Extra Coach Battery

[bulldog82098]

Is their any reason to buy a second coach battery? What I mean is does the single 12 volt battery run down very quickly? What exactly does the coach battery run. I know it runs the lights but they are LED so I would imagine they use very little power.

[Fred g]

Anything in your coach that is 12 volt runs through the battery. That includes rv frig, water heater when on propane, furnace, jacks, slides, power awnings, steps, sometimes satellites, water pump, and lights. I am sure I forgot a couple of others. Most of the systems require at least 12 volts. A fully charged battery will read 12.7 volts and a battery that is 10.6 volts is considered dead. I like 2 batteries because when you first set up, it takes a while for the 110 charger to get the batteries fully charged. Depending on what you are running while going down the road, the alternator might not be putting much into the house batteries.

Fred

[Oneilkeys]

It depends on how you are going to use the coach. If you go into a KOA every night and plug in, then one battery might be OK. If you intend to stay in some state and most National Parks and a few Walmarts, then one battery is not sufficient. In cold weather, the furnace takes a lot of juice as does the fan on warm days. One battery limits your options.

[Chance]

I agree; being able to run furnace blower all night without shore power is a must for us. Many National Parks have sites without hookups and don't allow running the generator at night.

Doubling battery capacity usually more than doubles useable capacity, so a second house battery can be a good investment.

[JamieGeek]

Our old 5th wheel only had one 12V battery and it could easily run the furnace overnight.

Our experience with our Axis also suggests that it should be able to run the furnace overnight with a single coach battery as well. We almost tested this: On our way back from FL last year we had stopped about 6 hours from home to overnight at a truck stop. After having dinner I checked the weather reports: we would wake up to 6" or more of snow on the ground. We quickly packed up and finished the drive!

Our other trips where we've overnighted without plugging in were all in warm weather and had no need for the furnace.

All of this is highly temperature dependent though. If its really cold out (<0F) the furnace will end up continuously running...but then I'm not sure you'd want to be camping in that weather anyway.

[sikoriko]

If your wife is like mine add two more batteries and a solar panel. She loves to run that water pump and have every led light on. not to mention watching the TV with a satellite receiver on for about three hours on a inverter. By morning the batteries are reading 12.4V. Did I say she loves to run that water pump?

[Oneilkeys]

Originally Posted by sikoriko

If your wife is like mine add two more batteries and a solar panel. She loves to run that water pump and have every led light on. not to mention watching the TV with a satellite receiver on for about three hours on a inverter. By morning the batteries are reading 12.4V. Did I say she loves to run that water pump?

Absolutely. Jamie may be right in that you can get by with one, but an unhappy wife is not worth the extra $100. The other thing is, you have to understand batteries and battery life. You have approx 2 volts to work with. A fully charged 12v battery charges to about 12.8v. At approx 10.8 you are about out of power. However, batteries are like cats, they only have so many "lives". A battery looses a "life" when it discharges to below about 11.8v. Car regular battery can only do this about 10 times before it starts to die. A deep cycle Marine/RV battery is built to deep discharge and it can be discharged many, many more times before it starts to die. Last summer my wife and I lived in the Vegas about 150 days on our 15000 mile trip to Alaska. Well over 100 of those days were spent in National, state, county, regional or city parks without electric. They are not only cheap (average about $10 a night - we're over 62) but we think they are generally much nicer than private, parking lot camp grounds. Anyway, if we had only had one battery, we would have discharged it below 11.8v every night and it would have been dead before we got home and we would have had to purchase another. With two Walmart 29 RV batteries, we seldom took them down below 11.8v and they still charged up to 12.8v when we got home. In addition there were a half dozen days when, for one reason or another, we could not run our generator. With two batteries, I had the option to deep discharge them and still have power. With one I would have had no battery power the second day and a very unhappy wife.

[Chance]

Originally Posted by JamieGeek

Our old 5th wheel only had one 12V battery and it could easily run the furnace overnight.

Our experience with our Axis also suggests that it should be able to run the furnace overnight with a single coach battery as well. We almost tested this: On our way back from FL last year we had stopped about 6 hours from home to overnight at a truck stop. After having dinner I checked the weather reports: we would wake up to 6" or more of snow on the ground. We quickly packed up and finished the drive!

Our other trips where we've overnighted without plugging in were all in warm weather and had no need for the furnace.

All of this is highly temperature dependent though. If its really cold out (<0F) the furnace will end up continuously running...but then I'm not sure you'd want to be camping in that weather anyway.

Jamie, you should be able to get a rough estimate of your furnace run time.

I can't find detail information on Axis equipment, but the furnace is listed as a 30,000 BTU/hr. Not knowing the model I checked a few and they seem to draw around 7 Amps on average.

Axis house battery model or capacity is not listed either, but if rated around 75 Amp-hours, it would yield about 6 hours of furnace run time (assuming fully-charged battery) before the battery got down to a reasonable level of discharge that insures long life. Much beyond that battery life will drop off more quickly.

That 7 Amps for furnace blower is less than 100 watts of power, and if running a small TV (which can run as much power, and more if also running a DVD) for a couple of hours at night, you will be left with much less than 6 hours of furnace run time.

Like you stated, much depends on how cold it is outside and how warm you want to stay inside. Given the low cost of a second house battery, I personally think it's a great upgrade provided the motorhome is set up for it and the charger and or alternator can handle the extra load.

[Fred g]

When adding the extra battery, I would also add a battery watering system. To me, they are vital to keeping the battery fluid at the proper level and make the job so easy.

Fred

[Chance]

Originally Posted by Fred g

When adding the extra battery, I would also add a battery watering system. To me, they are vital to keeping the battery fluid at the proper level and make the job so easy.

Fred

Other than higher cost, what's your opinion on maintenance free? AGMs are becoming more popular, but not everyone thinks they are worth it.

[Oneilkeys]

I used AGMs in my sailboat because they they can be turned upside down without a problem and they take vibration very well. But they are very expensive and personally I don't think they are worth it for the hours most people put on batteries in their RV.

[Chance]

I'm still hoping that lithium batteries come down in price as experts predict. They are light, maintenance free, lasts many more cycles, and can be discharged down to 20%. Longer-term I'm hoping price drops enough to make elimination of generators an option.

[Fred g]

AGM's would be great but until I have to replace the originals, I would not consider it. Another option is 6v golf cart batteries. I had them for house batteries in our DP and they were exceptional.

Fred

[Oneilkeys]

Originally Posted by Fred g

AGM's would be great but until I have to replace the originals, I would not consider it. Another option is 6v golf cart batteries. I had them for house batteries in our DP and they were exceptional.

Fred

They are great, if you have the room for 4.

[Oneilkeys]

Originally Posted by Chance

I'm still hoping that lithium batteries come down in price as experts predict. They are light, maintenance free, lasts many more cycles, and can be discharged down to 20%. Longer-term I'm hoping price drops enough to make elimination of generators an option.

They are the future. With greatly improved solar panels you may be able to do without a generator. I never had a generator in my 36' sailboat because of the weight. I used solar and the engine alternator to charge the batteries.

[blw2]

for what it's worth, mine came with the typical marine type, only one of them. I'm not sure off hand the group.

Anyway, it has served us well enough..... on our 2 week trip last Christmastime, we parking lotted several times (cracker barrels, truck stops.... a couple times 2 & 3 nights in a row.
We ran the furnace some, but not all through the night., watched some tv, showered, lights, usual stuff....
A little generator running mixed in to make coffee, etc... but not really enough to top off the battery
But driving everyday was enough.

I'd guess it might be a stretch on the one cheap marine battery for multiple nights without driving or charging if using the furnace.... but it's fine for one night at a time... for us anyway....

If I were doing multiple nights off grid, I'd likely consider 1 good golf cart battery (or maybe 2x6 volts) + solar

Not AGM. Too expensive

[Fred g]

We have the added draw of a residential fridge. I love the residential over the RV type fridge but it does require more electric. We currently have 2 group 27 batteries and I will see how they hold out. If necessary, I will put 2 6volt golf cart batteries where they 27's are located under the step. I will then put 2 or 4 more 6volt in the closest compartment, making sure there is adequate ventilation. We will probably okay with the 27's as we are not boondocking like we used to.

Fred

[JamieGeek]

Originally Posted by Chance

I'm still hoping that lithium batteries come down in price as experts predict. They are light, maintenance free, lasts many more cycles, and can be discharged down to 20%. Longer-term I'm hoping price drops enough to make elimination of generators an option.

They already have:
Lithium-ion Battery Prices Expected to Plunge 60 Percent by 2020 | Data Center Knowledge

Electric-Car Battery Costs Already Cheaper Than 2020 Predictions: Study

Lithium-Ion Battery Costs To Keep Falling, Boosting Electric Car Sector −

[Chance]

Originally Posted by JamieGeek

They already have:
Lithium-ion Battery Prices Expected to Plunge 60 Percent by 2020 | Data Center Knowledge

Electric-Car Battery Costs Already Cheaper Than 2020 Predictions: Study

Lithium-Ion Battery Costs To Keep Falling, Boosting Electric Car Sector −

Thanks Jamie, that's indeed good news -- but 2020 is still 5 years away. For now the typical prices I can find for "retail" purchase is around $1,000 per kW-hr.

For my present needs I estimate that 5 kW-hrs of battery capacity (4 kW-hr usable at 80% discharge) would eliminate the need for a permanent generator. When the cost gets down to $500 per kW-hr at retail, I should be able to buy the lithium battery bank for the cost of a generator.

For many campers 5 kW-hrs of battery capacity wouldn't be enough to allow eliminating the generator, but for us it would be just enough. And if prices go as low as predicted by 2020, installing even 10 kW-hr may be cost effective by comparison to generator costs.


By the way, 4 kW-hrs of usable golf-cart batteries at 50% discharge would require 8 kW-hrs of installed capacity, which would be 8 normal-size batteries. If not for the weigh of around 500 pounds, it would be practical for us from a cost standpoint.

[JamieGeek]

I believe that the 23kWh battery in my EV weighs in at <800lbs for comparison.