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Old 02-27-2024, 08:17 AM   #1
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Smallest AH Battery You Can Use?

The vast majority of our camping is with electric hookups. Twice a year we camp without any hookups for a week. I donít see a need to carry all the extra battery weight all year round for the two times a year we need it so I was thinking about building a separate battery box with an inverter that I would only break out for those two trips.

I swapped all our lights for led. What would be the minimum ah battery I would need when simply using the camper while plugged in?
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Old 02-27-2024, 09:28 AM   #2
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Thoughts to your question.

You really don't even need a battery if you are plugged in but you do need a battery while towing so your emergency brake-away brakes will work if the trailer gets disconnected from the truck. So with that, you could get by with the smallest deep cycle battery you can find which is usually a group 24 and less than $100.00

However, it only cost a little more comparatively speaking to get the larger deep cycle battery even though it is heavier and cost a little more, but buying the larger deep cycle battery would be more cost effective than buying the smallest for when you don't need a battery and then another larger one for when you do.

Perhaps a 100ah LifePo4 would work for both purposes and they weigh only around 30 lbs. ~CA
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Old 02-27-2024, 09:30 AM   #3
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Do you plan on running a refrigerator, radio/audio, or anything other than a nightlight?

You need 12 volts to run you fridge on propane.
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Old 02-27-2024, 10:22 AM   #4
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Very hard question to answer.

1st you do need a battery for the e-brake system. Most transporters I've meet use a small sealed battery I think 12 amh about the size of a motorcycle battery.

That battery will work for every day travels, but you will not get much run time for a frig or lights if you loose your shore power.

Lithium batteries are expensive need a special charger. You can get about 70-80% of the amps out of them, compared to a LA.
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Old 02-27-2024, 10:55 AM   #5
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Very hard question to answer.

1st you do need a battery for the e-brake system. Most transporters I've meet use a small sealed battery I think 12 amh about the size of a motorcycle battery.

That battery will work for every day travels, but you will not get much run time for a frig or lights if you loose your shore power.

Lithium batteries are expensive need a special charger. You can get about 70-80% of the amps out of them, compared to a LA.
I think perhaps you misstated what you meant. You can get 100% of the amps out of a LifePo4 battery without damaging the battery compared to what most battery mfgrs state should be the max draw down of a Lead Acid battery (50%) although many people state you can pull a LA down to 70~80% without damage as long as you recharge it shortly after drawing it down.

Also, you don't need a special charger, although having one is "optimal". I have recently purchased a LifePo4 charger off of Ebay for $23.99 10 amps and free shipping and currently have a 100a LifePo4 battery in my RV without having a converter specifically designed for LifePo4 (just a LA converter).

Also, LifePo4 batteries have come way down in price, you can now purchase a no-name 100ah LifePo4 for $179.99 off of ebay w/free shipping which is more than the cheapest LA deep cycle battery Walmart sells (~$100) but can easily last 5+ times longer than a LA battery (not a recommendation for any particular battery)

Just another FYI, there is currently a surplus of materials used to make LifePo4 batteries (which is why the prices for them are currently at an all time low and could go lower) due to many auto manufactures cancelling LifePo4 orders due to cutting way back on the manufacturing plans for EV's. Most LifePo4's are made in China (even if the battery says manufactured or assembled in USA as those are most often still made from components made in China) which is why you can now get no-name generic LifePo4's off of ebay for a whole lot less than previously. ~CA
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Old 02-27-2024, 11:09 AM   #6
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I think perhaps you misstated what you meant. You can get 100% of the amps out of a LifePo4 battery without damaging the battery compared to what most battery mfgrs state should be the max draw down of a Lead Acid battery (50%) although many people state you can pull a LA down to 70~80% without damage as long as you recharge it shortly after drawing it down.

Also, you don't need a special charger, although having one is "optimal". I have recently purchased a LifePo4 charger off of Ebay for $23.99 10 amps and free shipping and currently have a 100a LifePo4 battery in my RV without having a converter specifically designed for LifePo4 (just a LA converter).

Also, LifePo4 batteries have come way down in price, you can now purchase a no-name 100ah LifePo4 for $179.99 off of ebay w/free shipping which is more than the cheapest LA deep cycle battery Walmart sells (~$100) but can easily last 5+ times longer than a LA battery (not a recommendation for any particular battery)

Just another FYI, there is currently a surplus of materials used to make LifePo4 batteries (which is why the prices for them are currently at an all time low and could go lower) due to many auto manufactures cancelling LifePo4 orders due to cutting way back on the manufacturing plans for EV's. Most LifePo4's are made in China (even if the battery says manufactured or assembled in USA as those are most often still made from components made in China) which is why you can now get no-name generic LifePo4's off of ebay for a whole lot less than previously. ~CA

It interesting that you posted this. I just ordered a generic 100ah off of Amazon for $179.99 with coupon to run an inverter in my Sprinter. Not expecting anything spectacular for the price, but it is less than what Lead Acid and AGM are selling for here. Worth the shot.

https://www.amazon.com/JITA-Lithium-...zcF9tdGY&psc=1
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Old 02-27-2024, 11:50 AM   #7
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It interesting that you posted this. I just ordered a generic 100ah off of Amazon for $179.99 with coupon to run an inverter in my Sprinter. Not expecting anything spectacular for the price, but it is less than what Lead Acid and AGM are selling for here. Worth the shot.

https://www.amazon.com/JITA-Lithium-...zcF9tdGY&psc=1
I haven't discussed it lately but over the years I have purchased many used medical LifePo4 batteries for pennies on the dollar. Most are 50A rated but when purchased had about 80% (or 40ah) capacity. From my experience and testing, the batteries have maintained ~80% for quite a few years now and should last many years more before going down to ~70% and reports are that they could last ~20 years or more before they hit 50%.

I also purchased damaged LifePo4 batteries for even less and what I found is that most of them were damaged due to having too high of a current draw which damaged the internal BMS boards (often just an internal fuse). So I highly recommend not using too large of an inverter on a single 100ah LifePo4. If your inverter is rated for more than 750~1000 watts, I would consider using 2x100ah Lifepo4's even if you never intend to use more than 750 watts, due to the initial surge when turning on (or connecting) a larger inverter.

Also a thought to add and in particular when using a single LifePo4, because the initial surge that occurs when connecting an inverter can be very high (in particular large inverters but say 800w+), you can (should) use a resistor in series with the + cable for about 5~10 seconds to the inverter (be sure to turn it on before or during those 5~10 seconds) and then after those seconds pass remove the resistor and then connect the cables directly to the battery. This will keep the surge amperage low and protect the BMS. (you could also use an incandescent 12v light bulb). Once connected, you shouldn't have any more initial surge current concerns until the next time you disconnect/reconnect. This may not be needed, but I still suggest to do this and in particular with the lower cost LifePo4 batteries available today which likely will not have the strongest BMS boards inside.

One like this would be perfect. ~CA

https://www.amazon.com/LM-YN-Wirewou...s%2C321&sr=8-6
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Old 02-27-2024, 11:57 AM   #8
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I haven't discussed it lately but over the years I have purchased many used medical LifePo4 batteries for pennies on the dollar. Most are 50A rated but when purchased had about 80% (or 40ah) capacity. From my experience and testing, the batteries have maintained ~80% for quite a few years now and should last many years more before going down to ~70% and reports are that they could last ~20 years or more before they hit 50%.

I also purchased damaged LifePo4 batteries for even less and what I found is that most of them were damaged due to having too high of a current draw which damaged the internal BMS boards (often just an internal fuse). So I highly recommend not using too large of an inverter on a single 100ah LifePo4. If your inverter is rated for more than 750~1000 watts, I would consider using 2x100ah Lifepo4's even if you never intend to use more than 750 watts, due to the initial surge when turning on (or connecting) a larger inverter.

Also a thought to add and in particular when using a single LifePo4, because the initial surge that occurs when connecting an inverter can be very high (in particular large inverters but say 800w+), you can (should) use a resistor in series with the + cable for about 5~10 seconds to the inverter and then connect the cables directly to the battery. This will keep the surge amperage low and protect the BMS. (you could also use an incandescent 12v light bulb). Once connected, you shouldn't have any more initial surge current concerns until the next time you disconnect/reconnect. This may not be needed, but I still suggest to do this and in particular with the lower cost LifePo4 batteries available today which likely will not have the strongest BMS boards inside.

One like this would be perfect. ~CA

https://www.amazon.com/LM-YN-Wirewou...s%2C321&sr=8-6
Thanks for the tip. I'll look in to it. It's going to be powering a small 500w inverter.
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Old 02-27-2024, 01:41 PM   #9
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So @LongIslandCamper, you really need to do a basic energy audit of your trailer to figure out the needs. Here is an example of how to do that - https://outwardspaces.com/tips/how-t...ional-vehicle/

After that is done, you will have an idea of how much energy is needed each day. Then you can plan your battery capacity from there, trading off the pros and cons of Lithium vs. SLA. Depending on how long you will be staying, you may need a method to replenish that power so you can continue your camping trip. This may be solar or generator, or a combination of the two.
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Old 02-27-2024, 03:06 PM   #10
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Thoughts to your question.

You really don't even need a battery if you are plugged in but you do need a battery while towing so your emergency brake-away brakes will work if the trailer gets disconnected from the truck. So with that, you could get by with the smallest deep cycle battery you can find which is usually a group 24 and less than $100.00

However, it only cost a little more comparatively speaking to get the larger deep cycle battery even though it is heavier and cost a little more, but buying the larger deep cycle battery would be more cost effective than buying the smallest for when you don't need a battery and then another larger one for when you do.

Perhaps a 100ah LifePo4 would work for both purposes and they weigh only around 30 lbs. ~CA
Donít you still need a 12 volt battery to complete the circuit?
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Old 02-27-2024, 03:20 PM   #11
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Don’t you still need a 12 volt battery to complete the circuit?
No, as long as you have a working converter then you don't need a battery when on shore power in order to have 12v power.

I will add to my answer though based on a previous RV I owned that I kept at a semi-permanent lake campground, when I removed the battery and insulated the + cables from each other I lost all 12v power. On that RV (and likely others) the converter's output power went directly to the battery on one cable and then another cable went from the battery back to the 12v fuse panel. Having those two battery cables isolated prevented having any 12v power so I had to connect all the positive cables together (I used a SS bolt) in order to have 12v power in the RV (there was also a third cable as well that went to the front jacks which I left disconnected as I was already level).

A point of caution to add, when looking at RV's over the years, I have seen some with a warning label next to the slide switch stating not to operate the slide on converter power only as the slide could pull more power than the converter can output. I think the warning stated not to operate the slide without a battery installed... something along those lines. ~CA
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Old 02-27-2024, 09:46 PM   #12
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I think that's because the 12v supply out of the converter doesn't push enough amps when something like the slide motor needs it. I heard that the battery helps to smooth out those times when the converter is being pushed, and it's recommended to at least keep some sort of 12v battery hooked into the system.
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Old 02-27-2024, 10:45 PM   #13
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I think that's because the 12v supply out of the converter doesn't push enough amps when something like the slide motor needs it. I heard that the battery helps to smooth out those times when the converter is being pushed, and it's recommended to at least keep some sort of 12v battery hooked into the system.
I agree that it would be best to always have a battery installed in almost every situation, except perhaps the situation I had which was that the RV was setup for many years at a campground on a local lake (yearly lease and a couple hours away) that I did a lot of fishing in and often. I determined that the RV worked very well without a battery installed and that the converter installed in mine had enough power for everything needed including the slides (not super slides) and without overloading the converter. Also, I did have a couple of good deep cycle trolling motor batteries handy in my boat if I ever needed a battery in the RV, but I never needed to install one in the RV except when I would travel with the RV on vacation.

Outside of a scenario as I described, I wouldn't even want my RV not to have a battery installed nor would I recommend not having one and my earlier comments were simply that you don't necessarily need a battery installed when on shore power but you do when RV'ing (travelling). ~CA
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Old 02-28-2024, 09:58 AM   #14
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Interesting discussion, but I think the OP "has left the building"
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Old 02-28-2024, 11:22 AM   #15
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Interesting discussion, but I think the OP "has left the building"
Maybe they're out shopping for that battery?
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Old 02-28-2024, 09:18 PM   #16
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Thanks everyone.

Iím still trying to decide what I want to do. Iím all over the map from 2 100ah batteries, or 3 or 4 100ah batteries, to a single 300ah battery, or one 50ah battery and a separate battery box for my dry camping setup.
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