From:Dave Hennessey
Subject:RE: RE: BATTERY INFO Date:Mon Oct 13 20:32:19 2014
Response to:19934
I agree - it's probably toast. Hook it up, turn on the headlight, and see how long it stays lit. A surface-charge will last about a minute.

Another point is that you should never add acid to a battery that is low - only water (distilled is best). Then let it sit on a one amp charger for a long time. Sometimes they will come back to life after a week or so.

Also, never dump the old acid out of the battery. Turning it upside down will cause all the crap that has sunk to the bottom to come towards the top and stick in places it shouldn't be.

If it's an original Harley battery - definitely save the case. Someone may want to buy it. Same for an aftermarket WISCO.

Check the How To Restore section under Batteries. If you only do occasional daytime driving, the gel cell (Amazon) in a fake Harley-looking case (Taylor Custom Cycles) will do fine. These batteries were not designed for the vibration of a motorcycle, so they won't last forever, but at the price...

Also, if you hook two in parallel, using a double-bladed knife connector, you not only get twice the amp-hours, but also if one fails, you can disconnect it an run on the other one. That's what I do on my Henderson, and they tend to fail regularly, so I keep a spare on the shelf.

Unfortunately, both the Model 125/165 and the K and pre-1965 Sportsters use these oddball H3 batteries. If you do find an olde-fashioned lead-acid battery that will fit, let us know!


You'll be lucky if it does. You're probably only reading a 'surface charge' and not the real charge of the cells. Batteries that are properly maintained (read fully charged) have a balance in the electrolyte. The acid at this charge (potential) doesn't hurt the lead plates within. Let it drop beyond a certain point and the lead begins to absorb the acid. When this happens the lead begins to deteriorate (sulfation). If it were steel the term would be 'rust'. Sulfation cannot be reversed no matter if you add acid or charge it forever. Long story short? Your battery is toast. At today's prices it's worth buying a battery tender and leaving it on all the time. Buy a good one and also realize a 'tender' is not a charger.....make sure your battery is fully charged before you put it on the tender. Another wise piece of advice is don't ever use the 'quick charge method' on any battery unless it's an emergency. It warps the plates, boils off the water in the acid, and shortens the life of the battery. NOTE: Battery prices will double and possibly triple in the next few years as the Obama Administration recently used the EPA/DEP to shut down the last lead mine in the USA. All lead will be imported. That lead will be will all the rest of the battery components. I'm not being political here, I'm being informative. Don't even get me started on gel cells......

I let my 6Volt battery run down and after maybe a couple of years I put battery acid in and charged it slowly on and off several times over several days. It seams to be holding 5 volts, do you think that 5 volts will start my 1952 125cc Hummer or is the battery done for?