Solar vs Generator & Alternator

[zombiedude1]

First post! Sorry for the long topic, just wanted to explain the situation in detail for an accurate answer.

I'll be living in my van soon to save/invest money while I continue to work full time for the next 2-4 years. I've fully insulated my van in effort to not have to run the A/C very often.
I will be driving no less than 1 hour per day, will this be sufficient enough to restore my battery bank if driven off the alternator, or an additional alternator?
I will run the generator approx. 1 hour per day for microwave usage & a/c usage.

If possible, the best outcome would to be able to supply enough energy per day from my generator and alternator, as it would save the cash on solar.

My energy usage plans: Laptop/phone charging, occasional xbox360/tv, wifi, interior lighting (small led lighting), speakers, rare a/c use for under 1hr max. (Primarily at night after work)
Total estimated energy usage per day: 500-1,200watts. (Less usage on weekdays, more on weekends)

Major Appliances
1x 4kw Generator (To charge battery & run high-energy applications based upon need -- mounted in custom roof cover/box)
1x 5,000 BTU Window Air Conditioner (500-600W -- mounted in custom roof cover/box)
1x 1,250W Microwave (Only used with generator)
1x Propane Mini-Fridge (Seems to be more energy-efficient than using electricity 24/7?)

Energy Plans W/Solar
4x 12v 100ah AGM battery bank [ 400AH Total ]
2x 250W Solar Panels [ 500W Total ]
1x 1kw Inverter
1x 50A 12v Solar Panel Charger/ Controller

For 50% max usage with a 400AH bank, I will have 2.4 kw/h of energy usage available on a full bank.
My solar panels will be able to charge my bank from 50% to 99% in approximately 1-2 days if weather permits, correct?

Q1: Are solar panels worth purchasing, or will I be able to generate enough electricity with my standard alternator or an additional alternator + my generator? recommendation?
Q2: If I'm able to get by without solar, what would be the best way to setup charging through my alternator &/or my generator (when it is running)? I have very limited electricity knowledge.
Q3: If solar is a requirement for my power demands, is 500W overkill or sufficient?


Thank you in advance!

[SunEagle]

Hello zombiedude1 and welcome to Solar Panel Talk

To answer your questions I would say with your current major appliances and usage the generator and alternator would financially be your best way to charge a battery system batteries.

But I see two issues with what you propose.

1) Wiring 4 x 12v 100Ah batteries in parallel will more than likely kill one of them quicker that the stated life span and cycle rate. That is due to uneven charging and discharging of a parallel battery system.

2) The second issue is that most batteries will not last very long using 50% of their capacity and not charging them back up to 100% each time you use them. Letting them stay at a lower % SOC ends up sulfating the plates and again killing it off.

If you decide to build a 400Ah 12v battery system then 500 watts of panels and an MPPT CC is the correct balance. That 500watt with an MPPT will provide 41 amps of charging at 12volts which is in the sweet spot of C/10 for that size battery system. Going with less wattage will certainly generate charging amps that are much too little to keep the battery happy.

[sensij]

If you decide to build a 400Ah 12v battery system then 500 watts of panels and an MPPT CC is the correct balance. That 500watt with an MPPT will provide 41 amps of charging at 12volts which is in the sweet spot of C/10 for that size battery system. Going with less wattage will certainly generate charging amps that are much too little to keep the battery happy.

These are AGM batteries, not FLA. Sweet spot for charge current is probably more like C/5 - C/3.

500 W will not produce 41 A of charge current for any amount of time to be meaningful, and maybe never. It is important to design the system to handle *spikes* of current at STC conditions, or even higher in some locations, but for battery planning purposes, a maximum charge current of 30 A is probably going to be more typical, maybe less depending on how the panels are mounted.

OP needs to look into a battery isolator to properly charge from the alternator. Here is an overview:

http://all-about-lead-acid-batteries...solators-work/

[SunEagle]

These are AGM batteries, not FLA. Sweet spot for charge current is probably more like C/5 - C/3.

500 W will not produce 41 A of charge current for any amount of time to be meaningful, and maybe never. It is important to design the system to handle *spikes* of current at STC conditions, or even higher in some locations, but for battery planning purposes, a maximum charge current of 30 A is probably going to be more typical, maybe less depending on how the panels are mounted.

OP needs to look into a battery isolator to properly charge from the alternator. Here is an overview:

http://all-about-lead-acid-batteries...solators-work/

Ah. Sorry I missed the fact that those were AGM type. Thanks for the correction.

You are also correct that with 500 watts of panels that 41 charging amps will be limited in time duration depending on the location and direction the panels are pointed.

So even 500 watts would not truly be enough to charge the batteries daily and using a generator or alternator would be a better action plan.

[zombiedude1]

Thank you for your responses, I highly appreciate the shared knowledge.

Sun, So, if having 4 AGM batteries in parallel will cause an uneven discharge rate killing them faster, what would be the preferred setup for a 12v 400ah (est.) battery bank?
sensij Thanks for the reading material, I will educate myself after work today on battery isolators & ask any questions I may have afterwards on this topic.

I'll definitely just charge on my alternator & generator if I'm able to. So I run a battery isolator for the alternator charging when driving.
What method should I use for charging the battery bank from the generator while it's running? An automatic battery charger plugged into the AC outlet, what amp rate?
Or is there a better method?

EDIT: Short read, so I read it. Very simple and clear.

[SunEagle]

If you need a 400Ah 12v battery system you can build it with 6 x 2v 400Ah batteries wired in series.

Also the lower voltage high Ah rated batteries are easier to move then a 12V 100Ah battery.

I have a 12V 232Ah battery system in my RV which consists of 2 x 6v 232Ah batteries wired in series. Using 12v batteries to build a 232Ah system would be crazy big and heavy.

[Sunking]

Sun, So, if having 4 AGM batteries in parallel will cause an uneven discharge rate killing them faster, what would be the preferred setup for a 12v 400ah (est.) battery bank?

Your batteries will be dead in a year. Prallel batteries are fine for Emergency Stand By Power, not worth a darn in a daily cycle application.

FWIW one hour of engine run time will generate more energy than a van loaded with panels can generate in a day or two. All the panels will do is supplement. If you are going to use panels, run the engine early morning, then let the panels supplement and save batteries for later. But when it comes down to it. The alternator or generator is doing the real work. The panels just cost money and not doing much of anything.

[sensij]

If you need a 400Ah 12v battery system you can build it with 6 x 2v 400Ah batteries wired in series.

2 x 6v in series is reasonable, using Group L16 batteries. Plenty of options for either AGM or FLA, about 120 lb ea.

[Mike90250]

If you are running the engine 1 hr day, look into a marine Cold Plate and build your fridge around it. The engine does the work and chills the plate very cold, and there are phase change fluids in the plate that help store the cold and release it slowly. Save the space for the propane tank for something else.

[reed cundiff]

Engine alternators are fine but we utilize 48 V nominal in 5th wheel. Sufficient amount of solar panels and sufficient battery bank are self-explanatory. Many RV'ers have "sufficient" amounts of both and seldom require generator or alternator. Times have changed
Reed and Elaine

[zombiedude1]

So for a battery isolator I was looking at: https://www.amazon.com/Stinger-SGP32...ttery+isolator

Along with 2x 6v 420ah L16P-AC FLA batteries. (Yes, no longer purchasing AGM after more research)

Wiring Questions
What would be an appropriate wire gauge size for the batteries & charging wires?
So I just wire in series, down to the 200AMP Battery Isolator, to the van starter batttery? And as well from the battery bank to an inverter?

Battery Charging Question
If I wanted to charge from my generator I would just have a battery charger plugged into the AC outlet and hooked up to the positive side of one battery and negative side of the other battery?
What happens if I am running my generator and driving the van at the same time? Should I unplug the battery charger so the alternator provides the charge only?

I really appreciate all the answers I have been given, it's helping me understand more & more to be able to research correctly.