Technical battery question

Good afternoon people. I have a question for you technical types. I'm building a simple demo box to demonstrate a product I offer. Inside of a small tool box I'll have a fuel-fired heater that also runs on 12V. I have very limited space so I'm thinking a small motorcycle battery or a lawn tractor battery. I was at a battery specialty shop yesterday and they said what I'm doing will destroy a motorcycle battery because "that's a starting battery." Here's the specifics:
The heater will draw 20 amps for about .25 seconds, then will draw 2 amps/hour for 3 minutes, then dropping to less than 1 amp/hour for the duration of the demo, less than 15 minuted I figure. I will put it on a battery charger at the end of the day, or even in my car during the commute to the next place.
Here's my question:
What is the difference between a laws tractor battery, a motorcycle battery and a car battery. They are all starting batteries, and they all will have a small load during operation (lights, injection systems, espresso machines etc.) so why won't a lawn tractor/motorcycle battery survive what I'm asking of it?

Sears/Napa has deep cycle gel type batteries for LG/Motorcycles usually around $50.00

I think a lawn tractor or bike battery would do fine for your application. O'Reilley's had them on sale recently for like $19 or something. I picked up one for my generator. An automotive ("starting") battery is designed for big loads for short periods of time, versus a deep cycle battery that is designed for lower loads for longer periods of time. Plate construction is different or something. One can be used for the other, but with less life expectancy. For what you're drawing, I bet either would be just fine. Even a UPS battery would work for that. You're talking around a quarter amp hour per demonstration.

Deep cycles also are designed to deliver a consistent amperage during discharge with less fluctuations than a normal starting battery. But the draw you're talking about I don't think it would matter much.

Marty!!!

OH yeah, another thing. These heaters are designed to be installed on a over the road vehicle, so the fluctuations during discharge are ok. I'm going to look into the NAPA batteries because that's the price for a motorcycle battery, that's not even gel cell.

Just remember you can't 'fast charge' a gel cell battery- just in case you get into trouble.

I think it would be fine, just recharge during the commute. If you are not discharging it below 5% it shouldn't effect a starting batteries life significantly.

To charge it, maybe a cig lighter to cig lighter adapter, with a socket added to your demo box.

A blue top Optima marine battery would be ideal, but you'd likely have to get a bigger tool box..

Hawker Odyessy Dry Cell? They make a really small one that still cranks out almost 700 CCAs

With a peak 20A draw, CCA's won't matter too much. More Ah, but that is even pretty low.

You could probably run it off of an R/C battery pack.

There is a difference between the battery types.

Motorcycle batteries are typically built tighter internally. More plates closer together, and they are thinner. That's why motorcycle batteries usually don't last more than two years in service. It's all part of making them extremely small and light.

Lawn tractor batteries are built with more space between the plates, and the plates are thicker. That's why these batteries tend to last for many years. They are larger and heavier than motorcycle batteries. They also cost less.

Car batteries are built similarly to lawn tractor batteries. Thicker plates and larger spacing between them when compared to a motorcycle battery.

Your proposed battery load is minute. Any of them will hold up to it just fine for a year at least. If it's display unit I had to carry a lot, I'd go with the lightest battery. If it's going to be set on a table, I'd go with the cheapest battery.

While wet cell batteries would work, I don't recommend charging inside the passenger compartment as you travel. Explosive, smelly, corrosive gas plus you really don't want one to turn over on the leather seats!

Gel cell would be a good alternative,but may still have an issue with the 15 minutes of drawing power.

I have played with a lot of batteries with various solar and electric vehicle projects and learned not to try to reinvent the wheel.

My recommendation is to use a portable jump start box. All the electronics in one small package plus you have a useful tool for your car.

Or if you want slick looks, you could use cordless drill batteries. Charge it in the car, have a backup or two, build a workbench on the weekend!!

Bruce