Lithium Batteries / voltstart.

[cruising7388]

Originally Posted by gregmchugh

It has another purpose, it is needed to excite the alternator or solar charger (or shore power charging in this new configuration) when you need to power the battery heaters if the Ecotreks are shut down in cold weather. Without the AGM in place there would be no way to get power to the battery heaters to warm the batteries up to operating temperature without moving the van to a warmer spot or supplying external heating to the Ecotrek modules. It would seem that the battery heaters get power on the charge port before the relay so that they can operate no matter the state of the Ecotreks.

RT indicated to me that in the event of BMS shutdown, the charging sources remain hot to trot and the AGM is provided solely to kick start the battery out of its coma so it can accept charging. Does shifting the inverter/charger connection point alter this scenario?

You think that the heaters get their power upstream of the shut down relay? If this is true, when there is no alternator or shore power functioning, with a sustained <32F temp, what prevents the batteries from eventually totally discharging?

[booster]

Originally Posted by cruising7388

RT indicated to me that in the event of BMS shutdown, the charging sources remain hot to trot and the AGM is provided solely to kick start the battery out of its coma so it can accept charging. Does shifting the inverter/charger connection point alter this scenario?

You think that the heaters get their power upstream of the shut down relay? If this is true, when there is no alternator or shore power functioning, with a sustained <32F temp, what prevents the batteries from eventually totally discharging?

I think Roadtrek may have fed you a line on the AGM and charging sources. I don't know the brands or specs on their shore chargers or solar controllers, but essentially every one I have looked at needed a battery in the system to be active. The Nations alternator, run by the Balmar regulator positively needs a battery in the system to control the voltage. With the lithiums offlinel all those sources need to see the AGM battery.

[cruising7388]

Originally Posted by booster

I think Roadtrek may have fed you a line on the AGM and charging sources. I don't know the brands or specs on their shore chargers or solar controllers, but essentially every one I have looked at needed a battery in the system to be active. The Nations alternator, run by the Balmar regulator positively needs a battery in the system to control the voltage. With the lithiums offlinel all those sources need to see the AGM battery.

No question that the Nations alternator needs a battery load to deliver power but that's because any modern alternator, needs this. But I think it has nothing to do with excitation, per se, and more to do with load sensing. Sure, the alternator needs a voltage source to get initial liftoff but historically, once up and running, when sustaining a battery disconnect, rather than shutting down it would voltage spike and continue to deliver suds and as often as not, its diode junctions would puncture from excessive peak inverse voltage.

What prevents this these days is that if battery physically separates (or sustains a BMS shut down), the engine computer (or the Balmar regulator) recognizes this condition and shuts down the alternator field windings to stabilize the alternator before it goes into orbit. But to restore field winding current, I don't think any further excitation is necessary. All it has to see is the resumption of a battery load.

Consequently, I think RT's explanation is accurate, that the AGM is there to stimulate the BMS into waking up a shut down battery long enough to satisfy the charging source. What perplexes me is how long it took them to figure that out and why they chose to use a limited life group 24 battery for this rather than a charged capacitor network that would easily outlive the life of the battery.

[avanti]

Originally Posted by cruising7388

What prevents this these days is that if battery physically separates (or sustains a BMS shut down), the engine computer (or the Balmar regulator) recognizes this condition and shuts down the alternator field windings to stabilize the alternator before it goes into orbit.

Beware: The Balmar MC-614 regulator does NOT have such protection. The following is from its installation manual:

Many LiFePO4 batteries have a Battery Management System (BMS) that may disconnect the battery from the alternator as a protective action or when charging is complete. The regulator must be shut down before the battery is disconnected .Running an alternator without a battery will damage the alternator and may damage any attached system. This is doubly true if the battery can be disconnected during
high current charging, causing a load dump. The load dump can easily cause a high voltage spike
which will destroy the alternator’s recti er, at minimum. This is not a warrantable failure. To reiterate: THE ALTERNATOR MUST BE SHUT DOWN BEFORE DISCONNECTING THE BATTERY. THE ONLY SAFE WAY TO SHUT DOWN THE ALTERNATOR IS TO TURN OFF THE REGULATOR. The preferred method of turning off the regulator is disconnecting the regulator’s ignition (brown) wire, but if used as
an EMERGENCY ONLY shutdown, disconnecting the regulator’s power input (red) wire in addition to the ignition wire has a very low chance of damaging the regulator.

[booster]

Originally Posted by cruising7388

No question that the Nations alternator needs a battery load to deliver power but that's because any modern alternator, needs this. But I think it has nothing to do with excitation, per se, and more to do with load sensing. Sure, the alternator needs a voltage source to get initial liftoff but historically, once up and running, when sustaining a battery disconnect, rather than shutting down it would voltage spike and continue to deliver suds and as often as not, its diode junctions would puncture from excessive peak inverse voltage.

What prevents this these days is that if battery physically separates (or sustains a BMS shut down), the engine computer (or the Balmar regulator) recognizes this condition and shuts down the alternator field windings to stabilize the alternator before it goes into orbit. But to restore field winding current, I don't think any further excitation is necessary. All it has to see is the resumption of a battery load.

Consequently, I think RT's explanation is accurate, that the AGM is there to stimulate the BMS into waking up a shut down battery long enough to satisfy the charging source. What perplexes me is how long it took them to figure that out and why they chose to use a limited life group 24 battery for this rather than a charged capacitor network that would easily outlive the life of the battery.

The battery needs to be in the system, and stay in the system in nearly every alternator system, as the regulator needs to see the battery for voltage reference and load to drain spikes. Same with solar and most shore chargers. From everything I have ever heard, you should never run an alternator without a battery reference, same with solar and shore chargers as they either won't run or they will go nuts on voltage.

[cruising7388]

Originally Posted by avanti

Beware: The Balmar MC-614 regulator does NOT have such protection. The following is from its installation manual:

Thanks for the heads up! I wasn't aware that the Balmar regulator did not have this protection which doesn't reflect well on me since I have hat manual in my files. But it begs this question: the addition of the AGM was a field change only after a couple of years into Etrek production. How did the Nations alternator survive with a BMS shut down during that period it wasn't included?

[gregmchugh]

Originally Posted by cruising7388

Thanks for the heads up! I wasn't aware that the Balmar regulator did not have this protection which doesn't reflect well on me since I have hat manual in my files. But it begs this question: the addition of the AGM was a field change only after a couple of years into Etrek production. How did the Nations alternator survive with a BMS shut down during that period it wasn't included?

As I recall, the addition of the AGM to the Ecotrek system was done pretty soon after the introduction of the Ecotrek. But my memory is not that good these days so I may be mistaken...

The original Etreks were all AGM so not an issue there...

[gregmchugh]

Originally Posted by cruising7388

RT indicated to me that in the event of BMS shutdown, the charging sources remain hot to trot and the AGM is provided solely to kick start the battery out of its coma so it can accept charging. Does shifting the inverter/charger connection point alter this scenario?

You think that the heaters get their power upstream of the shut down relay? If this is true, when there is no alternator or shore power functioning, with a sustained <32F temp, what prevents the batteries from eventually totally discharging?

The battery heaters seem to be powered at the charge port so the relay is not going to effect it. The procedure for initiating battery warming was to simply start the engine and the underhood generator would power the heaters, as I recall...

Not sure what your last sentence means???

[cruising7388]

Originally Posted by gregmchugh

The battery heaters seem to be powered at the charge port so the relay is not going to effect it. The procedure for initiating battery warming was to simply start the engine and the underhood generator would power the heaters, as I recall...

Not sure what your last sentence means???

Perhaps it's confusion of definitions. As I think I understand your description:


Assuming the vehicle at rest without shore power,

1. If required, the battery heaters will get power from the battery even if the BMS has shut down the charge and discharge ports because the the heaters are connected to the battery upstream of the relay that controls the charge port.

2. If the battery temp goes below 32F, the BMS will turn the heaters on regardless of the battery SOC.

3. My question: if this is the way it works, what prevents a sustained below 32F environment from continuing to drain the battery to total discharge?

[gregmchugh]

Originally Posted by cruising7388

Perhaps it's confusion of definitions. As I think I understand your description:


Assuming the vehicle at rest without shore power,

1. If required, the battery heaters will get power from the battery even if the BMS has shut down the charge and discharge ports because the the heaters are connected to the battery upstream of the relay that controls the charge port.

2. If the battery temp goes below 32F, the BMS will turn the heaters on regardless of the battery SOC.

3. My question: if this is the way it works, what prevents a sustained below 32F environment from continuing to drain the battery to total discharge?

By “the battery “, I guess you are referring to the AGM battery or are you referring to the lithium battery?

In the scenario where the van is cold with the Ecotreks off and at a low enough temperature that the Ecotreks need to be heated before they will start up, the procedure has always called for using the underhood generator to power the heaters (and with the new wiring configuration for the inverter it would seem that shore power would also work). Given this scenario, it would appear that the battery heaters are only powered when there is a charge voltage level (higher than the normal AGM voltage) and the AGM will not simply discharge by powering the battery heaters when the engine is not running.

Once the Ecotreks are online, the battery heaters can be powered from the lithium cells even when there are no charge sources and in this case I guess there is a scenario where it is cold enough that the battery heaters might operate often enough to discharge the lithium cells to the point where the BMS would shut down the Ecotrek due to reaching the minimum SOC limit but the normal loads are typically larger than the battery heater load so the discharge is more due to normal loads than the battery heaters. Recovery would probably require starting the engine or plugging into shore power to recharge the lithium cells. Solar charging could also be happening in these scenarios and if the charge current was adequate it may be enough to power the battery heaters. I knew the wattage of the Ecotrek battery heaters at one time but I don’t recall what it was other than the fact that it is not a very large load...

[cruising7388]

Originally Posted by gregmchugh

By “the battery “, I guess you are referring to the AGM battery or are you referring to the lithium battery?

The lithium battery

[Davydd]

Why does no one else using lithium ion batteries not using an AGM battery in the system as Roadtrek does?

[booster]

Originally Posted by Davydd

Why does no one else using lithium ion batteries not using an AGM battery in the system as Roadtrek does?

Because they did it right it in the first place and didn't need to put a big AGM bandaid on them.

[gregmchugh]

Originally Posted by booster

Because they did it right it in the first place and didn't need to put a big AGM bandaid on them.

Yes, very true.

There is still the issue of powering electric battery heating pads from the underhood generator or shore power or solar for a cold van with the lithium battery bank below operating temperature which could still be a reason for keeping a small AGM battery in the system.

Winnebago is using cabin heated air to warm the lithium battery bank.

What was the solution that ARV decided to implement, I don’t recall the details?

[wincrasher]

Word has it that Volta offers the DC heating pads on their battery bank, but WGO did not opt for it. I wish they had decided otherwise, as the cost can't be that much. Having the Truma heat the pack is a good idea, but I'd like the redundancy of the pads.

[cruising7388]

Originally Posted by Davydd

Why does no one else using lithium ion batteries not using an AGM battery in the system as Roadtrek does?

This is what I think, subject to correction:

Every lithium battery that is shut down by its BMS needs a module that can coax the battery out of its coma and reopen a charging path long enough to satisfy a recharging source that there's something there to charge.

I think there are three different ways of accomplishing this:

1. Since the shut down lithium battery still has some residual charge, manually sneak past it's protection and use the residual charge briefly to reopen the charging path long enough to satisfy charging requirements.

2. Use a standby charged capacitor bank to provide this stimulation.

3. Install a standby (AGM) battery common to the alternator, battery charger and solar controller and employ it to reset the lithium battery.

I believe the Xantrex system uses a charged standby capacitor network which for all intents and purposes is just a small battery. I don't know how ARV addresses this or how it's done with the Volta setup. RT employs a beefy group 24 battery which seems to me to be overkill for the task it performs; has a shorter practical life span than solid state alternatives and since this AGM is common to the other charging sources, it's always being charged as if it's a lithium battery.

[wincrasher]

Volta works on SOC, not voltage. It will go into shutdown at 20% SOC if I understand correctly. That leaves plenty of reserve to restart the battery. It's still interlocked on temp though, and will not restart until it reaches it's set point.

If I understand correctly, Roadtrek didn't start out with an extra AGM battery. It was a kludge to address it's issues with Voltstart not triggering to recharge the lithiums. Problem is their BMS is such an energy hog, it was draining the batteries down to very low voltages.

The Volta autostart is also working based off SOC as I understand it and not from reading a voltage.

[cruising7388]

Originally Posted by wincrasher

Volta works on SOC, not voltage. It will go into shutdown at 20% SOC if I understand correctly. That leaves plenty of reserve to restart the battery. It's still interlocked on temp though, and will not restart until it reaches it's set point.

If I understand correctly, Roadtrek didn't start out with an extra AGM battery. It was a kludge to address it's issues with Voltstart not triggering to recharge the lithiums. Problem is their BMS is such an energy hog, it was draining the batteries down to very low voltages.

The Volta autostart is also working based off SOC as I understand it and not from reading a voltage.

Regardless of the trigger that the BMS employs, once the battery shuts down, it can't awaken itself to accept recharging without some stimulus to reopen the charge path.

The lithium Etrek originally had no AGM battery included. My understanding is that it was added to satisfy a condition the charging source(s) need to effect recharging. I think that Mumkin's episode with her setup is what prompted the factory change.

I'm at a loss how adding an AGM battery could correct any issues with Voltstart. I think Voltstart problems apparently had three different causes but I don't think any of them could be corrected with an additional battery:

1. There were different modules for the lithium and AGM setup. Some coaches were supplied with the incorrect module.

2. Some had wiring errors in the loom connecting the Voltstart module and the remote start module.

3. Some owners didn't follow the fairly complicated setup instructions which differed depending on whether the platform was Chevy, Sprinter or Promaster.

One of the problems with vetting an autostart system is that it involves a lengthy process with multiple restarts involved, so it can't be quickly good-or-bad tested like most other equipment. It's possible that it isn't even tested during production at the factory. And at the point of sale when the owners presumably gets their orientation, other than pointing at the switch, it's likely that the system is never even explained much less thoroughly tested prior to dealer delivery.

[booster]

Originally Posted by cruising7388

Regardless of the trigger that the BMS employs, once the battery shuts down, it can't awaken itself to accept recharging without some stimulus to reopen the charge path.

The lithium Etrek originally had no AGM battery included. My understanding is that it was added to satisfy a condition the charging source(s) need to effect recharging. I think that Mumkin's episode with her setup is what prompted the factory change.

I'm at a loss how adding an AGM battery could correct any issues with Voltstart. I think Voltstart problems apparently had three different causes but I don't think any of them could be corrected with an additional battery:

1. There were different modules for the lithium and AGM setup. Some coaches were supplied with the incorrect module.

2. Some had wiring errors in the loom connecting the Voltstart module and the remote start module.

3. Some owners didn't follow the fairly complicated setup instructions which differed depending on whether the platform was Chevy, Sprinter or Promaster.

One of the problems with vetting an autostart system is that it involves a lengthy process with multiple restarts involved, so it can't be quickly good-or-bad tested like most other equipment. It's possible that it isn't even tested during production at the factory. And at the point of sale when the owners presumably gets their orientation, other than pointing at the switch, it's likely that the system is never even explained much less thoroughly tested prior to dealer delivery.

I would certainly hope that the Voltstart won't start the engine unless there is a battery connected to the alternator, so the alternator doesn't go way high and destroy stuff. Even Roadtrek wouldn't be that foolish to allow starting under those conditions, so they needed the AGM so the Voltstart sees a battery. Of course the Balmar will also not activate without seeing a battery, so even if the Voltstart did start the engine, there would be no charging from the Nations alternator.

[wincrasher]

I don't see why the chassis battery isn't sufficient for monitoring and an autostart system. The draw is in milliamps, not unlike the stereo.

The Promaster also has an unusually large and robust AGM chassis battery.