Question Isolating coach batteries from house batteries.

[lostinfla]

Since I've changed to lithium for house power, I've been toying with the idea of not using the engine alternator to charge the house bank as it will last much longer than the daily drive to power what we use before plugging in again, then the inverter takes over the program. I have a lithium BIM installed and wondered if removing and isolating the coach line side from it would do the job, or eliminate it all together. What say ye?

 

[Rollin Ollen]

Since I've changed to lithium for house power, I've been toying with the idea of not using the engine alternator to charge the house bank as it will last much longer than the daily drive to power what we use before plugging in again, then the inverter takes over the program. I have a lithium BIM installed and wondered if removing and isolating the coach line side from it would do the job, or eliminate it all together. What say ye?

I, too, am interested in the replies and how difficult will taking the charge away from the alternator?

 

[lostinfla]

A far as I can see, the function of the LBIM is that it joins the chassis and house batteries for charging with a limit of 15 min on and 15 min off so as to not overwork the alternator, and for use as a boost, which is connecting both together in the same way. I would think it would only be a matter of removing the house battery lead from the unit, therefore charge would be going only to the chassis batteries from the alternator, The other way to do it would be to remove the feed wire at the chassis battery bank. I'll do a little more research and give it a try this week.

 

[Richpatty]

There should be no issue removing the line coming from the LiBim from the house batteries. What I have wanted to do is put in a heavy duty line switch in the battery compartment so I can choose when I want the alternator to charge the batteries or not. This would also preserve the “Boost” feature if you needed to bridge the batteries if the chassis die for some reason.

 

[lostinfla]

Excellent idea Rich. Thanks!
Just put a switch in my Amazon cart.

 

[Neal]

Personally, I'll wait for a failure before I change anything. Have we heard of anyone with an alternator failure due to LiFePO4 batteries? I'll gladly replace the alternator and then make necessary changes if needed. However, I also have solar so my house batteries can be maintained by solar vs. alternator. But IMHO these alternators are a lot more rugged than we think.

 

[Richpatty]

I called freightliner some time ago and asked them about alternator failures, in particular related to lithium house batteries and they had not heard of any issues.
So I do tend to agree that these are pretty tough units. And to be honest, I have not seen the lithiums pull more than 100 amps across (per the shunt).

 

[lostinfla]

My issue is, while traveling we usually run the generator to keep the ACs ahead of the heat, so the inverter is able to charge the house bank. I didn't want the alternator trying to join in and possibly have an issue with two charge/ battery type systems not playing well together. I'm going to install another disconnect to be able to keep them isolated unless needed at some point.

 

[Richpatty]

Welcome, The charging and power system will prevent dual charging from the generator and alternator.

I don’t think that is true…at least not on my rig. I don’t see how the alternator would stop sending power to the batteries just because the generator is sending power from the battery charger…. On mine, I would think the solar would also be contributing to the charging.

What would it stop this from happening?

 

[redbaron]

Welcome, The charging and power system will prevent dual charging from the generator and alternator.

Incorrect.

The systems are unaware of each other.

 

[redbaron]

My issue is, while traveling we usually run the generator to keep the ACs ahead of the heat, so the inverter is able to charge the house bank. I didn't want the alternator trying to join in and possibly have an issue with two charge/ battery type systems not playing well together. I'm going to install another disconnect to be able to keep them isolated unless needed at some point.

There is no problem with charging from multiple sources as long as each source has a method to stop charging.

The inverter stops charging based on a voltage reading.

The LiBM is controlled via a relay. This relay is controlled by silver leaf or another mechanism. That control device reads the house battery and determines when the solenoid is activated. In addition to being active from the solenoid, the LiBM also has controls to prevent charging based on time. So if it contributes 10 minutes to charging while your generator is also contributing, the total voltage improvement is recognized by both systems.

Another point is let’s assume 5 minutes into is 10 minutes of running the control system (silver leaf for example) sees the voltage as achieved or high, it will close the solenoid. That too will stop the alternator from providing charge.