A strong relay for sabertooth 2x32 and ESC, lawnmower

I'm running (2) 18AH lead acid batteries, to my Sabertooth 2x32, and a brushless RC ESC to drive the mower motor. As of now, I just connect the power connecters and cringe when I see that huge uncomfortable spark. I also have a 30a DC switch connected to sabertooth 2x32.

After talking with tech support at Dimension Engineering, they suggest I replace my switch with something heavier duty, since the Sabertooth feeds power back into the batteries for a regenerative breaking function (I am not totally certain how it works). They explain, it will try and push ALOT of power back to battery, and any weak link in the power lines (or limit to battery to absorb current-in) may cause the errors that I am having. They have also advised me AGAINST using a FUSE on this line - as that has known to cause trouble with their other customers. I asked them if I could just simply put a large capacitor in line, I was told that would not work either. I also asked if I could just put some high-recharge lithium cells in parallel in front of lead acid batteries, and was told that will not work as well.

Ideally, I would like to have strong relays controlled by my Arduino - so a simple low voltage switch, can activate the microcontroller's power, then my R/C safety system can be in control over the high current power lines to the Sabertooth & ESC.

I used relay's but they seem expensive. I think the 20/30 amp ones are common and at first try that would probably do the trick. I guess if they are too weak to handle a momentary high current spike - who knows what will happen ? I guess worse case, to ruin the expensive Sabertooth driver :frowning:

I would like to save cost of course. I am running 24v system, my ESC (a R/C hobby airplane brushless hobbywing) is "80 amp". The Sabertooth is 2x32, so (I guess it's maximum is 64 amp). The 20/30 amp relay's are common and fairly priced, however - when I search for 100 amp relay's - they are kind of costly at $25+ each - 2 of them $50.

I was wondering if anyone had any suggestions on a less expensive relay device to use, please.

I never was comfortable with the big spark that big ESCs produce plugging in.
Because it is the same spark that comes right after you hook up things wrong.
Which immediately precedes the release of the magic smoke.
I have heard of people putting in a pre-plug process with a resistor to slowly charge the big caps, but have never bothered.
I DID put in a shunt so that I could plug in my batteries without powering the system and then plug in the shunt to finalize the power up process, but that was more pf a practical thing since the big batteries were often difficult to get in and out of the RC aircraft.
I have had good experience with the guys at Dimension Engineering. And they are a local company for me!

It looks like your setup has ground connected first. If the "shunt" is the wire jumper for positive, I understand correctly.

I feel like I have to use some that Dr. Frankenstein switch in order to toggle my electricity:

or buy a $50 relay. This is the part where I regret not buying the box of relay's I thought I would never use at the flea-market for $5.00

Something like this might work for the connection. I believe it makes contact through a low resistance shunt then the main connection.

I kind of like that big frankenswitch.