Will this work for AC power for my bus?

[belfert]

I have currently an 8KW diesel generator, Prosine 3000 watt inverter, and six AGM deep cycle house batteries that total 300AH at 24 volt for my power.  I never have shore power when on the road.  My current batteries are fried after seven years.  If a heavy load is put on them they drop to well below 24 volts almost immediately.

I make one or two trips with the bus every year so buying another 600 amp hours of AGM batteries simply doesn't make financial sense.

My thought is to buy two AGM batteries, a used Honda EU2000 generator, and a solenoid to connect the alternator to the house batteries.  The Honda generator will be used when A/C isn't needed to keep the house fridge and the chest freezer powered.  I figure the Honda generator is the same cost as more house batteries and running the big diesel generator during the day to charge them.  When traveling the alternator should provide power.  If we need A/C then we do need to run the diesel generator.

Any reasons this won't work?  I would prefer to have just one battery bank for starting and house, but two 8D AGMs may not be enough to start the bus especially if discharged from house use.

[Oonrahnjay]

... Any reasons this won't work? 

     Your first question should be "what's the typical amp-hour load you see when you're not running the A/C"?  If two 8D's will give enough power to run those "light loads" for 24 hours, just charge them with the big gennie every morning (you'll want power for hot water -- showers, dish washing) anyway.  Plus when you're running the generator for A/C, you'll be charging the batteries then too.  It sounds to me like your typical power profile would be "generator in the AM for battery charging and 'morning loads'" and generator running in the afternoon for A/C.  Is this case, you really wouldn't need 24 hours of capacity.

     The issue of start versus combined batteries is a conumdrum (to me).  The way you've described how you use your bus, you usually know when you'll be starting up - you could just arrange to start the gennie (I think that everyone who gets away from a power pole needs a separate generator battery) in time to charge the batteries enough to get you started; if you did that, you could live with a small combined bank and not worry if house loads are drawing it down.  As you said, once the engine is running, you have the alternator to provide a charge.

    In the right conditions, the Honda would be overkill.

[belfert]

With all the loads we have running I don't believe we could get through 24 hours on two 8D batteries.  Right now with the 6 batteries at 100AH each we have been  lucky to make it 18 hours before charging when the batteries were good.  If we run just the fridge the batteries go several days.  On the trip this past week we had a 700 watt food warmer running 8 hours a day which required running the diesel generator during that time.  A small Honda generator could handle this load with less fuel and noise.

I do have a separate battery for the generator.  One concern with a combined house/starting bank is what happens if the generator won't produce electricity?

Another option I thought of is an auto start for the generator.  I would need a standalone module as my inverter won't do auto start.  This would insure having power when the batteries get low.

[bansil]

some solar would really help out during the day

our system is small right now

I have 1 12v deep cycle marine battery 115Ah

on the roof (flat not tilt able yet) I have 3 50watt panels

and I have a small 1500 watt modified sine invertor

also have a 200 amp solenoid that is wired to starter lug with 175 amp fuse so I can take advantage of my 190 amp alt while running down the road

the solenoid is controlled by an oil pressure switch so it switches once engine is running (I don't want to try and start bus with #4 cables)
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In the morning as soon as the sun comes up, the light on the ASC controller comes on and starts trickle charging battery and slowly increases as the sun rises until it sets....so I can "guess" that I can get a good 6 amps for 5 hours to charge battery (during the day the fridge doesn't use very much at all) and in the morning I was still at about 12.45v on the battery

when engine is running I am charging the battery with sun and alternator

my main loads are a full size fridge and a few lights, when wife wants to use the microwave or rotisserie on the road the alternator is more than enough for under 1000 watt loads (without draining battery)

next step will be one more battery and another 150 watts of solar and we should be good to go


This was designed for a normal travel day of 6-8 hours (we can slow cook, rotisserie a chicken, use 700 watt burners to heat up stuff in pans or use toaster oven while under way) and we don't have to cook when we stop for the night (dinner is done), and then be able to boondock overnight (keep ice cream frozen and beer/wine cold and read with a couple lights) and then make it to shore power next day, and works great for that purpose

just putting this out so you can see other ways to do it

[belfert]

I'm trying to figure out the most cost effective way to provide power for a bus that only gets used for one or two 8 day trips every year.  I don't think solar is the answer in my case.  The most cost effective answer might be to just run the diesel generator for 168 hours straight.  I figure the cost at around $350 each trip.  I'm just thinking there has to be something better than spending $350 on generator fuel per trip.

[Lin]

Our situation is not the same however, we have added a small Honda generator to our options too--an EU1000.  After running the 7.5 kw generator in the AM to heat water, etc., it seemed ridiculous to keep it running just to charge the batteries.  We traded some things we no longer wanted for this generator that the former owner no longer wanted (Yay Craigslist!).  So it would seem to me that your plan would be good.  The 2000 is a better choice than the 1000 we have.  The 1000 is very limited since it only puts out about 800 watts really. The 2000 will put out enough to be charging the batteries and still have some power left for some incidentals.

[bevans6]

You have the big item, the Prosine inverter, already.  What my solution was, in your situation, is to have four 6V wet batteries at 232 AH, for a $400 232 AH 24V battery bank.  You should be able to run overnight on that.  I have a $40 Marine A+B battery switch that lets me connect the house bank to the inverter on/off, or bridge in the start batteries and charge from the bus alternator.  That lets me run the big inverter from the bus allternator when the engine is running, charge the house battery bank, run the inverter (with light loads, like the fridge, TV, etc) overnight from the house bank only, bridge the house bank to boost the start bank on cold mornings, etc.  If I am parked for a while and need to charge batteries or run the AC I start up the Yamaha 3000 watt inverter generator.  It can run all my loads including my AC unit, and charge the batteries.  You already have your generator so you don't need another one.  I leave the house bank connected to the start bank 90% of the time, the only time I disconnect is if I am going to be draining the house bank fairly far, then I disconnect it so the start batt's don't get discharged, for two reasons.  One is the bulk and absorbtion charge scheme is different for the two types of batteries and the other is so the house bank recharges in half the time.

So what I would do if I were you is just buy four wet golf cart batteries, a marine battery switch, and have at it.  $450 bucks total, and use what you already have for the big buck items.  In your situation I see no benefit to AGM batteries unless there is a physical installation constraint I don't know about. (you have the batteries installed upside down or can't vent them except into your bathroom, or something...)

And get a smart battery maintainer, if your Prosine isn't a good charger.  I don't know the unit so I can't comment.  I use my Magnum 4000 to maintain both banks.

Brian

[TomC]

Forget the Honda 2000. Just run the Diesel genset (which will ultimately burn as much as the Honda 2000 most times anyway) when needed. I have two 8D AGM's and many times will run the genset for 2 hours in the morning and 2 hours at night. Not a lot of fuel burned either. Good Luck, TomC