ecotrek batteries using 6 internal amps

[gregmchugh]

The actual charge voltage profiles used by the 3 chargers is not known but I will throw out a speculation on how one might handle the mixed AGM / lithium battery configuration. If you wanted to insure the AGM battery gets charged fully you might accept that an AGM profile will be good enough to provide adequate lithium battery charging. The lithiums cannot get overcharged since the battery management controls will disconnect the chargers if needed. Pure speculation, This may not be what they are doing.

There could be other strategies for handling the mixed battery setup.

As Booster mentioned, the AGM battery would not discharge until the lithium batteries were down to voltages less than the AGM fully charged voltage level. Once all the Ecotrek battery management controllers open all the load terminal relays at 10% charge the AGM battery gets disconnected from the loads too.

[gregmchugh]

Originally Posted by cruising7388

Apparently there is indeed a defeat switch for VoltStart and enabling it does not shut down the batteries until they discharge to the point where the BMS says enough is enough and shuts down the discharge path but somehow keeps open a re-charge path. I'm hazarding the guess that the AGM battery addition provides a fall back recognition load for the UH generator or the charger and perhaps even stimulates some logic to the BMS to permit a recharge process even though the discharge path is shut off.

The general speculation by the armchair engineers seems to have been that the AGM was added to provide the chargers with a battery connection when all the Ecotreks were disconnected from the chargers. Other theories have been mentioned but that seems to be the most popular...

[gerrym51]

aren't lithium batterys considered a high charge acceptance rate and the engine generator just charges high amps.

Maybe roadtrek considers the ecotreks as 'temperory' high energy reservoirs that quickly deplete to be highcharged again by engine generator.

[cruising7388]

Originally Posted by gerrym51

I think Roadtrek wants to be able to mix and match ecotrek and agm among their many models.

Having each battery basically 'stand alone' with their own bms and relays actually makes sense if that is the goal.

this system however cannot get around the effect of using up power of each battery.

If it was all batteries tied to to 1 set of relays and one bms like in Davydd's i'm sure power consumption would be far less.

No question that having multiple batteries equipped with independent BMSs complicates the system and requires more power to support, but the redeeming virtue is that a battery or BMS failure doesn't incapacitate the entire system.

It seems to be that at least some BMS power requirements could be reduced to milliamps by:

1. Not having the BMS continually monitor battery status. Just sample it once a minute or so unless it senses a short circuit condition which prompts it to act immediately.

2. Use bi-stable latching relays which draw significant current only for milliseconds. They do cost more but in the perspective of the eight thousand dollar cost of the batteries themselves, it represents chump change.

That said, there is a power dissipation fact of life that can't be avoided and that's for battery temperature control in sub-freezing conditions but that's not a cross to bear that's exclusive to Roadtrek. Any lithium battery system has to live with this Sword of Damocles. In zero or sub-zero conditions, the 6 amp BMS load cited may be optimistic.

[gregmchugh]

The power needed to monitor cell voltages and temperatures and shunt current at any reasonable frequency and trigger the relays is not significant assuming they are using any of many available low power microcontrollers.

If someone can suggest anything besides relays and battery heaters that have the potential to use 6 amps please do it...

[avanti]

Originally Posted by gregmchugh

If someone can suggest anything besides relays and battery heaters that have the potential to use 6 amps please do it...

A mis-designed circuit could easily do this.

As someone (Marko?) suggested above somewhere, whatever is consuming such power will be hot. Should be easy enough to find.

[gerrym51]

wHAT IS IS. What roadtrek can do and what roadtrek does is.

[cruising7388]

Originally Posted by gregmchugh

RT has always said they would discharge the Ecotreks down to 10%

The Voltstart trigger point appears to have changed from the original spec to a higher voltage (it has no measure of actual battery charge level) but if you look at the typical usage profile it turns out the trigger point is not critical. The trigger voltage needs to be high enough to avoid inverter low voltage and Ecotrek low voltage shutdowns and low enough to avoid triggering before the battery bank has discharged the power provided by a single Voltstart engine run cycle. The total energy available using Voltstart from a fully charged battery bank will be 90% of the battery capacity plus the energy from the total engine run time of the Voktstart cycles as long as the trigger voltage meets the limits above.

Bottom line, Voltstart trigger voltage point does not seem to be a critical parameter...

I don't know this as a fact but it seems to me that the factory has to calibrate the AGM trigger point differently than the trigger point for the ECO batteries.
Voltage degradation during ECO requires a very sensitive measuring circuit.
The better measurement is a meter that compares power delivered with designed capacity. I have no idea what metric Roadtrek uses for their measurement.

The AGM battery condition is much easier to determine for VoltStart because the terminal voltage decrease corresponds reasonably closely with depth of discharge. What surprises me is that the Etrek explanation of Voltstart on their website cites 11.2 Volts as the trigger point for VoltStart. But a terminal voltage of 11.2 volts doesn't represent 50% depth of discharge. It represents complete discharge which is not a happy state for a lead acid battery.

[cruising7388]

Originally Posted by mojoman

You can't mix AGM and lithium batteries in the same system. The AGM battery will inevitably cook if connected together and charged at the lithium voltage of 14.6v. There are systems that connect a small amount of lithium batteries to lead batteries but only to handle surges and short high demands of inverters. They are usually setup to cut in at around 11.5v and it lengthens the life and AH of the lead batteries. They act similar as a start capacitor.

Well, unless the AGM battery supplied to support the Etrek is charged by the OEM alternator that's dedicated to charging the starting battery, it apparently is subjected to the charging parameters of the lithium batteries.

[gregmchugh]

Originally Posted by cruising7388

I don't know this as a fact but it seems to me that the factory has to calibrate the AGM trigger point differently than the trigger point for the ECO batteries.
Voltage degradation during ECO requires a very sensitive measuring circuit.
The better measurement is a meter that compares power delivered with designed capacity. I have no idea what metric Roadtrek uses for their measurement.

The AGM battery condition is much easier to determine for VoltStart because the terminal voltage decrease corresponds reasonably closely with depth of discharge. What surprises me is that the Etrek explanation of Voltstart on their website cites 11.2 Volts as the trigger point for VoltStart. But a terminal voltage of 11.2 volts doesn't represent 50% depth of discharge. It represents complete discharge which is not a happy state for a lead acid battery.

Based on most reports the Voltstart trigger voltage for Ecotrek systems is above 12 v maybe 12.4 volts or around there...

[gregmchugh]

Originally Posted by cruising7388

No question that having multiple batteries equipped with independent BMSs complicates the system and requires more power to support, but the redeeming virtue is that a battery or BMS failure doesn't incapacitate the entire system.

It seems to be that at least some BMS power requirements could be reduced to milliamps by:

1. Not having the BMS continually monitor battery status. Just sample it once a minute or so unless it senses a short circuit condition which prompts it to act immediately.

2. Use bi-stable latching relays which draw significant current only for milliseconds. They do cost more but in the perspective of the eight thousand dollar cost of the batteries themselves, it represents chump change.

That said, there is a power dissipation fact of life that can't be avoided and that's for battery temperature control in sub-freezing conditions but that's not a cross to bear that's exclusive to Roadtrek. Any lithium battery system has to live with this Sword of Damocles. In zero or sub-zero conditions, the 6 amp BMS load cited may be optimistic.

Each Ecotrek module has 4 amp battery heating pads which can be used to bring a cold soaked battery up to temp to allow it to be brought online ( power for this is provided by the underhood generator) or to keep an operating Ecotrek from getting too cold to continue operating (power for this can come from the batteries and any of the chargers). Operating Ecotreks connected to loads have some level of internal heating which reduces the power needed by the heating pads.

[gregmchugh]

There seems be confusion on the validity of the 6 amp internal load. The information on the 6 amp internal load for each Ecotrek module came directly from Roadtrek in the email to an owner that Gerry provided, it was not speculation by someone outside of Roadtrek.

[cruising7388]

Originally Posted by gregmchugh

There seems be confusion on the validity of the 6 amp internal load. The information on the 6 amp internal load for each Ecotrek module came directly from Roadtrek in the email to an owner that Gerry provided, it was not speculation by someone outside of Roadtrek.

Got that, but is the 6 amp figure a fixed load? 4 amps of this is presumably dedicated to the battery heaters but I wouldn't think it involves a 100% duty cycle unless you were parked at the Polar ice cap. Don't the heaters cycle on and off and wouldn't this affect the average battery maintenance power consumed?

[gregmchugh]

Originally Posted by cruising7388

Got that, but is the 6 amp figure a fixed load? 4 amps of this is presumably dedicated to the battery heaters but I wouldn't think it involves a 100% duty cycle unless you were parked at the Polar ice cap. Don't the heaters cycle on and off and wouldn't this affect the average battery maintenance power consumed?

The email is not specific, heaters may be included in the 6 amps or maybe not but based on the overall instructions in the email I think there is a good chance the 6 amps may be the internal load without the heaters. The use of the heaters is not a common condition so why give these very specific instructions for how to use the batteries for that very uncommon scenario.

In any case, the heaters probably have a low duty cycle except in the case of bringing a frozen battery bank up to temp to bring it online and the underhood generator is used in that case to power the heaters. The instructions seem more general than that rare case and are focused on daily use with solar.

But things are rarely clear on these things since the info from Roadtrek is sparse and typically without explanation of the underlying reasons for the instructions. This is actually a rather transparent set of info , they normally avoid divulging any shortcomings in the designs.

[gerrym51]

Originally Posted by cruising7388

Got that, but is the 6 amp figure a fixed load? 4 amps of this is presumably dedicated to the battery heaters but I wouldn't think it involves a 100% duty cycle unless you were parked at the Polar ice cap. Don't the heaters cycle on and off and wouldn't this affect the average battery maintenance power consumed?

Since there is still time to change your ecotrek 800 order or not change it-why not address this directly to roadtrek-maybe it is not correct or you can get clarification


however i agree with greg-i do not believe the heaters are included in that 6 amp use

[Davydd]

A complaint about battery use in June probably has nothing to do with heaters. It would take air temperatures nearly down to 20F for heaters to even come and then they are intermittent to maintain a set battery temperature above freezing. My li-ion battery temperature is consistently 10 - 20F above air temperature.

We attended Wendland's Winter Freezeout at Tahquamenon Falls in Michigan's UP last January. The temperatures were actually mild in the mid 20s day and night and my battery heaters never came on at anytime I had observed them parked for three nights and plugged into shore power.

[booster]

Don't know how copyright stuff works, but links are always OK I have heard, so will put a link.

This was in the comics this morning (Dilbert), and I think I recognized references to a bunch of us and others.

Twitter Complaints - Dilbert Comic Strip on 2016-06-13 | Dilbert by Scott Adams

[booster]

I agree with Greg, Gerry, and davydd that is it highly unlikely that the heaters are included in the 6 amps of load.

[gregmchugh]

I am hoping that an Ecotrek owner or potential owner follows up and gets a confirmation of the internal load. If this sh*tstorm came from bad info I would like to know that. If the info is wrong then RT needs to fix the customer support process to avoid this type of incident.

Someone from the owners group posted an inquiry on thecRoadtreking group to get a load number but the post disappeared, maybe by the poster who had second thoughts about doing it...

[gerrym51]

Originally Posted by gregmchugh

I am hoping that an Ecotrek owner or potential owner follows up and gets a confirmation of the internal load. If this sh*tstorm came from bad info I would like to know that. If the info is wrong then RT needs to fix the customer support process to avoid this type of incident.

Someone from the owners group posted an inquiry on thecRoadtreking group to get a load number but the post disappeared, maybe by the poster who had second thoughts about doing it...

Is the poster still a member? if you can't highlight their name they've been kicked out


cruising 7388 has a 210 eco800 on order. seems he should inquire.