What battery should I get for Hummingbird 688ci di?

So what about Li-Po batteries. I just picked a Elite 5 HDI and also need battery advice. The Li-Po option seems awesome because of the weight and quick charge capability.

Anybody have actual experience with these?

A freshly charged 7ah ran my 688 for 7 hours yesterday. This was a newer battery than last week. I bought this one over the weekend. It's a gd beast but plenty of power I think.

A freshly charged 7ah ran my 688 for 7 hours yesterday. This was a newer battery than last week. I bought this one over the weekend. It's a gd beast but plenty of power I think.

You mean 12 Ah, right?  That's what I see in your pics!

-Allen

BTW, it's also interested to note that Craig's new batter is specified as 12AH/20 hours.  Remember what I said in my article about 20 hours?   

-Allen

Do you happen to know your new batteries voltage after the 7hrs?

Do you happen to know your new batteries voltage after the 7hrs?

It's likely still above 12V.  Battery discharge curves are very non-linear.  They stay in the "range" for the majority of the time then fall off dramatically when they hit the discharged point.

-Allen

BTW, it's also interested to note that Craig's new batter is specified as 12AH/20 hours.  Remember what I said in my article about 20 hours?   

-Allen

Yep...when I was checking around that 20hr rating seems to be universal, at least for these type/size batteries it is.

Do you happen to know your new batteries voltage after the 7hrs?

It's likely still above 12V.  Battery discharge curves are very non-linear.  They stay in the "range" for the majority of the time then fall off dramatically when they hit the discharged point.

-Allen

My intentions are to try and "be nice" to my battery and discharge to no less than than magic 50% number that's supposedly at around 12.2v. Are my efforts in vain? Can the voltage potentially drop like a rock while I'm not looking?

No Allen. I used a newer 7ah fully charged. I just got this battery delivered this morning.

See ... http://www.steveduncan.net/html/discharge_testing_slas.html

Which is an article about a 12AH battery.  Here is the curve contained in that article.



I believe that the 688 that Craig uses has a spec of 615 mA draw.  So look at the farthest right curve, which is .6A (600 mA).   It's hard to get a precise number from the logarithmic scale used, but it appears to stay above 12V until about 14 hours.  And at 10 hours, the 50% point of the 20 hour target, it appears slighly above 12.2V.

-Allen

Just as a reference, the Lowrance Elite can run down to ~ 10/10.1 V for operation.

Just as a reference, the Lowrance Elite can run down to ~ 10/10.1 V for operation.

Humminbird too, but then again, most electronics will.  It's an artifact of the voltage converters used in electronics and the fact that most of the components internally run a voltages much lower than 12V.  But as you can see in the 0.6A curve, by the time you get to that point, voltage is dropping extremely fast.  You really shouldn't count on getting much extra run time in that range, and your battery really isn't going to like being discharged that far either.

-Allen

Thanks for that Allen. I'm gonna see if I can get that graph for my 14Ah battery. My 5xHDI so far appears to draw less than a half amp so depending on how long a day I use the finder I've likely got at least 2 if not 3 days before getting near the voltage cliff.

Sorry to say but I thought that the question was in reference to the 688. Not Lowrance models.

No Allen. I used a newer 7ah fully charged. I just got this battery delivered this morning.

Hah!  Perhaps I should actually read what you wrote instead of just staring at the pretty pictures.   

-Allen