Solar Generator Output with a Battery Tender

[39Tudor]

I purchased the 1200 watt solar power station from Harbor Freight to use in a detached storage building that does not and probably never will have power supplied from the grid. Currently the only thing on the power station is a battery tender jr. The power consumption listed on the battery tender is 750mw.

When I turn on the power station, the battery tender will fire up and will draw power off the power station until the indicator goes solid green. Once it reaches that point, it will run for about 30 minutes and then the power station will shut down. Prior to shutdown , the output meter on the power station will read between 0 and 3 watts.

I suspect that the draw from the battery tender is so small that the power station does not sense the load and shuts down. Could I purchase a LED night light and plug it into one of the power station outlets to keep enough current draw to keep the power station alive.

Appreciate any advise you guys may have to offer.

 

[jlv03]

What's the goal here? If you plan on running the battery tender beyond a few hours, the idle consumption of the inverter will drain the power station in about a day.

 

[mm08822]

From the manual:
6. The Power Station will shut off automatically if unused. It will shut off after 1 hour for AC or DC output modes, or after 2 hours for USB output mode.

You need to call HF Tech services and find out what is the cut-off threshold (Good luck with them! Not sure what they might have for product knowledge)
For technical questions, please call 1-800-444-3353.

Might be easier to just try known loads and find the answer yourself.

 

[mm08822]

What's the goal here? If you plan on running the battery tender beyond a few hours, the idle consumption of the inverter will drain the power station in about a day.

8. The Power Station will consume some power from the battery while on, even without loads attached. Turn Power Station off after use.

No mention of idle power draw amount.

 

[39Tudor]

I tested my plan with a different battery maintainer, Schumacher brand and i was able to plug it into the power station and could get 3 days of run time at 8 watts output. I had 10% capacity after 3 days. I carried the power station back to my shop and it was fully recharged by AC power in about 90 minutes.

Eventually I would like to mount a solar panel to use for recharging the system.

At no time with this maintainer did the power station go to sleep or shut off like it does with the Battery Tender Jr.

 

[dscheidt]

It sounds like the battery tender jr is detecting that the battery doesn't need attention and going to sleep, expecting to wake up in a while and check again. The battery back sees the draw is below its threshold, so it turns itself off. Then the BT Jr can't wake up and tend to the battery. The other charger probably had a higher standby draw (maybe because it was always pumping current through the battery, maybe because the idle circuitry is inefficient.)

What you need is a battery tender intended to run off a battery, or a power pack that has a lower threshold current, or one that can be told to wake up periodically and turn the outlets on, even if it doesn't see a load yet. I don't know if any of those are things, but I do doubt you're the only person who's tried to do this sort of thing, so maybe they do. There are 12v battery maintainers that are directly powered by solar, they're pretty commonly used on construction equipment, boats, and other things that sit for long periods, often where it's impractical to plug a regular charger in. Would that work for you?

 

[39Tudor]

@dscheidt Thanks for the suggestion. Just browsed thru “The Jungle” and there are a lot of inexpensive solar battery maintainers available. I’ll go out later today and get the specs off the Schumacher maintainer.

 

[mike93lx]

Just plug the charger for the battery pack into the battery pack. Besides unlocking infinite power , it will probably keep it awake

 

[theoldwizard1]

I tested my plan with a different battery maintainer, Schumacher brand and i was able to plug it into the power station and could get 3 days of run time at 8 watts output.

I don't have any scientific proof, but ...

For long term storage, I always connect a battery charger to an old fashioned, mechanical lamp timer. I set it to only turn on the charger for about 4 hours per day. My experience is that batteries, regardless of their chemistry, live longer if they are NOT constantly being charged.

 

[dave*99]

I don't have any scientific proof, but ...

For long term storage, I always connect a battery charger to an old fashioned, mechanical lamp timer. I set it to only turn on the charger for about 4 hours per day. My experience is that batteries, regardless of their chemistry, live longer if they are NOT constantly being charged.

Today's modern smart chargers control the charge automatically by going into a float mode. Float mode can vary from one charger design to another. No need for a timer with these units.

Watch some Youtube videos on NOCO Genius chargers to learn more.

 

[theoldwizard1]

Today's modern smart chargers control the charge automatically by going into a float mode. Float mode can vary from one charger design to another. No need for a timer with these units.

No "float" mode ! OFF !

I have a small battery operated vacuum. The charger "wakes up" (the light comes on), checks the battery state of charge, turns off and goes to sleep for 5-10 minutes. Other people have done the lamp timer trick on lead acid batteries used to auto start generators. With a typical automatic/float charger, the battery lasts 1 - 2 years. With the lamp timer 2 - 4 years.

 

[dave*99]

No "float" mode ! OFF !

I have a small battery operated vacuum. The charger "wakes up" (the light comes on), checks the battery state of charge, turns off and goes to sleep for 5-10 minutes. Other people have done the lamp timer trick on lead acid batteries used to auto start generators. With a typical automatic/float charger, the battery lasts 1 - 2 years. With the lamp timer 2 - 4 years.

Again, you have to understand the latest float technology.