7 amp battery question
 

I have a 12 volt 7 amp SLA battery and a Lowrance Elite HDI. The unit draws a fraction of an amp/hour, correct? last fall, same battery would last 4 hours on the bilge pump at 2.1 amps. it took a dump this winter! Maybe the cold room where I kept it??

so yesterday the battery only lasted 2 hours. I got home, charged it and the multimeter is reading 17 volts?? Busted multimeter??

More important than the model of FF is the screen size for judging how long it should last on a 7Ah battery. For a 4" it should be fine. For >5" you might be pushing it.

That reading on your multimeter could mean alot of things.

On the FF, also matters if you have the backlight on

maybe thats it! backlight seemed very very bright all morning

SLA Batteries are really prone to dying. If your Lowrance doesn't have GPS... it should last much longer than 7 hours. With GPS its might be pulling more than an amp/hr. Combine that with a dying SLA and there you go...

I replace SLA every year. I have heard of them even showing up bad out of the box.

Shortened duty cycle on an SLA is pretty typical of it going bad. I have a pretty good understanding of the physics of SLA technology but cannot for the life of me see how a 12 v battery can put out 17 volts. 13.5 to 13.8 right after taking it off the charger is possible but not 17. Break out the wallet. I think you have a failing battery and multimeter.

You mentioned the FF and the bilge pump(are you referring to your bait pump), are you running both off the same battery? If so, I would suggest you stop and get a separate battery for each unit.........don't keep all your eggs in one basket.

If you decide to go with another SLA go with a 12v 12a for your FF, that'll keep it going for several hours but whatever you do NEVER EVER let it go completed dead.

Assuming that your bilge pump is exactly that and you are not referring to your bait tank pump as your bilge pump and you do not have a leak in your kayak that would cause the pump to run more often than not I would suggest you get a 12v 7a. However, if the bilge pump that you're talking about is your bait tank pump get a 6v 12a battery, a 12v battery isn't necessarily overkill for a bait tank pump but its definitely not necessary. If you ask around you'll find that most kayakers use 6v batteries on their bait tank pumps.

LOL Great point. "My kayak sank because some a-hole on the internet told me how to save 3.5 amp hours on my bilge pump" :party:

7 amp ?
 

To run 7" ? Seriously? Try doubling it. 15 amp would be more appropriate . And you are tied into bait tank? SLA don't discharge well. Your battery is shot . Why it is reading 17 volts is not accurate . A 7" would probably consume .75 amp per hour . 15 amp would allow more than enough to run 10 hours with plenty reserve ? Even 12 hours. Also look for a marine battery capable of discharging and charging multiple times.

There are all kinds of issues with SLA batteries:

You can overcharge them by leaving them on a non trickle charger.

You can charge them too soon in their discharge (they can develop a memory).

They have a relatimely small number of recharges before they begin to lose capacity.

You can drain them too far, killing cells.

And they can easily discharge too fast with a short.

The good news is that they are cheap.

I have a garage full of them from before I switched to LifePo4 batteries. I have been using the same 2 6v batteries for at least 3 years and the same 2 12v batteries for at least 4 years. Averaging around 100 days otw per year. All of the batteries still last at least 2 7-8hr days per charge. The bad news is that they are expensive. But when you figure in the time and frustration of discovering and replacing bad batteries, it is not that bad.

That said, the backlight on most FFs will vary the power requirement quite a bit.

Plastic dip your battery terminals
 

Home depot $10 this stuff works good
I put electric tape first then covered put as many coats as you want.

I bought a box of 6 used battery at metalmart for $20
 

Every battery got a green light full charge

So do you carry a spare in case one doesn't last long enough? For that price it might be worth the extra weight to run a couple in parallel for better assurance the FF doesn't die in the middle of a fishing trip, which happened to me recently.

I only use one battery to run my hook 5
 

I haven't run out of power yet. I don't use a bait pump but if I did it would be another separate battery just for that.To much weight I prefer bait tubes I weigh 265
I paddle a cobra

Correct me if I'm wrong....
 

But I think they use the same batterys in alarm systems and it's is mandatory that they be replaced over a period of time, even tho they have never been discharged thats why you can pick them up second hand cheap.

AGM batteries are nice, and not that much more expensive. I use in motorcycle applications and experience good reliability. For you n00bs, a motorcycle is a lot like a bait tank ;)