Battery drop tester..

[doug748]

I suspect my house battery is losing capacity. Has anyone used one of these (available under different brand names Silverline, Sealy etc):

Clarke CVT2 12V Battery Tester - Machine Mart - Machine Mart

The reviews look ok, anyone used one on the boat? I would like to avoid lugging the battery for a test and it's nice to have an impartial idea of the state of things.

 

[LadyInBed]

Yes, it will do the job, it looks to be just the modern version of the device with two battery prods connected together with a low resistance high current bar and a voltmeter, held with wooden handles.

 

[Daydream believer]

I was concerned about the state of 2 agms that were only 15 months old & 3 months out of warranty. I found a tester as described above but with a better analogue scale as I felt the box type scales a bit inaccurate.
before blowing £ 60- 80( for the better quality unit) I decided to have a chat with the manufacturer/importer for an opinion of the best type. Was there a better way to test?
The chap said that I would be wasting my money & would be better sending the batteries back to the them. I felt this to be hassle, but I made up 2 separate parcels & they arranged a courier to collect.
They had them on cyclical testing for a couple of days & my phone call to them confirmed that they "within limits". However, when I described the use & importance of reliability on a yacht. They agreed (quite happily) to test for further deep cycles over a few days.

A week later I was sent 2 new batteries - even though mine were out of warranty. I also had a telephone call apologising re the quality of the batteries.
However, the point of my post is that the tech dept went into detail as to why the instrument above would be a waste of money in inexperienced hands. I forget the details, but it was worth sending them back & they paid all the costs of collection & delivery.

 

[PaulRainbow]

It's nothing like the one in post #2

It's rubbish.

Use a headlamp bulb and check over time. The process has been posted on her lots of times (bit pushed for time here or i'd re-post details).

 

[Skylark]

I have similar concerns regarding the capacity of my relatively recently installed domestic bank so I’ve made myself a drop tester. I plan to use it in the next couple of weeks when I next visit the boat.

It is simply a pair of car 55w, H7 lamps in holders and a couple of croc clips. I have a DC amp clamp meter. It should consume 8-9 amps and the wires are rated at 15 amp. Cost less than a fiver.

 

[vyv_cox]

I do not pretend to know a great deal about batteries but I have read that leisure-type batteries should not be subjected to direct short drop testing as it will distort the plates.

 

[Tzu]

I'm no battery testing expert either but more than happy enough with my Amazon bought tester.

 

[Boater Sam]

The only way to establish battery capacity is to fully charge then controlled discharge at the prescribed rate of the battery, usually the 20 hour rate , and measure the time to the half charged state.

 

[William_H]

I do not pretend to know a great deal about batteries but I have read that leisure-type batteries should not be subjected to direct short drop testing as it will distort the plates.

As I understand from the name a "leisure " battery is a compropmise between deep cycle for long term low current drain and high current engine start. So should be ok for volt drop test. Even large deep cycle battery should be ok especially if you need to use deep cycle house battery for emergency engine start where the tester emulates an engine start.
However the simplest way to test a battery for high current capability is to use it to crank the engine. The enthusiasm of the cranking is a sure sign of battery health and so capability of doing the job. As said however the other failure mode of a battery is it's actual capacity in amp hours. This will deteriorate over time but you should get some idea of impending failure as you monitor voltage with service loads on. ie how long will the fridge run before battery voltage falls. In other words will itstill do the job you need it to do? Or do a specific discharge over time test. ol'will

 

[Refueler]

I do not pretend to know a great deal about batteries but I have read that leisure-type batteries should not be subjected to direct short drop testing as it will distort the plates.

True leisure batterys have soft plates and do not appreciate it ...

 

[Refueler]

As I understand from the name a "leisure " battery is a compropmise between deep cycle for long term low current drain and high current engine start. So should be ok for volt drop test. Even large deep cycle battery should be ok especially if you need to use deep cycle house battery for emergency engine start where the tester emulates an engine start.
However the simplest way to test a battery for high current capability is to use it to crank the engine. The enthusiasm of the cranking is a sure sign of battery health and so capability of doing the job. As said however the other failure mode of a battery is it's actual capacity in amp hours. This will deteriorate over time but you should get some idea of impending failure as you monitor voltage with service loads on. ie how long will the fridge run before battery voltage falls. In other words will itstill do the job you need it to do? Or do a specific discharge over time test. ol'will

I'[ve lost count of the number of people I know who have ruined a 'leisure battery' cranking medium / larger engines ........ it may be ok on a 10hp or so ... but not on large.

Trouble with batterys - the RV Leisure industry has brought about the confusing middle ground Leisure battery that is supposed to be able to survive engine starts - but not repeatedly. Personally ... I don't like them - but that's me ... the difference in charge level you can use out of them compared to a decent cranker battery is not worth it IMHO.

 

[Refueler]

I suspect my house battery is losing capacity. Has anyone used one of these (available under different brand names Silverline, Sealy etc):

Clarke CVT2 12V Battery Tester - Machine Mart - Machine Mart

The reviews look ok, anyone used one on the boat? I would like to avoid lugging the battery for a test and it's nice to have an impartial idea of the state of things.

Many years ago - I bought a simple pocket LED Drapers battery / alternator tester .... people laughed at it when they saw me with it ... but its actually earned its keep .... it showed when my alternator was faulty ..... its shown when batterys have fallen off shortly after charge ....

It does not do as they claim - give you full picture - but what it does has been good enough.

Battery and Alternator Analyser for 12V DC Systems

 

[LadyInBed]

It's nothing like the one in post #2

It's rubbish.

Please explain why it doesn't fulfill the function of the old tester that I showed in #2, and what makes it rubbish, as I can't work it out from it's spec sheet.

Use a headlamp bulb and check over time. The process has been posted on her lots of times (bit pushed for time here or i'd re-post details).

I agree that using the 20 hour rate for a deep cycle battery is the correct way, but
a) that wasn't the question asked, and
b) we don't know what type of battery is being used as 'house'.

 

[PaulRainbow]

Please explain why it doesn't fulfill the function of the old tester that I showed in #2, and what makes it rubbish, as I can't work it out from it's spec sheet.

It won't do the same as the one you posted, because it's an entirely different tool

It's rubbish because it will not do what it says it will and it won't do what the OP wants it to do.

I agree that using the 20 hour rate for a deep cycle battery is the correct way, but
a) that wasn't the question asked, and
b) we don't know what type of battery is being used as 'house'.

a) It doesn't matter if was exactly the question the OP asked, my answer is materially relevant to his needs and may save him wasting his time and money.

b) It doesn't matter what type of batteries the OP has, the best way to check the batteries used as a house bank is to test them over a period of time using a known load.

 

[LadyInBed]

Thanks Paul, most informative.

 

[Skylark]

A supplementary question, if I may.

Is there an optimum discharge rate for a capacity test?

Using one or two 55w car bulbs as a load, I will draw either 4.4 or 8.8 amps (approx).

Assuming 12.2v represents 50% SoC, my fully charged 110 AHr battery should reach this voltage after 12 hours with one bulb or 6 with two.

Does load current influence the result?

 

[MikeCC]

A supplementary question, if I may.

Is there an optimum discharge rate for a capacity test?

Using one or two 55w car bulbs as a load, I will draw either 4.4 or 8.8 amps (approx).

Assuming 12.2v represents 50% SoC, my fully charged 110 AHr battery should reach this voltage after 12 hours with one bulb or 6 with two.

Does load current influence the result?

Yes, a higher load will reduce the apparent capacity. Best to make the load something similar to your typical usage, so one bulb is probably more realistic.

 

[MikeCC]

And to repeat Paul's message a, a drop test for a battery being used as house supply is almost completely pointless.

If you want a cost-effective automated gizmo for constant load testing, look up ZKE kit.

 

[LadyInBed]

Is there an optimum discharge rate for a capacity test?

Have a read of this article
Understanding Deep Cycle Batteries - Part 2 | altE Blog

 

[davidej]

The only way to establish battery capacity is to fully charge then controlled discharge at the prescribed rate of the battery, usually the 20 hour rate , and measure the time to the half charged state.

How do you know when it gets to the half charged state? A particular voltage? If so, what voltage?