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Old 05-23-2024, 07:15 PM   #1
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Battery, solar controller, or trailer wiring?

I have a Rockwood Signature 8263MBR with a Go Power GP-PWM-30-UL controller and 200 watt panel on the roof. The trailer came with two 81 Ah lead acid batteries that got very discharged this winter so I bought two 12V 100 Ah lithium batteries from LiTime. I charged and installed them in parallel according to LiTime’s manual. I covered the panel during installation then changed the controller to LFP prior to uncovering the panel. I monitor the batteries using the LiTime app.

All appeared well for a couple of weeks while the trailer sat at my house, sometimes plugged into shore power, sometimes with fridge and other appliances running. A couple of days ago I turned on the fridge and after several hours I checked batteries via the LiTime app. Only one of the batteries was discharging. I unplugged shore power and covered the panel. After a few more hours battery A was down to 70% SOC while battery B was still 100% and showing no discharge current.

I have spent two days reading manuals and trying different methods to make my batteries work together again. For a while today things appeared to be back to normal. I left the trailer with a small load on the batteries and only solar charging. When I came back after a couple of hours, the controller was flashing over voltage error and the problem battery’s BMS was in over-voltage protection mode. Only battery B has ever shown anything unusual. I should also mention that the controller manual says the battery negative should be wired directly to the controller. Our original batteries came with negative wired to chassis ground and changing that looks to be difficult. I did send an email to LiTime, but the response was hard to understand. So… what is the most likely culprit? Bad battery, bad controller, or improper wiring?
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Old 05-23-2024, 07:59 PM   #2
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Are the wires that feed your trailer split between the two batteries? IE positive to battery A and negative to battery B?
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Old 05-23-2024, 08:22 PM   #3
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Yes. I also tried changing which battery got the neg and which one was connected to pos. I also made new jumpers for the parallel connections, same length, 8ga, short as possible.
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Old 05-23-2024, 09:18 PM   #4
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Can you share the response you got from LiTime? It appears there are Chinese speakers on the other side of that communication. Their English is sometimes a bit difficult to sort out, but they have always been helpful to me, and after a re-read or two their meaning becomes clear.

What I have learned is that the LiTime BMS is fairly quick to place the battery into an over-charge protection disconnect. The instructions from LiTime is that to have the battery reconnect you simply draw a small current from it for a few minutes - around 2 to 5 amps. I consider this a "soft disconnect" mode. The disconnected battery still sources current and reads a (lower) voltage. An LiTime battery in BMS disconnect will measure about 12.9VDC even when fully charged. You might want to separate your battery bank and see what the individual battery voltages measure, and then try waking up the 100% battery with a small current (such as powering all the LEDs in your camper) for a few minutes. When the battery wakes up the voltage will increase to 13.4V. Once it wakes up, reconnecting your parallel batteries should see them equalize. HOWEVER, I don't like the idea of you reconnecting them with such a large SoC imbalance - the equalization current may be very large. I would re-charge the lower battery first and get them close before reconnecting.

I don't know why the two batteries in parallel are not staying equalized. If you haven't already you should ask LiTime CS specifically for an answer to that question. I presume that you fully charged the two batteries separately before connecting them into a battery bank. They should remain equalized from that point. I see the BMS disconnect state often (12.9V), and my battery bank wakes up easily (back to 13.4V). I assume that my 3 batteries are remaining in sync, but I do not have Bluetooth models, so I don't have the insight into each one as you do. I do know that all three are entering the disconnect state when fully charged, and all three are discharging at some point since I can get 90% of the capacity out of the bank according to my shunt. I just don't know if the three are going into and out of BMS disconnect at the same time.
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Old 05-23-2024, 09:30 PM   #5
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Also, if the solar controller triggered an over-voltage error, and if you did NOT have shore power connected when it did, then I think you also have a bad solar controller. I had a GP-PWM-30-SQ which was placing PV array voltage (20VDC or more) onto the battery terminals when the LiTime batteries went into BMS disconnect. Go Power quickly shipped me a warranty replacement for that controller when I contacted them about the issue.

So I think if your controller triggered the over-voltage error and there were no other charging sources connected, then the controller caused its own over-voltage condition.
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Old 05-23-2024, 09:58 PM   #6
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Reply to SparksPaul

I'm new to lithium batteries and am doing my first install of them in my Rockwood 35 footer. So my suggestion is not lithium specific.

If you undo the parrallel config and just connect one battery at a time you can maybe tell if its battery or controller. I have done alot of reading on these lithium batteries and it seems like the BMS is the source of a lot of problems. Cell phoneish reliability.

I spoke with a tech at WFCO about my converter and was warned that if my voltage drop was to much between converter and battery terminal, due to the cable run being to long or cable to small, that the BMS might reject charging. Makes no sense to me... but I'm not the expert.

My bet is BAD battery... Please post what you find out

Good luck
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Old 05-23-2024, 10:37 PM   #7
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Here is LiTime’s response:

Thank you contacting LiTime service, it's Ricket,i will be of your any assistance.
We would like to clarify that The minimum current that a Bluetooth battery can recognise is one amp, and when two batteries put out too little current, the Bluetooth device may not be able to monitor it
Thanks for your understanding.

I have been able to “wake up” the bad battery by separating and drawing current. When the batteries are separate, both seem to work fine when discharging. The problem battery will have over-voltage BMS disconnect when charging separately or connected in parallel with the other battery. The problem battery also frequently shows that it is “balancing” even when it is separated. The other battery has never had any fault messages.

I have been careful not to connect the two batteries unless the SOCs and voltages are close. The initial charge was done with a 0V charging function charger purchased from LiTime and batteries balanced according to the manual. The last over-voltage BMS happened when connected to solar only.

I think I have a bad battery and a solar charger that doesn’t work well with lithium. And I still have concerns about battery negative being connected to the frame instead of directly to the solar charger. Is that not an issue?
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Old 05-23-2024, 11:16 PM   #8
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That LiTime response is a bit cryptic. Actually, what was the question he was responding to?
I think you should ask him specifically about why the two parallel batteries are not remaining equalized and see how they explain that.

I agree the solar negative path might be a concern. If all the frame ground connections are solid it should be OK. But a direct conductor from the SCC to the battery, in addition to the battery connection to frame ground, is preferred. Did the factory really only connect the SCC negative output to the frame?

Do you have a shunt? You probably thought you didn't need one with the Bluetooth battery feature. I use the LiTime 500A shunt. It seems to be accurate and responsive to about 10 mA. The response about Bluetooth needing 1 amp or more is weird. The BT radio in the battery should just be a connection method for the app to communicate with the BMS' status, and I expect the BMS to have much more precision than one amp. Maybe that's a bad assumption.
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Old 05-23-2024, 11:31 PM   #9
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Connecting the battery negative sides to the frame, and also connecting the solar controller to the frame is not a problem IF all connections are good and the wire sizes are adequate (as noted by Jlankford. The problem is that connecting a copper wire to a steel frame is an iffy proposition. Corrosion at the point where the copper wire lugs are connected to the steel frame can introduce resistance and even result in an open circuit. This, even though the connections look good.

In this case maybe the 100% battery connection to the frame is not a good one.

If the PWM controller is not well connected to the frame (or both batteries aren't), it's output voltage could go high. Effectively it is operating with input from the panels but with no load.

What LiTime's Ricket was trying to say is that the LiTime BMS does not see current flow below one amp. It is normal to have a threshold below which current is ignored though 1 amp is surprisingly high. The Amphour counter thus won't see smaller currents (below 1 amp) flowing into or out of the battery. For instance, if you leave a full battery connected to a load of, say, 0.8 amps, the SOC reading will remain at 100% even though the battery will be discharging. A 100 Ah battery will hit 0% SOC in 125 hours with a 0.8 amp load. Likewise, charging may occur but the SOC reading will not change if the charging current is below 1 amp.

Losing track of SOC due to this one amp threshold is particularly likely with solar since the solar will not be putting out much current in the evening and early morning and might drop below 2 amps on a cloudy day or with trees overhead. I.e. if the batteries are sharing current equally, 1.9 amps of charge current will not be registered by the SOC monitor yet charging will be occurring. Likewise, less than 2 amps of load won't be recognized (with two batteries).

I'm not sure what made Ricket think your situation resulted from the SOC monitor not registering currents below 1 amp, but I think that is what he was thinking.

Check those frame connections. Redo them. They must be very clean. Use star washers. Cover with dielectric grease to keep air and moisture out. Or connect the solar controller to the batteries with some kind of busbar and connect that busbar to the frame. This is much preferred.
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Old 05-24-2024, 12:29 AM   #10
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Old 05-24-2024, 06:20 AM   #11
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Don’t know if others have said so….
8g parallel cables are pretty small I would use 2g or bigger

I bought a cable from west marine it was expensive but didn’t have to wait
Lugs were also high grade nickel plated copper

The cable to frame I left the size alone but ensured it was a good connection
Removed paint and star washer between frame and lug
The converter negative also was inspected and fixed

Charging/discharging
Look on your app to see if you have ability to change cell balancing mine is set to
“balance only when charging” is OFF
Balancing is performed during charging AND discharging
Anytime cells have reached 3.4 v

In the app can you check each battery’s over current protection make sure they are the same

Charge each battery separately to 100% I allowed overnight charging for each battery then connected in parallel

I don’t have inverter so my loads are small and batters remain even BUT I will see a small variation in charging performance…. Been watching it and always seams to even out at the end of the day

If you have high loads inverter
Make sure all lugs are clean…. Use sandpaper to remove any oxidation /dirt etc
Make sure lugs are flat and Torque each connection the same
Saw a good demonstration of how uneven lugs and torque has a big effect on amperage of the connection

If it keeps happening….. you might change the parallel configuration by having separate cables going from each battery to ta bus bar. Cables will need to be identical
Maybe use a 12v battery balancer
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Old 05-25-2024, 03:21 PM   #12
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Quick update: I sanded and cleaned the frame to bare metal where the negative cable from battery connects, then coated with dielectric grease. I could not find where the negative from the solar charger is attached. Somewhere under the floor and I am not ready to remove the protective liner yet. I bought two 18 inch 4ga jumpers from West Marine, the local store didn’t have heavier ones. So far I have tested my old flooded batteries by discharging and charging them with solar and shore power. I did not charge from both sources at the same time. They responded much better than I thought they would.

I tested LiTime battery B by discharging it from 100% SOC with 8.5A load for 2 hrs down to 83% SOC, 13.2 volts, measured with the LiTime app. I then charged it using shore power only. Charging current started at 9.5 amps then lowered as battery approached 100%SOC. After 2.5 hours, battery showed 99% SOC and was still being charged at 3A. After 10 hrs battery was 99% and with no charging current indicated. No faults were ever displayed during this process. I would consider all this to be normal. Am I wrong?

I am in the process of testing battery A now. So far it has performed the same as B. If it charges up without faults, my plan is to connect them in parallel (using my new jumpers) and let them sit overnight without connecting to the trailer. Then perform the same test that the separated batteries passed. If all goes well, then test again except this time use solar only for charging. Finally I would test again with both solar and shore active. This is sure time consuming.

I really appreciate the comments and advice. Any more suggestions are welcome.
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Old 05-25-2024, 03:37 PM   #13
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discharge the battery to about 50 % then see what amps you get from the converter/shorepower
if it stays at around 10 amps then your converter negative to frame needs the same work as the battery

unfortunately that connection may be underneath the underbelly

BUT... if you connected to shorepower... It's usually for a long period of time and charging speed is irrelevant...

Cell Balancing
if you can't change settings with Li-time app
try the overkill solar app for battery setup
it may connect to your BMS
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Old 05-25-2024, 04:59 PM   #14
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FWIW (probably not much!) But why with 200W of solar did your LA batteries get discharged over the winter? Could be some good reasons like they are old and shot or it was stored indoors not plugged in but you didn't say. Just sayin that outdoors in Nevada your LA batteries should not have discharged completely if your solar is functioning properly. That coupled with the overcharge shutdown would narrow the problem to the solar controller I would think.
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Old 05-25-2024, 05:13 PM   #15
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Main reason lead acid batteries died was I was unaware that turning off my 12v fridge doesn’t really turn it off. It comes back on after a power interruption. After winterization (northern Nevada) I disconnected my batteries to install a diode that will hopefully fix a trailer brake issue. When I reconnected batteries the fridge was now on and stayed that way most of the winter. During mid-winter my panel gets limited sun due to shadowing from my house and neighbor. Now I know to really turn of the fridge, I have to pull the fuse.
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Old 05-25-2024, 07:44 PM   #16
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Quote:
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Main reason lead acid batteries died was I was unaware that turning off my 12v fridge doesn’t really turn it off. It comes back on after a power interruption. After winterization (northern Nevada) I disconnected my batteries to install a diode that will hopefully fix a trailer brake issue. When I reconnected batteries the fridge was now on and stayed that way most of the winter. During mid-winter my panel gets limited sun due to shadowing from my house and neighbor. Now I know to really turn of the fridge, I have to pull the fuse.
t

Well that answers that! I am going to follow this as I am going to put Litime batteries in my FR3 and the solar controller I have is the exact same just with a different name on it. Crazy thing you have going on and hope you get it resolved soon! Good luck!
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Old 05-26-2024, 10:19 AM   #17
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Minor clarification point.
Early in the thread when equalization was discussed, it was in reference to both batteries equalizing to the same potential when paralleled. While that does occur with any battery, in a LiFePO4 battery, equalization controlled & monitored by that battery’s BMS only affect that individual battery. Ideally all cells within a battery bank will be fully charged the same but I doubt that will always occur. In the term, LiFePO4, the 4 stands for four cells per battery.
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Old 05-26-2024, 10:52 AM   #18
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Originally Posted by Boomerweps View Post
Minor clarification point.
Early in the thread when equalization was discussed, it was in reference to both batteries equalizing to the same potential when paralleled. While that does occur with any battery, in a LiFePO4 battery, equalization controlled & monitored by that battery’s BMS only affect that individual battery. Ideally all cells within a battery bank will be fully charged the same but I doubt that will always occur. In the term, LiFePO4, the 4 stands for four cells per battery.

A couple of errors to correct here...

The equalization mentioned previously (if by me) referred simply to the two parallel battery packages equalizing to the same relative voltage and presumably close to the same SoC. Nothing to do with individual cell equalization.

"PO4" refers to the chemical symbol for phosphate, not to the number of LiFePO4 cells installed into a multi-cell battery package.
A 24V LiFePO4 battery contains 8 (or more) individual cells. A 48V battery contains 16 or more cells.
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Old 05-26-2024, 11:15 AM   #19
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charge each battery one at a time to 100%
then when you connect them together in parallel there won't be a big difference in voltage
and the amp draw to get them the same voltage will be minimal

If you got a 1v difference in one battery
the amp draw will be high and the BMS may think there is short and shut down the battery

Have NOT experienced this as I make sure the batteries are fully charged (or same voltage) when they are connected

If the BMS is happy... then the 2 batteries will get to the same voltage
no need to do anything else... charger is NOT required either.

The more batteries you got.... the more important it is
to get your connections clean tight and cable size
so it is easy for the batteries to get to the same voltage

I see a small difference in battery amps in/out when my batteries are being used
pretty normal as each battery may just be a slightly different internal resistance
As long as the batteries eventually equals out things will be OK

Power HUNGRY people may have more problems
As there may not be enough time to allow batteries to equalize before you start drawing power again

you might consider using larger sized batteries so
instead of 4 x 100ah you only use 2 x 200ah


OR use large bus bars and wiring to allow quicker equalization between batteries
If in doubt ... and you want to use a lot of power have the system designed for you
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Old 05-26-2024, 11:27 AM   #20
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I see a small difference in battery amps in/out when my batteries are being used
pretty normal as each battery may just be a slightly different internal resistance
As long as the batteries eventually equals out things will be OK

Aussieguy, what brand of battery do you have and what granularity of current measurement is displayed in the Bluetooth app? Does the SoC reported by your Bluetooth app always agree with what is reported by your shunt? I think I've learned here in the last couple of days that the current/capacity usage reported by the BMS via Bluetooth may not be accurate enough to be trusted. I'm curious to learn about various brands' BMS accuracy...
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