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Old 11-24-2017, 02:57 PM   #21
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Just a few general notes:

UG = auxiliary alternator plus inverter.
Regulator programming includes limiting the auxiliary alternator output to protect alternator.
Solar charging can be way more than a trickle charge. 10, 20, or 30 times more easily obtainable.
Deep cycle lead acid batteries are specifically designed for deep draw downs - eg: golf cart

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I wonder if it is necessary to limit input to the house batteries in GeorgeRa's setup if it is a stock alternator + chassis battery + 230AH house batteries.

I'd first determine how often a setup like that results in more than 40A at the house batteries and then determine the duration at more than 40A to see if any limiting is needed.

If limiting is needed then would the $$$ be better spent on an additional battery? (assuming battery bank longevity is the goal)
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Old 11-24-2017, 03:55 PM   #22
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Good points from Marko and definitions.

In GeorgeRa's application, because it is a factory alternator use installation, I do think it needs to be limited, as much to protect the alternator as the batteries.

If his AGMs are like ours in acceptance rate, they will likely accept 100 amps or more for quite a while, if it is available, which would be a bit much for the batteries if they can handle the .4C ours can, or 92 amps in GeorgeRa's case, but would also likley get the alternator quite hot, when another 20-30 amps are added to run the van chassis, plus whatever other power is being used in the coach like frigs (especially propane ones) or charging up stuff.

The big difference, IMO, when you charge off the van alternator is that you lose the good stuff that the underhood generator system provides. This is mostly not the alternator and it's capacity, but the control from the regulator. It gives overtemp protection for the alternator and the batteries, plus a multistep charge profile, so you aren't hitting your batteries with many hours of full charge voltage on long drives if you leave full, or almost full. You lose all of those things if you use the van alternator without a DC to DC charger in the line, although you can get the battery overcharge protection back with a disconnecting style separator that you can control yourself.

The only other way I can think of to limit the current would be to put an adjustable field control on the alternator so you could turn it down when needed, but then you lose voltage also in most cases. If there is a good way to turn down just the amps, for lower cost that the DC-DC charger, you could do that and get most of the benefit by doing that and having a disconnect.

I am certainly not against charging off the van alternator, as I think the probably well over 90% of users would be just fine with that setup for up to 200-250ah of batteries. The continuing change to AGM from wet cells has changed the dynamics of it a bit, I think, as the AGMs will accept enough amps to heat up themselves and alternator, where wet cells would take considerably less amps.

Personally, if I had the choice, I would use a DC-DC charger even for a engine generator setup. That way you could use an internally regulated alternator, no external regulator, and be able to match the output to what batteries you have by the size of the DC-DC charger. I would have built our system that way, if I could have found a DC-DC charger large enough for what we need, I think. We achieved a bit better charge control with our system, but it is a manual control, and most folks want/need it to take care of itself.
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Old 11-24-2017, 04:46 PM   #23
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Just remember that modern vehicles have highly-engineered intelligent charging systems intended to save fuel and improve performance. Generally speaking, taking large amounts of power from them will produce unpredictable results. Mercedes forbids upfitters from taking more than a small amount of power from the engine charging system. DIY folks often get away with ignoring these specs, but I do not think it is a good idea, and probably will become even less so in the future.

One of the reasons I got a second engine alternator was because I was getting disappointing charging performance from my 2014 Sprinter chassis alternator. I must say that I feel better about taking these issues out of the equation.
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Old 11-24-2017, 05:02 PM   #24
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Agree with Avanti, especially on Sprinters.

Have they come out with limitation numbers for the Promasters and Transits? I don't recall ever seeing any.
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Old 11-24-2017, 08:41 PM   #25
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.

Maybe the 48v alternator/generator is the solution?
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Old 11-24-2017, 09:38 PM   #26
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Thank you all for the helpful discussion.

My van is 2013 Sprinter. The MB cut-off relay, the one between the auxiliary battery and the alternator, and 2 AWG wiring can support up to 100A. The 2 AGM Fullriver batteries should take at the bulk stage from 0.15-0.35 X C20 = 35A - 80A charge at 77°F, less at higher temperatures. http://resources.fullriverbattery.co.../batteries.pdf

With battery deeply discharged charging current exceeds the 80A maximum, and in several minutes, it drops down. I have no control of charge rate with higher battery temperatures, with hot battery the overcharging could be happening keeping me completely unaware.

It works fine now but I would like to have some limits on the charging current for my peace of mind. The 40A limit I picked is arbitrary, if it is a simple current cut-off it should be OK, with DC to DC charger the limit could be higher, 50-60A or even 80A.

Awhile back I purchased a Magnum ME-SBC battery disconnect which has 25A limit, my plan was to insert it between the cut-off relay and house batteries to prevent overcharging the starting battery. But 25A max is too limiting. Smart Battery Combiner | Magnum Dimensions. This unit could be set for connect/disconnect/reconnect different voltages, I think it was a premature purchase.

2013 Sprinter can provide higher alternator current than 2014 and up so no issue up to 100A.

Battery to battery charger is certainly best option to provide correct charging profile. Sterling is an option and it is popular, Kisae 30/50A B>B chargers DMT-1250 - Kisae Technology is another option.

One of the potential option would be to use an adjustable current sensing relay to override the MB cut-off relay. So, for these few times when current is too high the MB relay would be triggered off until reset, but, there would be no alternator charging until batteries will get charged enough by solar or AC charger. AS1 Current Sensing Relay | NK Technologies

I need to make up my mind, which way to go. Doing over again I would pick a dual power source charger to take my 300W PV and the alternator inputs. One of the scenario is doing nothing, as it was stated, I need to figure out how often the alternator exceed the charging current and if rarely doing nothing could be my best choice. Spending $400-500 of the DC>DC charge controller to extend batteries' life perhaps is not justifiable.
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Old 11-25-2017, 04:14 PM   #27
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Quote:
Originally Posted by booster View Post
https://www.amazon.com/Sterling-ProC...F6F574XDJGBYDS

Sterling ProCharge-B Battery to Battery Charger | 12 Volts In - 12 Volts 50 Amps Out
Would a Sterling B2B like this also stop alternator charging when the house battery reaches full?
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Old 11-25-2017, 04:49 PM   #28
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Quote:
Originally Posted by Saldar View Post
Would a Sterling B2B like this also stop alternator charging when the house battery reaches full?
It is a full feature smart charger, so within the limits of it's algorithm, it will take the batteries to float when they are full, just like a shore or solar charger. That is a very big benefit IMO.
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Old 11-25-2017, 06:10 PM   #29
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Thinking out loud .

How about getting a solar charge controller which is a DC to DC device instead of a pricey Sterling or Kisae. For example, this 40A MPPT Solar Charge Controller Tracer 4210A. I sent these folks an email with this question. I could be wrong, but a DC to DC is a DC to DC chage controller. The MPPT is useless in this case. The source resistance is different, but this shouldn’t make much difference.

https://www.aliexpress.com/item/40A-...StoreLevelAB=2
Based on my recent positive experince form the purchase of the headset radio from Aliexpress I am willing to experiment.

This is another one by Xantrex C Series PWM Charge Controller for $200 https://www.solarpanelstore.com/sola...ntrex_c60.html

Or, disconnect the cut-off relay on connect alternator positive to my Morningstar MPPT 45 solar controller input with solar panels being disconnected if it would be necessary.

What am I missing?
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Old 11-25-2017, 07:12 PM   #30
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Quote:
Originally Posted by GeorgeRa View Post
Thinking out loud .

How about getting a solar charge controller which is a DC to DC device instead of a pricey Sterling or Kisae. For example, this 40A MPPT Solar Charge Controller Tracer 4210A. I sent these folks an email with this question. I could be wrong, but a DC to DC is a DC to DC chage controller. The MPPT is useless in this case. The source resistance is different, but this shouldn’t make much difference.

https://www.aliexpress.com/item/40A-...StoreLevelAB=2
Based on my recent positive experince form the purchase of the headset radio from Aliexpress I am willing to experiment.

This is another one by Xantrex C Series PWM Charge Controller for $200 https://www.solarpanelstore.com/sola...ntrex_c60.html

Or, disconnect the cut-off relay on connect alternator positive to my Morningstar MPPT 45 solar controller input with solar panels being disconnected if it would be necessary.

What am I missing?

I asked this question over at Sprinter Source a few years ago (you participated in the thread). Graphite Dave responded as follows:

Quote:
A few years ago I called Morningstar with the same question. They said no. No way to control the amount of amps from alternator with a low house battery.
If this is accurate and I understand him correctly, I guess they are saying that the design of the solar controllers are dependent on the assumption of limited current availability from the solar panels.
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