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DC to DC charger install - does this work?
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krusovice
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PostPosted: Wed Dec 18, 2024 11:05 am    Post subject: DC to DC charger install - does this work? Reply with quote

I'm still working on getting my new-to-me EVC ready for next year. I need a new house battery, and a way to charge it from the alternator.

I found this Renogy DC to DC charger that I think will work for me.

https://offgridstores.com/products/renogy-12v-20a-...8223497268

Hat tip to this thread in the Vanagon section: https://www.thesamba.com/vw/forum/viewtopic.php?t=798420

My plan is to get a LiFEpo4 battery to go with it. I don't have the battery yet.

And my original combiner (the solenoid under the hood) doesn't work right now.

So the questions:
-I think this should not be installed under hood. Can I install it in the battery compartment in the back? I'd use the existing wiring to that box. Will this work?

-If replace the original solenoid, or replace it with a more modern combiner, could I skip the D+ wire to tell the DC to DC charger to start charging?

-If I'm not on the right track, what's a better solution?

thanks
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kourt
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PostPosted: Wed Dec 18, 2024 11:22 am    Post subject: Re: DC to DC charger install - does this work? Reply with quote

The Renogy product you list is the combiner/isolator. It detects whether or not the engine is running by voltage change.

That means you would install this Renogy product in the back of the van near the aux battery, feed it with a positive wire from the ignition (there is one serving the battery box from the factory) and remove the isolator in the engine bay. Replace the isolator with a fuse.

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krusovice
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PostPosted: Wed Dec 18, 2024 11:46 am    Post subject: Re: DC to DC charger install - does this work? Reply with quote

Thanks. I was trying to avoid running a wire from the front to the back but if there’s already one there, that’s better

Which wire is it? I only see the 12v positive. Don’t I need a 2nd wire to trigger the device?

https://www.winnebago.com/Files/Files/Winnebago/Resources/Diagram/2001/131677.pdf
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kourt
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PostPosted: Wed Dec 18, 2024 12:10 pm    Post subject: Re: DC to DC charger install - does this work? Reply with quote

That's the wire. The 8ga black wire that runs from the isolator in the engine bay to the isolated stud attached to the furnace support frame is the wire. The Rengoy will detect when the engine is running from that wire. No separate wire is needed.

Find the manuals for this Renogy device and make sure a separate D+ wire is not needed. If it requires a D+ wire, find another DCDC charger. All the modern DCDC chargers determine if the engine is running based on a > 13VDC condition, and do not require a D+ wire to assist the charger.

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krusovice
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PostPosted: Wed Dec 18, 2024 12:14 pm    Post subject: Re: DC to DC charger install - does this work? Reply with quote

That’s the problem. I’m pretty sure this won’t detect 13v (and does require the D+ wire).

Time to shop some more.

https://cdn.shopify.com/s/files/1/0551/8462/1620/f...cf4d15.pdf
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kourt
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PostPosted: Wed Dec 18, 2024 12:41 pm    Post subject: Re: DC to DC charger install - does this work? Reply with quote

Here's a few that don't require D+ wires:

https://www.amazon.com/gp/product/B093BB5JKF

https://www.amazon.com/gp/product/B0CWYWQGBF

https://www.amazon.com/gp/product/B0851TPKV7

I owned all three of these. Had each one in my EVC for a while. The Victrons were the best. The Renogy was good but not great. None required D+ wires.

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krusovice
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PostPosted: Wed Dec 18, 2024 8:49 pm    Post subject: Re: DC to DC charger install - does this work? Reply with quote

Thanks kourt. That helped a lot.

I'm leaning towards this unit: Renogy 40A DC-DC Battery Charger with MPPT
https://www.renogy.com/renogy-40a-dc-dc-battery-ch...o8jPdvQCsv

I like:
-it's a Dc to DC charger that doesn't require a wire to tell it the alternator is running
-it will also allow solar input. I'm not ready for that yet, but I will be at some point

I'd like bluetooth as well, but it's not a deal breaker. I have a voltage meter connected to the house battery so I can tell from that what state the battery is in.

Is 40amps too much for the alternator/wiring? I think it must be OK because the existing wiring has 40amp breakers.

Am I reading correctly that this will only charge the house battery from the starter battery if the voltage indicates the alternator is running?

Finally, just to be sure, the EVC does NOT have a smart alternator, right?
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PostPosted: Thu Dec 19, 2024 5:15 am    Post subject: Re: DC to DC charger install - does this work? Reply with quote

krusovice wrote:

I'd like bluetooth as well, but it's not a deal breaker. I have a voltage meter connected to the house battery so I can tell from that what state the battery is in.


As your future state includes a LiFePo4 battery, you may want to reconsider using a standard voltmeter as a measure of its state of charge. Unlike lead acid or AGM batteries which will drop voltage pretty early on in their discharge cycles, LiFePo4 batteries will show normal voltage almost until they are at 0% state of charge.
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kourt
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PostPosted: Thu Dec 19, 2024 8:40 am    Post subject: Re: DC to DC charger install - does this work? Reply with quote

The EVC does not have a smart alternator.

I found the Bluetooth on the DCDC chargers to be extremely helpful, in that I could determine the charge state of my battery from inside my house, and make config changes to the parameters for the DCDC in the field. The Victrons are very configurable. The Renogy is somewhat configurable, but not quite as flexible as the Victrons.

The Victrons allow you to dial down the amperage draw from the alternator, and also specify the voltage at which it detects whether the car is running or not. Both of these adjustable parameters put the Victron at a much greater value than the Renogy.

I found the combined MPPT function in the Renogy product to be a problem. It is better to have the solar charge controller in a separate device.

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JWaugh
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PostPosted: Mon Dec 23, 2024 11:27 pm    Post subject: Re: DC to DC charger install - does this work? Reply with quote

Recent upgrade to LiFeP4 200amp/hr. Renogy dc/dc charger does use trigger wire from ignition to old solenoid switch wire. 32 feet from starter battery to battery box @ 40 amps calls for #4 wire. The #8 will get pretty hot under charge. Replaced the old Magnatek shore power converter at the same time.
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PostPosted: Sun Feb 16, 2025 5:52 pm    Post subject: Re: DC to DC charger install - does this work? Reply with quote

Im Curious how your dc to dc charger works along with the onboard magnatek charger? I have a the renogy 30amp dc to dc and lifepo4 battery ready to install but how do I avoid potential issues of the magnatek and the new battery both supplying dc power to the accessories when the van is hooked up to shore power/A/C?

Thanks Much.
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krusovice
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PostPosted: Mon Feb 17, 2025 6:07 pm    Post subject: Re: DC to DC charger install - does this work? Reply with quote

Well, you’d have to disconnect the magnatec otherwise it will charge the battery when the vehicle is plugged in to shore power.

The dc to dc charger works when the vehicle is running (charging from the alternator).

I’ve not looked carefully enough at the wiring but I think it would attempt to charge from both AC and DC if you ran the engine while plugged in to shore power, though I can’t imagine why you’d want to do that.
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PostPosted: Tue Feb 18, 2025 9:20 am    Post subject: Re: DC to DC charger install - does this work? Reply with quote

XanderFree wrote:
Im Curious how your dc to dc charger works along with the onboard magnatek charger? I have a the renogy 30amp dc to dc and lifepo4 battery ready to install but how do I avoid potential issues of the magnatek and the new battery both supplying dc power to the accessories when the van is hooked up to shore power/A/C?

Thanks Much.


I don't know of anybody that kept the magnatek after installing the DC-DC. Most installs I've seen just delete it and don't have shore power charging the battery. On mine, the shore power only goes to the 110 outlets now- not connected to battery at all. House batteries charge off solar and alternator only.
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PostPosted: Tue Feb 18, 2025 10:33 pm    Post subject: Re: DC to DC charger install - does this work? Reply with quote

I have Weekender, so no magnatek. However, if you were to replace the magnatek (which I would highly recommend since there are much better options available today) with something like a Victron AC-DC charger and install a Victron DC-DC charger I can tell you it works just fine to have both charging a LiFePO4 battery at the same time. I've done it. Of course, this is a silly way to charge a battery but it works just fine.

What concerns are there having both charging at the same time? Maybe I'm missing something.
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PostPosted: Wed Feb 19, 2025 6:24 am    Post subject: Re: DC to DC charger install - does this work? Reply with quote

I have been making a very deliberate effort to not act like a know-it-all in life, which is part of why I've been posting on thesamba less.

That said, I decided to make another entry on this thread and want to emphasize- I am not an electrical wizard and the following is basically internet knowledge and limited personal experience only.

I would absolutely not use the Magnatek to charge a LiPo/Lithium battery if you were going to put one in as the new battery. It's 30 year old technology and not compatible. My understanding is you would be shortening the life of your new, expensive battery and could actually create a safety hazard.

If somebody is an actual wizard and knows I am wrong, feel free to correct.
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PostPosted: Wed Feb 19, 2025 6:42 am    Post subject: Re: DC to DC charger install - does this work? Reply with quote

I'm not a wizard, but I like to enable knowitalls on the internet.

Throw out the Magnatek. Throw it as far as you can chuck it.

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PostPosted: Wed Feb 19, 2025 7:56 pm    Post subject: Re: DC to DC charger install - does this work? Reply with quote

Sorry I’m off topic but I really appreciate the perspective and opinions of others on this forum. I don’t have to blindly follow what is said but I’m richer for the input and better able to figure out next steps because of the people on this forum.

I just wish we were half as active as the vanagon forum so we could get even more opinions, insight, and experiences.
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krusovice
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PostPosted: Sat Mar 01, 2025 2:09 pm    Post subject: Re: DC to DC charger install - does this work? SOLUTION Reply with quote

I think I've decided what to order. I'll place the DC/DC charger in the rear battery box, and the fuse under the hood. I think this allows the least invasive install. I'm still using the lead acid battery, but will eventually upgrade to LiFePo4 when the time comes.

I'm going to go with this Isolated DC to DC charger with bluetooth.

Victron 12/12 30amp.

https://www.amazon.com/gp/product/B086Q8YNJZ/ref=ox_sc_act_title_1?smid=A21C4U5X700J66&psc=1

Under the hood, I'll remove the original solenoid, and replace it with a 40amp fuse. (There are 2 other 40 amp fuses installed by Winnebago so I figure that's a good size to go with. I plan to use the original wiring.)

https://www.amazon.com/gp/product/B086Q8YNJZ/ref=ox_sc_act_title_1?smid=A21C4U5X700J66&psc=1

Before I click "buy" am I missing something? Thanks for all the advice over my "struggle" deciding.
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PostPosted: Sun Mar 02, 2025 10:42 am    Post subject: Re: DC to DC charger install - does this work? Reply with quote

You mention the Victron unit that you are interested in getting is isolated, but the link is for the non-isolated. I suspect you meant non-isolated since it is cheaper and you don't need the negative isolation. The isolated units are more commonly used when there is no common chassis ground like a fiberglass boat.

I have the non-isolated Orion Tr Smart and it works just as described. However, if I could I would have gotten the Orion XS. I have a 24V battery and the XS is not yet available in 24V. It's definitely more expensive but something to look into.

Also, you have not said, but do you have a way to monitor your system? A voltmeter is pretty minimal, and mostly worthless with LifFePO4. Being able to see current is just as important as voltage. Something like a Victron BMS 712? In fact, I could say if you are thinking about upgrading your original system a monitor is the first piece of equipment you should be getting.
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PostPosted: Sun Mar 02, 2025 12:18 pm    Post subject: Re: DC to DC charger install - does this work? Reply with quote

It's more money, but this is the baseline I recommend now:

DCDC:

https://www.amazon.com/dp/B0CWYWQGBF

Monitor:

https://www.amazon.com/dp/B075RTSTKS

These two will network together and communicate.

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