Jump-starter battery replacement

by Had Robinson

What happens when the sealed lead acid (SLA) battery on these handy devices goes bad?  It only takes about 3 years or less for the battery to become useless and unable to hold a charge.  Should you pitch the whole thing?

This is a Peak jump-starter that had a bad battery.  This model is recommended for 4 cylinder vehicles.  Unfortunately, the company stopped making them and, like most companies these days, has no replacement parts.  It contains heavy duty copper cables with well made clamps, a charger, indicator lights, a test function, a 12VDC socket for anything, a USB charging port, and a heavy duty switch.  The vast majority of users just throw them out after a few years.  How many bother to remove the battery for recycling?  How many of them are filling up landfills with something which only needs a $22 or less battery to be like new?  It is such a waste and so typical of the throw-away culture we live in.  Everything is throw-away, including cars, wives, husbands, families, etc.

If we search the Internet it is easy to discover that eBay and others have every size SLA there is.  The problem is that the batteries which would fit a small jump-starter have 1/4" tabs instead of nut and bolt connections.  The next step some may have tried was to call the manufacturer.  Not only are there no replacement batteries available but you will not even be able to reach anyone who knows what you are talking about or will help.  It is a complete waste of time.

This is the original battery in the Peak jump-starter that has the nut and bolt connections.

The good news is that an ordinary SLA battery of the correct dimensions with tabs will work just fine.  The tabs can be easily modified with a #10 drill bit, the closest to the metric bolt size used on the smaller jump starters.  (A 3/16" bit can be used but you will have to enlarge the hole slightly with a file.)

You have to be very careful drilling the hole because there will not be a lot of metal on the sides of the hole.  Do it slowly,  put a piece of wood just under the tab while drilling.  Locate the bit in the existing hole in the tab.

In tests, I could tell no difference between tab or nut and bolt connections.  My refurbished jump-starter worked perfectly on a nearly dead paragliding winch engine.

Here is a typical SLA battery that can be used in small jump-starters.

Other weaknesses in the jump-starters are how the charge cable is connected.  The Peak has the user simply plug an extension cord into a couple of prongs on the back.  It is best to leave the cord connected or be very careful plugging and un-plugging it.  The plastic housing is flimsy and may be why Peak gave up the business.  The Harbor Freight jump-starter has a much heavier duty outlet in which to plug a power cord (which they supply).

What if you have the much greater capacity Harbor Freight jump starter?  Like every other supplier, HF does not have a replacement battery.  The good news is that the battery they use is available on eBay for about $30 and has nut and bolt connections.  It is less than half the cost of a new jump-starter.  It only takes about 5-8 minutes to replace the battery and then you are good to go.