what size battery for FF?

[Southerly]

i just found this link :

http://www.cieux.com/bm/batteryWreck.html

if i understand, and i applied the 1/20 draw * Capacity rule to .700A FF indicates 14 Ah batt. similarly, a .200 A FF would only call for a 4Ah batt.

however, applying the other rule not to exceed 20% discharge for expected avg 6 hr trips implies that the calculated 100% capacity would have to be 5 * 6hr = 30 hours. with .700 A draw, that would require a 21 Ah battery !!!

a couple other things are important- weight and cost. replacing a $20 battery once a year is not a problem, but having it fail mid-trip stinks. i like when calculations and practical experience gets the same answers.

[moc]

Moc,

I hear you but I was way surprised when I checked the specs. Lowrance B&W X4 Pro and older Lowrance M68C GPS/Fish Finder that is color - same draw. As I said, I was really surprised. Now I agree, go to a big screen, high power processor, and add backlight I bet it gets up towards 500 mA to possibly and amp. At an amp you are down to 7 hours with a 7 Amp Hour battery.

Later,
TTYaker

My BW FFinders on my canoe last a long time on my 7ah battery, but once I got the Color FF from Hummingbird with GPS, 5 inch color HD screen I on got 3 hours out of the same battery real world. I bought a 12amph battery and now the battery can last 5 to 6 hours before getting to the 9v level from 12 v and then shutting off the FF. I looked at higher capacity batteries but they also get big in size. I may rig up my kayak to have two batteries with a toggle sw between them, so when one battery gets to 9v, then I can sw over to the other battery while out fishing.

[Southerly]

my new FF is a humminbird 798ci si. i hooked it up to a fully charged 7ah in my living room, and was going thru the manual, using the simulator to set defaults etc.

at 45 mins - BLAM screen flashed white and shut down!!!! my 1st impression was that the FF would be going back for warranty. but i tested battery instead = 10V. i recharged and repeated the whole scenario.

that battery had left me flat after 3 hr, on a previous trip w/my old FF. that trip had started pre-sunrise and i had forgotten to turn off the light and blamed myself. but for whatever reasons, i accept that battery is not performing to spec after just 1 year and a couple dozen cycles.

thanks for all comments - all things considered, i think 12ah or more is what i need for the new FF. i'm leaning towards bigger is better with my own limitation that i can secure it below deck. hopefully, it will add to my stability like a sailboat's ballast

[ComeOnFish]

I recently returned two new Hummingbird 170 in a row to Dicks before the 90 day store warrenty expired. It wasn't battery. It was FF. Can you check if the FF is OK? Can you connect the FF to a car battery to see if the same thing happens?

Joe

[Southerly]

thank you ComeOnFish,

i wanted to test actual current draw with my multi-tester but couldn't figure out how exactly. i'm probably wrong, but it didn't seem like it could accomplish the range needed for DC .700A. i looked at a couple utube how-to videos and tried to monkey them but i couldn't get meaningful measurement.

i also asked the guy at battery warehouse if he could measure it, but he said no. he's very knowedgeable in his business and i think he understood what i meant so i left it at that.

i saw a tester at west marine that clearly indicated its range would cover me, but that unit was $40.

but Yes, i do have more than passing interest in its draw. but my actual concern is more with ability of a battery to run it and i think my old batt is in failure mode despite the fact that it can be charged to 13+V.

so i plan to run the unit on the new battery for say 8 hours, or it cuts out. whatever comes first. i'd kind of like to run til failure just to know but don't want to put unessary wear on the FF.