on using a switching circuits with your design i would look at mosfets can handle very high current

Some well over 35 amps and more and almost no heatsink is needed like with switching darlingtons

USED 100 WATTS mosfets without a heatsink for H-BRIDGE design and not like switching transistors you can easy add in parallel to double the current rating with switching transistors (darlingtons ) YOU NEED A FEW RESISTORS with mosfets none is needed

Second i am looking at building a robotic mower ,but with our gas for many reasons,need a very very big battery larger frame ,plus very powerfull drive motors

BUT still you project does look good

Look at rc esc they work great an cheep

Simple $5.00 mosfet circuit or less is easy to make and easy handle 25 amps and no heatsink ,RELAYS not a great idea,cost is high plus you need a switching circuit if using a 25 amp darlington switching circuit you will need a good size heat sink

IRFZ44 mosfet is so simple to use ,it hooks the same as switching darlington circuit and resistor value is same,and no heatsink is needed,plus no power is wasted

pittom i see i am not the only one that doesnt use spell check and RICH has said to me a few times

lol especially when it is late

I don't want to drag this off topic, but since you brought it up. @robotmaker, it has been much easier to understand what you are saying in the past week or so since you have been checking your spelling and grammar. I had gotten to the point where I just skipped your posts because I never could figure out what you were trying to say, but you are much easier to read now, so thank you.

One extra hint that I have used to help people who sometimes have trouble communicating in writing.. Read your posts out loud before you hit send and make sure they sound right. It can help when you are typing so fast you get your words out of order. Just reading silently doesn't seem to do it, but reading out loud you actually hear yourself and can notice more. (I planned on telling you this privately when I asked you to email me a few weeks ago, but you wouldn't, so here it is...).

Thanks for your recent information on mosfets. It led me to look up some information and they seem to be very useful.

Alan

YES i know ,been awhile since i did any good writing and started to slowing comming back to me

This forum is first time i did any writing in over 20 years,never really had the need too.

I have a lot of work and dont really have the time to recheck my spelling or grammar and some is not needed ,like periods and capital letters

But my posts are getting better ,and most likely to make easy to understand them will do a few posts and not put many words in them.

Also of my words i use are very technical and most here dont know what it meens. like RDS on mosfets not many knows what it meens .

MOST think i am wrong on the mosfets,yet i know more about them then most of the guys here .

We are almost complete with one hang up. I used a battle switch to operate the solenoid for the starter on the gas engine. The switch is rated at 10 amp on 24V and 5 am on 12V. It operates the solenoid correctly but once the solenoid is wired to the starter it fries the battle switch. I am sure it is pulling to many amps but I havent seen a battle switch rated for higher amps? Any ideas?