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**Dockhead** · 13-09-2018, 11:47

Quote:

Originally Posted by mbartosch

If anyone needs an idea how that could be done - this is the LiFePO4 battery pack we use for our electric dinghy motor:

https://www.entropypool.de/2015/06/0...-battery-pack/

Over the time I have built two of these packs and upgraded the wiring so they can each sustain 50 A of charge/discharge (70 A burst).

These packs are an extremely convenient way to carry around a powerful energy source, and they can even be used to extend our house bank during longer sailing passages.

They can even run the entire boat electrics in case of a failure; the following article describes this use case when the old Lead Acid bank on our boat failed during our first shakedown cruise: https://www.entropypool.de/2015/06/2...-bank-failure/

The only downside of the distinct DIY look: you better don't carry them around in public in these times...

I admired that project of yours the first time you posted about, and now I officially admire it again!

Das ist wirklich etwas Besonderes!

What kind of motor are you using it with?

I had outboard trouble this summer and think about electric dinghy power.

**Jammer** · 13-09-2018, 11:55

Dockhead,

The main difference is capacity density per unit volume. L16s are big batteries, and are available in several configurations. The ones that have lower capacity (in kwh, Ah) last longer, and usually cost less and weigh less.

The lower capacity generally means that there is more space for electrolyte between and below the plates, which reduces the impact of variations in surface shape on the plates as they cycle.

T-105s have higher capacity per unit volume than any of the L16s, which is why they don't last as long.

FLAs work ok down to around -30 degrees C -- we run them that way on cars etc every winter in Minnesota. They don't perform quite as well, especially in cranking applications, and you have to charge them at a higher voltage. Below -30 C people use battery heaters.

**Dockhead** · 13-09-2018, 12:00

Quote:

Originally Posted by Jammer

Dockhead,

The main difference is capacity density per unit volume. L16s are big batteries, and are available in several configurations. The ones that have lower capacity (in kwh, Ah) last longer, and usually cost less and weigh less.

The lower capacity generally means that there is more space for electrolyte between and below the plates, which reduces the impact of variations in surface shape on the plates as they cycle.

T-105s have higher capacity per unit volume than any of the L16s, which is why they don't last as long.

FLAs work ok down to around -30 degrees C -- we run them that way on cars etc every winter in Minnesota. They don't perform quite as well, especially in cranking applications, and you have to charge them at a higher voltage. Below -30 C people use battery heaters.

Thanks!

hellosailor · 13-09-2018, 12:05

Fuel cells are no panacea, there's no magic there. IF you are shorebound with a good natural gas pipeline connection, fuel cells make a great backup because there's always (ahem) going to be fuel so you can always get power. But once you need to get portable, fuel cells usually mean large gas (not petrol) tanks, or highly purified methanol. Which is stable, but neither cheap nor compact. So the only advantage to the fuel cell is that you can box one up, along with a drum of methanol, and ten years later it will still be ready to go with full capacity.

I don't understand the complaints that you can't properly (fully) recharge batteries from solar. IF the system is properly designed, which means the solar panels will be using an MPPT charge controller so they can always exceed the battery's voltage, then the solar system will always be able to bring the batteries to 100%, rashly assuming that you've got enough capacity for that to happen. If it can't happen simply because you're not getting enough watts per day from the panels...Well sure, that's the same thing as saying "I installed a ten amp shore charger, for my 500A battery bank. I don't know why it never charges fully!"

Watts is watts, the battery doesn't care what made them.

**Dockhead** · 13-09-2018, 12:09

Quote:

Originally Posted by hellosailor

. . . I don't understand the complaints that you can't properly (fully) recharge batteries from solar. IF the system is properly designed, which means the solar panels will be using an MPPT charge controller so they can always exceed the battery's voltage, then the solar system will always be able to bring the batteries to 100%, rashly assuming that you've got enough capacity for that to happen. If it can't happen simply because you're not getting enough watts per day from the panels...Well sure, that's the same thing as saying "I installed a ten amp shore charger, for my 500A battery bank. I don't know why it never charges fully!"

Watts is watts, the battery doesn't care what made them.

I think everyone understands this.

But a surplus of solar power is not a parameter you can "rashly assume". It's not available to everyone. I have no solar power at all on my present boat, and have no way to install any without unacceptable consequences.

mbartosch · 13-09-2018, 13:02

Quote:

Originally Posted by Dockhead

What kind of motor are you using it with?

I had outboard trouble this summer and think about electric dinghy power.

We are using a Yamaha M26 which seems to be a rebranded Minn Kota Riptide Transom trolling motor (12 V/40 A). Overall we are happy with the motor. It fits nicely in our locker box and can be handled and mounted by a single person easily.
Power (~0.5 kW) is sufficient for our needs. Typically we go at 75 % power, our 4 person dinghy (2.65 m length) gets about 3 kn of speed at max power and with the 40 Ah battery bank we get about 1.8 nm range.

Some corrosion problems with the transom mount screws but otherwise no problems and zero maintenance after three years.

john61ct · 13-09-2018, 13:11

Quote:

Originally Posted by Dockhead

a surplus of solar power is not a parameter you can "rashly assume"

Yes and high-usage systems combined with a small boat means strict upper limits, even just 600W can be hard to find space for.

Not to mention windage

and some owners don't like the way too many makes the boat **look**.

But ICE to 85-90%, followed by full sunny day day output by a couple unfolded blankets is a cheap and KISS solution for many not traveling arctic waters in winter.

Paul L · 13-09-2018, 13:27

Using foldable solar panels for a fulltime cruiser is just impractical. You take one of the prime advantages of solar, no maintenance, no worry, and turn it into a daily hassle. Tieing them securely everyday from the ravages of the afternoon thunder storms. Keeping all the tie downs out of the way to the clear passage to the bow so you can deal with an anchoring CF - what a pain. Plus most of the foldables energy density is pretty poor, ie you need a lot of surface area to get any decent wattage. Then after that you have find a space to store them below.

**Pete7** · 13-09-2018, 13:46

Quote:

Originally Posted by Dockhead

I think everyone understands this.

But a surplus of solar power is not a parameter you can "rashly assume". It's not available to everyone. I have no solar power at all on my present boat, and have no way to install any without unacceptable consequences.

Indeed, a couple of days of heavy rain and cloud will have me concerned and if it continues on day 3 then the engine needs to be started or shore power plugged in.

Quote:

Originally Posted by Paul L

Tieing them securely everyday from the ravages of the afternoon thunder storms. .

Which is how we smashed our suitcase panel (rigid panels) and this was in harbour.

**a64pilot** · 13-09-2018, 14:03

Quote:

Originally Posted by john61ct

Yep, those are my reasons, noise, fuel, wear & tear costs are high, compared to say a couple 80W folding solar blankets put out 3-4 days a week.

I don’t think you realize what his electrical load is.
I’ve seen pictures of his Nav station, and heard him post about the electronics he has and how they are all integrated etc.
He uses a lot of power, way more than average Mom and Pop cruiser.
So maybe a kilowatt of Solar may make a good dent, but that is only if they are out there every day and he isn’t going to do that.
He won’t even have a Bimini due to windage, and I can’t imagine life without one myself

Then imagine if you will temporary panels on a deck when your bashing to windward in 25 kt winds, taking green water over the bow?

Nope, if I understand Solar isn’t even a consideration, can’t make it work. Only real source of power is coming from burning Dino juice, cause if you won’t have a Bimini cause it slows you down, think you would tow a generator?

He is right about generator costs, but in truth look at it another way, how many hours have you run your generator per year on average?
I bet less than a 1000, cause at eight hours a day, that is over four months at sea, and I assume you work so that just isn’t possible?

Besides assuming you take very good care of it, I’d say that a 1500 RPM heavy duty generator will live closer to 10,000 hours than 5,000.

**StuM** · 13-09-2018, 16:38

Quote:

Originally Posted by ArmyDaveNY

Do you think the desulfication chargers will help solve the shortened life of the batteries? I've read some good reviews on some of them, in particular the ones from PulseTech.

I've read some actual tests on some of them, which essential indicated that they are of little or no benefit.

kmacdonald · 13-09-2018, 16:50

Quote:

Originally Posted by StuM

I've read some actual tests on some of them, which essential indicated that they are of little or no benefit.

I've heard that they are worthless also. No personal experience with them though.

john61ct · 13-09-2018, 22:47

Quote:

Originally Posted by Paul L

turn it into a daily hassle.

Few times a week not daily.

Yes but still worth looking at when the alternative is NO solar.

Only needed for off-grid lead, LFP makes no solar easy.

Space is the size of a 3" binder.

john61ct · 13-09-2018, 22:51

Quote:

Originally Posted by a64pilot

I don’t think you realize what his electrical load is.

Not talking carrying even 5% of that.

Just for the long tail, last 3-4 hours at say under 10A, crazy to think about running ICE for that.

If impractical then the two remaining choices are LFP (even if just for the hybrid long tail) or frequent replacement of lead.