Monday, February 20, 2017

ELECTRIC PROPULSION: SOME THOUGHTS ON ELECTRO SAILING: Part Two

Now that I've shown an example of how I am able to easily Electro-Sail with BIANKA when the winds fail to show up. I'll discuss the components that enable me to achieve it and some of the things I have learned in the past nine years since I converted BIANKA to Electric Propulsion.

My Thoosa 9000 EP system specifications were designed  for 20 miles at 4 knots. This was using my 8A4D AGM batteries only. I have never checked if this was the actual case nor do I want to unless it becomes necessary. BIANKA is a sailboat and I always prefer to use the sail for propulsion. Another reason to avoid trying to push the battery bank close to depletion is you decrease the amount charge cycles of the battery bank. As this chart below shows:


It's about saving the amps champs! But, that does not mean I just use the EP system to get into and out of the harbor. Which is very easy for an EP system to do. I tend to leave my home harbor for other destinations not just day sails. But, EP makes that easy to do too.

So what do I use when I feel the need to Electro Sail? I will first start out under battery power alone. I watch the XBM battery monitor to see when my battery back has dropped down to about 75% battery capacity from the 100% fully charged condition I started out with. This is about two hours after I have started motoring. As noted above this habit allows me to have more recharge cycles out of the battery over it's lifetime. This is better than depleting the bank to down say 50%. It also reduces the amount of time spent to charge the battery back up to 100%

So when the battery bank has dropped to the 75% capacity.  I fire up the Honda 2000i generator and plug in the ZIVAN NG-1 charger into it.
The ZIVAN has turned into a real workhorse and has been very reliable. When I first installed the Thoosa system back in 2008 I was concerned about what would happen if the charger went bad and could no longer charge the battery bank while on a cruise. So I bought a backup NG-1. I'm happy to say that the backup has remained in it's box for these past nine years and has never had to be put into service.  The ZIVAN also works well with the Honda 2000 generator. When I use it for Electro Sailing on BIANKA it functions as a power supply pushing out 15 amps of max current to propel the boat acting as a power supply to push the boat along. It's output is just 900 watts well within the maximum 1600 watts continuous rating of the Honda generator. As the graph below from one of my harbor tests shows that 900 watts allows me to motor BIANKA at around three knots without drawing any amps out of the battery bank:


 In fact it allows me to operated the Honda Generator in ECO mode which makes the one gallon of gas in the Honda generator last for about four hours. I have operated the ZIVAN in this full out mode for hours at a time without issue. BIANKA will move along quite nicely at this speed until the fuel runs out. Of course despite being a fairly sophisticated charger the ZIVAN does not know it is being used only has a power supply to push BIANKA along on a windless day. It thinks it is still charging a battery bank. Which brings up something one has to be on the lookout for when Electro-Sailing with this and other chargers. Because the charger never sees the battery being charged at some point it will disconnect. Thinking the battery is not charging it will timeout. It takes several hours to reach this conclusion and it is easily reset by unplugging it from the generator and plugging it back in. Then it is good to go for another several hours.
 One of the nice things about having Electric Propulsion is how easily it is to modify components of the system or change operating modes. Because the ZIVAN's output is limited to 900 watts it means I am not able to take advantage of the full 1600 watts continuous output of the Honda 2000i. So I am contemplating buying a 48 volt 1500 watt power supply to use when it looks like I will have to operate on an extended Electro-Sail mode. I expect it should move BIANKA along about 4 knots. I'll test and post about that hopefully some this upcoming season.


6 comments:

svfugu said...

I am curious to know how the 48V power supply will fare if connected in parallel with the 48V nominal AGM pack. Wouldn't a fully charged AGM pack be at about 51.2V?
I still haven't electro-cruised my boat (16x 100ah LiFePO4 pack, also at 51.2V resting charge)
If the power supply is outputting a steady 48.00V, wouldn't that make the batteries try to flow toward the power supply a little? What model power supply are you looking at? Is it adjustable?

Is this the sort of power supply you are considering?
http://www.trcelectronics.com/View/Mean-Well/RSP-1600-48.shtml


I am tempted to give the battery charger the boot altogether and opt for just a CC-CV power supply sized for my 1600W continuous generator or 15A shore-power circuit.
My reasoning is that the lithium BMS can disable the power supply at high-voltage cutoff and the charge profile of LiFePO4 chemistry is pretty much constant current at C/3 to 3.6V/cell, then constant voltage until the current drops to C/100 (1.00A in my case). There aren't any fancy charge-pulse or anti-sulfation battery conditioning routines to consider.

My PFC1500 only outputs 1200W at 115V AC, which tops out at about C/5 (~22A charge) which gets me quite close to full (over 90%). Moving to power supplies is also cheaper than battery chargers, which allows for carrying a spare. Some of these are also parallelizable which means perhaps using a series of smaller ones that can come online as needed and share the load, AND provide active redundancy. Instead of a single 1600W 30A supply, use 4 10A supplies and a microcontroller like an arduino to bring 2nd third and 4th ones online/offline as needed.

I am excited now Need to plan this out more. Thanks for the post!

Cheers,

/Jason

Capt. Mike said...

One of the reasons I start under battery alone when Electro sailing is so I bring the AGM bank voltage down so that the ZIVAN NG-1 battery charger will see an under charged battery bank and go into it's full 15 amp output mode when I plug it in. As I mentioned in the post I operate under battery alone for about two hours. I'm not sure if Lithium will behave the same way as the AGM's or standard lead acid batteries.

It's possible you will be able to just us a power supply for charging with Lithium. Though you would need a good Battery Management System (BMS) and a power supply that can be controlled by it. Since I'm currently sticking with my AGM's I have not looked into it. But, my NG-1 charger can also charge Lithium batteries with an easy module swap. Should I decide to switch to them at some point.

I would be careful with your choice of the 1600 watt power supply because it bumps right up to the 1600 continuous limit of a Honda 2000 it might trip out when in operation. It's one of the reasons why I'm looking at a 1500 watt unit as it has 100 watts of overhead.

As far as parallel supplies you will need to choose wisely. Not all supplies can be paralleled. As I found out when I tried a 600 watt power supply to use in parallel with the ZIVAN unit. It sensed the voltage of the ZIVAN and did not provide any output when the ZIVAN was on. That's why this year I'm looking at the 1500 watt PS for testing.

svfugu said...

I read a few articles on the different paralleling methods and for the simplest "just connect two sources to the same load" method, the output voltages need to be very closely matched and behave the same as regards voltage drop under varying load. if the supplies are identical then once the voltages are properly trimmed, it should be fine. However, if the voltage sources are different technologies (a power supply and a battery charger) then curernt limiters can kick in or power can start flowing in the wrong direction, possible damaging the supply. Many of these supplies support current sharing, this one up to 6 units. If they do support it, they say so explicitly in the datasheet.

Another thing to watch for is output voltage trim. Some supplies are 48.0V output and can be trimmed up to 110% of output voltage, so 52.8V. That is fine for running off a generator as the voltage will be above the pack voltage. However, if I want to replace my charger, then I need to get a supply than can put out up to 57.6V (3.6V/cell charge voltage). My BMS has a high-voltage-cutoff pin that can drive a relay on the AC input side of the power supply which should prevent overcharging the cells.

There certainly are some neat products out there for the person willing to learn how they work and can integrate them into the boat's power system. This just highlights one of the big advantages of electric propulsion. As you have mentioned in this and several other blog psots, we can upgrade individual components of our system as we go, as we learn more about the operational envelope our boating activities are in, and as budget allows.


Capt. Mike said...

One of my driving concerns is Keeping It Simple. I do recognize the advantages of Lithium but,I don't like the complexity of trying to keep them charged namely the BMS. Knowing the vulnerability of electric circuits to things like nearby lightning strikes I try to keep things as simple as possible and reliability has high as possible. My Zivan has proven itself to me for charging and Electro-Sailing. So I'll keep using it for most of my needs for now. The new 48 volt power supply will just be used when extended Electro-sailing is required. Personally, I only want to deal with one component (supply). So a single 1500 watt supply should meet my needs. Though perhaps by the next time I need to replace the battery bank I'll go with Lithium. The thing that's nice about EP is the choices you have.

Pajo Gazibara said...

I am curious what potentiometer you landed on? I initially used the curtis lever type on Cinderella, but I found that it is rather annoying that the lever likes to slide back to "neutral" I am thinking about going with a dial, is that what you used?

I also like the idea of not worrying about the inevitable tangling of sheets with the lever.

Capt. Mike said...

Pajo:

The Potentiometer came with my ASMO Thoosa 7000 system. It's pretty robust unit but, I can not find any manufacturer name on it. You might want to contact http://www.clean-e-marine.com about it since they put the system together. I agree the round control is safer with lines in the cockpit. Here is a picture of my speed control: http://biankablog.blogspot.com/2010/07/what-helm-part-1.html It has worked fail for over eight years.