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Author Topic: Solar Panel Battery Charge Ventilation  (Read 319 times)

JeffVolp

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Solar Panel Battery Charge Ventilation
« on: April 29, 2021, 12:19:08 PM »

I'm presently using X10 to control an exhaust fan for a solar panel battery bank. Presently that fan runs during most daylight hours, but it only has to run when the batteries are actually charging.

I'm going to design a voltage monitor that just turns on the fan when the batteries are charging.  Monitoring battery voltage, it will close a relay when the voltage begins to increase and open it a few minutes after the voltage begins to decrease.  A threshold setting will prevent the fan from turning on as the batteries recover after the inverter shuts off at the discharge limit.

I was going to do a one-off for myself, but I wonder if there is any interest from others with solar systems.  It would work on 12V, 24V, and 48V systems, and possibly provide 12V fan power from the battery voltage.

Jeff
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Tuicemen

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Re: Solar Panel Battery Charge Ventilation
« Reply #1 on: April 29, 2021, 02:30:54 PM »

Although my 24v system has a 12v fan currently attached to an Outback charge controller which does this, I'd be intrested. Since I have 3 chargers not including the back up generator the fan isn't always on when it should be.
 I had thought of increasing my exhaust pipe size and adding another fan to the other charger's. But monitoring voltage at the batteries would simplify things.
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JeffVolp

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Re: Solar Panel Battery Charge Ventilation
« Reply #2 on: April 29, 2021, 04:04:10 PM »

So there may be interest from others.

Thanks.

Jeff
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Tuicemen

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Re: Solar Panel Battery Charge Ventilation
« Reply #3 on: May 02, 2021, 07:47:22 AM »

I suspect there may not be much interest from users on this forum. However I would expect more interest from users on alternative energy forums using flooded batteries.
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JeffVolp

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Re: Solar Panel Battery Charge Ventilation
« Reply #4 on: May 03, 2021, 12:05:12 AM »

I suspect there may not be much interest from users on this forum. However I would expect more interest from users on alternative energy forums using flooded batteries.

Yes, I will pursue that down the road.  Rather than just modifying an EEU board for myself, I ordered some prototype boards.  I hope to have a small batch ready in the summer.  It will run from 12V to 60V, and will provide either its own switched 12VDC (.5A max) or control power supplied from an external source.

It will be in a Polycase LP-21F case.

Jeff
« Last Edit: May 03, 2021, 01:24:38 PM by JeffVolp »
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Re: Solar Panel Battery Charge Ventilation
« Reply #5 on: May 03, 2021, 07:26:36 AM »

Sounds awesome.
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toasterking

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Re: Solar Panel Battery Charge Ventilation
« Reply #6 on: May 03, 2021, 02:09:09 PM »

Warning: n00b response here.

I don't have a solar power system (yet), but I've been thinking about connecting marine deep cycle batteries to a UPS and am curious how much venting is required for something like that, if any.

Jeff, I know you had two incidents in which such batteries exploded and finally moved them into a (probably loosely sealed) plastic container to prevent a big mess again, should the scenario repeat.  What kind of venting arrangement is required for a configuration like that?
« Last Edit: May 03, 2021, 02:11:20 PM by toasterking »
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JeffVolp

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Re: Solar Panel Battery Charge Ventilation
« Reply #7 on: May 04, 2021, 12:54:00 PM »

Jeff, I know you had two incidents in which such batteries exploded and finally moved them into a (probably loosely sealed) plastic container to prevent a big mess again, should the scenario repeat.  What kind of venting arrangement is required for a configuration like that?

You are exactly right about those two "incidents".  And yes, the batteries are now in a plastic bin to contain the acid should it ever happen again.

In my case I believe the APC UPS was actually overcharging the batteries, releasing hydrogen gas.  I had to top them up every few months to replace water loss.  That same battery bank is now being used for solar panel storage.  I had topped them up when I put them into service last fall, and so far the electrolyte levels have not dropped.  So I believe the MPPT charge controller is doing a much better job maintaining the batteries than the APC UPS.  But it could be that there is not enough surplus energy to fully charge them.  Anyway, maybe venting was actually more important when using the UPS than with the solar charge controller.

For venting, I attached a small 3" vent fan to the lid of the battery bin, and 2" plastic drain pipe to exhaust any gases out of the room.  A rubber coupler went from the fan to the drain pipe.

https://www.ebay.com/itm/353329404796?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

I reduced the voltage to 9V to slow it down a bit, but there is still plenty of airflow to eliminate any odor escaping from the battery enclosure.

Right now I have X10 turning that fan on an hour after sunrise and off an hour before sunset.  While that ensures it is running whenever the batteries could be charging, we are often consuming all the energy our "emergency" panels are generating.  That will be especially true over the summer with the A/C load.

Jeff
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toasterking

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Re: Solar Panel Battery Charge Ventilation
« Reply #8 on: May 06, 2021, 03:55:22 PM »

In my case I believe the APC UPS was actually overcharging the batteries, releasing hydrogen gas.  I had to top them up every few months to replace water loss.  [...]  Anyway, maybe venting was actually more important when using the UPS than with the solar charge controller.
Good catch.  I'll make a note to keep tabs on the charging voltage if I do the UPS mod.

For venting, I attached a small 3" vent fan to the lid of the battery bin, and 2" plastic drain pipe to exhaust any gases out of the room.  A rubber coupler went from the fan to the drain pipe.
Clever implementation!  That airflow booster fan holder thingy is neat.  I knew those existed but wouldn't have thought to use one for something like that.  Is the room housing your batteries below ground or above ground?  How do you duct the exhaust to the outside?

Thanks!

P.S.  Your new WordPress site looks really nice.
« Last Edit: May 06, 2021, 03:57:56 PM by toasterking »
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Brian H

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Re: Solar Panel Battery Charge Ventilation
« Reply #9 on: May 06, 2021, 04:14:41 PM »

APC has stated. Their UPS units are calibrated for sealed lead acid batteries. Of the AH rating they are designed for. Anything else can sometimes lead to issues.
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JeffVolp

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Re: Solar Panel Battery Charge Ventilation
« Reply #10 on: May 06, 2021, 05:40:22 PM »

For venting, I attached a small 3" vent fan to the lid of the battery bin, and 2" plastic drain pipe to exhaust any gases out of the room.  A rubber coupler went from the fan to the drain pipe.
Clever implementation!  That airflow booster fan holder thingy is neat.  I knew those existed but wouldn't have thought to use one for something like that.  Is the room housing your batteries below ground or above ground?  How do you duct the exhaust to the outside?

Walk-out ground level.  The builder installed a 2" PVC pipe up to the attic to provide an easy run for future wiring.  I tied into that to vent outside.

Thanks for the feedback on the updated website.  It was to make it more compatible with cellphones.

Jeff
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toasterking

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Re: Solar Panel Battery Charge Ventilation
« Reply #11 on: May 08, 2021, 12:45:50 PM »

APC has stated. Their UPS units are calibrated for sealed lead acid batteries. Of the AH rating they are designed for. Anything else can sometimes lead to issues.
It gets worse.  From what I've seen, that "calibration" can be a very weak effort at best!  The APC Back-UPS 1250 I am using on the PC I am typing this on uses an LM7815 to regulate to 15V and then two 1N4005 in series to drop the voltage to ~13.6-13.8.  If one of those two diodes deviates from spec, there is no feedback and no correction.  If I replace the SLA batteries with unsealed deep cycle batteries, I may modify this "charging" circuit also or modify it to switch a "smarter" lead acid charger in-circuit for charging.
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