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#11848394 - 09/25/16 03:30 PM AA batteries for a bigger fish finder?
Tony from Oak Point Offline
Extreme Angler

Registered: 01/23/05
Posts: 2121
Loc: DFW, Texas
Curious if anyone has tried powering a big fish finder with just AA rechargeable batteries? The other day I tried out the "big" Hummingbird 798 SI finder with 16 AA batteries and it only lasted an hour or so. I'm going to go up to 20 AA batteries to bump up the voltage and then I hope to get 4 or 5 hours per charge.

My luck with cheap lead acid AGM "deer feeder" batteries is not too good as the last two that I've purchased have failed quickly with hardly any use. For the last year or so I've been using 16 NiMH AA batteries in two 8 battery holders wired in parallel with a Plano 3400 case. This has worked great giving me all day light weight power for a smaller Lowrance fish finder.

With my test the other day, the voltage started at 10+ volts. The power cut out soon after the 9 volt alarm was triggered so the batteries only used about 25% of their capacity before the voltage dropped too low. Since NiMH batteries operation at 1.2 volts instead of 1.5 volts compared to a regular AA battery this was part of the problem. To help bolster the power I'm now adding two, 2 battery holders so that each battery bank will have 10 batteries instead of 8. This will bump up the voltage from 10v to 12v per bank so I should be able to discharge the batteries much further before the fish finder cuts out. I will be interested to see if I can get the 4 or 5 hours per pack or if it will fall short? It will probably be a week or so before I can test out this setup. In the mean time I'm curious if anyone else has gone this route and if so how did it work? If it's not feasible I may go in another direction.




Edited by Tony from Oak Point (09/25/16 03:33 PM)

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#11848717 - 09/25/16 06:28 PM Re: AA batteries for a bigger fish finder? [Re: Tony from Oak Point]
ChuChu1 Offline
Extreme Angler

Registered: 03/08/10
Posts: 2767
Loc: Gonzales, Tx
How about a lawnmower battery?
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#11848772 - 09/25/16 06:58 PM Re: AA batteries for a bigger fish finder? [Re: Tony from Oak Point]
Tallgrass05 Offline
bill maher's protege

Registered: 03/02/05
Posts: 39972
Loc: Kansas
That looks like a lot of hassle. Which deer feeder batteries did you buy? Did they have enough amps to do the job?
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#11849255 - 09/25/16 09:53 PM Re: AA batteries for a bigger fish finder? [Re: ChuChu1]
Tony from Oak Point Offline
Extreme Angler

Registered: 01/23/05
Posts: 2121
Loc: DFW, Texas
Originally Posted By: ChuChu1
How about a lawnmower battery?


That's a good suggestion for a lot of folks. A friend of mine uses one when a "big" deep cycle isn't needed. However, when I've tried in on my little Heritage Featherlite it took up too much room and was too heavy. Being a bit lazy I like something light enough I can carry up and down from a launch point in one haul which is why I'm complicate things lol.

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#11849379 - 09/25/16 11:10 PM Re: AA batteries for a bigger fish finder? [Re: Tallgrass05]
Tony from Oak Point Offline
Extreme Angler

Registered: 01/23/05
Posts: 2121
Loc: DFW, Texas
That's a good point Tallgrass, it's extra trouble for sure.

Today as I have had a chance to read up on the subject, I see that Lithium Iron Phosphate batteries are being used now in place of AGM "dear feeder" batteries for those kayakers willing to spend 4 times extra for about 1/4 the weight depending how you calculate things. Looking at the true amp ratings for the Lithium Iron Phosphate batteries, I may get close to the same performance per weight with the NiMH batteries at less cost? The downside or upside depending how you at it is I'm dealing with a bunch of individual AA batteries. I imagine that the existence of LiFePO4 batteries has preventing anyone else trying to use AA batteries to accompish the same thing I'm trying and I may end up going that route too although it aint cheap.

Regarding the lead batteries, I had two wildgame 12vb/7ah AGM batteries fail on me in pretty short order. For this application I'd need a bigger AGM battery, probably something in the 12AH range or higher which would be 9lbs or higher.

For my Lowrance Mark 4 HDI, 8 2400MAH AA Amazon high capacity batteries last ~3+ hours. 16 AA batteries last ~6+ hours. The pack with 16 batteries in the pic weighs about 1.5 pounds with the case which is a lot lighter than the 5 pounds or so that the smallest 12v dear feeder AGM battery weighs.

For the new battery back I'm use all EBL brand 2800MAH AA NiMH batteries. I think 20 batteries will give me about 3 or 4 hours. Guess we'll see when I get a chance to test it out more.

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#11850214 - 09/26/16 01:40 PM Re: AA batteries for a bigger fish finder? [Re: Tony from Oak Point]
Searsay Offline
Outdoorsman

Registered: 07/26/12
Posts: 156
Loc: Lewisville TX
tony - i was going to respond to you yesterday as well on my thread but this is probably a more appropriate location.

You can buy all the parts for a LIPO battery including individual cells at a much cheaper rate - but you have to include a "control" circuit. I think the cost for building an equivalent of the 14AH battery i had in my thread worked out to ~$60 in parts instead of the $100 the built one did. That said i was looking for something that if my son got into it would be somewhat safe - hence the pre-built one.

LIPO batteries get very reactive if you overcharge them (see hover board fires and samsung phone issues) - and get ruined completely if you let them drain below 3% (most control circuits will cut them off at 5%) - a $5 control circuit will prevent that.

Biggest issue i can see with you rig will be the lifespan of the NiMH batteries - i've never had luck with them lasting to long life-cycle wise.

One item of note for your rig - most fish-finders will handle a voltage range that goes from 9-14V - so you could do 12 batteries in each bank which will take you to the top end of that and give you the maximum run time for each bank that is possible. It should also reduce the individual load per cell, which will reduce the individual heat load and extend the battery life more (since heat is what kills most batteries and electronics).

Regardless if you get that to work... it may be worthwhile seeing what it would take to charge the whole rig in place as well - that way you never have to unpack any of it (and save yourself a ton of time/effort).

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#11853170 - 09/28/16 01:05 AM Re: AA batteries for a bigger fish finder? [Re: Tony from Oak Point]
Tony from Oak Point Offline
Extreme Angler

Registered: 01/23/05
Posts: 2121
Loc: DFW, Texas
Thanks Searsay. Those are good suggestions. I didn't consider constructing a LIPO battery with individual cells and a controller but it would be a fun project should I get brave. Charging the batteries in the holders all at once has potential too. Thanks for the details regarding the Lithium batteries.

NiMH batteries have been hit or miss for me too. Fry's used to sell "Rayovac 4.0" batteries for not much more than a dollar a piece and I bought about 2 dozen of them back in 2008 /2009 and within the last year or I'm just now buying new NiMH batteries as they start to fail. With the Rayovac 4.0 I've been able to deep discharge 100s of times but I've had less luck with Energizers, non-hybrid Rayovacs, and Harbour Freight NiMH AAs. Now I'm trying Amazon high capacity NiHMs and EBL high capacity NiHMs. So far the Amazon batteries have had the most testing and they have done well along with the Rayovac 4.0 powering my Lowrance 4 with GPS. I think the Lowrance 4 fishfinder series is very tolerant of low voltage though. I'll post how 20 batteries work (would go up to 12 per bank as you suggest but no room in the little plano 3400 case lol).

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#11859690 - 10/02/16 02:01 AM Re: AA batteries for a bigger fish finder? [Re: Tony from Oak Point]
Tony from Oak Point Offline
Extreme Angler

Registered: 01/23/05
Posts: 2121
Loc: DFW, Texas
The verdict is in, AA NiMH batteries are good enough to power my Hummingbird 798ci HD SI finder. 20 2800mAH NiMH batteries split in two parallel banks crammed into one Plano 3400 case was enough to power the finder for 5 hours 45 minutes continuously with backlighting, gps, sidescan, di, (everything) running. I never had to use the spare battery pack.

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#11859788 - 10/02/16 08:06 AM Re: AA batteries for a bigger fish finder? [Re: Tony from Oak Point]
Cast Online   content
TFF Team Angler

Registered: 07/31/12
Posts: 4794
Loc: North Texas - God's Country
I don't get why the 6v batteries failed you. I'm waiting for a flexible solar panel equipped yak. Why doesn't a manufacturer offer a power pack option?

I think about my Monarch feeders. 9.6ah of 12v plus a small solar cell equals years and years of flying corn.
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#11859998 - 10/02/16 10:22 AM Re: AA batteries for a bigger fish finder? [Re: Tony from Oak Point]
Tallgrass05 Offline
bill maher's protege

Registered: 03/02/05
Posts: 39972
Loc: Kansas
I've had zero trouble with my $20 Cabela's 12V 8Ah battery. It weighs a bit under 6 lb and will run my Lowrance Elite 4-HDI all day, or until I'm tired of fishing and head in.
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#11864460 - 10/04/16 03:00 PM Re: AA batteries for a bigger fish finder? [Re: Tony from Oak Point]
Tony from Oak Point Offline
Extreme Angler

Registered: 01/23/05
Posts: 2121
Loc: DFW, Texas
I think some of those kayaks for ocean trips have solar cells. I guess it would need to be fuse protected pretty good to have a solar array out on the water in case it gets wet and shorts out. It seems like a bigger solar panel could power a small finder without issues though.

Tallgrass, you have a lot of good points. If I wasn't doing crazy launches down rip rap and such I'd just go with a cheaper lead acid gell cell. In the past I did use some meant for UPS power supplies that lasted an insanely long time like 7 years so I now it is not just the gell cell.

I did some reading and found this link.
http://www.cieux.com/bm/batteryWreck.html
In a nutshell it claims that you can only drain a gell cell at 1/20 it's overall rated capacity and only down 10 volts. So when I was using the 7AH gell cell to power my crappie light that drains 1.2 amps I was damaging the battery. I also at first used a car battery charger at 2amp which seemed to kill my first 7AH battery pretty quickly.

I tested my fish finder with an analogue amp meter and it seems to pull about .7 amps which is a bit more than what it is rated for. To follow the rules in the link above to avoid battery damage I'd need a 14ah gell cell which would too heavy for my little SINK kayak. My AA battery pack for the Lowrance 4DSI lasted all day and weight a bit over a pound. My current pack that runs the bigger finder over 5.5 hours is a pound 8 ounces.

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#11864636 - 10/04/16 04:38 PM Re: AA batteries for a bigger fish finder? [Re: Tallgrass05]
Capt Jerry Online   content
Outdoorsman

Registered: 12/22/13
Posts: 244
Loc: Cedar Creek Lake
Originally Posted By: Tallgrass05
I've had zero trouble with my $20 Cabela's 12V 8Ah battery. It weighs a bit under 6 lb and will run my Lowrance Elite 4-HDI all day, or until I'm tired of fishing and head in.



Same here. Just be sure to put the charger on when at the end of each day.

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#11865168 - 10/04/16 09:25 PM Re: AA batteries for a bigger fish finder? [Re: Tony from Oak Point]
pelican Offline
Extreme Angler

Registered: 08/27/11
Posts: 2399
Loc: Grapevine
I could never get a AGM / Lead acid deep cycle battery to last more than about a year and they are heavy.
I decided to buy a Lithium Ion and it's been great. It's very light weight, it recharges much faster than lead acid and it has a much longer life cycle. Even though it was more $$ up front when you consider it will last much longer and the weight factor makes it a great battery for kayak use.
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#11870760 - 10/08/16 12:02 PM Re: AA batteries for a bigger fish finder? [Re: Tony from Oak Point]
Tony from Oak Point Offline
Extreme Angler

Registered: 01/23/05
Posts: 2121
Loc: DFW, Texas
Pelican, good to know I'm not the only one that kills lead batteries in a year's time :-). I'm sure I made some mistake with discharging / charging but nothing too crazy. At any rate I'll probably go with the LiFePO4 (Lithium Iron Phosphate) battery on my next battery purchase (if I have a next purchase)? I've been using AAs to power my fish finders for the last 5 years or so and it's cheap and easy to replace an individual failing battery when needed.

In case it helps someone with their own battery setup I thought I would post some measurements with my cheapo amp meter. The Humminbird 798 ci hd si combo draws .70 Amps with the screen turned up to 10 brightness (where I get 5.7 or so hours of use from the 20 AA battery box). This is a bit more than the max draw in the paper work details but it matches my test using another meter. What was interesting is just by dropping down to 8 brightness the consumption drops to .58 Amps, at 5 brightness it drops to .48, and at 1 brightness down to .41 Amps. So the screen back lighting does sap a lot more power, more than I expected. That is where most of the extra juice is going I guess, not in the SI or the CPU. In comparison my older Mark-4-HDI with GPS black and white fish finder with the stock transducer (not DI) draws .35 at 10 brightness, .30 and 5 brightness, and .29 at 1 brightness. So the new finder uses about twice the juice as the old one, but turning down the brightness evens things out a lot.


Edited by Tony from Oak Point (10/08/16 12:05 PM)

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