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I’m not trying to compare solar vs honda generators. My question would be to most of the forum members who know the math charging hours amp hours etc. how long would it take to charge 4 agm battery’s under normal daily use with a honda 1000 watt generator vs the changing rate of the optional solar panel that comes with the Oliver. Math is not my strong point. The simplest explanation would help. Thanks

Grant  2022 GMC Denali 2500 HD 2019  Elite 11😎

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I have the same question but from my initial research it looks like it depends (as always) on several factors but the crux of it comes down to you knowing some details about how much current each of the two charging methods supply (Solar Controller  vs. Onboard Controller ) :

1) Solar Controller - what's the maximum charge rate available for the AGM profile.   
     (example Zamp controllers can be 30Amps or 40A depending on the model installed?)
2) Onboard Controller - from shore power or generator - implies using the onboard Progressive Dynamics charge controller which could be the  45A or  60A unit...depends on your model)

AGM batteries generally should be recharged at a minimum of 20% of their total AH rating. 
Example a 200AH battery bulk charge rate should be ideally...200x.2= 40A...
if your charge controller can only push 20A the time to recharge will double.



First Pass EXAMPLE: Actual Numbers may be 40% more time than this....
Let's say we had 4 , 200AH AGM's...800AH total capacity, now sitting at 50% discharge.
So to take them from  50%  discharged state to recharge we need to generate 400AH total charge.

Solar - Assumes perfect sun, and controller running at full 30A:
400AH/30A = 13.3 HRS  (Actual due to solar and charge inefficiencies will be maybe 22 HR or more)

Generator - Assumes the 45A Progressive Dynamics Controller
400AH/45A = 8.8 HRS (again...it's more likely about 13 - 16 Hrs due to battery inefficiencies in recharging)

... which ever charge controller can deliver the power UP TO the 20% rate would be the fastest....


Now - if you want to go into more specifics for YOUR system then consider:

* The specific individual AGM battery specs (total AH rating) is it a 200AH battery x 4 .  You'll need to know the individual AH ratings?
* Assuming the 4 batteries are connected in a series/parallel setup.
* The state of the batteries at start of charge (example start charging from 50% charged state)
* You'll need to know the charge rating available from the various chargers in play:
    Each solar charger has a specific profile and amperage rating for AGM batteries...
    The on board charge controller (when using the Generator) has it's own charge rating....

Here's a base article about how fast AGM's can be charged. 

If I have time in the next day or two...I'll do a calculation on my own exact setup and post a reply.

Here's a resource for AGM Charging as well: 

battery charging.docx




Edited by ctshort09
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2019 Elite II (Hull 505 - Galway Girl - August 7, 2019 Delivery) 
Tow Vehicle: 2021 F350 King Ranch, FX4, MaxTow Package, 10 Speed, 3.55 Rear Axle
Batteries Upgrade: Dual 315GTX Lithionics Lithiums - 630AH Total
Inverter/Charger: Xantrex 2000Pro 

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I guess I'm not sure that what you're asking is a useful metric to judge your decision, since that's not how you use your system; i.e., running the batteries all the way down and then recharging them 100%. From discussions a few years back, it seems like most people in an Ollie use around 70-80Ah per day.  That includes a little inverter use for hair dryers and microwave, along with lighting, heat, etc.  No AC, obviously.  

That usage means roughly 2 hours plugged in to shore power or a generator, or an average sunny day with the 360w solar package.  

Generators are certainly the more reliable choice.  To increase the reliability of your panels, you either have to add more solar, so that you charge faster, or more batteries, so that you can go longer without a charge.  Or both.

Having said that, ctshort answered most of your question, and I'd only add that for solar, you'll never actually see 30A, even at noon in July in Tuscon, and certainly not for the entire day.  The general rule of thumb, which I've found to be fairly accurate, is to plan to get 20-30Ah per 100w of solar per day.  So for 360w, somewhere between 70 and 108 Ah, which, per above, is adequate for most owners, at least on sunny days, and with ~200AH of usable battery storage, means that most can plan on 3 cloudy days without worrying about recharging by some other means.  

I'd also say that for lead acid batteries, having both a generator and solar is a good combination.  Run the generator for an hour or so in the AM to get a big chunk of the bulk charging done, and then let the solar panels take care of the slower absorption and float.  

Edited by Overland
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Don't forget the 26% federal income tax credit for solar in 2020.  That includes all parts and labor.

Last year's 30% credit covered our generator!


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Andrew, Carianne and Buffy | San Diego, CA

2019 Legacy Elite II Hull #468 "California Burrito" | 2018 BMW x5 35d 

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I'll second what Overland said, as I  have said it before in other posts. The most effective use of the fossil fuel generator is in the morning, at bulk charge, when we need the honda 1000 genset boost. 45 minutes to an hour usually gets us out of bulk charge mode in shoulder season camping . We let the solar panels take care of the rest. On a crappy day, we might run the generator again for 30 minutes to an hour in the evening,  if it's going to be a cold night, and we're in the mid 80s on percentage of battery.

Agm batteries have many advantages.  They're sealed, no fumes, less sulfation.  (Great for me, as they're under my head in our Elite I, 2008.) They don't leak, even if damaged. Less susceptible to vibrations. Charge faster than flooded, in bulk mode, especially. Supposedly can be discharged further than flooded.

I get twitchy when we get into the 70s percentage of full, as I  want the expensive batteries to get their full / best life. Any battery, agm or flooded, lasts longer if not regularly discharged to the limit, and not overcharged, either. Keeping the batteries discharged to 70 to 80 per cent should prolong their life. Cycling is based on full discharge rating, so....longer life if you don't fully discharge. (Full discharge depends on your battery type. Often 50 per cent. I  try to not go that low.)

We have a dc danfoss/ secop compressor fridge now, so I  really watch the battery states, more than I did when we had a three way. 

The big night time power user for us, as shoulder season campers, is the furnace fan. Noisy, and power greedy. In our older, original Elites, it's at the foot of the bed, under the kitchen drawer,  unlike the newer trailers, where it's up forward, under the north seat.   So, not only does it suck a lot of power, but it wakes me up every time it kicks in. Paul swears he doesn't hear it, but I do. So, I  set the furnace to the lowest setting, and add a blanket. That helps. Both with warmrh, and battery useage.

We have two agm 12v, 105 ah batteries,  so not the same configuration the op was asking about.  




Edited by SeaDawg

2008 Ram 1500 4 × 4

2008 Oliver Elite, Hull #12



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Thanks for the responses.  Would it be right to say it doesn’t mater what you charge with, solar or generator. The on board charging regulator charges at one rate only, and that rate determines how long it takes to change the batteries ? 

Grant  2022 GMC Denali 2500 HD 2019  Elite 11😎

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44 minutes ago, Landrover said:

Thanks for the responses.  Would it be right to say it doesn’t mater what you charge with, solar or generator. The on board charging regulator charges at one rate only, and that rate determines how long it takes to change the batteries ? 

Yes and no. You actually have two charge controllers in the trailer, solar and shore power. Each one charges the batteries independently, based on what each controller knows about the state of the batteries, which in this case is the battery voltage. Each controller has its own limits on how quickly it can charge. Fortunately, neither charger is powerful enough to damage the batteries even when both are working at their maximum. 
You can opt for third party systems, which gather additional information about battery state and usage, and which coordinate the charging between solar and shore power; but while a few of us have those and enjoy some advantages, they aren’t necessary. 

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21 hours ago, Overland said:

Sherry do you only have 210Ah total, or is that usable?

210 ah, total. The battery tray in the 2008 Elite I only holds two group 27 batteries. And that's obviously not all useable. 

It's ok. With some conservation (maybe read power miser controls), and good monitoring tools,  we've boondocked successfully for 12 years. 😃 

2008 Ram 1500 4 × 4

2008 Oliver Elite, Hull #12



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