Battery load tester

[JDCAVE]

Is a cheap analog load tester sufficient for once or twice a year tests or should I consider a digital model? Also, are 6v FLA GC’s with their high amp hour rating a special case? There are some models that indicate they can test 6 and 12 volts, but others just indicate they are for 12v batteries and do not specify otherwise.

Suggestions?

Jim

 

[RT Firefly]

Greetings,
Mr. JD. I may not know any better but I use one like this:
https://www.harborfreight.com/100-amp-612v-battery-load-tester-61747.html

 

[psneeld]

Unless you find some miracle digital one, I have had better results with the analog ones as they are simplistic.

None has ever lied, but 2 digital ones, including an expensive one at a place of work did.

 

[dhays]

What are you actually trying to test? It was my understanding that a typical load tester will test a batteries ability to produce cold cranking amps. That would be good for a start battery but how useful is that for testing deep cycle batteries such as used for a house bank?

 

[psneeld]

What are you actually trying to test? It was my understanding that a typical load tester will test a batteries ability to produce cold cranking amps. That would be good for a start battery but how useful is that for testing deep cycle batteries such as used for a house bank?

The digital ones may let you check 20 amp hr draw....

But even the stone age ones let you know if your battery has any guts left in it...just no accurate number to associate with deep cycle numbers.

But voltage tells you even less, much less....

 

[JDCAVE]

If you are trying to judge the State of Health of a deep cycling House bank, all these are close to useless.

Short of big lab-grade gear costing thousands,

only a 20-hour load test will be accurate for that purpose.

A truncated version, **if** executed exactly the same every time, would be pretty close, providing you executed a benchmark run in the early days after properly commission-charging and breaking in the bank,

if well-coddled, say within the first 50 deep cycles.

Which is why I asked that question.

Jim

 

[jungpeter]

Hi JDCAVE,

Unfortunately, there's no easy way to measure battery "health" accurately for deep-cycle house batteries, unless you wish to resort to laboratory-grade test equipment, and rigorous test procedures, executed immediately after purchase, and executed routinely thereafter. Digital/analog handheld el-chepo battery conductance testers (ESPECIALLY Harbor Freight versions, for instance) are simply a waste of money and time, and I have to agree with john61ct. For reference, you may want to read:

https://marinehowto.com/are-battery-conductance-testers-worth-it/

Regards,

Pete

 

[tiltrider1]

If you are trying to test your start battery, the battery must be full charged first for the resistance style battery testers to work correctly. The new digital ones don’t require a fully charged battery to do their test. The digital battery testers will give you much more data but most just want to know if the battery is good or not and could careless about how good or bad the battery is. Be careful, there are some resistance style testers with digital displays.

 

[caltexflanc]

For deep cycle batteries, I far prefer a good battery monitor system. For start batteries a decent load tester works fine.

 

[DDW]

But any good AH counter can be used to *determine* the capacity of the battery. The only thing the %SOC number is used for is to display a number for the amusement of the user. All you need to do is observe the voltage at particular points of AH usage, and the capacity will reveal itself. For example, if your 200 AH (advertised) bank drops to 11.5V after 100 AH have been drawn from it, you've got closer to a 100 AH bank now.

This is not true of the resistance type testers discussed above. In fact they reveal very little that can't be seen with a cheap voltmeter and a heavy load.

Western Mountain Radio makes some very nice testers, but for a 400 AH battery bank you really need the 500W version and that's around $1K. If you can break your bank into 200 AH pieces, the $160 one will do it one at a time.

 

[BruceK]

Greetings,
Mr. JD. I may not know any better but I use one like this:
https://www.harborfreight.com/100-amp-612v-battery-load-tester-61747.html

I bought one of those. The load test is complete when you smell smoke. Despite the criticism, I think it achieves purpose.

 

[psneeld]

I bought one of those. The load test is complete when you smell smoke. Despite the criticism, I think it achieves purpose.

I agree with the backyard mech evaluation/perspective...just have to have an eye and an ear for that sort of thing. Accuracy? Heck no but does tell you something.

Plus one may have one around FOR starting batteries, etc.

As has been posted, without an involved test, you don't know exactly, so rule of thumb tests that are easy work for me.

 

[FF]

The golf course folks have an expensive unit that can give a snapshot , charged or discharged , but there pri$y.

Just as you would not use a single oil sample to judge an engine , installing a SOC meter can keep track over time of the battery sets condition.

A long history is better than a snap shot.


On buying a boat , just plan on replacement in time.

 

[ghost]

I’m not sure what the digital ones that form an opinion in a moment are doing. The hf auto shop ones are simply applying a load and watching a volt meter to see if the voltage drops under load. Actually they are pretty effective for a bad battery, good/bad outcome. But don’t do squat for measuring the amp hour capacity.

I used to test amp hour loads for a 12 volt 18 amp hour battery set when we absolutely had to know if it was going to last for its intended use. I had a set of large resistors of known value that I would bolt or clamp to my metal bench. Then connect them to the battery. The resistance would pull around 20 amps if I recall. I’d let the. Go until they hit a specified voltage. You could chart the voltage every 10 minutes or so. Interesting part was the characteristics of the “bad” ones. Some would have the same curve as when new, just a little lower. Others would go along looking just a little lower than normal and then fall off really quickly. I’m leery of any device that samples just a few minutes to form its conclusion.

Oh, and those huge resistors would get hot enough to heat my shop. To do my current 1200 amp-hour house bank would take considerable time and for most, the heat would be dangerous enough to require some thought.

To test amp hour capacity at this scale, typically can’t practically be done in place. It’s possible, but very few would pull it off safely. Plus if you did not test and plot when new, you have little to compare to.

My soc meters get reset occasionally, call me skeptical. Maybe if they took the voltage at repeated soc points, but they are all different. Sometimes the batt has been fully charged, other times not. Sometimes there are background loads. Too many variables. Helpful, but I’m skeptical this accurately approximates a real amp hour test.

 

[ghost]

Pragmatic me would not vary the load. Only reason to do that is if you are the mfg and trying to publish a statistic. The value to an individual would be better served to establish their own baseline with a load that is consistent each test, thus a fixed resistive load answers perfectly. The value is then plotting at a future date and establishing how much capacity has been lost would be the goal. Keeping the test consistent would be the hardest part.

 

[Roamer Blue]

Quick learning curve with these, use it a bit, on new and old batteries, you'll have a good idea whether there's some "oomph" left, or if it is getting tired. Your car, the neighbor's car, the kid's car, passers by, down by the grocery store on "cheque day" for some rougher examples... One battery at a time please... see what will hold the needle high, and what will get it to degrade over the 10 seconds of test time...And then extrapolate your learning for the deep cycle power houses...


Type A personality, OCD, engineers may now blow their brains out at this completely seat of the pants foolishness that lacks any scientific content whatsoever... but I've still only spent what? $24 on Amazon? and test each battery in 10 seconds...

Greetings,
Mr. JD. I may not know any better but I use one like this:
https://www.harborfreight.com/100-amp-612v-battery-load-tester-61747.html

 

[psneeld]

Exactly....

 

[alfamike]

Battery Testers

I use the newest Midtronics tester.

it does test for reserve capacity.

Alfa Mike

 

[RT Firefly]

Greetings,
Mr. RB. Thanks for that. I was feeling pretty dumb for posting MY test equipment but all I really want is to see, as you put it, the "oomph". Will continue in lieu of UL labs....

 

[BruceK]

Greetings,
Mr. RB. Thanks for that. I was feeling pretty dumb for posting MY test equipment but all I really want is to see, as you put it, the "oomph". Will continue in lieu of UL labs....

Well don`t, several of us own that basic device and it does tell us something that is adequate for many purposes. If you have LAs nothing really takes the place of a hydrometer for testing for battery condition, and hydrometers cost only 3/8 of 5/8 of not very much.

 

[psneeld]

Plus.....cruising isn't bench testing....you live with your experience as your guide, hoping to keep things in order as long as you can.

It's like taking IR readings of an engine as your cruising as opposed to checking compression, injector patterns, oil analysis...etc..etc every day to check the health of your engine.

While an IR gun won't tell you exactly the engines health, a T r ained eye can surmise a lot from some random readings.

 

[RT Firefly]

Greetings,
I test with hydrometer as well.

 

[AusCan]

As I’ve given up on the old lead acid batteries, my hydrometer hasn’t been used for years.
I find that just monitoring the voltage of battery banks keeps a person aware of the battery condition. My voltage is always displayed at the helm and it is the first thing I look at when I visit the boat. I take into account whether the battery is on charge and/or what loads are on and that tells me the condition of the battery bank.

 

[DDW]

While we are at it:

"The only way to determine [the capacity] accurately is to conduct a 20 hour capacity test." - FALSE

A 20 hour capacity test is one way to determine the health of the battery, but certainly not the only way. It is a test unavailable to most boat owners, and damaging to an LA battery if repeated often.

Resting voltage provides a reasonable estimate of state of charge in an LA battery. State of charge after a known number of AH extracted tells you the functional capacity. This is something any boat owner with an AH counter (which should be all of 'em) can do, every day. The accuracy will not be as good as a 100% discharge test, but it will be perfectly adequate to determine replacement time, takes little to no effort, and can be repeated without damaging the battery.

 

[HopCar]

When I was selling batteries I had a tester that was just a double throw switch, a couple of leads and a display.

If a customer wanted a battery tested and it was under warranty, I’d throw the switch to the right. The display would say “Good”.

If the battery was out of warranty, I’d throw the switch to the left and the display would say “Replace”.

Just kidding! Please don’t kill me.

 

[psneeld]

Well, I do agree the 20hour test is what people should do...but most if us have lives, and replace batteries if need be and generally take good care of them I hope, but maybe not perfect care.

My theme is, my batteries exist for me, not me for the batteries so they get plenty of though but action is split with a lot of other demands.

 

[BrianSmith]

I bought one of those. The load test is complete when you smell smoke. Despite the criticism, I think it achieves purpose.

Ditto. I had two start batteries that were only about 2 1/2 years old, but I suspected one of them was bad. This load tester showed a very, very obvious difference in the two that confirmed my suspicion.

 

[Roamer Blue]

My theme is, my batteries exist for me, not me for the batteries so they get plenty of though but action is split with a lot of other demands.

Smartest fellow on the internet this morning!


I got better stuff to do with mind and body...

 

[DDW]

Balmar has been selling the Smart Gage for some time, claims better than 5% SOC accuracy measuring only voltage (no shunt). Maine Sail has tested and likes it. I believe his argument is that most boat owners will not understand, install, and calibrate a true AH counter properly, so a dumb gage is better.

For my use, SOC is of little value. I want to know how many AH I am down, which tells me how much I have used and how much I need to replace. Also current usage or replacement rate. An auto calculating SOC does not provide that information: 50% of a new 200AH battery is 100AH, the same battery 5 years later might be 50AH. The devices on my boat consume and produce amps, not %SOC.

 

[High Wire]

When I was selling batteries I had a tester that was just a double throw switch, a couple of leads and a display.

If a customer wanted a battery tested and it was under warranty, I’d throw the switch to the right. The display would say “Good”.

If the battery was out of warranty, I’d throw the switch to the left and the display would say “Replace”.

Just kidding! Please don’t kill me.

Sounds like the old vacuum tube tester the TV repairman used to bring. Never saw a used tube it liked.