Boats are different from cars or golf carts. If there is a problem on a Lithium Battery in a car, the owner pulls to the side of the road and in a minute or two can be out of the car.
If there is a problem on a golf cart, the drive can slide of the seat, and be out of the cart in seconds.
In a boat, you live with any problem that the boat has, or you abandon ship. Neither seem appealing to me. Because the risk is greater aboard a boat, the work has to be done to a higher standard to prevent the risk from happening in the first place.
When I took the Marine Electrical Certification from ABYC, 52% of all boat fires originated in the electrical system.
Electrical installations comprise both the parts and installation. It is more often that the installation gets customers into trouble than the parts themselves. Installation requires careful design, and mounting of the components and this is often done by the boat owner, with no previous electrical experience. So everyone looks to groups like this, youtube videos and internet posts and pages to educate them on a very steep learning curve.
To say that any one component is completely safe in any installation is misinformation. you can drop a wrench on any battery and get yourself some pretty spectacular fireworks in your boat.
Complacency is the biggest danger aboard a boat. When you know there is a danger, then don't do anything about it, you are complacent. This could be from not being aware of your batteries, to not being aware of your radar, or any other installation or operation aboard a boat.
The FACT that everyone should be aware of, is that batteries have a 100% failure rate, after which they get replaced. Batteries can fail gracefully or catastrophically. When we learn of catastrophic failures, we go back to the drawing board and start engineering a solution.
The FACT that everyone should be aware of, is that batteries in parallel can fail catastrophically. Batteries can fail catastrophically if they short a cell, and the charger keeps charging in series.
THe simplest way of building the safest battery pack is to employ Pure Lead Technology which I understand will never short the plates so are safe in parallel or series operation. However I still employ every thing we know and have learned about batteries, including Battery Temperature Monitoring, Battery Voltage Monitoring and Battery Balancing. If there is a safer way of building a boat, why would you not look into it?
The single best way of insuring that a battery does not fail catastrophically is to have a temp sensor on each battery, enabling any charger that affects the battery. If the battery gets hot, then the charger turns off. This is really simple way of insuring the safety of a boat. The manual way of doing this? Get a digital Infrared Point at it thermometer and monitor the battery near the end of its charge cycle. Get a voltmeter and monitor the voltage at near the end of the charge cycle. And if you ever smell an "electrical smell" get it repaired quickly, Turn off all switches and all chargers. Ventilate the boat. And sometimes it might be better to wait, than try and disconnect a battery because disconnection of a battery can cause a spark and if hydrogen gas has built up, this can be a point of ignition. If in doubt, hire a qualified marine electrician to take care of the situation.
But whatever you do, don't be complacent to any danger that anyone has discovered. Use this information to make your boat safer.
Batteries in parallel can fail catastrophically because the good battery discharges into the bad battery. It takes less than 10 amps to maintain a thermal so hot that you can start a fire, even without a hydrogen explosion.
To be aware of an issue, and to ignore it is Complacency. We have additional responsibility to the crew and guests aboard a boat that go much farther than golf cart or car owners.
If you see information out there that you don't like, don't just ignore it, look into it.
I estimate that about 10 percent of AGM, GEL, or Flooded Lead Acid batteries short a cell. Just because the other 90 % of these batteries worked flawlessly over years of ownership does not negate the fact that a small percentage of these batteries fail in a way that if you keep charging them, you can blow up the battery or catch the boat on fire.
Diesel boats that employ chargers with 3 leeds, but only one, and sometimes no temp sensor have a flaw, which (in my opinion) is the most common electrical flaw aboard a boat. The batteries are usually interconnected by a 1/2/Both battery switch which is sometimes inadvertently left on. You now have a potential problem that can cause ignition.
The good news is that with the combined experiences of this group, we can make our electric boats much safer than your neighbor's diesel boat.
Be Vigilant and make sure that your batteries are not failing you by monitoring them. When you feel heat, you have a problem. Its a simple as that. And if you have a problem that affects the most important component aboard your boat - propulsion - do something about it. Fix it and keep your boat, your crew, and your guests, SAFE.
James
James Lambden
The Electric Propeller Company
625C East Haley Street,
Santa Barbara, CA
93103
805 455 8444
james@electroprop.com
www.electroprop.com
I love the title of this thread: "Feasible to change to 6v golf cart batteries?"
Simple answer: Yes.
Basis? Many of us simply configure our drives as with golf carts and even use the same components. Perhaps billions of hours of successful golf cart use and thousands of successful hours on boats.
Going with golf cart batteries is one of your best "bang for buck" options and about 3-4x cheaper per KWH than using the GPL-31T-2V Lifeline 2v batteries that have been suggested earlier.
And don't be afraid of parallel solutions despite the warnings…I ran with 2 permanently-linked parallel 36v golf cart battery strings for at least 10 years before switching to 10x paralleled 48v lithium permanently-connected (though fused w/10amp fuses each half-module) lithium modules.
There is a lot of misinformation out there. One I read here suggested that a shorted lead in paralleled strings of lead acid are somehow more dangerous than a shorted cell with paralleled batteries----As if that single shorted cell causes more current to flow from one string to the other because they are 48v nominal strings in parallel vs 6v batteries in parallel. In fact, with more series connections in a string, less current would flow into a shorted cell in a paralleled string than if batteries were "buddy paired" and one had a short. Also, a 2v cell short seriously stresses buddy pairs but doesn't stress series strings in parallel---e.g. a 2v cell short would only be 1/4volt stress on each of 8 golf cart batteries in a paralleled series string. Things would settle quickly, without danger.
Again, I ran my boat for several years with 6 series T-105 batteries in parallel with another series string. Another friend ran his boat with 3 parallel 36v strings and did hundreds of miles of cruising and charge cycles over 8-10 years before recently changing to a 6x parallel lithium configuration like mine---actually it's technically 12x parallel: 12P(12S2P) of Enerdel lithium cells.
YMMV-
-MT, Portland, Or.
www.evalbum.com/492
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