There are not twice as many batteries in a apples to apples system. Two 6v batteries in series will do what 2 12 v in parallel will do.
I can certainly attest to this. Just not on my boat. I have a whole-house UPS setup that has 4 battery modules of 240vdc each, connected in parallel.Each module is 20x 12v 7ah SLA batteries connected in series.Each module has a 50a 4-pole circuit breaker, connected at 0v, 120v, 240v, and on a control line.I had two batteries short internally. This caused a the entire module to drain into the shorted cells, destroying 20 cells.It also caused the 3 other battery modules to drain into the short. However, as soon as the load passed 50a on the shorted module, the breaker tripped under load. It saved the 3 other modules but the breaker destroyed itself in the process. The UPS kept right on keeping on, without the shorted module, so with reduced running time.My basement filled with an acrid smell of sulfer and there was a it of haze in the air. This was from only two, small SLA batteries. Imagine the same situation happening in a smaller volume of a boat with much larger batteries, with more easily vented gasses and fumes. Not a fun place to be. This certainly highlights the need for circuit interrupters located at the power source. And also between parallel banks. The added costs of this very sane protection add up quickly so it's often better to fit a single large bank initially./Jason
On Jun 6, 2017, at 14:23, James Lambden james@electroprop.com [electricboats] <electricboats@yahoogroups.com> 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 fail ed 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.JamesJames Lambden
The Electric Propeller Company
625C East Haley Street,
Santa Barbara, CA
93103
805 455 8444
james@electroprop.com
www.electroprop.comOn Jun 6, 2017, at 7:40 AM, Jeff LaCoursiere jeff@jeff.net [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@yahoo.com [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
Posted by: Daniel Michaels <nov32394@yahoo.com>
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