Roadtrek Ecotrek and Voltstart

[Davydd]

Why can't shore power or the alternator provide the power instead of an AGM battery?

[gerrym51]

Originally Posted by gregmchugh

In other words the instructions are still valid and work as long at the added AGM is in place. Not sure how you got two issues out of this but yes the issue would be that there needs to power on the house 12v circuit for the reset switch to provide power to the BMS to reboot and start the lithium charging process.

The issue for the armchair enginners to speculate on is: When the batteries are disconnected by the BMS, why is there no power on the circuit when plugged into shore power or running the engine generator which I expect was the way the system was supposed to work. Or maybe the issue was only with one of the charging sources...

sorry-regardless what they say the agm is for voltstart also

[booster]

Originally Posted by Davydd

Why can't shore power or the alternator provide the power instead of an AGM battery?

They can if you can get them running, but neither of them will start running without a battery in the system for reference voltage. In the startup procedure, they look for proper 12v reference, and if it isn't there, they won't function and start charging.

I did look, and the Outback also needs a battery reference to initiate.

[gerrym51]

Originally Posted by Davydd

Why can't shore power or the alternator provide the power instead of an AGM battery?

because on the roadtrek system without the agm to power up the control panels to turn on the lithium-no power is reaching them- the agm gives the control panel power to turn on the ecotreks

i have no idea why this is like this-just that it is

[gregmchugh]

I think it is pretty clear that when the EcoTrek BMS disconnects the battery module when it hits the low voltage point there is not anymore power provided until the reset button supplies it from the house circuit. I expect they had a reason for this, probably simplicity, but it seems like you could set it up so that it resets using the internal cell power when you hit the reset switch. Another option would seem to be that rather than kill the BMS completely when it disconnects you used a reset circuit internal to the module that would reboot when it sees charge level voltage coming into the module. Of course, this does not deal with an issue of the charge sources not operating when there are no batteries on the circuit.

[avanti]

How about a little 12VDC power brick connected to shore power? I don't see why this wouldn't suffice for providing a 12V reference to get the ball rolling.

[gregmchugh]

Originally Posted by avanti

How about a little 12VDC power brick connected to shore power? I don't see why this wouldn't suffice for providing a 12V reference to get the ball rolling.

Still have the issue of using the engine generator when not on shore power.

It seems the solution is either what they did, a battery independent of the lithiums, or a way to have the EcoTrek BMS reconnect to the system using inernal power when commanded to provide a reference voltage for the chargers. I suppose you could have a way to jump the chassis 12v for a reference to get things started but that would not work with the 24v configurations.

[booster]

I think a lot of the suggestions that Greg or Avanti put out would work, as long as they had enough current available for the charging sources. That is why I find all this so odd, as there are lots of ways to do it. We don't know how Roadtrek has this AGM wired in, but they may just have a small battery, with a trickle charger on it, and a switch to put it into the system when the lithiums and BMS are offline. I that is the case, I would think a diode protected source from the engine battery, with the switch would also work just fine.

It would be interesting to ask ARV how their systems would react if the batteries somehow went totally flat so there was no power available. They well may have a small power supply to boot them up off shore power.

[gerrym51]

Originally Posted by avanti

How about a little 12VDC power brick connected to shore power? I don't see why this wouldn't suffice for providing a 12V reference to get the ball rolling.

isn't this an agm battery-only bigger

[gregmchugh]

Originally Posted by booster

I think a lot of the suggestions that Greg or Avanti put out would work, as long as they had enough current available for the charging sources. That is why I find all this so odd, as there are lots of ways to do it. We don't know how Roadtrek has this AGM wired in, but they may just have a small battery, with a trickle charger on it, and a switch to put it into the system when the lithiums and BMS are offline. I that is the case, I would think a diode protected source from the engine battery, with the switch would also work just fine.

It would be interesting to ask ARV how their systems would react if the batteries somehow went totally flat so there was no power available. They well may have a small power supply to boot them up off shore power.

Getting the power from the engine battery might be an issue for the 24v configurations with 24v inverter/charger and 24v engine generator I guess you could have a dc to dc converter to get the 12v up to 24v in that case.

[avanti]

In fairness, Teslas have a conventional 12V automotive battery to power the electronics, despite the fact that they have enough Lithium to drive hundreds of miles. I'm sure that they thought it through, so I guess it must make some kind of sense.

[booster]

Originally Posted by gregmchugh

Getting the power from the engine battery might be an issue for the 24v configurations with 24v inverter/charger and 24v engine generator I guess you could have a dc to dc converter to get the 12v up to 24v in that case.

Good point-I wonder if this applies only to the 12v models, or are they using a 24v battery in the others.

Davydd's is 12v, isn't it?

[booster]

Originally Posted by avanti

In fairness, Teslas have a conventional 12V automotive battery to power the electronics, despite the fact that they have enough Lithium to drive hundreds of miles. I'm sure that they thought it through, so I guess it must make some kind of sense.

I read something a long time ago about that, and I think they figured it was because the rest of the system was so specifically tied to high voltages, but don't recall details.

[gregmchugh]

Originally Posted by booster

Good point-I wonder if this applies only to the 12v models, or are they using a 24v battery in the others.

Davydd's is 12v, isn't it?

All the systems seem to be built using multiples of the Ecotrek 200 module.
An Ecotrek 400 is just two of the 200's wired in parallel. The 800 and 1600 have 4 and 8 of the 200's but seem to be set up to give 24v. Each of the 200 modules had it's own internal BMS so they can be connected up just like any battery bank would be done. Similar to the 8 AGM 24v battery ETrek but without the issue some batteries under the hood.

[booster]

I should have been more clear, are they putting a 24v AGM in the 24v lithium models.

[gregmchugh]

Originally Posted by gerrym51

sorry-regardless what they say the agm is for voltstart also

Yes, we haven't ventured back into the Voltstart area yet...

[gerrym51]

Did anybody notice on the ecotrek sheet greg posted that voltstart now lasts about 20 minutes

[gregmchugh]

Originally Posted by booster

I should have been more clear, are they putting a 24v AGM in the 24v lithium models.

Good question, recent reports of the added AGM have been 12v configurations only. Not sure I have seen any reports of working Ecotrek 24v vans but they may surely be out there with added AGMs I would expect. Maybe a small 24v AGM if there is such a thing or two small 12V in series?

Also have not seen what size 12v AGM they are using for the add on...

[gregmchugh]

Originally Posted by gerrym51

Did anybody notice on the ecotrek sheet greg posted that voltstart now lasts about 20 minutes

Yes, I saw that and no mention of the 6 cycle limit on restarts was there but I don't think it went away. Also mentions the fact that the hood and doors must be closed for it to operate.

We were speculating before on the power for the Voltstart which is likely to be located up front somewhere with the activation switch in the dash and some interface into the chassis electronics for the auto start. My guess is that it gets its power from the chassis 12v circuit and gets its voltage reading for the house circuit from the engine generator circuit. All this could be wrong but seems plausible to me.

[Davydd]

Originally Posted by booster

Good point-I wonder if this applies only to the 12v models, or are they using a 24v battery in the others.

Davydd's is 12v, isn't it?

Advanced RV is a 12v system. What I do know is in theory there is no way you can deplete the lithium ion batteries lower than 20% SOC as they will simply disconnect at that point. You are right that the Outback has to detect a 12v source. A couple of weeks ago I turned off my autogen and deliberately drove my batteries down to 20% and they disconnected as they were supposed to do. Then I plugged into shore power and it took 5 - 6 minutes holding down a start button toggle before power resumed and charging continued on its own. My understanding that hold down was building up 1% (or 21%) of charge for the computer electronics to resume their function.

My 800ah battery bank consists of 16 200ah 3.2v cells. So there are 4 cells in series to make 12v and four in parallel to make 800ah all controlled as one. Each cell has a computer chip sensor attached to it to read voltage and temperature. The BMS will shut the bank down if the voltage drops to 20% or the temperature drops to about 32 degrees with any cell I believe. Heating pads sense the temperature drop somewhere above freezing and come on automatically at a higher temperature reading. Shore power as I am on right now will supply that heating power for perpetuity. If off shore power the autogen will come on at a programmed SOC you can set yourself. I've got it set at 30% which means 30% of the 640ah available or at 44% of the full 800ah. Lots of reserve and I haven't gotten that low yet other than for testing. I'm monitoring my batteries right now and they are, when plugged into shore power with little load, running about 10 degrees above ambient outside temperature. They have been as high as about 20 degrees higher when under heavier loads.

BTW, like Voltstart, Advanced RV autogen will come on for 5 times. After 5 you have to physically insert your key and start the engine. Then you have 5 more auto starts. I'm thinking that might be a Mercedes Benz thing. When I do auto start I have it programmed to run 110 minutes or when fully charged. I tested that too. I set my autogen to come on at 90% SOC and when it reached full charge it shut off. That was somewhere around 20 minutes.

The few supposed photos of the ecotrek lithium ion batteries I've seen I did not see anything remotely like a computer chip sensor on the individual cells. So I am not sure how they are controlling all those functions.

I'm describing this stuff from my electrical knowledge dyslexia. I don't pretend to know how it really functions. I'm just trying to describe what was said to me in laymen's terms and what I have tested to verify.