Battery Isolator?? Better Options for power??

[Gigi]

Hi..so I've been really trying to wrap my head around power options for me.  I live in the PNW and will be spending a lot of time in this area as well as doing road trips.  Some BLM camping but maybe not as much as many of you all do.  I am converting a minivan.  Would I be better off getting an AGM battery for my "house" battery and then connecting it to my car battery using an isolator switch?  Bob's blog didn't touch on isolators in any depth.  

Would there be a better option?

Would I be better still going solar and maybe using one of the flex solar panels on my roof?  

I only want to power a fan, charge my laptap and phone and run a very, very, small dometic frig, and stream a movie or 2 every so often.

All tips and suggestions are welcomed!  


Thank you.

 

[Optimistic Paranoid]

Hi..so I've been really trying to wrap my head around power options for me.  I live in the PNW and will be spending a lot of time in this area as well as doing road trips.  Some BLM camping but maybe not as much as many of you all do.  I am converting a minivan.  Would I be better off getting an AGM battery for my "house" battery and then connecting it to my car battery using an isolator switch?  Bob's blog didn't touch on isolators in any depth. 

Some of this depends on how much and how often you'll be driving.  If you're going to try sitting somewhere for days at a time, then no way is your alternator going to be able to keep a house battery charged via an isolator.  If you're driving every day, then such a set up might work very well, depending on how much driving you do.

The problem with alternators as a charging source is that usually the engine battery will not be nearly as low as the house battery, so once the engine battery is brought back to full charge, the voltage regulator will cut back the alternator output to keep from overcharging the engine battery, so not that much gets to the house battery.  There can be work arounds for this problem, some cheap and some not-so-cheap.  But it all still comes back to how much driving and how much sitting you will be doing.

 

[John61CT]

No, as long as the two batteries want the same charging voltage range, and the alternator matches, they can all be in one parallel circuit while charging, and a big empty House bank will keep a decent alt setup pumping out high charge, while your full cheap little starter won't be accepting any charge, no harm done to any of the three.

Best to have the alt wired directly to House, ideally with separate voltage temp sense wire as well.

The ACR/VSR or LVD will open when no charging going on, isolating the starter batt/engine circuit from House bank and loads.

Simple solenoid fine if Alt alone, but unless you're on shore power every other night, you'll need to supplement with solar or a little gennie.

Don't get expensive House batteries unless you're regularly getting them to true 100% charge.

 

[highdesertranger]

you can do both, tie into your alternator and add some solar. highdesertranger

 

[Gigi]

Thank you all for your insights. Sincerely, each of you taught me something new!! I started thinking as I dozed off last night...it's probably not an either-or situation and wondered if I could have more than "just one" power source. Got that answer too. I will start researching a little more on solar now!

Are those flexible solar panels any good?

 

[Optimistic Paranoid]

Are those flexible solar panels any good?

Power ratings for solar panels are all calculated at a standard temperature, I believe it's 77 degrees F.  Solar panels in sunlight get hot, and as they get hot, they lose efficiency.  A rigid panel, mounted with an inch or so of airspace between the roof and itself can shed some of the heat in that space.  A flexible panel, mounted directly to the roof, can't.  I think flexible panels are best reserved for remote ground deployment when you are boondocking, and not permanently mounted to a vehicle roof.

 

[Canine]

Normally Id say whatever Sternwake or Optimistic Paranoid tell you, well, add JiminDenver to that list, and 29chico... well you get the drift. In your case, with a minivan, and you wanting (even a small) compressor fridg and streaming movies, I think that you've passed the point of depending on solely an alternator/solenoid system.

I tried it with a cheapo walmart 29 marine battery in a trolling motor battery box (in order to get the fused connections) with just driving or idling and no compressor fridg and I ended up killing the battery within 1 year (lucky WM took it back). I considered myself (and still do) to be a minimalist on power usage, as I plug in all my portable electronics at a job or coffee shop whenever I could/can yet I still couldn't drive enough (15-20 minutes twice or three times a day doesn't cut it) to do any good.

So I bought a flexible 100W panel off Amazon, a cheapie PWM 10A Chinese controller and 3M taped the panel to the top of the van, running the MC4 connector 10 gauge wire through the cracked open window (have the window guards on them) to the controller then fuse then battery. Haven't had a problem, course I'm not in the PNW either.

Now the 2 days of rain we just had made me nervous as the solar didn't recharge the battery well. I've only got a 1:1 solar watts to battery amps and frankly, its not enough for stretches of bad weather and minimal driving.

That's my setup. Someday I will change vans to get more roof real estate, then have 3-400W solar and 2 golf cart 6v batteries. Someday... :-/

 

[SternWake]

The Alternator's effectiveness is directly realted to how long one drives, the thickness and length of the copper between alternator and house battery, and most importantly, the vehicle's voltage regulator, over which one usually has Zero control.


My battery yesterday at 14.7v was taking 29 alternator amps.  When I reduced voltage to 13.7v, it took only 9 amps from the alternator.

HUGE difference, and most vehicles do not allow 14.7v for very long as they never were designed to recharge a depleted battery tacked onto the alternator charging circuit, but they were designed to prevent serious overcharging, thus the premature drop to 13.7v.  What voltage is chosen and how it is chosen varies very widely among different vehicle platforms.

So By all means utilize the alternator, it is foolish not to, but do not expect it to have the time or be allowed to attain the voltage which can then charge the battery at the limit of its acceptance, and also Know that 80 to 100% charged takes 3 to 4 hours NO Matter what, and without ever reaching a true 100% charged, the battery is doomed to early failure.

Early morning alternator to bring battery to 80% is good, when followed by enough Solar wattage  to finish off the task, or nearly so.

Also have a plug in charging source for if/When one does have access to grid power.  Aim for no less than 20 amps per 100Ah of capacity.

You can beat the F out of a battery, and still get An Ok life from it, IF you can occassionally fully charge it, however long that takes, and an abused battery can take a long long time to get there, usually requiring the automatic plug in charging source be tricked multiple times into restarting.

Restarting it requires one load battery with high loads until battery voltage drops below 12.6v, then restarting charger, then removing loads.

A hydrometer on a flooded battery will show that multiple restarts of the 'smart' charger are usually required.

All 3 of these charging sources can be tweaked/chosen/ modified to perform better, but this can overwhelm the Newb trying to get an overall grasp of it.

For solar, Aim for as much as your roof will allow and get a solar controller which allows some adjustability as to absorption voltage and duration, if possible.
For the alternator charge path, use thick copper from to alternator (+) output stud to isolation device, to Fuse, to Aux battery.  Ground it back to the alternator mounting bolt  or (-) output stud, with equally thick copper.  Not much can be done for the vehicle's voltage regulator's Unideal allowed voltages, not for a Newb not willing to spend 2 to 4 C notes for a DC to DC converter,  and the time to true full charge is still 3 to 4 hours from 80% charged.

For the plug in charger, One which can power all DC loads while charging the battery, without gettng confused by the cycling of the compressor fridge, can go a long way in getting acceptable lifespan from a battery.  "Garage" chargers vary widely in how well they do.  RV converters generally do better, but do not come with sey casings, alligator clips, or blinking lights that also promise to preform oral sex on you like the garage charger marketers claim.

When the battery fails, replace it.  It is only rented anyway. the length of the contract is the variable depending on its treatment.  It kind of sucks when its capacity is so comnpromised the fridge appears to not be working properly anymore, but just know when the fridge becomes unreliable you should be considering a location where it is not so hard to replace the battery.

Many people can get away with very substandard charging methods, as long as they accept the battery will not live long, and not be very reliable.  At some point this person perhaps gets tired of trying to warranty or purchase batteries, then steps up the charging equipment.  

It does not all have to be done at once.

I would recommend the compressor fridge  get a dedicated 10 AWG circuit, and not rely on existing vehicle Ciggy plug 12v receptacles.  Better yet is to bypass the Ciggy plug and receptacle and wire it right to Fuse block.  Make sure the vents on the fridge are not restricted whereever it is located, and that it does not bake in a hot vehicle .

Streaming videos likely will use 3 to 4x as much electricity as the fridge uses in that same time span.

 

[Canine]

Read all the way down on SW's post and you will see the note on streaming video. That's what will push you into solar panel territory. As he said, the compressor fridges, even if the duty cycle is say 5-6 hours a day, won't pull much (maybe no more than what, 1.5 A/hr? The smaller sized ones). So that's not a large load, especially if you buy the insulating bag or make your own. But then if you can justify a several hundred dollar compressor fridg (I presume its new) then you can certainly get a sub $180 100W solar panel, even if its a rigid one. In my case my whole flex panel, controller, wiring fuse set up was under $300.

I did pick up SW says to run the negative all the way back to the alternator bolt. Hmmm, I only ran mine to the nearby passenger seat frame bolt... What say you experts, do I need to return it back to the alternator case? :huh:

 

[SternWake]

Grounding to bolt then requires all current for house battery to flow through original grounds. There might only be a 12 AWG ground between engine battery (-) and firewall, so in effect all alternator current for depleted house battery is bottlenecked on this firewall ground, which was never intended for this 30+ extra amps.

One solution could be adding a frame to alternator ground, but frame grounds cane become problematic all to quickly due to dissimilar metals, and being outta sight outta mind.

Which is why I recommend running equal thickness cables from alternator + and - to house battery, with a isolation device on the red + cable and a fuse close to the battery. This eliminates the possibly problematic frame grounds and will increase amperage into a depleted battery, especially if the vehicles engine battery to firewall frame ground is inadequate, which it likely is.

One could simply choose to upgrade the engine battery to frame ground too, but then the engine battery to engine ground is the weak spot deserved of upgrade too.

So what is 'simplest' might not be any less work or copper than running the cable back to alternator (-) stud or mounting bolt.

Remember the (+) is only half the circuit, and bad grounds are all too common when electrics do not work properly.

 

[jimindenver]

I know renogy stopped selling the flex panels due to them dropping output and getting burn marks. A regular style of panel would give you more options and more output if you are not against having one up there. The good thing about framed panels is they can easily be made to tilt which can improve their output by a fair amount. Last thing is for what you pay for a flexible panel, you would be amazed at what you can get for the money in a regular panel.

Yes do have multiple sources of charging available. You won't always be driving enough and the sun doesn't always shine. The last thing you want is to run out of power and have your fridge shut down, ruining all your food out in the boonies.

 

[Canine]

I only went flexible for lower sight line. I agree that a glass framed panel is superior in all other ways, warranty, cooling, output etc. I was nervous about 1- holes in roof, 2- being noticed, my van has the luggage bars on the back so the taped down flex panel is almost invisible from the side and 3 - I was considering being able to pull the panel and make it a portable setup, so storage is easy being flex.

Reality: A few holes aren't a big deal. 2 - stealth is overrated. Sure I'm more comfortable but I doubt I'm fooling anyone who is really concerned, if you trace the wire through the window that could make you wonder... and 3 - as a city dweller, no chance I will do a portable mount.
The loss of wattage due to hot weather heat buildup and the less quality covering probably wasn't the best choice, but its done. I'm on year 2 and still outputs 4-5 amps at solar noon, so by my guesstimate, I'm normally gaining 15-20 amps a day and using less. Works for my particular needs but YMMV.

 

[Moondancer]

I went to a mechanic and asked him to install a stinger sgp32 200a battery isolator relay  in my Jeep Patriot just to use for my Dometic CF-18.  He suggested  I get  a Jump N Carry/ Booster Pk 1100 Peak Amps instead. It has a 12 V plug on it and  holds a charge for quite a while before needing to be plugged in to DC to get recharged. This is to be used only while traveling and I sleep in the jeep. What is your opinion on getting a Jump Starter to power my Dometic?

 

[Optimistic Paranoid]

I went to a mechanic and asked him to install a stinger sgp32 200a battery isolator relay  in my Jeep Patriot just to use for my Dometic CF-18.  He suggested  I get  a Jump N Carry/ Booster Pk 1100 Peak Amps instead. It has a 12 V plug on it and  holds a charge for quite a while before needing to be plugged in to DC to get recharged.   This is to be used only while traveling and I sleep in the jeep. What is your opinion on getting a Jump Starter to power my Dometic?

The 1100 peak amps and 325 cold cranking amps are meaningless.  What we need to know is how many amp hours is the battery rated for?  And unfortunately, I can't find that info anywhere on their site, not even in the manual for it.

I do note that the whole thing only weighs 18 lbs, which means it has to have a pretty small battery in it.  A true deep cycle battery, which has 100 or so amp hours, would weigh about 60 lbs or more.

So no, I don't think this is going to do a very good job powering your fridge.

Now, you could maybe replace your engine battery with a marine/rv battery and run the fridge off that, while carrying the jump pack to start your car with if you ran the battery down too far.

 

[Moondancer]

The 1100 peak amps and 325 cold cranking amps are meaningless.  What we need to know is how many amp hours is the battery rated for?  And unfortunately, I can't find that info anywhere on their site, not even in the manual for it.

I do note that the whole thing only weighs 18 lbs, which means it has to have a pretty small battery in it.  A true deep cycle battery, which has 100 or so amp hours, would weigh about 60 lbs or more.

So no, I don't think this is going to do a very good job powering your fridge.

Now, you could maybe replace your engine battery with a marine/rv battery and run the fridge off that, while carrying the jump pack to start your car with if you ran the battery down too far.

This would be connected to a battery on the floor in the front seat area. I have an AGM battery.

 

[John61CT]

If you already have a large 12V AGM - for a efficient low-amps fridge I'd say 200+A with good charge sources - then what do you think the jump-starter's going to do for you?

 

[John61CT]

Those powerpaks usually have a SLA 18-22AH battery inside.

 

[Optimistic Paranoid]

This would be connected to a battery on the floor in the front seat area.  I have an AGM battery.

If I'm understanding you correctly, you are thinking of hooking the powerpack up to a larger battery so the charger in the powerpack can keep the big battery charged?

I can't see that working.  The charger in the powerpack will be sized small to keep it from overcharging the built in battery, and if you plug it in to a ciggarette lighter socket, the thin wires and low fuse on it will keep any real power from flowing.  In short, the big battery won't get recharged.

If this first mechanic won't/can't put a solenoid and FAT wires in for you, you need to finad another mechanic that will.  Admittedly, this is not something a regular mechanic is used to doing or understanding.  You might be better off finding a mechanic who's used to working on RVs.