[RE-wrenches] Suspect MX 60

Tue Nov 18 10:03:11 PST 2014

Hi:

This may not be the problem, but I wanted to bring it up as I have heard 
of a few cases of battery boiling issues with various charge controllers 
and want to suggest a possible cause.

I'll do this point form.  It's easier to describe it that way:

1. Solar charge controllers are programmed to go to bulk charge in the 
morning.
2. The intensity of the sunlight starts off low in the morning and 
depending on the weather during the day, the intensity can reach any level 
between virtually 0% and 100%.
3. The exit criteria for bulk is that the battery voltage reaches the 
Vbulk/abs volts setting or a bulk/abs timer times out.
4. If the sunlight conditions are just right to keep the charging voltage 
just below the Vbulk/abs setpoint, the exit from bulk/abs will be the 
timer.
5. Bulk/Abs timers are usually set for rather a long time, many hours is 
not uncommon.
6. Given the above, it is possible that the battery stays at gassing 
voltages for many hours every day at certain times of the year when the 
sunlight intensity is just right to support that.
7. As a consequence the boiling problem will show up only at particular 
sites, particular battery/charge controller sizes and particular times of 
year.

Again, I am not suggesting that this is necessarily the cause of battery 
"boiling" in systems with solar charge controllers, but it could be a 
reason.

2nd ps.  All manufacturers do precise battery voltage/current measurements 
on the bench with a wide variety of conditions, but we will never be able 
to simulate the 1000's of conditions that happen on the 1000's of installs 
out there.  With that in mind, on-site battery voltage/current data 
logging is a very powerful tool when investigating these kinds of issues.

JARMO
_____________________________________________________________________________________ 

Jarmo Venalainen  |   Schneider Electric   |  Solar Business  |   CANADA | 
  Training & Development Specialist - Senior 
Phone: +604-422-2528  |   Fax: +604-420-1591  |   Mobile: +604-505-0291 
Email: jarmo.venalainen at schneider-electric.com  |   Site: www.SEsolar.com 
|   Address: 3700 Gilmore Way, Burnaby, BC V5G4M1 

*** Please consider the environment before printing this e-mail 

From:
Drake <drake.chamberlin at redwoodalliance.org>
To:
RE-wrenches <re-wrenches at lists.re-wrenches.org>, 
Date:
11/18/2014 09:15 AM
Subject:
[RE-wrenches] Suspect MX 60
Sent by:
"RE-wrenches" <re-wrenches-bounces at lists.re-wrenches.org>

Hello Wrenches,

An MX 60 boiled a 24 volt bank of 4 Trojan L-16 batteries last summer. The 
batteries all checked out to be in good shape. It is not totally clear 
that the CC was not set to auto equalize, but the EQ voltage was only set 
at 31.0 V. 

The battery bank has been replaced by 8 Full River L-16 AGM batteries. The 
parameters have all been reset for AGM with EQ disabled. The homeowners 
are concerned that the charge control may not work, and damage their new 
battery bank. 

If there is a problem with the CC, it is very intermittent. Has anyone 
ever seen an intermittent MX 60? 

Outback tech support says if we send it in they will update the firmware 
for $90, and do a 24 hour bench test. It appears that the firmware update 
will not do anything useful for this off grid system. There are no new 
boards available for this unit. I'm not sure if the bench test will show 
up an intermittent problem. 

Has anyone had this situation before?  Would it be better to: 
Replace the CC 
Send the CC to Outback 
Do nothing 
Thank you,

Drake 

Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV 
740-448-7328
http://athens-electric.com/ 

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