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Old 12-06-2023, 11:18 AM   #1
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DC to DC charger install in 3500 Sprinter (2016)

I recently replaced the AGM house batteries in my 2018 Winnebago ERA with two 100Ah Renogy LiFePo batteries and have read conflicting opinions as to whether a DC to DC charger is necessary to charge the LiFePo batteries from the alternator. It seems the conservative thing is to add a DC to DC charger, so I'm planning to install a Renogy 60A.



I thinking of installing it on the back of the passenger seat base and wire it in parallel with the battery boost solenoid that is under the seat. I would appreciate hearing from anyone who has installed a DC to DC charger in a Winnebago/Sprinter about the best options for do this.
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Old 12-06-2023, 01:09 PM   #2
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I recently replaced the AGM house batteries in my 2018 Winnebago ERA with two 100Ah Renogy LiFePo batteries and have read conflicting opinions as to whether a DC to DC charger is necessary to charge the LiFePo batteries from the alternator. It seems the conservative thing is to add a DC to DC charger, so I'm planning to install a Renogy 60A.



I thinking of installing it on the back of the passenger seat base and wire it in parallel with the battery boost solenoid that is under the seat. I would appreciate hearing from anyone who has installed a DC to DC charger in a Winnebago/Sprinter about the best options for do this.
I'm going to install one in my Via, in fact my custom made cables will be here today. I am putting it on the side of the battery compartment under the step. I already installed a disconnect in the negative wire to the coil on my battery isolation solenoid and I will supply the DC-DC charger from the chassis side of the solenoid. If I ever need to use the boost function I can temporarily plug the disconnect together and start the engine, then unplug again. I can also plug it back together if I ever want or need the original charging system to be functional again. I will attach my schematic.
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Old 12-06-2023, 01:30 PM   #3
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You could also leave your BIS functional and wire the DC-DC input in series from the house side of the BIS, this way whenever you shut off the engine the BIS will open the circuit. With the Victron that I am using it has an ON-OFF function so I decided to wire it in parallel and disable the BIS in a way that was easily reversible.
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Old 12-06-2023, 02:57 PM   #4
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You could also leave your BIS functional and wire the DC-DC input in series from the house side of the BIS, this way whenever you shut off the engine the BIS will open the circuit. With the Victron that I am using it has an ON-OFF function so I decided to wire it in parallel and disable the BIS in a way that was easily reversible.

The Renogy does not have ON-OFF function - as I understand it, it has to be wired it to a D+ source. If I'm going to wire the DC-DC input from the house side of the BIS, do I remove the wire to the house battery from the solenoid and put it on the +input on the DC to DC charger and then run a new wire from the +output on the DC to DC charger to the house battery?


Also, as a D+ source for the Renogy can I run a wire from the wire that come from a IGN source to the solenoid to the DC to DC charger?
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Old 12-06-2023, 03:49 PM   #5
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The Renogy does not have ON-OFF function - as I understand it, it has to be wired it to a D+ source. If I'm going to wire the DC-DC input from the house side of the BIS, do I remove the wire to the house battery from the solenoid and put it on the +input on the DC to DC charger and then run a new wire from the +output on the DC to DC charger to the house battery?


Also, as a D+ source for the Renogy can I run a wire from the wire that come from a IGN source to the solenoid to the DC to DC charger?
Well not if it's wired like mine, the heavy cable that goes from the BIS to the battery is a two way street and also carries power back from the battery where the house circuit breakers are fed from 2 cables that are also attached to that same post on the BIS. If yours is the same you will need to remove all the cables from that post and connect them back together on an insulated junction block then add a new wire from the BIS to the battery. Or if you have room for another cable on that same post just tie in a new wire there.

If yours is wired differently post some pics. Although mine is a Sprinter it is a class A and the DC wiring is a little different.

Also on my Victron DC-DC #6 is the biggest that will fit the terminals and the battery cables are AWG-1 so even if your plan worked you may have to reduce the connection end with a junction and a smaller cable..

I don't see an issue using the ign on wire from the solenoid to tell the Renogy when to start.
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Old 12-06-2023, 04:24 PM   #6
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What I currently have is a red cable (4 AWG) coming from the starter battery to the left side of the solenoid and on the right side two red cables (a 4 AWG and a 6 AWG)- one to the house batteries and one to relay that I believe goes to the switch to shut off the house batteries to the coach. You can also see (assuming I can successfully load the pic) the paired yellow and white wires to the small terminal on the front of the solenoid. As stated in a previous post, the yellow is the 12V power to the solenoid and the white wire (labeled GDN) is paired with another white wire (labeled FM) and grounded on the back of the seat base.



If I'm understanding what you said in your last post, I can simply add another cable to the left side of the solenoid and run it to the + input on the DC to DC charger. Do I do the similar thing on the output from the DC to DC charger - that is, add another cable from the +output on the DC to DC charger and run it to the right side of the solenoid (where the existing cable is that goes to the house batteries)?


I appreciate your patience with all these questions. I'm a relative novice when it comes to RV wiring and I don't want to ruin the alternator and the new lithium batteries. I suppose I could take it to the shop but I'd rather learn how the system works.



Jack
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Old 12-06-2023, 05:05 PM   #7
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Quote:
Originally Posted by mojack View Post
What I currently have is a red cable (4 AWG) coming from the starter battery to the left side of the solenoid and on the right side two red cables (a 4 AWG and a 6 AWG)- one to the house batteries and one to relay that I believe goes to the switch to shut off the house batteries to the coach. You can also see (assuming I can successfully load the pic) the paired yellow and white wires to the small terminal on the front of the solenoid. As stated in a previous post, the yellow is the 12V power to the solenoid and the white wire (labeled GDN) is paired with another white wire (labeled FM) and grounded on the back of the seat base.



If I'm understanding what you said in your last post, I can simply add another cable to the left side of the solenoid and run it to the + input on the DC to DC charger. Do I do the similar thing on the output from the DC to DC charger - that is, add another cable from the +output on the DC to DC charger and run it to the right side of the solenoid (where the existing cable is that goes to the house batteries)?


I appreciate your patience with all these questions. I'm a relative novice when it comes to RV wiring and I don't want to ruin the alternator and the new lithium batteries. I suppose I could take it to the shop but I'd rather learn how the system works.



Jack
2018 Winnebago ERA on 2016 Sprinter

Yes, you can do that, assuming you are planning to disable the BIS. You can run your charging cable from the DC out to the other side of the BIS like you said or you can run it directly to your batteries, whichever is easier/closer. You are basically using the BIS as a junction. Then you will remove the paired wires from the small terminal on the BIS and use them for the DC-DC ignition signal.

Don't forget fusing per Renogy's recommendation. I'm using inline MRBF holders from Mouser with 60 amp MRBFs. I had short cables made to go from the batteries to the fuse holder and from the charge post on the BIS to the fuse then on to the DC-DC.

If you want nice custom cables this place does a nice job and they get them out right away and shipping is very low, I ordered 7 cables and they only charged $4 shipping. You can get them with the right size ring terminals on each end and they will even turn them 90 or 180 if you want.
https://www.batterycablesusa.com/



Yours is simpler than mine, and easier to get to.
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Old 12-07-2023, 01:35 PM   #8
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Correction on Fuses

Jack I apologize but I am working on mine today and I realized I gave you the wrong info on my fuses, they are MIDI fuses with inline MIDI fuse holders. The MRBF (marine rated battery fuse) is what I used at the battery terminal itself, 150 amp. Pictured below are my custom cables and info on the fuses and holders from Mouser
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Old 12-07-2023, 03:08 PM   #9
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Jack I apologize but I am working on mine today and I realized I gave you the wrong info on my fuses, they are MIDI fuses with inline MIDI fuse holders. The MRBF (marine rated battery fuse) is what I used at the battery terminal itself, 150 amp. Pictured below are my custom cables and info on the fuses and holders from Mouser
Brian, Thanks for the updated info on the fuses and battery cables. I take it you bought the MIDI fuses and holders separated and add them to the cable or did BatteryCablesUSA send you the cables that way?



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Old 12-07-2023, 07:25 PM   #10
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Brian, Thanks for the updated info on the fuses and battery cables. I take it you bought the MIDI fuses and holders separated and add them to the cable or did BatteryCablesUSA send you the cables that way?



Jack
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Yes all separate. I ordered the short cables that attach from the battery to the fuse holder and from the solenoid to the fuse holder with 5/16 and 10/32 ends, and the ones from the fuse holders to the Orion DC-DC with 10/32 on one end and open on the other. Then I assembled myself and torqued the fuse holder nuts to 6nm. When finished I slipped a piece of corrugated plastic wire conduit over the fuse holders to cover the exposed parts at the connectors.

If you have a place to fasten the fuse holders you can get them with mounting holes. I did not, mine are just floating.
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Old 12-08-2023, 09:29 AM   #11
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I've successfully replaced the defective Trombetta solenoid with a Cole Hersee and now I'm planning to add the Renogy DC to DC 60A charger. Based on information I've found here and on other forums my thinking is to connect the + input side of the charger to the large solenoid post with the starter battery cable, ground the - input side to a seat bolt into the chassis; the + output side of the charger would be connected to the solenoid post with the house battery cable, and ground the - output side to a seat bolt. Both positive cables will have inline fuse holders with MIDI 60A fuses.

From the D+ connector on the charger I'm thinking of running a wire to a toggle switch (mounted on the dash) and then to the small D+ terminal under the driver's seat. Similarly, splicing into the D+ wire running to the solenoid, I'd run a wire to a toggle switch and then back to the solenoid. My thinking here is that I'd like to be able to turn the charger and the solenoid off and on independently so that I can retain the batter boost function of the solenoid (with the charger turned OFF), or run the DC to DC charger (with the solenoid turned OFF), or have both OFF.

Does this sound like a workable plan or am I missing something?

Thanks,
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Old 12-08-2023, 09:49 AM   #12
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Quote:
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[FONT=&quot]I've successfully replaced the defective Trombetta solenoid with a Cole Hersee and now I'm planning to add the Renogy DC to DC 60A charger. Based on information I've found here and on other forums my thinking is to connect the + input side of the charger to the large solenoid post with the starter battery cable, ground the - input side to a seat bolt into the chassis; the + output side of the charger would be connected to the solenoid post with the house battery cable, and ground the - output side to a seat bolt. Both positive cables will have inline fuse holders with MIDI 60A fuses.


That sounds like it should work, as long as you remember to use your switches.

There is a guy on the Sprinter forum who sells custom dash switches for our Sprinter dash, you could get lighted ones and wire them so they light up when on to remind you what is on and what is off.
https://diyvan.com/products/ncv3-spr...er-with-switch

One note, if you plan on installing a shunt based battery monitor you will want all of your house grounds to go to the shunt, it's the only way the shunt will be accurate.
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Old 12-08-2023, 10:10 AM   #13
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Before you commit to 60 amp fuses what does Renogy say and what size wires are you running?
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Old 12-08-2023, 10:47 AM   #14
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I might throw in a small point to make it a little more "fool-proof"?
I find depending on me being totally right on what I do, I find making it sure I don't flip the wrong switch at the wrong time is a goo idea!
I've not looked at anything on the DC-DC charger but I might question what would happen if the switches were not totally accurate and the DC input got connected to the DC output? that appears it could happen if one of the two control switches was not right!

I might look at using a switch which would not allow both to be on at the same time.
Something like an on-center off -on switch. That would allow operating the solenoid at one end of the switch range, neither when switch was in center, and then the other option when switch was fully thrown?

A bit more complex switch but then it avoids any chance of getting the wrong things connected at the wrong time!
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Old 12-08-2023, 12:35 PM   #15
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I might throw in a small point to make it a little more "fool-proof"?
I find depending on me being totally right on what I do, I find making it sure I don't flip the wrong switch at the wrong time is a goo idea!
I've not looked at anything on the DC-DC charger but I might question what would happen if the switches were not totally accurate and the DC input got connected to the DC output? that appears it could happen if one of the two control switches was not right!

I might look at using a switch which would not allow both to be on at the same time.
Something like an on-center off -on switch. That would allow operating the solenoid at one end of the switch range, neither when switch was in center, and then the other option when switch was fully thrown?

A bit more complex switch but then it avoids any chance of getting the wrong things connected at the wrong time!
That's a good idea and would make things foolproof. I try and make as much as possible foolproof not just for myself, but for others that come after me.
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Old 12-08-2023, 01:22 PM   #16
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Before you commit to 60 amp fuses what does Renogy say and what size wires are you running?

Thanks for the link to the switches in your prior reply. That's what I was hoping to find. They recommend 4 AWG and 90A fuse on the input side and 6 AWG and 75A fuse on the output side, so that's what I'll use. Thanks for pointing that out to me.



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Old 12-08-2023, 02:28 PM   #17
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I might throw in a small point to make it a little more "fool-proof"?
I find depending on me being totally right on what I do, I find making it sure I don't flip the wrong switch at the wrong time is a goo idea!
I've not looked at anything on the DC-DC charger but I might question what would happen if the switches were not totally accurate and the DC input got connected to the DC output? that appears it could happen if one of the two control switches was not right!

I might look at using a switch which would not allow both to be on at the same time.
Something like an on-center off -on switch. That would allow operating the solenoid at one end of the switch range, neither when switch was in center, and then the other option when switch was fully thrown?

A bit more complex switch but then it avoids any chance of getting the wrong things connected at the wrong time!

I agree with the idea of making things foolproof but I don't understand the how the DC input could get connected to the DC output. Are you suggesting this would be the case if BOTH the DC to DC charger switch was ON and the solenoid switch was ON?


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Old 12-08-2023, 03:58 PM   #18
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Yes, I think that is what we are each thinking.
The idea is that IF both were left on it might look like this:
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My concern might be what this does? Not knowing much about the details of the dc-dc, I just would not expect us to want to connect the in and out of any item. to connect directly.
But if we were not really careful, it might happen that both get left ON at the same time?

Is that a real problem or one that my cynical mind might have imagined?
Possibly a good time to ask the folks who build the DC-DC?
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Old 12-08-2023, 04:30 PM   #19
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Yes, I think that is what we are each thinking.
The idea is that IF both were left on it might look like this:
Attachment 188042

My concern might be what this does? Not knowing much about the details of the dc-dc, I just would not expect us to want to connect the in and out of any item. to connect directly.
But if we were not really careful, it might happen that both get left ON at the same time?

Is that a real problem or one that my cynical mind might have imagined?
Possibly a good time to ask the folks who build the DC-DC?

The diagram helps me understand what you're getting at. I'll have to investigate that further. Thanks.



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Old 12-08-2023, 05:21 PM   #20
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There are a couple more ways to prevent both from accidentally being on at the same time. One is to wire in a relay using the NC contacts to provide the ground for your BIS, then connect the coil to the switch for the Renogy so when the Renogy is switched on it energize the relay and interrupts the ground to the BIS and disables it. Another solution is to simply put a switch in the ground wire to the BIS and place the switch in an out of the way place, like under the seat. You'll only ever need it for the boost and you may never need it. On mine I just cut the ground wire and attached plug in connectors to each end and labeled it "put together for BIS" so if I ever need the BIS to function I will have to open the compartment and plug the wires together. I didn't want a switch that someone could flip just because.
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