Fairly new to power options... Dual battery? solar? stand alone deep cycle?

[TEC3]

Hey guys,

Been around Expo Portal for a while but really am just now venturing into upgrading electrical stuff and need a little guidance.

My current setup is my factory battery running normal Truck power, LED lighting, a winch as well as charging phones, laptops etc on a dying little 400watt inverter. I have a deep cycle in a walmart battery box that I charge at home and will bring with us in the back of the truck. I will use it while camping to run additional lighting, etc...

I have a trip coming up where we will be off grid for a few weeks and power recharging(campground/ outlets) will be minimal to none.

I am interested in going to a dual battery setup with Optima red tops but don't know much about them. I am pretty sure I would like the system to charge both batteries off of the Alternator but be able to monitor both batteries and switch when I get one too low/ know when to run the truck for power.

I have also considered just using my current Deep cycle and this http://www.zumasrusstore.com/collections/zuma-50-89-01-parts/products/charger-solar-5w
To get me through the trip.

Please send me suggestions, concepts and best practices. I am excited to learn, just need to know what I should be learning. We currently will not be running a fridge, but if I get it all set up correctly I would be interested in moving from coolers to a fridge setup. I work at a college and have access to a cube(dorm) fridge, would that be too much to run on a dual battery setup?

 

[dwh]

In a hurry, so just a hit and run reply...

5w of solar is nothing. Want to run a fridge? - figure on 50w minimum. Want to run a fridge and a laptop and charge your phone AND still charge your big battery? Better start thinking about 100w or more.

Dorm fridges draw a lot of power for what they are. Pretty much the worst possible fridge you could use on batteries. Only thing worse would be an RV "3-way" fridge running on battery instead of propane or shore power.

 

[AndrewP]

If you are going to really be away from external power, and sitting so your truck isn't running every day, you need a couple of things.

1-You need a second battery dedicated to your "house" loads, so you are never pulling power from your starting battery. There are other ways to do this, but this is easiest and probably best for you as it sounds like you're new at the offgrid electrical game.

2-You need a way to charge the #2 battery when running (easy-see the $50 dual battery thread), and a way to charge it when not running (solar likely your only good option) There are better dual battery systems than the $50 system, but if you understand how that works, you will also understand what you might need or want. Me personally, I like the Blue Sea ACRs (automatic charge relay) but there's a lot of good stuff out there.

3-For a small ARB/Engel camping fridge you still need substantial solar power-like 100 watts MINIMUM. 5 watts is a Joke. The solar charges your #2 battery during the day, your fridge draws it down at night. Just for instance a real camping fridge uses about 3 amps while running (a dorm fridge off an inverter would use 10X that or more). I always figure about 2 amps per hour for my fridge so 2aH X 24 hours =48 aH, which is all the charge you can safely pulled out of a 100aH battery before it it half charged. And most batteries are less than 100aH-often 55-75 is more like it.

Each one of these things though requires considerable thought, and knowledge which is hard to manage in the rush before a trip. You need to learn about power usage, voltage drop, wire sizes, fuses, charge controllers and a whole bunch of things that individually are easy but in aggregate can be pretty difficult to wrap your brain around It sure was for me. Even learning why 5 watts is a trivial and almost useless amount of power would be a good place to start.

The easy way to monitor your batteries is with a volt meter. For quick and dirty purposes 12.3 volts is about a 50% charge with your average car battery. Since its very hard on most batteries to go below 50% charge(it will damage them permanently), every time you get to 12.3 it's time to charge. A full battery will read about 12.8 volts.

You need to learn to conserve power too. Minimize lighting(use a flash light), forget using your inverter which is likely wasting 50% or more of the input power, and minimize uses like playing music, watching TV, etc. Charge other gear only when also running your motor for battery charge.

Learn to think in Amp.Hours or Watt.Hours. For instance, lets say you want to charge your 1/2 charged battery by running your truck. Let's say it's a 100 aH battery so it still has 50aH in it. Lets say you have a good alternator that can put out 100amps at a voltage appropriate for charging. So theoretically you could charge your battery in 30 minutes(100amps x 0.5 hours = 50aH). The problem is, the battery can't absorb a full charge that fast, and to fully charge may mean running several hours to really charge things up to their full potential.

Lets's also figure your 100 watt solar panel can make 5 amps into the battery for 10 hours per day. That's 50 amp hours. That will basically just barely keep up with your fridge alone, but any other loads will deplete the battery. So there is no quick and easy way to do any of this and what ever you do will cost more than you think. What are your mandatory loads, and how much power do they use. Start there.

One other thing-My experience with Optima Red tops has been bad. Their Blue Tops were OK. But I have given up on expensive batteries and essentially always use the Costco Grp27 Marine batteries. Good battery for 3-4 years, good warranty at Costo, hold 100aH, and tolerate deeper discharges OK.

Good luck.

 

[jonyjoe101]

the optima red tops are mostly for engine cranking. The blue and yellow tops are for deep cycle/cranking but there main weakness is all of them have low AH ratings. The biggest one is about 80 ah.

For your use I would recommend to get at least a 100 ah battery, myself I prefer agm because they don't need to be refilled with water and wont leak acid. Even a 100 ah battery only has 50 ah of usable power available, you don't want to drain them below 50 percent. 12.7 volts is fully charged, 12.1 volts is about 50 percent charged. If you drain them below 50 percent it reduces there life.

Solar power is more complicated and requires alot of room on your roof to be worthwhile. I have a 240 watt panel on the roof of my astrovan connected to a 20 amp ecoworthy mppt controller feeding a 102 ah kinetik hc2000 agm battery. The solar panel produces about 12 amps of power at midday. I wouldn't recommend anything smaller than 100 watts. you need at least 5 amps of charge power to do any battery charging. 5 watts is mostly to prevent battery self discharge. The kinetik is used mostly for extreme car audio systems but works great in solar, after a day of solar charging it reads 12.9 and its rare i get it below 12.5. Originally I had a very heavy 145 ah UPS type of agm battery, after a day of charging it read 12.7 and in the morning it would read 12.3. High quality battery is the way to go, the optimas are good quality just there AH are on the low side.

if you are going to charge your house battery from the alternator you need an isolator, its best to get a smart isolator. the smart isolator will charge your start battery first when it reaches full charge it connects both batteries and charges the house battery. When you turn off your engine, it disconnects the start battery (isolates both batteries) to prevent it from draining. Wirthco battery doctor isolator is a smart isolator, it also lets you connect your house battery to the start battery in case you need to jump start. There are other type of isolators available, the non smart ones just connect both batteries together as soon as you start the engine.

A small AC dorm fridge because of the thin insulation uses too much power even for dual batteries. 12 volt fridges are expensive in the 600 dollar range but they all use the danfoss compressor which is very energy efficient. The one I had edgestar fp430, used 27 amps of power in 24 hours when set to 40 degrees. The other alternative if you have the room is to get a small chest freezer and use a freezer to fridge thermostat conversion. These will use as little power as the 12 volt fridges because there thicker insulation (thicker than the 12 volt fridges) will reduce how much the compressor has to run.

 

[TEC3]

OK, read up on everything you guys suggested and even on the 50 dual battery setup. I Think it all make sense. I don't do a bunch of wiring, but I do understand it. So I am going to start with that setup. I have my exisiting battery(starter) and I have a Deep Cycle battery I use on trips already that will be the (House) battery. I am going to see if I can mount them side by side. Not sure both will fit. If not I have a few other spots but will need a tray. Any suggestion on a good quality tray or will anything from the old google search work?

The 50 dual battery setup says to use old Jumper cables, I have a set that my wife wonderfully ran over the clamps and flattened them. I knew I held onto them for a reason. So basically I need Fuses, Solenoid and a few other small odds and ends. Now I plan on wiring the winch to the starter battery, but The house battery will run to a wiring block that I will run all the house items in the bed like inverter, lighting(Rack lighting/camp lights and bed lighting) etc... When I run the truck it will charge both, but when I stop it should only drain the House as long as I am only using the lighting/ inverter that are ran to the wiring block for the house battery, right?

As for the fridge. I am not their budget wise yet. It is on the list, but not yet.

 

[dwh]

The 50 dual battery setup says to use old Jumper cables, I have a set that my wife wonderfully ran over the clamps and flattened them. I knew I held onto them for a reason. So basically I need Fuses, Solenoid and a few other small odds and ends. Now I plan on wiring the winch to the starter battery, but The house battery will run to a wiring block that I will run all the house items in the bed like inverter, lighting(Rack lighting/camp lights and bed lighting) etc... When I run the truck it will charge both, but when I stop it should only drain the House as long as I am only using the lighting/ inverter that are ran to the wiring block for the house battery, right?

You could also use new jumper cables. 4 gauge can be had pretty cheap. Old cables are not required

Sounds like you are on the right track.

Yes, the batteries will be isolated when the ignition is off - as long as you get power for the solenoid from an ignition switched circuit. Don't tap ACC for the solenoid or the batteries will be tied while you're just sitting in the truck listening to the radio...

Inverters tend to use a lot of power - even a 400w unit will draw 400w / 12v = 33.3a at full load. They work best wired directly to the battery with some of that fat jumper cable wire.

 

[GregSplett]

I find this interesting...

For your use I would recommend to get at least a 100 ah battery,. Even a 100 ah battery only has 50 ah of usable power available, you don't want to drain them below 50 percent. 12.7 volts is fully charged, 12.1 volts is about 50 percent charged. If you drain them below 50 percent it reduces there life.

so you are saying that taking a standard auto bat below 12v is damaging?

Edit; this would help explain a battery problem i am having in the river rat.

 

[AndrewP]

I find this interesting...

For your use I would recommend to get at least a 100 ah battery,. Even a 100 ah battery only has 50 ah of usable power available, you don't want to drain them below 50 percent. 12.7 volts is fully charged, 12.1 volts is about 50 percent charged. If you drain them below 50 percent it reduces there life.

so you are saying that taking a standard auto bat below 12v is damaging?

Edit; this would help explain a battery problem i am having in the river rat.

Yes, very damaging. voltage/state of charge varies a bit with temperature, but if you pick a cut off at 50% charge you should do OK. I use 12.3 volts as my 50% cut off which is a little conservative, but 12.2 would also work.

For a real starting battery, they don't appreciate much discharge at all, and should be kept nearly fully charged at all times for longest life.

For the original poster-the real trick for you will be to conserve power. Inverters are power hogs because they are so inefficient-ever wonder why most look like a big heat sink? It's because they waste most of the input power as heat. It sounds like you'll be using an older battery of uncertain condition, so don't expect high performance from your system. And really, used Chinese jumper cables? LOL. Tinned marine wire is what you want.

Also for a long term trip, a real camping fridge is smart money. Otherwise you will be stressing over the ice situation every day or two. Ask anyone on this forum, and a camping fridge is their single favorite and most useful piece of gear. It only seems expensive until the first trip you take with it. It always kills me that people think nothing of spending $800 or more on a winch, and $200 for the synthetic cable - both of which sit as decorations on their bumper, and then think a Fridge for $700, that they use every single day all day is expensive.

 

[dwh]

The 50% rule is based on deep cycle battery life span.

Most deep cycle batteries are rated to last for 1000 repeated cycles if drained to 50% and then fully recharged ASAP. Drain them only 20% and you might get 3000 cycles before they need to be replaced. Drain them 80% and you generally only get 500 cycles.

Cranking type batteries are designed to be drawn down just a touch, 1%-3%, when starting the engine, and then immediately recharged. Draining them to 50% or more will radically shorten their life, and you might get away with it only a dozen times before it needs to be replaced.


So the "proper" thing to do is have a cranking battery for the engine, and a deep cycle battery for the auxiliary loads, never drain the cranking battery deeply at all and never drain the deep cycle aux battery below 50%.

That's the conventional wisdom and is usually a good idea.



With the camper I have now, and the way I use it, I adhere to the conventional wisdom only up to a point. I do have a cranking battery for the engine, which I never drain deeply at all (unless I forget and leave the lights on) and a deep cycle battery for the aux loads. Where I depart (some might say deviate) from the conventional wisdom, is that I ignore the 50% rule for my deep cycle battery - I just drain it however much I need to (very often, totally dead), and recharge it whenever I get around to it.

Does that reduce the battery's life span? Oh yes, it certainly does.

But it's worth it.

I've got a 100ah battery. I can get 100ah of usable energy budget from it by ignoring the 50% rule. If I stuck to the 50% rule, I'd either only get 50ah of usable energy budget, or I'd have to have two of those batteries to get the same 100ah usable energy budget.

So if I stick to the 50% rule I can either have half the energy budget, or buy twice as much battery to get the same energy budget - OR - I can buy half as much battery twice as often, ignore the 50% rule AND leave 50 lbs. of ballast sitting on the store shelf - and still get the 100ah energy budget.


I'm not saying that's the right decision for all situations. With a different camper, I might very well go a different route. But that's the way I do it for this camper and the way I use it. It's a camper van, so I do have the room if I wanted to double up and carry two aux batteries. In a smaller rig, there might not be room for two aux batteries - so sticking to the 50% rule cuts the usable energy budget by 50% and that's that.


The point is: There's more than one way to skin an electric cat.

 

[GregSplett]

Thanks a lot guys.

:ylsmoke:

 

[AndrewP]

I basically agree. We all abuse our stuff if the circumstances dictate. Fortunately, 50aH is about the amount my fridge uses in the average day, and my house battery is 100aH, and so rarely really get into the deep discharge situation. Plus, the trips I like typically involve moving every day and so the recharging is not an issue. For the days I stay in one spot, the solar charges my house battery and generally keeps up. As long as you understand that batteries have a finite life span, and that you can make them last a year or two longer with better power management, then those are trade offs you get to make. These are especially important considerations if you buy the really expensive batteries that so many here seem to use.

But real starting batteries are kind of a problem. They don't tolerate even 1 deep discharge very well. I have found this out the hard way-usually by deeply discharging a 2-3 year old battery, that after the deep discharge never really holds much of a charge again. Kind of like killing off a middle aged battery prematurely.

 

[GregSplett]

But real starting batteries are kind of a problem. They don't tolerate even 1 deep discharge very well. I have found this out the hard way-usually by deeply discharging a 2-3 year old battery, that after the deep discharge never really holds much of a charge again. Kind of like killing off a middle aged battery prematurely.


:iagree:

 

[dwh]

You can also prematurely kill a middle aged battery by letting the guy at the auto parts store hit it with a carbon pile tester. They always seem perfectly happy to sell you a new one after that.

 

[CSG]

The reason I hardly ever use the LandCruiser for trips these days in because my PW Traverse, even though only 2x4, has a battery box big enough for two G27 D/C batteries. I trade the ease of running my vertically installed Norcold fridge (2 way), lights, recharging computer, phone, etc. for the trouble I'm able to get into with 4x4. BTW, don't know about the ARB and similar chest types of fridges but I turn my fridge off overnight as the constant on/off cycling annoys me when trying to sleep. It holds cold all night without issue. I probably save 15-20 amps too.