How should I power my fantastic fan?

[Kenny P]

Hi. I have a fantastic fan installed on my van.
In the winter I literally only need to run the fan 3 minutes once a day (I enjoy a cigarette before bed).
I have a feeling running some wires from my vans battery would do the trick and my battery would have more than enough juice for 3 minutes of fan time a day.
But I’m also looking toward the summer in 5-6 months... I’ll want to run the fan ALL NIGHT.
I don’t want to do solar, I really don’t. I live very simply and I’m never “home”, so I don’t have a big need for power.
What if I upgraded to a top-of-the-line starter battery for my van, could i run a fantastic fan off that all night without killing the battery?
I know all of you electrical engineers will tell me I need to know the amp pull of my fan and the amp hours of my battery before determining this... but this is just more of a general what-if question.
Thank you.

 

[TMG51]

The best answer to your question is, "solar." But you don't want solar. So here's a simplistic non-solar answer.

If you are not going to have a means of charging a separate deep cycle battery bank, then replace your engine battery with the highest amp hour marine battery you can find (not a starter battery). A marine battery is halfway in between a starter battery and a deep cycle battery. It does both, just neither as well as the other does independently.

Add to your new marine battery a voltage disconnect safety, such that if you run your fan at night and it drains the battery too much, it will cut off while you're asleep and not leave you with a dead battery in the morning.

That's the only simple answer I can think of.

 

[B and C]

What TMG51 said. This assumes you are driving everyday or have another way to charge it everyday. I would also add to your kit one of those little jump start packs since you only have one battery doing dual duty.

 

[John61CT]

They do consume a fair bit left on for long periods, as much as an efficient fridge.

So no, if you tried to do with even a topnotch single battery, you'd need to jump start sometimes,

and driving less than 5-6 hours a day won't get the batt back to full, same with a gennie.

So you must have solar, or access to shore power overnight at least a few nights per week,

and put in a pair of GC2s to tide you over between, keep your Starter batt dedicated as is.

 

[MrAlvinDude]

So a trial-and-error experiment.  Things that might happen during the experiment:

a) you buy a bigger battery, and it turns out that it is big enough to run the fan for the required time, and you can still start your van, and the amount of daily driving turns out to be enough to charge up the battery every day. And all is good.

b) And all is good - for a long time, but then suddenly one day.... the battery was not charged as much as usual, or is getting older and can no longer be charged as much - and you will need to get a jumpstart. 


c) the battery is big enough to run the fan, and still be able to start the van, but your daily drive is too short to fully charge the battery, so after some time, you will need to get a jumpstart.

d) the battery is big enough to run the fan, but not big enough to start the van, and you will need a jumpstart


If you get a battery monitor, that can turn off the fan, when the voltage reaches a certain low, you will avoid the need for the jumpstarts. 


For all the options not being a), you get a second chance to think of  new solutions and what to buy, so you can make one more trial-and-error experiment.

 

[Trebor English]

What if I upgraded to a top-of-the-line starter battery for my van, could i run a fantastic fan off that all night without killing the battery?
I know all of you electrical engineers will tell me I need to know the amp pull of my fan and the amp hours of my battery before determining this... but this is just more of a general what-if question.
Thank you.

Generally, what if, yes.  It is possible.  When my minivan starter battery got to the end of the warranty period and died I replaced it with the biggest battery that would fit in the original location.  I got a group size 24.  There's a bunch of batteries available that size.  I got the one with the most weight, the most amp hours, and the least cranking amps.  

Ford recommends a group size 59 for my minivan.  That's $100.  The trolling motor battery I got was $80.  A "top-of-the-line starter battery" sounds like the most expensive battery of the wrong kind.  Comparing the Ford recommended starter battery with the one I got, the starter battery has a reserve capacity rating that is much lower, much lower weight, more cranking amps.  For charging phones, running the MaxxFan, powering LED lights, etc, the starter battery is all wrong.  More weight means more lead.  Less cranking amps means less porous plate material.  

I know that the battery I got has a sticker that says it is a deep cycle battery.  Really what is inside these batteries is highly suspect.  Golf cart batteries really are deep cycle batteries and are 2 or 3 inches taller than the one I got.  The 50% maximum discharge recommendation applies to deep cycle batteries.  For starter batteries my experience is that if you limit cycling to 5% of the capacity based on reserve capacity minutes the battery life isn't substantially reduced.  With a 12 volt alleged deep cycle battery I expect to get similar service life keeping the discharges to 10% typical and 25% max.  The very long charging times typical of deeply discharged lead acid batteries don't really apply if you limit the discharge to 5% or 10%.  If you start charging at 95% it won't take 6 hours of driving.

My MaxxFan uses less than 3/4 amp on the middle speed.  That's 6 amp hours over an 8 hour period.  My 75 amp hour battery at 10% is 7.5 amp hours.  That will work, not damage the battery, and still leave enough to start the engine.  North Dakota in January might be a problem.  Doing this will require driving daily.  I don't run my fan all night.  To avoid having to drive every 2 or 3 days I got a 100 watt solar panel.  A couple of 2 amp hour phone charges and an hour of fan running is about all I ever did to the battery before solar.

Before I got this flooded lead acid battery the one I had was a sealed maintenance free starter battery, a real porous plate high cold cranking amp starter battery.  There was calcium in the lead alloy so it didn't waste much water.  It died.  It lasted to the end of the warranty period.  It was a starter battery and it died.  I am presuming that with this battery it too will die.  Since I have solar now I might be able to wait until 2 PM and with a fresh charge it might start one more time.  I didn't carry a lithium jump starter before and still don't.  I have never had the battery get over discharged and fail to start the engine.

This battery doesn't have calcium in the lead alloy.  It uses water.  It takes 20 to 30 ml per cell per month.  Being a bit retentive I do keep a record for each cell.  This could give me a warning of an impending failure.  Since it uses water it gives hope that it isn't just a different sticker on a plain starter battery.  Being not sealed I use a hydrometer monthly when I check the water.  Ten minutes per month isn't onerous but it isn't optional.  

My minivan is small.  If someone gave me a pair of golf cart batteries I don't know where I would put them.  

My use of electricity is low.  I have been doing this since September 2016 and never needed a jump start.  It can be done.  Just don't run your battery down.  It is bad for batteries to do that.  Measure the current used by everything.  My van has a terrible load with everything off so I use a disconnect switch.  Know the current of everything including when off.  I had an inverter that used the same on or off.  No load it was low but far from zero.  When you connect the van to the battery expect the surge to blow the fuse in your amp meter.  That's no excuse.  You need to know how much current everything takes.

 

[DLTooley]

Small solar panels can function without a controller, so long as you are only using trickle charger amps for your loads. A smaller portable folding panel might also do the trick. I'm thinking 10-15 watts, but you'll want to do your own math on both ends.