Small battery for 3 lights and fan-tastic?

[PitterPatter]

I'm building a 4x8 camper and wonder if I can get away with a smaller (ie. wheelchair) battery as I will only be running 3 LED lights (2 hrs daily?) and fan nightly for weekend trips.

I'm trying to be economical with these considerations:
-Weight/size
-Price
-Resources

As I said, most of our trips will be weekenders, and if we went on any longer trips I'd probably add a solar panel to keep it charged.
Can anyone suggest a smaller battery for a simple system like this? Could a wheelchair battery suffice?

Thanks!

[TimC]

With just the fan running on high speed you will need an 80 ahr battery to enjoy 20 hours of hi speed breeze. The lights are likely less than 1 aHr combined which at two hours is negligible. Do some looking at amperage draw on your lights to determine if they pull higher amps. A fantastic fan is said to use 1.9a on high speed.

So two nights with the fan running 10 hours, or three nights of just over six hours will require at least an 80 ahr battery (40 aHr usable). A small solar panel (50w) on a sunny day would help restore each night's power usage and assure you have enough to make the weekend.

I use Mighty Max 18 ahr batteries (currently eight of them). They are small and easy to find space to hide them. They cost a bit more per aHr than a single battery of higher ahr. One of those will definitely not work for you. Two might if you have a recharge method each day. Whatever you do think about long term needs. Start charging phones and tablets and you may be in the dark.

[noseoil]

A wheel chair battery would be fine. My rule of thumb for charging with solar on a trailer is 1 watt of charge per AH of battery storage (completely arbitrary number on my part, not an electrical engineer, it just works well). A good wheel chair battery (35 AH-AGM) will last about 5 years in this situation & be plenty for your power draw. A solar panel of 35 or 40 watts will be good for your needs.

We run a 100 AH battery & 100 watt solar panel. It powers a fan, lights, stereo, TV & sound bar, inverter in the galley for the coffee grinder, charging ports, etc. After 6 years we need to replace the battery, but the system is fine for our needs.

[Sparksalot]

I have a 35Ah battery in Rose. Fantastic fan, 2 porch lights, 2 cabin lights and several usb outlets. I run the lights just a few minutes on occasion. The fan on low for maybe 5 minutes to help purge the cabin.

[S. Heisley]

Your LED lights should not be a problem. LED light bulbs have come a long way in the last decade and are truly wonderful. My bulbs use .18 Amps per hour. When you write LED "lights" You may mean light fixtures. So, if your light fixtures have 2 LED light bulbs in each and assuming your LED "bulbs" use .18 Amps per hour, you are using .36 Amps per hour per fixture. From that assumption, we'll guess that you are using a little over 1 full Amp per hour (1.08) if all your lights are on. If you think you will be using them for 2 hours. that would be 2.16 Amps per day and around 6 & 1/2 Amps (6.54)for lighting for a 3 day weekend. (Double check me. I did this in my head.)

Using the fan all night is not as good nor as easy. Again, without knowing what fan you are using. I am guessing. Plus, there are two speeds (or more?) to a fan. I found this information on a Fantastic Fan:

How long will fantastic fan run on battery?
22.85 hours
Using kpic's number of 1.86 amps per hour for the fan on low and using 85 amp hours for a typical Group 24 battery, we can calculate that you'd be able to run the fan 22.85 hours. At that point the battery would be discharged 50% and should be recharged.

Now, let's take that 1.86 Amps per hour (on low) and multiply it by 8 hours. That would be almost 15 Amps (14.88) while you sleep 1 night. On a 3 day weekend, assuming 2 nights, that would be nearly 30 Amps! 3 nights would be close to 45 Amps!

Now, let's try cutting that fan usage by getting one of those clip-on oscillating trucker fans. I got mine a the local drug store for about $15 and it uses .9 amps per hour. If I use that for 8 hours for 1 night, that's 7.2 Amps and for 3 nights, 21.6 Amps and cut that fan Amp usage in half!

Again, please double check all these calculations as I did them all in my head, sitting at the window without benefit of any lights on and it's starting to get dark.

One more thing....Notice that in the quoted area, it says you should not deplete your battery by more than half. I'll agree that you should never exhaust your battery as it will likely damage it and shorten it's life but I feel you can discharge your battery 70%. However, using a 50% calculation leaves some room for errors.

By the way, I use a 55 Amp AGM battery and it weighs 38 pounds. I have 6 LED fixtures but 9 LED lights plus 1 CFL fixture (2 tubes) that I have yet to modify to LED. I don't have an overhead fan but I do have that oscillating trucker fan (which I love).

[saltydawg]

My bet is you wont use the fan even on low, they are sized for full sized trailers. As was said you will use it to suck the hot air out, then just leave it open. If you think you will want constant airflow look up the thread here "slowing down a fantastic fan" it uses a pwm speed controller to make it even slower, and uses less power. The other option as was stated is a clip on fan.

Next I am a firm believer in lifepo4 battery, a 60 amp hour battery that is usable down to 10% discharge with no damage is 14 lbs. Or go even smaller with a 30 ah battery, and put a 100 watt renogy panel on the roof and stay out forever. Yes lifepo4 batteries are a buy once cry once price but they will out last lead batteries esp if you over discharge them.

[ebis]

Check out the 10 speed maxxair maxxfans. According to a review at faroutside.com, the fan draws 0.1 amps at the lowest speed and 2.8 amps at the highest speed. Options like lights, remote, rain sensor, thermostat and motorized opening will increase the power needed. BTW Maxxair uses pwm to control the fans speeds. Ask me in a few months on how well it works.

[featherliteCT1]

I have Maxxfan. Below summarizes the actual amps drawn at the indicated fan speeds, measured with my shunt based battery monitor.

Screen Shot 2021-05-26 at 8.19.02 PM.jpg (30.2 KiB) Viewed 1302 times

[Tom&Shelly]

I have Maxxfan. Below summarizes the actual amps drawn at the indicated fan speeds, measured with my shunt based battery monitor.

Screen Shot 2021-05-26 at 8.19.02 PM.jpg

Mine are similar (measured with a DC clamp-on ammeter):

0.05 A
0.15
0.2
0.4
0.5
0.7
1.0
1.35
1.80
2.65

It's a no-frills MaxxFan--no temperature or rain sensor.

After two spring trips in New Mexico and Arizona, I think we only ran it for a few minutes one night on one of the lower settings. The roof vent is the main thing.

Tom

[featherliteCT1]

My fan is also a no-frills MaxxFan--no temperature or rain sensor. In my setup, I consider it to be a relatively high amp draw item.

[tony.latham]

...and fan nightly for weekend trips.

Where will you be camping? I can recall running our fan once. Maybe twice last summer.



We certainly didn't run it on our near-month-long spring trip.



But we're generally in the middle of Idaho or western Montana.

Tony