Possible Setup and Opinions

PuddleJumper

New member
Ok first I would like to thank you for your help and appologize for the "Newb" questions.


Here is what I am looking to do. I am trying to outfit my rig for weekend trips(3-day) and would like to have a setup in place that will last me that long but has the option to add on later. I, as well as most of us am on budget due to im in the middle of the full build and need to be wise with my spending. My goal is to be able to run some small things, but make them last the full weekend. Components such as a small heater in the back of the camper top ran at night(not sure 12v or 110v), a 12v pump for the on demand shower system, interior cabin lights for inside the camper top, charging a laptop most likely during the day and cell phone at night.


Now, I have done a little bit of reading and the consensus ive seen is that for a normal weekend trip to keep a battery charged, a 65-90watt pannel is required. What I currently have is an AGM primary starting battery for the rig and a 80AH standard marine(deep cycle) battery that I plan to use as the secondary "house" battery. only the primary is obviously hooked up currently. Now from my readings(please correct me if im wrong) AGM as primary and wet cell secondary charging is fine but not the other way around? When I state charging, I am speaking of a similar system to the Cheap Isolated Dual Battery Setup . BUT with this setup I would also like to run solar panels. Here is where things get tricky for me.


I found this 100W Starter Kit for $173. Opinions on this kit welcomed! Now if I use this kit would I still hook up the charging cables from the dual batt setup directly too the house battery, or would they go into the charge controller(for some reason I feel this is wrong)? How will the dual batt system cooperate with the solar panels when running down the road? My plan is to put the dual batts on a switch in the cab as well as have a battery disconnect switch(possibly overkill) in line.

And lastly, Will the single battery work for what I would like or do I need a secondary battery in the house system?
 

DiploStrat

Expedition Leader
Some Ideas

Ask three people and you will get five answers. Would offer these thoughts, based on my own experience:

-- When you say a three day weekend trip, does that mean three days without starting the truck engine, depending on solar only?

-- You need to find some way to guesstimate your electrical needs. In my case, cooking electrically and running diesel heat all night, I use about 125Ah per night. Thus a weekend without running the engine would require 350-400Ah of usable battery capacity. You will probably need less, UNLESS you plan on running an electrical heater. Especially a 110v heater through an inverter. So you really need to get a handle on your power needs before you go much further.

-- Remember the 50% rule; conventional lead acid batteries (AGM or open cell) should not be discharged below 50%. So to size your battery bank, take overnight use * days without starting * 2. E.G.: 50Ah per night * 3 nights = 150Ah * 2 = 300Ah. That's a lot of batteries.

-- That quickly generates a BIG number. You can reduce this number by between 20 and 30 Ah per 100w of solar panel per sunny day. Obviously, this varies by amount of sun, amount of rain, etc. For this reason, I always guesstimate on the lower side.

So your first task is to get a handle on how much battery power you need and determine if you have the space and weight capacity to carry those batteries.

That done, what kind of batteries? Lithium Iron offer much, much better performance, but are too expensive for most of us and it can be hard to find proper chargers for them.

That leaves AGM and open cell. Both perform very well; AGM is more expensive, but easier to mount and does not need/cannot be topped up with water. Open cell are less expensive, but require more maintenance and proper venting. Modern open cell batteries, like Trojan, also want very high charging voltages.

After that, how are you going to charge them? Scholars differ, but I like a relay based system, loathe diode isolator systems, and am not convinced that most modern vehicles have any need for a Battery to Battery (B2B) charger. The advantages of a relay based system, and a ton of supporting information on how to set one up, are presented here:
http://www.smartgauge.co.uk/technical1.html If you want a contrarian view, read the articles at the bottom of this page, specifically the ones marked "Must Read": http://www.sterling-power.com/downloads.htm You will note that while Messers Gibson and Sterling agree on the need for a high voltage, multi stage charger, they differ on whether or not a modern vehicle will provide adequate voltage. (My buddy dwh is even more convinced than I am that alternators back through the 1980's at least have a charging voltage that is more than high enough.)

On my truck, I use two charging systems:

-- The camper batteries are connected to the starter batteries by a relay (solenoid). This means that when the engine is running I have the benefit of 200A of alternators which produce a very high charge rate during the boost or bulk charging stage. The critical elements in this type of system are: A) Adequately sized wire, calculated to handle the maximum output of your alternator over the distance from the alternator to the batteries and back, and B) An adequately sized relay (solenoid).

-- The camper batteries are directly connected to a solar charger. The solar charger produces less current, but it continues the charge process through the acceptance/absorb and float stages, long after the engine has been shut off. I think that this extended charge time is very important as it assures that the batteries are more likely to achieve a complete charge by the end of the day. You can read more about the importance of adequate acceptance/absorb charge, and the problem of surface charge, here: http://www.smartgauge.co.uk/surf_chg.html Basically, it is highly unlikely that you will ever run your engine long enough to achieve a full charge, hence the desirability of a solar or shore power charger. Buy a decent kit, from a reliable supplier, and, most important of all, make sure that the wiring is adequately large, excessive resistance, which produces voltage drop, really hurts performance in low voltage systems like these.

Basically, for an overland camper, I recommend two charge sources: the vehicle alternator for the bulk charge and a solar kit for the acceptance charge. Your batteries will happily accept a charge from two sources at the same time when you are driving down the road on a sunny day.

Finally:

-- While a key controlled solenoid will work, I prefer an automatic or intelligent relay as this connects your batteries whenever there is a charge available from either the engine or the solar kit. (Nice for the time your truck is sitting without the engine running.)

-- Fuse all but the shortest cable runs at BOTH ends. Remember, the circuit can be live from either battery.

To your last question, I can't comment on the solar kit you reference, but I have had good service from AM Solar (
http://www.amsolar.com and happily recommend that you chat with them. I would buy a controller large enough to handle the maximum number of panels that you will ever need; makes it much easier to upgrade.

You can read more about how my truck works here:
http://diplostrat.org/about/

Hope this is helpful.

 
Last edited:

PuddleJumper

New member
So looking into heaters and what it would take to run them, as this would be the key thing I would want to run. It looks like solar is a horribly innefficient(read expensive) way of heating a space. http://www.solarpaneltalk.com/showthread.php?8625-150-watt-12v-Heater-on-Deep-cycle-bank-Will-it-work I have been reading a few threads on similar questions and this one looks like it really puts it to light. Looks like multiple batteries required even if just for a 150 watt 12v heater. So are these theories all true? Is the real world just like the math says it is? If so, what are other people doing for heat? Honestly it is looking like solar is going to be useful for the other things I would like to run and actually still a feasible option, but those coupled with trying to use electric heat just may not be the way to go.

so what are my options? How about smaller camp generators such as the Generac Ix800 If I go this route this its 4 stroke so could just refill with spare jerry cans. but how is the noise level on one of these and seems I would want to build some sort of platform on the front of the truck and lock it down just for security sake. How about a mix of the two?

I honestly thought I was starting to have a hold on what I needed and was going to get.. dang.:confused:
 

DiploStrat

Expedition Leader
Hard Numbers

The comments on the site link you provided look about right.

Solar is not a very efficient way to make electricity. So why use it?

-- The price is right. Not the price of purchase, but the price of use - sunlight is free.

-- The time is right. Proper charging of a large battery bank (200+Ah) takes a L O N G time, much longer than you probably want to run your engine or a generator. A solar kit keeps going as long as there is light.

I use a Webasto Dual Top hot water and hot air heater. It runs on diesel fuel and draws about 5A per hour.

As a practical matter, you probably want a propane or diesel furnace. If you are short of electrical power, you might want to
consider a propane powered catalytic heater.
 

wrcsixeight

Adventurer
I have a 200 watt heater that draws 18 amps when powered by my inverter. In 3 hours my group 31 battery is well below 50%

Rethink electrical heat. The 200 watt heater can barely take the edge off of a cool night in the high 30's and keep my lightly insulated Van in the low to mid 50's.
 

PuddleJumper

New member
The comments on the site link you provided look about right.

Solar is not a very efficient way to make electricity. So why use it?

-- The price is right. Not the price of purchase, but the price of use - sunlight is free.

-- The time is right. Proper charging of a large battery bank (200+Ah) takes a L O N G time, much longer than you probably want to run your engine or a generator. A solar kit keeps going as long as there is light.

I use a Webasto Dual Top hot water and hot air heater. It runs on diesel fuel and draws about 5A per hour.

As a practical matter, you probably want a propane or diesel furnace. If you are short of electrical power, you might want to
consider a propane powered catalytic heater.

I am trying to outfit a truck bed with camper top, diesel and propane heat just seem like more things to carry/expend on a trip. not to mention trying to figure out where to put a propane bottle securely while offroad.

I also have a worry while camping about sufficient sunlight as I am on the east coast and most places i go camping/offroading are in the woods in the hills and mountains.

I have a 200 watt heater that draws 18 amps when powered by my inverter. In 3 hours my group 31 battery is well below 50%

Rethink electrical heat. The 200 watt heater can barely take the edge off of a cool night in the high 30's and keep my lightly insulated Van in the low to mid 50's.

So you have a single battery? what is the amp hr rating on it 90-100 amp hrs? so with this info, if I were to run 2 batteries I should be able to get 6hrs or so of sufficient heat which could take us through the night depending on outside temperature. you also state you run this heater via an inverter which to my understanding wastes about 20% of energy? so in theory if I run a 12 volt heater of the same wattage, I could get 7.5-8 hrs heat time which would be perfect.
 

DiploStrat

Expedition Leader
Camper Top?

You mean something like this?

original.jpg


In which case, you might want something like this: http://www.campingworld.com/shopping/item/olympian-wave-8-catalytic-safety-heater/19334 You could plumb it into your stove.

As a practical matter, with just a truck topper, you are probably better off with warmer clothes and a better sleeping bag. Big dog never hurts, either.

I have a 600Ah battery bank and I would not even think of electric heat; at least not with any product that I have yet seen.

Final point; there is plenty of sunlight on the east coast, ironically, especially in winter.
 
Last edited:

wrcsixeight

Adventurer
I have a single group 31 battery I use as house battery and it is rated at 130 amp hours.

Look into the peukert effect. it basically says the higher the load on the battery, the less capacity the battery has to give, and a 18 amp load is a big peukert component an a hundred amp hour battery, which is rated at 100 amp hours under a 5 amp load. A hundred amp hour battery will have about 60 amp hours total to provide at a 18 amp load, and only half of that should be used.

Even if you do sucessfully power a pitifully ineffective heater electrically one night, the batteries are going to be so depleted and need a long time to be recharged, and if you cannot achieve a true 100% recharge, which is extremely unlikely, then the next night you might not get half the time from the heater, and the next night half of that, and then the batteries will be punch drunk and need a long time on a grid powered charger to return to baseline specific gravity and their maximum remaining capacity, as these deep and abusive cycles will have compromised their capacity to some degree.

Rethink electrical heat. Think about a propane powered catalytic heater and leave a window cracked. People have been doing this successfully for a long time. Few sucessfully can do electrical heat, and those that do have large battery banks and extreme solar arrays to replace what is used.
 

Forum statistics

Threads
185,530
Messages
2,875,570
Members
224,922
Latest member
Randy Towles
Top