I am looking for advice on what battery bank setup is the most reliable between series and parallel. I recently installed an electric motor in my Hunter 27 sailboat and have four lead-acid 12V 80AH batteries (for now) to power the motor. I am also looking for advice for a solar panel(s) and solar charge controller that can handle this type of battery bank setup.
BATTERY BANK SETUP
- Thread starter jr22553
- Start date
Lot of questions. The biggest question is what kind of power does your motor need? How big is the motor? How far do you intend to motor? Is this a DIY job or did you buy a system from a manufacturer?
Series wiring will increase voltage but the amperage will remain the same. Parallel wiring does the opposite, voltage remains the same, with the amperage will increase.
With the 4 batteries you have, you can get 80 ah at 48 v if all four are in series. Or 320 ah at 12 v in parallel. Or you can get 24 volts and 160 ah if you have 2 pair of batteries wired in series and each pair wired in parallel.
Regardless of the configuration, the battery capacity you have is likely very inadequate for the electric motor if you intend to motor any distance, meaning more than just motoring out of the marina.
An 80 ah battery has only 40 usable amphours. Thus, if maxed out the 320 ah you have has only 160 ah that are usable.
The amount of solar you will need will depend on how big the battery bank is. As a guide line you can expect on average to get 3 times the nominal capacity of the panel per day, i.e., a 100 watt panel can be expected to provide 300 watt hours of power per day, more on bright sunny days in the summer, much less to zero on cloudy days. Once you know the amount of power you need for the motor, you can determine the battery size, then you can match your charging sources to your power needs.
Edits: Corrections in blue.
Series wiring will increase voltage but the amperage will remain the same. Parallel wiring does the opposite, voltage remains the same, with the amperage will increase.
With the 4 batteries you have, you can get 80 ah at 48 v if all four are in series. Or 320 ah at 12 v in parallel. Or you can get 24 volts and 160 ah if you have 2 pair of batteries wired in series and each pair wired in parallel.
Regardless of the configuration, the battery capacity you have is likely very inadequate for the electric motor if you intend to motor any distance, meaning more than just motoring out of the marina.
An 80 ah battery has only 40 usable amphours. Thus, if maxed out the 320 ah you have has only 160 ah that are usable.
The amount of solar you will need will depend on how big the battery bank is. As a guide line you can expect on average to get 3 times the nominal capacity of the panel per day, i.e., a 100 watt panel can be expected to provide 300 watt hours of power per day, more on bright sunny days in the summer, much less to zero on cloudy days. Once you know the amount of power you need for the motor, you can determine the battery size, then you can match your charging sources to your power needs.
Edits: Corrections in blue.
Last edited:
My error, should have said series, need to proof read before posting.
Yes, I knew it was a typo of sorts, just giving you a hard time.My error, should have said series, need to proof read before posting.
I purchased a 10kW motor from a manufacturer. The distance to motor from my slip to open water (Potomac River) is less than 100 yards. I have not been to many places on the river so knowing how far I intend to motor is going to be new to me with this motor once I start visiting other places this summer. If I have to put a best guess on intended distance to motor, I would say around two to four miles or less.
Assuming you have a prop that is pitched correctly for the motor, and you motor at half the 10kw you will probably get about 2-3 mph in flat water with no current. To motor for one hour you will need 10kw hours of battery capacity in order to not excede the 50% limit on LA batteries.
You currently have about 3.84 kWh (80ah * 4 * 12v) at full capacity, a little less than 2kwh usable. It will be necessary to increase the capacity of your battery bank five fold in order to reach that level. That's a lot of lead.
Also consider how much power you might need when you find yourself 10 miles from home, it starts raining, no wind and the current is against you.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 23,034
Reading this post is kind of like marching into a mine field with no map and no experience defusing mines.
@jr22553 perhaps it would be helpful to you to get an understanding of DC current and how it makes your new motor move your boat. There are any number of excellent sources found on the web, in a library, or at a community college. Batteries on boats or not complicated, just operate with defined limits.
@jr22553 perhaps it would be helpful to you to get an understanding of DC current and how it makes your new motor move your boat. There are any number of excellent sources found on the web, in a library, or at a community college. Batteries on boats or not complicated, just operate with defined limits.
You might get a 1 1/2 hours out of the bank before you hit 50% long as you pay attention to the amp draw, 20 amps per hour or 960 watts. Your speed will probably be in the 2.5 to 3 knot range.
If you dont have battery monitor that came with your motor I'd highly recommend a Victron 702 monitor. Best $150+ you'll spend, it becomes your fuel gauge.
Solar, buy a couple of panels that are at a minimum 24 volts & wire them in series.
Almost any MPPT controller will do. I personally like the Midnight Kid for the way I use my boat due to having a user friendly menu. Victron also has good controllers, reasonably priced but you need a smart phone app to adjust the parameters.
FWIW, I have 320 watts of solar on my electric boat & it takes care of all my power needs majority of the time.
What voltage does your new motor require? 36v or 48v? It seems to me that the new boats that are building with electric motors are 36v or 48v for inboards. You need to wire your 12v batteries in series to match your motor voltage requirement.
I'm curious, at one-tenth the rated power, you can get 2.5 to 3 knots of speed, or about half the hull speed? That seems low to me. My Yanmar needs closer to half the rated power to achieve the same speed.
Second Star has 2 150 watt panels with Victron controllers. The app not only allows for setting the parameters, it provides real time information on panel voltage, output, network output, and battery voltage in addition to storing a 30 day history showing daily output with the amount output at bulk, absorption and float stages.
On good day in the summer the most the panels have produced is about 1 to 1.2 kWh, just enough to recharge about an hour's worth of slow motoring.
Another consideration is the locale. The Potomac has both river currents and tidal currents, fine if he current is with you.
By far the most convenient but not the only way. You can make adjustments with a Victron MPPT Control Display and a VE.Direct cable. These were necessary for the older BlueSolar line and can also be used with the new SmartSolar.
I could do easily 3-4 knots at less than 2000 rpm with a 33' boat and a 3GM30. 1800rpm is about 2.5kw of power from the Yanmar, thats half the rated RPM, but about 12.5% of the power.
Well electric is quite a bit more efficient. Fortunately they do not have the efficiency losses when compared to a ICE. The fly in the ointment has & may always lie in battery technology when range is one of the considering factors when comparing electric to a ICE.
Far as tides/currents, Sailing is alot like fishing. One learns to play the tides/currents if they want to catch fish.
Last edited:
These questions remind me of the time I decided to upgrade the battery system in our boat. Without going through all the different iterations and configurations that I went through while spending large amounts of money on things that were ultimately bad design ideas I actually took a serious look at what it was I was trying to accomplish before spending another dime on the system. Of course, that lead to spending some serious money that I should have spent from the get-go had I actually spent the time to do the research needed to end up with a system that I eventually (this season) will have installed. Have I learned from my mistakes? I would say that I have, but if I had only thought out and taken the time to research all the aspects of what I was about to do I could have installed the right system on day one. My biggest mistake was I was trying too hard to save money. As I read through this forum I see time and time again others doing the same thing that I did over and over. With that said my comments are not meant to be negative, but to say I think it is prudent when we are faced with boat upgrades that we should all take the time and try to get it right the first time instead of doing things twice to get it right. This forum can be a great resource for spotting mistakes before we make them: while gleaning the knowledge from others that have already been down the road we are about to travel. Good luck with your project.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 23,034
Such wisdom often comes from having made mistakes. Thank you for sharing. Perhaps some will heed your advice. I expect some will say. What does he know.
Such is life. Darwin observed such things. He was acknowledged as being insightful.
Boat electrical systems are at once both very simple and complex, simple when you understand it and complex while learning. The BoatHowTo.com site has a course on boat electrical systems that some may want to pursue. Nigel Calder is one of the principals on the site.
Life is too short to worry yourself about the state of charge of your sailboat's batteries, the amount of sun shining or the angle of your solar panels. Save yourself a lot of money and work and buy yourself a 10-15 HP outboard engine and attach it to a bracket that can lowered into the water and you will be able to take your boat as far as you want and not be worried if you can your boat back home when the wind dies down.
A refreshing post with an alternative view.
But I'm not sure I agree. We sailed a friends T37 in the ocean from St. Lucie inlet to Greenport LI. Almost all our power was solar. He had a water maker and refrigerator/freezer plus the stereo was going the whole way (Have you ever had acoustic hallucinations from lack of sleep?). We did not lack for power. We only ran the engine for the water maker, and to increase speed when necessary. I was skeptical but was impressed with the power of solar.
As for electric propulsion, a friend bought a sailboat with electric propulsion. He was late or non-existent at post race parties.
But I'm not sure I agree. We sailed a friends T37 in the ocean from St. Lucie inlet to Greenport LI. Almost all our power was solar. He had a water maker and refrigerator/freezer plus the stereo was going the whole way (Have you ever had acoustic hallucinations from lack of sleep?). We did not lack for power. We only ran the engine for the water maker, and to increase speed when necessary. I was skeptical but was impressed with the power of solar.
As for electric propulsion, a friend bought a sailboat with electric propulsion. He was late or non-existent at post race parties.
Last edited:
This thread seems to have gone way off track. @jr22553 says he already installed the 10 kW electric motor. There isn't any sense in discussing propulsion options or how far he is going to get with it until he sorts out his battery needs. He suggests that he has 4 Grp 27 (80 ah) lead acid batts. These will be woefully inadequate as @dlochner has already pointed out. First, he needs to identify the voltage of his motor so he can figure out how many 12v batts need to be put in series to equal the propulsion system. Then he needs to figure out how much space he has to expand his battery capacity because he will need ALL that his boat can carry and more. I'd suggest that he needs to re-think his battery purchase. He could probably use 2 of his original 12v batts for house loads. His propulsion system is going to need a much more sophisticated set-up than 4 12v batts at 320 ah.
Then he is talking about solar energy generation. He will need as many solar panels as he can fit on his boat. I'd suggest he will need a 20 amp MPPT controller with as many panels as he can fit on the boat, say at least 200 watts or more.