In another post someone asked about fish finder batteries. I advised that I had a Lowrance HDS 8 Gen 2 and I estimated I was pulling like 3 amps. Some advised that was to much and I don't know anything about electrical stuff. I got on YouTube and did so e research on how to determine amp draw using a volt meter. My next question is am I doing this right?

This is what it reads when it is set to full brightness with side scan.

This is when I dim the screen some.
Are my settings on the meter right? I unplugged the positive side of battery and used the meter to complete the circuit. So my guess is the meter would read how many amps is being pulled by the finder?? Is that right? Or am I still an idiot who needs to quit messing with electrical objects.. Any help would be appreciated.

So either you went and bought an amp meter to prove you were right in an internet post.....

Or you already had one and are being very sarcastic here when you say you 1) don't know anything about electrical stuff and 2) didn't know how to use an amp meter you already had.....

So which is it?

I think you have it right. Not sure why your load is higher than the specs would indicate. I have the same graph and will check mine as well.


Mine measured 1.45 amps. Maybe you have a bad splice on a connector or something?

I agree - looks like you have everything set up right.....but I would expect something in the <2a range.

The screen brightness is a big consumer of the battery - Henry, was yours set at brightest setting when you measured 1.45?

That's how you measure dc amperage

Yes, max brightness. It was about 1.0 at half brightness, which is my normal night time level.

I bought an amp meter to try and get a good accurate reading. I watched several Youtube videos to try and learn how to do what I was wanting to do with the meter. The reason I did this was not to prove I was right or wrong but to see if I might have something hooked up wrong and I am drawing to much power from my battery. Others mentioned they had a similiar or bigger unit pulling .4 to .7 amps or something like that which is really good. Currently I have to carry two 12v batteries with me to get a a full day of use on my fishfinder. Electrical knowledge still don't know and if you seen my rat nest of wires in my kayak you would understand what I mean. I just want to make sure there is not something I can do to help my battery life before I go out and buy a bigger heavier battery.

Lowrance Spec Sheet

The spec sheet says 0.7Amps with the backlight on and 0.4 with it off.

That's hardly within normal variations so something else is wrong.

If the finder was the only thing wired when you made the measurement, that unit is way out of specs or you have a short somewhere between the battery and the unit.

Disconnect the back of the unit and measure again. Shouldn't see any current at that point.

I would also stick the transducer in a bucket of water. The unit might be screaming trying to get an echo signal back.

Albert, let me know if you want some help chasing it down. There's a reason for it being higher than it should be and you're exactly right to try to determine what it is before it degrades further. I'm betting on a bad crimp or something simple like that...

Mine was dry when I neasured. Good idea on a current leak though..

Unless the crimps are touching between the two conductors, a bad crimp will only result in a lower current. Thinner wires will also result in lower current.


The rated current is measured at 13 Volts. The unit runs down to 10V and at 10Volts the range is 0.5-0.9Amps.

Hank & Ricardo thanks for the info. I am going to chase it down and check and recheck everything to see if I can figure it out. I can't find it I will take you up on that offer Hank. Thanks.

As said, unnecessarily long or too small gauge could effect it as well as would bad connections