Which system for reliability?

[Unsettled]

I plan to run a low watt system (laptop, small 12v portable fridge, USB small fan, and LED lantern), maybe 150+ watts max draw? (Maybe 4G booster also.)

This is for a Dodge Grand Caravan.  It's important to me to not to be stuck without power.  I'm assuming 200 watts of solar -but maybe I can fit 300? 

1.   200 Ah 12v AGM battery connected with a smart isolator plus solar:  it seems that with moderate driving the battery should stay topped up?

2.  Dual System:  Solar feeds a lithium 12v. 50 or 100 Ah battery in the back.  In the front, have a separate system with 100 Ah AGM connected with isolator.  Swap out the appliances between the two depending on which battery has more charge.  (Or split the appliances between the systems.) Complicated, I know, and maybe I'm overthinking this, but it seems more reliable to me since I'd still be getting power even if one system has issues. 

Any thoughts on which system is more practical or could be configured better?

 

[Uncle Todo]

I'd say the 1st one, 2 is getting overly complex and taking up valuable space.
Yep, the isolator will keep the secondary battery charged while driving.

Also, if you wanted to add LiFePO4 to 1, I came across a battery isolator made to work with lithium secondary batteries and charges them so you wouldn't need a separate charger.
https://www.amazon.com/Battle-Born-Batteries-Lithium-Isolation/dp/B07DY8S815

I'm still fumbling around with this myself for my van, so many options, decisions, specs & numbers to consider!

 

[DLTooley]

Solenoids are generally preferred over isolators. All lead acid batteries have a long charge tail where it takes a long time at low charge rates to top off. Solar is better for that.

Do realize you will never get the wattage rating of a panel.

I don’t think agm is worth it, but some people swear by them. LiFePo4 battery markets are evolving, there are now power stations equipped with those batteries. Including one in your system might well provide the hybrid functionality you are considering.

Pass through charging, use while charging, is a feature to consider. The simplest solution might be just to charge a power station while driving.

With their various outputs power stations can also simplify design and wiring. I used to recommend only going to about 500wh on a value basis, but that market too is evolving. Price on the bigger models is dropping and they have higher capacity inverters.

Go for the three hundred watts if you can fit it. A good controller/bms system will help with your education regarding real world charge and load. I use a Victron controller which has a smartphone Bluetooth display.

Multiple controllers is a good option in a more complex, or growing, system. Your description on that isn’t specific.

Start simple!

 

[Spaceman Spiff]

I plan to run a low watt system (laptop, small 12v portable fridge, USB small fan, and LED lantern), maybe 150+ watts max draw?  (Maybe 4G booster also.) . . .
Any thoughts on which system is more practical or could be configured better?

My 2¢:

 - 200W solar (minimum)
 - MPPT solar controller
 - 100AH usable battery power (LiFePO4, if budget allows)
 - DC-DC charger (instead of isolator)
 - Amp counting battery monitor

I run more than you plan on 200W solar and 208AH (104 usable) GC2s.

DC-DC charger gives better control of charging house battery, especially if the starter battery chemistry is different.

 

[Unsettled]

Pass through charging, use while charging, is a feature to consider. The simplest solution might be just to charge a power station while driving.

Which battery systems are not pass-through?

 

[bullfrog]

Your idea of small isn’t small when you had a refrigerator and a laptop as well as a fan and lights. Do realize on winter cloudy days you will have to drive up to 4 or more hours to charge you batteries. Your system is it’s limit of what it can do on sunny days. An AGM battery isn’t going to last being discharged below 50% continuously. Due to the space limitations I would recommend lithium batteries even though I use AGMs because I have lots of room. I have a tilt able 305 watt panel with MPPT controller just to be sure I can maintain 150 to 200 watts of charging on winter sunny days, on cloudy days I use a small generator for a few hours first thing in the morning and last thing at night if not fully charged. I do not use the vehicle or it’s battery for the household power needs because I want to know the vehicle will start and while running will not put extra wear on the components. This is just my way and my opinion.

 

[Unsettled]

My 2¢:

 - 200W solar (minimum)
 - MPPT solar controller
 - 100AH usable battery power (LiFePO4, if budget allows)
 - DC-DC charger (instead of isolator)
 - Amp counting battery monitor

I run more than you plan on 200W solar and 208AH (104 usable) GC2s.

DC-DC charger gives better control of charging house battery, especially if the starter battery chemistry is different.

I'll consider this.  I'd rather use lithium.  I just thought I could charge the AGM faster (less driving) with an isolator than from a lithium with a DC-DC charger.  I notice those go from 20 to 40 to 60 amps.  Is there any reason not to go with the 60 amp?

But regardless, this actually makes the most sense and works on my budget, set at around $1500 -or more if need be.  I'll probably also pay an automotive electrician to hook up the DC to DC and check the rest of my system over, just for safety's sake.

 

[Unsettled]

Your idea of small isn’t small when you had a refrigerator and a laptop as well as a fan and lights. Do realize on winter cloudy days you will have to drive up to 4 or more hours to charge you batteries. Your system is it’s limit of what it can do on sunny days. An AGM battery isn’t going to last being discharged below 50% continuously. Due to the space limitations I would recommend lithium batteries even though I use AGMs because I have lots of room. I have a tilt able 305 watt panel with MPPT controller just to be sure I can maintain 150 to 200 watts of charging on winter sunny days, on cloudy days I use a small generator for a few hours first thing in the morning and last thing at night if not fully charged. I do not use the vehicle or it’s battery for the household power needs because I want to know the vehicle will start and while running will not put extra wear on the components. This is just my way and my opinion.

Thanks, yeah, I might be underestimating my requirement and overestimating what can be generated.  I don't want to be driving around needlessly or carrying a generator.  I'm doing side vents so I'll see how much solar I can pack onto the roof and go for max.

 

[Unsettled]

I thought it was overboard, but now I'm thinking I should do the DC to DC with li-po, max out the solar on the roof, and carry a 200 watt foldable panel to supplement it when I'm stationary for a long time. I definitely do not like going without power. Also I forgot, I like to vape and I'm not sure what that draws but I can go through a small powerbank in a day pretty easily with it. Anyway, thanks for the reality check folks. I've got the funds so I'm gonna go whole-hog on the system now.

Just one more question for you guys. Is there some reason I should go for a 200ah Li-Po battery or is 100ah sufficient?

 

[Uncle Todo]

I joined a DIY solar forum about the same time as I joined here. From my understanding with a DC-DC charger, you need to size one to your alternator as well.
If it's pushing 60a into your house battery, then it's sucking 60a from your alternator so you may have a short lived alternator.

I just bought a higher output alternator, was going to put in today but decided to enjoy the seasons first snow fall instead!

 

[maki2]

This winter in Quartzsite I am using a 150 watt panel and a 160ah AGM deep cycle marine battery. Running ntrictly off of solar, no charging from my car, I can run my small 17 liter Engel fridge/freezer, use my laptop during the sunlight hours, keep my tablet and cell phone charged. Use my inkjet printer. Spend several hours running my vinyl cutter too. Often in the mornings or evenings I also run my diesel heater/ cooktop. That uses some 12v electricity to light the glow plug to ignite the diesel fuel and also to run the blower fan which is always on when that heater/ stove is on.

You just plan it out, keep a reserve for nightime and early morning and do the computer stuff during peak sunlight hours. Use the tablet and cell phone whenever but charge all your devices during peak sunlight hourrs. I have rechargeable LED lights and also a bunch of rechargeable AAA and AA batteries   I just have a routine of plugging them in to recharge in the morning and afternoon to keep those items charged. I have lots of 12v outlets and USB outlets installed. That makes it easy to plug things in for charging during the peak solar hours.  I am not trying to run power hungry 120v appliances so I do not need a large inverter. No TV running at night. You can have a lot but just dont do it all after dark, do your extra power use work while the sun is bringing in the electricity.

 

[MotorVation]

Here's some real world info. I'm travelling, it's almost 1pm, I have 590 watts of panels. It's cloudy. I'm pulling in 42 watts. The clouds may break this afternoon but if not, I have 200 AH of lithium which will get me through till tomorrow. I don't have any other way to charge the batteries except for a small generator. There will be days like this...

 

[maki2]

Reminder, the original person who made this request is living out of a minivan. Not much space in or on it.

 

[MotorVation]

I was trying to make 2 points. There are days when there's a thick cloud cover and there's not much power to be had from the sun, even with a lot of panels. The other is that it's a real good idea to have other ways to charge the batteries. I'm travelling right now and sleeping in truck stops. It's not practical to run a portable generator. It's a really good idea to be able to charge from the alternator while driving. I didn't rig that up and should have. 

I was just waking up when I wrote the other post. I should have been more specific. I have an extended van and I didn't go with a roof vent/fan to make room for larger panels

 

[Camper]

Along the lines of reliablilty, I'm looking for ideas on 12-volt outlets, usb charging ports and LED lights for my van.

 

[MotorVation]

Bein' that I'm currently stuck on the side of the road in Mississippi mud waiting for AAA, I feel like too much of a dumb ass to offer any more tidbits of wisdom    :s

 

[bullfrog]

Welcome to my world a few days ago except no AAA out here!

 

[Unsettled]

Lots of different thinking and real-world realities to consider. A second alternator sounds pricey to install but it may be worth the dough to get reliable power 24/7. I'll be running a laptop at night quite a lot and a small USB fan. Maybe the way to go is to buy a more efficient laptop, like one of those Surface Go machines or the like. If you put on some magnified reading glasses, it's just like viewing normal screen. I'm also gonna go with a smaller fridge that draws fewer watts.

USB fan = 2.5 watts
LED lantern = 10 watts
Surface Go = 24 watts
Total = 36.5

16 Liter fridge = 45 watts (non-continuous)
Vape pen = 11 watts (non-continuous)
Phone charging = 4 watts (non-continous)
Total = 60

Altogether it's about 100 watts but probably significantly lower since the fridge doesn't run all the time. Also, it might be nice to crank up a proper laptop at 45 watts, but that added wattage would still keep me around 100 watts? I'm not sure cuz there're a lot of variables, like what I'd doing on the computer at any particular time and how often the fridge is kicking in and how much I'm vaping.

Maybe the way the way to go is the low amp DC to DC and 200ah LiPo to get me through days when the sun isn't out.

Or my original idea of a second system in front with a lead acid connected to the battery with an isolator that I can turn on when needed and get high amp charging to get me through in a pinch. That could run maybe the fridge and other stuff and it wouldn't be hard to swap out appliances as needed from the 100ah LiPo on pure solar in the back. Some people said this wasn't smart but I still think it has merit. As far as taking up space goes, it would jsut be a battery box on the floor of the passengers side with an inverter velcroed to it, space I'm not using anyway.

I'm not doing any of this until I get back to the US this summer anyway. I just like thinking about it for some reason But that's all "theoretical engineering" so I really appreciate all the real-world limitations members are discussing.

 

[Spaceman Spiff]

Lots of different thinking and real-world realities to consider.  A second alternator sounds pricey to install but it may be worth the dough to get reliable power 24/7.  I'll be running a laptop at night quite a lot and a small USB fan . . .

USB fan = 2.5 watts (seems high, max power for USB 2.0 = 2.5W , too much for USB 1.0)
LED lantern = 10 watts
Surface Go = 24 watts (max watts or average?)
Total = 36.5

16 Liter fridge = 45 watts (non-continuous)
my fridge runs about 30% of the time at 70º ambient, 50% at 90º
Vape pen = 11 watts (non-continuous) how long to charge?
Phone charging = 4 watts (non-continous) [font=Tahoma, Verdana, Arial, sans-serif]how long to charge?[/font]
Total = 60

 . . . I'm not sure cuz there're a lot of variables, like what I'd doing on the computer at any particular time and how often the fridge is kicking in and how much I'm vaping. That is why you measure your normal usage

The metric you want is watt-hours not watts.  How many hours are you running your laptop? fan? lights?  Since you have time, get a Kill-A-Watt meter and measure how much your laptop, vape pen, phone, et.al. actually uses in a day.

The best way to determine your need for power is to build a power budget:
 - add up all the power requirements for a day (watt-hours or amp-hours).
 - multiply by how many days you want to go without adequate power input.
= how much usable battery you need.
 - multiply by 2 to get the minimum solar you need (to rely only on solar).

Start there.  Then you can play around with how often/how much other charging sources are needed and iterate until you are satisfied.