TBammer
Nov 29, 2015Explorer
12V vs 6V
Recently bought our first travel trailer, and it has been quite the education, including understanding the dual electrical system. One thing I am thinking about doing is adding a 2d battery. I have ...
SoundGuy wrote:ktmrfs wrote:
If you dry camp a lot, then a pair of 6V has an advantage of more AH ...
... and the ability to withstand hundreds of discharges to less than 50% of capacity. Something 12V aren't real good at.
Also, if you intend to run a very heavy load (>100A) like inverters etc. for > a few minutes at at time, and do it fairly often then 12V offer an advantage in that they have lower internal resistance and are much better at high current draw situations.SoundGuy wrote:
I would be interested in seeing supporting documentation to both these claims as my primary interest in upgrading to dual batteries from my current single G27, aside from the fact it's now 8 yrs old, is that I am now running a 1K inverter for those times we don't have on-site shore power available.ktmrfs wrote:
looking at the Trojan website, cycle life if a pair of GC2's discharged to 30%SOC is around 500 cycles IIRC. So in terms of useable AH 6V has an advantage in cycle life and capacity over most 12V. Most 12V even the trojan's, cycle life degrades rapidly beyond 50%DOD. So a 250AH 12V has around 125 \"useable AH\" per cycle with reasonable life. While a 250AH 6V bank has 180-200 useable AH per cycle for the same or higher cycle life.
And how many of us will ever do enough camping to get to 500 cycles? Golf carts, yes, campers, not many of us.
As for high current discharge, myself and several others have gone through that with 6V. A pair of 6V will handle a 800- 1000W load down to about 80%SOC before dropping below the trip voltage on most inverters. Get's very frustrating when the bank needs to be almost fully charged to run the microwave for a few minutes. A single 12V will do better than that. for 1000W load, 4GC is a better choice. They will run 1000W inverter down to around 60%SOC. But a single or pair of 12V will do that as well will ease. and Four 12V will handle that with lots of margin.
Which battery (6V or 12V) best works for you really depends on what your needs are and how you intend to use them.
For me, battery \"cycle life\" is irrelevant considering our dry camping is limited to perhaps 3 - 4 occasions each season that have us camping for a few days without shore power, for reasons I described earlier, not because we want to but because we have to. However, high power discharge, albeit brief, is important because when we're without shore power I would like to use my 1000 watt inverter to power a toaster (620 watts measured) or coffee machine (560 watts measured) or my wife's hair dryer (350 watts measured, on low). One concern though is whether even dual G31s would offer sufficient capacity to remain above 60% SOC those times we also run a fan or two during really hot weather in lieu of A/C. With my current G27's SOC at 80% or higher the inverter will handle these appliance loads without protest but on one occasion I had forgotten to force the fridge to gas so when it's 300 watt electric element load was added to the toaster load the inverter's incoming voltage dropped below threshold and the alarm began to squeal. As you say - frustrating, particularly when the battery SOC was well above 80%. The microwave oven we don't care about but if replacing this G27 with a pair of G31s will allow me to power these appliances for a few minutes each once or twice a day along with a few hours of fan run time then that would seem to be the better choice for me than a pair of 6 volt GC-2s which according to your explanation won't handle high power discharge as well.
Thanks for the help - great info! :)
SoundGuy wrote:ktmrfs wrote:
If you dry camp a lot, then a pair of 6V has an advantage of more AH ...
... and the ability to withstand hundreds of discharges to less than 50% of capacity. Something 12V aren't real good at.
Also, if you intend to run a very heavy load (>100A) like inverters etc. for > a few minutes at at time, and do it fairly often then 12V offer an advantage in that they have lower internal resistance and are much better at high current draw situations.SoundGuy wrote:
I would be interested in seeing supporting documentation to both these claims as my primary interest in upgrading to dual batteries from my current single G27, aside from the fact it's now 8 yrs old, is that I am now running a 1K inverter for those times we don't have on-site shore power available.ktmrfs wrote:
looking at the Trojan website, cycle life if a pair of GC2's discharged to 30%SOC is around 500 cycles IIRC. So in terms of useable AH 6V has an advantage in cycle life and capacity over most 12V. Most 12V even the trojan's, cycle life degrades rapidly beyond 50%DOD. So a 250AH 12V has around 125 \"useable AH\" per cycle with reasonable life. While a 250AH 6V bank has 180-200 useable AH per cycle for the same or higher cycle life.
And how many of us will ever do enough camping to get to 500 cycles? Golf carts, yes, campers, not many of us.
As for high current discharge, myself and several others have gone through that with 6V. A pair of 6V will handle a 800- 1000W load down to about 80%SOC before dropping below the trip voltage on most inverters. Get's very frustrating when the bank needs to be almost fully charged to run the microwave for a few minutes. A single 12V will do better than that. for 1000W load, 4GC is a better choice. They will run 1000W inverter down to around 60%SOC. But a single or pair of 12V will do that as well will ease. and Four 12V will handle that with lots of margin.
Which battery (6V or 12V) best works for you really depends on what your needs are and how you intend to use them.
For me, battery \"cycle life\" is irrelevant considering our dry camping is limited to perhaps 3 - 4 occasions each season that have us camping for a few days without shore power, for reasons I described earlier, not because we want to but because we have to. However, high power discharge, albeit brief, is important because when we're without shore power I would like to use my 1000 watt inverter to power a toaster (620 watts measured) or coffee machine (560 watts measured) or my wife's hair dryer (350 watts measured, on low). One concern though is whether even dual G31s would offer sufficient capacity to remain above 60% SOC those times we also run a fan or two during really hot weather in lieu of A/C. With my current G27's SOC at 80% or higher the inverter will handle these appliance loads without protest but on one occasion I had forgotten to force the fridge to gas so when it's 300 watt electric element load was added to the toaster load the inverter's incoming voltage dropped below threshold and the alarm began to squeal. As you say - frustrating, particularly when the battery SOC was well above 80%. The microwave oven we don't care about but if replacing this G27 with a pair of G31s will allow me to power these appliances for a few minutes each once or twice a day along with a few hours of fan run time then that would seem to be the better choice for me than a pair of 6 volt GC-2s which according to your explanation won't handle high power discharge as well.
Thanks for the help - great info! :)