp504f502yiv7157825480gmail_quote"><div dir=3D"l=
tr"><div><div style=3D"font-family:monospace;"><br></div><div style=3D"font=
-family:monospace;">If you leave a vehicle outside all winter in a cold cli=
mate without charging the AGM batteries, will they be ruined&nbsp;by the co=
ld?</div><div style=3D"font-family:monospace;"><br></div><div style=3D"font=
-family:monospace;">I know that regular lead-acid batteries can freeze up, =
but I don't know about AGM batteries.</div><br clear=3D"all"></div><div><br=
></div><span class=3D"ydp504f502yiv7157825480gmail_signature_prefix">-- </s=
pan><br><div dir=3D"ltr" class=3D"ydp504f502yiv7157825480gmail_signature"><=
div dir=3D"ltr"><div dir=3D"ltr"><div dir=3D"ltr"><div dir=3D"ltr"><div><sp=
an style=3D"color:rgb(0,0,0);font-size:12.8px;background-color:rgb(255,255,=
255);"><font face=3D"monospace" style=3D"background-color: inherit;">Phil E=
thier, West Side, Saint Paul Minnesota, USA</font></span></div><div><span s=
tyle=3D"font-family:monospace;color:rgb(0,0,0);">2006 Gulf Stream Conquest =
Super C, 8.1, white</span></div><div><span style=3D"color:rgb(0,0,0);backgr=
ound-color:rgb(255,255,255);"><font face=3D"monospace" style=3D"background-=
color: inherit;">2011 Cayman 2.9 PDK, white</font></span></div><div><span s=
tyle=3D"color:rgb(0,0,0);background-color:rgb(255,255,255);"><font face=3D"=
monospace" style=3D"background-color: inherit;">2021 Ford F-150 3500cc twin=
 turbo, white</font></span></div><div><span style=3D"background-color:rgb(2=
55,255,255);"><font face=3D"monospace" style=3D"background-color: inherit;"=
>1991 Caterham 1700 Super Sprint, not white</font><br style=3D"color:rgb(0,=
0,0);font-family:verdana, geneva, lucida, arial, helvetica, sans-serif;"><a=
 href=3D"http://www.mnautox.com/" style=3D"color:rgb(0,24,57);font-family:v=
erdana, geneva, lucida, arial, helvetica, sans-serif;" rel=3D"nofollow" tar=
get=3D"_blank">www.mnautox.com<br></a></span><br></div></div></div></div></=
div></div></div>
</blockquote></div><div><br clear=3D"all"></div><div><br></div><span class=
=3D"ydp504f502yiv7157825480gmail_signature_prefix">-- </span><br><div dir=
=3D"ltr" class=3D"ydp504f502yiv7157825480gmail_signature"><div dir=3D"ltr">=
<div dir=3D"ltr"><div dir=3D"ltr"><div dir=3D"ltr"><div><span style=3D"colo=
r:rgb(0,0,0);font-size:12.8px;background-color:rgb(255,255,255);"><font fac=
e=3D"monospace" style=3D"background-color: inherit;">Phil Ethier, West Side=
, Saint Paul Minnesota, USA</font></span></div><div><span style=3D"font-fam=
ily:monospace;color:rgb(0,0,0);">2006 Gulf Stream Conquest Super C, 8.1, wh=
ite</span></div><div><span style=3D"color:rgb(0,0,0);background-color:rgb(2=
55,255,255);"><font face=3D"monospace" style=3D"background-color: inherit;"=
>2011 Cayman 2.9 PDK, white</font></span></div><div><span style=3D"color:rg=
b(0,0,0);background-color:rgb(255,255,255);"><font face=3D"monospace" style=
=3D"background-color: inherit;">2021 Ford F-150 3500cc twin turbo, white</f=
ont></span></div><div><span style=3D"background-color:rgb(255,255,255);"><f=
ont face=3D"monospace" style=3D"background-color: inherit;">1991 Caterham 1=
700 Super Sprint, not white</font><br style=3D"color:rgb(0,0,0);font-family=
:verdana, geneva, lucida, arial, helvetica, sans-serif;"><a href=3D"http://=
www.mnautox.com/" style=3D"color:rgb(0,24,57);font-family:verdana, geneva, =
lucida, arial, helvetica, sans-serif;" rel=3D"nofollow" target=3D"_blank">w=
ww.mnautox.com<br></a></span><br></div></div></div></div></div></div></div>
</div>
</div>_______________________________________________<br><br><a href=3D"mai=
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[email-masked]

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---

From: David Scheidt <[email-masked]>
Date: Fri, 14 Nov 2025 08:30:15 -0600

--===============7350540737432117278==
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--Apple-Mail-37DE7577-D238-47E4-A55B-A7925738F188
	charset=utf-8
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<html><head><meta http-equiv=3D"content-type" content=3D"text/html; charset=3D=
utf-8"></head><body dir=3D"auto"><div dir=3D"ltr"></div><div dir=3D"ltr">Agm=
 batteries freeze, at sufficiently low temperatures and state of charge. The=
y do have very low self discharge, so charging before it=E2=80=99s too cold s=
hould have them charged enough for the winter. &nbsp;(Assuming they=E2=80=99=
re disconnected, of course .).&nbsp;</div><div dir=3D"ltr"><br></div><div di=
r=3D"ltr"><br></div><div dir=3D"ltr"><br><blockquote type=3D"cite">On Nov 14=
, 2025, at 02:24, Philip Ethier &lt;[email-masked]&gt; wrote:<br><br></b=
lockquote></div><blockquote type=3D"cite"><div dir=3D"ltr">=EF=BB=BF<div dir=
=3D"ltr"><div dir=3D"ltr"><div dir=3D"ltr"><div class=3D"gmail_default" styl=
e=3D"font-family:monospace"><br></div></div><br><div class=3D"gmail_quote"><=
div dir=3D"ltr" class=3D"gmail_attr">On Fri, Nov 14, 2025 at 1:34=E2=80=AFAM=
 Philip Ethier &lt;<a href=3D"mailto:[email-masked]" target=3D"_blank">p=
[email-masked]</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" s=
tyle=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padd=
ing-left:1ex"><div dir=3D"ltr"><div><div style=3D"font-family:monospace">Abs=
orbed Gas Mat batteries:</div></div></div></blockquote><div><br></div><div c=
lass=3D"gmail_default" style=3D"font-family:monospace">OOPS.&nbsp;<span styl=
e=3D"color:inherit;font-size:inherit;font-style:inherit;font-variant-ligatur=
es:inherit;font-variant-caps:inherit;font-weight:inherit;font-family:&quot;L=
inux Libertine&quot;,Georgia,Times,&quot;Source Serif 4&quot;,serif">Absorbe=
nt glass mat</span></div><blockquote class=3D"gmail_quote" style=3D"margin:0=
px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><d=
iv dir=3D"ltr"><div><div style=3D"font-family:monospace"><br></div><div styl=
e=3D"font-family:monospace">If you leave a vehicle outside all winter in a c=
old climate without charging the AGM batteries, will they be ruined&nbsp;by t=
he cold?</div><div style=3D"font-family:monospace"><br></div><div style=3D"f=
ont-family:monospace">I know that regular lead-acid batteries can freeze up,=
 but I don't know about AGM batteries.</div><br clear=3D"all"></div><div><br=
></div><span class=3D"gmail_signature_prefix">-- </span><br><div dir=3D"ltr"=
 class=3D"gmail_signature"><div dir=3D"ltr"><div dir=3D"ltr"><div dir=3D"ltr=
"><div dir=3D"ltr"><div><span style=3D"color:rgb(0,0,0);font-size:12.8px;bac=
kground-color:rgb(255,255,255)"><font face=3D"monospace">Phil Ethier, West S=
ide, Saint Paul Minnesota, USA</font></span></div><div><span style=3D"font-f=
amily:monospace;color:rgb(0,0,0)">2006 Gulf Stream Conquest Super C, 8.1, wh=
ite</span></div><div><span style=3D"color:rgb(0,0,0);background-color:rgb(25=
5,255,255)"><font face=3D"monospace">2011 Cayman 2.9 PDK, white</font></span=
></div><div><span style=3D"color:rgb(0,0,0);background-color:rgb(255,255,255=
)"><font face=3D"monospace">2021 Ford F-150 3500cc twin turbo, white</font><=
/span></div><div><span style=3D"background-color:rgb(255,255,255)"><font fac=
e=3D"monospace">1991 Caterham 1700 Super Sprint, not white</font><br style=3D=
"color:rgb(0,0,0);font-family:verdana,geneva,lucida,&quot;lucida grande&quot=
;,arial,helvetica,sans-serif"><a href=3D"http://www.mnautox.com/" style=3D"c=
olor:rgb(0,24,57);font-family:verdana,geneva,lucida,&quot;lucida grande&quot=
;,arial,helvetica,sans-serif" target=3D"_blank">www.mnautox.com<br></a></spa=
n><br></div></div></div></div></div></div></div>
</blockquote></div><div><br clear=3D"all"></div><div><br></div><span class=3D=
"gmail_signature_prefix">-- </span><br><div dir=3D"ltr" class=3D"gmail_signa=
ture"><div dir=3D"ltr"><div dir=3D"ltr"><div dir=3D"ltr"><div dir=3D"ltr"><d=
iv><span style=3D"color:rgb(0,0,0);font-size:12.8px;background-color:rgb(255=
,255,255)"><font face=3D"monospace">Phil Ethier, West Side, Saint Paul Minne=
sota, USA</font></span></div><div><span style=3D"font-family:monospace;color=
:rgb(0,0,0)">2006 Gulf Stream Conquest Super C, 8.1, white</span></div><div>=
<span style=3D"color:rgb(0,0,0);background-color:rgb(255,255,255)"><font fac=
e=3D"monospace">2011 Cayman 2.9 PDK, white</font></span></div><div><span sty=
le=3D"color:rgb(0,0,0);background-color:rgb(255,255,255)"><font face=3D"mono=
space">2021 Ford F-150 3500cc twin turbo, white</font></span></div><div><spa=
n style=3D"background-color:rgb(255,255,255)"><font face=3D"monospace">1991 C=
aterham 1700 Super Sprint, not white</font><br style=3D"color:rgb(0,0,0);fon=
t-family:verdana,geneva,lucida,&quot;lucida grande&quot;,arial,helvetica,san=
s-serif"><a href=3D"http://www.mnautox.com/" style=3D"color:rgb(0,24,57);fon=
t-family:verdana,geneva,lucida,&quot;lucida grande&quot;,arial,helvetica,san=
s-serif" target=3D"_blank">www.mnautox.com<br></a></span><br></div></div></d=
iv></div></div></div></div>
</div>
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From: Bob Spidell <[email-masked]> SJlVk6xSergESldBuZ8puNVB20BeAFalvFvv+kjFqTPw8jzPYzlvX3lG1PT6j+QdDxHcWGkfTuHjNIVmxBDbCVAf+d/WRbl7fv4=
Date: Fri, 14 Nov 2025 06:56:02 -0800

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Interesting question. I'm not a hexpert, but I have a lot of cars and 
farm/garden equipment that need batteries--including a new EV--so I 
spend a lot of time thinking about batteries. I have AGMs in both my 
Austin-Healeys; in one because it originally had two 6V batteries in 
parallel and replacements in an appropriate size are all but NLA, and in 
one because they're just flat-ass better (and I got tired of 
neutralizing/cleaning acid spills in the boot--'trunk' for you Yankees (:)).

IMO, AGM are better because they seem to generally be better 
constructed, and because the electrolyte--concentrated sulfuric acid--is 
constrained by the fibrous 'mat.' Otherwise, the chemistry is the same 
as any other lead-acid (note 'SLA,' or 'sealed lead acid,' aka 
'maintenance-free' batteries seem to be generally overall quality and I 
buy them when I can).

Since this question was new to me, I did some digging:

https://discoverbattery.com/support/learning-center/battery-101/what-is-the-freezing-point-of-battery-acid-electrolyte

This is something I hadn't known; that the freezing point varies with 
state-of-charge so, first off, if your battery is going to endure 
freezing temps make sure it's fully charged. I have several battery 
minders/tenders, and bought one especially for AGMs, and I use them (the 
tractors sometimes sit for weeks and, when I need them, I need them).

Here's another thing I hadn't considered, but I live in the California 
Central Valley and we rarely get below-freezing weather (TL;DR: cold 
weather bad: "Cold weather accelerates wear and tear on batteries"):

https://www.relionbattery.com/blog/top-4-factors-to-consider-for-a-cold-weather-battery

So, yeah, freezing conditions are not good for lead-acid batteries, 
including AGM.  I've heard the "don't store batteries on concrete" 
theory, but I can't offer any explanation except that the concrete is 
likely to transfer more cold to the battery (I think this is largely an 
"old wives tale"). If you think your AGM is going to experience severe 
cold for any length of time, store it somewhere warmer with a smart 
charger (definitely not a 'trickle' charger).

Bob

On 11/13/2025 11:55 PM, Philip Ethier wrote:
>
>
> On Fri, Nov 14, 2025 at 1:34 AM Philip Ethier <[email-masked]> wrote:
>
>     If you leave a vehicle outside all winter in a cold climate
>     without charging the AGM batteries, will they be ruined by the cold?
>
>     I know that regular lead-acid batteries can freeze up, but I don't
>     know about AGM batteries.
>
>
>     -- 
>     <http://www.mnautox.com/>
>
>
>
> -- 
> <http://www.mnautox.com/>
>
> Donate:http://www.team.net/donate.html
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<!DOCTYPE html>
<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
  </head>
  <body>
    Interesting question. I'm not a hexpert, but I have a lot of cars
    and farm/garden equipment that need batteries--including a new
    EV--so I spend a lot of time thinking about batteries. I have AGMs
    in both my Austin-Healeys; in one because it originally had two 6V
    batteries in parallel and replacements in an appropriate size are
    all but NLA, and in one because they're just flat-ass better (and I
    got tired of neutralizing/cleaning acid spills in the boot--'trunk'
    for you Yankees (:)).<br>
    <br>
    IMO, AGM are better because they seem to generally be better
    constructed, and because the electrolyte--concentrated sulfuric
    acid--is constrained by the fibrous 'mat.' Otherwise, the chemistry
    is the same as any other lead-acid (note 'SLA,' or 'sealed lead
    acid,' aka 'maintenance-free' batteries seem to be generally overall
    quality and I buy them when I can). <br>
    <br>
    Since this question was new to me, I did some digging: <br>
    <br>
<a class="moz-txt-link-freetext" href="https://discoverbattery.com/support/learning-center/battery-101/what-is-the-freezing-point-of-battery-acid-electrolyte">https://discoverbattery.com/support/learning-center/battery-101/what-is-the-freezing-point-of-battery-acid-electrolyte</a><br>
    <br>
    This is something I hadn't known; that the freezing point varies
    with state-of-charge so, first off, if your battery is going to
    endure freezing temps make sure it's fully charged. I have several
    battery minders/tenders, and bought one especially for AGMs, and I
    use them (the tractors sometimes sit for weeks and, when I need
    them, I need them).<br>
    <br>
    Here's another thing I hadn't considered, but I live in the
    California Central Valley and we rarely get below-freezing weather
    (TL;DR: cold weather bad: "Cold weather accelerates wear and tear on
    batteries"):<br>
    <br>
<a class="moz-txt-link-freetext" href="https://www.relionbattery.com/blog/top-4-factors-to-consider-for-a-cold-weather-battery">https://www.relionbattery.com/blog/top-4-factors-to-consider-for-a-cold-weather-battery</a><br>
    <br>
    So, yeah, freezing conditions are not good for lead-acid batteries,
    including AGM.  I've heard the "don't store batteries on concrete"
    theory, but I can't offer any explanation except that the concrete
    is likely to transfer more cold to the battery (I think this is
    largely an "old wives tale"). If you think your AGM is going to
    experience severe cold for any length of time, store it somewhere
    warmer with a smart charger (definitely not a 'trickle' charger).<br>
    <br>
    Bob<br>
    <br>
    <br>
    <br>
    <div class="moz-cite-prefix">On 11/13/2025 11:55 PM, Philip Ethier
      wrote:<br>
    </div>
    <blockquote type="cite"
cite="mid:CAE16_w1NzJJ9c5tVp6h5dUonobioG3i8=[email-masked]">
      <meta http-equiv="content-type" content="text/html; charset=UTF-8">
      <div dir="ltr">
        <div dir="ltr">
          <div dir="ltr">
            <div class="gmail_default" style="font-family:monospace"><br>
            </div>
          </div>
          <br>
          <div class="gmail_quote">
            <div dir="ltr" class="gmail_attr">On Fri, Nov 14, 2025 at
              1:34 AM Philip Ethier &lt;<a
                href="mailto:[email-masked]" target="_blank"
                moz-do-not-send="true" class="moz-txt-link-freetext">[email-masked]</a>&gt;
              wrote:<br>
            </div>
            <blockquote class="gmail_quote"
style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
              <div dir="ltr">
                <div>
                  <div style="font-family:monospace">Absorbed Gas Mat
                    batteries:</div>
                </div>
              </div>
            </blockquote>
            <div><br>
            </div>
            <div class="gmail_default" style="font-family:monospace">OOPS. <span
style="color:inherit;font-size:inherit;font-style:inherit;font-variant-ligatures:inherit;font-variant-caps:inherit;font-weight:inherit;font-family:&quot;Linux Libertine&quot;,Georgia,Times,&quot;Source Serif 4&quot;,serif">Absorbent
                glass mat</span></div>
            <blockquote class="gmail_quote"
style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
              <div dir="ltr">
                <div>
                  <div style="font-family:monospace"><br>
                  </div>
                  <div style="font-family:monospace">If you leave a
                    vehicle outside all winter in a cold climate without
                    charging the AGM batteries, will they be ruined by
                    the cold?</div>
                  <div style="font-family:monospace"><br>
                  </div>
                  <div style="font-family:monospace">I know that regular
                    lead-acid batteries can freeze up, but I don't know
                    about AGM batteries.</div>
                  <br clear="all">
                </div>
                <div><br>
                </div>
                <span class="gmail_signature_prefix">-- </span><br>
                <div dir="ltr" class="gmail_signature">
                  <div dir="ltr">
                    <div dir="ltr">
                      <div dir="ltr">
                        <div dir="ltr">
                          <div><span
style="color:rgb(0,0,0);font-size:12.8px;background-color:rgb(255,255,255)"><font
                                face="monospace">Phil Ethier, West Side,
                                Saint Paul Minnesota, USA</font></span></div>
                          <div><span
style="font-family:monospace;color:rgb(0,0,0)">2006 Gulf Stream Conquest
                              Super C, 8.1, white</span></div>
                          <div><span
style="color:rgb(0,0,0);background-color:rgb(255,255,255)"><font
                                face="monospace">2011 Cayman 2.9 PDK,
                                white</font></span></div>
                          <div><span
style="color:rgb(0,0,0);background-color:rgb(255,255,255)"><font
                                face="monospace">2021 Ford F-150 3500cc
                                twin turbo, white</font></span></div>
                          <div><span
                              style="background-color:rgb(255,255,255)"><font
                                face="monospace">1991 Caterham 1700
                                Super Sprint, not white</font><br
style="color:rgb(0,0,0);font-family:verdana,geneva,lucida,&quot;lucida grande&quot;,arial,helvetica,sans-serif">
                              <a href="http://www.mnautox.com/"
style="color:rgb(0,24,57);font-family:verdana,geneva,lucida,&quot;lucida grande&quot;,arial,helvetica,sans-serif"
                                target="_blank" moz-do-not-send="true">www.mnautox.com<br>
                              </a></span><br>
                          </div>
                        </div>
                      </div>
                    </div>
                  </div>
                </div>
              </div>
            </blockquote>
          </div>
          <div><br clear="all">
          </div>
          <div><br>
          </div>
          <span class="gmail_signature_prefix">-- </span><br>
          <div dir="ltr" class="gmail_signature">
            <div dir="ltr">
              <div dir="ltr">
                <div dir="ltr">
                  <div dir="ltr">
                    <div><span
style="color:rgb(0,0,0);font-size:12.8px;background-color:rgb(255,255,255)"><font
                          face="monospace">Phil Ethier, West Side, Saint
                          Paul Minnesota, USA</font></span></div>
                    <div><span
                        style="font-family:monospace;color:rgb(0,0,0)">2006
                        Gulf Stream Conquest Super C, 8.1, white</span></div>
                    <div><span
style="color:rgb(0,0,0);background-color:rgb(255,255,255)"><font
                          face="monospace">2011 Cayman 2.9 PDK, white</font></span></div>
                    <div><span
style="color:rgb(0,0,0);background-color:rgb(255,255,255)"><font
                          face="monospace">2021 Ford F-150 3500cc twin
                          turbo, white</font></span></div>
                    <div><span style="background-color:rgb(255,255,255)"><font
                          face="monospace">1991 Caterham 1700 Super
                          Sprint, not white</font><br
style="color:rgb(0,0,0);font-family:verdana,geneva,lucida,&quot;lucida grande&quot;,arial,helvetica,sans-serif">
                        <a href="http://www.mnautox.com/"
style="color:rgb(0,24,57);font-family:verdana,geneva,lucida,&quot;lucida grande&quot;,arial,helvetica,sans-serif"
                          target="_blank" moz-do-not-send="true">www.mnautox.com<br>
                        </a></span><br>
                    </div>
                  </div>
                </div>
              </div>
            </div>
          </div>
        </div>
      </div>
      <br>
      <fieldset class="moz-mime-attachment-header"></fieldset>
      <pre wrap="" class="moz-quote-pre">_______________________________________________

<a class="moz-txt-link-abbreviated" href="mailto:[email-masked]">[email-masked]</a>
Archive: <a class="moz-txt-link-freetext" href="http://www.team.net/pipermail/shop-talk">http://www.team.net/pipermail/shop-talk</a> <a class="moz-txt-link-freetext" href="http://autox.team.net/archive">http://autox.team.net/archive</a>

</pre>
    </blockquote>
    <br>
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From: Moose <[email-masked]>
Date: Fri, 14 Nov 2025 10:20:15 -0500 11/14/2025 10:20:28 AM, Serialize complete at 11/14/2025 10:20:28 AM

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Bob ponders...

>"don't store batteries on concrete"

This is one of those things that once were true, but aren't anymore.  I 
think we even talked about it here before.  I watched a good youtube video 
on it.

Turns out that older car batteries used a different type of casing 
material that allows leaching of the chemicals in the batteries (or at 
least of the charge) if it was in contact with the ground for long periods 
of time.  However, since batteries have been made with modern plastics, 
this is no longer the case.  I still don't do it, but mostly because if 
the battery's case cracks or something, I'd rather have wood under it to 
absorb the chemicals than it etching my concrete.

Moose

--=_alternative 0054412A85258D42_=

<font size=2 face="sans-serif">Bob ponders...</font>
<br>
<br><font size=2 face="sans-serif">&gt;</font><font size=3>&quot;don't
store batteries on concrete&quot;</font>
<br>
<br><font size=3>This is one of those things that once were true, but aren't
anymore. &nbsp;I think we even talked about it here before. &nbsp;I watched
a good youtube video on it.</font>
<br>
<br><font size=3>Turns out that older car batteries used a different type
of casing material that allows leaching of the chemicals in the batteries
(or at least of the charge) if it was in contact with the ground for long
periods of time. &nbsp;However, since batteries have been made with modern
plastics, this is no longer the case. &nbsp;I still don't do it, but mostly
because if the battery's case cracks or something, I'd rather have wood
under it to absorb the chemicals than it etching my concrete.</font>
<br>
<br><font size=3>Moose</font>
<br>
<br>
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[email-masked]

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