Lithium batteries jump start

[Kevin D Pem]

I can see that if the batteries have their own shut-down or the BMS is isolating them, the inverter wouldn't recognize them or be able to charge them. Odd system but it explains the situation. Hence “jumping” your house batteries. Weird. I would think this is a relatively common conundrum amongst RT owners.

Yes quite common with lithium BMS. They don't play nice with smart charging systems in general. That is why when I have (very seldom, as I discourage lithium) set up a lithium system. I use a basic cvcc charging system (buck converter).

 

[mwagon73]

After a few hours of charging everything is back and working properly. Thanks for the help here. Moving forward, It is parked in my driveway, and I typically leave it plugged into shore power. Just leave the house on with the inverter on? What's ideal?

 

[Kevin D Pem]

After a few hours of charging everything is back and working properly. Thanks for the help here. Moving forward, It is parked in my driveway, and I typically leave it plugged into shore power. Just leave the house on with the inverter on? What's ideal?

The BMS will not allow the battery to overcharge.

 

[Rich W.]

After a few hours of charging everything is back and working properly. Thanks for the help here. Moving forward, It is parked in my driveway, and I typically leave it plugged into shore power. Just leave the house on with the inverter on? What's ideal?

Yes because its an inverter/charger and it will keep the batteries charged. Otherwise anything that stays on and/or any parasitic loads will drain your house bank and you’ll be back where you started.

 

[BenHennig]

I too have a 2021 Roadtrek Zion with lithium batteries and I've had this very problem.

It sounds like your coach's AGM battery was drained too low and you couldn't get the Firefly to run, which means you can't get the inverter to turn on, nor can you get the lithiums to turn on. Further, the under-hood generator (UHG) won't charge things back up.

I've learned that in addition to the lithium coach batteries, we also have an AGM coach battery in parallel. The AGM provides several functions: 1) it powers the Firefly when the lithiums are off, 2) it provides some electricity to the under-hood generator (UHG) to get it going. Yes, the UHG needs some initial electricity to start generating electricity from the engine rotation. 3) it may do more than this... such as heating the lithiums if they are too cold to permit charging... I just don't know the details and don't want to spread bad info.

So if the lithiums + AGM is allowed to run down too far, first it can damage the AGM battery (about $300 for a replacement + labor; I just replaced mine this week!). The lithiums have a battery management system that will disconnect them automatically to prevent discharging them too low; the AGM does not. Second, there won't be power available to run the Firefly to turn on the inverter or lithiums, nor power available to get the UHG generating.

The fix isn't too hard. I'm disappointed this isn't covered in the Roadtrek manuals. From my own owner's notes (pardon any repetition):
----------------------
Draining the AGM battery to empty may reduce its life, perhaps drastically. The AGM has no protection to disconnect it from coach loads if it's charge drops too low. Even with the coach batteries disconnected (via the red battery switch), the AGM may still drain if there is a leakage path; the AGM is still connected to the electrical system (e.g. UHG), just not the coach loads (e.g. lights, fridge). Some RVs have a leakage path in the UHG which can drain the AGM with the battery disconnect activated. If your AGM died while the coach batteries were disconnected, this (or something else) may be the cause.

"Option 1: Use shore power.
You can use the shore power + the inverter to charge the AGM battery. Normally, you would use the Firefly to turn on the inverter, but in this case the Firefly is dead because the AGM is dead and the lithiums are off/dead. And you can't get the lithiums to turn on without the Firefly. Instead, you will have to turn on the inverter manually using the switch on top of the inverter. *Be sure to turn it back off after this procedure. Otherwise the inverter will be on all the time and that is a great way to drain your coach batteries.*

Connect to shore power. Turn on the inverter manually using the switch on top of the inverter. Engage the coach battery connect switch. You should now be able to turn on the Firefly and set it to turn on the inverter. At that point, you should be able to turn off the inverter's manual switch. Leave the lithium batteries off since you probably want to prioritize charging the AGM. After XXX time, try turning off the inverter to see what charge the AGM will hold. 12V or higher on the AGM under no-load conditions is decent. Note the true voltage from the AGM is best read after it has been left alone for a couple hours with no charging or load, and of course with the lithiums off. Let the AGM charge fully from either inverter (slower), or start the engine and use the UHG (faster). If you are using the UHG to charge the AGM you can turn off the inverter once the engine is running.

Once AGM is charged (I'm not clear on time here), you can try turning on the lithium batteries and charging them if needed. I suggest turning them on one at a time and checking the Network Diagnostics to ensure that the "Li 12V" indicator is green, which indicates that Li Battery is indeed reset and connected. Probably best to charge both lithiums together. You can use either the inverter + shore power (slower), or start the engine and use the UHG (faster) + no inverter."

"Option 2: Use jumper cables or a jump starter battery pack + the under-hood generator (UHG):
You can temporarily source 12V power to the coach via the inverter's terminals to get things going. Options for the 12V source includes: the chassis battery, another vehicle's 12V battery, or a jump starter 12V battery pack. If using the chassis battery, I'm told there are terminal connections under the engine hood. Alternatively, the chassis battery is accessible under the driver's floor panel.

Remove the black and red plastic caps on the inverter's terminals. (The inverter is located beneath the seat next to the fridge.) With the engine running, connect as you would a car battery. You should now be able to turn on the Battery Disconnect and turn-on the Firefly. You should now be able to disconnect the jumper battery. Keep the engine running to charge up the coach batteries. I'd keep the lithiums off for half an hour or so (?), so that all the charging is going to your AGM first.

Beware, you need to find out why your AGM drained so low. It may now be damaged and if so, will only retain a small capacity despite showing a high voltage. A recharge will bring it back to life, but maybe only momentarily. The biggest culprit in killing the AGM is leaving the inverter on, either by leaving the on/off switch on top of the inverter turned on, or by leaving it enabled via the Firefly control panel. The AGM will also lose charge over time with storage, either by self-discharging or by leakage paths in the RV; I'm using a battery tender to prevent this during storage.

 

[Rich W.]

Wow - excellent treatise. Far more in-depth than a dealer ever would, or probably even could give you. And even if they could they probably wouldn’t for fear of chasing off customers. Sounds like the R and D folks at Roadtrek need to spend a little more time at the drawing board. If I had a rig that operated like this I’d either fix it or at least carry a jump-starter device - they are handy anyway. This one had me scratching my head, but now I get it.

 

[AbdRahim]

That is why when I have (very seldom, as I discourage lithium) set up a lithium system.

ok. I have to ask. Why do you discourage Li batteries?

 

[BenHennig]

Thanks! Hope others find it helpful.

Indeed. I purchased a battery jumper pack just for this purpose and keep it ready as part of my kit. Good thing to have on hand regardless. I'm not terribly excited about connecting chassis battery to the coach battery, but it *should* work just fine.

My main wish is that Roadtrek put out better information on how their electrical system works and needs to be maintained. I've pieced together what I know from sources on the internet, which is not ideal as you have to sift thru conjecture vs. good info vs. real experience. Their docs aren't very clear how the AGM and lithiums work together. Further, some of their vehicles didn't have lithium batteries and instead have only AGM batteries... so when their documentation refers to AGM, it can be confusing whether they mean a vehicle with only AGM coach batteries, or the AGM battery that accompanies the lithiums. Or their docs show an older control interface which leaves you wondering how much of this info is applicable to my vehicle.

\end rant

 

[Kevin D Pem]

ok. I have to ask. Why do you discourage Li batteries?

The list is large but:

Not environmentally friendly. ( mining and refining)
Fire hazard, every thing that uninformed people recommend on forums can lead to a burned up coach.
Electronics failure is the largest failure point with a lithium battery, and that can lead to the above scenario.
The recycle system is well established with lead acid, and virtually non-existent with lithium batteries. Top that off with the toxic build, when disposed of improperly is just not an acceptable situation.

These things must by law be shipped with no more than 50% charge (what is the state of charge when you take your rig out?).
You are breaking the law if you ship lithium batteries installed in your device via USPS. do you just think that is just an overabundance of caution?

Did you know installing lithium system without certification will not be covered by the installers insurance?

Is that enough? I have more!

 

[AbdRahim]

There you go using that old school, outdated logic again. Shame on you.