NiMH Custom Pack Issues, HELP!

**Shadar Al'Niende** · 09-05-2010, 08:28 AM

Ok folks,

So I wired up 4x NiMH in series to make a custom pack. When metering voltage it looks fine ~5v.

When i metered for current, I disconnected my pos probe from the 400 mAh max and connected it to the 10A max side (without the fuse) to measure my ~1A that should be coming from the pack.

When i did this, i got an orange spark from the battery surface and my meter reads an error "OF"

The batteries got hot as well, which had me concerned. Not too hot to touch, but definitely warm.

I am using the rechargeable AAA sold in the store here. And this is the meter I am using. (And yes, i know that's my problem right there.. buying a multimeter from RS

so no need to mention it

)

**FenderBender** · 09-05-2010, 08:33 AM

Thats because you can't test for current on a pack with your multimeter the way you are trying to do it. You're basically creating a short with the meter. You don't need an expensive meter, and some of the RS meters are made by Fluke anyway. When not under load, the meter will actually short the pack. You may have actually blown the meter fuse and I would check the pack. The way to meter a pack/driver is to hook it up to an LED (any LED with proper resistor will work) and use the probes in series: batt+>probe->probe+>LED/resis.+>LED->batt-

**Shadar Al'Niende** · 09-05-2010, 08:34 AM

Oh, well that shows my lack of experience with a multimeter... How do I measure current on it then?

**FenderBender** · 09-05-2010, 08:41 AM

You have to meter it under load, with the probes in series (in line with + or - lead) not in parallel (pos to pos etc)

You're going to have to open it up now and check the internal fuse. Also, before you check for voltage again, don't forget to move those probes back.

**Shadar Al'Niende** · 09-05-2010, 09:59 AM

So by "under load" you mean when power is going to the components and not just off the pack?

Also, i'm going to be hooking my pos probe to the neg end of the pack and neg to the pos ends?