[///d]

Can someone clear this up for me?

I'm looking for a battery for my teardrop camper trailer. I know if I have EVERYTHING powered on I will be at 38.5 amps, but I will never have everything on at once so I'm figuring at most 15amps at once at the most.

When researching batteries and how to calculate battery life they say divide your capacity (amp hours) by your load (amps) to get your battery life in hours. However, I found that the accepted amp hour rating time period for 12v deep cycle batteries and the likes is a 20hr rate, and lithium batteries at 10hrs until they drop below 10.5v, and I see the 20hr and 10 ratings spec on Batteries Plus that states "Capacity 20hr: 30AH" and so forth.

Thats where I get confused, when looking at a 30AH Lithium battery, does that mean that it can provide 30amps for one hour before dropping below 10.5v, or does it mean it will provide 30amps per hour for 10 hours before dropping below 10.5v?

[dreamingat30fps]

Originally Posted by ///d

Can someone clear this up for me?

I'm looking for a battery for my teardrop camper trailer. I know if I have EVERYTHING powered on I will be at 38.5 amps, but I will never have everything on at once so I'm figuring at most 15amps at once at the most.

When researching batteries and how to calculate battery life they say divide your capacity (amp hours) by your load (amps) to get your battery life in hours. However, I found that the accepted amp hour rating time period for 12v deep cycle batteries and the likes is a 20hr rate, and lithium batteries at 10hrs until they drop below 10.5v, and I see the 20hr and 10 ratings spec on Batteries Plus that states "Capacity 20hr: 30AH" and so forth.

Thats where I get confused, when looking at a 30AH Lithium battery, does that mean that it can provide 30amps for one hour before dropping below 10.5v, or does it mean it will provide 30amps per hour for 10 hours before dropping below 10.5v?

As far as I know a 30AH battery would provide 30amps for 1 hour or 1amp for 30 hour etc. Not really sure if that's what you're asking.

[antgenn]

Originally Posted by ///d

Can someone clear this up for me?

I'm looking for a battery for my teardrop camper trailer. I know if I have EVERYTHING powered on I will be at 38.5 amps, but I will never have everything on at once so I'm figuring at most 15amps at once at the most.

When researching batteries and how to calculate battery life they say divide your capacity (amp hours) by your load (amps) to get your battery life in hours. However, I found that the accepted amp hour rating time period for 12v deep cycle batteries and the likes is a 20hr rate, and lithium batteries at 10hrs until they drop below 10.5v, and I see the 20hr and 10 ratings spec on Batteries Plus that states "Capacity 20hr: 30AH" and so forth.

Thats where I get confused, when looking at a 30AH Lithium battery, does that mean that it can provide 30amps for one hour before dropping below 10.5v, or does it mean it will provide 30amps per hour for 10 hours before dropping below 10.5v?

It depends on the battery type and how you "allow" to use it. For acid/AGM, you cannot drop below 50% capacity as deeper discharge will permanently damage it. Lithium can be safely discharged to 20% (theoretically to 100%). That means that you can get 50 Amp Hours from 100amp acid battery or 80 amp hours from Lithium. From here you divide your available capacity by current to get the hours that battery can support the given amp consumption. And, to be precise, you need to account for losses due, for example, for efficiency of your converter.
So from your 30AH battery you can get 0.8x30/30=0,8 hours at 30 amp of permanent load.
I have a set up with 400AH of Lithium, 400W solar, 3500W/30amp inverter-charger. My biggest loads draw 130 amp microwave and 75 amp Air Conditioner. AC use and power consumption will be first tested this weekend.

[antgenn]

There are plenty of good videos on this. I used some basics for solar application from here: https://www.youtube.com/c/WillProwse

[///d]

Originally Posted by antgenn

It depends on the battery type and how you "allow" to use it. For acid/AGM, you cannot drop below 50% capacity as deeper discharge will permanently damage it. Lithium can be safely discharged to 20% (theoretically to 100%). That means that you can get 50 Amp Hours from 100amp acid battery or 80 amp hours from Lithium. From here you divide your available capacity by current to get the hours that battery can support the given amp consumption. And, to be precise, you need to account for losses due, for example, for efficiency of your converter.
So from your 30AH battery you can get 0.8x30/30=0,8 hours at 30 amp of permanent load.
I have a set up with 400AH of Lithium, 400W solar, 3500W/30amp inverter-charger. My biggest loads draw 130 amp microwave and 75 amp Air Conditioner. AC use and power consumption will be first tested this weekend.

So what is the rated time period for then? Everything makes sense to me until I see the rated period specs.

Using the generic AH/Load, for a 30AH battery, theoretically I should be able to run my 15amps combined for 2 hours continuously, or my 5amp fan for 6 hours continuously (not including additional losses). But then throw in the "accepted rated time period", unless I am interpreting the rated time period wrong, if a Li battery is rated for 30AH @ 10hrs time period then I should be able to run 15 amps for 20 hours before I drop to 10.5v of power and the BMS switches off the battery.

I must be misunderstanding what the rated time period is.

And actually, this battery may even fall into the 20hr rated time period category.

"The accepted ampere hour rating time period for solar electric batteries, deep-cycle batteries and backup power systems -- uninterruptable power supplies -- is generally a 20-hour rate. The rating indicates that the battery is discharged to 10.5 volts over 20 hours, while the total ampere hours supplied is measured."

[Atavus]

In reality, you might not get a whole hour at 30 amps, but you’d possibly get more than 60 hours at half an amp. The rated time period gives a way assess and you can see if that drain pattern suits your consumption.

[antgenn]

Originally Posted by ///d

So what is the rated time period for then? Everything makes sense to me until I see the rated period specs.

Using the generic AH/Load, for a 30AH battery, theoretically I should be able to run my 15amps combined for 2 hours continuously, or my 5amp fan for 6 hours continuously (not including additional losses). But then throw in the "accepted rated time period", unless I am interpreting the rated time period wrong, if a Li battery is rated for 30AH @ 10hrs time period then I should be able to run 15 amps for 20 hours before I drop to 10.5v of power and the BMS switches off the battery.

I must be misunderstanding what the rated time period is.

And actually, this battery may even fall into the 20hr rated time period category.

"The accepted ampere hour rating time period for solar electric batteries, deep-cycle batteries and backup power systems -- uninterruptable power supplies -- is generally a 20-hour rate. The rating indicates that the battery is discharged to 10.5 volts over 20 hours, while the total ampere hours supplied is measured."

Not sure how that applies, however you only can use stored energy up to 100% capacity and if you use more amps per hour it will last less. Like water in the tank: 100 gal will run out in 2 hours @50gph or in 4 hours @25gpm. I did not use advanced formulas for my calculations and I am using the system I build for 2 years now. My battery monitors shows amp/time relation pretty close to those basic calculations.
So with 30AH on board you will run 30 amps for 1 hour. What I suggest you do is to make a Excel table listing all the devices that consume power and evaluate not just the amps, but the usage per day so you can see the total power demand. Then you can see how much you can get back by recharging from solar or while driving ( if your alternator is capable of extra 30 amp of load) and that will give you the goal capacity. You may not like the number and will revise your assumptions several times...

[///d]

antgenn messaged me for an update

I ended up going with a 110AH AGM battery, and picked up a 100w solar kit with a 30A PWM controller.

Since we will likely charge our phones in the vehicle those wont need much power from the trailer, maybe 5 amps combined for a couple hours at night, if even that. My fan runs at 5 amps and that will run all night. The solar should be enough to recharge what we use each night, and since we will use barely any power during the day I suspect this setup will be plenty. I can run up to 4 panels on this controller, so if I need to ad an additional I can.