What battery should I get for Hummingbird 688ci di?

What battery should I get for Hummingbird 688ci di? I'm fairly confused on that one, and I know you guys have been there done that. The unit is very similar to a 597ci di.

Thanks guys

7ah-9ah sealed battery.  They are available at a number of places.  Bought mine thru Home Depot (garage door opener replacement battery) but only because I had a coupon for $5.00 off.  They also sell them in the lighting section for emergency exit battery backup (CHECK THE DATE CODE though; some of them at my H.D. store were already over 2 years old!).  Lot's of places sell similar batteries.  Depends on what dimensions you want & where you want to place it.

~Bill

i don't known what the power consumption on a 600 series is compared to the 500 series or how much DI adds to the power usage. Would be interested in finding out. On the humminbird 500 series I get at least two long days of fishing off a a 4Ah LA

As a general rule of thumb, assume about 75-80% "useable" battery before voltage starts to drop below "useable" voltage for most units.

As a general rule of thumb, assume about 75-80% "useable" battery before voltage starts to drop below "useable" voltage for most units.

I don't think batteries are rated that way.  I think you get 100% useable battery when it is brand new out of the factory and that's how they are rated.  Through general usage in our application (or even just sitting on the shelf), you quickly go to 80% capacity or less, and then it is a slow steady decline from there until the battery dies months/years later.

-Allen

So something like this?

http://www.homedepot.com/p/UPG-SLA-12-Volt-9-Ah-F1-Terminal-Battery-UB1290/203770508?MERCH=REC-_-nosearch2-1-_-NA-_-203770508-_-N#

Perfect.

As a general rule of thumb, assume about 75-80% "useable" battery before voltage starts to drop below "useable" voltage for most units.

I don't think batteries are rated that way.  I think you get 100% useable battery when it is brand new out of the factory and that's how they are rated.  Through general usage in our application (or even just sitting on the shelf), you quickly go to 80% capacity or less, and then it is a slow steady decline from there until the battery dies months/years later.

-Allen

It's not, persay, a "rating".  As you use a battery, even the first time, the voltage output will decline from "full charge" of ~13.2V to ~10.2'ish V as you use that battery.  Some brand units (ie. FF/GPS) will shutoff when the voltage drops below a threshold.  I've found that most batteries will drop below that "threshold" at around 80% of rated cpacity.  Some higher ~ 90/95% but others are much lower.

Bill

I think I got the 6 or 7ah version of this battery.  It was like $25? last year.

Bill

I use 7ah with all my units.

This is the one I bought I think.  7ah $20

http://www.homedepot.com/p/Mighty-Mule-12-Volt-Replacement-Battery-and-Fuse-Combo-Kit-for-Mighty-Mule-Gate-Openers-FM150-EFK/203642200

As a general rule of thumb, assume about 75-80% "useable" battery before voltage starts to drop below "useable" voltage for most units.

I don't think batteries are rated that way.  I think you get 100% useable battery when it is brand new out of the factory and that's how they are rated.  Through general usage in our application (or even just sitting on the shelf), you quickly go to 80% capacity or less, and then it is a slow steady decline from there until the battery dies months/years later.

-Allen

It's not, persay, a "rating".  As you use a battery, even the first time, the voltage output will decline from "full charge" of ~13.2V to ~10.2'ish V as you use that battery.  Some brand units (ie. FF/GPS) will shutoff when the voltage drops below a threshold.  I've found that most batteries will drop below that "threshold" at around 80% of rated cpacity.  Some higher ~ 90/95% but others are much lower.

Bill

We're sort of saying the same thing, but not entirely.  The problem is that we use these batteries more in a deep cycle fashion.  It only takes a few deep discharges to reduce their capacity to 80%.  it's less a function of the fishfinder, and more a function of how we use the batteries.

-Allen

What chargers are you guys using?

I have a 597 HD CI, which as you said, is similar to this unit.  Both are rated to draw 615 mA.  I use a 7 Ah battery with this and it will last a full fishing day.  It won't last another day without re-charge.  The 7Ah batteries are fairly common and not too heavy.  If there was a lighter 12 Ah at a decent price, I'd likely choose that, as it would keep my discharge above 50% when using for 1 day.  This will give better lifetime for the battery.  But it also has enough juice to go 2 days if I'm unable to charge for a second day.

-Allen

FWIW ... check out this article I wrote on SLA batteries.

http://www.kayakfishingmagazine.net/articles/139-kayak-fishing-how-to-articles/1538-sla-batteries-demystified.html

-Allen