HQST Battery Dead or Alive?

[JeffK]

I'm not sure if this is a BMS wake up problem or not. I have two HQST (Renology?) LifePO4 batteries in our camper. On a recent trip our shunt was reporting 60% capacity then pretty quickly the voltage dropped and we lost power completely. When we returned, I left the batteries to recharge with our RV converter plugged in (it has a lithium charging profile). One battery seems ok, it recharged fully and I can run our camper on it without any issues. The other however, didn't recharge. I checked and there was a 14V charge applied to it but after 7 hours of charging it was still at 1V or so. I contacted HQST and they claim the battery needs to be activated with a suitable lithium battery charger. My understanding is that when charging the charger needs a sufficient battery voltage to know the battery is there before providing a voltage to activate the BMS. In my case however with the RV charge controller it provides a voltage (as I observed) regardless of the battery status. Is this sufficient to wake up the BMS or is there something else going on? I'm pretty sure I have a dead battery and nothing will revive it.

 

[sunshine_eggo]

So with the "bad" battery connected to the converter, you measure ~14V at the battery terminals? If so, your charger is working, and it should activate as they claim.

Send them a video showing terminal voltage with the converter attached and then with the converter removed. Evidence of a "bad" battery.

Furthermore, charging them in parallel would accomplish the same thing. If "good" battery charges while in parallel with "bad" battery, further evidence of a "bad" battery.

 

[JeffK]

Thanks! I wasn't sure if there was some trickle current required or black magic, etc. I wanted to be sure that applying voltage would be sufficient to activate it.

I anticipated that they would come back with this so I sent them pictures of the voltage being applied and the dead battery result. Maybe this didn't translate very well to Chinese. I'll try again, maybe with a video as you suggest for emphasis and point out that one did charge in parallel.

Unfortunately, we are leaving on a trip in a week and I doubt they can replace it in time even if they agree it's dead. I'm not sure how we'll do with one battery - we won't have shore power. I might see if I can get more solar or pack more bourbon.

I'm also a little worried that it failed after a few months. I don't think there was anything weird going on. I added a 500W inverter but it shouldn't draw more than the battery is capable of handling.

 

[sunshine_eggo]

Thanks! I wasn't sure if there was some trickle current required or black magic, etc. I wanted to be sure that applying voltage would be sufficient to activate it.

I anticipated that they would come back with this so I sent them pictures of the voltage being applied and the dead battery result. Maybe this didn't translate very well to Chinese. I'll try again, maybe with a video as you suggest for emphasis and point out that one did charge in parallel.

It's not about understanding, it's about producing evidence. A Video is harder to dispute.

Unfortunately, we are leaving on a trip in a week and I doubt they can replace it in time even if they agree it's dead. I'm not sure how we'll do with one battery - we won't have shore power. I might see if I can get more solar or pack more bourbon.

Definitely part of the solution.

I'm also a little worried that it failed after a few months. I don't think there was anything weird going on. I added a 500W inverter but it shouldn't draw more than the battery is capable of handling.

Likely an issue with the BMS. They're cheap electronics, and they fail. The only concern with an inverter is that you have a precharge circuit to prevent BMS overcurrent.

 

[JeffK]

Thanks, I'll work on my video skills and see where that goes.

I'm feeling fairly ignorant on inverters now. I installed the 500W Victron inverter with a 50A breaker (mostly to protect the wire as I understand it). In the Will video he does mention precharging isn't necessary for a lower wattage inverter like mine.

 

[sunshine_eggo]

Thanks, I'll work on my video skills and see where that goes.

I'm feeling fairly ignorant on inverters now. I installed the 500W Victron inverter with a 50A breaker (mostly to protect the wire as I understand it). In the Will video he does mention precharging isn't necessary for a lower wattage inverter like mine.

The video describes the concept and is focused on the hazards of the spark. With LFP batteries, there is an additional concern - the surge to charge the capacitors may trigger short-circuit protection in the BMS. Having a small wattage inverter and/or having dual batteries may mean it's not a concern in your case.

 

[JeffK]

I do feel better educated. I doubt with this camper we'd ever install a larger inverter unless we take a liking to fancy blender drinks and espresso maybe.

 

[JeffK]

An update... I jumped through a couple more hoops for HQST trying to charge the battery. It charges to 13.7V but under a load it will discharge quickly and the voltage drops to 2V or so. They agreed to replace it. They have been very responsive and I'm glad they stand by their product.

They said they no longer carry the battery I have and will replace it with the current model (https://hqsolarpower.com/12v-100ah-lifepo4-lithium-iron-phosphate-battery/). It appears to have the same specs. It will be in parallel with the old model, I assume this will be ok?

 

[sunshine_eggo]

Provided you have them connected in parallel properly (short, equal length, thick interconnects), and you use the (-) terminal of one and the (+) terminal of the other as your main battery terminals, should be good. Worth triple checking all connections for proper torque.

 

[JeffK]

you use the (-) terminal of one and the (+) terminal of the other as your main battery terminals

Thanks! I didn't know that. I might invest in some better battery cables as well.

 

[sunshine_eggo]

Thanks! I didn't know that. I might invest in some better battery cables as well.

If you don't pull off "opposite" ends "across" the battery, the current won't be equally shared.

Check the wiring unlimited link in my sig.

 

[JeffK]

Just confirming I did receive a new battery from HQST. They did not ask for the old one back. I'm happy with their customer service and that they back their product. The form factor is quite a bit larger than their old battery, but it will fit.