Battery Testers

[TernVI]

Before you test a battery 'to see if it's OK' you need to decide what 'OK' is.

For a car battery, the main things you want are enough capactiy to power the alarm and other background loads for say a fortnight, and enough cranking amps to turn the engine.
You can either test that with a starter motor and a volt meter, or a high current tester. A clamp meter to see the current is also good.
By the time car batteries become 'suspect' they are usually a very long way from their new performance, and there isn't much in the way of grey areas, its performance is dropping by the month.
Mostly you need a good charger, so you can prove the problem is the battery not the charging side.


For a boat's house battery, you mostly want to know its capacity and maybe self discharge.
I would test the capacity by taking 10 or 20A and looking at the voltage over an hour or two.

But what are the pass/fail criteria? We've happily got another season out of batteries which have lost 30% capacity and discharge themselves noticeably if you leave them for a month. They're Ok for what we need, but I wouldn't set off on a world cruise with them.....

AIUI, the complex electronic chargers can determine the AH capacity of a battery, and lots of other characteristics by doing a few measurements very quickly at different current levels. That's what you want in a commercial situation, I don't need that. I need to know how long it will run the fridge or nav lights for, and whether that's much worse than last year.

 

[MikeCC]

After all that agony, you just need a ZKE EBD-A20H - about £70. That may or may not seem good value to you.

 

[Rappey]

Some change their dyneema rigging every year regardless, others change their batteries evey 3 years regardless. the advantage of the electronic testers is that they can still rate the battery even when flat.. There have been some very expensive and near perfect batteries thrown out many times over..

 

[William_H]

If you look at lead acid batteries across the world there are a huge number used in cars trucks etc primarily for engine start. On this forum we are also interested in deep cycle battery performance. This concern is but a tiny fraction of the world use of lead acid batteries. hence manufacturers of testing are concerned with testing a car battery. (et al) ie capacity to provide a huge short term current. Just from shear numbers they can ignore concern re capacity to provide a load over a long period.
Now any car or boat with engine for that matter has a built in battery tester. All you have to do is listen carefully to your starter motor when it cranks your engine especially from cold after a period of no charge. Energetic (normal) cranking is a good battery, sluggish cranking is bad battery. (meaning soon to fail to do the job)
Regarding capacity to provide current for long period. Yes you can get a discharge tester as depicted above. it has a constant current load (hence the fan to cool it) and a clock to time it up to auto shut off. But in reality on your boat (or off grid home) you will soon know if battery has lost it's capacity by premature volt drop. Calculations of actual capacity in AH will probably dismay you. 50% of claimed capacity is probably quite good. Just replace or add top if it won't do the job. Forget any tester beyond a volt meter. ol'will

 

[KompetentKrew]

All I really want to establish is the current state of my batteries as a base line for their future state.

What criteria of battery performance should I be looking at to determine the current condition of my batteries and what test equipment that doesn’t cost an arm and a leg, could I look at?

Take them to the local battery shoppe.

As per previous threads, Plymouth Battery Centre have a professional tester that performs the test over a discharge time of about 4 hours. I imagine that this shows the battery's condition with "good enough" accuracy even without temperature-controlled conditions, and that most battery specialists must have access to similar equipment these days.

 

[Ian_Rob]

Take them to the local battery shoppe.

As per previous threads, Plymouth Battery Centre have a professional tester that performs the test over a discharge time of about 4 hours. I imagine that this shows the battery's condition with "good enough" accuracy even without temperature-controlled conditions, and that most battery specialists must have access to similar equipment these days.

I will probably do just this but I am on a swinging morning and if there is affordable test equipment that actually works it would have been a lot easier.

Thankyou

 

[TernVI]

I will probably do just this but I am on a swinging morning and if there is affordable test equipment that actually works it would have been a lot easier.

Thankyou

If you want an affordable test, all you need is a few car headlight bulbs a multimeter and a graph of volts against % state of charge.
https://www.scubaengineer.com/documents/lead_acid_battery_charging_graphs.pdf

If it's a nominally 100Ah battery, take about 10A from it and plot the voltage over a couple or 3 hours.
It usually doesn't take long to see if the capacity is well down on spec, or if one battery in a bank is much weaker than the others.

Like all simple load tests, it's very much clearer if you start knowing the battery is 100% charged.
When I kept boats on a swinging mooring, I used to take the batteries home for a thorough 12 hour charge once or twice in the winter, until we got enough solar to not need this.

 

[GHA]

Take them to the local battery shoppe.

As per previous threads, Plymouth Battery Centre have a professional tester that performs the test over a discharge time of about 4 hours. I imagine that this shows the battery's condition with "good enough" accuracy even without temperature-controlled conditions, and that most battery specialists must have access to similar equipment these days.

Any idea what current draw was used?

At least it's some useful real data.

 

[Alfie168]

Shows up duff cells pretty quick though.

I have an antique Heavy Discharge meter. Two asbestos plates sandwiching a heavy coil and passing through a voltmeter. Spring loaded pivoting prongs for the terminals fitted with wooden handles.

Dont 'alf get 'ot!

I have had it since the mid seventies.

A heavy discharge tester is predominantly used for testing starter batteries.

Not much use for anything else.

A similar device could be seen lurking in the back of many a workshop back in the 60s and 70s. I'm sure there's quite a few still out there.

 

[rotrax]

Take them to the local battery shoppe.

As per previous threads, Plymouth Battery Centre have a professional tester that performs the test over a discharge time of about 4 hours. I imagine that this shows the battery's condition with "good enough" accuracy even without temperature-controlled conditions, and that most battery specialists must have access to similar equipment these days.

There speaks one of little experience in installing/removing/transporting 660AH of Marine bateries.

My bank weighs in excess of 150 Kilos and is located in the bowels of the vessel. In a bloody great box with bars, a heavy lid and little clearance above - just enough to get a battery out.

Far easier, quicker and less physically demanding to take the instrument to the battery bank............................

 

[rotrax]

A similar device could be seen lurking in the back of many a workshop back in the 60s and 70s. I'm sure there's quite a few still out there.

Absolutely - not much to go wrong and still does a very useful job in finding a bad cell or cells.

I shall not be disposing of mine.

We arrived in NZ three years ago to find our elderly Mazda Premacy had a flat battery.

The AA guy came and tried to start it with a micky mouse starter pack, no joy. He condemmed the then 9 year old OE Battery after connecting a funny looking gauge to it.

Conveniently, he had a battery on board at 180 NZ Dollars.

I asked him to put his Toyota van alongside and I used my own good jump leads to get the Mazda going.

He, disgruntled, left. The Mazda is still going with that battery three years on, our son using it when we are not there.

As others are saying, a short sharp high discharge is very different to an insidious constant drain.

Different battery for different uses. Athough our boat had as OE USA made 'Lifeline' batteries, spiral wound AGM's, used both as the house bank and for starting.

The previous owner replaced three, two of the OE's checked out perfect and I added a cheapo spiral wound Chinese AGM for the genset starter.

Touching wood as I type, faultless performance so far.

 

[PaulRainbow]

I will probably do just this but I am on a swinging morning and if there is affordable test equipment that actually works it would have been a lot easier.

Thankyou

Why not do what i, and others, have said, use a headlamp bulb, or two, to measure the discharge rate/capacity ?

Fully charge the batteries and let them rest for a while.
Note the voltage.
Apply a known load, two headlamp bulbs are near enough 10 amps.
At hourly intervals disconnect the load, leave for 15 mins and note the voltage.

You can do the test in a few different ways, for domestic batteries, you could let the batteries drop to a given voltage to see what usable capacity they have. Divide the capacity of the bank by 20 to give you your load. Apply that load and periodically note the voltage, as above. When the rested voltage gets to 12.2V the batteries will be at 60% SOC. Depending on how long it took to get to 12.2V will tell you all you need to know.

 

[MikeCC]

Why not do what i, and others, have said, use a headlamp bulb, or two, to measure the discharge rate/capacity ?

And for the naysayers, it's not usually too tricky to go into marina for a day to get shore power to fully charge before/after test. Just use a good multistage charger, not an agricultural type.

 

[Tanqueray]

Cue a thread about the accuracy of headlight bulb power consumption manufacturer claims.
Hella v Lucas v Rocna - the final showdown.

 

[migs]

We had a battery that ran a 380A bowthruster ok. When tested with a steady 10A discharge it had only 6Ah capacity (was supposed to be a 110Ah battery).

Just follow PaulRainbows advice on testing batteries. Perhaps should be a ‘sticky’ as the same old subject seems to crop up with monotonous regularity…

 

[KompetentKrew]

Any idea what current draw was used?

At least it's some useful real data.

No idea. Because a scale is given, I guess one could figure it out based on the upper dotted line on the chart, which presumably indicates the ideal discharge of a new battery.

Label in the top left indicates the tester is made by www.Emrol.com