6v or 12v?

People are in favor of 6V for less cost for same capacity/durability. Disadvantage is that you need both batteries to power your system.

I have no reason to switch to 6V batteries currently since either system works for my purposes.

I'm using a pair of 12v AGM's because they were given to me. I've considered 6v when the time comes to replace the 12v. How would I go about charging a 6v batteries when one goes south on the road?

I have spent considerable time looking at batteries over the last year. We currently have a pair of t-105 6v batteries run in series to produce 12v. as well as a second bank with 2 12v trojan 100 amp hour batteries. These 4 batteries produce about 425 nom. amps but in reality they produce about 200 amps if you are willing to drain them down to 50% which we don't. We try and stay above 12.3 volts all the time which gives us about 120 Amp Hours of service. This has been ok since we don't use much now and have a 500 watt solar array to help keep them in the top 70%. Our new camper we are looking to run and use more stuff.

We are going to bite the bullet with Lithium Iron Phosphate LiFePo bank. The batteries can be almost fully discharged so a 200 Amp (2 28 pound batteries) hour bank would give us more power and battery wight would be 1/4 of the weight of what we have now. Weight is an important consideration in a TC.

The high battery cost, about 900 bucks for a 12v 100 battery is offset somewhat at time of purchase in that you need half the number of batteries and further off set in that they can typically go 3x the recharge cycles. In the long run the can definitely pay for themselves if you take care of them. LiFePo batteries also can accept higher charge rates which means you can charge them more quickly.

"Drop in" versions have a BMS (battery monitor system) so for the most part you just buy the battery and drop it in as a replacement and it will work fine. The BMS controls the charging limits to the battery to protect it although with a quality solar and shore charge controller you can refine the charging settings to maximize the battery. You also need a decent battery monitor. LiFePo batteries have a pretty flat discharge rate in volts so a voltmeter is a poor way to gauge. Victron or Bogart meter is a wise investment and are fully configurable to these batteries.

Anyway, my 2 cents. We have been happy with our 2 6v golf cart batteries and looking at your usage they should work just fine. Take them out every 3 months or so to check water lever and test with a hydrometer. That has served us very well for almost a year full timing.

Hi,

Batteries are designed around a 25 amp per cell discharge rate. When that is exceeded there may be excessive voltage drop. If the voltage falls enough, then the inverter may cut out, even though there is still lots of power to be had.

Example:

If you have a 220 amp-hour six volt jar in series with another, then you have a 220 amp-hour twelve volt battery with six cells. If a load of 50 amps is placed on it, then each cell must provide 50 amps. There may be lots of voltage drop.

If you have two 110 amp-hour twelve volt batteries wired in a balanced manner, then you have a 220 amp-hour capacity but with 12 cells. If a load of 50 amps is placed on it, then each cell only needs to provide 25 amps. There will be less voltage drop than in the six volt twins.

I often do 70 amps loads, so having 4 12 volt jars means the load per cell is 70/4 =17.5 amps per cell.

My microwave draws 156 amps. With 4 six volt jars each cell must do 78 amps, but with 4 twelve volt batteries it is 39 amps.

I hope this helps.

Freep wrote:

pianotuna wrote:
It depends.

My own preference is 12 volt. I do that because I run a medium size 3000 watt inverter.

This is interesting. How does the inverter figure into this? At some point I'd like to add an inverter too. The hope is to one day be able to run the MW for a few minutes without running the gen.

time2roll wrote:
Alright!

Honestly I would try to just not use the 12v fridge option. Use propane on the road like 99 percent of RVs do.

12v vs 6v points are moot once you move to AGM. I recommend Lifeline deep cycle in the shape that fits the most amp/hrs in the space. No difference in construction, very low fail rate.

Next would be to review your charging system to minimize generator run time. Solar is great however if running the generator you want 60+ amps at 14.4 volts into the Lifeline. Flooded you want 14.8 volts again at 60+ amps. Other AGM is good too but check the charging specs.

PD9280C - 14.4 volts

PD 9280C - 14.8 volts

After the trouble and expense I went through to get the right gauge harness installed, I'm using the DC fridge while driving. :) I just have to remember to make sure I'm back on LP when I stop.

I had already settled on the lifelines and found several candidates that will squeeze the most battery into the space.

I'm glad you mentioned the converter chargers. This is one area where I am ignorant. I don't how the battery is charged now when the gen is running or when I'm plugged in. I do remember seeing some device in the basement wired between the gen and something. I'll have to check that out.

Alright!

Honestly I would try to just not use the 12v fridge option. Use propane on the road like 99 percent of RVs do.

12v vs 6v points are mute once you move to AGM. I recommend Lifeline deep cycle in the shape that fits the most amp/hrs in the space. No difference in construction, very low fail rate.

Next would be to review your charging system to minimize generator run time. Solar is great however if running the generator you want 60+ amps at 14.4 volts into the Lifeline. Flooded you want 14.8 volts again at 60+ amps. Other AGM is good too but check the charging specs.

PD9280C - 14.4 volts

PD 9280C - 14.8 volts

time2roll wrote:
Read through them all? How about post your concerns related to your camping style.
Space concerns, how will you charge them... throw us a bone for what you need.

Otherwise you have read all the general answers.... go down and buy something. Unless you are going lithium not much has changed in 25+ years.

No, I did not read them all but I read a lot of them over the last few months.

OK, Here's some details. We mostly boondock and generally stay for one or two days in each location. I hate using the Onan generator because it is incredibly loud. I recently added the lance 8 gauge harness to the truck so the camper batteries will charge and I can run the fridge on DC when driving. This works very well. We also have a 90 W solar panel. I will probably add a 200 W panel and an MPPT charge controller after upgrading the batteries.

On our last trip during the eclipse, our batteries drained considerably most nights. One reason was the fridge not flipping to LP after camp was set up and me not noticing it for about an hour(twice!). But we also use our computers quite a bit and listen to the radio. We don't watch TV much, no satellite. We like to camp in the colder months and need the heater to run during the night. The batteries are AC Delco G24 FLA batteries, 12 V.

My wife routinely takes the camper out on her own and I don't want her losing power in the fall and winter, so I'm looking at AGMs, even though I really want to go Lithium.

Let me know if you want any more details.

You cant compare a 12 v gp dual purpose battery to a gc2. As covered in the last go around compare a Trojan SCS225 to two T105

2oldman wrote:
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Are you saying you also smelled a dead horse. :)

Freep wrote:

pianotuna wrote:
It depends.

My own preference is 12 volt. I do that because I run a medium size 3000 watt inverter.

This is interesting. How does the inverter figure into this? At some point I'd like to add an inverter too. The hope is to one day be able to run the MW for a few minutes without running the gen.

Some physics thing. The 12v carry a heavy load with less drop. I forget the name of the effect.

Now this means a true 12v deep cycle, not a starting battery rated by CCA.