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Improved Pilot InstaBoost Jumpstarter Clamps

The Sienna now spends all its time sitting outdoors in an apartment parking lot and gets even less driving (hence, battery-charging) time than we used to give it. Fortunately, Santa being my kind of guy, our Larval Engineer received a Pilot InstaBoost jumpstarter, which is basically a 10 A·h / 40 W·h lithium battery with husky plug & socket connectors, a pair of 10 AWG wires, and big alligator clamps. The package claims a 400 A peak discharge rate, but the tiny inscription on the back of the case reports 200 A; either of those seems mmmm somewhat optimistic to me.

The customer reviews suggest that the plastic battery clamp handles feature a crappy hinge joint which disintegrates under moderate stress on a cold winter night, firing the spring into the nearest snowbank and rendering the clamp completely useless. The joint consists of a plastic post on each side of the inner handle that protrudes into a hole in the outer handle:

Battery Clamp - original joint

Battery Clamp – original joint

I assigned her some Mandatory Quality Shop Time to improve the joint. She found some brass tubing that fit the existing hole and cut two pieces to length:

Battery Clamp - cutting brass tube

Battery Clamp – cutting brass tube

A 1 inch stainless screw was just barely long enough (that’s Loctite Red in the nut), but the end result certainly looks durable enough:

Battery Clamp - improved joint

Battery Clamp – improved joint

It’s along the same lines as the improvement I applied to my old Park Tool MTB-7 Rescue Tool.

Apart from that, the clamps look pretty good. There’s even a husky braid between the two jaw pads, ensuring at least one reasonably low resistance joint to the battery post:

Battery Clamp - jaw strap

Battery Clamp – jaw strap

With a bit of luck, we’ll never know how well it works as a jumpstarter. She can use the USB port to keep her phone charged, which may provide enough motivation to keep the thing topped up and ready for use…

[Update: two days after this post went live, someone found it by searching for:

how to repair clamps pilot instaboost 400

You have been warned!]

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  1. #1 by David on 2015-01-01 - 15:30

    Does the heatshrink on that braid go all the way into the crimp? Or is it just the way the photo looks?

    • #2 by Ed on 2015-01-01 - 19:29

      All four pads have the heatshrink butted up against the crimps. Dunno if crimping the insulation would be good (better strain relief) or bad (interferes with metal-to-metal contact)…

      • #3 by david on 2015-01-01 - 23:20

        Definitely bad — that joint will only flex a dozen times in the thing’s lifetime…

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