New to all this 12v power stuff, need advice on these batteries.

[228B]

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The "nancy heating pad" is a requirement to keep the Mrs and dogs happy.

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In all sincerity, I can't argue with that. However, the fact remains that even if you were given a "pass" to ignore the necessary battery-life 50% discharge guideline (one that experienced 12V users everywhere do their absolute best to adhere to), you still wouldn't have enough battery capacity for two nights' use of the devices you wish to use... and that is also when not considering the effects of Peukert's Law (that a battery or battery banks' capacity is further reduced under load in proportion to increasing amp draw/heavy loads)
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What should you do? Tough question. No matter which way you slice it (cheaper batteries with a bit more capacity, etc... a tradeoff that may net you minimal gains yet produce the result of too-short battery service life) when you work the simple math necessary to figure your load's amp draw or watt draw vs. battery capacity X # of cycles (days) you'll find that you're behind the 8-ball here in regards to your budget vs your stated needs.
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If we seem harsh, I apologize... we (if I may include workerdrone tgreening and unseenone) think it better to give it to you with no sugar coating; better than you having spent all your dough then on the second night of your trip have the batteries arrive at a zero state of charge, have on your hands a shivering, miserable wife then no hot tea. Why not look towards, as workerdrone suggested, a liquid-fuel stove? You could have boiling water in +/- 3 to 5 mins. Remember the old saying, "One cannot afford the castle if one cannot afford to heat it".
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Please keep us posted on any new developments.

 

[bunce1260]

After reading up on these golf cart batteries, I don't think they'll work as they off gas and the batteries are going inside the van. Unless it's easy to put them outside somehow? Nothing about this van is turning out easy though.

 

[dwh]

This mattress pad http://amzn.to/1SLoRWb uses about 7 amps/hr

This kettle http://amzn.to/1DsqEII uses 8 amps/hr but would only be on for about 10 mins at a time.

For a 7 hour sleep and a nice cup of tea in the morning 75ah would work right?

So you're batteries are 100% dead in one night. That will shorten their life to probably around 300 cycles.

IF you fully recharge them after you do it.

No problem doing a full recharge with an alternator. Shouldn't take more than 16-24 hours of driving time...


You gotta either dump that heating pad or add some serious solar. No other choice.

 

[workerdrone]

After reading up on these golf cart batteries, I don't think they'll work as they off gas and the batteries are going inside the van. Unless it's easy to put them outside somehow? Nothing about this van is turning out easy though.

They do off gas. They're like mouse farts of hydrogen, but really if you're doing things by the book you should put them in a compartment (build a quick sealed box), then add an outside vent. If you're handy and can scrounge it could cost you free.

 

[calicamper]

Avoid electric heat products and you can make this work. As mentioned the electric heating items are basically only worth using for on grid power. Battery only system you either need a big bank of batteries or need to figure out an alternative to the electric heat. There is a big reason propane is used for heating in off grid situations. Also keep in mind most solar set ups are cheaper than reworking stock electrical systems on vehicles to address the added power needs of off grid living etc. The advantage to having a solar panel or two on the lid is that your generating power during the day to help off set the power use at night. Even a 80-100watt panel will have a considerable impact on your battery life and also the load your alternator is having to cover when your running the van.

 

[highdesertranger]

lots of good advice here. 1st add up your power consumption. this will give you your battery size, remember no more than 50% discharge. that's the max, actually it's better to shoot for 30-40% discharge. gives you a little wiggle room and reserve. your batts will be much happier. trying to heat with electricity is very inefficient. a down comforter and a dog is 1,000 times more efficient than an electric blanket. a coleman stove and a couple of hot water bottles work almost as good as a dog. after all your camping no need to bring your house with you. a solar panel or 2 will greatly extend your time out. highdesertranger

 

[bunce1260]

So after reading through all of the advice here, I think it's clear that without spending a fortune on batteries my plan's not going to work.
So after doing a lot more research I have a new plan.

This 100 ah AGM battery http://amzn.to/1Eo96su wired with this battery isolator http://amzn.to/1L71DCW so that I can charge from the alternator while driving and not drain my starting battery when camping. Then hook up to this 100w solar panel kit http://amzn.to/1f8WRcw so that it's constantly charging during the day. Mono is more efficient than poly, right?

The 12v kettle is thrown out the window, I'll just have to get up and crack the windows and fire up the propane stove. We will be keeping the 12v heating pad though. It will greatly increase the camping season for the wife.

I appreciate your input and would love to hear what you think of my new plan. Thanks heaps.

 

[228B]

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That is an excellent panel. The charge controller should be sufficient. What you will have to mind, however, is the wire size from the controller to the battery. If you size this correctly and place the controller very near the battery, you may not need to tie into the vehicle's charging system.
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Of much importance here, though, is the amp draw from the electric bedding. What does it say on the packaging? We need to know that load to calculate the overnight draw on the battery.

 

[highdesertranger]

x2 that is the single most important thing. what is the amp draw. add everything up that will determine everything. it's a waste of money to over/under buy. you want to be over a little but not tons. especially if you are just weekending. highdesertranger

 

[rayra]

casual perusal of the 12v electric blankets - and you DO want a native 12v blanket, instead of a house blanket and an inverter, with it's attendant power loss / inefficiency during voltage inversion - shows them drawing about 4amp. You run that about an hour when you get in bed, and you won't incur much power use. Forget the electric coffeepot. Propane is cheap and easy and relatively quick if you can't take a little chill to do that the outdoors probably aren't for you.

Don't get hung up on the de rigueur '6V golf cart battery' answer. Or the ridiculously minor issue of hydrogen venting. A good big AGM battery will do, just follow the precautions on drawing it down more than half. Better to start your vehicle and run it at a high idle for 20mins / day every morning. That will go a long way towards topping off your battery and let you run the vehicle heater for the missus, while you get cold making her coffee.

An amp-hour (Ah) is a 1 amp draw for 1 hour. A 35Ah battery gives you about 16Ah of useful power before recharging becomes an important issue. 16hrs at 1 Amp. 4hrs at 4 Amps. So you aren't running that electric blanket all night.

There's lots of ways to charge that 'house' battery, in a wide range of costs. Low-tech, you wire it to your alternator output same as your car batter, and put a cutoff switch in it so you charge up your car battery first, before connecting your 'house' battery. That same supply wire should also have a diode on it, which acts as a one-way gate to the 'house' battery, so as to not backfeed the car system from the house battery and screw up any car computer or alternator charging readings. You will also want to make sure to disconned the house battery from the vehicle charging circuit when it s time to use it, so as to not drain the car battery. This is the low / no budget solution.

There are a variety of charge controllers that combine various features link power inversion / conversion, isolation, and low-voltage cutoffs to prevent damaging discharge levels. Wide range of prices equal to or even exceeding the cost of 1 or 2 batteries.

Use 12v LED light bulbs in your interior lights or a battery (AA or C/D) lantern as an interior light / reading light.

Get an inexpensive portable solar panel. There are many under $100 that will net you 5-10amps / hour, depending on optimum placement and conditions. Having such might forestall the need to start the vehicle every day. Or just structure your trips so you drive and camp in a different spot each night. A camping tour such that you see more and coincidentally fully charge your batteries each day.

And that's another thing. Unless you really and severely drain your house battery as a matter of course, it doesn't take terribly long to charge it up again. Even econo-cars have at least a 60amp alternator. Far in excess of the power drawn by the ignition and core electronics. That's a lot of power going back into any battery connected to it. Not sure where these dour predictions of having to drive all damned day come from.
Additionally / related, most vehicles have at least two different Amp output rating alternators offered as factory options. It's a simple matter to upgrade to the higher if you don't already have it. Some vehicles have three tiers available. And that's not even counting the higher output aftermarket engendered by today's high-powered sound systems. Lots of options from inexpensive to ridiculous in this approach.


In summary, for your basic system and low budget -
A good big single 'house' battery, preferably AGM, preferably 'deep cycle'.
Use as many 12V-native devices as possible. Use a right-sized inverter, otherwise (the closer its output matches your needs, the less power is wasted in the conversion, don't buy a 1000W inverter when a 100 will do)
Get a $3 multimeter from Harbor Freight (there's even 'free' coupons available) and learn how to use what it tells you about your house battery voltage level.
Get a small inexpensive 'dashboard' type solar panel, that you can jack into your 'house' battery during peak daylight hours. Learn how to use it effectively.
Find what balance you need between battery use and engine running to get the power performance you need.

That's anywhere from $200 to $400, depending on what you buy.


Go read up at battery1234.com and solar1234.com

 

[Freebird]

Unless things have changed, motor RPM greatly influences how much power a alternator (or generator) puts out.
That thought was mentioned in the "high idle" point earlier. I will expand on the point just a bit.
Idling slow through a camp ground or medium speed on a forest service road will provide way less power generated for the battery than highway speeds...
All very proportional.... Well, last I knew, anyway. Things DO keep changing!

 

[bunce1260]

I'm doing a bit more research on solar panels now, looks like there's a few kits about for the 100w panels. That should take care of any low idling, maybe even just use solar and not wire up to the alt. ??