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Old 06-19-2016, 07:31 PM   #41
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Electrical Questions:

Electrical Questions:

What I want to accomplish is an electrical system that will allow me to run some outlets (phone chargers, computers etc, no appliances) and the AC off the bus batteries and alternator (with a inverter) while the bus is running and then power all that same stuff with the generator when not running the bus.

My plan was to run a cord from the generator and a cord from the bus batteries to a central box between my seats in the bus. These would run into a selector switch where I could turn it to Battery power, generator power, plug in 50amp power, and an off switch/selector. Not sure if a 4 way selector exist but at least the 2 or 3 would be nice.

My question is, am I going to need a separate battery bank while running the AC and outlets while using the bus batteries or could I hook directly into the 3 existing batteries used to start the bus. Will a 15,000btu heatpump and some small phone chargers run the batteries dead (over say 15 hours) or will the alternator be able to keep up?

I bought a EU7000is Honda generator, super awesome generator. Been using it on the road and it is beastly. Ran a refrigerated beer truck, 4 industrial fans, and a full PA for a band all at the same time. I think this thing could run a neighborhood if it needed to, and needless to say will be more than enough got the #BRAGeorgia bus. I plan to weld some mounts to the bottom of the bus and mount it there. It is ~ 261lbs and will need significant amount of supports holding it.

I also bought this 15K btu heat pump, as the bus is a sweat box here in the summer and AC is needed.

Advice on how to set this up, inverters to buy or selector switches would be GREATLY appreciated.

THANKS!!!
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Old 06-19-2016, 08:35 PM   #42
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You will need to see how much start up juice is required to get the A/C unit going. That will determine how large your invertor has to be to run the A/C while going down the road. You will also have to do a power inventory to determine how large of a battery bank you will need to power everything whenever the genset or engine alternator isn't producing power.

As long as the bus is running you can run all of the batteries together so that the alternator is recharging as you go along and powering your systems at the same time. I would guess your bus alternator is at least 150 AMP and could be as large as 250 AMP or larger.

You will need to be able to keep the house and bus batteries separate when the engine is off or you will run the real risk of not being able to start your bus the next time you want to go.

As far as starting batteries are concerned, you really do not need three Group 31's to start your bus. It has that much reserve CCA's to make up for the way in which school buses operate. Even with 250 AMPS alternators it isn't unusual for a bus to use more amps than are available at idle when stopping and picking up/dropping off kids at bus stops. The total load of head/tail/clearance lights, overhead 8-way flashers, stop paddle flashers, heaters/defrosters/blower fans/vent fans, or A/C can put a very large load on a system. With a battery bank with ample reserve you don't need to worry about not having enough juice to start the next morning.

You could probably get away with just one Group 31 battery if the CCA rating was at least 1000 CCA's. Your house batteries need to be a deep cycle type of battery that is designed to continuously cycle from full charge to full discharge. Deep cycle batteries are no good as starting batteries.
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Old 06-19-2016, 09:15 PM   #43
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Thanks cowlitzcoach!! Good advice on the alternator.

My plan was to always wither run the bus or the generator when running the AC. That being said do I still need a battery bank other than the one used to start the bus? It sounds like with a 150 or 250 amp alternator I would not, but then you mentioned having to run a bunch of other school bus related items may use more amps than produced by the alternator. But I'm not running flashers, heaters, stop signs etc.

Rather than mess around with hooking up a battery bank to the alternator, Id rather just run the generator I have when running the AC/other interior items. Its super quiet and will run about 20 hours on a tank. Unless you don't think the alternator can't keep up and I'll need a battery bank anyway. If this becomes a problem I can always go back and add a bank of batteries.

The AC is 2114 Running Watts, and I could not find a mention of starting watts. I would assume a 3,000watt inverter would be a fit. Do you guys have any suggestions on invertors? Is one with a charger a good idea too? Switches as well, having trouble finding a 4 way selector switch for this application, most look like battery selectors.

Thanks!!!
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Old 06-20-2016, 12:13 AM   #44
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The common thinking behind having two battery banks is that batteries are likely to be accidentally run down with lights and such to the point where the battery is no longer able to crank and start the engine. If that happens to the "house" battery bank it's not so big a deal because the separate coach/starting battery is still charged and ready to to crank the engine.

The EU7000is is a beautifully quiet machine. I haven't used mine much yet, but I'm looking forward to it!

I wouldn't plan on idling the engine to run its alternator to power an air conditioner. For one thing, generally an alternator produces much less than its max rating at idle. For a long time I wanted to find a way to put A/C in my bus engine-driven for when underway and generator or shore power driven at other times. After I picked up that EU7000is, or I guess during the process of deciding to buy it, I decided it just wasn't worth the complexity of trying to involve the engine/alternator. I'll just always run the generator (or shore power if available) when air conditioning is wanted.

Probably I'll violate the conventional wisdom on separate battery banks... I'd really like to have a LiFePo house battery bank, and my starting batteries are basically done for. If I pool the money for the replacement starting and new house batteries then I can justify making the upgrade to LiFePo. But I recognize that I'll have to monitor the state of charge and learn through experience how dead is too dead to start the engine, and I'll have to have a method ready to recharge the batteries from the generator when that situation does happen.
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Old 06-20-2016, 01:30 AM   #45
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You will need a battery bank in order to deal with surges like when the A/C starts. The invertor will be able to "take" from the battery bank more juice than what is being produced by the power source.

In other words, the battery bank will reduce the peaks and valleys that occur as loads are added and subtracted.

As far as switches are concerned, I think Cole Hersee makes a switch for just about any application.

West Marine
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Old 06-20-2016, 10:55 AM   #46
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I use a Bosch SB-200 (its made to be a school bus alternator).that is 200 AMPS.. BUT it puts out 140-150 Amps of Juice at engine IDLE.. so that way I can pull quite a bit of pwoer even with the engine just idling and still keep the batteries charged...

im not sure how much insulation you have and if your windows are tinted or not.. but with 15K BTU and non-tint windows you'll have a tough time keeping it cool with one unit... if the windows are tinted and the bus is in the shade you'll have a much easier time cooling it down...

-Christopher
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Old 06-20-2016, 12:10 PM   #47
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cadillackid - Thanks for the info! So do you not use a separate battery bank?

The windows are tinted, which is good, but didn't add additional insulation as I won't use it full time or enough to justify the cost. I am hoping going down the road a 15K will be enough to keep it cool, then at night when the sun goes down. I'll have to look at my alternator to see what it puts out. maybe cheaper to get a new alternator than put in a battery bank.

I don't plan to idle and use the AC, as soon as I stop I'll switch over to the generator.

I Plan to use one of my emergency roof hatches as the AC duct and custom build a plywood mount around the opening. This looks pretty straight forward to me but I haven't received the AC unit yet. Any one have any thoughts on this?

Thanks Guys!
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Old 06-20-2016, 12:36 PM   #48
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I have a separate battery bank of 3 Deep cycle AGM VRLA group 31s anda 1500 watt pure sine wave inverter.. ( I went pure sine as im a Mobile Software / hardware DEV lab so i am running a server rack at times)...

I have a 7 window short bus.. for Stopped A/C i have a 12K Portable Inverter unit (2 pipe)(no hard start surge.. it slowly ramps up).. currently I do NOT have tinted windows and that A/C has a real tough time keeping it cool inside.. my bus is bone stock..

for road A/C i have an engine driven 40 + 30 system... originally I installed a single 50k unit behind the driver seat and ducted it to the seats and work area in the bus (temporary for testing)... it kept the back of the bus comfortable.. but the driver cockpit still hot..

so I started hush-matting the firewall and sealing up any openings i could find for wires / hoses etc.. and that has made a huge difference...

Next I wanted to clean out and update the driver console heater box... well it ends up that its manufacturer did really piss poort design of that console and the school fleet hacked it up tryign to change blower motors.. so im gutting it out and installing a 30k A/C heat unit up there.. which will handle the dash vents and floor heat for numer-uno (me) and a second smaller heater ducted to the left windshield defrost...

I de-rated the unit in the back down to 40k as my condenser is designed max at 70k btu..

electrically the batteries are isolated so they wont run the starting batteries down when the bus is off...

when the bus is running my 200 amp alternator will charge both the starting batteries and my aux batteries... my Bus gets driven far more than its parked online on average... though it is noce to park and leave that 12k A/C running even if ijust run into a store..

I built a little voltage detection circuit so that my battery Isolator relay will not kick back to join the main system in until the alternator is actually putting out voltage (or i can override with a switch)...thus if I turn the key on but dont start the engine then my batteries will not join back together..

I'd Love to have a generator but i cant seem to find a nice way to do it without a Lot of hang-down and ground clearance loss... my bus drives in the cities quite a bit where steep driveway enterances are common... thus I dont want to scrape the generator on the ground...

your biggest hurlde will be staying cool while driving due to engine heat and hot air infiltration into the bus at highway speeds..

-Christopher
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Old 06-20-2016, 01:41 PM   #49
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Hey Cadillac...you can always hang the Genny on a small rear deck. That was the only place I could fit mine.
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Old 06-20-2016, 01:53 PM   #50
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Quote:
Originally Posted by Tango View Post
Hey Cadillac...you can always hang the Genny on a small rear deck. That was the only place I could fit mine.
I kind of like that idea.. so you just have a deck off the back and then built a little "house" for the genny?

I could probably also pump air springs up higher too.. but I dont know how high you can go before they pop like a balloon..

-Christopher
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