6V Battery Setup Questions

[merryweather]

Hi all,

Is it possible / feasible / advantageous in any way to install two 6V deep cycle batteries in my 80 series in lieu of a second 12V battery? This would be essentially a dual battery system, but using two 6Vs wired in series instead of the 12V.

I'm primarily interested in maximizing the amp hours available for dry camping without a generator on hand, and when the rig may not be run enough between power usages to charge the battery back up to full.

If there is an easier way to go about what I'm trying to achieve I would definitely love to know. Thanks!

 

[The Jade Bean]

I have no idea about the 6V batteries, but I'm interested to hear what others say. However I'm not sure if you thought about this, but you could carry a solar panel to clip to the battery while camping to help keep the juice up (that's what we're going to do).

-Daniel Kent

 

[skidplate]

I would think a honda 2000 generator would take up about the same amount of room and probably weigh less than two batteries. You could use it for powering gadgits in camp plus charge your truck batts. Just my .02.

 

[george_tlc]

Hi all,

Is it possible / feasible / advantageous in any way to install two 6V deep cycle batteries in my 80 series in lieu of a second 12V battery? This would be essentially a dual battery system, but using two 6Vs wired in series instead of the 12V.

I'm primarily interested in maximizing the amp hours available for dry camping without a generator on hand, and when the rig may not be run enough between power usages to charge the battery back up to full.

If there is an easier way to go about what I'm trying to achieve I would definitely love to know. Thanks!

Not a good idea. What are you achieving?

Now you have two 6V batteries, if one fails you're dead in the water. You have created a situation with more cables, more clamps and no redundancy. Just doesn't make any sense.

It certainly is NOT a dual battery system since you only have one "12V" battery.

There's a reason folk that want dual batteries install 2 TWELVE volt batteries...

With a modern vehicle, there's a LOT of electronics that NEEDs power to be able to start and drive. If you want redundancy in case of a flat battery or outright battery failure, then install an isolated dual 12V battery system.

cheers,
george.

 

[merryweather]

I appreciate the replies. All I'm really trying to achieve is maximizing available amp hours. It seems like the top dollar deep cycle 12V batteries don't come close to the amp hours of some 6Vs. It sounds like the best choice would be a good deep cycle 12V isolated in a dual setup, and possibly look into a small generator.

Am I correct in thinking that a device that has a max draw of 3 amps DC running on a 125ah battery will run for 41.xx hours? I know those are theoretical numbers, not exactly what will occur in practicality, and I also know a deep cycle battery shouldn't be drawn below half charge, I just want to make sure my understanding is accurate.

 

[EOE_overland]

I appreciate the replies. All I'm really trying to achieve is maximizing available amp hours. It seems like the top dollar deep cycle 12V batteries don't come close to the amp hours of some 6Vs. It sounds like the best choice would be a good deep cycle 12V isolated in a dual setup, and possibly look into a small generator.

Am I correct in thinking that a device that has a max draw of 3 amps DC running on a 125ah battery will run for 41.xx hours? I know those are theoretical numbers, not exactly what will occur in practicality, and I also know a deep cycle battery shouldn't be drawn below half charge, I just want to make sure my understanding is accurate.

Sounds like a good idea but:
2X 12V 75aH batteries connected in parallel= 12V@ 150aH
2X 6V 75aH batteries connected in series= 12V@75aH.
So you gain nothing except the voltage increase for equal capacity battery systems. If you can get 2x 6V batteries that fit and are say, 200aH each, then technically you are ahead. But as mentioned above, one 6v battery will be useless in failure situation.

 

[george_tlc]

Furthermore to EOE, the energy density of a lead acid battery is based on the size of the cell. So, whether you fit two big 6V batteries in the two battery slots or one 12 battery in each one, if their total volume is the same, their capacity will essentially be the same.

12V 75A.hr battery gives you 12 x 75 = 900 W.hrs
6V 150A.hr battery gives you 6 x 150 = 900 W.hrs

2 of the 12V 75A.hr batteries gives you 2 x 12 x 75 = 1800 W.hrs
2 of the 6V 150A.hr batteries gives you 2 x 6 x 150 = 1800 W.hrs

BUT... with the 2 12V batteries, if one fails you can run start/run the vehicle with the other one. If one of your 6V batteries dies, you're stranded...

So, if you need a lot of W.hrs prior to vehicle starting and recharging, then a generator, solar, etc is needed.

cheers,
george.

 

[merryweather]

Sounds like a good idea but:
2X 12V 75aH batteries connected in parallel= 12V@ 150aH
2X 6V 75aH batteries connected in series= 12V@75aH.
So you gain nothing except the voltage increase for equal capacity battery systems. If you can get 2x 6V batteries that fit and are say, 200aH each, then technically you are ahead. But as mentioned above, one 6v battery will be useless in failure situation.

Typically 6V deep cycle batteries have far more aH than their 12V counterparts, that's the only reason I was thinking along those lines. Interstate sells a fairly common 6V deep cycle for RV usage that is rated at 232aH.

 

[EOE_overland]

Typically 6V deep cycle batteries have far more aH than their 12V counterparts, that's the only reason I was thinking along those lines. Interstate sells a fairly common 6V deep cycle for RV usage that is rated at 232aH.

Your line of thinking isn't wrong, but is just one facet of what is normal use for an expedition-type vehicle. You may be able to get more time running lights or pc with that setup, but as your only two batts they will also be the start batts, winch batts, etc which deep cycles arent usually designed for. And most often dual batt systems are for field redundancy.

If you had a start battery and two 6v batts for an isolated deep cycle bank, that would be better. But that will require more space than usually given in an engine bay.

Is the 232ah batt you mentioned sized to fit in the battery tray?
.

 

[merryweather]

Your line of thinking isn't wrong, but is just one facet of what is normal use for an expedition-type vehicle. You may be able to get more time running lights or pc with that setup, but as your only two batts they will also be the start batts, winch batts, etc which deep cycles arent usually designed for. And most often dual batt systems are for field redundancy.

If you had a start battery and two 6v batts for an isolated deep cycle bank, that would be better. But that will require more space than usually given in an engine bay.

Is the 232ah batt you mentioned sized to fit in the battery tray?
.

That's what I was originally thinking, have my normal 12V starting battery, and have the two 6Vs isolated for use with other needs (instead of another 12V isolated). This was for no other reason than to take advantage of the additional amp hours, but the increased complexity and chances for failure are good arguments against it.

All I really want to be able to do is power one or two DC devices for 6-8 hours a day for at least 5 days straight. It sounds like I need to investigate some other charging sources like solar or a small generator.

As for the size of the 6V, it's about half-size of normal car battery. Looks like a motorcycle battery. But I've seen 6Vs in a variety of shapes and sizes.

 

[george_tlc]

...
As for the size of the 6V, it's about half-size of normal car battery. Looks like a motorcycle battery. But I've seen 6Vs in a variety of shapes and sizes.

Again, if you are comparing lead acid batteries, the energy density is essentially constant.

So, if your 6V battery is 1/2 the size of a normal car battery, it will have HALF the watt.hours...

NOW, if you are comparing different chemistry batteries, then that's a different story (i.e. li-ion versus sla etc).

cheers,
george.

 

[EOE_overland]

That's what I was originally thinking, have my normal 12V starting battery, and have the two 6Vs isolated for use with other needs (instead of another 12V isolated). This was for no other reason than to take advantage of the additional amp hours, but the increased complexity and chances for failure are good arguments against it.

All I really want to be able to do is power one or two DC devices for 6-8 hours a day for at least 5 days straight. It sounds like I need to investigate some other charging sources like solar or a small generator.

As for the size of the 6V, it's about half-size of normal car battery. Looks like a motorcycle battery. But I've seen 6Vs in a variety of shapes and sizes.

Can you post a link of the specific 6v half size batts you're talking about? That will give something a little more concrete to compare.

 

[ironhippy]

I looked into this during the summer.

The 6 volt batteries he is referring to are real deep cycle batteries (not a starting/deep cycle battery, but an actual deep cycle battery, you will kill the batteries quickly if you try to crank off them). They are typically used in electric golf carts and stuff like that.

Here is the battery I was looking at: http://www.canadiantire.ca/AST/brow...lt+Deep+Cycle+Golf+Cart+Battery.jsp?locale=en

- Premium 6-Volt deep cycle battery
- 480 minute reserve capacity, 226 amp hour

The problem you will run into is charging the deep cycle battery. Your alternator will not charge it properly so do it properly you will have to have some type of DC to DC charger wired in.

In the end I just got the big Die Hard Platinum.

 

[merryweather]

The 6 volt batteries he is referring to are real deep cycle batteries (not a starting/deep cycle battery, but an actual deep cycle battery, you will kill the batteries quickly if you try to crank off them). They are typically used in electric golf carts and stuff like that.

That's correct.

The problem you will run into is charging the deep cycle battery. Your alternator will not charge it properly so do it properly you will have to have some type of DC to DC charger wired in.

That's what I was wondering. I think I'll just go with a good second battery system for winch, lights, and other accessories. I will probably look into an alternate power setup for use in base camp. Solar or generator sounds like a good viable solution.

 

[ironhippy]

That's what I was wondering. I think I'll just go with a good second battery system for winch, lights, and other accessories. I will probably look into an alternate power setup for use in base camp. Solar or generator sounds like a good viable solution.

yeah, the 6 volt (or any real deep cycle) solution is better suited to an RV, or trailer setup. You could do it in an SUV, but it's a lot of work when you're better of with a generator.

Another idea is you could build your own power packing using 6volt batteries, build in a charger and it would be a weekend's reserve of power. You could work out some type of inverter charging if you wanted to charge it while driving...
This is giving me ideas for my sleeping platform, it'd be nice to be able to run an electric heating pad overnight without worrying about the truck's batteries.

This forum on expedition portal has a lot of information on batteries and charging that is relevant to our uses http://www.expeditionportal.com/forum/forums/48-Power-Systems-12v-Solar-Gen

 

[merryweather]

Another idea is you could build your own power packing using 6volt batteries, build in a charger and it would be a weekend's reserve of power. You could work out some type of inverter charging if you wanted to charge it while driving...
This is giving me ideas for my sleeping platform, it'd be nice to be able to run an electric heating pad overnight without worrying about the truck's batteries.

This is basically what I'm trying to achieve. Except I also need to power my sleep apnea machine (3a DC) for long camping trips. A separate power setup from the truck's power is likely the way I'll go.

 

[EOE_overland]

Ok, thats why there was concern in a number of the comments as your OP sounded like you were going to use two 6ers instead of 2 12s. And that all of your batts were becoming true DCs.
You're idea could work, but if you spend a good amount of $ on high performance DCs it might be better to set it up a little differently?
As mentioned your 12v alt wont charge them properly. It will charge for sure, but probably shorten battery life. That may or may not matter much depending on how much you spend on it. I would suggest using two twelves; if you want to add extra capacity for sleep ap machine, etc above that it might be better to put them in a box in a trailer or in the cargo area?
You're looking to run ~3a for 6-8hrs a night for trips lasting a week? What else do you plan to run from this bank? Are you wheeling a bit during the trips? Or will your truck be sitting the whole time? Tossing two little 6v batts in the second tray could work fine. But depending on your answers might point toward a solution that is cheaper and/or less complicated.

 

[merryweather]

You're looking to run ~3a for 6-8hrs a night for trips lasting a week? What else do you plan to run from this bank? Are you wheeling a bit during the trips? Or will your truck be sitting the whole time? Tossing two little 6v batts in the second tray could work fine. But depending on your answers might point toward a solution that is cheaper and/or less complicated.

Most often I drive to a location and setup camp, and only drive sporadically after that. Maybe to explore a bit, or wheel a bit, but there's no guaranteed driving time.

 

[EOE_overland]

Hey, give it a shot depending on how much the batteries run. Post some pics and results if you do!