Roadtrek Ecotrek and Voltstart

[markopolo]

So just a delay meaning the people participated in the offer will eventually get them?

The delay would be disappointing but at least they'll get them if they want them. Is that what he meant?

Why didn't the dealer just say there was a delay

my husband talked with the dealer and was told that Roadtrek is offering a $1500 refund if we forego the battery, and that people are having trouble with the batteries, getting it to function.

[gerrym51]

I know 2 owners with agm and ecotrek together.

one had ecotrek added to agm. one had agm added to ecotrek because voltstart would not work.

both failures.

one was given new etrek and took agm.

one did not take delivery.

although i know of some ecotrek/voltstart successes- i know of no 'tandem ecotrek' successes

[gregmchugh]

As a thought experiment lets just assume for a moment that some other company besides Roadtrek is selling a mixed AGM / Lithium configuration, is there a way to have a mixed set of 12 volt batteries, some AGM and some lithium all connected in parallel, connected to a common load/charge connection, such that a battery management system including charging control internal to the 12v lithium battery module could correctly handle lithium cell charging from an external AGM charging profile, and the discharge of the mixed battery bank would provide something close to the combined amp hours if the overall battery bank.

I want to remove the issue of whether Roadtrek can ever design a electrical system that works correctly and just look at the technical aspects of a mixed battery system

[markopolo]

Same challenges faced and same questions asked regardless who's doing it from my point of view.

I think some of the energy from the lifepo4 will be wasted as it will go to charging the AGM. I also think the lifepo4 will do most of the work because of the minimal voltage drop during discharge. Also, what happens when the off-the-cliff voltage drop off occurs when the lifepo4 is fully discharged?

Here's a chart showing both lifepo4 and lead acid:

lithium & solar power LiFePO4 : Photo

It really does look like the lifepo4 will supply all the current until it is nearly depleted. What happens then? How much current will the lifepo4 draw from the AGM at that point?

[booster]

Originally Posted by gregmchugh

As a thought experiment lets just assume for a moment that some other company besides Roadtrek is selling a mixed AGM / Lithium configuration, is there a way to have a mixed set of 12 volt batteries, some AGM and some lithium all connected in parallel, connected to a common load/charge connection, such that a battery management system including charging control internal to the 12v lithium battery module could correctly handle lithium cell charging from an external AGM charging profile, and the discharge of the mixed battery bank would provide something close to the combined amp hours if the overall battery bank.

I want to remove the issue of whether Roadtrek can ever design a electrical system that works correctly and just look at the technical aspects of a mixed battery system

I don't think it could work unless it had two separate control systems. I don't see any way that the lithium and AGM could just be attached together and work properly. Of course, if they had the multiple bank manual switches that were shown earlier on another system, you could run on either the lithium or AGM and when it was low, switch to the other one. With two charging systems, one for each, that could work. But, there are 3 different charge sources, so you could need more than 2 chargers.

As Marco mentioned earlier, you would need to get them onto the bench and test how they react to different situations. We found that even minor cable length differences can affect AGM charging and discharging balance that way. And from the etrek discussion, it is apparent that abuse can cause very early AGM failures.

[gregmchugh]

I will continue to be the devils Advocate. Ignore charging for now and look at discharging My simple mind says the with a mixed AGM / Lithium bank with all in parallel that the lithium batteries discharge first and power the loads and keep the AGM batteries up near full charge. At some point the battery management control in each lithium battery module disconnects the battery when it reaches the "complete" discharge point and eventually just the AGM batteries are powering the load and at some voltage set point the auto generator start activates and the generator starts recharging the battery bank. Tell me how my simple minded process is flawed, I am not really very knowledgeable about all this and expect I am missing something basic about all this.

[markopolo]

What LVC is RT setting for their modules?

If 2.5V per cell then that's 10V. If 2.8V per cell then that's 11.2V. The AGM bank will be involved in powering the load way before those voltages.

[gerrym51]

the voltstart video shows different voltages than have been printed in the past

[gregmchugh]

So, as the lithium modules discharge, at some point the AGMs also start discharging in parallel with the Lithiums. What if the lithium batteries are set to drop off line at a higher voltage than the generator start voltage, leaving the AGMs to continue discharging to the gen start point. Any issues with that? Or would you try to start the gen before the lithiums go offline?

[gerrym51]

Originally Posted by gregmchugh

So, as the lithium modules discharge, at some point the AGMs also start discharging in parallel with the Lithiums. What if the lithium batteries are set to drop off line at a higher voltage than the generator start voltage, leaving the AGMs to continue discharging to the gen start point. Any issues with that? Or would you try to start the gen before the lithiums go offline?

greg-you are guessing-who knows what roadtrek is doing-they are not telling

[markopolo]

I think people spend the big bucks for lithium because they can be discharged 80% or 90% and then be charged quickly.

Raising the LVC limits the DOD. Lesser DOD can mean more batteries needed. More batteries = more $.

Running a generator or an engine is not permitted at all hours in some parks: http://www.classbforum.com/forums/f5...html#post34773

[gregmchugh]

Gerry, Mine is a generic technical discussion, not specific to Roadtreks design, how could it be done?

[Davydd]

Originally Posted by markopolo

I think people spend the big bucks for lithium because they can be discharged 80% or 90% and then be charged quickly.

Raising the LVC limits the DOD. Lesser DOD can mean more batteries needed. More batteries = more $.

Running a generator or an engine is not permitted at all hours in some parks: http://www.classbforum.com/forums/f5...html#post34773

There is a solution for that. I can program my Advanced RV auto start so that it won't come on during quiet hours. I didn't see that in the Voltstart video though.

Anyway, it is kind of an overblown concern, IMO. I am sure owners would not want their engine coming on while they are sleeping anymore than the rest of the campground. No different than using your Onan generator you can simply check your state of charge and run your engine during permitted hours if you need to. It is easy enough to predict how much energy you will use overnight and what your state of charge should be to get you through a night. One might get surprised one first time, but like putting fingers on a hot stove you probably won't again.

[markopolo]

The point was that relying on a generator autostart to prevent a system shutdown wouldn't always be doable.

The system still needs to be able to function without that feature.

[gerrym51]

Originally Posted by Davydd

There is a solution for that. I can program my Advanced RV auto start so that it won't come on during quiet hours. I didn't see that in the Voltstart video though.

Anyway, it is kind of an overblown concern, IMO. I am sure owners would not want their engine coming on while they are sleeping anymore than the rest of the campground. No different than using your Onan generator you can simply check your state of charge and run your engine during permitted hours if you need to. It is easy enough to predict how much energy you will use overnight and what your state of charge should be to get you through a night. One might get surprised one first time, but like putting fingers on a hot stove you probably won't again.

Raodtrek appears not to have a way to tell you state of charge

[Davydd]

Originally Posted by markopolo

The point was that relying on a generator autostart to prevent a system shutdown wouldn't always be doable.

The system still needs to be able to function without that feature.

I am not sure what you are trying to say. I can manually start the engine remotely and keyless at anytime I desire. I don't have to wait for auto start to kick in. I can also program auto start to come on at any state of charge. I can also turn my auto start feature completely off and if the lithium ion battery state of charge got down to 20% the system would automatically shut down and disconnect the batteries to preserve the batteries until I gave it personal attention like start the engine with a key in the ignition to start the van engine to charge the batteries. The second under hood alternator then charges at a rate greater than 200 amps or about twice as fast as shore power or an Onan generator. This seems all more reliable than an Onan generator which is another internal combustion engine to maintain and from my experience would need you to also start by turning on the van engine to get enough electrical juice jumped to it when your batteries are run down.

I don't see much downside to a second alternator (or under hood generator like Roadtrek calls it) whether you have an auto start feature or not. Saves weight and saves space instead of an Onan generator which can be allocated to more batteries, and you can preserve your propane for other things (with diesel engines.) With gas or diesel, with more battery power you could eliminate propane for the most part.

[Davydd]

Originally Posted by gerrym51

Raodtrek appears not to have a way to tell you state of charge

No idiot lights?

[gerrym51]

Originally Posted by Davydd

No idiot lights?

idiot lights do not work with lithium

[markopolo]

Davydd - my comment followed Greg's mentioning auto start in these posts about paralleling AGM and Lifepo4:

http://www.classbforum.com/forums/f5...html#post36337

http://www.classbforum.com/forums/f5...html#post36333

Nothing to do with your rig.

-------------------

Originally Posted by gregmchugh

Gerry, Mine is a generic technical discussion, not specific to Roadtreks design, how could it be done?

Other things to consider:

The lithium batteries will do best when stored at less than a fully charged state from what I've read.

The AGM's will need to be stored near fully charged to prevent sulfation.

The lithium's will do fine with partial state of charge cycling (PSOC). Start the day at 70% then down to 50% and back to 80% later in the day. It doesn't matter with lifepo4.

The AGM's won't do well with PSOC cycling. They'll do best when fully recharged after each use.

[Davydd]

Originally Posted by markopolo

Davydd - my comment followed Greg's mentioning auto start in these posts about paralleling AGM and Lifepo4:

http://www.classbforum.com/forums/f5...html#post36337

http://www.classbforum.com/forums/f5...html#post36333

Nothing to do with your rig.

-------------------



Other things to consider:

The lithium batteries will do best when stored at less than a fully charged state from what I've read.

The AGM's will need to be stored near fully charged to prevent sulfation.

The lithium's will do fine with partial state of charge cycling (PSOC). Start the day at 70% then down to 50% and back to 80% later in the day. It doesn't matter with lifepo4.

The AGM's won't do well with PSOC cycling. They'll do best when fully recharged after each use.

Marko,

I'm no expert in regard to mixing batteries like AGM and Lithium Ion other than to suspect Rube Goldberg's lesser brother is adding more complexity onto something already in a state of confusion. The question I guess is does Roadtrek regulate two different charging profiles? I was only addressing the auto start features.

The lithium ion batteries living in a state of partial state of charge is a strange one. It makes no sense and everything I have read has been anecdotal speculation and a lot of meaningless nonsense in practicality. I've asked Advanced RV about this and it has been double-check with Elite Power Solutions the distributors the GBS lithium ion batteries I have. They have nothing to substantiate this. With the amount of cycles they have been tested to it would be a matter of non-concern anyway. To go 5,000 cycles would mean fully charging every single day for over 13 years. Over charging is a concern. Charging at below freezing is a concern and totally discharging is a concern. A good system would have all those safeguards built in. Advanced RV put the DOD at 80%. Roadtrek is a little more reckless at 90% DOD. Mine float at 99% SOC no matter what the charging source is applied. If I plugged into shore power, was under full sunlight on my solar panels and ran my engine alternator all at the same time it would bulk charge at over 300 amps input until it reached 99% SOC and then stay there and only accept additional charge to replace discharge which is about a rate of 6-10 amps per hour. I've set my DOD arbitrarily at 70% which is more conservative but have yet to reach that point where auto start would come on to charge. I think it would be very difficult to keep lithium ion batteries at a partial state of charge in a Class B when just a little bit of driving fully charges them each day on the road.