3 batteries -to which one do I wire the fridge?

[WalkaboutTed]

So... I've searched for this info but cannot find an answer.

My truckfridge 130 arrives tomorrow.  I'm connecting it directly the batteries (3x100ah group 27). #1 battery has the input from the alternator/solar. #3 battery has the 1100 watt inverter connected to it. #2 will be connected to the charger every couple of weeks when we have shore power.  

Two questions:  are those the correct connections? And second, which battery to wire to the fridge? I will have a disconnect switch between batteries and the fridge, but I don't want to turn off the fridge overnight while doing a multiple hour charge.

Once again, thank you for your help,
Ted

 

[Weight]

Most common; Vehicle has separate starter battery. There is a house battery to power the fridge, inverter, and other living area stuff. All available charging systems connect to this house battery. Sometimes with a combiner from/to the starter battery. So, I don't understand your 3 separate battery system. I would connect my 12 volt fridge to the battery with the most charging stuff connected, as this one will have the best chance of keeping the beer cold.

 

[SternWake]

What works, and what is ideal can often be very different things. Your system will work.

Ideally all loads and charging sources would tap the + of battery one and would tap the - of battery 3.

Yes there becomes issues when there are more than 3 or 4 ring terminals stacked atop each other.

Whether 6v batteries are in series or 12v batteries are in parallel, i think it best to view it as one big battery in separate pieces. It does seem to be a waste only having one cable connector stacked on the middle battery, and would appear to be little difference in performance, but when power or chargign sources are not run through all batteries, but attached to only one, then than one battery takes more of the charging or supports more of the load, and wears out faster, causing bank imbalances, which then degrades the whole bank faster



So I would recommend wiring the truckfridge( and all loads and charging sources) with the (+) to battery one and the (-) to battery 3, using 10AWG or 12AWG(truckfridge), certainly no thinner, and putting a fuse on the (+) within 7 inches of the (+) terminal.

 

[WalkaboutTed]

To Weight:
My starting battery is separate, the three batteries mentioned make up my auxiliary battery bank. I should have explained better.

To Sternwake:
Per your recommendation in another post, I do have the ground going from #3 battery. But then your answer brings me to one more question.

I was planning to ground the fridge to the chassis about a foot from the fridge, where I have a ground block consolidating other wire runs. Are you saying that it's better to run the negative wire back from the fridge to ground directly to battery #3?

 

[Almost There]

So... I've searched for this info but cannot find an answer.

My truckfridge 130 arrives tomorrow.  I'm connecting it directly the batteries (3x100ah group 27). #1 battery has the input from the alternator/solar. #3 battery has the 1100 watt inverter connected to it. #2 will be connected to the charger every couple of weeks when we have shore power.  

Two questions:  are those the correct connections? And second, which battery to wire to the fridge? I will have a disconnect switch between batteries and the fridge, but I don't want to turn off the fridge overnight while doing a multiple hour charge.

Once again, thank you for your help,
Ted

If I'm reading the above correctly, I have more questions than answers! Maybe its just the sentence that is confusing and you do have all 3 batteries hooked together but that's not the way I'm reading it.

Are you planning 3 separate battery systems and if so, how are you planning on charging the #3 battery? You show solar alternator charging to #1 only and only charging # 2 once every couple of weeks - which won't let you use that battery every day.

All 3 batteries need to be wired together so that you have use of all three at any one point in time. Think of all 3 wired together as being one big battery, not 3 smaller ones. It works the same as a flashlight where you have more than one battery in there, power is drawn from all three simultaneously, not one or the other. You'll have access to 300 amp hours (usable 150 amp hours) as opposed to 3 separate battery systems with only 50 amp hours available from any single one (when each battery is full).

Multiple sources of charging won't confuse anything. Both the alternator and the solar will charge all three simultaneously as will shore power (with a battery charger) when you're hooked up to it.

The fridge could either be wired directly to the battery bank with a fuse near the battery or to a fuse bank set up to handle all your 12 v needs. You will have other things that need 12V like lights, outlets for charging phones etc.

Because we all end up with multiple wires attached to the one positive post of a battery and the same thing at the negative post of the  3rd battery, it is possible to do one of 2 things - use a buss bar (think of it like a power bar strip - multiple outlets) or simply put half the terminal lugs on one side of the post and half on the other, thereby cutting down on the number of lugs stacked up.

Also, why do you think that the fridge would have to be turned off while you're charging the battery(ies)?

 

[WalkaboutTed]

Boy, I guess I'm striking out on describing my system properly. The three batteries are my battery bank, all wired in parallel. I have the alternator and the solar going into my CTEK d250s with Smartpass which then has one output going into #1 battery.

My original worry, which was silly, is that I don't want to cause any surge or drain that might make the fridge unhappy. I was thinking that if I connected the fridge to battery #1 that any surge of power coming from the alternator /solar might bother the fridge. And then, I was concerned that if I connected the fridge to #3 battery , to which the inverter is connected, that a sudden, big drain on that battery (my coffeemaker or ricemaker) might bother the fridge too. And then, I was concerned that, since I was going to connect my charger to #2 battery, along with the fridge, that the input from the charger would cause a disturbing surge on the fridge.

I was overthinking it. For some reason, I supposed that I shouldn't have more than one item on each battery. And per Sternwake, all of that is now a moot point.

Oh, and I am planning to put a 15 amp inline (15 amp is what Truckfridge recommended) fuse right next to the battery on a 10 awg wire.

That leaves my new question. Right by the fridge, I have a bussbar with grounds coming in so as to reduce 9 ground wires having to go back to the battery bank. That bussbar is then grounded to the chassis. (I am aware that set up may cause a ground loop, but that was a separate thread). Can I ground the fridge there, or must I run the negative for the fridge back to the battery ground?

Hoo! Now I've confused myself.

 

[SternWake]

As far as grounding the fridge to a Nearby ground Buss, this will certainly work.

But,

What I feel I must point out, is that Danfoss, the maker of the fridge's compressor and compressor controller, says to not share busses with other devices, but to wire directly to battery terminals.

http://files.danfoss.com/TechnicalI...nit_101n0600_12-24vdc_08-2011_dehc100m602.pdf

The reasons they say this, are:
1: Voltage drop.  If there are other loads sharing the busses, they will drop the voltage along the wiring to and from the shared buss, reducing the voltage the compressor controller gets.  This only really becomes an issue when the batteries are low, or the wiring is too thin to and from the Buss, and or the load on the other circuits that share the buss are quite high, like an inverter powering a microwave, or an electric coffee maker.

2:  When some electrical loads are turned off, there can be a voltage spike that is transmitted through out all the wiring back to the battery, which kind of acts like a big electrical filter.

So if the fridge is wired directly to the battery, there is a large reduction in the possible negative Effects of both 1 and 2.

NOw wiring to battery posts themselves is 'ideal', but many many perhaps most 12v compressor fridges are NOT wired like this, and work properly the whole time.  Mine is One not meeting the ideal criteria, as I have my fridge ground wire sharing a Buss on my Shunt( for battery monitor), and the positive is shared with the Buss to my fuse block, which also powers both inverters.

So, you can choose to attempt 'ideal', or not.  The risk of consequence is likely very small.  I just don;t want to be on the record saying to ignore the instructions from the  fridge's compressor maker, even though experience and evidence says it is not really a factor.

Right now, I only have the one battery, used for fridge and starter motor, and they share that ground buss at the shunt, and the starter motor is most likely to send the biggest voltage spikes through out the shared wiring, and My fridge continued to operate very well, and in June it will be like this for 2 years that the same Buss always shares the engine starter and fridge, and in October the fridge will be 5 years old and running continuously at least 50 weeks a year.

 

[John61CT]

OK, so what sounded like 3 separate batteries are all hooked together in parallel - hopefully with nice big fat properly crimped wires of equal lengths, and pos = neg lengths.

In other words you have one big House battery.

3x100ah group 27
...
#1 battery has the input from the alternator/solar. #3 battery has the 1100 watt inverter connected to it. #2 will be connected to the charger every couple of weeks when we have shore power.

What batteries specifically, and why did you choose those?

Your solar, inverter and shore charger are all connected to your one big House battery, let's call all that circuit B.

How about the vehicle loads, essential to driving? Ignition, starter, running lights etc, GPS, any monitoring/safety gear. . .

They should usually/ideally be on a completely separate circuit A, along with the starter battery.

you spent $500 on a very nice pair of Swedish gizmos, that Dual DCDC + SmartPass should take care of most of your issues, if you read the manual and follow their instructions, with some q&a input here.

Have you got circuit A on the left side post of your SmartPass marked with an Alt symbol, and circuit B on the right, labelled with a battery?

Your fridge should go, along with other "non-essential" loads, up to 80A total, on the bottom right LVD post of the SmartPass, labelled with a light bulb.

All your grounds should go to a central ground buss, also attached to the chassis and **both** ground posts on the Dual DCDC and SmartPass.

All with proper wiring as above.

 

[MrNoodly]

Ideally all loads and charging sources would tap the + of battery one and would tap the - of battery 3.

I have two 12V batteries. The charging lines go the + on number one and - on number two. The loads connect to the opposite terminals: + on number two, - on number one. And, of course, I have big ass cables going + to + and - to -.

 

[WalkaboutTed]

John, to answer/respond to your questions and recommendations :

I chose group 27 batteries (all with equally sized cables from genuinedealz .com), essentially since I didn't know any better. I had been abusing the heck out of a Costco marine battery for a couple of years while camping and it kept coming back from the dead. So I figured that three UPG group 27 batteries would be good enough. I'm sure that they'll be fine, but now with a little more knowledge, I wish I had bought golf cart 6volt batteries. Especially since we're going to be running more of a load then I had originally planned (i.e., fridge, laptops, tv, cell booster, etc.). We'll be on walkabout for several years, so I plan on using them without too much worry about giving them TLC. If I manage to kill them (I'm the battery forewoman), we'll replace them with four 6 volt golf cart batteries.

The engine battery will handle all the loads you mentioned. Our van has a 400 watt inverter built in and Nissan meant the battery to be well used so they put in an "80ah" marine battery (though we know that marine batteries do not behave like true deep cycle batteries and "amp hours" is not an appropriate description). We will run that battery without too much concern as the CTEK system also charges the engine battery from the solar. In any case we'll carry one of those jump packs in case we drain both systems. If we trash the engine battery, we'll replace it with a deep cycle. The adage here on CRVL is that newbies destroy their first set of batteries anyway. So if I do that by benign neglect I won't be heartbroken. Hubby and I have decided that we'll take reasonable care of the batteries, but we won't do without our pleasures. Oh! 11.9 volts! Ahhh-let's watch some more tv!

I was planning to hook up the fridge on the CTEK "non-essential" load post like you recommended, but the truckfridge installation instructions are adamant about connecting the fridge directly to battery. Also, that post runs the max of 10 amps and truckfridge says up to 15 amps. So I have an extra beautiful stainless marine 12 volt outlet connected to that "non-essential" post with 10 awg wire. Now I can use it for some other heavy 12v load.

As far as bringing all the grounds back to a central ground, that would have been worse than a bucket of spaghetti as we have a total of 26 ground wires (no, you don't want to ask about my system-we'll just say that I don't like extension cords and I want different types of outlets and lights and other goodies wherever I might ever possibly want them). I researched about it and then got final dispensation by Sternwake for more than one ground buss. I just have to be aware that I have a splendid ground loop and will be having to use ground loop isolators. In any case, everything works.

But, to be on the safe side, I will run the the fridge ground back to the battery. For a $700 item, I prefer not to intentionally neglect that to death.

I think I covered it all. I wouldn't have been able to do all this without all the help from this board and a sailboat electric book. I knew I should be fine when I started dreaming about wire gauges (true).
Ted

 

[John61CT]

So I figured that three UPG group 27 batteries would be good enough. I'm sure that they'll be fine, but now with a little more knowledge, I wish I had bought golf cart 6volt batteries.

S'done is done, if you find someone with major starting needs before they get too beat up, maybe recoup some and replace, going to have to anyway likely a year or two max.

We will run that battery without too much concern as the CTEK system also charges the engine battery from the solar. In any case we'll carry one of those jump packs in case we drain both systems. If we trash the engine battery, we'll replace it with a deep cycle.

Good idea. Just know with solar CTEK, nothing goes to the left side (usually starter) until right/house is full.

Look in the manual example where big house is on the left, fed directly by the Alt, starter is the one fed only by the Dual when charge is under 20 A. Worth considering.

I was planning to hook up the fridge on the CTEK "non-essential" load post like you recommended, but the truckfridge installation instructions are adamant about connecting the fridge directly to battery. Also, that post runs the max of 10 amps and truckfridge says up to 15 amps.

Doesn't mean you must obey, really good wiring will let anything go anywhere, long as you're within specs, maybe get a sparky to verify with meters if you're unsure.

And of course you could get a variable-setpoint LVD just for the fridge, but you already paid a fair bit for the one in that SmartPass.

final dispensation by Sternwake for more than one ground buss. I just have to be aware that I have a splendid ground loop and will be having to use ground loop isolators. In any case, everything works.

But, to be on the safe side, I will run the the fridge ground back to the battery. For a $700 item, I prefer not to intentionally neglect that to death.

You're good then, bigger the amps the more critical solid grounding, the little stuff won't (usually) burn the house down.