6 volt vs 12 volt batteries for boondocking

[placergold]

Hi all, While waiting for our new 28' Stealth toy hauler we're trying to figure out the best batteries to get for when we're back in the hills camped off the grid.

We ordered the optional 200 watt solar panel & regulator with Power Boost. And a 1,500 watt Go Power Inverter.

I've been told the golf cart type 6 volt batteries will last much longer than the 12 volt deep cycle batteries available. Mainly because of the constant discharge/charge cycle that occurs.

But, I really have no experience in this area, so any and all input from those familiar with this subject would be greatly appreciated!

Thank you.

[Timmo_]

You can spend big bucks for the perfect battery, or select 2nd best for a fraction of the cost. I got my CG2's at Sam's Club many years ago.

[time2roll]

OldSmokey wrote:

First off you are wrong...fact...battery is made by East Penn, not interstate.

interesting.. my contact at interstate said they supplied duracell brand.. hmmm.. i need to make another call..

Interstate is just a distributor. They do not make batteries.

Yes the may supply the Duracell but not manufacture.

[marcsbigfoot20b]

http://www.driveduracell.com/assets/duracell/image/1686.pdf

At the bottom of the page.

Edit

The 31AGM also branded as Deka Intimidator
http://www.eastpennmanufacturing.com/wp-content/uploads/Marine-Master-Spec-Sheet-0194.pdf

[MEXICOWANDERER]

interesting.. my contact at interstate said they supplied duracell brand.. hmmm.. i need to make another call..

Yes indeedee you do. A battery rebrander claiming they supply another rebrander is curious. Like looking for a used car dealership.

[MEXICOWANDERER]

Interstate is a battery rebrander

The only thing they "manufacture" is hot air.

LTH in Monterrey is starting to manufacture conventional AGM batteries.

[OldSmokey]

MrWizard wrote:
I might be wrong
but i am of the opinion that the more Conservative the AmpHr rating per pound of lead, aka more lead per AmpHr

the higher the quality of battery

usually one of two cases, thick plates for longevity and cycles
or surface area for low internal resistance and high discharge rates.
hybrids such as marine sit in the middle. all variations to suit different markets.

high quality comes at a price and that usually implies more lead.


your telco batteries are AGM with Lead Calcium plates
like a car battery.. designed for large currents ( 1C ) and low cycles as they usually sit in float service for most of their life, typically
10 to 15 years.

other AGM are made for high current and moderate cycles, but you pay the price in longevity. also high $$$$

deep cycle like Trojan have really thick plates of lead antimony alloy for lifespan and high cycles, but higher internal resistance and lower current.

so your choice of battery depends on intended use of course.



I see at least three camps in RV ( pun not intended ! )

1. boon dockers who want every modern appliance.. so high current draw and low cycles. this is the AGM

2. boon dockers who minimize and require only lighting and a few low current draws.. therefore low current and high cycles. this is the Trojan RE

3. those who camp with hookups and don't care less.. use a marine or car battery.

4. those who need high capacity and high cycles.. this is the world
of Lithium. problem here is cost.. how many would spend say $4000 for
a battery ? not many..

now, these are just typical use. you can get high draw and high cycles but at a price and weight. Main limitation with RV is space and weight.

[MrWizard]

I might be wrong
but i am of the opinion that the more Conservative the AmpHr rating per pound of lead, aka more lead per AmpHr

the higher the quality of battery

my Surplus Telco server batteries 105# 135Ah each
thats 1.28 Ah per pound of lead
since the batteries are 33% heavier than a group 31, but also taller
i don't know if the plates are just taller, or also Thicker while being taller
i suspect thicker, because i'm not sure they are 33% taller
i never thought about it until now

as it has been stated many times
plate thickness is design of function
super high amps for a short time, aka spin the starter on a cold engine
or moderate amps for a along time for a dedicated load

For MOdern RV'ers , there is NO constant for comparison
no set number of hours of 40w tv, no set number pump run minutes
lots of intermittent high amp inverter use

[OldSmokey]

Yeah no biggie. Just that some of us know what we are doing for our own particular situation. It's hard to figure all that out on the Internet forums from the information that is provided, lol.
And of course for every setup there is one better setup, just $$$$$

quite right.. sometimes it's difficult to assess things without all the relevant information.

I just finished up a call re: interstate

It was clarified that duracell has had multiple suppliers over the years. including : Johnson controls, interstate and east penn.

[marcsbigfoot20b]

OldSmokey wrote:

First off you are wrong...fact...battery is made by East Penn, not interstate.

interesting.. my contact at interstate said they supplied duracell brand.. hmmm.. i need to make another call..

Second, how do you know how much solar is enough? Are you ASSuming I am going down to 50% SOC EVERY DAY? I am not.

only you know that as you didn't post your daily w/hr.

if you would care to post your daily w/hr then I would gladly discuss and assist you with panel/battery best practices.

i made a rough back calc based on battery capacity, no need to get belligerent about it..

I have been an ASE master tech since 91 and a field service engineer in the semiconductor industry for the last 22 years.
I didn't just guess when I added these components.

I'm sure you did, however paralleling always raises a red flag in the professional world, unless there is no better solution, paralleling is the last choice. I have 40 yrs as MSEE and 20 as PE.. as you will appreciate, our design criteria will be quite different.

Yeah no biggie. Just that some of us know what we are doing for our own particular situation. It's hard to figure all that out on the Internet forums from the information that is provided, lol.
And of course for every setup there is one better setup, just $$$$$

[wa8yxm]

I will say this again. GC batteries. be they GC-2 or GC-12 are DEEP CYCLE, you can also get other DEEP CYCLE batteries but they can be hard to find and expensive.

Most of your Group 24, 27, 29, 31 batteries are MARINE/deep cycle. (pay attntion to the case I use)

Starting batteries need to be kept well fed like 80+% at all times. Run 'em down and they are TOAST'
MARINE batteries are starting as well Just not rated for sub freezing temps. but MARINE/Deep cycle.. Well they are Mostly starting with lip service paid to DEEP CYCLE you can run em down safely just a few percent less than MARINE.

DEEP CYCLE are designed for 50% discharge.. Provided you recharge soon.

And due to fact that Golf Courses order GC batteries by the pallet load.. As opposed to ordering in smaller quantities as Auto Stores do the Group this or that types. GC batteries are LOWER COST. as well.

[OldSmokey]

First off you are wrong...fact...battery is made by East Penn, not interstate.

interesting.. my contact at interstate said they supplied duracell brand.. hmmm.. i need to make another call..

Second, how do you know how much solar is enough? Are you ASSuming I am going down to 50% SOC EVERY DAY? I am not.

only you know that as you didn't post your daily w/hr.

if you would care to post your daily w/hr then I would gladly discuss and assist you with panel/battery best practices.

i made a rough back calc based on battery capacity, no need to get belligerent about it..

I have been an ASE master tech since 91 and a field service engineer in the semiconductor industry for the last 22 years.
I didn't just guess when I added these components.

I'm sure you did, however paralleling always raises a red flag in the professional world, unless there is no better solution, paralleling is the last choice. I have 40 yrs as MSEE with 20 of those yrs as PE.. as you will appreciate, our design criteria will be quite different.

[OldSmokey]

for this example your batteries numbered 1,2 and 3 are connected in parallel string with the take off on battery 1 to your equipment.

If you think that's how it's done, you're doing it wrong


I KNOW that's the incorrect way, I was highlighting that method for the OP's education.

you now discharge at 90 Amps. you would think that each battery will supply 30 amps right ?.. well your wrong,

Wrong only if the wiring is wrong.

you will be surprised to learn that even if they are connected as you post, the batteries will still be imbalanced ( to a lesser degree ) due to the internal resistance and capacity.

[marcsbigfoot20b]

OldSmokey wrote:

marcsbigfoot20b27 wrote:

OldSmokey wrote:

All 3 of my batteries were bought in the same month....just adding them to the trailer permanently with some 1/0 cable.

not going to make much difference, 2-3 years max and you will be replacing them anyway..

Oldsmokey, still waiting to hear your reason why my brand new AGM batteries will only last 2-3 years?????

sorry for the delayed reply, I have been overseas finishing up a contract.

now back to your issue, i'll try to keep it in laymans terms.


your Duracell agm is a budget agm made by interstate, it's a 'b' grade and not
made to the best standard. battery to battery variance in internal resistance and
capacity is the issue here, when you connect them in parallel the set will behave
( performance wise ) as the worst battery. so in effect you had 2 good batteries
and one not so good and made them into three not so good batteries.

now the situation becomes worse when you actually use them and start to charge and discharge

over time.

for this example your batteries numbered 1,2 and 3 are connected in parallel string
with the take off on battery 1 to your equipment.

you now discharge at 90 Amps. you would think that each battery will supply
30 amps right ?.. well your wrong,

in practise, more current will be drawn from batt 1 than batt2 and batt 3
this is due to cable and internal resistance.
i won't bore you with complex network analysys, but the current distribution
from a 3p string is approx like:

batt 1, 41 A
batt 2, 28 A
batt 3, 21 A

so you have batt 1 doing much more work than batt 2 and batt 3
this also happens when charging, batt 1 will charge first with the others lagging
behind. now, after many cycles of this abuse, batt 1 will age much more rapidly than
batt 3. as batt 1 ages, it has the effect of dragging the others with it as they
attempt to equalize each others voltages. batt 1 drags batt 2 and 3 and batt 2 drags 3


now for fun, just imagine what happens if one battery cell develops a short ??

you guessed it.. the others dump their charge into it at a very high rate
and you get your very own firework show..

now there is a 'trick' that will mitgate some of this and it's simple..
you connect all 3 in parallel and draw positive from one end of the string
and neg from the other.. now you only have one batt underworked..
it's still not good but will give the string a better chance..


you stated you have 360 W of panels..
I can tell you right now that's not enough.. 300Ah of agm will need
at least c/10 to charge. a good mppt cc will be 90% so 360 * 0.9 = 324 W
and 324 W at 12V = 27 Amps.. so you are short even at max insolation.
you need a minimum of c/10 or better still, for agm c/6 = 50 Amps
so you need more like 720 W or so.. and that's probably wrong because we don't know
your actual usage.

and fwiw, that WFCO convertor is not woth the space it occupies and will not
charge your agm's correctly either.

if anyone needs more info on solar/RE i would be more than willing to assist.

First off you are wrong...fact...battery is made by East Penn, not interstate.
Second, how do you know how much solar is enough? Are you ASSuming I am going down to 50% SOC EVERY DAY? I am not.
I have been an ASE master tech since 91 and a field service engineer in the semiconductor industry for the last 22 years. I didn't just guess when I added these components.
You can see it here. https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/29379975.cfm

[mike-s]

OldSmokey wrote:
for this example your batteries numbered 1,2 and 3 are connected in parallel string with the take off on battery 1 to your equipment.

If you think that's how it's done, you're doing it wrong.

Wrong (both external connections to the same battery. Consider the pairs to be single batteries, this is just the clearest drawing easily found):


Right (external connections at opposite ends, so there's an identical voltage drop to each battery):

you now discharge at 90 Amps. you would think that each battery will supply 30 amps right ?.. well your wrong,

Wrong only if the wiring is wrong.