Inverters, two batteries and furnace burn time

[rich]

Hello Everyone,

We are back from a two week road trip which was really the shake down trip for our camper. I am running one 24 series deep cycle battery with the poor mans auxiliary charging system, just a 4 post solenoid drawing power from the windshield wiper motor so it only charges when the key is on. For a little extra safety when off the beaten path I put two quick disconnects in the system as a poor mans battery isolator. In established campgrounds I don't worry about it but for a little extra piece of mind in the back country I pop the hood and disconnect those two spots which means even if the solenoid fails the camper can't draw the truck battery down. The system worked great, even when stopped for 4 days with minimal heater usage the lights didn't even dim. However, one night in Death Valley we decided to set the thermostat and leave the heater on and able to cycle overnight. We woke up to a dead battery. My in laws were near by with a battery charger and generator so we just drove to them and charged back up. It was a good test. Also we found ourselves wanting to charge the laptop in places without shore power so I got thinking about an inverter. This left me with a few questions that you all may be able to help me with.

1. For those of you running two batteries and perhaps larger batteries are you able to set the furnace thermostat and leave it on overnight or is that always too much draw?

2. For those running hard wired inverters how many watts are you running and do you need to have two batteries to keep the lap top and phone charge draw from killing your battery?

3. I want to install a meter that gives me real time info about my battery charge. I know FWC and ATC install them in their new campers but has anyone found an aftermarket one that they really like?

Thanks for the help guys!

Rich

 

[craig333]

I have three batteries, two in the truck, one in the camper. I normally leave them paralled just because I'm lazy. I always leave the heater on all night (if its at all chilly) and have never had any issues. The inverter with my laptop plugged in and on all day while I was out wheeling in moab did drop my batteries into the yellow zone.

I should mention I can Isolate the camper battery if I feel the need to with a switch.

 

[Ted]

We run two 12 volt AGM batteries in the camper. We always leave the heater on all night. A recent trip to Tahoe got down to 18 degrees overnight. Heater was set at 45 and ran a lot. No problems. That said, we had driven about three hours to get to camp, so the batteries were fully charged. I would be hesitant to run the heater like that while parked in one spot for multiple days.

 

[Barko1]

We run two 12 volt AGM batteries in the camper. We always leave the heater on all night. A recent trip to Tahoe got down to 18 degrees overnight. Heater was set at 45 and ran a lot. No problems. That said, we had driven about three hours to get to camp, so the batteries were fully charged. I would be hesitant to run the heater like that while parked in one spot for multiple days.

I'm running two cheapo 12v batteries in the camper and have a 1500w inverter which, as I guess many do, has a very nice voltage indicator. I added the second battery to insure that the furnace would always run. I also have a Northern Tool 15w panel on the roof that has it's own battery indicator and keeps the batteries in good shape, at least when there is sun. Here is a decent inexpensive inverter, 1250w continuous for just over $100. http://www.sierratradingpost.com/p/4376,1352K_Wagan-Continuous-Power-AC-Inverter.html The microwave suck batteries dry fast

 

[robojeeper]

I do a four battery setup,two in the camper and two under the hood. 3 of them are tied together to run everything for camper and 4th is isolated for engine only.I have ran my heater all night for 5 nights no problem at the minimun temp 45/50 degree and snow on the ground.I changed all lights to 36 and 48 flat led style.I use a 100w inverter only for a tv or shaver etc.couple times for electric drill.Make sure to use size 6awg minimun size 4 or 2 is better on the inverter.the batteries are interstate ultima blue top,they are expensive but an 8 years life.they do take 2 days to recharge after I get home with my 8amp charger. Hey comfort is not cheap!

 

[rich]

Thanks for the info guys,

Does anyone have an aftermarket gauge suggestion?

 

[rich]

I do a four battery setup,two in the camper and two under the hood....Hey comfort is not cheap!


Wow Robojeeper that sounds like a bomber system but where do you store all the liquor with that many batteries on board?

 

[fish more]

I installed two AGM batteries from Cabelas, group 24 size. These batteries have the highest reserve power of any AGM's I looked at, while shopping for batteries. I can camp for three days, running heater, lights, tunes, all on 12 volt, refer is operating on propane, but still draws alittle 12 volt power. After three days I still have plenty of power for 12 volt. I have added a marine battery charger to recharge the batteries, normal recovery rate using the 10 amp charger is approx 6 hours. It's all about reserve capacity of your batteries. Check these batteries out, I have been very happy with them, they perform very well. And yes, still room for the booze !!

 

[camelracer]

Thanks for the info guys,

Does anyone have an aftermarket gauge suggestion?



Rich,

I installed this digital voltmeter as have several others in the group. Works good for me.
www.alliedelec.com/Images/Products/Datasheets/BM/LASCAR_ELECTRONICS/572-0002.PDF

Dick

 

[mtn-high]

A bit off topic..but "battery" related and possibly of help to someone else (?)

I was out and about yesterday and came out of an establishment to find my truck battery drained (ah...kids and car stereos). I had jumpers but there wasn't any movement around/anyone nearby...so after the initial bum out and standard "WTF???" period I started thinking about the battery in the FWC that is ALWAYS chaged fully via the solar panel....

I dug under the cushions for the battery and unhooked the nifty velcro strap and then sat the battery (still hooked to the camper cables) near the sliding window in the FWC. I had just enough power to get the rear slider down in the Tundra and fortunately...the cables JUST reached from battery to battery.

Click........ Vroooom.....problem averted.

I love my camper

mtn

 

[HikerCook]

I installed two AGM batteries from Cabelas, group 24 size. These batteries have the highest reserve power of any AGM's I looked at, while shopping for batteries.


Please explain to me what is meant by "reserve power". Cabela's online battery buyer's guide gives good definitions of MCA, CCA, and Ah but not their own mysterious "reserve capacity" specification. They also carry the Optima D31M which they state has a reserve capacity rating of 155. The Optima website lists the D31M as having a 75Ah capacity so they are obviously two different specs. I'm hoping to install a 120v/12v fridge in my camper next spring and will upgrade to a dual battery bank at that time.

Thanks,
Mike in ElDo

 

[craig333]

As far as batteries, on the other sites everyone is raving about the sear diehard platinum. A rebadged Odyssey AGM. Very pricey but I'll probably get a set when its time to replace the truck batteries. Hard to put a price on having reliable power.

http://www.sears.com/shc/s/p_10153_12605_02850131000P?vName=Automotive&cName=Batteries+%26+Chargers&sName=Marine+Batteries

 

[rich]

Rich,

I installed this digital voltmeter as have several others in the group. Works good for me.
www.alliedelec.com/Images/Products/Datasheets/BM/LASCAR_ELECTRONICS/572-0002.PDF

Dick


Dick,

That looks nice, small and simple to install which is just what I was looking for.

Thanks

 

[leadsled9]

Thanks for the tip on the battery craig333. That's the one I want when the time comes.

 

[dsrtrat]

Hello Everyone,

We are back from a two week road trip which was really the shake down trip for our camper. I am running one 24 series deep cycle battery with the poor mans auxiliary charging system, just a 4 post solenoid drawing power from the windshield wiper motor so it only charges when the key is on. For a little extra safety when off the beaten path I put two quick disconnects in the system as a poor mans battery isolator. In established campgrounds I don't worry about it but for a little extra piece of mind in the back country I pop the hood and disconnect those two spots which means even if the solenoid fails the camper can't draw the truck battery down. The system worked great, even when stopped for 4 days with minimal heater usage the lights didn't even dim. However, one night in Death Valley we decided to set the thermostat and leave the heater on and able to cycle overnight. We woke up to a dead battery. My in laws were near by with a battery charger and generator so we just drove to them and charged back up. It was a good test. Also we found ourselves wanting to charge the laptop in places without shore power so I got thinking about an inverter. This left me with a few questions that you all may be able to help me with.

1. For those of you running two batteries and perhaps larger batteries are you able to set the furnace thermostat and leave it on overnight or is that always too much draw?

2. For those running hard wired inverters how many watts are you running and do you need to have two batteries to keep the lap top and phone charge draw from killing your battery?

3. I want to install a meter that gives me real time info about my battery charge. I know FWC and ATC install them in their new campers but has anyone found an aftermarket one that they really like?

Thanks for the help guys!

Rich


Hi Rich,

Why not just run the cell phone and laptop off the 12 volt system and avoid the large inverter losses? You are going from 12 volts to 120 and than back down to 18 or 20 volts for the laptop and 3.7 or so for the cell phone. Everytime you change voltages you have large losses, most of your power is going to heat the inverter and run it's fan. I have a 12 volt adapter for my laptop and cell phone, they don't drain much off the single battery I run.
Might be cheaper to buy a 12 volt adapters and skip the inverter. You will still have losses in the chargers but less than with an inverter.
Dsrtrat

 

[rich]

Hi Rich,

Why not just run the cell phone and laptop off the 12 volt system and avoid the large inverter losses? You are going from 12 volts to 120 and than back down to 18 or 20 volts for the laptop and 3.7 or so for the cell phone. Everytime you change voltages you have large losses, most of your power is going to heat the inverter and run it's fan. I have a 12 volt adapter for my laptop and cell phone, they don't drain much off the single battery I run.
Might be cheaper to buy a 12 volt adapters and skip the inverter. You will still have losses in the chargers but less than with an inverter.
Dsrtrat


That is a good idea Dsrtrat, I will look into that. There is one 110 appliance that I really want the inverter for which is a small 110 space heater. We set it right above the fridge next to the bed and if it gets chilly in the rack at night I can just roll over and turn it on and we are warm in 2 minutes or less which is really nice. We used it on this trip when we had shore power and it came in really handy.

 

[HikerCook]

Please explain to me what is meant by "reserve power". Cabela's online battery buyer's guide gives good definitions of MCA, CCA, and Ah but not their own mysterious "reserve capacity" specification. They also carry the Optima D31M which they state has a reserve capacity rating of 155. The Optima website lists the D31M as having a 75Ah capacity so they are obviously two different specs. I'm hoping to install a 120v/12v fridge in my camper next spring and will upgrade to a dual battery bank at that time.

Thanks,
Mike in ElDo


I found the answer to my question here http://www.batterystuff.com/tutorial_battery.html#11

"Reserve Capacity (RC) is a very important rating. This is the number of minutes a fully charged battery at 80 ° F will discharge 25 amps until the battery drops below 10.5 volts."

Mike in ElDo

 

[Barko1]

I just read this on an RV Boondocking site and I though it might be of interest. I agree with the post above about avoiding the inverter for things like cell phone however be careful charging laptops with cheapo 12v cig lighter plugs, I had one melt from the current draw.
____________________________

But now battery companies spread around the world are working feverishly to invent the breakthrough battery that will change transportation forever. One such company is Mastervolt that has developed a 24 volt lithium ion battery. Weighing in at just 115 lbs., the output is that of four 8Ds. Think of that. A single 115-pound battery functioning as well as four 140-pound batteries--or 560 lbs! Not only that, Mastervolt claims that their battery will last three times longer than the 8D. (Group 8D AGM batteries are powerful 12-volt, 225 to 255 Amp hour, heavy duty, deep cycle batteries costing several hundred dollars and used in large luxury RVs and yachts.)

Though available now only in 24-volt and being marketed to yacht owners, a 12-volt version is in development, which could be a breakthrough for RVers--and especially for boondockers. There is one slight hitch, though. The battery costs $7,500. However, with a smaller 12-volt version, and as demand and manufacturing mass production come together, prices will come down. How far down, is hard to tell, but with competing companies also pushing the same development, it may--hopefully--be sooner rather than later.

 

[rich]

Though available now only in 24-volt and being marketed to yacht owners, a 12-volt version is in development, which could be a breakthrough for RVers--and especially for boondockers. There is one slight hitch, though. The battery costs $7,500.
[/quote]

Well $7,500 is a lot more than I have in my camper right now but if they come down that would be the battery to have.

 

[pods8]

Dick,

That looks nice, small and simple to install which is just what I was looking for.

Thanks


Just watch how you wire it in, you're supposed to actually use some resistors to isolate if from motors and such if you have them on your system. I didn't know that and my water pump roasted mine.

That is a good idea Dsrtrat, I will look into that. There is one 110 appliance that I really want the inverter for which is a small 110 space heater. We set it right above the fridge next to the bed and if it gets chilly in the rack at night I can just roll over and turn it on and we are warm in 2 minutes or less which is really nice. We used it on this trip when we had shore power and it came in really handy.


Keep in mind using batteries to power an invertor to power a resistance based heater is likely going to SUCK down the juice. Might want to crunch the numbers first.

I'm running two 6V agm 210amp hour batteries in series. I haven't calculated run time but would likely easily get a couple days off the heater. For just lights and such I can run a long time.