Electricity while off grid

[Old Crow]

On the subject of trickle charging....

I believe the trickle-charging in post 15 refers to features of the D250SA and SMARTPASS.

On page four of the manual, this is how it's described for the D250SA:

"Trickle charging of the starter battery from a solar panel. The D250SA trickle charges the starter battery from a solar panel at intervals of 3 seconds if the service battery is fully charged."

On the other side of page four, under SMARTPASS 120, it's described like this:

"Starter battery trickle charging. The service battery trickle charges the starter battery without assistance from the solar panel or alternator to compensate for the self-discharge of the starter battery. The service battery charges in 3-second pulses when its voltage is higher that of the starter battery and the voltage of the starter battery is low."

-----

On the subject of start assistance from the SMARTPASS-controlled service (house) battery (from the same page of the manual).....

"Start assistance. SMARTPASS 120 automatically connects the service battery to the starter battery for 10 sec to assist, if the starter battery on its own is unable to start the engine. After the start assistance function has been activated, SMARTPASS 120 will display a fault indication until starting has been achieved without using the start assistance function."

.

 

[MidAtlantic]

Another case of me not having RTFM'd. I misunderstood what was meant by not one, but two things - jump starting and trickle charging. I thought of both in the 'conventional' sense, i.e. using another vehicle or battery pack to start the engine, and an AC trickle charger to keep both batteries topped up during storage. The ability to do both from within the truck/camper system was unknown to me and sounds pretty cool, but not sure for me it's worth the extra cost of the SMARTPASS. But, I suppose it might be to worthwhile to insure maximum bulk charging.

I have a single house AGM (don't know make and model) and 85W solar panel, and only run LEDs, a furnace (rarely) and Dometic CR-65 2-way compressor fridge (<2 Ah/h). We drive frequently on trips, but struggle to keep charged up, even in the desert. I was thinking of upgrading the Tacoma's alternator (tow-package 130A) , but am now convinced the CTEK option is a better option (not least because it avoids messing with the truck). I think I can live with the inability to program for specific batteries, and agree with Old Crow that lithium is a lot of money anyway, especially for the Battle Born.

The wire gauge discussion has been useful and interesting. Funny how it stirs up a lot of feeling and seems difficult to get and consensus on. I might upgrade mine (8-gauge, I think) when I install the CTEK gear, or do the experiment see if the charger alone solves my problem. Then I could add my 2 cents to the wire discussion!

Many thanks to you all.

 

[MidAtlantic]

I've been thinking of what it will take to live off grid in my NCO Alaskan camper. This is for emergencies only and I will not need any power for AC or heat. It will mostly be for charging electronics and 2 LED lights. I'm thinking of adding a 2nd battery under my truck hood and running power to the back for the camper. I believe I'm going have to get a bigger alternator and ISO cable.
Does anyone have this set up? Is it effective?
Any thoughts or advice would be greatly appreciated.
Thanks,
Joe

Sorry JoeKan. I seem to have hijacked your thread a bit.

To address you initial questions, I have a relatively simple system sold with the camper: one house battery charged by the truck's alternator and a small, 85W solar panel. A simple voltage-sensitive relay controls current flow between the truck and house batteries, a very cheap controller handles the flow from the solar panel, and a crude monitor shows the battery charge state. The price for this option was $525 in early 2015. I only run LED lights, the furnace fan, and a compressor refrigerator.

I have not been happy with the performance of my system, especially on spring trips in the desert with lots of driving, which should provide ample charging. This is why I am interested in discussions of alternator outputs, wire gauges, DC-DC chargers, MTTP controllers, etc. Unfortunately, answers to questions about power and electrical systems seem to get specific and technical very fast. It's just the nature of the beast. Fortunately, we're both lucky to have this forum and people who are willing to help and answer our questions.

FWIW I would agree that 'off-grid' living would probably warrant a solar panel, even if you only want power for LED lights and charging electronics, unless you drive often or are willing to run the engine to charge your battery. The down side is you will find yourself falling down the solar/electrical rabbit hole like I have. Unfortunately, there is no on-size-fits-all solution, so you will need to absorb a lot of information and differing advice.

But hey, what doesn't kill you makes you stronger, right?
Good luck!
.

 

[klahanie]

JoeKan, just to give an example...

My truck came from the factory with 2 batteries under the hood. The "extra" battery It is a simple design consisting of:

2nd battery tray
2nd battery (duplicate of battery #1)
battery cable connecting Batt2 pos to to Batt1 pos
battery cable connecting Batt2 neg to truck frame

Truck is a diesel, the second battery required for cold weather starting, I believe. Alternator charges both batteries exclusively.

If not needed for cold weather starting I could use the extra battery capacity to power lights in the cab, listen to radio, charge phone, etc. (people do this every day in their cars on their lunch breaks, quiet evenings with a friend etc.)

If I wanted to power that stuff while in the camper, I could run a cigarette plug extension cord from the truck into the camper, thru the slider windows. Have actually done this to power a fridge.

That's a simple system with 2 batteries. But I think most would add a disconnect or switch between the two batteries to separate them to prevent the main battery #1 from being discharged when running those lights etc with the motor off. The disconnect might be an ACR like mentioned post #7, a battery isolator, relay, solenoid, manual switch, plug or something else (?).

I posted before that I have previously used an inexpensive continuous duty solenoid, wired into to cable that connects the two batts. The coil (switch) is connected to an ignition hot, connects batts when motor running, separates when engine off. So you don't run your main battery flat while camping. [ON EDIT: Hook up the camper interior lights and outlets and ...]That's a simple dual battery system with separation.

* You should look into or ask about circuit protection (fuses) as well.*

To keep costs down, check if your truck model was available with a second underhood battery - to possibly source the tray. Or consider locating the second battery outside of the camper per Alaskan. But of course wire costs will be higher. Again, the battery is where you can spend a lot of money if you so choose. There are cheap batteries out there, perhaps even used. You did mention emergency use tho, so depends what you want.

 

[JoeKan]

Thanks everyone for the information. A lot to consider, maybe should go with a solar panel.

 

[MidAtlantic]

Just a few notes on the D250SA in case the info may be helpful to someone. I've been running one in my rig since October 2017 and am happy with it but I may not be the typical FWC user. I have a D250SA but I don't have the SMARTPASS. I'm only running a single battery and use it for LED lights and furnace only (I use a cooler for refrigeration). I don't use the solar-charging portion of it as I've not found it necessary. As far as control leads, I have the black one grounded to the frame to select a bulk charging voltage of 14.7 volts for the AGM battery. The voltage is temperature-compensated so when I say 14.7, what I actually see at, say, 45 degrees F, is voltage in the 15.0 range while my alternator is putting out 14.1 cold and mid 13's warm. The red lead isn't used as my Tundra doesn't have an ECU-controlled alternator. I only have 8-gauge wire running to it from the truck's starter battery (and a fuse in the positive line).

My Lifeline battery (GPL-31T) is eight years old and probably only capable of storing 80-some per cent of its original 105 amp-hour capacity at this point. Nevertheless, that has been enough for my modest needs. I drive (and therefore charge) daily, I don't run the furnace overnight, and I charge my electronics (GPS, Inreach, iPad, two phones, two cameras, dashcam, a laptop, and sometimes my brother's CPAP) in the truck. When the weather's warm enough I don't need to run the furnace, the battery is of course massive overkill for the short time I use an LED light or two (and I don't have a fan in my rooftop vent).

One downside of the D250SA is it doesn't have a LiFePO4 charging profile. I sometimes think I'd like to go to a LiFePO4 battery when the Lifeline finally can't handle the load. If I had to do that now, I'd probably be going with a Redarc BCDC1225D or similar DC-to-DC charger for it. But that's a lot of money by the time you add up the more expensive LiFePO4 battery and the charger and necessary gear. For my current needs, I'd probably be smarter to just replace the battery and let the D250SA keep it happy.


.

Thanks Old Crow. Finally about to make some purchases, so am re-reading everyone's helpful posts.

Like you I am going with the D250SA alone, at least for now. I think I can live without the Smartpass, despite its ability to deliver >20A during the bulk charging phase and to top up the truck battery when the house battery is fully charged. The current amazon price for the Smartpass is $278, so that is also a factor. (Why so much for what is apparently just a relay?) The Redarc althernative to the D250SA looks interesting, but it is quote a bit more expensive and like you I am probably more likely to just replace the batter if it dies than upgrade to lithium (which the CTEK charger does not support).

I will take Vic's and others advice and invest in a Trimetric TM2030 monitor, which is $153 from Northern Arizona Wind & Sun, and definitely replace the factory wiring to and from the truck battery with at least AWG 4 or 6. Still haven't decided if I need to go up (down?) to AWG 2. I'm not sure there will ever be a definitive answer to that one without doing the experiment, but people seem happy with the D250 and either 4 or 6.

Finally, for those reading about the CTEK D250, especially in pre-2017 posts here and elsewhere, note that the newer SA model can handle smart alternators out of the box. There is a lead that connects to the vehicle ignition circuit. The specs from the manual are below.

Conventional alternator cut-in
>13.1V, for 5 sec. (engine running, alternator charging)
Conventional alternator cut-out
<12.8V, for 10 sec. (engine running, alternator not charging) or service battery voltage > starter battery voltage

Smart alternator cut-in
>11.8V, for 5 sec. (engine running, alternator charging)
Smart alternator cut-out
<11.4V, for 10 sec. (engine running, alternator not charging) or service battery voltage > starter battery voltage

Thanks again to everybody for all the information and advice.

 

[rando]

A little late to the game here, but you can save a little hassle and cost. You either need to upgrade the factory wiring or install the DC-DC charger, not both. The DC-DC charger will boost the voltage at the camper battery and therefore compensate for any voltage drop in the wiring between the truck and the battery. So you don't need to update the truck-to-camper wiring as long as it is rated to carry the current the charger will draw. I think the 'stock' wiring is 10 awg, which is rated to carry 60A, so it will be fine for your 20A charger and even 12 awg would be fine:

https://www.bluesea.com/resources/96

Also, skip the Trimetric and get a Victron battery monitor. Once you add the shunt and cable to the Trimetric, you are at the same price as the Victron 'Smart' monitor BMV-712 which is more accurate, more modern and has many more features than the Trimetric.

 

[Vic Harder]

+1 to rando's suggestions. The Victron is better, and what I use. The Trimetric has been out there for a while, and was the best thing going for a long time.

To rando's point about not needing to upgrade the wiring, I would add:

1) if just using the CTEK unit, put it at the camper battery end of the wiring, not under the hood. That way it will compensate for the voltage drop from truck to camper

2) I wonder if just doing the wiring is enough on trucks with smart alternators? If it really does drop down to the low 12.x volt range while trying to charge. At 40-60A coming from my alternator I do see a .5 to .7v drop even over 2g wire.

 

[MidAtlantic]

A little late to the game here, but you can save a little hassle and cost. You either need to upgrade the factory wiring or install the DC-DC charger, not both. The DC-DC charger will boost the voltage at the camper battery and therefore compensate for any voltage drop in the wiring between the truck and the battery. So you don't need to update the truck-to-camper wiring as long as it is rated to carry the current the charger will draw. I think the 'stock' wiring is 10 awg, which is rated to carry 60A, so it will be fine for your 20A charger and even 12 awg would be fine:

https://www.bluesea.com/resources/96

Also, skip the Trimetric and get a Victron battery monitor. Once you add the shunt and cable to the Trimetric, you are at the same price as the Victron 'Smart' monitor BMV-712 which is more accurate, more modern and has many more features than the Trimetric.

Two good points, rando. You know, I had actually thought to be systematic and just change the wiring to see the effect, and only spend money on the charger if the problem wasn't solved. And funnily enough, I had realized not long after posting tha the Vitronic BMV-712 is a better choice than the Trimetric. It is only about $50 more and has Bluetooth/phone app capability, plus 10-m cable and shunt included.

 

[MidAtlantic]

+1 to rando's suggestions. The Victron is better, and what I use. The Trimetric has been out there for a while, and was the best thing going for a long time.

To rando's point about not needing to upgrade the wiring, I would add:

1) if just using the CTEK unit, put it at the camper battery end of the wiring, not under the hood. That way it will compensate for the voltage drop from truck to camper

2) I wonder if just doing the wiring is enough on trucks with smart alternators? If it really does drop down to the low 12.x volt range while trying to charge. At 40-60A coming from my alternator I do see a .5 to .7v drop even over 2g wire.

I will probably not be systematic and go ahead and change both the wiring and add the charger, because I have very limited time to work on the rig between uses (long story). And will definitely put the charger in the camper next to the battery, not under the hood.

Thanks everyone. I'm hopeful this will be the solution.

 

[pvstoy]

And if you have a terminal tool and the proper end terminal to match existing you can cut down the extra cat-communications cabling to make it a cleaner install. I only needed about 2 feet. Shortened a friends cable also.

Been pleased with the Victron BMV-712 monitor as you really need something to show you how much you have used and if you have reached 100 percent charge on the battery bank.

It will not tell you how much you have lost when the battery has been sitting for a month with nothing going in and out. Where as the resting voltage should give you a clue if you are low and need charging.

We often see many postings where the person is having problems with their system. Weather it is the battery is not holding charge to my solar is not keeping up and not working. "IF" they did have a battery monitor and understood the results it would go a long way in determining the cause of the problem.

Battery voltage alone does not tell you the whole story, as over time there are cumulative events draining a battery and you don't have a idea by how much. Or how much do I need to get back to 100%. Look at your voltage and put a draw like a water pump. The voltage will drop and show that I might be worried that it is showing a low voltage after use. But look at the battery monitor and you may have went from 95% to 92% capacity. And while it was running you can see how many amps are being taken away from the battery bank. Most of the time look at the volts and they may have come back up in value.

If you take away amps you need to put back the same plus more to get back to 100 percent. The smaller the battery bank the quicker the battery takes to get there. The bigger the battery bank the longer it takes and may require a bigger solar array, amps and watts to get the bank back to 100% in a solar day. A bigger multi battery bank is great to extend run times between charging but remember it takes more time to get it back to 100%

Before solving unknown problems with bigger battery banks and expensive wiring, etc. Maybe a battery monitor will help figure just exactly what the demand usage is or help track down a defective component in the system.

Ok soap box talk off, I got side tracked..... A battery monitor device is not for every one, nor will everybody have a perfect system without flaws. But they are a cool tool for figuring things out and keeping track of the ever demanding power demands.

Cheers

 

[larryqp]

I've been following this post and some others, about various off grid systems and may have missed this, so forgive me if I'm re-hashing. But if your system is setup to charge off the truck's alternator and let say its a cloudy day or you just had an unusual amp draw, (cold night with furnace running longer than usual), why not just either go for a short drive or run the truck for a short period. My alternator is rated at 140 amps, or something like that, so if the truck runs for 30 minutes, it would produce approximately 70amps.

My truck is much quieter than a generator, burning 30 minutes of gasoline is cheaper than the cost of a generator, no additional fuel to carry, and no additional weight. Am I missing something? This is assuming you have your system sized appropriately for sunny days and just run into an issue sporadically.

 

[MidAtlantic]

A little late to the game here, but you can save a little hassle and cost. You either need to upgrade the factory wiring or install the DC-DC charger, not both. The DC-DC charger will boost the voltage at the camper battery and therefore compensate for any voltage drop in the wiring between the truck and the battery. So you don't need to update the truck-to-camper wiring as long as it is rated to carry the current the charger will draw. I think the 'stock' wiring is 10 awg, which is rated to carry 60A, so it will be fine for your 20A charger and even 12 awg would be fine:

https://www.bluesea.com/resources/96

Also, skip the Trimetric and get a Victron battery monitor. Once you add the shunt and cable to the Trimetric, you are at the same price as the Victron 'Smart' monitor BMV-712 which is more accurate, more modern and has many more features than the Trimetric.

I think you are right - either change wiring or install charger - no need for both. The CTEK manual suggests only AGW10 from the alternator for 15' and AGW8 for 30'. Interestingly, for the Smartpass, which will take a lot more amperage form the alternator, it suggests AGW1 for both those distances. Another case of RTFM?

I will probably go with the charger, despite the cost, because it also gives me a much better MPPT solar controller to replace the crap $10 one that came with the camper.

 

[MidAtlantic]

I've been following this post and some others, about various off grid systems and may have missed this, so forgive me if I'm re-hashing. But if your system is setup to charge off the truck's alternator and let say its a cloudy day or you just had an unusual amp draw, (cold night with furnace running longer than usual), why not just either go for a short drive or run the truck for a short period. My alternator is rated at 140 amps, or something like that, so if the truck runs for 30 minutes, it would produce approximately 70amps.

My truck is much quieter than a generator, burning 30 minutes of gasoline is cheaper than the cost of a generator, no additional fuel to carry, and no additional weight. Am I missing something? This is assuming you have your system sized appropriately for sunny days and just run into an issue sporadically.

Indeed, how did it get so bloody complicated? JoeKan asks a simple question and it spirals out of control.

While kindly offering his advice to JoeKan, Vic happened to mention an issue with Toyota alternator outputs. I have a Tacoma with 130A alternator and have never been happy with its ability to charge the camper battery, even after driving all day, let alone the half hour that you propose. Vic suggested two main solutions to my problem (bigger wires and/or a DC-DC charger) and others have added good advice, including pvstoy's well-justified admonition to install a good battery monitor and learn to use it effectively.

So, thanks to everyone's input, I think I have a solution that will allow me to use the truck alternator exactly as you suggest. But, who ever said life was meant to be easy?

 

[klahanie]

why not just either go for a short drive or run the truck for a short period. My alternator is rated at 140 amps, or something like that, so if the truck runs for 30 minutes, it would produce approximately 70amps.

I've done this on occasion, having no solar of genny. A key point for us is our truck has a user switchable battery charge "logic" program that sets the rpm and alt output to aid in charging. No idea what the batts have gotten out of it, having no monitoring. But it has helped out when needed.

I see a few probs with the above assumption: Does alt truly output as stated. You'd want to run the motor continuously at the correct rpm for the alt to be at max output. You'd have to subtract whatever current the electric systems the truck needs to operate. At some point the alt will heat up and output will fall - likely sooner if the truck is stationary. Can that current be delivered to the battery. Can the battery absorb it - varies with battery state of charge.

It's a good theory but might be problematic in a campground (noise, no idle rule) and likely require longer time if driving (slow drive out to the highway). And funny thing is, we've "just gone for drive" and ended up not going back !

 

[MidAtlantic]

And if you have a terminal tool and the proper end terminal to match existing you can cut down the extra cat-communications cabling to make it a cleaner install. I only needed about 2 feet. Shortened a friends cable also.

Been pleased with the Victron BMV-712 monitor as you really need something to show you how much you have used and if you have reached 100 percent charge on the battery bank.


[snip]


Before solving unknown problems with bigger battery banks and expensive wiring, etc. Maybe a battery monitor will help figure just exactly what the demand usage is or help track down a defective component in the system.

Ok soap box talk off, I got side tracked..... A battery monitor device is not for every one, nor will everybody have a perfect system without flaws. But they are a cool tool for figuring things out and keeping track of the ever demanding power demands.

Cheers

The UTP data cable for the BMV-700 series has RJ12 connectors (see here). Victron actually sells a number of different lengths from 30 down to 0.3 m. (Too bad you don't get a choice with the unit.)

The soap box oration was much appreciated. I am definitely getting the monitor, so in my case it might have been preaching to the converted, as they say over here.

 

[JaSAn]

A couple of cautions on using your vehicle's alternator for house battery charging:

• An automotive alternator is designed to expect airflow from a moving vehicle. Underhood temperatures rise quickly when a vehicle is stationary; alternator output drops and life is shortened. Opening the hood will help.
• Optimal battery charge rate is .2C = 20A per 100AH of battery (below 113ºF). Higher rates increase battery resistance = heat = shortened battery life.
• A lead acid battery will take a minimum of 2 hours to get from 80% to 100% no matter how many amps you try to push into it.

 

[Vic Harder]

A couple of cautions on using your vehicle's alternator for house battery charging:

• An automotive alternator is designed to expect airflow from a moving vehicle. Underhood temperatures rise quickly when a vehicle is stationary; alternator output drops and life is shortened. Opening the hood will help.
• Optimal battery charge rate is .2C = 20A per 100AH of battery (below 113ºF). Higher rates increase battery resistance = heat = shortened battery life.
• A lead acid battery will take a minimum of 2 hours to get from 80% to 100% no matter how many amps you try to push into it.

I'd agree with all of this based on my own experience. I have lots of gauges and such, and can see that when my 250AH batteries are at 75 to 80% they will be getting 40-80A from the alternator. 25% down on 250AH = 62.5AH. So they should easily be fully charged in two hours of charge, right? Nope. The current drops as the batteries charge up, and with 5% or so to go, only 3-4A is flowing over the wires. I usually punch the remote switch on the ACR to kill the connection at that point and let the Victron solar controller figure out when the batteries are really fully charged. The Victron has smarts that my alternator has no way of knowing.

And even if I had a "smart" alternator, it would not really know what to do with another battery hanging off of a wire 20' away.

In short: Idling your truck for 30 minutes isn't going to do much. And without a BMV, you have no idea what it does do.

 

[pvstoy]

And as angry Bob, as some call him has said... You can use a generator ( or truck alternator) to put a charge back but turn it off when you reach 90 percent. anything after that if on generator or idling your truck is wasting gas.

That is when a battery monitor comes in handy to know when to run such a device and when to turn it off.

Your alternator may be pushing a high amp number at the battery but that may not be what is actually going into the battery as different types of battery's will have different acceptance of what is being pushed to it.

 

[klahanie]

Re alternator charging in camp. I thought the idea was used as an occasional option, as in, "say its a cloudy day or you just had an unusual amp draw".

The Bulk (constant current) part of charging is efficient, going from 50% to say 70% soc. I think the alt could be useful if "needed" to keep the battery above an undesired DOD.

.2C might be common for some batts. Some agms spec .4C. I had some agms that could take 1C, for a period.

Pity the poor, unloved vehicle alternator. Imagine jumping in your car to run an errand. You start the motor, crank up the defrost and heat (or aircon), turn on some tunes, drive for 10 mins. Same again for the return. Next day the car still starts fine (!). I don't doubt people do these start/stop, short runs all the time. The alternator does provide a charge, year after year.

Ultimate charging ?, no. Get the rated output ?, prob not. At idle ?, nope. But, done right, it might give 10, 20, or more AHs. And that might be enough to help the batts longevity and keep the camper camping, another day.