Small Battery Instead of Large Deep-Cycle

My 2 cents: My horse trailer (8000 lbs GVW) with electric brakes runs off a very small battery. If all you want is a battery for your emergency electric brakes, go to Etrailer and search "Trailer Breakaway Kit". That may be what you are looking for.

I can see where the OP may want to do this if he wants to reduce weight.
A small 12 volt lawnmower battery at Wallyworld is 18 pounds and costs about $20. Whether that has enough reserve to power break-away brakes or not, I don't know. I would assume that it does because those brakes only need to hold for the short time the trailer is free until it comes to a stop. But I am not knowledgeable in how much juice this would take. If you are doing a lot of mountain travelling, probably not a good idea. But maybe a possibility if you travel mostly in flat terrain.

A group 24 deep cycle shouldn't be more than about $75.
I don't know if the lawn mower battery would lock down your trailer brakes for very long in a break-away situation.
Many converters use the battery to help filter their output. The smaller the battery the less filter.
Do you have slides? Most slides pull too much to operate on the converter alone and use battery power to help. A smaller battery might not allow the slides to work properly.

OK but why replace at all?

We do not camp without shore power and boon docking is not on our list. However we were at times limited on our campgrounds when traveling out west. Twice we have lost power for several hours.

The ability to camp-over for a night or two at a primitive sight or a city park camp ground is handy.

But you are correct, if you spend your weekends at Yogi Bear campgrounds you do not need much of a battery.

I have a 2002 Jayco Eagle 266FBS. I'm not thinking of using a motorcycle battery, rather a lawn tractor battery. The lawn tractor battery is $39 as opposed to over $100 for a deep cycle like is on there now.

I think before I buy, I'll just take my lawn tractor battery out and give it a try. I feel sure it has enough power to operate the brakes in a break away situation. I see much smaller sealed batteries mounted for the same purpose.

Thanks for the responses.

If your rv style involves parking the rig while you visit or sightsee, you might have limited amps using a battery that's too small.
A hybrid deep cycle from Walmart, grp 24 will do the job and not be too heavy and at the same time probably be the same price as a smaller motorcycle/tractor battery.

You Do you not need a large Deep Cycle for what you are doing. But, in my area the motor cycle batteries are not much cheaper then a small car battery and a small car battery would do what you want.

How much will you save by installing a small battery rather than the correct size?
And, is it really worth it?

Not knowing what TT you have, do you have break away brakes on TT ? If so, be sure it has enough reserve to power the brakes in case of an emergency. Also be sure it's a 12 volts battery. If you have electric jack it requires 12 volts and I don't think you want to plug in to a 120 source just to jack the TT each time.