Battery testers

[brianl703]

I have a Harbor Freight 100 amp battery load tester that went bad. It won't apply a load to the battery anymore. I think the switch is bad. I wondered if it actually pulled 100 amps from the battery and I didn't think to try my clamp-on ammeter until after it died. Oh well.

I decided to replace it with a conductance tester I found on Ebay for $40 with free shipping, the KAL KM8100. This appears to be a new-old-stock discontinued model--the copyright date in the manual is 2001. Supposedly it was about $180 back then.

The KAL KM8100 doesn't have an LCD display. What it does have are three LEDS: Orange for "ready", green for "battery OK", red for "battery bad", two buttons "TEST" and "COLD TEST" (for testing a battery under 32F) as well as a dial to select the CCA of the battery in 25CCA increments from 350CCA to 900CCA.

To use it you set the dial to the CCA of the battery you're testing, hook up the cables, and push the TEST or COLD TEST button. If the battery is good the green light will come on. If it's marginal both the red and green lights will come on. If it's bad the red light will come on.

If you're wondering how good or bad the battery is, you can turn the dial until either the red or green light stays on.

For $40 it seems like a good tester. It seems accurate in that it can tell the difference between the 700CCA, 2-year-old battery in my Saab and the 650CCA, 3-year-old battery in my Mustang. The Saab battery is actually putting out 800CCA according to the test, while the Mustang's battery is only putting out 700CCA. (It's apparently normal for a battery to test above it's CCA rating when it's good).

Unfortunately, neither conductance testing nor load testing can give you an idea of the battery's reserve capacity, which is how long it can power a load without the engine running. It seems the only way to test that is to actually drain the battery down and see how long it takes.

There is only a weak correlation between a battery's CCA and it's reserve capacity. It seems very common for a battery to lose reserve capacity, yet still test OK for CCA.

 

[George7941]

I use a Midtronics PB200 Conductance Tester and find it useful.

The only problem I have with it is that it does not seem to be able to detect sulfation in batteries. I have the tester showing good CCA readings on batteries that were sulfated with little capacity left. So my experiences mirror yours.

They are useful for quick checks but I always back up with a load test if I have any doubts about a battery.

The cheap cheese-grater type of load testers that apply a 100 amp load for 15 secs is really not enough to detect a bad automotive battery. The load amps is supposed to be 1/2 CCA, so, you need a carbon pile load tester.

 

[punisher]

Originally Posted By: George7941
The load amps is supposed to be 1/2 CCA, so, you need a carbon pile load tester.


How I miss my old VAT40.

 

[brianl703]

Originally Posted By: George7941
I have the tester showing good CCA readings on batteries that were sulfated with little capacity left. So my experiences mirror yours.


I'm not sure capacity loss is always due to sulfation. Cold cranking amps is mainly determined by the surface area of the plates. The capacity is mainly determined by the thickness of the plates.

I believe capacity loss is caused by shedding of material from the plates over time.

There is definitely no correlation between CCA and reserve capacity, looking at the Interstate Batteries spec sheet.

http://www.interstatedealers.com/ibcatalog_07/common/spec_sheets.pdf

 

[George7941]

Hi, Brian.

Do you know when material is shed from the plates, is it mainly lead or is it mainly lead sulphate? If lead sulphate, then it would lead to lower specific gravity of the acid in the battery when fully charged.

 

[brianl703]

I don't know if it's mostly lead or lead sulphate. I do know that more material is shed from the plates the deeper you cycle the battery, particularly for starting batteries (they just hate that kind of use). That seems to suggest it may mostly be lead sulphate.

 

[George7941]

The reason I asked the question goes back to an old thread of mine

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1093449&fpart=1

I have these failed batteries with good concentration of acid (1.25 and 1.26) in them, so the failure was not due to sulfation. If lead sulpate had been shed that would also have weakened the acid. Only if lead had been shed would the acid retain its strength.

 

[Donald]

Have you tried a battery charger with one of the anti-sulphuation circuits built into it?

You could also email the people at Battery Minder with your question and they might know the answer.

 

[Donald]

Originally Posted By: brianl703
I have a Harbor Freight 100 amp battery load tester that went bad. It won't apply a load to the battery anymore. I think the switch is bad. I wondered if it actually pulled 100 amps from the battery and I didn't think to try my clamp-on ammeter until after it died. Oh well.

I decided to replace it with a conductance tester I found on Ebay for $40 with free shipping, the KAL KM8100. This appears to be a new-old-stock discontinued model--the copyright date in the manual is 2001. Supposedly it was about $180 back then.

The KAL KM8100 doesn't have an LCD display. What it does have are three LEDS: Orange for "ready", green for "battery OK", red for "battery bad", two buttons "TEST" and "COLD TEST" (for testing a battery under 32F) as well as a dial to select the CCA of the battery in 25CCA increments from 350CCA to 900CCA.

To use it you set the dial to the CCA of the battery you're testing, hook up the cables, and push the TEST or COLD TEST button. If the battery is good the green light will come on. If it's marginal both the red and green lights will come on. If it's bad the red light will come on.

If you're wondering how good or bad the battery is, you can turn the dial until either the red or green light stays on.

For $40 it seems like a good tester. It seems accurate in that it can tell the difference between the 700CCA, 2-year-old battery in my Saab and the 650CCA, 3-year-old battery in my Mustang. The Saab battery is actually putting out 800CCA according to the test, while the Mustang's battery is only putting out 700CCA. (It's apparently normal for a battery to test above it's CCA rating when it's good).

Unfortunately, neither conductance testing nor load testing can give you an idea of the battery's reserve capacity, which is how long it can power a load without the engine running. It seems the only way to test that is to actually drain the battery down and see how long it takes.

There is only a weak correlation between a battery's CCA and it's reserve capacity. It seems very common for a battery to lose reserve capacity, yet still test OK for CCA.


I would also consider the variable load tester from HF. You really want to put a 1/2 CCA load on the battery for 15 seconds and see the final voltage (temp compensated).

Maybe the best of both worlds is a load test and a conductive test.

 

[George7941]

I am a bit sceptical of the high frequency anti-sulfation circuits. I have never come across any proof that they actually work.

 

[SHOZ]

The material that gets shed is led sulfate. And yes it will lower the sp gravity (which reduces capacity) over time as well as reduce capacity by way of less material. It will also lead to an accumulation of junk at the bottom of the plates which may short the cell out depending on the separator design.

Deslufation only causes shedding as the lead sulfate chemical reaction is not reversible.

 

[George7941]

Shoz, check out my post about five posts back of this one.

If sulfation weakens the electrolyte and shedding also weakens the electrolyte, why do I have two batteries with very low capacity and yet have strong acid in them?

 

[kgb007stb]

When we buy new batteries, we expect the specific gravity to be around 1280 on all 6 cells. As the battery goes through a discharge process the electrolyte is converted into electricity through a chemical reaction between the plates and electrolyte. As a result of the electron shedding, or the battery doing work, energy is produced causing the specific gravity of electrolyte to decrease. As the lead plates react with electrolyte they become loaded with sulfide crystals, often referred to a sulfation on discharged or old batteries. As the discharge cycle progresses, sulfide crystals become larger taking up more space on the plates, as a result the growing crystals tend to expand the plate with it. The expanded plate, already sandwiched under pressure to resist vibration has no room for expansion, thus it starts to buckle or bend in wave forms like when crushing a can. As discharge progresses to a very deep state, the crystals grow so large and the buckling is so great that the deformation of the plates causes these crystals to fall to the bottom of the battery as mud. This mud is irreversible damage that cannot be converted back to electrolyte as it cannot undergo hydrolysis when energy is applied. As crystals take up space on the plates, they reduce the CCA as the battery exhibits greater resistance than normal. Electrolyte solution become weaker, it too exhibits greater resistance thus dropping the CCA of a battery. These two factors combined are the greatest contributors in determining whether a battery will perform as it should.

Now we apply a charging current to reverse the chemical process and recharge our battery. Deep discharger batteries do not like great currents due to high internal resistance, the plates and the weak electrolyte. In charging our sulfate crystals break down and reverse back into electrolyte or active solution. As the breakdown occurs, crystals that once expanded and stressed our plate into buckling is reversed into contraction and unbuckling. If all goes well, we should reach our ideal 1280 specific gravity, all crystals convert back to active material, and we should see unbuckling of out plates with some hydrogen gas bubbles escaping to the surface. The reality is that plates do not like to be mechanically stressed, some older batteries exhibit plates in wave like form, the permanent expansion stress that is non-reversible. Sulfate crystals, over time harden and are harder to break back into electrolyte. What usually happens on older sulfated batteries, heat dissipation and excessive gassing due to a battery not being able to convert sulfate crystals back to active electrolyte. Chemistry tells us that no chemical reaction, no matter how violent it may be, is complete. What this means is that when we take a battery at 1280 specific gravity, fully discharge and recharge, under ideal circumstances we will have a specific gravity of less than 1280, hence the reason why all batteries, not just car batteries go bad over time.

Reserve capacity is a beast onto itself, the problem with reserve capacity is that the more I drain a battery the less RC it will exhibit, while the less drain I put on a battery the more RC it will tend to have. The problem with RC lies in how batteries work on the most basic fundamental principle. One factor is the I-squared R loss, meaning that a battery will dissipate heat depending on its rate of discharge/recharge. As we discharge a battery Resistance goes up due to plate sulfation and weakening electrolyte. Batteries discharged at a high rate will give off more heat (I-squared) than those discharged with a weaker current. Also remember that in order for batteries to work properly, the ions must flow freely in the weakening electrolyte solution. When we apply a great discharge rate, the electrolyte near the plates becomes exhausted hence the reason why batteries under start conditions tent to seem to lose power where as batteries that are discharged slowly, such as a laptop will tend to exhibit more reverse capacity as when discharged electrolyte has more time to mix and provide the energy needed.

George, as for batteries with 1260 or 1250 solution misbehaving, they could have an internal cell short, they could have been deeply discharged, rapidly recharged, stressed through vibration, some manufacturing defect, electrolyte contamination, or other unknown factors that could contribute to its demise. Batteries tend to be more complicated than people give them credit.

Desulfation products, I am testing one very hated brand on these boards with good results so far. The problem with many batteries pre-maturely failing is that people buy cheap Chinese chargers that tend to overcharge or undercharge batteries, yes a cheap Chinese charger can be used to safely re-charge a battery, but one has to monitor a battery with at least a volt meter to compensate for over or under charging.

I’ve been also playing with a Midtronics tester that seems to make very good calls on new charged, new sulfated, new discharged, old sulfated, and old discharged batteries. I will still have to perform more tests to confirm my results, as for reserve capacity, it is as relevant as CCA, let’s not confuse RC as absolute. European car manufacturers tend to push the RC ratings on all batteries, while here in the stares we like the CCA ratings.

 

[brianl703]

Originally Posted By: Donald

I would also consider the variable load tester from HF. You really want to put a 1/2 CCA load on the battery for 15 seconds and see the final voltage (temp compensated).


I've thought about that one, but I wonder if it's going to last any longer than the 100 amp one I got that doesn't work anymore. For $50 though I guess it's not too much of a gamble.

 

[brianl703]

Originally Posted By: kgb007stb
European car manufacturers tend to push the RC ratings on all batteries, while here in the stares we like the CCA ratings.


All the car batteries sold in Europe have amp-hour ratings on them (as well as CCA ratings), while I see batteries that don't even have a reserve capacity rating on them (neither of the two Kirkland Signature batteries I bought have reserve capacity ratings on them).

If you do have a reserve capacity rating (in minutes), according to Johnson Controls you can multiply it by .6 to get the amp-hour rating.

It's no wonder why European manufacturers push reserve capacity--my Saab 93 is an electrical power hog. It consumes 8 amps from the battery with the key in the "OFF" position (basically the accessory position).

 

[George7941]

The first thing I did when I bought my 100 amp load tester many years ago was to replace the momentary On switch with a 30amp DPST toggle switch (DelCity). The OE switch that comes with the tester doen't seem to be any more than a 30 amp switch. I used the 2 pole switch so I could wire the poles in parallel to double the capacity to 60 amps and this switch has been able to handle the 100 amp load. I keep the tester on for about 50 secs at a time (any more and it starts to burn the white insulator sheets holding the element up. The ability to leave the tester on while you go check something else is very useful.

A burnt-out switch is the most likely problem with your load tester. The element almost never burns out.

 

[George7941]

The 0.6 factor in RC x 0.6 = AHr is a little surprising. GM had a TSB out many years ago publishing the same 0.6 figure.

I did a sample calculation using a typical heavy truck battery - Group 31, with a RC of 180 mins.

25 amps for 180 mins = 75 AHr.
180 x 0.6 = 108 AHr.
108 AHr translates to 5.4 amps over 20 hrs (the North American standard for AHr rating is a 20 hr discharge period).

So, discharging the battery at 5.4 amps gives 108/75=1.44 times as much total output as discharging the battery at 25 amps. Didn't know that the figure was that high.