Better way to check battery SG?

[ktmrfs]

I keep thinking there must be a better way to check battery SG. A good hydrometer is almost ideal, the issue I keep having is the top of the float wanting to rest on the glass making repeatable measurements problematic.

Well, finally decided to do some looking and may have found a better way, not necessarily less expensive, but at least much more repeatable and just as easy.

A battery refractometer. Refractometers are a pretty common way to check coolant concentrations and make sure your DEF fluid is at spec.

Turns out there many available that will do battery SG and Coolant concentrations. I settled with one from RobinAir, prices vary all over the place, RobinAir seems to be a good company.

Now for the test.... I recently did testing on my 10 year old set of Trojan GC batteries with my Frieze hydrometer, Cells were all pretty consistently high, problem was if I did repeated measurements on a given cell, it would read between about 1.275 and 1.300 depending on how the float rested.

With the Robins, repeated measurements were dead on, never varied even 0.001 And, with the 4 batteries lowest SG was 1.298, (2) highest was 1.301 (1), the rest were at 1.300

Test method was to do a full charge with my PD charger, then I topped off all the cells with water from my battery watering jug which stops at a fixed level, did another top charge

Probably took less time than using a hygrometer with a float and is more repeatable.

Now if Mex is still around like to get his take on using a refractometer vs. hydrometer for measuring SG.

[ktmrfs]

time2roll wrote:
I always tried to avoid the hydrometer whenever possible.
After swapping to LFP I doubt I will ever use one again.

I suspect my current flooded cells will last another year or so. If LFP are competitive price wise I'll switch if not another set of flooded cells and I'm sure by the time they are dead (10years) it will be LFP.

And by then things like hydrometers will be like a vacuum gauge for adjusting ICE fuel mixture or timing lights to adjust timing. Most people won't have a clue as to what they are, let alone how to use them and not anything they can use them on either.

[opnspaces]

ktmrfs wrote:
I keep thinking there must be a better way to check battery SG. A good hydrometer is almost ideal, the issue I keep having is the top of the float wanting to rest on the glass making repeatable measurements problematic.

I have to agree with you on this ktmrfs. I tried a few times over the years to use my hydrometer but the float always sticks to the tube. Now I just take a voltage measurement and see if I'm around 12.7 when full.

After a few years goes by and it seems that the batteries are draining faster than normal when dry camping I just replace them. Yes I could spend time maintaining my batteries and extend their life from 5 years to 10. Maybe when I retire I'll pay more attention to my batteries. But in my current life usually I have too much going on to have time to worry about my weekender trailer batteries.

[2oldman]

time2roll wrote:
After swapping to LFP I doubt I will ever use one again.

I guess you have to be a die hard tinker to want to keep doing this with acid batteries.

[time2roll]

I always tried to avoid the hydrometer whenever possible.
After swapping to LFP I doubt I will ever use one again.

[ktmrfs]

Gdetrailer wrote:

ktmrfs wrote:

Gdetrailer wrote:
All I have ever used for batteries is the simplest, cheapest "ball" type in a tube Hydrometer..

Sort of like this one..



All of the balls rise, the battery is fully charged..

Simple, cheap and effective.

These work ok to tell if a battery is well on it's way out, but not real good at an accurate SG cell to cell comparison. And all balls rise usually means SG is between about 1.250 and 1.300, a pretty noticeable difference in battery real condition.

But yes, they will tell you if you've got a cell or battery heading south.

Sort of splitting hairs to find the "holy Grail" of perfect in an imperfect world.

There will always be some small discrepancy between cells, trying to achieve the exact same ideal 1.300 on every cell is pretty much a futile effort.

The discrepancy comes from slight differences in grids, how they are molded (grids can vary due to how much flash there is left after the molding) and composition of the lead, how close the grids are, variations in how straight the grids are, and even acid along with chemical reactions that have taken place from charge/discharge cycles not to mention possible stratification of the electrolyte. Everything also ages at different rates which can affect the SG between cell to cell.

Unless you want to spend $5K for a digital Hydrometer (they DO exist) your going have a difficult time to achieve the high accuracy you are after and even then, what if anything can you really do to correct the small insignificant variances you will see?

I am sure Mex knows a few tricks, but one must ask themselves, is the hassle to gain 2 minutes of battery run time worth the hassle and aggravation of jumping through a lot of hoops?

Batteries are a "consumable" item, use it and it is consumed, has a finite life and as such it wears out and you replace it with new and start the cycle over.

If I can see my SG dropping from 1.30 or so down to 1.275 I know it's time to start looking for new batteries but still have life left. The advantage of a quantitative tool.
If all I know is it is above 1.25, I won't know it's time to look for batteries until they are pretty close to needing replacement soon.

Qualitative and Quantitative tools, both very useful and valuable.
Yours is a great one for a quick check of a battery if one suspects an issue or see if batteries are charged.
checking SG with more resolution can give a better idea of overall battery "health" and if it's starting to go.
Both good tools to have in the toolbox.

[Gdetrailer]

ktmrfs wrote:

Gdetrailer wrote:
All I have ever used for batteries is the simplest, cheapest "ball" type in a tube Hydrometer..

Sort of like this one..



All of the balls rise, the battery is fully charged..

Simple, cheap and effective.

These work ok to tell if a battery is well on it's way out, but not real good at an accurate SG cell to cell comparison. And all balls rise usually means SG is between about 1.250 and 1.300, a pretty noticeable difference in battery real condition.

But yes, they will tell you if you've got a cell or battery heading south.

Sort of splitting hairs to find the "holy Grail" of perfect in an imperfect world.

There will always be some small discrepancy between cells, trying to achieve the exact same ideal 1.300 on every cell is pretty much a futile effort.

The discrepancy comes from slight differences in grids, how they are molded (grids can vary due to how much flash there is left after the molding) and composition of the lead, how close the grids are, variations in how straight the grids are, and even acid along with chemical reactions that have taken place from charge/discharge cycles not to mention possible stratification of the electrolyte. Everything also ages at different rates which can affect the SG between cell to cell.

Unless you want to spend $5K for a digital Hydrometer (they DO exist) your going have a difficult time to achieve the high accuracy you are after and even then, what if anything can you really do to correct the small insignificant variances you will see?

I am sure Mex knows a few tricks, but one must ask themselves, is the hassle to gain 2 minutes of battery run time worth the hassle and aggravation of jumping through a lot of hoops?

Batteries are a "consumable" item, use it and it is consumed, has a finite life and as such it wears out and you replace it with new and start the cycle over.

[ktmrfs]

Gdetrailer wrote:
All I have ever used for batteries is the simplest, cheapest "ball" type in a tube Hydrometer..

Sort of like this one..



All of the balls rise, the battery is fully charged..

Simple, cheap and effective.

These work ok to tell if a battery is well on it's way out, but not real good at an accurate SG cell to cell comparison. And all balls rise usually means SG is between about 1.250 and 1.300, a pretty noticeable difference in battery real condition.

But yes, they will tell you if you've got a cell or battery heading south.

[ktmrfs]

wa8yxm wrote:
The fact the test results varied with the hydrometer suggests stratification.

Very common.

When I use a hydrometer I make sure to "stir" up the cell by filling the tube and flushing a few times. But yes there could be stratification.

What I experience the most is that the side of the hydrometer float likes to stick to the side of the glass and trying to get the float away from the glass is tough so it's hard to get what I feel is an accurate reading.

[wa8yxm]

The fact the test results varied with the hydrometer suggests stratification.

Very common.

[Gdetrailer]

All I have ever used for batteries is the simplest, cheapest "ball" type in a tube Hydrometer..

Sort of like this one..



All of the balls rise, the battery is fully charged..

Simple, cheap and effective.

[pianotuna]

ktmrfs,

Great to know. Mex is around but mostly on the pandemic thread.

I considered the refractometer and then replaced my batteries with agm.