Disconnect Alternator from House Battery Charge

[robo44]

I wanted to disconnect my alternator from charging my house batteries while I drive. Is there a simple connection or fuse located in the Battery Control Center or other location that I can simply disconnect?
2019 FR3 33DS

[Frameman]

Why ???

[formerFR]

why ?? (#2!)

[AudiDudi]

If I turn off my battery disconnect switch, the alternator does not charge the house batteries. Disconnecting the main ground wire on the battery bank would also do it.

[14apex]

Why disconnect??

[robo44]

Why some ask.. I just upgraded to lithium house batteries and solar. The 2 reasons i have are
1. Per Battleborn, RV alternator cannot fully charge batteries (Alternator charges at a lower voltage.) I do not ant to run the risk of damage to my Alternator or batteries if possible without having a solution. The solution recommended to me was to buy a DC-DC converter to take care of issue. I dont have the $400 plus for the recommended part at this time.

2. Our solar can keep up with our demand, & we have a generator with the proper converter that can charge the lithium batteries if needed.

My thinking is to disconnect the current Alternator from the Control Center so I do not charge the batteries OR potentially damage one or the other UNTIL I get the funds or push comes to shove and I feel I need the alternator to charge while I drive.

To change the alternator on my FR3 was just priced at $500 for the Alternator & $200 Labor. I dont want to pat that either.

Im open to suggestions just trying not to break, or damage items if I can avoid it.

[ScottBrownstein]

Put a switch on the BCC isolation solenoid coil. If it can't energize it won't charge the house from the alternator.

[14apex]

Thanks for the explanation, Robo44...this is way above my expertise, but extremely interesting in any event. ScottBrownstein's suggestion sure sounds like a good option -- otherwise the master disconnect as also suggested above should do it? Please report back as time evolves to let us know how the system is working out for you -- it sure sounds great!

[Steve-W]

There is also a circuit breaker under the hood. It is mounted just beyond the grill. It should be visible as soon as you open the hood in the front left corner. That is the connection from the Chassis system to the house system. Either open the C/B (some have a button to do this) or disconnect the heavy cable from the C/B to the chassis battery.

[robo44]

Thanks I will take a look at that.
Appreciate the suggestion

[formerFR]

Originally Posted by robo44

...
1. Per Battleborn, RV alternator cannot fully charge batteries (Alternator charges at a lower voltage.) I do not ant to run the risk of damage to my Alternator or batteries...

this is only saying that an alternator is not a battery charger, and is not designed to try to 'fully' charge your batteries, any batteries for that matter, even our FLA Flooded Lead Acid batteries found in any RV....

you're reading something different, as this is NOT saying NOT to allow the alternator to charge your battery bank, as if that somehow can 'damage' them, but just simply that the charging is not going to ever get to a 'full charge' as you would see on a true battery charger.

Use your batteries, use the alternator, use the solar, use the battery charger... all is well, you don't 'need' to do anything different.
There are plenty of RVs with these batteries and don't 'disconnect' anything.

[babock]

The big problem is the BIM. If the Lithium batteries are fully charged, the voltage is high enough that it will allow the BIM to connect the lithium batteries to the chassis battery. This is not a desirable situation. This can even happen if the lithium batteries are fully charged and there is no charge source on.

The fact of the matter is that the alternator will never really supply much current to the lithium batteries. Just disconnecting or putting in a switch that you could connect in an emergency to charge the chassis battery is the best solution

You can buy a DC to DC converter for way less than $400. Here are two options.

https://smile.amazon.com/Renogy-Batt...y&sr=8-1-fkmr1

https://smile.amazon.com/Renogy-Batt...8-1-fkmr1&th=1

[robo44]

Originally Posted by babock

The big problem is the BIM. If the Lithium batteries are fully charged, the voltage is high enough that it will allow the BIM to connect the lithium batteries to the chassis battery. This is not a desirable situation. This can even happen if the lithium batteries are fully charged and there is no charge source on.

The fact of the matter is that the alternator will never really supply much current to the lithium batteries. Just disconnecting or putting in a switch that you could connect in an emergency to charge the chassis battery is the best solution

You can buy a DC to DC converter for way less than $400. Here are two options.

https://smile.amazon.com/Renogy-Batt...y&sr=8-1-fkmr1

https://smile.amazon.com/Renogy-Batt...8-1-fkmr1&th=1

Thank you for your advice and link

[rk06382]

Originally Posted by robo44

Why some ask.. I just upgraded to lithium house batteries and solar. The 2 reasons i have are
1. Per Battleborn, RV alternator cannot fully charge batteries (Alternator charges at a lower voltage.) I do not ant to run the risk of damage to my Alternator or batteries if possible without having a solution. The solution recommended to me was to buy a DC-DC converter to take care of issue. I dont have the $400 plus for the recommended part at this time.

2. Our solar can keep up with our demand, & we have a generator with the proper converter that can charge the lithium batteries if needed.

My thinking is to disconnect the current Alternator from the Control Center so I do not charge the batteries OR potentially damage one or the other UNTIL I get the funds or push comes to shove and I feel I need the alternator to charge while I drive.

To change the alternator on my FR3 was just priced at $500 for the Alternator & $200 Labor. I dont want to pat that either.

Im open to suggestions just trying not to break, or damage items if I can avoid it.

I have been using Battle Born for over a year. I have had no problems charging my Battle Born batteries with my alternator. It is true the alternator will not charge to 100% SOC, but the alternator will charge to 80-90%.

Image is from: How to Find Happiness With LiFePO4 (Lithium-Ion) Batteries

I take SOC the rest of the way with the solar or shore power. When I talked to Battle Born last year, I asked the question about the alternator. I was told with four Battle Born batteries it would not be a problem. With the Victron BMV-712 I have seen 86-93 amps @ 13.59-13.78 volts. This is inside the charge curve above. The solar was also on at the same time.




I have had no problems with the alternator but if you know of something, I would like to know.

[robo44]

Thanks Robert -
I guess what has me (maybe being over cautious) is Battleborn also send me info on my system links to a DC-DC converter to use. I then began to read more about it and was left with a cautious approach to save my alternator.

What struck me in a few posts was the words “self-destruct” & the cost of replacing my alternator if I do not regulate using a DC-DC converter or other.

“ A Lithium Ion battery can put a lot of load on an alternator and have it working flat out for an extended time. There might need to be some way to limit the demand to prevent the alternator from self-destructing.
Lithium batteries have a maximum charge current and a recommended charge current. RV alternator it would be wise to consider some kind of limiting to prevent it from self-destructing when charging Lithium Batteries at high output for an extended time.
DC DC converter has a vibration sensor to turn it on automatically when the engine is running. It takes the input voltage and changes it to whatever voltage is required by the Lithium Battery, and in the process limits it to the programmed value, up to a maximum of 40 Amps”

Anyway, thank you for your thoughts… I am leaning towards a Renogy DC-DC converter at a more pleasant price point with a fairly good reputation, &/or possible switch that I can isolate my house batteries while driving.

[babock]

Originally Posted by robo44

DC DC converter has a vibration sensor to turn it on automatically when the engine is running. It takes the input voltage and changes it to whatever voltage is required by the Lithium Battery, and in the process limits it to the programmed value, up to a maximum of 40 Amps”

Anyway, thank you for your thoughts… I am leaning towards a Renogy DC-DC converter at a more pleasant price point with a fairly good reputation, &/or possible switch that I can isolate my house batteries while driving.

What the Renogy uses is a control signal to turn on the the converter by either the ignition or a voltage signal of your choice.

[ScottBrownstein]

Originally Posted by rk06382

Attachment 211065

Attachment 211074

I have had no problems with the alternator but if you know of something, I would like to know.

Admittedly I have 4 FLA batteries in my house bank and regularly see 14.2 or more when running down the road. Looks like the alternator is well within the lithium charge profile anyway. However, simple low current switch on the isolator solenoid primary coil would allow you to enable/disable charging from the alternator and still allow you to boost start whenever necessary.

[babock]

The problem with charging from the alternator is not how high the voltage is but if you have very large gauge cables between your alternator and your lithium batteries, it could force the alternator to go 100% duty for a LONG time. If your cables are a smaller gauge, that actually helps limit the current since the voltage drop works in your favor and the lower voltage at the lithium batteries limits the amount of current.

With my Ford F-150, the charge current to my Lithium batteries is never more than 2A since the wiring between the alternator, through the 7 pin connector and then to the trailer itself is very small gauge.

If you really want the best way to charge your lithiums while running, the DC to DC converter is the way to go. It will limit the current to 20A or 40A with a Renogy model depending on which one you pick. You will also want to mount it close to the lithium batteries so you have minimal voltage drop. Voltage drop is what kills your charging capability. One reason why all my charge sources, converter, solar controller are within 2 feet of my batteries.

[rk06382]

Originally Posted by robo44

Thanks Robert -
I guess what has me (maybe being over cautious) is Battleborn also send me info on my system links to a DC-DC converter to use. I then began to read more about it and was left with a cautious approach to save my alternator.

What struck me in a few posts was the words “self-destruct” & the cost of replacing my alternator if I do not regulate using a DC-DC converter or other.

“ A Lithium Ion battery can put a lot of load on an alternator and have it working flat out for an extended time. There might need to be some way to limit the demand to prevent the alternator from self-destructing.
Lithium batteries have a maximum charge current and a recommended charge current. RV alternator it would be wise to consider some kind of limiting to prevent it from self-destructing when charging Lithium Batteries at high output for an extended time.
DC DC converter has a vibration sensor to turn it on automatically when the engine is running. It takes the input voltage and changes it to whatever voltage is required by the Lithium Battery, and in the process limits it to the programmed value, up to a maximum of 40 Amps”

Anyway, thank you for your thoughts… I am leaning towards a Renogy DC-DC converter at a more pleasant price point with a fairly good reputation, &/or possible switch that I can isolate my house batteries while driving.

Call Battle Born and ask about the Precision Circuits Inc. LiFePO4 Battery Isolation Manager. ($172.10)

Under normal charging conditions, the BIM will connect for 15 minutes every 35 minutes. That means that the BIM will connect for 15 minutes, disconnect for 20 minutes, and repeat this cycle until the coach battery is charged.
If the coach battery resting voltage exceeds 13.4V than the BIM will disconnect. A resting voltage greater than 13.4V indicates a fully charged battery. Note that “resting voltage” means that no current is flowing to the coach battery.
The BIM will disconnect if the alternator voltage exceeds 14.4V. This protects the coach battery from over charging.
The BIM will disconnect if the voltage difference between the alternator and the coach battery is less than 0.1V. If the voltage difference is too low, then there is a negligible charging current, and no need to connect to the coach battery
The BIM will disconnect if the alternator voltage drops below 13.3V. If the alternator voltage is too low, than it cannot adequately charge the coach battery, so there is no reason to connect. Made in the USA.