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Old 04-07-2018, 08:27 PM   #1
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Default One battery or two

I'm in the process of pulling out the Onan and building in capacity for two lead acid batteries in it's place.

I tend not to use much power while boondocking though the new style Dometic fridge does not help in this regard. An average would be 20-25 amp hours, unless it's cold enough to run the jet engine, er, um the furnace quite a bit. I have no intention of running a Microwave/toaster oven or other heavy use from the house battery.

I have 150 watts of portable suitcase style solar collectors fed through a Renogy PWM controller.

My conundrum. Due to the slow finish charging of the batteries, I'm thinking I would be better off with one battery vs two. I would still be good for basically three days with no help from solar running one battery. I'm thinking cuz of the slower finish rate two batteries may have a much more difficult time getting to full charge versus just one, creating an environment where the batteries would spend several days to a couple of weeks not getting full.

I really don'r have the need or inclination to get more solar, though the controller is rated at either 20 or I think 30 amps.

If for some reason there was a lack of solar or extra demand I have no issue running my nice quiet Champion remote start inverter genny for a while.

Thoughts? Am I just being too anal and I should mount up 200 amp hours of batteries?

The RT is a 2000 Chevy 200 Versatile.

TIA.
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Old 04-07-2018, 10:17 PM   #2
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You are mostly right on the guess that two batteries will take longer to finish charge than one, but that only applies if the charging source is quite small like the solar is. The extra time won't really be spent in the final 20% of charge as much as in the bulk stage getting to that point because you won't be able to supply all the current the batteries will take.

You 150 watts of solar should get you back in the range of 30-40ah per day if the sun is very good, less than that if it is not, and way less in clouds, rain, shade, etc. If you get sun all day, you should have enough time to top off 200ah of batteries if they are down only 25ah. We routinely have done 40ah out of our 440ah of battery and recovered it all by 2:00 in the afternoon in good sun, with our 300 watts of rooftop.

I wouldn't even worry about carrying an extra generator unless you want to run the microwave or some other high load item. For recharging a 200ah bank, if it gets down a ways because of bad sun, you will be better off to use the van engine and alternator to take you to the 85% full point, and then let the solar finish it off. Your alternator charging from that era is likely about 50 amps, so just about the right rate for 200ah batteries.

You will likely be in good shape, unless of course you like to camp in the deep forest or where it is always raining
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Old 04-07-2018, 10:30 PM   #3
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I'm in the process of pulling out the Onan and building in capacity for two lead acid batteries in it's place.

I tend not to use much power while boondocking though the new style Dometic fridge does not help in this regard. An average would be 20-25 amp hours, unless it's cold enough to run the jet engine, er, um the furnace quite a bit. I have no intention of running a Microwave/toaster oven or other heavy use from the house battery.

I have 150 watts of portable suitcase style solar collectors fed through a Renogy PWM controller.

My conundrum. Due to the slow finish charging of the batteries, I'm thinking I would be better off with one battery vs two. I would still be good for basically three days with no help from solar running one battery. I'm thinking cuz of the slower finish rate two batteries may have a much more difficult time getting to full charge versus just one, creating an environment where the batteries would spend several days to a couple of weeks not getting full.

I really don'r have the need or inclination to get more solar, though the controller is rated at either 20 or I think 30 amps.

If for some reason there was a lack of solar or extra demand I have no issue running my nice quiet Champion remote start inverter genny for a while.

Thoughts? Am I just being too anal and I should mount up 200 amp hours of batteries?

The RT is a 2000 Chevy 200 Versatile.

TIA.
are there bigger alternators that can replace the standard alternator in this? maybe that would help?
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Old 04-07-2018, 11:44 PM   #4
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You are mostly right on the guess that two batteries will take longer to finish charge than one, but that only applies if the charging source is quite small like the solar is. The extra time won't really be spent in the final 20% of charge as much as in the bulk stage getting to that point because you won't be able to supply all the current the batteries will take.

You 150 watts of solar should get you back in the range of 30-40ah per day if the sun is very good, less than that if it is not, and way less in clouds, rain, shade, etc. If you get sun all day, you should have enough time to top off 200ah of batteries if they are down only 25ah. We routinely have done 40ah out of our 440ah of battery and recovered it all by 2:00 in the afternoon in good sun, with our 300 watts of rooftop.

I wouldn't even worry about carrying an extra generator unless you want to run the microwave or some other high load item. For recharging a 200ah bank, if it gets down a ways because of bad sun, you will be better off to use the van engine and alternator to take you to the 85% full point, and then let the solar finish it off. Your alternator charging from that era is likely about 50 amps, so just about the right rate for 200ah batteries.

You will likely be in good shape, unless of course you like to camp in the deep forest or where it is always raining
Thanks Jim.

The genny not going with is a non-starter. We need it for A/C. When in the heat, even only say 75-80*, it's nice to fire up the A/C for a half hour or so to pull the heat out of the coach after driving and the exhaust, trans and other stuff gives off a lot of heat that seems to rise up to the inside. And we do have both a microwave and a toaster oven that gets used, especially at breakfast, so there is a nice little kick to the battery in the morning. The charge control is Progressive Dynamics with a 45 amp converter.

I'm thinking I'm gonna go with a single with a provision to add another. Obviously looking at 12 volts.

The engine running for charging a dual battery setup is something for me to keep in mind. Thanks.

I have followed your setup, and I like it. I just don't wanna do that much work to go that route, and it is a bit of an investment, money better spent on gasoline.

Later, and thanks again.
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Old 04-08-2018, 12:04 AM   #5
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are there bigger alternators that can replace the standard alternator in this? maybe that would help?
Yes there are but I'm thinking I wouldn't really benefit unless going with more than two batteries. I'm just debating whether the extra capacity is really such a good idea unless I really needed it for a couple of days usage while boondocking. More than 90% of our camping is boondocking and generally for a few days to a coupla weeks at a time. I do get pretty much a full recovery charge daily off of my solar.
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Old 04-08-2018, 12:32 AM   #6
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I'm not sure I am following the logic here. Obviously two empty batteries take longer to charge than one empty battery of the same size. But that's because you are putting twice the amps into it. But that is apples to oranges. For a given number of amps, isn't it true that two batteries will accept them FASTER than a single battery?

Now, it may be true that getting to 100% might take longer, but I don't see where that matters, as long as it happens once in awhile.

Or, am I confused?
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Old 04-08-2018, 12:50 AM   #7
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I think the missing information is how much usage and what charge rates you can get from the charging sources. If you have two batteries that are below the 70-80% SOC point where they start to taper on charge amps, and you have a charge source big enough to supply them with as much as they will take, or at least large amount of amps, then you will recover your used amperage twice as fast as with just one of them, give or take a bit.

The original question brought in the premise of having the batteries get full all or most of the time, and that changes everything. If you are down 15%, you will never get much acceptance, so you may be charging at well under your charging amps capacity. If that is the case, you will recover the amps you used faster with a second battery to help use the total amperage.

If you have only one battery and a smallish charge source, it will get the battery to the tapering section of the charge sooner than if it was trying to charge two batteries on the low charge rate, and the sooner you get to the nearly fixed time of the tapering charge, the sooner you get done. So in this case your need less total time.

There are so many variables when you put the tapering charge to full into the mix, that you can come up with just about any possibility.

The good is that on any system that has alternator charging of even very modest capacity, you can get a normal sized battery bank charged enough for a day or two of modest use quite quickly. You won't be full, but you don't have to be all the time, just every 7-10 cycles, so you catch that later when you get good sun or a long drive.

Those with absorption frigs regularly report 20ah per day use, so they can get that back very easily in a lot of ways. Add a compressor frig and that turns into closer to 50ah per day and starts to get you into starting to look at bigger systems. For those that also add coffee makers, induction cooktops, and microwave use, you can easily get to 100ah per day or lots more than that, and require substantially upsized systems.
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Old 04-08-2018, 01:33 AM   #8
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I'm not understanding why you would pull out your generator only to replace it with another. Sure, the inverter generator will be quieter but one large enough to run your A/C is heavy and where are you going to put it?
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Old 04-08-2018, 02:58 AM   #9
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I'm not understanding why you would pull out your generator only to replace it with another. Sure, the inverter generator will be quieter but one large enough to run your A/C is heavy and where are you going to put it?
I was done with the Onan. On two long trips, it broke down to the point that to get it running it would have to be removed. And it's loud and vibrates. And parts are not cheap. Now I have a Champion inverter genny with a remote start/stop fob, mounted on the trailer tongue of my motorcycle trailer. It is rated at 2.8 KW steady, 3.1 surge. It weighs less than the Onan. It has a three year warranty. If I need to work on it on a trip, I can. Cost was only slightly more than what I stuck into and what would have to be spent on the Onan, with me doing the labor. Voltage regulator, muffler, fuel pump, carburetor, then next??

Fueling is a bit of a hassle but I did retain the fuel pump and put on a hose that will reach the Champ's fuel tank. So not so bad unless the weather sucks when I need to fuel. It's on the trailer(which pretty much goes everywhere with me/us) so once camping I can unhook the trailer and leave it up to 75 feet from the RT, helping a bunch more with noise. And I have a fuel supply for off road vehicle playing out in the toolies.

Did I mention before how quiet the Champion is?

If for some reason I want to travel without the trailer(wow, like, without my motorcycle??!?), I can mount the genny on a receiver hitch luggage rack.

I thought quite a bit on the change over and it is/was the right decision for us. Had I made this decision a year earlier I would have purchased a compressor fridge at the time instead of a new absorption fridge and set up the RT along the lines of what Booster has done. But living in the south I still need that A/c option so a genny is mandatory. Have I mentioned how quiet it is?

Hopefully this explains clearly enough on my thoughts and thought processes.

Thanks to all for the input.
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Old 04-08-2018, 04:04 AM   #10
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I was done with the Onan. On two long trips, it broke down to the point that to get it running it would have to be removed. And it's loud and vibrates. And parts are not cheap. Now I have a Champion inverter genny with a remote start/stop fob, mounted on the trailer tongue of my motorcycle trailer. It is rated at 2.8 KW steady, 3.1 surge. It weighs less than the Onan. It has a three year warranty. If I need to work on it on a trip, I can. Cost was only slightly more than what I stuck into and what would have to be spent on the Onan, with me doing the labor. Voltage regulator, muffler, fuel pump, carburetor, then next??

Fueling is a bit of a hassle but I did retain the fuel pump and put on a hose that will reach the Champ's fuel tank. So not so bad unless the weather sucks when I need to fuel. It's on the trailer(which pretty much goes everywhere with me/us) so once camping I can unhook the trailer and leave it up to 75 feet from the RT, helping a bunch more with noise. And I have a fuel supply for off road vehicle playing out in the toolies.

Did I mention before how quiet the Champion is?

If for some reason I want to travel without the trailer(wow, like, without my motorcycle??!?), I can mount the genny on a receiver hitch luggage rack.

I thought quite a bit on the change over and it is/was the right decision for us. Had I made this decision a year earlier I would have purchased a compressor fridge at the time instead of a new absorption fridge and set up the RT along the lines of what Booster has done. But living in the south I still need that A/c option so a genny is mandatory. Have I mentioned how quiet it is?

Hopefully this explains clearly enough on my thoughts and thought processes.

Thanks to all for the input.
Totally makes sense to me and I've had thoughts along similar lines. We already had a Champion generator before we bought the Paseo (same wattage specs as yours but pull start only). We used it with the small toyhauler we had before the Paseo, and it worked great. Sips gas, could run either the AC or the microwave, just not both at the same time, and is very quiet. If all you were using it for was to top off batteries, you could barely even hear it from the next campsite.

I was shocked... and I really mean shocked... the first time I fired up the Onan in the Paseo. Unbelievably loud, and the vibrations from it can be felt throughout the entire vehicle. Love everything else about the Paseo, but not that generator.
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