Victron Phoenix Charger Ghost Temperature Sensing

[JeffKim]

Just on the off-chance anyone who has or knows Victron equipment, I'm curious how my Victron charger senses temperature without any temperature sensors in the VE Network. I replaced the stock WFCO charger with a Victron Smart Phoenix 50A which is working like the champ it is. We have the trailer plugged in and I disconnected the batteries since with our bargain-basement lithium batteries I don't entirely trust the BMS to prevent cold temperature charging. This frosty morning the inside lights didn't come on and the battery switch light is out. Since for various reasons I think our trailer is cursed, I'm thinking "great, another problem I get to deal with". I checked the breakers, fuses, etc. Then I switched on the batteries and the lights were working but checking the charger it had a message that it wasn't charging because the temperature is too low (<5C).

A light went on in my head and I figured out the charger wasn't powering anything because of the low temperature cutoff. However, I don't have any temperature sensors attached to the shunt or the solar controllers; the charger was correct and shut down, but I don't know how it sensed temperature. (There is an option to enable the low temperature cutoff which I now have disabled.)

[dznf0g]

First, if I understand your post correctly, I wouldn't turn off low temp cutoff. Lithium can be discharged cold but not charged cold.
Second, if I remember correctly, the victron solar controller has an AMBIENT temp sensor. While in the ballpark, it does not tell you internal battery temperature, which is what you really want. If your batts don't have internal sensors, I'd recommend the victron Battery Sense. It is affixed to the side of that battery and the other victron components utilize its reading over the network. Still not internal batt temp, but closer. I made a Styrofoam "box" to cover my sensor and adhered it to the batts to try and not pick up ambient temps as readily. I have agms, so incremental temp changes are more important than with lithium.

The Phoenix may have an ambient sensor as well. Do you see a temperature on the app?

[JeffKim]

Thanks, I might not have provided enough details. The batteries are supposed to have a BMS with a low-temperature charging cutoff, but I've never tested it. We don't do any low-temperature camping, so I disconnected the batteries for the winter. However, I do need the temperature cutoff disabled on the charger/converter or we won't be able to run the lights or anything DC when plugged in if it's below 5C (41F).

I can't find anything in the Phoenix readings for temperature so that's why I don't think it has a sensor. I might look into the Victron battery sense, it's not too expensive ($39) and probably more accurate than my "ghost" sensor. I can disconnect the batteries and override the temperature cutoff if I want to run the converter.

[dznf0g]

Page 3 of the manual seems to indicate the Phoenix has a temp sensor.
What I don't like about the sensor at the charger/controller is:
1) the mass of the battery means that it doesn't change it's internal temperature as quickly as it's surroundings.
2) the charger heats up with use, giving a false high reading
3) a battery will heat up internally with higher loads, which isn't accounted for at the charger sensor, making inaccuracies .

Ideally, an internal battery sensor is most accurate, but that's not possible after manufacture.

I'd say a victron smart battery sense is your best option.

[gypsydad]

What type (brand/size) Li batteries did you get and what did you pay if you can share? Also, why would they cut off at 40~ degrees?? (did I read that correctly)

[JeffKim]

Originally Posted by dznf0g

Page 3 of the manual seems to indicate the Phoenix has a temp sensor.
What I don't like about the sensor at the charger/controller is:
1) the mass of the battery means that it doesn't change it's internal temperature as quickly as it's surroundings.
2) the charger heats up with use, giving a false high reading
3) a battery will heat up internally with higher loads, which isn't accounted for at the charger sensor, making inaccuracies .

Ideally, an internal battery sensor is most accurate, but that's not possible after manufacture.

I'd say a victron smart battery sense is your best option.

Thanks for checking. I think that is a different Phoenix model. This is the manual for my model (see pages 8-9). It can use an internal temperature for varying voltage for charging lead-acid batteries but this is disabled for lithium. Maybe in the absence of any other battery temperature sensor in the network it uses the internal one?

Under Temperature Compensation the implication is that there is an internal temperature sensor:

During power up the charger will measure its internal temperature and use that temperature as the reference for temperature compensation.

Under VE.Smart Networking:

Temperature Sense uses battery temperature data that is accurately measured directly at a battery terminal or on the battery body and provides it to the charger.

But yes, I'll order the smart battery sense.

[JeffKim]

Originally Posted by gypsydad

What type (brand/size) Li batteries did you get and what did you pay if you can share? Also, why would they cut off at 40~ degrees?? (did I read that correctly)

I settled on HQST. I paid $279 for them but they're on Amazon for $199 (!). I rationalized that with the number of charge cycles we do in a season, it wasn't worth paying for the high price brand. They come with a 10-year warranty (I know, probably not worth anything).

I bought two for our dearly departed Bambi in 2022 and one stopped holding a charge. After a little finagling and back and forth they replaced it for free with the newer version/model (the current version that I have now in our Globetrotter). They have a domestic warehouse and their customer service is in China, but they were very responsive. So far, after one season I haven't had any issues.

The Victron Charger had a cutoff at 40F (configurable), with these they claim the BMS charging cuts out at 23F.

[dznf0g]

I mentioned upthread that I made a small insulated "box" for the victron smart sense unit affixed to the side of one of my batteries. Attached is a pic of that small mod. It was made from the corner of one of those thick Styrofoam food delivery boxes. I cut a corner out of the box and made the other side piece cutouts, glued them together with silicone, covered the inside and outside with aluminum duct tape and siliconed the cover to the battery side over the sensor. Seems to be effective in reducing the ambient trailer trailer temp swings relative to the actual battery temp.

[JeffKim]

Interesting, I posted to the Victron forums and got a response from Victron:

There's a fix in v2.46 for occasional erroneous battery temperature broadcasts on VE.Smart networking, causing chargers on the same network which are configured for low temperature cutoff to stop charging. These erroneous temperature broadcasts can occur even when no temperature sensor is configured.

I have v2.46 in the SmartShunt, but v2.44 in the SmartSolar chargers but no option to upgrade to v2.46. I'm awaiting a response.

[JeffKim]

Originally Posted by dznf0g

Seems to be effective in reducing the ambient trailer trailer temp swings relative to the actual battery temp.

Thanks, seems like a good idea. Are you able to get temperature readings from the Battery Sense in the Victron app? When I get to it, I think I might try gently blasting it with a hair dryer and see how insulated it is.

[dznf0g]

Originally Posted by JeffKim

Thanks, seems like a good idea. Are you able to get temperature readings from the Battery Sense in the Victron app? When I get to it, I think I might try gently blasting it with a hair dryer and see how insulated it is.

Yes, it appears to me after observations that when a SmartSense is on the network, it is the Master for temp for all components on the network (not voltage, each component has its own voltage reading so you can see drops to that component...however the SmartSense is true batt voltage, as it is hooked directly to the posts).

Judging by comparing daily ambient temp swings in the AS to the temp swings of the SmartSense, the insulated cover box is pretty effective in judging internal battery temps. Not as accurate as internal battery sensors, but as close as one can get, IMO.

[JeffKim]

To close this out, I did get a response from Victron. Apparently, this is a defect. Temperature sensing shouldn't have happened with the charger and they say it probably originated from the shunt. They want me to file a service report however this morning it's 28F and I'm not getting the same behavior with the temperature cutoff - it's powering the DC components and not shutdown. I'll check again in a few days, but whatever it was seems to have gone away. Also, I think the Battery Sense is the way to go anyways, so I'll add that.

[JeffKim]

Epilogue: I found out the battery sense isn't the only option. Much simpler I got a temperature sensor for the Smart Shunt ($30) and installed it this weekend. The sensor attaches to the battery terminal, so maybe not getting the correct internal temperature, but better than nothing. I set the charger to cutout to 32F. As I stated I don't entirely trust the BMS in my bargain-basement batteries and this is extra insurance.