Small battery bank/inverter as buffer?

[Scott & Heather]

I have read through countless threads here about battery banks and inverters. For months you guys have succeeded in making my head swim and hurt on a daily basis. And frankly I agree with Oohranjay, solar is voodoo ha ha ha! I am hoping I can ask a very specific question and receive a very specific answer from someone here who has better knowledge than I do. Sigh. Here goes:

Right now we have twin Honda EU3000is gensets running in parallel which have been providing almost 6000 watts of juice pretty happily now for a year. They run non stop when we are traveling since I have no inverters and no battery bank yet.

Here is what I would like to accomplish:

1. When my heat pump compressor or a/c compressor kicks on and off at night, the genders (which run in low idle eco quiet mode) throttle up for a split second and back down immediately after covering the initial startup load. It's literally a fraction of a second. Same thing happens when water pump kicks on etc. I would like to have a small battery buffer that could absorb that initial startup so my interior lights don't dim for that split second and the gennies don't throttle blip for that split second. It's the one and only thing that reminds us we are on genny power is that throttle blip sound. It also is the only annoying aberration in the otherwise really quiet white noise sound that might be annoying my trucker neighbors in truck stops as well as anyone else nearby.

2. Also when I transfer from pole power to genny power my clocks all reset and I would love for this to be eliminated.

Can I do this with a small battery bank and large inverter? Run everything to the inverter and the gennies charge the batteries constantly and the batteries absorb the load spikes? This could allow me to turn off one genny too because I have been able to run my normal life and loads with just one Honda running, the only issue is that the initial startup load of the roof a/c will blip the lights and fridge enough to sometimes (not every time) kick the fridge off and back on again. To mitigate that I just run both of them but 90% of the time they are just quietly idling along at 46dB and I'm not even using the power they are putting out. So I would like my entire system to go through an inverter/bank that just gets charged either by pole power or genny power or coach alternator power. Is this a bad idea? Please please I beg you, speak to me in infant terms. Please.


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[Jon]

This free advice is worth every cent you will pay for it.

To deal with the clock issue just use battery powered clocks. Either using a AA battery, or Dc power from the coach house battery.

While the generators are not a bad idea I question if they use gas instead of diesel, and if so one of my first objectives would be to use a diesel generator.

A house battery bank and inverter(s) is how all professionally converted coaches are set up. While this set up is not perfect, and tends to be a compromise as almost everything is on coaches right now that set up addresses a lot of needs. To make that set up more ideal it should have a fully automatic transfer switch. That feature makes the system user friendly, but there is going to be a delay any time sources change so any items that will reset with a power interruption are still going to be a problem, such as clocks, AC units, etc.

Your current producing system is as basic as you can get and when you add batteries, inverters, automatic transfer switch, etc. you get complexity because you haven't eliminated anything, but in fact have added stuff. As you change power sources from generator to shore power I suspect you are going to have the same problems you have UNLESS you run 100% of the AC powered devices through the inverter(s) and all the gensets and shore power do is charge the batteries.

[Oonrahnjay]

     I'm sorta like a broken record on this but what you're asking for can be taken care of very neatly by a "Load-Sharing" inverter.  I have a modern, well-designed, efficient inverter that's easily programmed and is totally reliable -- BUT it doesn't load share so it's either all from the battery or all from shore/gennie power.  The one I have (made by Outback) is designed to sense voltage dropping and bring in inverter power quickly enough to avoid the clock-resetting problem and it works ... mostly but a load-sharing inverter is already running and in the loop and will do a better job.
     If all you want it a buffer, even a small battery ("marine-type" would prob work well, although a normal "start" vehicle battery, while less deep-cycle, has stronger plates and may resist vibration and bump loads better -- YMMV) should work for you.  Of course, if there's a time when you need to take a gennie out of your combined-setup for service (or, I hope not, you have a problem with one), then more battery capacity will help keep your house power stable for a longer time.  This is an issue that you'll have to work out considering your needs and how near you need to go to disaster proof.
     Speaking of capacity, many 12V inverter systems cannot supply enough 120V power to run more than one rooftop air conditioner (some struggle with one), so you may need a high-capacity 12V inverter or else go with a 24V inverter and two batteries.  Again, how long is a piece of string and how long do you need it to be???
     I think that what you're talking about is an easy system to design and install.  I'd be sure to consider a good transfer switch to handle the change from shore/generator/battery-inverter power and the accompanying neutral ground needs, but what you're talking about is pretty simple.

[blue_goose]

Lets see if I can make this easy to understand.  The best way to wire a coach is with two 24 volt 4000 watt inverters that are designed to switch the load.  Everything in the coach is powered through the inverters and doesn't know what is powering them.  Depending on how long you want to run off the pole or gen. determines how much battery power you need to install.  The type of generators you have may still spike if you let the batterys get to low before you start them up.  If you still have the large alternator on the bus you won't need anything else going down the road.
Jack

[B_K]

While Jack, Jon and Bruce have all given great info here.
I am like you and easily confused about the inverters and the "BEST" system.

My vote is to contact Sean Welsh and get his opinion on what will work best in your use situation.
He does get rather techie when talking electronics, but I think he can keep it simple if you remind him your challenged in that area.
(at least when I get to that point that is my plan)
  BK 

[sledhead]

how I did it but simpler

a 24 volt battery bank   4 x 6 volt golf cart batteries and this inverter . you set the remote at your driver seat to say 15 amps coming in or 20 amps or 30 amps . so how it works is if you go over about 14 amps or 19 or 29 amps the inverter will add the extra power from your batteries as it needs it and when you do not need it it will top up your batteries as a charger  

you will not even know this is happening

another + is if you install it right you ac will work off the engine alternator as you go down the road with out using the gennes

the only inverter I would buy    yes it will cost you some money
https://www.solar-electric.com/magnum-energy-msh4024re-hybrid-inverter.html  
https://www.solar-electric.com/mameadrecofo.html


dave

[Scott & Heather]

Wow. This is really simple excellent info. Exactly what I needed. Thank you so so much. So here is where my mind is at:

A load sharing inverter might be the ticket. But yes I basically don't need to run the coach off a battery bank ever really. I have too much electrical needs. But I have been able to keep my average load down enough that I can run one roof a/c and the rest of my needs on one 3000 watt genny. The only exception is when the compressor kicks on and off, it works but the lights blip and the fridge resets. I can't imagine this is good for it when this happens every several minutes. So to be able to absorb that blip and charge back up in between a battery bank would be nice. I can't use battery clocks when my clocks are microwave and stove top/ appliance clocks. You wouldn't think resetting clocks is a big issue but after 12,000 miles in the past three months and constant resetting it becomes more of a priority that you'd ever imagine. I am comfortable running the gennies constant while parked in a no pole situation so again, I just need a buffer but I would like it to be for the entire coach system. So 100% of my AC power would come through an inverter and the batteries would
Be charged by three different power sources depending on the day. Either coach alternator, genset or pole power. That's it


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[Oonrahnjay]

... the only inverter I would buy    yes it will cost you some money
https://www.solar-electric.com/magnum-energy-msh4024re-hybrid-inverter.html  

https://www.solar-electric.com/mameadrecofo.html

dave 

     Back on my hobbyhorse; that's a classic load-sharing inverter and all the specs appear to indicate that it does so very well.  Also, the remote control appears to be an excellent device (I haven't used one but reading the specs and info on the "control wheel" to select menu items instead of having to scroll down appears to be very good).

[eagle19952]

so....run the fridge and the compressor (both of which run intermittently/periodically) off of the/an inverter.

i have only two 8d starts and my inverted load needs are similar to yours. i have no "house" bank. When on shore or gen power my 220v loads < heat and AC> and my hot water 110V 20 GALLON and my load sharing/pass thru inverter/charger are serviced by the source.....which then the inverter 3000 watt, feeds a sub-panel on which resides every outlet and sundry 110v lighting loads,my microwave and 2 electric 110v burner Sealand hob etc. this has worked well for 20 years 13 of which includes my ownership. i have re-wired to balance these loads.
further, somewhere in the archives resides a post whereby Sean said were he to reaccomplish his set-up he too would have re considered separate banks (start/house).

i do have an auto transfer switch too.in case of power outage. but i am the auto gen start...

[Beachfinn]

Scott,
i think you are on the right track. I'll say this though; Solar is simple, though not cheap, and it is awfully nice to have full house batteries, when i pull out of storage, or run just basic stuff. In moderate climates, i don't have to run genny at all during the night, i run all basic stuff out of house bank, even some heat. i will put a switch to one roof top, so i can run that also through inverter, if needed. Lastly, after i smoked my genny starter few weeks ago, it sure was nice to still have basic power (the genset was charging the house bank at 140A for quite a time after few days of running out of batteries). As a matter of fact; ill be adding more solar, likey few more batteries and possible another inverter (if i can find the space; maybe a pull out tray in the spare tire compartment). i have automatic tranfer switch for shore power and a surge protector/analyzer for shore power, that wont let bad ju-ju in the house system. Most of my bus dont know where the power comes from, outside of the  AC units, everything works in any situation. I will tie the house to the coach electrical by switches; so that house bank can be charged via the mega alternator and if needed a starter jump can be done with house bank.

So, in short, in my opinion, it is worth throwing a few more batteries than you think as well as over sizing your inverter. In your situation; it would be darn nice if you had to leave the bus, to have your fridge run off solar...

Sami

[Kmj5200]

I have a question about the house bank. Lately I have been learning about house banks that DIY'ers are creating for their home, that they compare to the Tesla house pack. Made from Lithium Batteries from abandoned laptop cells and the like.  These can be created to any size. Would creating such a pack to use in RV conversion be advisable?  Would it be less than, equal to, or greater than using traditional deep cycle 12 or 6 volt setups?


Kenneth

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[ArtGill]

A mini split uses Inverter technology in the unit and there is no current inrush or spike because the current slowly ramps up and the compressor and fans only runs as fast as needed.  I have an 18,000 btu, dual head min split and the most current I've seen it use was 10.9 amps at 120 volts AC.  This happened when the unit had been cut off overnight on a cool night.  I cut on both units and set the demand at 75 degrees and the current ramped up to 10.9 amps and then went back down as the temperature was satisfied. No sudden change in load.  I have an amp meter installed and I have checked it an inexpensive clamp on amp meter.  After i have more time to test and get some cold weather I will post a message with my findings.
Art

[buswarrior]

Load sharing inverter charger. Period, end of story.

Trace 4024 in the old days, the Magnum hybrid linked above today.

I could run 2 crappy mid 80's roof airs with 4 crappy golf cart batteries, the Trace 4024 and a Yamaha EF3000iSEB.

With just a kiss of extra for the batteries.

The stock coach alternator would run the same roof airs via the Trace going down the road.

Swap the plug from the generator to the power pole, as noted, the clocks didn't know, and didn't care.

You can screw around, or just run with the big dogs.

Load sharing inverter charger.

Job done.

happy coaching!
buswarrior

[daddysgirl]

You might look at this, while you're looking. I have the 90 AMP model 4590

http://www.progressivedyn.com/all_in_one_pd4500_1.html

I love it. I have a house bank that is separate from the 8D's. This keeps the batts charged, and has AC and DC Circuits with protection.
When I get the starter installed, I get to figure out how to use the additional 55amp charge/converter...or If I'll need it.

[TomC]

Simple-get rid of the twin gasoline powered Honda's (yes they're cheap to buy [compared to Diesel]) and install a Diesel. Powertech makes a nice compact 8kw with reverse cooling (pulling air through radiator and discharging it down). I had a truck driver friend that had one in his truck and when he sold the truck, the 8kw had over 23,000hrs on it. You would need 3 replacement Honda for that amount of hours. Good Luck, TomC