Jackery 500 versus my RV battery

[jornvango]

My Casita trailer has one Duracell AGM group 27 battery with 92 amp hour capacity.
If I can use about 40% before needing to charge it, that's about 40 amp hours I can use.
I paid about $200 including tax.

Since I want to safely charge my laptop (90W 110V charger), I'm debating adding a Jackery 500. I like how it's portable so I can take it with me to use on the road in the car, away from the RV.
The Jackery 500 has 500 watt hours capacity. At 110V usage for my laptop charger, that 500 watt hours converts to 4.5 amp hours. Since it's lithium, that's 100% usable.
The Jackery 500 costs about $600 including tax.

Watt-hours = Amp-hours * Volts

Amp-hours = Watt-hours / Volts

Is the above correct? Does my $200 RV AGM battery give me 40 amp hours (or 4,400 watt hours at 110V) versus only 4.5 amp hours for the $600 Jackery?

If that's the case, I'm better off adding an inverter in my RV to charge the laptop. I can't believe the above is correct since the Jackery 500 would be too pricey for that small amount of power compared to a regular AGM battery...

I have a suspicion that my math is way off. :h

Thanks,!

[Old_Days]

I have the jackery 240 that I have had for 3 months. I agree you are paying for portable power but I have found a lot of things I do with it. It is nice to have power anywhere.

[jjrbus]

I find myself confused, "solar generator" They are not solar, they generate nothing. If I put a solar panel and a couple outlets on my mower is it a solar generator?

[KD4UPL]

40 Ah at 12 volts from the Duracell is 480 Wh. The two are almost identical in usable capacity. I wouldn't be afraid to take the AGM down to 50% or even below as long as it's not every day.

[JimK-NY]

Your numbers are off. The 40 AH @12 v is conservative but correct for your current battery. To compare the Jackery you need to convert 500 Watt hour divided by 12 v = 41.6 AH. They have close to identical useable power.

You laptop charger will pull 90 watts divided by 12 v = 7.5 amps. That seems excessive. I would check that number. That is only roughly 5 hours of charging for either the house battery or the Jackery. Of course, 5 hours of charging is not 5 hours of laptop use. Charging should take well less than an hour and should give you many hours of use off of the laptop battery.

Clearly buying conventional batteries costs much less. Battery banks work best when all of the batteries are identical and of the same age. If you want more capacity and your existing battery is a few years old, then it makes sense to buy at least 2 new batteries. There is another common misconception that 6 v batteries will give you more amp hours. Remember to equate the AH of a 6 v battery to 12v, you need to divide the 6 v AH by 2. You will pay roughly the same and have batteries of equivalent size and weight when buying either 6 v or 12 v batteries. 6 v batteries, especially "golf cart" batteries are built for deep discharge. You can also buy deep discharge 12 v batteries. The typical car battery is optimized for quick cranking power. They work in an RV. They are not ideal but are readily available and often relatively low cost.

[Skibane]

jornvango wrote:
My Casita trailer has one Duracell AGM group 27 battery with 92 amp hour capacity.
If I can use about 40% before needing to charge it, that's about 40 amp hours I can use.

IMO, you're being way too conservative in only discharging it 40 percent.

At 60 percent discharge, you will still get a lot of charge-discharge cycles out of it.

[theoldwizard1]

Your numbers are correct. You are paying a lot for that portability.

When it is time to replace the battery on the trailer, use two 6V golf cart batteries. You will get about 220 Ah and the cost will be around $200.