5A 12V Load tester

[Carlos_tlewis]

Hello guys!

Just wondering if anyone can help me...

Part of my job asks me to test the batteries in alarm panels with a 5A load and record the voltage after about 15seconds, basically to if the batteries any good.

I'm either looking where I can buy one and what it's called as I can't find one? or I saw a guy with a home made one, I asked him about it and he said it's got a multi meter with a resistor (couldn't really tell as he had made a nice box for it.

Appreciate the help

 

[telectrix]

you need a headlight lamp from a car. 60 watts should do nicely.

 

[Carlos_tlewis]

Sweet, thanks!

I'll have ago at making one... see what happens. If anyone know the resistor way I would really appreciate hearing that as well.

Thanks again!

 

[telectrix]

it'd be a bloody big resistor to dissipate 60 watts of heat.

 

[Carlos_tlewis]

I know. I can't understand how the guy made one... maybe there is a car lamp inside! Might see if I can borrow it and take it apart and see what's inside.

 

[Tiny Spark]

You would need to make up 2.4 Ohm of resistance, You would probably need to put several good wattage resistors in paralel I would think.

 

[telectrix]

6 x 10watt resistors, each 15Ω , in parallel should do it.

 

[UNG]

There is always these people Battery Testing | ACT Meters

 

[amlu]

you need a battery tester, quite common in car workshops
https://www.machinemart.co.uk/shop/search/filter/battery-testers/type/any/module/shopcategory/page/1

 

[telectrix]

i wouldn't like to put one of those across an alarm battery unless i wanted to destroy it.

 

[tazz]

ACT meters are the only quick and easy way to test SLA batteries. Before they were introduced, we used car cigarette lighters as a load.

 

[Lucien Nunes]

+1 for those testers, they actually display the estimated capacity in Ah rather than just a voltage under load.

I lashed up a useful battery tester in a couple of hours using a 3-terminal regulator (e.g.LM317) as a current source (by putting a resistor between ref and output that drops a voltage equal to the reference at the desired load) with a couple of outboard pass transistors. These dissipate most of the power with only a small fraction of it heating the resistors.

The advantages of this unit were that the load current was accurate regardless of battery voltage and it could be used without adjustment on any battery from 3 to 24. I think the load settings were 0.5, 1, 2, & 5A. A panel voltmeter was connected permanently to the battery leads but the load was only applied while you held the button. The power transistors were screwed to the diecast box with a thermal fuse stuck to one of them, although if you held the button for too long at 5A / 24V you would drop the tester before it caused damage!

 

[The Finch]

From memory when I was a apprentice the guy I worked with had a big resistor with wires soldered on, put this across his meter probes and tested the battery under load, one of the companies I used to work for made me one up as one of the contracts specified testing batteries that way, it was 2 high wattage resistors in series mounted on a heat sink with two flying leads, nowadays I use the act tester, if you can get hold of one go for the small gold intelligent battery tester, the new big ones although can read 6v batteries I find to give odd readings

 

[Dcf]

try an mr16 12v 50w lamp holder and lamp on a couple of push on crimps
check voltage with meter.
i think a 50w lamp is about 4 amp rather than 5 though
soon tell you if the batteries buggered though