Hymer new Lithium/AGM combo

[GeorgeB]

Hymer Europe introduced a new energy package that combines Lithium and AGM batteries. Although it has a very limited energy capacity (230 Ah) compared the huge banks some members of this forum have installed in their rigs, it is an original hybrid solution that could be an interesting transition toward the onerous all-Lithium systems. Aren't Tesla cars equiped with an AGM battery to keep the BMS system working?

It is composed of a 95 Ah AGM wired in parallel with a 135 Ah lithium battery.

Is it combining the best of both technologies or simply making it more complicated with limited benefits? Time will tell.


As mentioned in the press release:

...The lithium batteries undertake the majority of the charging cycles, whilst the lead batteries serve as backup storage devices.

…By connecting together two different battery systems, the entire winter-proof system can even be operated at temperatures below 5 °C, without any adverse impact on the lithium battery. This is because the operation of the entire system at lower temperatures is ensured by the lead battery, which is impervious to the cold.
…


The press release:
https://www.eriba.com/assets/files/m...y%20System.pdf

An article in Motorhome Full time
Hymer introduces energy package | Motorhome Full Time











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[booster]

The Roadtrek systems here all have an AGM which is needed to recover the lithiums if they go into shut down. Likely Hymer is using that same thing in Europe, but with a smaller battery.

[GeorgeRa]

Interesting development, seems as Roadtrek influence on Hymer. With a higher sensitivity to gas mileage with EU fuel costs weight savings will have significant value there. Estimated life of 3 years for AGM and 10 years for Li/AGM combo is a little pessimistic for the AGM and optimistic the combo.

No cost data yet, but having a well-engineered system will help to penetrate the market successfully.

For my needs of 230Ah AGM or more weight saving in US is still insufficient to switch.

[GeorgeB]

Originally Posted by GeorgeRa

Interesting development, seems as Roadtrek influence on Hymer. ...
No cost data yet, but having a well-engineered system will help to penetrate the market successfully.

Yes I'm curious if Roadtrek had any input on this European option. Just hope they didn't consult the same engineers. :-0 The Hymer system is offered as a 3000 € option.

The originality of the system seems to be that the two batteries are wired in parallel and are working together to supply power. What kind of hybrid BMS could manage both types?

[booster]

Originally Posted by GeorgeB

Yes I'm curious if Roadtrek had any input on this European option. Just hope they didn't consult the same engineers. :-0 The Hymer system is offered as an 3000 € option.

The originality of the system seems to be that the two batteries are wired in parallel and are working together to supply power. What kind of hybrid BMS could manage both types?

The parallel of the battery types has been an issue here with Roadtrek systems from what I have heard. The AGMs can have very short life in them and need replacing nearly every year in some of the examples I have seen mentioned.

[JohnnyFry]

That fact in itself is discouraging and inflates the cost of operation for an already expensive system, as well as adding to the overall weight of the system. It appears that some of the other Li systems out there do not need an auxiliary AGM so apparently it is an issue with the BMS used by Roadtrek (and now, apparently, Hymer). This aspect certainly bears watching.

[booster]

Originally Posted by JohnnyFry

That fact in itself is discouraging and inflates the cost of operation for an already expensive system, as well as adding to the overall weight of the system. It appears that some of the other Li systems out there do not need an auxiliary AGM so apparently it is an issue with the BMS used by Roadtrek (and now, apparently, Hymer). This aspect certainly bears watching.

We don't know about the new Xantrex system or the Volta system yet, but best guess is that they don't use an AGM.

As far as I have been able to determine, the AGM is only really needed if the BMS has shut the charging down due to under 32*F and there is no way to heat the batteries back up until they will accept charge. ARV doesn't have the AGM, and they are OK if there is still enough charge in the batteries to run the heaters and heat up the batteries until they come back online, but if they are in cold shut down for charging and low battery shutdown you are out of luck and need to get the van to someplace warm. The heaters won't work because none of the charging sources will activate and hold hold voltage without a battery reference. Roadtrek had similar problems before they added the AGM, which allows the charging sources to come on and run the heaters.

IMO, the obvious solution is to make sure there is another way to heat the batteries without going south or inside. The van power system is totally separate and will work normally through all of this, so it seems that all you would need would to be able to switch the heaters to van power until the batteries warm up and a charging source comes on. Unless I am missing something, I just don't see the need for the AGM if you have well designed system.

There is also likely another reason the Roadtrek had to go with the separate AGM, which is not disconnected when the lithium modules are, and that is their horrendously large parasitic losses in lithium modules. They will drain themselves with no loads in only a couple of days, so whenever not being used or able to be recharged, they have to be shut off, and that would mean the charging sources would not activate and the heaters would not work.

[avanti]

If I were designing a DIY Lithium system today, I would take a close look at using a small Espar hydronic system as a cold weather backup. I could imagine a well-insulated battery compartment that also housed the expansion tank for the Espar. That way, there would be a lot of thermal mass to minimize cycling of the Espar. In the grand order of things, such a setup would not be all that expensive.

I am, of course, just making all of this up.

[mumkin]

Originally Posted by booster

The parallel of the battery types has been an issue here with Roadtrek systems from what I have heard. The AGMs can have very short life in them and need replacing nearly every year in some of the examples I have seen mentioned.

I am on three Facebook pages for Roadtrek/Hymer owners and no one has reported having to replace the AGM that works with the lithiums. Many of the owners don't even know that it is there.

Many issues with Promaster starting batteries, but that is a whole different issue that Dodge dealers having been handling.

[booster]

Originally Posted by avanti

If I were designing a DIY Lithium system today, I would take a close look at using a small Espar hydronic system as a cold weather backup. I could imagine a well-insulated battery compartment that also housed the expansion tank for the Espar. That way, there would be a lot of thermal mass to minimize cycling of the Espar. In the grand order of things, such a setup would not be all that expensive.

I am, of course, just making all of this up.

Those of us that are old enough and live in the cold still remember the gasoline fired engine block tank heaters. They were passive pump "tank" heaters in the terminology of the day and actually worked quite well as long as you kept the exhaust from melting things under the hood.

[booster]

Originally Posted by mumkin

I am on three Facebook pages for Roadtrek/Hymer owners and no one has reported having to replace the AGM that works with the lithiums. Many of the owners don't even know that it is there.

Many issues with Promaster starting batteries, but that is a whole different issue that Dodge dealers having been handling.

Maybe it was an early on type issue, as I have also not heard anything lately. IIRC, the issue was mostly related to lithium modules shutting off on low voltage without the owners noticing, and then the AGM running things until it was dead. Repeatedly running the AGM would be very hard on it. There may now be a disconnect on the AGM to prevent that now. The logical thing would be to have the AGM offline whenever lithium modules are active and only come back online when when a charging source was present, although I don't know how you would control that.

[GeorgeB]

The new European Hymer combo system doesn't seem related in any way to the EcoTrek RT is offering. The batteries are clearly working in tandem to alleviate their respective weakness. The AGM is not there only to power the control module or to pick-up when the Lithiums are dead or offline. It is also

I still don't understand how come RT hasn't resolved the problematic BMS load after 3 years. Or have they? Are there any Ecotrek users out there that are happy with their system? Even if it's often the nature of online forums I only read horror stories of people struggling with having to constantly shutting off the battery banks to prevent excessive draining, ending-up eventually replacing the Lithiums with AGMs. My personal experience with Roadtrek's electrical engineers convinced me to cancel my contract and buy another brand back in 2014, but I was very confident that their new system (designed by exterior consultants?) would be a success.




The press release:
https://www.eriba.com/assets/files/m...y%20System.pdf

An article in Motorhome Full time
Hymer introduces energy package | Motorhome Full Time

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[booster]

Interesting article, but the link is dead.

It sounds like they shut off the lithium, or at least the charging to it, at 5*C and run on the AGM, which makes sense, and the AGM would be there to get things going again. Also would eliminate the need for heaters, which they don't really have enough capacity to run anyway unless a charge source is active.

We don't know how the Roadtrek setup is wired, but parallel has been mentioned and in some way it has to be to get charged at the same time as the lithium. We don't know if it is on the charge or load side of the lithiums, though.

An interesting premise, especially the touting winter use. Roadtrek wouldn't be able to do that, though, as to have enough AGM to run all the stuff that takes power on them, with the reduced output of the AGM in the cold, they would have to have a quite large AGM bank.

[cruising7388]

Originally Posted by booster

Maybe it was an early on type issue, as I have also not heard anything lately. IIRC, the issue was mostly related to lithium modules shutting off on low voltage without the owners noticing, and then the AGM running things until it was dead. Repeatedly running the AGM would be very hard on it. There may now be a disconnect on the AGM to prevent that now. The logical thing would be to have the AGM offline whenever lithium modules are active and only come back online when when a charging source was present, although I don't know how you would control that.

The AGM provided by Roadtrek for their lithium setup is not supposed to supply power to any appliances but to serve solely as a means of resetting the lithium BMS modules in the event they shut down. But since this AGM is paralleled with the lithiums, it's not clear to me how this is accomplished. without subjecting the AGM to appliance loads. Perhaps it's done by connecting the AGM to the lithium charge port bus rather than the discharge port bus. What is clear is that the AGM is being charged by the underhood generator with the Balmar regulator configured to charge lithium batteries, not an AGM battery.

Mumkin reports that there have been no Facebook reports of failure of the AGM battery. I'm not so sure since there is no AGM voltage indicator for the AGM and short of probing its terminals, there is no way to determine the condition of this battery. It could fail completely without any observable failure symptom unless and until you were attempting to effect a lithium BMS reset. Indeed, that was our experience. Fifteen months in, one of our lithium batteries failed and during its replacement it was determined that the even though the AGM battery was getting charging voltage, its resting voltage was about 5 volts. It was also replaced along with the lithium replacement and we are monitoring its condition. So far, so good.

What's caused this AGM failure is a vexed question. It could have been a bad battery from the get go or it could be related to the failed lithium battery.

The silver lining is that the factory quickly responded to the findings of our mobile tech and authorized the replacement of both batteries.

[GeorgeRa]

Originally Posted by avanti

If I were designing a DIY Lithium system today, I would take a close look at using a small Espar hydronic system as a cold weather backup. I could imagine a well-insulated battery compartment that also housed the expansion tank for the Espar. That way, there would be a lot of thermal mass to minimize cycling of the Espar. In the grand order of things, such a setup would not be all that expensive.

I am, of course, just making all of this up.

Indeed, not too expensive. A few coolant hoses, cupper tubing, clamps, know how, wires ($100) and for about $850 winterizing is done.

[booster]

Originally Posted by avanti

If I were designing a DIY Lithium system today, I would take a close look at using a small Espar hydronic system as a cold weather backup. I could imagine a well-insulated battery compartment that also housed the expansion tank for the Espar. That way, there would be a lot of thermal mass to minimize cycling of the Espar. In the grand order of things, such a setup would not be all that expensive.

I am, of course, just making all of this up.

I wonder if these would be less expensive, better sized, etc, and work the same.

https://www.eberspaecher-na.com/prod...t-heaters.html

[Boxster1971]

Originally Posted by booster

Interesting article, but the link is dead.

It sounds like they shut off the lithium, or at least the charging to it, at 5*C and run on the AGM, which makes sense, and the AGM would be there to get things going again. Also would eliminate the need for heaters, which they don't really have enough capacity to run anyway unless a charge source is active.

We don't know how the Roadtrek setup is wired, but parallel has been mentioned and in some way it has to be to get charged at the same time as the lithium. We don't know if it is on the charge or load side of the lithiums, though.

An interesting premise, especially the touting winter use. Roadtrek wouldn't be able to do that, though, as to have enough AGM to run all the stuff that takes power on them, with the reduced output of the AGM in the cold, they would have to have a quite large AGM bank.

Try this refreshed link - it should work.
https://www.eriba.com/assets/files/m...y%20System.pdf

[BBQ]

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The reason you do not hear the AGM failure is because the Li is always undercharged.

[JohnnyFry]

It didn’t work either...404 error

[GeorgeRa]

Originally Posted by booster

I wonder if these would be less expensive, better sized, etc, and work the same.

https://www.eberspaecher-na.com/prod...t-heaters.html

Eberspacher/Espar are slow in getting their latest product into the market. This new S3 is not available yet from Heatso UK. Newest controls are only available in EU. I doubt S3 will be less expansive than current models.