[RE-wrenches] battery vent control for lead acid

Tue Jun 3 19:11:08 PDT 2025

Hey Wrenches...

It's not a good idea to run this based on temperature...    You want the
fan to come on when the batteries are gassing. If the battery temperature
is cold and they are charging, it could still be gassing.  This would
result in the fan not running and potentially lead to hydrogen ignition.
Typically, you turn the fan on at or just above float voltage, and it runs
until the voltage falls .2 to .4 volts below the float voltage.

You want the fan to be sealed and brushless so that there is no chance that
it'll ignite the hydrogen being expelled from the box. If the fan is sealed
like the zephyr fans, it won't corrode.

If you are tying a Sol Ark inverter to a lead-acid bank, it's a good idea
to contact Sol Ark and have them push the firmware that allows you to
adjust the tail current time.     With their tail current set to only 10
mins and no way to program absorb timers, this will result in
chronically undercharged FLA/AGM or GEL batteries.

You should use the EQ V, EQ Time, and EQ Frequency to simulate a normal
bulk/absorb timer...   Depending solely on the tail current for the time of
every charge cycle will result in undercharging issues.  Typically, the EQ
frequency is set from 2-7 days for full-time systems or 14 to 30 days for
backup or lightly loaded systems.

Another thing to keep in mind is that they utilize the battery's internal
resistance to increase charging voltage and current, which is supposed to
help break up sulfation. From my experience, this cooks the battery. The
issue with this is that it's not temperature-compensated.    I would defeat
this by setting the internal resistance to 0 or 1 mΩ.    What happens here
is that if the measured internal resistance is higher than programmed,
it'll bump up the voltage and current to lower that resistance.  If the
battery is already sulfated, it'll become so hot that it'll gas very
quickly. Alternatively, if it's an AGM or GEL battery, it'll cook the
battery electrolyte, causing the bank to dry out, swell, and fail.   In the
past, I have seen them charge at over 66 volts. Since disabling this, I
have not seen the Sol Arks do this.

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On Tue, Jun 3, 2025 at 6:47 PM Jay via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> It’s a good idea to go with ac fan.
> Simple and easy
> And there isn’t any charging if the inverter goes down.
> Jay
>
>
> On Jun 3, 2025, at 3:52 PM, Jerry Shafer via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
> 
>
> Wrenches, Dave,
>
> I have had success with CPU fans, 12,24,48 vdc, 120 vac use no power and
> run them through a thermostat set at 80 to 90 degrees
>
> Fun times
>
> On Tue, Jun 3, 2025, 1:30 PM Roy Butler via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
>> Dave,
>>
>> The Morningstar Relay Driver can work as a stand alone unit, it can
>> derive it's power from the battery bank.
>> This allows it to be programmed for voltage based relay operation which
>> is ideal for vent fan applications.
>>
>> The relay channels are dry contacts and have a current limit of 750mA.
>> This will run a fan somewhat larger
>> than the good old Zephyr vents.
>>
>> Roy Butler
>> Four Winds Renewable Energy, LLC8902 Route 46 <https://www.google.com/maps/search/8902+Route+46?entry=gmail&source=g>, Arkport, NY 14807
>> 607-324-9747
>>
>> Education is when you read the fine print; experience is what you get when you don’t.
>>
>> “The less people know, the more stubbornly they know it.”
>>
>> Although no trees were killed in the sending of this message,
>> a large number of electrons were terribly inconvenienced.
>>
>>
>>
>> On 6/3/2025 2:22 PM, Dave Tedeyan via RE-wrenches wrote:
>>
>> Hi all,
>>
>> What are people using these days for venting a good ol' 48v flooded lead
>> acid battery box? I am upgrading an off grid system. There is a one year
>> old set of flooded lead acid batteries, so those will stay, but everything
>> else will be new. I plan on using a Sol-Ark inverter. The existing battery
>> box does not have any active ventilation, so I would like to add some. In
>> the past, I have used the Zephyr Power Vent Fans, like this one:
>>
>> https://www.thesolarbiz.com/zephyr-power-vent-fan-for-48-volt-battery-systems.html
>> They don't seem readily available, but I think I can find one somewhere.
>>
>> More importantly, what would you use to control this? Sol-Ark inverters
>> do not have any kind of relay for it. I have found external controllers in
>> the past (Yandina LLC Vent Control), but I cannot seem to find any right
>> now. There is one noted in the fan documentation (Solar Converters,
>> Inc. VCS1AH), but that does not seem available anywhere right now. Does
>> anyone have a recommendation for either a vent fa controller or a whole
>> venting solution?
>>
>> Thanks!
>> -Dave
>> --
>>
>> [image: Logo] <https://www.sungineersolar.com/>
>> Dave Tedeyan, P.E.
>> Owner | Sungineer Solar
>> p: he | him | his
>> a: 1653 Slaterville Rd.
>> <https://www.google.com/maps/search/1653+Slaterville+Rd.+%C2%A0+%7C%C2%A0Ithaca,+NY+14850?entry=gmail&source=g>
>>
>> <https://www.google.com/maps/search/1653+Slaterville+Rd.+%C2%A0+%7C%C2%A0Ithaca,+NY+14850?entry=gmail&source=g>| Ithaca,
>> NY 14850
>> <https://www.google.com/maps/search/1653+Slaterville+Rd.+%C2%A0+%7C%C2%A0Ithaca,+NY+14850?entry=gmail&source=g>
>> w: www.sungineersolar.com <http://www.sungineersolar.com/>
>> c: (607) 270-0370
>>
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