Problems in connection 24VDC &19A battery to UMI-7774 (please reply quickly)

[mechanical Engineer]

I have a UMI-7774, first I connect it to transformer circuit and it works well, but when I connect the UMI-7774 to two batteries in series each with 12V and each can gives 19A, the umi doesn't work, all what happens that when I make a contact at first between the batteries and UMI the leds illuminate and then turn off, so i don't know wgere is the problem, and for your information, when this problem happened, I connect the batteries to a 24V motor with 0.33 hp and the motor worked well.

And thank u? 

[AnalogKid2DigitalMan]

Does the 7774 still work when connected to the transformer again? If so, I would try the batteries again, making sure your connections are tight. I see no reason why it would not work running off of batteries.

[mechanical Engineer]

I went to the office that i bought from it the umi-7774 and the engineer there bring a variable voltage power supply and he make a connection between them and the umi-7774 worked well, so what is the problem with the batteries.

Thank you,

[Brian_Beal]

What is the measured voltage of the batteries.  It will higher than 24V, but might it be too high?

[VINAY KUMAR D.I]

battery voltage might be higher than 24V, check the voltage acroos battery.

[jslouie]

Hi ni-motion,

Thank you for using National Instrument's forums.  At this point in time, I would suggest finding out how much voltage the batters are giving, as everyone else here would like to know.  Also when the batteries are connected to the UMI, is the voltage still 24V across the terminals?  Is it possible the batteries are older and actually don't give the 19A of current they suggest?  Or are they giving too much (i.e. voltage is too high)?  Please let us know of your findings.

Thanks!

Justin Louie

[VINAY KUMAR D.I]

but if battery is not giving 19A, not an issue.
i don't think UMI draws much currnet.

[jslouie]

Hi Vinay,

Yes, this would definitely be the case.  The UMI doesn't draw much current at all.  I probably should have been more clear, but I'm referring to when the battery is so old that it is not able to maintain its voltage because of lack of current ability.  Namely, it isn't able to output above 230 mA required to power the UMI.  As highly unlikely as that is, I still wonder about it.

Thanks!

Justin Louie

[mechanical Engineer]

I bought a dv-voltage supply with variable voltage and ampere, and I connect it to the UMI-7774 and then I adjust the o/p voltage of the supply on about 19V, and the current on 0.05 volts approximately, and then the UMI works well, so my conclusion as I think that the 24V battery which gives a 24 V when I connect it to the UMI, can't handle this very low ampere, which is out of its range, like if i operate 100W pump on a system needs 0.2 W ( for example).

Tank you all for co-operation

[Buechsenschuetz]

I don't think the problem is related to the missing low-current handling ability of the batteries.

It is rather related to the difference between nominal (rated) voltage and actual voltage of a battery. In case you use a lead-acid battery it will consist of 12 cells. The nominal voltage of each cell is 2V - BUT! the actual voltage may be up to 2.3V after recharging. In this case, the voltage across the battery terminals will be almost 28V, and maybe the UMI shuts down when connected to overvoltage.