hydrometer ?

55 50 Ron · Aug 13, 2019

Do you use a hydrometer to test lead acid batteries? I've read some articles that say the hydrometer is the most accurate way to test condition of lead acid batteries. Facts or opinions?

Janicholson · Aug 13, 2019

It is a direct reading of the temperature adjusted specific gravity. As such it measures the Mass of the battery acid against gravity. The higher the charge in the battery, the more Sulfur is chemically moved into the fluid, and off of the plates. Thus the "acid" weighs more. When discharged, the acid can become much less saturated, and watery. This can allow a battery to freeze when dead and cold. If there has been no added distilled water, and if the cells are accessible, it can sure do a good job. It also shows distinct differences between good cells, and bad. Jim

Bob · Aug 13, 2019

A "load test" whether done with an old-fashioned tester that converts battery capacity to heat or by a modern electronic digital pulse load tester will give a MUCH more accurate evaluation than a hydrometer.

I'll bet not many vehicle or tractor dealerships even have a hydrometer anymore.

gene bender · Aug 14, 2019

Yes it is the best because it will show all the cells condition. If they aren't up to snuff of course the load test will show failure.

Geo-TH,In · Aug 14, 2019

Hydrometer doesn't work on AGM, sealed batteries.

John T · Aug 14, 2019

Mornin Ron, good question, in my "arsenal" used to test flooded lead acid batteries I have three instruments and may use one or more or all as conditions and results indicate.

Volt Meter,,,,,,,,Load Tester,,,,,,,,,,Hydrometer

The voltage can indicate to at least some degree of accuracy the State of Charge (SOC)... HOWEVER it must be when the battery is at rest and stabilized ?? Its a useful (even though not all knowing) tool if you have nothing else...

The Load Tester can indicate a batteries ability (or inability) to store energy...

The Hydrometer can indicate the SOC and condition of each individual cell (See Jim's great explanation below)

All three can provide information as to the batteries SOC but each work differently and provide different information so I like having all three in my arsenal so I have choices and options even though I may or may not use all three of them ???.

That's what I like having and "That's my story n Ima stickin to it" lol

Take care Ron

John T

Mike M · Aug 14, 2019

I do like a hydrometer. But many batteries don't have caps you can get off either.

Determined · Aug 14, 2019

(quoted from post at 08:09:55 08/14/19) Mornin Ron, good question, in my "arsenal" used to test flooded lead acid batteries I have three instruments and may use one or more or all as conditions and results indicate.

Volt Meter,,,,,,,,Load Tester,,,,,,,,,,Hydrometer

The voltage can indicate to at least some degree of accuracy the State of Charge (SOC)... HOWEVER it must be when the battery is at rest and stabilized ?? Its a useful (even though not all knowing) tool if you have nothing else...

The Load Tester can indicate a batteries ability (or inability) to store energy...

The Hydrometer can indicate the SOC and condition of each individual cell (See Jim's great explanation below)

All three can provide information as to the batteries SOC but each work differently and provide different information so I like having all three in my arsenal so I have choices and options even though I may or may not use all three of them ???.

That's what I like having and "That's my story n Ima stickin to it" lol

Take care Ron

John T

In addition to the fine information that John has posted I will add 2 more things that I do;

Time and temperature.

Starting with time, I have come across a few batteries that passed all of the above tests yet let them sit for a week completely disconnected and they would self discharge themselves down to 8-9 volts.

Temperature; every fall I seem to have a dozen or so batteries from vehicles, tractors, fencers, boats etc lined up on the shop floor.
After being charged and tested I set them outside when it is minus 40 for a week.
Bring them back in and check them after they have warmed up for a few days and weed out the ones that could not handle it.

westga · Aug 14, 2019

There are different ways to test a battery. But the hydrometer can be the "last word" on the lead acid battery.

Old school phone co. employees preferred hydrometers.

dr sportster · Aug 14, 2019

That is how to test it chemically .A meter tests it electric wise.

55 50 Ron · Aug 14, 2019

Thanks folks. Lots of good information. My curiosity to post this was prompted by me finding the hydrometer that my dad used on the farm in North Dakota in the 1950s and 60s and it was in stuff of his that I saved after his passing. I tried it on some batteries (some I know are good and some I know are bad) and after all these years it still found which ones were good and which ones were bad.

hydrometer ?

55 50 Ron

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Janicholson

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Bob

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gene bender

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Geo-TH,In

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John T

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Mike M

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