12 Volt to Twin 6 Volt Conversion

[AirMiles]

From the giant number of "battery" threads here, it's very obvious that there is a wide range of user experience in terms of battery life. The stuff above is a lot of what drives this range of experience. Without everything being same / same it's very tough to compare one experience to the other.

Very good post, especially the last comment. I do not baby my batteries. My plan is to use them just as I do my 20# propane exchange tanks - use and abuse them until they run out of juice and then replace them. I really don't care if I draw them down 50% or 80%. My analysis shows that batteries are good for a certain amount of amp hours in their lifetime. A few more amp hours if you baby them and a few less if you abuse them. But not enough difference between babying and abusing for me to worry about.

Here is the analysis:
See the "Typical Cycle Life" chart at this link:
https://www.altestore.com/store/deep...battery-p9843/
This chart shows if I baby my batteries and only draw down 20% before recharging, I will get 2,500 cycles. My batteries have 230AH. At 2,500 cycles at 46AH equals 115,000AH during their life. At 50% draw down, you get 1,000 cycles at 115AH equals 115,000AH. At 80% draw down, you get 500 cycles at 184AH or 92,000AH. I'm ok with getting as low as 92,000AH out of a pair of batteries costing $200, or .002 cents per amp hour. That's means my batteries cost 40 cents per cycle (day of use). By babying my batteries, I may save 10 cents per day of use. I've got bigger things to worry about than that!

[uncle_bob]

Hi

As long as you don't totally freak out when you have to replace batteries, the "use them and replace them" works very well. Ultimately they *are* a consumable, just like brake pads. If you are going to agonize about "why did my (abused / cheap) batteries only last X years?" then don't go with that approach.

Of to my new thread - don't ever use your brakes, it will wear them out ...

Bob

[ROBERT CROSS]

More info on babying batteries, how does one go about it?
Empty minds want to know.
Would staying on shore power help?

Bob
🇺🇸

[uncle_bob]

Originally Posted by ROBERT CROSS

More info on babying batteries, how does one go about it?
Empty minds want to know.
Would staying on shore power help?

Bob
🇺🇸

Hi

One (of many) factors in wearing out a battery is how deep and how often you discharge it. To "treat it nice" (in that respect) just never use it .... indeed, shore power forever and the battery is always on float. There are some people who really don't use batteries a lot. That's more by their campsite choices than by any intention of helping the battery out.

Yes, cycles are also done with parasitic loads. If the same "always camp with shore power" folks then store for weeks on end with no power and loads connected ... the battery gets a cycle to zero *and* sits dead for a while. The do still have to have some sense about batteries.

Bob

[Al and Missy]

I don't know how any converter/charger can claim to match the ideal charging profile for a battery which is in use given the loads that are usually attached to the battery. The generic ideal profile is to charge at a constant current which is some percentage of the Ah capacity, say 25%, until the voltage reaches a threshold. This is the bulk charge phase. So for a 100Ah battery bank, the constant current would be 25A. What happens, for example, when the furnace turns on? The current available for the battery drops to 18 amps. This is probably not detrimental to the battery, but will extend the charging time. The next phase, absorption, will put out a constant voltage until the current drops to a threshold level, usually quite low. With the normal loads of a trailer, the current may never drop to this level and the charger will never enter the third phase, float, where the voltage is reduced to avoid overcharging.

Converter/chargers are, of necessity, a compromise. The various smart designs attempt to optimize this compromise, but probably can't match the ideal profile for a specific battery.


All of the above, IMHO, YMMV, etc.



Al

[hshovic]

I agree. My 6v agm’s lasted 70,000 miles and finally gave up. Had to replace them. As Lighfoot writes “Stories always end”.

[AirMiles]

My definition of "babying" a lead acid battery bank would be to limit draw downs to 50% of bank amp hours. Using 115AH from a 230AH bank.

My definition of "not-babying" a lead acid battery bank would be to limit draw downs to 80% of bank amp hours. Using 184AH from a 230AH bank.

My battery plan is to "not-baby" my battery bank and to replace the batteries when necessary. My "not-babying" plan saves 50% of the cost of the battery bank up front for a cost of 20% less amp hours over the battery bank's lifetime. In other words, "not-babying" a battery bank is more cost effective than "babying" a battery bank. At a cost of around $200 for my 230AH battery bank, I'm willing to test my "not-babying" plan.

[gypsydad]

Originally Posted by Al and Missy

I don't know how any converter/charger can claim to match the ideal charging profile for a battery which is in use given the loads that are usually attached to the battery. The generic ideal profile is to charge at a constant current which is some percentage of the Ah capacity, say 25%, until the voltage reaches a threshold. This is the bulk charge phase. So for a 100Ah battery bank, the constant current would be 25A. What happens, for example, when the furnace turns on? The current available for the battery drops to 18 amps. This is probably not detrimental to the battery, but will extend the charging time. The next phase, absorption, will put out a constant voltage until the current drops to a threshold level, usually quite low. With the normal loads of a trailer, the current may never drop to this level and the charger will never enter the third phase, float, where the voltage is reduced to avoid overcharging.

Converter/chargers are, of necessity, a compromise. The various smart designs attempt to optimize this compromise, but probably can't match the ideal profile for a specific battery.


All of the above, IMHO, YMMV, etc.



Al

Not an expert here either, but the term "probably" may not be appropriate either, when "assuming" how the newer manufacturers of the new 4 stage converter/chargers have built in to their units. Perhaps an expert in this area can enlighten us more...the write ups from Progressive Dynamics and also Boondocker seem to cover all my concerns, but maybe I am missing something here? This one from Progressive Dynamics is a good read if you have not seen it yet.

https://www.progressivedyn.com/servi...anagement-101/

[Al and Missy]

I'm not trying to take away from the PD and Boondocker converters. I put a PD in my 25 and am about to pull the trigger on something for my 30. They are certainly better than the fixed voltage chargers that were prevalent for a while. My 25 had one and my 30 still does.

I hadn't seen that writeup, but it does not fully account for the trailer situation. If it did, there would be a water pipe going off to the right feeding a handful of faucets that are turned on and off at random times and flow rates.

As an engineer, I don't know how well a converter can determine which electrons are going to the battery and which are going to trailer loads. I can think of a few methods to approximate the split, but they would be an approximation. I have actually designed a converter charger that can, but it would cost a lot more than the current set of devices. I may build a prototype and try it out on my trailer.


Al

[68 Overlander]

Originally Posted by Al and Missy

As an engineer, I don't know how well a converter can determine which electrons are going to the battery and which are going to trailer loads. I can think of a few methods to approximate the split, but they would be an approximation.
Al

This is exactly correct Al, they can't determine the difference and that is no secret. What they can do however is sample the voltage and choose the "best" mode to be in, bulk, absorption or float. Voltage and timers are used as you know.
That said, for most 24-30 foot campers almost always get a converter in the 55-60 amp range. Rarely will you see 55-60 amps delivered to the batteries even with nothing else on since the resistance builds so fast. The Boondocker 1260 will output actually 64 amps if only converting with no resistance but the instant you connect it to a battery, it begins to taper (internal resistance) unless the battery bank is large and significantly discharged. Same with PD and Iota and the others.
We've had PD modify several product for us based on customer request and they are almost as popular as the regular units. One is the 14.8 VDC Boost 9200s instead of 14.4. Many want faster charging and as you know, volts pushes the current. Trojan customers especially love them because they actually recommend the higher voltage.
Other is the 4655 MBA for the WFCO 8955 PEC.

On the Boondocker deck mount units, they are now adjustable on all models ending in CL or PC. Soon they will all be. They also have the ability to equalize or operate in a constant current/constant fixed voltage for LiFePO4

[vintage65]

Thanks everyone for all your valuable input! Darren

[Grateful26]

Originally Posted by kscherzi

Twin 6 volt Trojan T 105's here. Maintenance consists of checking distilled water levels annually. Much cheaper than AGM's. Unlike expensive lithiums, no costly change to Airstream onboard control panels etc., simple plug and play.

This post caught my attention. I am a new owner, learning each day fro y’all.
I was thinking of getting a lithium ion.
Are you saying that I can’t simply replace my existing battery with a lithium?
Thanks.

[68 Overlander]

Originally Posted by Grateful26

This post caught my attention. I am a new owner, learning each day fro y’all.
I was thinking of getting a lithium ion.
Are you saying that I can’t simply replace my existing battery with a lithium?
Thanks.

You can but your existing converter will not charge it completely. Most LiFoPO4 batteries need a constant current/constant voltage power supply at ~14.6 VDC

[uncle_bob]

Originally Posted by Grateful26

This post caught my attention. I am a new owner, learning each day fro y’all.
I was thinking of getting a lithium ion.
Are you saying that I can’t simply replace my existing battery with a lithium?
Thanks.

Hi

You can and with the "right" lithium batteries it will work..... sort of.

If you are doing the "normal" sort of upgrade, you are spending >= $2,000 to improve your battery situation. A simple converter that better matches the needs of a lithium setup is around $200 or so bought from somebody with a phone number. Maybe not quite round off error, but close. Yes you could save a bit buying on Amazon but then you have zero support - that is *not* a good way to go.

Running a "stock" converter can let your lithiums run down to about 70% capacity before they charge back up. Yes, it works. Yes, they do eventually charge back up. Most of us want our batteries to be well over 95% charged when we're just sitting there on shore power.

There are a number of variables in all this. Do you have solar? Do you connect / disconnect from shore power often? Which converter / charger do you have? Exactly what voltages is your particular sample set to? ( a tenth of a volt is a really big deal in this case). Net result is that you really can only guess what the outcome will be without digging into a lot more details.

Bob

[Grateful26]

Originally Posted by uncle_bob

Hi

You can and with the "right" lithium batteries it will work..... sort of.

If you are doing the "normal" sort of upgrade, you are spending >= $2,000 to improve your battery situation. A simple converter that better matches the needs of a lithium setup is around $200 or so bought from somebody with a phone number. Maybe not quite round off error, but close. Yes you could save a bit buying on Amazon but then you have zero support - that is *not* a good way to go.

Running a "stock" converter can let your lithiums run down to about 70% capacity before they charge back up. Yes, it works. Yes, they do eventually charge back up. Most of us want our batteries to be well over 95% charged when we're just sitting there on shore power.

There are a number of variables in all this. Do you have solar? Do you connect / disconnect from shore power often? Which converter / charger do you have? Exactly what voltages is your particular sample set to? ( a tenth of a volt is a really big deal in this case). Net result is that you really can only guess what the outcome will be without digging into a lot more details.

Bob

Bob (and all) thanks for this. Learning a ton. We’re new owners after tent camping for 41 years. Newly retired and just returned from a monthlong 4,000 mile trip. Headed to Arizona for six weeks in January and I’d like to have this at least partially nailed down. I’ll be getting a portable 100w solar and would like to double the battery capacity.
On a related note, the tiny plastic battery box on the Bambi is very disappointing so I’ll have to build a new one.

Marcos

[uncle_bob]

Originally Posted by Grateful26

Bob (and all) thanks for this. Learning a ton. We’re new owners after tent camping for 41 years. Newly retired and just returned from a monthlong 4,000 mile trip. Headed to Arizona for six weeks in January and I’d like to have this at least partially nailed down. I’ll be getting a portable 100w solar and would like to double the battery capacity.
On a related note, the tiny plastic battery box on the Bambi is very disappointing so I’ll have to build a new one.

Marcos

Hi

There are a number of threads around here detailing how various people have redone their solar and battery systems. Some of us get pretty crazy when doing it so not everything applies to a minimum upgrade path. Check them to get lots of ideas.

Quick and simple way to go:

Check the battery box size against something like the BB lithiums. ( = make sure they will fit or build a new box).

Buy as many BB's as will fit on the credit card and in the space available

Drop them into the existing wiring

Replace the converter / charger with a "lithium" version. You can spend anywhere from $200 up into the thousands (hybrid inverter / charger) on this part. Strongly suggested - do buy from somebody with a support phone number and not an anonymous account on Amazon ....

That's the basic minimum recommended / least likely to be a problem approach.

A very common upgrade to that system is a Victron BMV-712 to keep track of battery state. It's not mandatory, I'd say that > 90% of the people who have posted on the forum with details have put one in on their lithium setups. It makes it *much* easier to tell what's going on.

=====

Arizona in January .... hmmm .... which part of Arizona? Once you get below 24F, lithium's are not as much fun. They can't be charged and their discharge is a bit limited as well. Yes, this gets into batteries indoors vs outdoors and a few other things ....(You can put a temperature probe on a 712 to tell you what the batteries are seeing ...).

Bob

[Grateful26]

Originally Posted by uncle_bob

Arizona in January .... hmmm .... which part of Arizona? Once you get below 24F, lithium's are not as much fun. They can't be charged and their discharge is a bit limited as well. Yes, this gets into batteries indoors vs outdoors and a few other things ....(You can put a temperature probe on a 712 to tell you what the batteries are seeing ...).

Bob

We’ll be in the Tucson area. Traveling from Austin so we’re staying south.

I *think* I have decided which direction to head in terms of my setup for now.
But if I’m being stupid, call me out. This battery stuff is fun and super interesting but damn do I have a lot to learn.
I’m going to go with two 6v from Sam’s at $89 per and build a new box.
Someone mentioned that this is a “plug and play” situation so that fits my needs, budget and limited knowledge at this time. I will order a Renogy 100a portable suitcase model, which comes with the controller and it looks like I have to buy an adaptor for the Zamp connection. Since we’ll be in AZ, I am counting on sun. At any rate I should have more capacity.
I’ll have to wait for more options, unless I can find a less expensive battery monitor that fits the bill.

My second, cheaper option is to buy. Second 12v.

Thanks again.
M

[Fair_Enough]

M, your not being stupid. I’ve not seen even from Sam’s an $89!deep cycle 6 volt. The thing about portables is they don’t charge in the carrying case, which means you could arrive with low batteries. 100 W also isn’t much if the demand is average. Not sure where the Zamp plug is or how appropriate it is, but I think most simply clip the renogy cord directly to the batteries. Second 12 volt what?
Clint

[AirMiles]

Originally Posted by Grateful26

We’ll be in the Tucson area. Traveling from Austin so we’re staying south.

I *think* I have decided which direction to head in terms of my setup for now.
But if I’m being stupid, call me out. This battery stuff is fun and super interesting but damn do I have a lot to learn.
I’m going to go with two 6v from Sam’s at $89 per and build a new box.
Someone mentioned that this is a “plug and play” situation so that fits my needs, budget and limited knowledge at this time. I will order a Renogy 100a portable suitcase model, which comes with the controller and it looks like I have to buy an adaptor for the Zamp connection. Since we’ll be in AZ, I am counting on sun. At any rate I should have more capacity.
I’ll have to wait for more options, unless I can find a less expensive battery monitor that fits the bill.

My second, cheaper option is to buy. Second 12v.

Thanks again.
M

I use a pair of Sam's Club 6V golf cart batteries with 230AH. I purchased the slightly more expensive EGC2 model over the lower cost GC2 model based this article's recommendation https://marinehowto.com/what-is-a-deep-cycle-battery/ Sam's Club occasionally runs a $20 off any battery sale if you can catch it. Golf cart batteries are tough and can take great abuse. Just keep the water levels topped off.

I think your start small and learn plan is a great idea. 100W of solar kept pointed at the Arizona sun can produce as much as 200W fixed to the roof. Your small system is a great way to learn about solar which will help you determine how big of system you may want in the future.

I really like my 400W of roof mounted panels because they charge as I drive down the highway and when I am parked. I get fully charged batteries 97% of the time with my 400W of Solar. The 3% of the time when I need to charge with a generator is due to "dark" rainy days or complete tree canopy where even 1000W of solar would not be enough. What is needed on these "dark" days is more Amp Hours of battery (or a generator). These are the type of things you will learn while using your small system.

Have fun learning about solar with your new small system and keep us posted on how it works for you.

[Adventure.AS]

Originally Posted by AirMiles

...
I really like my 400W of roof mounted panels because they charge as I drive down the highway ...

My batteries charge fully from my TV when travelling. I don’t think solar would add any more charge, except on short travel days.

The 3% of the time when I need to charge with a generator is due to "dark" rainy days or complete tree canopy where even 1000W of solar would not be enough. What is needed on these "dark" days is more Amp Hours of battery (or a generator).

You can add a lot more amps by running your TV and using good jumper cables to your house batteries. My alternator can put out 160 amps. My goal is to get the batteries to 80% charge quickly (as the other 20% would require too much run time. ) YMMV