Charging batteries by gen or shore power?

Endi

I'm looking to buy a charge controller that can charge batteries from my panels, but ALSO from generator or shore power.  Is there such a charge controller?  If not, is there a device that will let me charge the batteries via shore or gen power?

BB.

Nothing that I can think of (I am not in the solar business--So there may be products like this out there).

In general, solar panels>DC Charger>Battery bank is all DC based.

With AC based generators (there are DC output generators too), there are no AC input(s) to a typical DC Solar Charger.

If you wanted AC power--There are quite a few integrated-chargers that take solar panel power, AC power, and DC Battery power, and have the ability to manage those to give your 120/240 VAC output, and manage the "system" (supply AC power, manage solar charging, can auto start a genset, etc.).

Otherwise, you can go with an AC input to DC output battery charger... In general, you can "parallel" multiple charging sources to a single battery bank. In general, as long as long as all the battery chargers have the correct charging set-points, the system will work.

From one point of view, a "manual" genset charging system works well... No auto start issues, no running genset out of oil/overheating/fuel in the middle of the night--Failure to crank, dead starting batteries, over/under charged main batteries, etc. Problems with cold start, issues with different fuels (gasoline, diesel, propane, etc.).

Automatic genset charging seems to devolve into aberrant behaviors (won't start, won't stop, won't start at the correct charging set-points, etc.) And with (sometimes multiple genset/charge control modules), configuring the various parameters, trying to debug run problems, trying to figure out what genset auto-start interface works with which controller brand/model/option, auto start capable generators are generally on the larger size--And can "waste" fuel (In general, loading a standard gasoline power genset to 50% or greater output is more fuel efficient... And many of the smaller/electric start gensets, don't have auto choke (have to manually setup choke solenoid--Or look for a fuel injected genset--again not very common or cheap).

So, stepping back from looking for a specific solution--What is your system like now, what is it that you are looking for (size/voltage of battery bank, battery type, etc.) auto or manual genset control, etc...

We should be able to give you better answers then. A small 1,800 Watt genset, vs a 10,000+ genset are going to have very different hardware configurations and capabilities.

-Bill

Endi

Thank  you for the reply.

This is the setup so far:

3 100amp batteries 12v
3k inverter
2 100watt panels (adding 1 more next month)
Champion 2k generator, has 2 ac outlets, 1 dc (cig looking) outlet
Various solar cables, connectors, 2 10g and 2 12g solar wires.
Still need a charge controller. And a way to charge batteries by gen (occasionally shore, but that's rare) when there is no sun. 

littleharbor2

You can find the Iota ac to dc regulated chargers at the host's store Would this work?

Iota DLS-55 12 Volt 55 Amp Regulated Battery Charger with IQ4 | NAZ Solar Electric (solar-electric.com)

BB.

First the battery bank... You did not say what type of batteries they are (FLA, AGM, GEL, LiFePO4?). Lets assume that they are flooded cell lead acid. generally, 5% minimum rate of charge (mostly for battery banks that are not used very much), to 10-13% minimum for cycling battery bank (i.e., off grid system, daily cycling). And can go as high as 20-25% (a bid hard on batteries, and generally suggested that 13% or greater rate of charge, that you use a charger with temperature controlled voltage output--I.e., as FLA batteries get hot, their charging voltage requirement falls). If you are monitoring the bank state of charge and temperature, and using AC/Genset for occasional charging (bad weather, poor sun, etc.)... You could just turn off genset charging when the battery is charged/or turn off if battery temperature gets too high.

So, from a basic math point of view, the charging current for your bank would be (remember that numbers are approximate--Just level setting expectations):

• 300 AH battery bank * 0.05 rate of charge = 15 amps minimum
• 300 AH battery bank * 0.10 rate of charge = 30 amps nominal
• 300 AH battery bank * 0.13 rate of charge = 39 amps "cost effective" maximum rate of charge

Then there is the rough maximum your genset can charge at... Remember that batteries if significantly discharged, can draw "maximum current" for 5+ hours (say 10% rate of charge from 30% SoC to 80% SoC--Dif, ference is 50% charge capacity at 10% rate = 5 hours). You do not want to run a 2kWatt genset at 2kWatts for 5 hours--Generally residential gensets are not designed to run at "full power".

For the Champion 2,000 Watt genset, there are quite a few variations--Generally rated 1,600 to 1,700 Watt continuous output... I will pick 1,600 Watts for the following:

• 1,600 Watt rated * 0.8 genset derating * 0.8 PF/Charger Efficiency * 1/14.5 volts charging = 70.6 Amps max suggested charging current into 12 volt battery bank with this genset

Note that AC charger Power Factor / Efficiency is actually quite variable... "Matching" an AC charger to your genset (6 different Champion "2kWatt" models--And some are propane--typically lower running watts. And inverter-generators have less surge capabilities).

Anyway, for your battery bank--If you go with 10-13% rate of charge--You do not need a very large AC charger--And will not overload your genset.

You have not talked about your expected energy usage per day (AH @ 12 volts or XXX Watt*Hours per day)... Your 3,000 Watt AC inverter is really "way to large" for a 12 volt @ 300 AH battery bank... For a "reliable" setup, the suggested maximum AC inverter would be around:

• 300 AH battery bank * 1,000 Watts * 1/250 AH (at 12 volt) battery bank = 1,200 Watt suggested max AC inverter

For that size of 12 volt battery bank, I would be suggesting a (roughly) 600 to 1,200 Watt AC inverter maximum. A 3 kWatt AC inverter on that size battery bank running at 3,000 Watts would flatten the bank in 1 hour or less--And there is a good chance the bank may not even run a 3,000 Watt load (let alone surge current for starting motors/tools/etc.).

Lets say you want to run your loads for 1/4 of battery bank capacity for 2 days--To 50% State of Charge (two days of "no sun", don't deeply discharge battery for longer battery life) and sunny day or genset charging for the 3rd day. Your bank would supply:

• 300 AH * 12 volts * 0.85 AC inverter eff * 1/2 days run * 0.50 max planned discharge = 918 Watt*Hours per day
• Say run lights/radio/etc. for 5 hours per night: 918 WH / 5 hours per night = 183.6 Watt average load (for 5 hours per night/day)

As you can see--A "generic" AC load for 5 hours (evening use in Cabin) would work just fine with a 200-300 Watt AC inverter.

Sizing the solar array for a 2 day/50% discharge load:

300 AH * 14.5 volts charging * 1/0.77 solar panel+charger deratings * 0.05 rate of charge = 282 Watt array minimum (emergency power)
300 AH * 14.5 volts charging * 1/0.77 solar panel+charger deratings * 0.10 rate of charge = 565 Watt array nominal
300 AH * 14.5 volts charging * 1/0.77 solar panel+charger deratings * 0.13 rate of charge = 734 Watt array "typical cost effective maximum"

I would suggest that a 282 Watt solar array would be the "minimum" for your 300 AH @ 12 volt battery bank (for battery health). 10-13% would be better...

But we also need to know your (rough) location and seasonal usage... Live in a "sunny" location, you can get 3+ hours of sun during winter, and 5+ hours of sun during summer. If this is for summer camping, we could use 5 hours per day of sun. If this is for 12 months a year usage (cabin, small off grid home), then it could be 1-3 hours per day of sunlight...

Using 5 hours per day for a sunny/summer usage, the equation would look like:

918 WH per day * 1/0.52 overall solar system eff * 1/5 hours per day sun = 353 Watt minimum solar panel (as an example)

If you "needed" this power and to minimize genset use (i.e., random clouds/bad weather/etc.), then would suggest that you only use around 50% to 65% of your predicted harvest. I.e.:

353 Watt array * 1/0.65 solar fudge factor = 543 Watt array to minimize genset runtime...

I will stop here--There is a lot in this post--And I am sure you probably will have questions. I am a big believer in doing the basic paper modeling of your solar power system before you start purchasing the hardware... There are a lot of decisions that will affect your hardware purchases and system configuration. Want to make sure the system meets your needs before spending your money.

The charger that LittleHarbor2 suggested is a good quality charger that should work with your 2kWatt genset...

-Bill

Endi

Wow. Okay that is a lot of information. I'll try to digest all that. We're on the road for the next three weeks, plenty of time to try to learn a bit more, which I obviously need to do.

The inverter was a gift from a relative who never used it. The plan is to upgrade to new batteries this spring.

Again, wow. A lot I didn't know! Thank you all for the help. I've printed this out and hit the road in a day. Hopefully I can figure this out!

BB.

Please feel free to post your questions... I know I threw a lot at you--But to design and build a solar system that meets your needs has a lot of details that need to be addressed to ensure the system will work for you.

I do the math so you can plug in your own numbers and understand how your needs/expectations can affect your hardware choices--I have just used generic values and guesses that should give you a reliable home cabin or possibly RV system that would give you reasonable output (based on what you have told me so far).

Solar Panels + Battery banks don't produce as much energy as most people think... Batteries are expensive--And on average, AC inverters are cheap. So it is not unusual for folks to "under panel"/"over estimate" how much energy per day they will harvest and just hang a big/cheap AC inverter on the battery bank and call it a day.

In the end--Starting with conservation (pick the smallest/most efficient loads & hardware you can), then design the system to meet those loads.

For most folks, they "kill" their battery banks with under charging / over discharging (too many loads, too little charging). And these days, batteries are some of the most expensive components with the shortest life--You want to make sure that you don't over stress them... Depending on batteries and use--Typical Lead Acid batteries can last 3-7 years if properly maintained. And they can be destroyed in a few weeks or even days if not kept properly charged.

Have a safe and fun trip!

-Bill