[RE-wrenches] Outback FXR: Battery voltage exceeds settings

Fri Jul 22 19:49:51 PDT 2022

William,

If the battery cases swelled, they saw over 52 degrees C temps for quite
some time.

While the swelling is usually only cosmetic, what's happening inside is the
negative plates are starting to burn. This is where you will start to lose
capacity and life cycle...  Extended temps of just 35C will half the
overall battery life.

One of the issues with the Outback gear is they only temp compensate at
5mv/Degree/cell. For all the AGM batteries I know of, you need to temp
compensate at 4mv.   In hot temps, this should help, but cold temps could
result in an overcharge.   Did you check the BTS and make sure it was
operating properly?

Another issue is that BTSs are often placed on the top or lug of the
battery,   The top of the battery is about 5-10 deg C cooler than 1/2 way
down the side of the battery, Which will also cause problems with proper
temperature compensation, especially with warmer/colder extremes.

Any kind of sulfation will cause an imbalance when you mix old and new
batteries.   I'm not a fan of mixing any age AGM batteries as there is no
way to tell what the SOC of the old bank vs. the new bank is.   They are
not like flooded batteries; you can check SGs and dissipate heat
much better than AGM or GEL batteries.   I discourage doing this if you
can.   I probably wouldn't have mixed the old and new in the same strings.
This way, you keep the higher resistance batteries in a single string,

Lastly, bunching them together with no spacing between them is very bad.
Batteries should be in a cool, dry environment.  Most battery companies
want to see 1-3 inches in between each battery to allow for effective
cooling. When they are all bunched up together, that is a lot of thermal
mass that doesn't have much chance of cooling.   I have seen two parallel
strings of AGMs take 24-36 hours with no charging or load to drop from 45c
to 25C!

Hope this helps!  Have a good weekend.

<http://www.rollsbattery.com> <http://www.rollsbattery.com>
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On Fri, Jul 22, 2022 at 6:48 PM William Miller via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Friends:
>
>
>
> I maintain a system with 16 AGM L-16 batteries.  Eight were installed in
> September of 2021 and 8 were added in March of 2022.  This is 5 months
> apart.  I have understood that when you install a string of batteries you
> have one year in which to add another string before the first string ages
> to the point it is contraindicated.  When I added the second 8 I put 4 new
> batteries and 4 old batteries in each string.
>
>
>
> About a third of the batteries are discovered to bulging on top.  I assume
> this means the batteries are damaged.  I checked the FXR and Outback
> Extreme Charge controller settings and all were set to absorb at 58.8, and
> float at 55.2, as the manufacturer recommends.
>
>
>
> I downloaded the charge controller log and got 129 days of data.  In that
> log I see 68 days where the batteries exceeded 60 VDC. This is over half
> the days.
>
>
>
> I wonder this:
>
>
>
> 1.   Why did the voltage go up above 58.8 on so many days even though it
> was set at 58.8. (I set the EQ voltage at 58.8 just in case, but EQ was
> never engaged.)
>
> 2.   Did the excess voltage damage the batteries?
>
> Any input is appreciated.
>
>
>
> Sincerely,
>
>
>
> William Miller
>
>
>
> Miller Solar
>
> 17395 Oak Road, Atascadero, CA 93422
>
> 805-438-5600
>
> www.millersolar.com
>
> CA Lic. 773985
>
>
>
>
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