MOD Silverleaf Charge Bridge Limitation / Workaround

[turbopilot]

I thought I would start a discussion about possible modifications to the Newmar charge splitter/battery isolator design used in SilverLeaf equipped coaches. I will lay out my thoughts for discussion but I am still looking for input and other approaches. The primary driver is that the Newmar charge splitter/battery isolator design is pretty old fashioned and prone to failure. A further driver is that this design is a bad idea with lithium batteries in the mix. Given demands of the lithium batteries it can put excessive load on the coach alternator without regulation. And lithium batteries really like tight computer controlled algorithms for charging. The present system does not do any of these things.

Here is how I understand the system works. I have pulled this from other threads. It sound plausible. So what we have is called a "Voltage Sensitive Relay" charge splitter/battery isolator design. When the engine is running Silverleaf senses a chassis battery voltage higher than the house battery (this gets messy if solar is online) then opens the charge bridge to allow the diesel engine alternator to charge the house batteries (in addition to the chassis batteries). As far as I can tell this is a full passthrough of alternator output to the batteries with no regulation or charging algorithms applied. With either battery type and a low battery SOC this can really place a high continuous demand on the alternator.

Here is what I have heard is going on from several sources and my own experience watching the charging cycles of the chassis battery.

When the engine shuts down the charge bridge closes (no flow) isolating the chassis battery from the house battery. When the chassis battery falls to 12.5 or lower for 30 seconds the charge bridge opens to allow the house batteries to charge the chassis batteries. Some sources say this may last at most an hour or until the chassis batteries hit around 13 volts. If there is a charge source on the house batteries the cycle will continue opening and closing the charge bridge based on chassis battery voltage. The constant opening and closing of the charge bridge solenoid is the cause of flaky SilverLeaf behavior without the fly back diode.

This whole system exists to do three things.

1. Open a line to the alternator when the engine is running to charge the house battery and supply DC needs of the coach.

2. Charge the chassis battery periodically when the engine is not running.

3. Provide a switch to allow current to flow from the house battery to the chassis battery in the event of a discharged chassis battery.

There is a better, more modern way to do all this.

My last New Aire on a Freightliner chassis had a big chassis battery shut off switch near the chassis batteries. Assuming the design has not changed the cable from the switch goes forward to the charge bridge solenoid mid ship. I am thinking about replacing the charge bridge solenoid with a Victron Orion - Tr Smart DC-DC charger. The largest Orion DC/DC charger is 30 amps so with a large set of lithium batteries may two or three chargers running in parallel that may be better to charge the batteries faster. The decision comes down to how fast to charge the batteries versus running the alternator at high output for a long time. These Victron chargers are controlled with Bluetooth via an app so you can elect how many chargers to keep on line.

So this would eliminate the need for the charge bridge solenoid. In the event you want to start the engine with from the house battery you would turn on the chassis battery switch otherwise it would remain closed with charging coming from the Orion DC/DC charger bypassing the switch from the alternator to the house battery.

All that is left is the ability to trickle charge the chassis battery. As I laid out above SilverLeaf is intermittently opening the charge bridge with the right voltages when the engine is off to keep the chassis battery topped off. There is a better way to do this without cycling a solenoid.

Xantrex makes an echo charger just for this purpose. This little trickle charger runs all the time keeping the chassis battery topped off using the house battery even when there is no charge source to house battery. If the coach is parked outside the chassis battery has a solar cell for charging. The solar cell in bigger in 2023/2024 models. So it is possible the solar charger may keep the chassis batteries topped if the coach is seeing the sun each day with the trickle charger.

So those are my thoughts about eliminating the charge bridge solenoid. Aside from avoiding the previous problems with the charge bridge the biggest upgrade is that lithium house batteries and the engine alternator will be treated much better. This is an important consideration.

Thoughts?

 

[turbopilot]

In the posts above I commented about the looming problems dropping lithium batteries in coaches with "old fashioned" electrical systems employing unregulated charge bridges. Here is a video that covers this subject. Upgrading the batteries from lead acid to lithium is not a simple process of just changing batteries. The electrical systems in these coaches, including the chassis electrical systems, were designed to support lead acid batteries. It appears the coach manufacturers now making lithium batteries standard equipment may not understand this problem.

I do not have access to the electrical schematics for the new coaches with standard lithium house batteries. If they are providing charging protection from the chassis alternator, it is an undocumented feature. It would be helpful if someone with one of the luxury coaches with lithium as standard equipment could check their documentation and see if there is any type of charge regulation or protection when the lithium batteries are being charged by the chassis alternator source. This is not an issue on 50 amp shore power, on generator power or solar power with a solar charger set up for lithium batteries as that power is coming into the inverter/charger and the solar controller is being regulated to support lithium battery charging. This issue is only important when the coach is rolling down the highway with the alternator as the only source of charge power and that source does not use any charge algorithm to support lithium batteries.

 

[MarkMaxPayne]

I thought I would start a discussion about possible modifications to the Newmar charge splitter/battery isolator design used in SilverLeaf equipped coaches. I will lay out my thoughts for discussion but I am still looking for input and other approaches. The primary driver is that the Newmar charge splitter/battery isolator design is pretty old fashioned and prone to failure. A further driver is that this design is a bad idea with lithium batteries in the mix. Given demands of the lithium batteries it can put excessive load on the coach alternator without regulation. And lithium batteries really like tight computer controlled algorithms for charging. The present system does not do any of these things.

Here is how I understand the system works. I have pulled this from other threads. It sound plausible. So what we have is called a "Voltage Sensitive Relay" charge splitter/battery isolator design. When the engine is running Silverleaf senses a chassis battery voltage higher than the house battery (this gets messy if solar is online) then opens the charge bridge to allow the diesel engine alternator to charge the house batteries (in addition to the chassis batteries). As far as I can tell this is a full passthrough of alternator output to the batteries with no regulation or charging algorithms applied. With either battery type and a low battery SOC this can really place a high continuous demand on the alternator.

Here is what I have heard is going on from several sources and my own experience watching the charging cycles of the chassis battery.

When the engine shuts down the charge bridge closes (no flow) isolating the chassis battery from the house battery. When the chassis battery falls to 12.5 or lower for 30 seconds the charge bridge opens to allow the house batteries to charge the chassis batteries. Some sources say this may last at most an hour or until the chassis batteries hit around 13 volts. If there is a charge source on the house batteries the cycle will continue opening and closing the charge bridge based on chassis battery voltage. The constant opening and closing of the charge bridge solenoid is the cause of flaky SilverLeaf behavior without the fly back diode.

This whole system exists to do three things.

1. Open a line to the alternator when the engine is running to charge the house battery and supply DC needs of the coach.

2. Charge the chassis battery periodically when the engine is not running.

3. Provide a switch to allow current to flow from the house battery to the chassis battery in the event of a discharged chassis battery.

There is a better, more modern way to do all this.

My last New Aire on a Freightliner chassis had a big chassis battery shut off switch near the chassis batteries. Assuming the design has not changed the cable from the switch goes forward to the charge bridge solenoid mid ship. I am thinking about replacing the charge bridge solenoid with a Victron Orion - Tr Smart DC-DC charger. The largest Orion DC/DC charger is 30 amps so with a large set of lithium batteries may two or three chargers running in parallel that may be better to charge the batteries faster. The decision comes down to how fast to charge the batteries versus running the alternator at high output for a long time. These Victron chargers are controlled with Bluetooth via an app so you can elect how many chargers to keep on line.

So this would eliminate the need for the charge bridge solenoid. In the event you want to start the engine with from the house battery you would turn on the chassis battery switch otherwise it would remain closed with charging coming from the Orion DC/DC charger bypassing the switch from the alternator to the house battery.

All that is left is the ability to trickle charge the chassis battery. As I laid out above SilverLeaf is intermittently opening the charge bridge with the right voltages when the engine is off to keep the chassis battery topped off. There is a better way to do this without cycling a solenoid.

Xantrex makes an echo charger just for this purpose. This little trickle charger runs all the time keeping the chassis battery topped off using the house battery even when there is no charge source to house battery. If the coach is parked outside the chassis battery has a solar cell for charging. The solar cell in bigger in 2023/2024 models. So it is possible the solar charger may keep the chassis batteries topped if the coach is seeing the sun each day with the trickle charger.

So those are my thoughts about eliminating the charge bridge solenoid. Aside from avoiding the previous problems with the charge bridge the biggest upgrade is that lithium house batteries and the engine alternator will be treated much better. This is an important consideration.

Thoughts?

Agree, and I share the same concerns and similar thoughts. Before Newman recently posted their latest service bulletin admitting to installing the wrong legacy solar controller on factory installed lithium coaches, I notified them of the issue and replaced their legacy lead acid solar controller with a modern one up to the task myself.

The way they simply join batteries is rather concerning, especially as I ponder adding the 3rd supposed "plug-n-play" Lithionics battery. With 2 batteries the factory solution to simply join them is worrisome at best, but with a 3rd battery added in the mix is way beyond that.

To me the ideal solution would be a 3 way solution where any one of them locks out and even electrically isolates the other 2:
1. Ability to join if you wanted to combine to start engine in an emergency where chassis is too low to start engine;
2. DC-DC to charge house from chassis alternator at set minimum RPM;
3. DC-DC to charge chassis from house, if required.
With Silverleaf simply sending voltage to engage the join solenoid under a variety of conditions (as you have outlined), I haven't thought of a way to do this without taking the Silverleaf control out of the equation.

Best,
-Mark

 

[turbopilot]

Agree, and I share the same concerns and similar thoughts. Before Newman recently posted their latest service bulletin admitting to installing the wrong legacy solar controller on factory installed lithium coaches, I notified them of the issue and replaced their legacy lead acid solar controller with a modern one up to the task myself.

The way they simply join batteries is rather concerning, especially as I ponder adding the 3rd supposed "plug-n-play" Lithionics battery. With 2 batteries the factory solution to simply join them is worrisome at best, but with a 3rd battery added in the mix is way beyond that.

To me the ideal solution would be a 3 way solution where any one of them locks out and even electrically isolates the other 2:
1. Ability to join if you wanted to combine to start engine in an emergency where chassis is too low to start engine;
2. DC-DC to charge house from chassis alternator at set minimum RPM;
3. DC-DC to charge chassis from house, if required.
With Silverleaf simply sending voltage to engage the join solenoid under a variety of conditions (as you have outlined), I haven't thought of a way to do this without taking the Silverleaf control out of the equation.

Best,
-Mark

Have you confirmed you have the same unregulated charge bridge solenoid with your lithium batteries? I suspect you do since that has always been the design.

There is a work around until we understand this situation and come up with some alternatives. We need to understand at what depleted SOC of the lithium batteries will pose a threat to the 240 amp chassis alternator. We also need to know if the alternator is rated at full continuous output indefinitely. Most are not. They may deliver 240 amps in a surge but will overheat running at the max capacity for long periods.

For now the safest thing to do is to run the generator while driving anytime the lithium SOC drops below some number ( I suggest 90%) until the lithium batteries are charged. In theory if the generator is running then the batteries are being charged via a lithium algorithm through the house charger and/or solar. Also I don't think SilverLeaf will open the charge bridge solenoid with a high voltage on the house side which you would have with the house charger engaged. We need to confirm this as well.

 

[MarkMaxPayne]

Have you confirmed you have the same unregulated charge bridge solenoid with your lithium batteries? I suspect you do since that has always been the design.

Yes, only the simple join solenoid on my 2023. To me the simplest safety solution is to disconnect the solenoid power wire triggered by the Silverleaf to join the batteries (or add a switch to that wire connection to override allowing the join to occur when I don't explicitly enable it).

Best,
-Mark

 

[turbopilot]

Yes, only the simple join solenoid on my 2023. To me the simplest safety solution is to disconnect the solenoid power wire triggered by the Silverleaf to join the batteries (or add a switch to that wire connection to override allowing the join to occur when I don't explicitly enable it).

Best,
-Mark

The only downside is that the chassis battery will not get intermittent charging from the house side while the RV is in use with the master battery switch on. That may not be an issue with enough sun since the chassis battery solar panel is bigger starting in 2023.

 

[MarkMaxPayne]

The only downside is that the chassis battery will not get intermittent charging from the house side while the RV is in use with the master battery switch on. That may not be an issue with enough sun since the chassis battery solar panel is bigger starting in 2023.

The intermittent charge from the house side was worthless on my 2023. Within days my chassis batteries would be drained too low regardless. I replaced my chassis batteries just weeks after buying my rig as they wouldn't hold a charge. Within a couple of days after replacing them I decided the vampire drains were just too much regardless of what Silverleaf wanted to do to join them to house. The dedicated chassis battery solar on my 2023 can keep the chasis topped off only when I throw both chassis breakers off while stored (at least on my Spartan chassis build).

Best,
-Mark

 

[turbopilot]

The intermittent charge from the house side was worthless on my 2023. Within days my chassis batteries would be drained too low regardless. I replaced my chassis batteries just weeks after buying my rig as they wouldn't hold a charge. Within a couple of days after replacing them I decided the vampire drains were just too much regardless of what Silverleaf wanted to do to join them to house. The dedicated chassis battery solar on my 2023 can keep the chasis topped off only when I throw both chassis breakers off while stored (at least on my Spartan chassis build).

Best,
-Mark

On my 2018 NA (Freightliner) I had 1000 watts of solar on the roof. I replaced the spring loaded Boost Battery switch with a normal switch. For storage I simply turned on the boost battery switch. That opened the charge bridge solenoid and allowed the solar panels via the solar controller to keep both chassis and house batteries at 100% SOC. More complicated now with lithium house and AGM chassis batteries. As I said above I think the solution is to remove the charge bridge solenoid, use a DC to DC charger for alternator charging of the house lithium batteries and a simple trickle charger from the house batteries to the chassis batteries.

 

[newmarokie]

OK. As you can tell by the number of posts I am a newbie. Some of the things mentioned is lithium batteries, outdoor storage, and flyback diodes. I have a '19 DS with lead acid batteries(may be AGM). It is stored inside plugged into a 50 amp service. From what I read this fixes some of the issues talked about. Are there other issues this will cause. Sold a 2021 Georgetown G7 and it was relatively (dumb)

 

[turbopilot]

OK. As you can tell by the number of posts I am a newbie. Some of the things mentioned is lithium batteries, outdoor storage, and flyback diodes. I have a '19 DS with lead acid batteries(may be AGM). It is stored inside plugged into a 50 amp service. From what I read this fixes some of the issues talked about. Are there other issues this will cause. Sold a 2021 Georgetown G7 and it was relatively (dumb)

I don't know much about the DS. The issues talked about in this thread involve what Newmar calls "luxury coaches". These coaches can have lithium and SilverLeaf. Those two systems create issues with the charge bridge solenoid.