A different lithium battery heater setup

[mojoman]

I understand why Roadtrek would use AGM to heat their batteries. My system is wired the same way except my lithium batteries are usable when freezing, It won't let me charge them till they are within temperature parameters. I'm surprised ARV can't prevent charging when freezing but still allow use. It would only require a low temp solenoid cutout of the charging circuit upon which a load would self heat the batteries eventually. $150 in parts at the most.

[avanti]

Originally Posted by mojoman

I understand why Roadtrek would use AGM to heat their batteries. My system is wired the same way except my lithium batteries are usable when freezing, It won't let me charge them till they are within temperature parameters. I'm surprised ARV can't prevent charging when freezing but still allow use. It would only require a low temp solenoid cutout of the charging circuit upon which a load would self heat the batteries eventually. $150 in parts at the most.

Just to prove to DavyDD that we understand how his van works:
ARV DOES prevent charging when below freezing. What they do wrong is to not provide the ability to power their heating pads from shore power, the chassis battery, or the vehicle generator. This would cost more like $40 and would permit a cold boot under all circumstances without resorting to the kind of hacks that DavyDD thinks are reasonable.

[booster]

Originally Posted by mojoman

I understand why Roadtrek would use AGM to heat their batteries. My system is wired the same way except my lithium batteries are usable when freezing, It won't let me charge them till they are within temperature parameters. I'm surprised ARV can't prevent charging when freezing but still allow use. It would only require a low temp solenoid cutout of the charging circuit upon which a load would self heat the batteries eventually. $150 in parts at the most.

Actually, it appears that the ARV setup does allow use of the batteries when cold, but no charging. The issue we have been discussing is under certain circumstances like if the van has cold soaked to a very low temperature. The batteries will come on, but the 10 amps of heat from the batteries won't get the batteries warm enough in the very cold and coming from ambient. If the batteries are low, it is even less likely to get going, and output of lithium drops with temp like other batteries, it appears. With no other way to heat the batteries than off the batteries, ARV winds up very limited in reheating to charge temp, compared to Roadtrek that can use the engine running to do it. With the ARV, you would have to go someplace warm to get to charging temp on the batteries.

What method(s) do you have to warm the batteries if they are in cold shutdown?

[mojoman]

The batteries are inside the coach, bottom insulated, using 12v seat heating elements, about 60watts. They may never get that cold since they are indoors.

[booster]

Originally Posted by mojoman

The batteries are inside the coach, bottom insulated, using 12v seat heating elements, about 60watts. They may never get that cold since they are indoors.

Will you be able to power the heaters if the batteries are in cold and/or low charge cutout, off shore or engine power?

[mojoman]

I have an auxiliary 70ah AGM that can be charged by solar, alternator, shore power both (15 or 30 amp service) or generator. The small AGM battery powers the 12v system while traveling, fridge, fan, water pump etc...The lithium pack has the same options for charging but on a larger scale.

[mikes47]

Do I understand correctly that the gap in ARV's design is that ARV fails to provide a secondary, back-up method to warm the Lithium batteries in the event that the primary, interspersed heaters fail?

[avanti]

Originally Posted by mikes47

Do I understand correctly that the gap in ARV's design is that ARV fails to provide a secondary, back-up method to warm the Lithium batteries in the event that the primary, interspersed heaters fail?

No. The belief is that there is no way to power those heaters in the event that the batteries need charging in cold weather after the vehicle has been shut down (e.g., after storage).

[gregmchugh]

As a point of reference, there is a report that Roadtrek has two 2 amp heating pads in each 200 amp hour Ecotrek battery module. ARV is reported to have two 5 amp pads in an 800 amp hour battery bank, so this would be 10 amps vs 16 amps in an 800 amp hour Ecotrek system. And Roadtrek does allow battery discharge below freezing p, they just prevent charging at low temps. With two 12 volt connections on the Ecotrek, one for charge sources and one for loads and both likely with relays they can control them separately. My gyess is that the battery heaters may be powered from the charge source input before the relay so they are powered while the batteries are isolated from the charge sources as needed. Just my guess in a likely configuration.

[wincrasher]

Greg, sizing of the heating pads is likely a function of the design of the battery enclosure. The ARV battery enclosure is a thing of beauty - a large, well insulated enclosure. All the batteries are together in this casing.

I can't really speak to the casing on the Roadtrek other that what I've observed - it looks to be a metal casing about the size of individual "drop-in" batteries. I can only assume the insulation is minimal considering the size. You get multiple modules based on the size of the pack you ordered. So batteries really can't share in each other's heat, which I assume is possible in the ARV setup.

[booster]

The lady on Yahoo just posted that Roadtrek confirmed that the batteries only will heat off the engine generator, if they are in cold shutdown. Once warm if they are on and the inverter on, they will then heat off shore power. Stated 40 watts (200ah pack) and 2 hours to heat from -13C (8*F). I assume while you are driving to warm the batteries the engine generator would be supplying the coach, or you would have no frig, etc. If it was -20*F, I wonder if they would ever get warm? You would need to run the engine overnight.


Just don't go anywhere closer than 2 hours if want shore power to charge, I guess.

I would hope they change this, though, as with AGM there, it should be easy to do.

Maybe a battery charger on the engine generator output so could warm when AC available to preheat before leaving.

[avanti]

Better than nothing.
But, if I owned one, I would mod it in a heartbeat. How hard would it be to directly power the heater from shore power via a manual switch? I don't know whether the pads are AC or DC, but either way...

[booster]

Originally Posted by avanti

Better than nothing.
But, if I owned one, I would mod it in a heartbeat. How hard would it be to directly power the heater from shore power via a manual switch? I don't know whether the pads are AC or DC, but either way...

Me too. Can't be that difficult.

[gregmchugh]

As I suspected, the heaters are powered from the 12 v charge connection into the Ecotrek before the relay. The new information is that the inverter/charger appears to be connected to the 12 volt load connection so it is not powering the heaters. The AGM is likely connected to the charge side along with the aux alternator. Final piece of the puzzle is the solar charge controller connection which would likely go to the charge connection. I assume they protect the lithiums from the shore battery charger when below temperature by sensing charge level voltage on the load connection and disconnecting with the relay on that side.

[booster]

Originally Posted by gregmchugh

As I suspected, the heaters are powered from the 12 v charge connection into the Ecotrek before the relay. The new information is that the inverter/charger appears to be connected to the 12 volt load connection so it is not powering the heaters. The AGM is likely connected to the charge side along with the aux alternator. Final piece of the puzzle is the solar charge controller connection which would likely go to the charge connection. I assume they protect the lithiums from the shore battery charger when below temperature by sensing charge level voltage on the load connection and disconnecting with the relay on that side.

I guess the part that doesn't make sense is if it is OK for the alternator to connect to the charge side, why not the shore charger. If the AGM is there, it should activate either of them. The load side stays disconnected so that means no frig or anything else until the batteries get warm. I would think if there are relays on charge and load, they could tie them together in lockout and have shore power or alternator run the coach in conjunction with the AGM. Definitely seems that the AGM was a quick fix and not all that well integrated.

[gregmchugh]

Originally Posted by wincrasher

Greg, sizing of the heating pads is likely a function of the design of the battery enclosure. The ARV battery enclosure is a thing of beauty - a large, well insulated enclosure. All the batteries are together in this casing.

I can't really speak to the casing on the Roadtrek other that what I've observed - it looks to be a metal casing about the size of individual "drop-in" batteries. I can only assume the insulation is minimal considering the size. You get multiple modules based on the size of the pack you ordered. So batteries really can't share in each other's heat, which I assume is possible in the ARV setup.

Agree but is there a risk of having them too well insulated and having them overheat? No one has active cooling for the over temp case do they, I mean besides the electric vehicles?

[booster]

Originally Posted by gregmchugh

Agree but is there a risk of having them too well insulated and having them overheat? No one has active cooling for the over temp case do they, I mean besides the electric vehicles?

I would think they should be on a thermostat, but who knows in the secretive world of magic boxes

[gregmchugh]

Originally Posted by booster

I guess the part that doesn't make sense is if it is OK for the alternator to connect to the charge side, why not the shore charger. If the AGM is there, it should activate either of them. The load side stays disconnected so that means no frig or anything else until the batteries get warm. I would think if there are relays on charge and load, they could tie them together in lockout and have shore power or alternator run the coach in conjunction with the AGM. Definitely seems that the AGM was a quick fix and not all that well integrated.

I believe there are relays on both 12 v connections and I had guessed that the inverter was on the charge side but this new info indicates otherwise. There have been reports that the batteries can still be discharged at low temp when charging is disconnected. Having the inverter on the load side would allow 120 v loads to be powered from the inverter at these low temps along with the 12 volt loads including the fridge. Yes, connecting the charge side to the load side and bypassing the batteries would be another option to power the van while warming the batteries. Lots of things to still understand about the operation of the current configuration.

[gregmchugh]

Originally Posted by booster

I would think they should be on a thermostat, but who knows in the secretive world of magic boxes

The heaters are surely on a thermostat and do not operate when the batteries are above 40 deg or so. Some people seem concerned about batteries operating at high temps and getting reduced life cycles. I expect there may be an auto high temp shutdown at some point. Maybe no issue from over insulating the battery bank to reduce low temp problems and a resulting risk of not keeping the batteries cool enough on hot days. Next summer we will see what happens. Any reduction in life cycles due to heat may not be significant for most users over normal ownership lifetime.

I am sure Davydd will chime in with data on the max temps he has seen on his batteries in the ARV configuration and how there is no issue in his configuration.

[wincrasher]

Originally Posted by gregmchugh

Agree but is there a risk of having them too well insulated and having them overheat? No one has active cooling for the over temp case do they, I mean besides the electric vehicles?

Greg, I don't think the issue is the batteries generating any appreciable heat while in use. The insulated casing keeps the generated heat from the pads inside, but also shields the batteries from summer heat outside.

It appears that it works well enough not to need a liquid cooling system like the electric cars. Davydd's been to some really hot places and hasn't reported any high temp alarms. How hot is too hot? There's alot of debate about that.

Technomadia sat in the desert heat for weeks at a time and did essentially nothing to mitigate baking their batteries.