# Strange charging instructions for my new fill-it-yourself motorcycle battery. HELP!
**URL:** https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296
**Category:** Factual Questions
**Created:** [April 12, 2003, 6:05pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296 "2003-04-12T18:05:44Z")
**Posts on this page:** 19
**Page:** 1
### Author:  [@stuyguy](https://boards.straightdope.com/u/stuyguy)
#### Post date: [April 12, 2003, 6:05pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296/1 "2003-04-12T18:05:44Z")
As you may recall from a previous thread I’ve been having electrical trouble with my bike. Well, it seems like a shot battery was the problem after all, so I bought a new one yesterday.
Unlike all the car batteries I’ve ever bought, this one is a fill-it-yourself-with-acid-then-charge-it type. (I had no idea batteries came that way, BTW. It’s a motorcycle thing, I suppose.)
I’ve got a 1.5 AMP charger that can juice this baby up, but it’s a bare-bones model – no cut-off or indicator to show when the battery is fully charged. But there are instructions and a table that came with the battery that I think might help, except I can’t figure them out. They read:
* * *
We recommend the battery be charged at 1 to 1.5 AMPS, using the following table.
3-5AH Battery —\> 3-6 hours
6-10AH Battery —\> 7-9 hours
[etc.]
* * *
What the heck does the “AH” mean and how do I find the AH rating of my battery?
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### Author:  [@tomndebb](https://boards.straightdope.com/u/tomndebb)
#### Post date: [April 12, 2003, 6:23pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296/2 "2003-04-12T18:23:33Z")
AH = Ampere Hours.
Your battery should have it marked on the side.
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### Author:  [@Reeder](https://boards.straightdope.com/u/Reeder)
#### Post date: [April 12, 2003, 6:26pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296/3 "2003-04-12T18:26:12Z")
AH stands for amp hour, the amount of energy that will flow for one hour at one ampere.
What is the brand of the battery?
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### Author:  [@stuyguy](https://boards.straightdope.com/u/stuyguy)
#### Post date: [April 12, 2003, 6:31pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296/4 "2003-04-12T18:31:38Z")
Nope, Tom.
No mention of AH or Ampere Hours ANYWHERE on the battery, box or instructions. I even checked out the Sears Diehard webpage and found nothing helpful there.
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### Author:  [@stuyguy](https://boards.straightdope.com/u/stuyguy)
#### Post date: [April 12, 2003, 6:34pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296/5 "2003-04-12T18:34:41Z")
Oh, hi Reeder.
It’s a Diehard. The closest thing to a model # is given on a label that reads:
Dept. 28
Stock No. 44358
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### Author:  [@Gary\_T](https://boards.straightdope.com/u/Gary_T)
#### Post date: [April 12, 2003, 6:37pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296/6 "2003-04-12T18:37:12Z")
A rule of thumb is that when the cells start bubbling, the battery is fully charged. If you take it off the charger at that point, you should be fine.
The problem is that leaving it on the charger for very long after that point can result in overcharging, which is harmful to the battery. You have to check it fairly often to avoid doing that.
It’s been a long time since I worked with dry batteries and filled them in the field, but I don’t remember having to charge them after filling. It seems to me that full-strength acid is what you end up with after charging a battery, and I would think that full-strength acid is what you’re putting into it.
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### Author:  [@sailor](https://boards.straightdope.com/u/sailor)
#### Post date: [April 12, 2003, 7:06pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296/7 "2003-04-12T19:06:52Z")
You are pretty safe charging the battery with a charger at 1 - 1.5 amps for about 5 hrs and then just install it and let the bike finish the charge. Just don’t use the starter motor the first couple of times and let the bike charge it.
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### Author:  [@tomndebb](https://boards.straightdope.com/u/tomndebb)
#### Post date: [April 12, 2003, 7:27pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296/8 "2003-04-12T19:27:17Z")
Sorry. I expected them to place it somewhere on the battery. (Most car betteries have _some_ indication.)
As noted on the [HOW TO SPEAK “BATTERY” From the Engineers at DieHard](http://www.danblanton.com/battery.html) page, the AH are used to measure Rated Capacity:
> [@](#):
>
> RATED (20-HOUR) CAPACITY (Ah) – the conventional means for declaring the capacity of a lead-acid battery. It is the ampere-hours that should be delivered by a new, fully charged 12 volt lead-acid battery at 80 degrees Fahrenheit (27-degrees Celsius) during a continuous 20-hour discharge period and maintain a terminal voltage of at least 10.50 volts.
I find it hard to believe (but not impossible to believe) that they do not show the capacity _somewhere_ on the battery. I’d call the store back and ask them to look up their specs.
The battery should be rated in Amps _somewhere_–even if they are too cruel to let the customer see the rating–but perhaps they are simply hiding it in the capacity in hours, as noted above.
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### Author:  [@hammerbach](https://boards.straightdope.com/u/hammerbach)
#### Post date: [April 12, 2003, 8:25pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296/9 "2003-04-12T20:25:54Z")
> [@](#):
>
> \*Originally posted by Gary T \*
> \*\*A rule of thumb is that when the cells start bubbling, the battery is fully charged. If you take it off the charger at that point, you should be fine.
>
> The problem is that leaving it on the charger for very long after that point can result in overcharging, which is harmful to the battery. You have to check it fairly often to avoid doing that.
>
> It’s been a long time since I worked with dry batteries and filled them in the field, but I don’t remember having to charge them after filling. It seems to me that full-strength acid is what you end up with after charging a battery, and I would think that full-strength acid is what you’re putting into it. \*\*
From _Secrets of Lead-Acid Batteries_ by T.J.Lindsay:
“Charging should be carried to completion. If charging is stopped at the point where gassing is to begin or just before, the lead sulphate remaining on the plates can recrystallize from the soft form normally found to a hard form which does not readily take part in the chemistry of charge-discharge. Once converted to this hard crystal form, it cannot be converted back. Over a period of time, much sulphate can be converted to the hard form, and the battery loses capacity.”
It goes on to say that one cell may be less charged than the others and that if you stop charging immediately at gassing, and that this cell will be the one to go bad first, bringing the rest of the battery down with it. Better to let it bubble a short while.
Pure sulfuric acid has a specific gravity of 1.840. Your charged battery electrolyte should have a SG of about 1.265 to 1.285 or so. I’d like to know what you started with. I’ve never measured the electrolyte before it went in the battery… Any idea of that, **GaryT**?
Thanks for a fascinating topic, **stuyguy**!
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### Author:  [@Rick](https://boards.straightdope.com/u/Rick)
#### Post date: [April 12, 2003, 9:29pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296/10 "2003-04-12T21:29:05Z")
There are three ways to measure lead acid battery capacity **A** mp **H** ours, **C** old **C** ranking **A** mps, and **C** ranking **A** mps. (No, CCA and CA they are not the same thing.)
Automotive batteries almost always list one of these three methods on the label. It appears that motorcycle batteries don’t always.
**hammerbach** 1.265 is the specific gravity of a fully charged battery. I have never seen a cell register more than 1.265. The problem with recommending this to **Stuyguy** is that he probably does not own a hydrometer, and if he finds one at an auto parts store, the pickup tube will probably be too large to fit in the fill hole at the top of the cell. (ask me how I know this)
Dry charged batteries will self-charge to about 50-70% with the addition of the electrolyte. A charge of a few hours with your trickle charger will top up the battery. If you really want to be sure that the battery is fully charged, use a volt meter.
Each cell in the battery produces 2.12 Volts fully charged. So a 12 Volt battery fully charged is 2.12 V \* 6 cells = 12.72V (\>12.6 is considered fully charged).
Now in addition to that the charger must overcome the internal resistance of each cell (.2 V).
.2 V \* 6 = 1.2 V
12.72 V + 1.2 V = 12.92 V with the charger attached
When charging (the charger attached and running) a fully charged battery will register 13.92 Volts. (Actually 13.8 or above is considered by the industry to be “fully charged”).
FWIW here are some other handy numbers
75% Charged 12.45V
50% Charged 12.25V
25% Charged 12.00V
Add 1.2 volts to the above numbers to watch the progress of a battery charging, With the charger running.
What ever you do, do not just remove the charger and then measure the voltage across the terminals. You will get an incorrect reading. Batteries get a thing called surface charge. This is extra voltage above the real level of charge. For instance if you battery is 75% charged, and you just remove the charger and then measure the voltage across the terminals, you might see 13.6 Volts and think that the battery is almost done. This would be incorrect. You must remove surface charge before measuring the battery voltage to get an accurate reading. To remove surface charge, either let the battery sit overnight, or discharge it for a short period of time (crank the engine W/O starting for 15 seconds, or leave the headlights on for 30 seconds will also do it). Then turn off the key and measure the voltage.
Oh and one more thing, if you have not yet filled the battery make darn sure that you wear safety glasses when doing so. Acid in the eye is not a fun thing.
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### Author:  [@hammerbach](https://boards.straightdope.com/u/hammerbach)
#### Post date: [April 12, 2003, 9:49pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296/11 "2003-04-12T21:49:23Z")
Sorry, my intent wasn’t to recommend a specific gravity, but just to show that it’s not pure sulfuric acid. Thanks for the info.
Oh, and as to the safety glasses thing… I generally let the other guy fill it. Bad stuff.
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### Author:  [@Gary\_T](https://boards.straightdope.com/u/Gary_T)
#### Post date: [April 12, 2003, 10:02pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296/12 "2003-04-12T22:02:13Z")
**hammerbach** , I was not aware of the info you quoted. I only remember being cautioned not to let the cells bubble away for very long.
I never measured the specific gravity in a freshly filled battery, or of the electrolyte before it was installed. It has been over 25 years since I’ve seen a dry-charged battery.
I have seen hydrometer readings in the 1.275-1.285 range in testing some batteries.
I’ve observed that **Rick** is quite knowledgeable on this subject, he clearly knows some details that I don’t.
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### Author:  [@stuyguy](https://boards.straightdope.com/u/stuyguy)
#### Post date: [April 12, 2003, 10:44pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296/13 "2003-04-12T22:44:06Z")
Rick wrote:
> [@](#):
>
> When charging (the charger attached and running) a fully charged battery will register 13.92 Volts. (Actually 13.8 or above is considered by the industry to be “fully charged”).
This sounds like just the ticket! I’ve got a little voltmeter, so I’ll check the voltage every half hour or so after 3 hours. When it hits 13.8 or higher I’ll disconnect.
That’s a good plan, right?
(According to the instructions, after the first charge is complete I should add distilled H2O to replace any lost acid and charge for another 30 minutes. I assume that’s valid advice, yes?)
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### Author:  [@Rick](https://boards.straightdope.com/u/Rick)
#### Post date: [April 12, 2003, 11:59pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296/14 "2003-04-12T23:59:37Z")
> [@](#):
>
> \*Originally posted by stuyguy \*
> \*\*This sounds like just the ticket! I’ve got a little voltmeter, so I’ll check the voltage every half hour or so after 3 hours. When it hits 13.8 or higher I’ll disconnect.
>
> That’s a good plan, right?
>
> \*\*
sounds like a great idea.
> [@](#):
>
> \*\*
> (According to the instructions, after the first charge is complete I should add distilled H2O to replace any lost acid and charge for another 30 minutes. I assume that’s valid advice, yes?) \*\*
You may or may not lose any electolyte during the charging process. If you do then top with water only. NOT more acid. If you do have to add water a little more time on the charger at that point couldn’t hurt.
Oh, and **Gary T,** from one pro to another, it is nice to recognized. ::: tips hat:: 🙂
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### Author:  [@handy](https://boards.straightdope.com/u/handy)
#### Post date: [April 13, 2003, 3:23pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296/15 "2003-04-13T15:23:09Z")
I prefer to charge for about an hour then put it in the car or cycle & drive around for a while to charge it (about 20 min).
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### Author:  [@stuyguy](https://boards.straightdope.com/u/stuyguy)
#### Post date: [April 14, 2003, 5:15pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296/16 "2003-04-14T17:15:32Z")
Okay, something wierd is going on.
I filled the battery with acid and hooked it up to the charger an hour and 45 minutes ago. Using my voltmeter, the battery showed a charge of 12+ V when I first hooked it up. (Voltage measured with charger on.)
**It’s up to 14.6 V already!**
What’s going on? How can it get so high? Should I stop charging? It hasn’t even been 2 hours yet. I’m confused. HELP.
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### Author:  [@Hampshire](https://boards.straightdope.com/u/Hampshire)
#### Post date: [April 14, 2003, 5:42pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296/17 "2003-04-14T17:42:43Z")
I just got a new battery for my motorcyle over the weekend. Who knew they didn’t come charged? The bike originally came with a 15ah battery but I upgraded to a larger 19ah.
I bought from the dealer a $60 smart charger that blinks when the battery is 80% charged and stays lit when completely full. It also states it’s safe to leave on this type charger and won’t damage it.
A very handy $60 investment.
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### Author:  [@Rick](https://boards.straightdope.com/u/Rick)
#### Post date: [April 14, 2003, 6:31pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296/18 "2003-04-14T18:31:38Z")
I would say that you are done.
If you aren’t sure, take the charger off and leave the battery overnight so that the surface charge disappears. Then check the voltage, if it is 12.6 V or above you are good to go.
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### Author:  [@stuyguy](https://boards.straightdope.com/u/stuyguy)
#### Post date: [April 14, 2003, 6:42pm UTC](https://boards.straightdope.com/t/strange-charging-instructions-for-my-new-fill-it-yourself-motorcycle-battery-help/168296/19 "2003-04-14T18:42:33Z")
thanks, rick.