House batteries toast?

I neglected to indicate that my "strategy" is only used when shore power is not available, which is less than 50% of the time and never for more than 4-5 days at a time. Otherwise, traveling or shore power gets me to 100%.

Voltage alone is not nearly good enough to know the state-of-charge (SOC) of the batteries for the reason you mentioned (batteries at rest) plus SOC is very sensitive to voltage and to temperature. I have learned that a good battery monitor is essential for anyone who camps without shore power for more than a day. It also confirms my point that amps-in drops off rapidly as the SOC increases. Without a battery monitor, you really have no way of knowing the charging amps. IMO it's not worth running the generator once the SOC reaches about 80%. Plus 80% SOC easily gets me another day until the SOC reaches 50% again.

Anyone who does an energy balance on charging via generator (fuel consumption vs energy to the batteries) will find it very inefficient, but sometimes that's the only option.

I don't have (or want) solar, but that's another story.

P.S.My 2 Lifeline GPL-4CT batteries are more like $400 each, but have significant advantages over most other "deep discharge" batteries used in RVs.
I agree. I don't know anyone who uses a generator for the last 10% on any regular basis. I had a bad controller and no solar for about 4 months, so I hear what you're saying. It takes a crazy amount of generator fuel to get them full going all the way through absorption. Clearly, generators are most efficient at the bulk stage, as folks have said. When I didn't have my solar, I was doing what you say you're doing; rolling though campgrounds at least every 4-5 days just to top them off. I get down as much as 200AH regularly on an 800AH bank. My system is designed for a max DOD of about 25-30% of bank capacity because I full time and am in it for the long haul. I agree that battery monitors are essential for 1 battery or many. The beauty of solar for me, as a full time traveler, is that, depending on the weather, I can usually not run the generator (I only carry a Honda 2000) at all, or if necessary, just an hour or so in the am, then let solar bring the batts up to 100%, even while on the road.

I'm looking at a 23' class C for a year long trip to South America and will likely only have a 200AH bank due to space. I'm going to set it up with a large alternator for charging while driving, or if parked. I don't know if I can retrofit the technology, but I want to get the auto start feature that starts the engine/ alternator, if the battery bank (not engine starting battery) hits a certain low set point, during the night, then kills the vehicle engine once a certain time expires. The original OP would be well served by this strategy, if it can be fitted to existing vehicles. Hymer has this on their new vans (via Roadtreck acquisition) and maybe Winnegago puts this into their vans. This allows these manufacturers to delete the generator so save weight and space. I would carry my Honda 2000, in place of an existing Onan 3.6Kw from the Class C I'm looking at. I'll remove the AC for this trip, cuz there isn't shore power down there much, so the Onan isn't needed, and that weight is better applied to cargo.
 
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smiller

2008 View J (2007 NCV3 3500)
I try and follow the 50% SOC guideline and recharge from the generator when SOC gets down to 50-60%. I run the generator only long enough (about 1 hour) to put a day's worth of power back into the battery (about 30-40Ah), and then repeat the next day. As the SOC increases, the amps-in decreases and the whole charging process becomes less efficient. Starting from 50% SOC, it is better (more efficient) to charge more frequently for shorter duration, than to charge less frequently for longer duration. Once a day works for me.
Yes. Charge current during the final 10-20% of the charge period is going to be low so it's not very efficient to run a generator to a 100% state of charge,. Charging to 80% on a continuous basis isn't optimal for maximum cycle life of a FLA battery as this charge regimen will not allow proper cell equalization, but doing so for a few days or a week boondocking will generally not harm the battery bank. Just fully charge the bank to 100% with a proper 3-stage charge regimen at your next opportunity (or perform a formal cell equalization if the manufacturer recommends it) and there shouldn't be any significant impact on battery life by an occasional series of short-charges.
 

Eka

New member
Sprinters, at least the latest generation, can have the stock MB PTO for alternator or compressor added. It just costs you more when added later.
 

HighPockets

Active member
I've never heard of a "Nugget" before but I may one. Not sure I want to claim the name. I was praised by a boats'n mate in Navy boot camp for being the only one who ever cleaned the garbage can when emptying it. But while in an elementary job in an old industrial building at 1 South Main St, Houston, Texas I cleaned the window behind my work station thinking I had done a good thing but when the boss came by he fussed because it had taken 30 years for the dirt to accumulate enough to cut the glare from the sun. There was another incident in my youth but it would be too hard to explain. So I might well could have been the "Nugget" that cleaned the coffee mess.

Gene
 

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