I should clarify that statement.
A 6 volt battery can be monitored manually. What I should have said - I have yet to find a way of monitoring a 6 volt battery with commercially available equipment. To get the voltages displayed on a screen at all times is more difficult to do because 6 volts doesn't have many practical applications so there is very little 6 volt equipment out there. It is easy to monitor under 5 volts because any computer chip can do that. To go over 5 volts you have to put a voltage divider in. You have twice as many individual electrochemical devices to monitor when using a 6 volt batteries compared to 12 volt batteries. Also twice the interconnects between the batteries.
But it is less about monitoring, and more about balancing. There are no 6 volt balancers available.
You have good experience with batteries - but most don't. Not everyone is interested or willing to accept the risks associated with equalizing a battery by taking it over-voltage, against the manufacturer's recommendations. Most don't know how long it should be left at the elevated voltage or what to look for. It is vital to have good ventilation while equalizing to dissipate any hydrogen gas buildup.
A lot of people are now running AGM batteries, and if they are equalized, there is a risk that you can activate one of the pressure relief valves, and it is my understanding that when one of those valves opens, it will not close again, and that can ruin an AGM or GEL battery. What voltage, for what time, makes one of these valves open, is different for every battery, and every different environment, or charge discharge cycle, that the battery experiences.
There is no scientifically safe way to accurately, automatically, equalize a battery for maximum effect. It is all guesswork. This is why we choose to automate as much as possible with the battery charging.
Many 48 volt chargers are now finishing at up to 64 volts and terminating with a delta voltage over delta time algorithm trigger. That might be ok on a 12 volt battery, but when a 48 volt string goes out of balance and the voltage is up at 64 volts on the string, it is very easy for one of the 12 volt batteries to go up to 20 volts. Obviously, that is not good.
The solution is battery balancing, and accurate battery charging resolving to the logic of each individual battery.
The safest way is to have separate battery chargers with dedicated temp sensors on each battery. That way if the battery gets hot, the charger for that battery knows to turn off the charging.
I believe firmly that each electrochemical device that has the potential to catch on fire or emit explosive gases should be monitored for temperature, and chargers should be disconnected in the event of a thermal.
Basically what I am saying is that the logic from data from each electrochemical device (battery), should be used to enable the charging circuit. Whether it is lead acid, AGM, GEL, Lithium or the best of all of them PURE LEAD.
The battery that sets the standards for every other battery to look up to is the American made Northstar.
Northstar Batteries are up to 210 amp hours. Northstar Batteries do not have a high charging requirement and can accept a charge of 10 percent of their amp hour capacity.
Pure Lead does not fail with shorted plates so the likelihood of a thermal if very small.
Northstar Batteries are more efficient than AGM batteries so need special charging algorithms that truncate the Bulk Charge by current rather than by time. A lot of chargers will overcharge a Northstar Battery which will reduce battery life.
Northstar batteries are made to last 10 years, and if properly looked after I think they could last as much as 15 years or more, pretty much making the battery maintenance thing, a thing of the past.
Good Batteries, with good chargers will the proper algorithms significantly reduces the risk of storing electrical energy on a boat.
For those of us who have 48 volt systems, without monitoring or balancing equipment, it is a really good idea to check individual battery voltages and case temperatures of the batteries once a month, throughout a charging cycle. Look for anomalies. Most battery problems can be prevented by balancing and not over charging.
When using a 48 volt charger, all the batteries in the string share the entire voltage as a function of their resistance.
When a battery fails, it gets spongy - the voltage of the weakest battery in a string goes higher than the rest when charging, and lower than the rest when discharging. Voltage fluctuates more for the weakest cell in the pack.
When a 48 volt charger is charging, the weakest battery will steal the voltage from the strongest batteries. Once the weakest has taken the voltage, it starts to gas off. The weakest battery gets ruined by going over voltage, and all the other batteries get ruined because they get starved for voltage.
Without balancing, the batteries in a string go out of balance incrementally more each battery cycle.
Its a real simple solution. 4 chargers with temp sensors with the proper algorithm is safe, effective and the best thing for the life of the battery. Just make sure that all of the chargers are working though.
OR a Battery Balancing Solution with enough balancing current for the batteries that you are using.
Whether manual or automatic, for maximum life, batteries need to be monitored and balanced regularly.
Proper Battery Monitoring will avoid the scenario when you leave the dock and you think your battery is full, but you have one failed battery in the string and you get stranded with no propulsion.
My preference is an automated system because it is on all the time, in real time, and will prevent batteries from having problems in the first place, but will catch the anomaly and give you fair warning that there is a problem so you can fix the problem before it becomes an issue with the navigation of the vessel.
Electroprop displays all 4 battery voltages on one color display with about 30 other parameters so you know what you have. No more guessing or worrying about what the batteries are doing because you have the information available so you can make informed decisions for the safety of the vessel and its crew.
The best thing you can do for battery (after balancing that is) is to have solar.
Decrease the absorption time on the solar charge controller once the battery has been fully recharged. Let the sun do the work for you. Every day the battery goes through a light charge. Over time, on a graph of voltage, it looks like a heartbeat.
The AGM batteries on Kapowai last over 10 years and were only charged with solar.
The flutter of a little charge every day is way better than holding a battery on float for the battery pack and may even be better than doing a regular equalization.
It is no accident that batteries on boat last 2 to 5 years on average. Look after them, and good batteries will last ten years or more. It is worth every penny to take the time or buy the equipment to automate the process.
James Lambden
The Electric Propeller Company
625C East Haley Street,
Santa Barbara, CA
93103
805 455 8444
james@electroprop.com
www.electroprop.com On Jun 10, 2017, at 12:17 PM, king_of_neworleans wrote:
James, what exactly do you mean when you say a 6v battery cannot be monitored? If you can monitor a 12v battery, then surely you can monitor any battery with any number of cells, right? I check the voltage of each battery before and after every outing or full charge, and occasionally even when on float. A BMS to do this automatically and shut down the system when it is in a fault condition would not be rocket science to implement. I'm sure you have a reason for your statement, but a clarification would be nice for us less knowledgeable types.
Certainly, keeping it simple is better. I agree that parallel wiring has serious drawbacks. And fewer user maintained connections is better, of course. But often the form factor of the 6v battery, with the fairly large amp hour capacity, presents advantages for a particular installation. I personally hate lugging 4D or 8D batteries around. A GC2 or even an L16 is much easier to handle. Honestly, if cost was less of an issue AND I wanted a higher capacity bank at the same voltage, I would go with single cells. Yeah, more connections. But if properly implemented and occasionally checked and tightened if needed, and using nice fat cable, it's not such a terrible thing. I check all my connections every time I check electrolyte level or SG. Only takes a minute. With a 48v bank of 6v batteries, I have 8 batteries connected. With 12v batteries, I would STILL have 4 batteries connected. So it's not like 12v batteries eliminate a possible bad connection. They only reduce the not so very high risk by a factor of 2.
---In
electricboats@yahoogroups.com, <james@...> wrote :
There is no way to monitor a 6 volt battery.
Batteries in series go out of balance over time. One of the batteries will go to a very high voltage, and the rest will be low. The high voltage battery is at risk of gassing off and can experience catastrophic failure.
Most of the danger comes at the end of the batteries life, but batteries sometimes fail prematurely. A lead acid battery system should be monitored just like every Lithium system out there.
I do not recommend 6 volt batteries. There are twice as many batteries in the system, so twice as many interconnections, and much more to go wrong with a system like this.
Batteries in parallel have issues too. Hardwiring batteries in parallel is problematic. when one battery fails, the other will be ruined by the failure. In worst case scenarios, the failed battery emits hydrogen gas and the smallest spark can set off a catastrophic failure.
Please be careful and monitor every battery on board your boat for temperature and voltage and keep your electric boat safe for you and your passengers.
The technology exists to have a safe battery bank. Pure Lead 12 volt Batteries in series with monitoring. Its really simple, and safe.
James
On Jun 6, 2017, at 7:40 AM, Jeff LaCoursiere
jeff@... [electricboats] wrote:
That isn't correct - 12 x 6v in series would be 72v. The OP was originally correct - 2 sets of 6 x 6v, the two sets in parallel.
I'll throw out a guess that you could then keep your original chargers, and use them in the same manner - just charge each 36v bank just like before.
j
On 06/06/2017 07:33 AM, Daniel Michaels
nov32394@... [electricboats] wrote:
They would all be in a series. One battery charger. Same as a golf cart.
I recently bought a 2002 Canadian electric boat Fantail Launch. It has 36v system, with two groups of three 12v batteries in series, then the two groups linked in parallel. There are two ProTournament series 3-step marine battery chargers, each dedicated to one of the 3-battery groups.
I fear the current six 12 v Interstate batteries are approaching end of life, and I'm interested in changing over to the 6v golf cart batteries with the higher amp hours capacity.
I need a 36 volt system for the current motor. So, would I be linking 12 of the 6v batteries: two series of 6 in parallel? Would I need two more charges to charge the added 6 batteries?
Thanks, and Regards.
M Kirkwood
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