Backyard Aquaponics
A place to discuss aquaponics

Cool re: off the shelf controllers. I have one on my own electric bike.

Everyone run out and buy an electric bike or an electric bike conversion kit for your existing bike. They are awesome!

I'm not sure it would do everything I would want it to.

The boat has a total of 360 watts of solar panel, so I'm guessing cruising speed would be at the lower end so I could keep moving for 5 hours a day, but I also dont really need a lot of battery. Just a bit to act as a buffer.

I ran it without solar for years on a 100... maybe 120 AH battery. Most trolling speed is slow walking speed, and boats tend to have a maximum speed that the hull wants to run at, and no matter how much extra thrust you throw at it, it doesn't seem to gain a lot. Having said that, I think my boat goes a different way. Its a catamaran that's perhaps 8inches wide max each hull, so there is very little drag. I suspect the prop angle sets the maximum speed before the hull does, as the motor is designed for a displacement hull or a small tinny. I think my boat ...kind of...outruns the prop. Like if you were pushing a car and the car was doing 99.9% of your max running speed.

Either way, the battery didn't last as many km on fast as it did on slow, so we tended to use it at the lower end of the speeds.

It could travel around 6km at a fast walking pace from memory (which would have been setting 3 of 5) with a final voltage under load of around 11.5 volts, that then raised up to ... and this is getting very vague...maybe 12v after a little rest.

But that is of course using it like everyone tends to use their boats. Weekends at best, not flat out, and sometimes long rests between trips... like winter long. (always kept on the 7 stage smart charger)

It was still a usable battery up until the last time I checked it when I discovered the error msg on the charger. It was bought around 8 years ago.

No doubt using it every day would be another matter, although my plan was to never intentionally run the battery lower than 95% charged when I camped for the night because I would always want the ability to find a camp site in a storm, to be able to recharge a phone or a laptop and to give the battery a chance at a long life. If there was no sun, I simply wouldnt leave where I was camped until there was.

I can get AGM batteries for around $3/AH I think, and Lithium would set me back 12$/AH I think.

I've spent hours in chat trying to get battery sales people to tell me what I need to know, but it doesn't seem to be working.

I would have thought battery sales people that sold all three types of battery could tell me...

What is the cost per "usable" AH (and I understand that's vague, but wanted them to compare total recharge cycles, like for like) for Gel, AGM, and Lithium Ion?

I've decided instead to simply buy one of the stores in question, send my new sales team to where ever you learn this stuff... battery school? then ask them the same question again. I think it would be less frustrating, and cheaper in the long run:)

My electric bike has 15kg of old school lead acid batteries 36AH I think)(giving it around 25km at 20kph on flat ground with no wind and no peddling. The stats the seller offers claims the same kind of performance from their 10AH lithium packs, as they claim from the lead acid version I have.

Does that mean I can run a 10AH lithium battery to zero AH? If so does that mean it has three times the usable storage of a lead acid battery?

Who knows.

I run(ran) the battery as a constant backup for my aquaponics system, and the plan was always to connect the boat to the aquaponics battery and inverter when it was parked in the driveway. There's no point having solar panels just sitting there, and the battery always needs to be topped up no matter what. But the point is, whatever battery I bought would also be one that would enjoy being connected to my aquaponics system.

Then again, for 2000/4000km boat trip, I'm guessing I have to consider the battery(s) as a consumable

LiFePOP4 chemistry beats Lead-acid as fas as usable kWh/$ over the life of the battery. No battery should be run to flat, generally you want to keep Lead acid above 75% state of charge (SOC), and you can take Lithium down to about 20% SOC, for a similar overall life time.
Lithium battery charging is a lot more efficient than Pb-acid charging, so you'll have significantly more energy available from your solar panels to drive the boat. Lithium batteries weigh heaps less than Lead-acid, and operate much better at low ambient temperatures too. Lithium batteries have much lower self-discharge rates, so you only need to give them a slight charge every 3-6 months (and they are best stored only partially charged), but Lead-acid batteries need more frequent topping up- to fully charged. Lithium batteries can safely be left at a low SOC, but Lead-acid batteries will die much sooner if left partially discharged for lengthy periods.

Awesome thanks.

Does that 75% for lead acid apply to AGM? One of the sites I read said I can take them down to 20% and get the same life as taking a GEL battery to 50%.

I spent another hour or so last night in chat with battery sales people to try to get this information. There is so much contradictory info out there.

I don't think there is a huge difference between the various types of Lead-acid batteries, flooded, AGM or gel, as far as longevity goes. Supposedly some gel and AGM batteries can be taken to flat, but it does significantly reduce their lifetime, and in my experience the claims for life for all batteries are on the very optimistic side.

Lithium batteries don't suffer Peukert effect loss of capacity like Pb-acid batteries do, which is important when you want to run your motor fast. That 100AH battery when discharged at 5A suddenly runs out of puff after delivering only maybe 50AH when you try to discharge at 40 or 50A. A 100AH LiFePO4 battery has no problems, and no loss of capacity, when delivering 100A.

Disinformation on the internet. Who would have thought.

I only have a 30 amp MPPT charge controller so I doubt I'll ever draw more than 30 amps from the battery unless there's an emergency. Though I notice I need a 130 AH lead acid batter to handle that kind of charge. That's 45kg or so which is fine when it's being used on the aquaponics system, but isnt so good on my little boat.

If I were to buy a lithium one, it would have to be a lot smaller than that. 22 AH looks like it would cost around the same as a 130AH SLA, but to get one that would take the 30 amp charge, looks like I would need to go to way larger.

You would think these battery sellers would just show some charts indicating all this stuff. Some show part of the story, but I want a site that show everything so I can gauge the differences through their own level of lie. I figure if all the information is from the same place, the level of lie, is likely to be more consistent.

I suspect the level would vary relative to the profit margin for each particular model of battery

All the decent battery manufacturers publish data on their batteries, which will be more believable than some retailers' word of mouth claims, although you should take that as a best case scenario- lab conditions rather than in the real world.

We have a 20AH LiFePO4 battery for starting the old Hilux, putting out 100+A is no problem and nor is charging at up to 50A, although you don't need to do it for long.
For your boat, I'd think around the capacity of 50 or 60AH should do the job, and it will save you a lot of weight.

I'm still trying to get my head around 3 phase variable frequency drives.

Changing the AC Hertz changes the speed, I get that.

Changing the order of the phases changes the direction of motor rotation. Kind of sort of get that.

Changing the direction of motor rotation whilst attached to a centrifugal pump, and it still pumps, just a lot less water. That I don't really get...

I also don't quite understand how they change the frequency, is it turning 50Hz 415V 3ph into DC then an inverter is going back to AC?

Either way, nice motor speed controllers, certainly do their job well

The rotor spins around and throws the water outwards (hence 'centrifugal' pump), the outlet hole is approximately tangental and lined up with rotation direction, so the water flows out there and gets sucked in via the inlet which is centred over the rotor. Running the motor backwards still throws the water outwards, but now it has to reverse direction to escape, so it will be quite inefficient.



It's running from a battery or other DC source, which could be 240VAC converted to low voltage DC, and the controller is just a variable frequency 3 phase inverter. Most pumps for use in AP, pools etc are likely to be 3phase 20-50VAC, and the voltage may increase a bit as the frequency goes up, to maintain power. Sometimes, rather annoyingly, these 3 phase AC pumps are called brushless DC motors. Brushless DC motors are permanent magnet DC motors.

That's twice the $ of the lead acid alternative, and my blog has to pay for everything I do. And it doesn't help that I haven't written a whole lot in the last year or two

I'm starting to think I should tempt fate a little and run the charger only when I'm running the motor to eat some load, and when it's sitting in the driveway being used as the power supply for my aquaponics system, I should just unplug one panel.

That way I think I can buy a smaller battery and save a buck and some weight.

Every kg of battery I take has to come off my ethanol to body fat carbon sequestration program I've been running for many years, and I figure I still have around 16kg to go.

Or I could add a third hull from a length of 8inch PVC and put off global warming for a bit longer by keeping the carbon locked up.

I get some pretty good battery pricing through work if it's any help to you Bullwinkle.

Gordon may not like this Bullwinkell but you could make your own l-ion battery pack. There is a guy on the net who made an off grid battery bank out of (I think) used laptop battery packs (Obviously only kept the good ones).

Certainly doable to make a small battery, but looking after so many tiny cells for a large capacity one would be a nightmare, and I doubt it would last all that long. I'd need a truckload of laptop batteries to replace my house battery

BullwinkleII,

I'm surprised Edison NiFe batteries are not in your top 120! My next DIY battery project is building an Edison-style NiFe battery bank to last a life time... Well, at least some little ones for my kid's science fair project next year.

The Idiot/Edison Battery DIY
DIY solar system with NiFe (nickle Iron) batteries

I know one old guy in West Texas who built his 5000 Ah cells like this:

I haven't yet checked the price for buying NiFe batteries from those Chinese factories, but they may not be cost prohibitive.

--
Sam

If BW wants to make one as described above for his river trip, he'll have to upscale to a barge to take the weight!

I love a bargain... so yeah!

And I do need a new battery so I'll ask when it's time.

I've spent a few more days on the river at Morgan over the last few months, and feel I have to really get a handle on the timing of this trip.

The flow is currently enough that it might be a struggle to move upstream. I'm guessing from looking at driftwood floating by that it might be around 3 or 4 kph. That's enough to put quite a dent in my plans if I time it incorrectly for the upstream leg.