Q about power supplies/ Ah testing

[BAD ORCA]

I'd like to be able to do my own 20hr Amp hour capacity testing using a power supply. I would most likely be testing only single batteries at one time so i cant imagine i would ever have to test a battery that was over 250 Ah capacity. Voltage would be 6 or 12v.

Based on these specs I would only need a power supply that could output 15 amps max if i was testing a battery on the high end of this range. A 250 Ah battery would only require 12.5 amp load if my math is correct.

I played with a power supply several years ago at my old job but i cant remember exactly how it worked. To do a 20Ah test do i only need to adjust the power supply amps to the desired load and voltage sets itself or do i need to program in voltage and the amp load specifically and independently?

Im trying to get a decent power supply thats hopefully under $300. The fully programable ones start to get very expensive. More than i want to spend just to be able to test Amp hour capacity. Do i need a fully programmable power supply or can i use one of the cheaper ones like this one?

https://www.circuitspecialists.com/csi3010sw.html

[Lake-Effect]

Check out this thread. In it, one post mentions an active load, which is what you want for Ah testing, not simply a power supply.

[BAD ORCA]

Originally Posted by Lake-Effect

Check out this thread. In it, one post mentions an active load, which is what you want for Ah testing, not simply a power supply.

Ok great thank you. If im not mistaken the power supply sets an active load in amps. I will take a look though... That may have actually answered my question about voltage. If i used a power supply and set the amp draw, the voltage probably sets itself to whatever the current voltage of the battery is and drops as the useable capacity in Ah'rs diminishes. I need to read up again on how to do the testing but I think thats basically it.

[Stu Jackson]

20 Hour Capacity Test by Maine Sail

http://forums.sailboatowners.com/ind.../#post-1295253

[BAD ORCA]

Originally Posted by Stu Jackson

20 Hour Capacity Test by Maine Sail

http://forums.sailboatowners.com/ind.../#post-1295253

Thanks Stu...that was easy. Im guessing the advantage of using a power supply is that it maintains the exact amp draw throughout the duration of the test and does not require any adjustment?

[Lake-Effect]

A power supply ... supplies power. Usually plugged into AC, and producing one or more DC voltages, at up to a rated maximum current. An active load (or active sink) consumes power, at a steady current rate (yes, without requiring adjustment). I don't know why you keep saying "power supply", when what you're describing is an active load, to draw a steady current from a battery, as part of a capacity test.

[BAD ORCA]

Originally Posted by Lake-Effect

A power supply ... supplies power. Usually plugged into AC, and producing one or more DC voltages, at up to a rated maximum current. An active load (or active sink) consumes power, at a steady current rate (yes, without requiring adjustment). I don't know why you keep saying "power supply", when what you're describing is an active load, to draw a steady current from a battery, as part of a capacity test.

Sorry my bad. I meant DC load tester. We had both and was confusing them.

[stormalong]

Use several automotive headlights in parallel. With an ammeter in series and a volt meter across the battery you can adjust the load by adding headlights until you reach your load goal and also monitor battery voltage to determine when the test is complete.

Be sure to immediately recharge the battery after the test. Leaving it discharged will significantly shorten it's life.

[oleman]

Electronic load testers are normally used for testing high current power supplies. They are great for testing alternators for voltage regulation under loads. Also could be used for battery testing for capacity. At the lab I would screen gelcell batts in the old days with one. I have had a surplus one since the 70's all analog meters and it is one of my favorite test meters. Believe it will support 100V and 100 amps. Most non test equipment people think is is a power supply because it is rated in voltage and current on the panel meters.

Down side is it cost far more than the battery or alternator being tested.
Like most electronics it could be much cheaper now than when mine was new.

[BAD ORCA]

Originally Posted by oleman

Electronic load testers are normally used for testing high current power supplies. They are great for testing alternators for voltage regulation under loads. Also could be used for battery testing for capacity. At the lab I would screen gelcell batts in the old days with one. I have had a surplus one since the 70's all analog meters and it is one of my favorite test meters. Believe it will support 100V and 100 amps. Most non test equipment people think is is a power supply because it is rated in voltage and current on the panel meters.

Down side is it cost far more than the battery or alternator being tested.
Like most electronics it could be much cheaper now than when mine was new.

Thanks Oleman. Iv'e given up on the idea for now. The more research i do the more its becoming clear that a decent entry level load tester is going to set me back $500 minimum. It seems the cheap Chinesium testers are not worth the cardboard box they ship in, at least thats the feeling im getting.

If i was doing this for a living i would splurge but just for personal curiosity it seems too expensive. Hell i could get another Firefly battery for $500.

I think ill just do it the old fashion way as some of the other replies have mentioned.

[smac999]

If you have a battery monitor and a decent inverter it’s fairly easy to do. As you can set the shut off voltage on the inverter to 10.5V. Or less to deal with the voltage drop. Abd it will shut itself off. Then You can read ah drained on the battery monitor.

Otherwise it’s a $1000 for an automatic load tester.

[BAD ORCA]

Originally Posted by smac999

If you have a battery monitor and a decent inverter it’s fairly easy to do. As you can set the shut off voltage on the inverter to 10.5V. Or less to deal with the voltage drop. Abd it will shut itself off. Then You can read ah drained on the battery monitor.

Otherwise it’s a $1000 for an automatic load tester.

Thank you! thats good to know. I dont at the moment but that could be useful when i finally get around to installing one.