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Old 03-19-2018, 07:22 PM   #281
huytnankai
 
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Default Re: AGM battery charging from alternator

I have a good news for anyone who is looking to charge their AGM battery with alternator.
I applied this on my 2016 Sprinter,it works like a charm. Charge really fast to over 13 volt with some high way driving.

And it is very SIMPLE!

I bought four exactly same battery, dual purpose AGM, 100Ah each. Replace the original starting battery with one of them, and leave the rest three in the coach, connect all in parallel.

The myth about alternator cannot charge well is not because " the fancy controller it has". It is because when you try to mix batteries of different size, type, age, etc!!! Only batteries of the same age, type, capacity can be effectively charged together. Otherwise, you will end up with one battery voltage raise relatively fast, and trick the controller to "turn down" charging current while other batteries are still hungry. You do need to realize during charing mode, the same voltage could mean different state of charge. It is not as easy as the "voltage - state of charge" table looks like. That's when everything is settled down. Ps, I do have a PhD in Electrical Engineering.

Hope it helps!
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Old 03-19-2018, 09:31 PM   #282
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Default Re: AGM battery charging from alternator

Quote:
Originally Posted by huytnankai View Post
I have a good news for anyone who is looking to charge their AGM battery with alternator.
I applied this on my 2016 Sprinter,it works like a charm. Charge really fast to over 13 volt with some high way driving.

And it is very SIMPLE!

I bought four exactly same battery, dual purpose AGM, 100Ah each. Replace the original starting battery with one of them, and leave the rest three in the coach, connect all in parallel.

The myth about alternator cannot charge well is not because " the fancy controller it has". It is because when you try to mix batteries of different size, type, age, etc!!! Only batteries of the same age, type, capacity can be effectively charged together. Otherwise, you will end up with one battery voltage raise relatively fast, and trick the controller to "turn down" charging current while other batteries are still hungry. You do need to realize during charing mode, the same voltage could mean different state of charge. It is not as easy as the "voltage - state of charge" table looks like. That's when everything is settled down. Ps, I do have a PhD in Electrical Engineering.

Hope it helps!
Do you have an I4 or the V6 engine? As far as I am aware, no one on this list has reported issues with direct charging from the V6. The "fancy controller" is limited to the I4.
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Old 03-20-2018, 01:53 AM   #283
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Default Re: AGM battery charging from alternator

I have charged AGMs for over ten years on RVs and trucks using only the Alternator of a duramax Chev. I have charged up to 4 batts at one time while driving. My new 2017 Sprinter has the option that I can increase the idle speed of the engine, so long slow idle problems will not happen. Many ways to skin this cat, but KISS is best. The more items you add to an electrical system the more potential for problems. If you go with a second alternator dedicated to the house battery, you should be good. That is the path I'm going.
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Old 03-20-2018, 02:35 PM   #284
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Default Re: AGM battery charging from alternator

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Originally Posted by avanti View Post
Do you have an I4 or the V6 engine? As far as I am aware, no one on this list has reported issues with direct charging from the V6. The "fancy controller" is limited to the I4.
I have I4
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Old 04-06-2018, 03:54 AM   #285
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Default Re: AGM battery charging from alternator

Definitely have learned a lot from this thread. I have a 2017 V6 and am working out my electrical system and in particular the charging system. I have no doubt that the OEM alternator is capable of bulk charging an aux battery bank at high current based on the data provided here. What I and obviously others on this thread are trying to figure out is why MB specifies limiting the charging current to aux batteries at 40A.

If it is a matter of alternator life or gas mileage that is one thing. I am just not willing to risk somehow damaging the van electrical system.

So my question is has anyone gotten an answer on this specifically? I am considering calling the support number on the Upfitter portal to ask. Anyone have any idea how good there support is if you do call? Thanks.
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Old 04-06-2018, 04:21 AM   #286
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Default Re: AGM battery charging from alternator

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Originally Posted by ChadBuilds View Post
What I and obviously others on this thread are trying to figure out is why MB specifies limiting the charging current to aux batteries at 40A.
Here's my earlier analysis of the 40A recommendation:
https://sprinter-source.com/forum/sh...866#post639866

IMO, there are two reasons to limit charging current:

1) Protect the wiring from overcurrent. This is unlikely to be the cause, because it would not make sense to offer a 180A or 220A alternator, nor place a 300A fusible link in the Y-cable... if only 40A of additional current could be taken safely.

2) Maintain a proper charging voltage. Batteries need to be charged at a sufficiently high voltage in order to charge them in a reasonable amount of time. As the current output of the alternator increases, the regulator will maintain the voltage at ~14.4V at the alternator terminals. However, at higher currents the resistance of the Y-cable introduces additional voltage drop between the alternator and the battery.

My guess is that MB did the math on worst case vehicle electrical loads, chose an acceptable minimum charging voltage (maybe 13.8V? 13.2V?), took the resistance of the Y-cable and figured the available surplus current while maintaining that minimum voltage. (If) the answer was around 40 amps, they probably rounded it to 40 and called it a day.

The final clue to me that the worry is about charging rather than damage is the last sentence from the body builder guide: "A suitable alternator must be selected to ensure that the overall charging balance is positive."



Are you likely to damage the van electrical system by taking more than 40 amps? In my opinion, no. But if you're doing it consistently, you may fail to fully charge the starter battery.. especially if you regularly run it down listening to the radio with the engine off.

"The basic vehicle may be damaged" sounds like CYA boilerplate translated from German. The message is- don't build more than 40A of additional charging current into your Sprinter-based RV or shuttle bus design, while relying on the Y-cable to deliver a sufficient charging voltage to the batteries. If you're worried about it, running a separate cable to the alternator should permit you to go beyond 40A without negatively affecting charging of the starter battery.


Last edited by sprint2freedom; 04-06-2018 at 04:29 AM.
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Old 04-11-2018, 01:51 AM   #287
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Default Re: AGM battery charging from alternator

I have an update on my system - I have a 2013 with the 220a alternator; I installed the CTEK DUAL250S and SmartPass (2x300ah 6v Lifetime AGMís); together they have the capacity for up to 100a. I have seen high 90ís on the Victron for short bursts when Iím down in the 60%ís, most often it seems to sit in the 60-70 range for the first hour, then tapering down as the batteries get filled up. So far, Iíve got about two years on the system, and havenít seen anything indicating any problems.

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Old 04-12-2018, 03:18 AM   #288
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Default Re: AGM battery charging from alternator

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Originally Posted by GSWatson View Post
I have an update on my system - I have a 2013 with the 220a alternator; I installed the CTEK DUAL250S and SmartPass (2x300ah 6v Lifetime AGMís); together they have the capacity for up to 100a. I have seen high 90ís on the Victron for short bursts when Iím down in the 60%ís, most often it seems to sit in the 60-70 range for the first hour, then tapering down as the batteries get filled up. So far, Iíve got about two years on the system, and havenít seen anything indicating any problems.

Old photo of setup -


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Thanks for the update. Are you tied into the connection under the seat after the infamous Y harness or did you run straight off the alternator?


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Old 04-13-2018, 01:35 AM   #289
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Default Re: AGM battery charging from alternator

I used the spare slot on the fuse block on the start battery, and ran cable from there.


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