Solar for kayak

[alanw]

Originally Posted by beef78

If you use math and stuff you should figure out that when you use a pump rated for 12 volt on a 6 volt system, it will draw twice the current. Which means a 6 volt 10 amp battery would last half as long as a 12 volt 10 amp battery.

That just doesn't sound right according to Ohm's Law.

V = I * R

Voltage = Current * Resistance


The resistance of the motor is a constant, so the only things that can change is volts and current which means that as voltage goes down so does current.

That means that a 6 volt 10 amp battery should last longer than a 12 volt 10 amp battery.

[FishNinjaY]

Originally Posted by alanw

That just doesn't sound right according to Ohm's Law.

V = I * R

Voltage = Current * Resistance


The resistance of the motor is a constant, so the only things that can change is volts and current which means that as voltage goes down so does current.

That means that a 6 volt 10 amp battery should last longer than a 12 volt 10 amp battery.

This was my understanding as well.. Most of the pumps out there are "rated" for 12V, and around 2.5Amp draw, right? So, people have been advising using 6V battery to modestly decrease the water flow, and to prolong run time on the battery.

From your description, you are running BOTH your livewell and fishfinder off a single 12V10A battery? For way less than the cost of a complex solar set-up, you could get TWO 12V12A LiFePO4 batteries, that would weigh less also. I don't have this battery yet, but am considering buying it tomorrow.

http://www.amazon.com/Bioenno-Power-.../dp/B0083BMHPY

BWE member, GregAndrews (& others), here know a lot more about this. I'd look into this route, instead of solar. Good luck.

[jorluivil]

Greg turned me on to the LifePO4 batteries a few months ago, I was a little skeptical at first but I decided to take a chance. I've only had the battery for about two months and so far its but running flawless. I was on the last Islander trip and was able to run my HDS5 from about 6am to almost 8pm, it never skipped a beat. The PO4's aren't cheap but they are super light; the 12v 12ah weighs less than a 6v 12ah. I can't remember the exact cost of my battery but it was right around $170(includes tax/shipping/3year squaretrade warranty). Another thing to keep in mind abou these batteries is that you can charge them something like 1000 times before they start loosing their juice.

[Baja_Traveler]

My kayak is set up to use a 32 Watt flexible solar panel for system charging.
THIS one in fact. Got it some 10 years ago locally at a solar place that no longer exists, and it has been on every fishing kayak I've ever owned.

The main reason I'm set up for it is Baja trips. Everybody here has been saying to "just Charge every night at home" or "carry a spare" which is all fine and good for 99% of your needs. But in my past I was into expedition style trips, where I'd paddle out and not return to the truck for as long as a week (but the norm was 2-3 days). Space and weight is at a premium on these style trips, so carrying a spare meant leaving something else behind.

Haven't done one of those trips in a long while, one of my favorites was to paddle out of the Old Mill and camp way out on a little sand spit at the mouth of the bay on the point, where halibut WSB and yellowtail were within reach for sunrise hookups...

I still use it from time to time though. When my battery starts getting old it will not keep the finder running a whole day, so to stretch its full potential I plug the panel in and I'm good. Then I can spend the 30 or so bucks to replace it at my leisure.

Maybe I'll do one or two more expeditions before I get too old here, we'll see...

[danjor]

The best place I have found for LiFePo4 batteries is batteryspace, there prices are good and theres a 5% off coupon you can use. They have all the LiFePo4 SLA replacement batteries, all the stuff to build you own pack and anything else you want. I am no way affiliated with this company they are just who I have found to be one of the best priced quality battery suppliers after countless days of research on these batteries.

[Yakly]

Thanks guys for the info.... I think I'll take the advise from you guys and purchase LiFePO's. You guys have been doing this for some time so ill follow your leads.... It was just a thought as I'm into gadgets but understand the limited space.

I'm also one of those crazies (in the eyes of some) that want to do an extended trip up the coast and camp. So if there's anyone interested or if they're trips already planned, I'm in.

[FishNinjaY]

Originally Posted by Yakly

It was just a thought as I'm into gadgets but understand the limited space.

I'm also one of those crazies (in the eyes of some) that want to do an extended trip up the coast and camp. So if there's anyone interested or if they're trips already planned, I'm in.

I hear that.. we're all gadget heads.

If you want to think outside the box... why don't you get rid of the battery altogether? at least for the livewell.

I know there is a small-ish solar panel that can run an actual small pump that will take water from your swimming pool and pump in UP to to a gravity solar array on your roof for pool heating. The nice thing about that, is it is ALWAYS ON, and only runs when the sun is out. Perfect for people that like to run their pool filters during the night to save on electricity costs. Anyways, I bet that solar panel and pump have to be sufficient to run any kind of livewell bait tank, right? If it puts out enough juice, maybe you can even run your fishfinder also? or at least keep a FF battery topped off.

[Yakly]

I'm still looking at all kinds of options and trying to wait till the new boats come out to see what new goodies will be available. Sometimes it sucks wanting all of the new shiny stuff..... My girlfriend says I have ADD but whatever, it keeps me busy and out of trouble...... So far!!!!

[jorluivil]

"The best solution to our problems may actually be the nearest or the easiest. Sometimes it seems so easy that we doubt its effectiveness"

[Fiskadoro]

The traditional problem with solar for a Kayak is the size of the panel you need to put out the power required.

For instance I have a mono-crystalline solar panel for my truck to keep the battery up when I'm not using it. It's about the size of a piece of paper and only weighs a few pounds but it also only puts out 5w or .28amps.

It would charge a battery that's sitting but won't keep up with a fishfinder and bait tank.

A 50w mono-crystalline panel would put out 2.8 amps. That would be enough power to run a Hummingbird combo and a Hobie baittank but it would be roughly 2 ft square and weigh over 20 pounds.

More realistic would be a poly-crystalline 50w panel. Once again that's only 2.8 amps but I've seen some of those that were only like 12 pounds but they were still big something like 20x30 inches.

Pete you got me rethinking this though. I think most of the newer Hummingbird finders only pull half an amp. Having a variable voltage setup where you can step down to a 6v for the bait tank and that would pull less amperage about the same half an amp. 1.5 amps would probably do it.

I have several friends who are into bike touring and they are using combinations of 5w panels to make 20w and 25w systems for charging phones lights GPS etc...

I'll look around and see what I can find.

Jim

[PescadorPete]

Jim, it will be interesting to see what you come up with. Maybe a 12V panel to feed the ff directly and also feed the 12V to a PWM to power the pump. I built a PWM for my 1st bait tank setup and the 12V battery lasts almost as long as running the pump on a 6V battery. I didn't measure how low the 12V battery can go before the PWM quits. pete

[taggermike]

I'm with the get a bigger battery side and make sure you put it on the charger the night before you fish. I have thought of a solar charge set for Baja trips where you don't have access to power but plenty of sun. Bring 2 batteries and alternate them. Mike

[PescadorPete]

Here battery voltage versus current with a Hobie 12v bait tank pump, tank full of water:

12V --> 1.37A
11V --> 1.20A
10V --> 1.06A
9V --> 0.91A
8V --> 0.77A
7V --> 0.64A
6V --> 0.52A
5V --> 0.39A

On six volts, the pumps draws less current (so it uses less power) than at twelve volts. My experience has been a 6 volt battery last much longer that a 12 volt battery powering the pump.

[old_rookie]

Originally Posted by PescadorPete

Here battery voltage versus current with a Hobie 12v bait tank pump, tank full of water:

12V --> 1.37A
11V --> 1.20A
10V --> 1.06A
9V --> 0.91A
8V --> 0.77A
7V --> 0.64A
6V --> 0.52A
5V --> 0.39A

On six volts, the pumps draws less current (so it uses less power) than at twelve volts. My experience has been a 6 volt battery last much longer that a 12 volt battery powering the pump.

I bet the motor/pump moves less water too. If the amount of water circulated is adequate, then it sounds like a good solution. But this idea doesn't work for other electronics such as FF or whatever that needs to run on 12V. Usually they have internal voltage converters to bring it down to 5VDC for the internal electronics run - but there could be other devices that still need 12VDC - like the display or sonar. So it is best to run those at the rated voltage.

[steveooo]

Solar on the kayak definitely wouldn't be my cup of tea, but the technology is available...

Hobie has a foldable 23W Solar panel for the eVolve that kicks out enough juice to run the motor and push the kayak at about 2 knots indefinitely in sunny conditions. It weighs only 1.4 lbs and is designed to withstand getting wet with saltwater. With a few mods, I bet that could run a fishfinder or 2.

On our Santa Cruz camping trip, I was able to run my Garmin for 3 days off the same 12V 12aH LiFePO3 battery the entire trip without needing a charge. For an extended trip I think my preference would be to just bring a 2nd battery and KISS.

[jruiz]

Originally Posted by alanw

That just doesn't sound right according to Ohm's Law.

V = I * R

Voltage = Current * Resistance


The resistance of the motor is a constant, so the only things that can change is volts and current which means that as voltage goes down so does current.

That means that a 6 volt 10 amp battery should last longer than a 12 volt 10 amp battery.

Motors aren't resistors.

[Old Man in the Sea]

This is the charging system I would recommend to meet all of your charging needs

http://www.globalindustrial.com/p/ou...FSFyQgodZgIABA


only downside is that it requires an additional kayak to be towed behind you...

[alanw]

Originally Posted by jruiz

Motors aren't resistors.

Right, motors are inductive, but the load can be considered resistive