I'm going to install 2 lifepo4 batteries in my motorhome. I know that I need a dc to dc charger. I also know that my alternator cannot exceed 40 amps. My first question is where does it get wired, just between the alternator and the battery? My second is really advice on which one. I see victron has an 18 amp and a 30 amp. I am going to have 340 ah of batteries. I don't know what I don't know.
Wiring confusion.
- Thread starter Daledevon
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Yuphorya
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I'm looking into this right now. While there are units from Victron and Sterling, they are fairly pricey. I recently found this device and trying to get more information on it.
www.bogartengineering.com
On all DC-DC chargers, it's basically one side is wired to Starter batteries w/ Alternator and then the other side is direct to your house battery bank.
High Efficiency Solar Charger Controller
Compact, powerful and smart solar charger controller for RV, off-grid. 30 Amps 12V and 24V charger for Gel, AGM, lead acid, lithium LFP. WiFi remote capable
On all DC-DC chargers, it's basically one side is wired to Starter batteries w/ Alternator and then the other side is direct to your house battery bank.
I do not recomend a OEM alternator to charge LiFePo battery. But basicly as posted above, The starter battery goes to the right side of the B-to-B and the house battery goes to the other right side of the B-to-B. Most installers use too small of cables and often forget the fuses.
Yuphorya
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Seems like a very common question about charging the LFP battery system with the vehicle while driving. From what I've been reading it seems an OEM alternator with no sort of regulation is a bad thing but if there is a current limiting device it is fine. Just wondering if I'm missing something.
Which is why @Yuphorya is on the right track with this (below) line of thinking, right?
My limited understanding is that so long as the current limiting device limits the current to a level the alternator can handle, it is okay. Various ways to accomplish this but a current limiting DC-DC ("battery to battery") charger is the most common.
DaleDevon, does you motorhome right now have system set-up to charge the house batteries? If so you need to look at that too (and figure out a good way to disable it).
Yes I you want to use a Battery to Battery charger that can handle lithium. Also, when you install it - wire a switch to turn it on and off to the drivers seat. That way if you don't want the batteries completely full (Lithium does not like to be completely full), you can tell it to stop charging with the flick of a switch.
The Victron unit I believe you want is the Orion-Tr-SmartDC-DC charger - non-isolated. It can handle lithium charging. At 30Amps of charging - if your house batteries are very empty - it will take about 10 hours to completely charge it. How long it will really take will depend on how much power you use. 340ah is a LOT of power for a MotorHome.
Yes I you want to use a Battery to Battery charger that can handle lithium. Also, when you install it - wire a switch to turn it on and off to the drivers seat. That way if you don't want the batteries completely full (Lithium does not like to be completely full), you can tell it to stop charging with the flick of a switch.
The Victron unit I believe you want is the Orion-Tr-SmartDC-DC charger - non-isolated. It can handle lithium charging. At 30Amps of charging - if your house batteries are very empty - it will take about 10 hours to completely charge it. How long it will really take will depend on how much power you use. 340ah is a LOT of power for a MotorHome.
Zil can you clarify what you are saying. Are you giving a general disclaimer about due diligence the dangers/risks of hooking up an LFP bank to an alternator directly? Or are you specifically cautioning against what is being discussed in this thread and saying you have observed failures even where a lithium compatible DC-DC charger is used (like those from Sterling, Victron, etc)?
Are you going to build a 12V or a 24V battery pack?
For a 12V battery pack get the Orion-TR 12/12-30 Smart Charger
For a 24V battery pack get the Orion-TR 12/24-15 Smart Charger
Both will stay under your 40A alternator limit and will deliver the same amount of power (watts) to your battery pack. Nice thing about the Orion-TR Smart is if you have a BMV-712 battery monitor it will control the Orion over Bluetooth (wirelessly) using Victron-Connect.
My system has a 24V@280AH battery pack and I am using the Orion-TR 12/24-15 Smart Charger. It takes a lot of driving to fully charge the battery with just alternator power, but that is just one of the charge sources I have in my system. I also have a Victron Multiplus for shore power and a Victron MPPT 100/20 Smart Solar). All 3 charge sources are controlled by the BMV-712 (2 by relay output and one by Victron-Connect).
In addition stopping charge at a predetermined state of charge, the BMV-712 will also cutoff charging if the battery temperature drops below -5 degrees C.
For a vehicle system you can use either an isolated or a non-isolated charge controller (the non-isolated is a bit cheaper). The isolated version is really only required when you are charging a trailer house system from a tow vehicle alternator.
Hi
HaldorEE can you explain why the isolated version is the correct choice for a towed trailer?
I am setting up such a system now and have been unable to find that answer from Victron.
Thanks,
Mike
Here are a couple of threads that may help.
What do isolated and non isolated mean with respect to DC/DC chargers?
I'm preparing to swap out my AGMs for LifePo4s and Updating all the sources for charging my batteries. I've upgraded my panels and added a Victron MPPT that supports LifePo4. I'm upgrading the Progressive Dynamics 4045 Might Mini so it will support LifePo4. Then I started wondering about how the...
diysolarforum.com
24V to 12V Converter Options: Isolated vs Non-isolated
I originally intended to parallel two Orion TR 24/12/20's to cover the almost 40A 12V DC loads I could require (w everything on all at once ... unlikely though). As I was about to purchase them, noticed that there's an Orion TR 24/12/70 but it's not isolated. Since I've recently decided to...
diysolarforum.com
In order for fuses and circuit breakers to protect against wiring shorted to the chassis, you have to connect the battery negative to the vehicle chassis. This is the same reason why in AC wiring the white neutral wire is connected to the safety ground.
However, you only want to make this connection at a single place, otherwise some of the return current can flow through chassis ground instead of the negative wire. This is not a great idea since current flow through dissimilar metals can cause corrosion. Plus if the current path is interrupted (by opening a car door for example), this can cause unexpected operation.
In automotive electrical systems, the negative terminal of the battery is connected to chassis ground. When you install a house electrical system that uses alternator charging you don't need to add a connection from the house battery negative to chassis ground, in fact you shouldn't do this unless you use an isolated DC-DC charge controller.
There are two situations where an isolated DC-DC charger makes sense. When adding alternator charging to an existing house electrical system that already has a negative to chassis ground connection. Or in a trailer that must connect the house negative to chassis ground even when connected to the tow electrical system which also has a negative to chassis ground connection.
Systems in a trailer that use alternator charging have to work both when connected to the tow vehicle electrical system and when disconnected. An isolated DC-DC charger controller permits you to ground the trailer system negative independently of the starter battery negative to chassis ground connection.
You can always use an isolated DC-DC charger. The only reason why you wouldn't is because the non-isolated versions are cheaper, and you are installing the house system from scratch and are willing to use the starter system negative to chassis ground connection.
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Can't believe I got this so wrong.
The MPPT Smart Solar is the one that is controlled wirelessly by the BMV-712. With the Orion-TR you have to use the relay output of the BMV-712.
It's not like I didn't know this. I guess I was just wishing that Victron would add this feature so bad that my subconscious was convinced it is a thing.
Not yet.
Yeah I really don't know why Victron went through all the trouble of creating a new line of 'smart' product without better integrating it into the rest of its ecosystem--after all integration is one of their strong points. Its one of their newer products, you would think it would be more tightly integrated.
There is a Smart Orion, which makes the other one "dumb" I guess. On another thread I suggested the smart version, simply because it gave you the ability to program it. If Victron didn't integrate it, shame on them.
The Orion-TR Smart adds Bluetooth for monitor and control. It currently does not also also support Victron.Connect via Blue Tooth like the MPPT Smart Solar does. I bet they plan on doing this, but things happen at whatever pace they happen. I understand that Victron has to put out the biggest fires and grease the squeakiest wheels first.
At least the Orion has the contact closure input to control charging so you can use the relay output of the BMV-712 for this. The MPPT SmartSolar doesn't have a contact closure input so it desperately needed the Victron.Connect functionality over Blue Tooth. Hopefully all Blue Tooth capable Victron equipment will fully support Victron.Connect eventually.
