Battery Tester

[Mistroma]

How would you use a hydrometer on a sealed battery?

lw395, What are the top brands in meters?

Very many "sealed, low maint." batteries have a label over the plugs. It is often just a matter of removing the label and then unscrewing the plugs. Worth a try as first thing you need to check is the electrolyte level if your are worried about battery performance.

I use a Hydrovolt hydrometer to measure Specific Gravity, much better than the ones Halfords sell and it automatically compensates for temperature.

http://www.ebay.co.uk/itm/Pro-Hydro...y-Hydrometer-Electrolyte-Tester-/322082591860

I also use a clamp meter and also have a spare multi-meter. It took a while to find a reasonably priced clamp meter able to handle DC Amp. I think that it cost £35 and accuracy seems OK with 2-3A upwards but this type isn't meant to measure 0.1A. I think it was a Tenma model from Rapid Online but it is discontinued.

Built in systems monitor current and voltage, plus Smartgauge for ongoing State of Charge indication in conjunction with the other kit.

I'd agree that the item you first asked about isn't really much use for a domestic battery bank.

 

[Venus1]

But we still might want to know capacity ie ability to supply a low/medium current for a long time. The only way to test this is to discharge with a current drain over a period and monitor voltage. Again actual experience in use will test your battery. So all you need is a volt meter and the knowledge of what you are doing to "test" a battery. olewill[/QUOTE]
Thanks olewill, simple and practical
To test a domestic battery that way (in my case standard 100Ah wet lead acid), what numbers would you expect?
ie if you drain a current of say 4A for 6 hours, what voltage drop would be acceptable? Thanks

 

[macd]

...I use a Hydrovolt hydrometer to measure Specific Gravity...

Excellent bit of kit.
http://www.ebay.co.uk/itm/like/3220...=9046646&device=c&campaignid=738466455&crdt=0

No connection etc.

 

[Vegable]

But we still might want to know capacity ie ability to supply a low/medium current for a long time. The only way to test this is to discharge with a current drain over a period and monitor voltage. Again actual experience in use will test your battery. So all you need is a volt meter and the knowledge of what you are doing to "test" a battery. olewill

Thanks olewill, simple and practical
To test a domestic battery that way (in my case standard 100Ah wet lead acid), what numbers would you expect?
ie if you drain a current of say 4A for 6 hours, what voltage drop would be acceptable? Thanks[/QUOTE]

Ideally a battery should not be drained to below 50% of its capavity (to prolong its life). So your 100ah battery becomes a useable 50ah battery. So at 4 amps load it will take 12.5hrs to discharge to its 50% capacity - assuming a new battery and ignoring losses.
If you start with a fully charged battery at anything above 12.7 volts, and you've disconnected any input from battery chargers, wind generators, and solar panels, you should find that the battery voltage will drop under a steady load to about 12.4/12.5 volts and stay there for (say) 10 hours or so. (Depends on the age of your battery). If it starts falling below that and continues falling, then you've got a duff battery.
Last autumn on my boat, I've 5 x 135ah batteries I put on absolutely everything. The ammeter hovered around 22 - 23 amps, the battery voltage initially gave me a fright by dropping to 11.9 volts and then stayed there rock solid for over 2 hours whilst I kept checking the electrolyte levels with a hydrometer. After that it was tea time so I went home happy.
Mike