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Old 06-10-2021, 12:06 PM   #1
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Observations on a LFP battery bank with incompatible OEM converter.

I'm out camping for the first time with my recently installed solar charging system and 2 x 12V 100Ah LFP batteries. We have shore power.

We started out with 90+% SOC but were continuously discharging the battery by a few amps. When we got up this AM, (after the second night) the SOC was down to 65%. This is with the converter on and batteries connected.

For the first two days we were here, the battery monitor showed 13.2V. I disconnected the batteries for the first time today and everything's running fine. The converter is working. I measured 13.6V at the OEM fuse block.

After reconnecting the batteries and disconnecting the solar panels my VOM measures 13.67 at the converter and 13.52 at the battery terminals, a 1.1% drop.

I surmise that the battery charge was high enough when we first started that the OEM charger was in FLA trickle mode. After disconnecting the battery it went to the higher 13.6 absorption range and, after reconnecting, stayed there.

I don't think I have reason to upgrade the OEM converter but I'm surprised by the discharging of the LFP batteries. I guess the V of the LFP batteries at full SOC is higher than the V of the converter in trickle mode, so the LFP batteries supply the amps.
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Old 06-10-2021, 02:34 PM   #2
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Quote:
Originally Posted by chriscowles View Post
I'm out camping for the first time with my recently installed solar charging system and 2 x 12V 100Ah LFP batteries. We have shore power.

We started out with 90+% SOC but were continuously discharging the battery by a few amps. When we got up this AM, (after the second night) the SOC was down to 65%. This is with the converter on and batteries connected.

For the first two days we were here, the battery monitor showed 13.2V. I disconnected the batteries for the first time today and everything's running fine. The converter is working. I measured 13.6V at the OEM fuse block.

After reconnecting the batteries and disconnecting the solar panels my VOM measures 13.67 at the converter and 13.52 at the battery terminals, a 1.1% drop.

I surmise that the battery charge was high enough when we first started that the OEM charger was in FLA trickle mode. After disconnecting the battery it went to the higher 13.6 absorption range and, after reconnecting, stayed there.

I don't think I have reason to upgrade the OEM converter but I'm surprised by the discharging of the LFP batteries. I guess the V of the LFP batteries at full SOC is higher than the V of the converter in trickle mode, so the LFP batteries supply the amps.
Do you know what model your OEM Converter is? I have a WFC8955 and am contemplating getting a 200AH LifePO4 battery.
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Old 06-10-2021, 03:09 PM   #3
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Do you know what model your OEM Converter is? I have a WFC8955 and am contemplating getting a 200AH LifePO4 battery.
I have the same. If you don't have solar panels you need a replacement converter/charger that is compatible with LFP batteries. Without that, they will never be fully charged. Drop-in converter replacements are easy to install if you've done any DIY projects. It does involve electricity but isn't complicated at all.

With a solar charge system, the converter won't charge the battery fully but the solar charge controller makes up the difference most of the time. For the times it doesn't, it doesn't hurt the LFP battery the same way that undercharging can damage a lead-acid battery.

Progressive Dynamics make a drop-in replacement that is often recommended here. I've never owned one so my knowledge is second hand. Other manufacturers exist. WFCO also makes one but, if you're paying the money, you might as well buy a better one from another manufacturer.

Some people disable the one in their OEM power center and install a separate deck-mount converter. I don't think there's a functional difference except that it might be easier to take with you if you upgrade your trailer and sell the current one. A deck-mount version may have other features, but it's definitely not a requirement.
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Old 06-10-2021, 03:15 PM   #4
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I actually do have a Victron 100/30 with 3 120w panels that I'll supplement. I just wasn't 100% sure my converter would at least keep the batteries somewhat charged. Good to hear someone else that has a similar setup I am looking to do and is working fine. My trailer is brand new so don't want to void the warranty by changing out the converter.

Thanks for the response!!
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Old 06-10-2021, 03:27 PM   #5
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Originally Posted by johnnynlin View Post
I actually do have a Victron 100/30 with 3 120w panels that I'll supplement. I just wasn't 100% sure my converter would at least keep the batteries somewhat charged. Good to hear someone else that has a similar setup I am looking to do and is working fine. My trailer is brand new so don't want to void the warranty by changing out the converter.

Thanks for the response!!
Some will tell you that you need a new converter. That is true, without a solar charge system. Because you have one, don't worry about it. The lower voltage trickle charge of the WF-8955 doesn't help the battery, but it doesn't hurt it, either. On low-solar days your generator will charge it to about 80% using the WFCO. My recall on the specific voltage is fuzzy. Others may contribute their knowledge.

One thing that will help a lot is to increase the size of the conductor from the converter to the battery. The standard #8 will drop a lot of volts on the way to the battery, if it's a long wire, hampering the charge process. I added a #4 in parallel to the OEM #8. The effective size is #3 with a measured 1% drop at 13.5 volts over 20'.

I posted my note because I was surprised that the LFP batteries can discharge even when connected to shore power. I can always disconnect the batteries and run off the converter but prefer to run our CPAPs off 12V. That way, if the power fails in the middle of the night (it happens) we continue our sleep undisturbed.
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Old 06-10-2021, 04:25 PM   #6
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Chris-

What brand/type solar controller do you have?

If a Victron, when you program it the "Absorption" phase has a time limit. You may want to increase that to a longer period as I think the default is one hour. This at least will allow you with your setup to achieve a higher level of SOC.

As long as you are able to charge fairly regularly to over 14 volts you should have no cell balance issues.

FWIW, my two Battleborns will drop to around 13.2 -13.3 volts when just running off the batteries with no solar panels deployed. They'll hang around that voltage for quite a long time until the batteries reach the lower "Knee" in the voltage curve.

For the benefit of others, this is why it's so important to have a good "Coulomb Counting" battery monitor with LiFePo4 batteries.
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Old 06-10-2021, 05:41 PM   #7
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Chris-

What brand/type solar controller do you have?

If a Victron, when you program it the "Absorption" phase has a time limit. You may want to increase that to a longer period as I think the default is one hour. This at least will allow you with your setup to achieve a higher level of SOC.

As long as you are able to charge fairly regularly to over 14 volts you should have no cell balance issues.

FWIW, my two Battleborns will drop to around 13.2 -13.3 volts when just running off the batteries with no solar panels deployed. They'll hang around that voltage for quite a long time until the batteries reach the lower "Knee" in the voltage curve.

For the benefit of others, this is why it's so important to have a good "Coulomb Counting" battery monitor with LiFePo4 batteries.
Mike, I have an Epever Triron controller. I set the Absorption phase to the max duration which is 3 hours.

I'm not worried about how the controller works or if the battery gets fully charged. I was just surprised that the batteries would discharge while the converter was working. I believe it does because the charger voltage at float level is less than the voltage of the battery. I just didn't think about it.
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Old 06-10-2021, 05:49 PM   #8
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Originally Posted by chriscowles View Post
Mike, I have an Epever Triron controller. I set the Absorption phase to the max duration which is 3 hours.

I'm not worried about how the controller works or if the battery gets fully charged. I was just surprised that the batteries would discharge while the converter was working. I believe it does because the charger voltage at float level is less than the voltage of the battery. I just didn't think about it.
This is it. When the LiFePo4's have reached the float voltage of the Converter the converter will handle the load with batteries handling any surge. A state of equilibrium has been reached and won't really change until the Converter is out of the picture and the Solar Controller takes over. It MAY be necessary to shut down solar and restart in order to force the controller back into bulk mode if it doesn't do it automatically when the converter is off line. Depends on what the lower threshold is for it to switch to Bulk on it's own. It may well do it on it's own when you disconnect shore power then run in slides, etc. that will cause the voltage to sag below that threshold. Time will tell.
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Old 06-11-2021, 02:04 PM   #9
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This is it. When the LiFePo4's have reached the float voltage of the Converter the converter will handle the load with batteries handling any surge. A state of equilibrium has been reached and won't really change until the Converter is out of the picture and the Solar Controller takes over. It MAY be necessary to shut down solar and restart in order to force the controller back into bulk mode if it doesn't do it automatically when the converter is off line. Depends on what the lower threshold is for it to switch to Bulk on it's own. It may well do it on it's own when you disconnect shore power then run in slides, etc. that will cause the voltage to sag below that threshold. Time will tell.

Titan Mike, I just posted with similar questions at: Battery Charging, Solar vs WFCO Conv/Chrgr (Sorry, I don't know how to post a link)
. Your input on this thread is very interesting, but I am unclear on some of it, as follows:
1) Could you clarify "the converter will handle the load with batteries handling any surge" ?What Surge?
2) Could you clarify "Converter is out of the picture and the Solar Controller takes over? How is the Converter out of the picture?
3) How does one "shut down solar and restart in order to force the controller back into bulk mode if it doesn't do it automatically" ?
4) What does "lower threshold" mean: "lower threshold is for it to switch to Bulk on it's own"
5) What equipment will "do it on it's own when you disconnect shore power ?
. Sorry, I seem to be un-informed on some of this subject and would really appreciate a simple tutorial.

. Rod
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Old 06-11-2021, 04:47 PM   #10
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Titan Mike, I just posted with similar questions at: Battery Charging, Solar vs WFCO Conv/Chrgr (Sorry, I don't know how to post a link)
. Your input on this thread is very interesting, but I am unclear on some of it, as follows:
1) Could you clarify "the converter will handle the load with batteries handling any surge" ?What Surge?
2) Could you clarify "Converter is out of the picture and the Solar Controller takes over? How is the Converter out of the picture?
3) How does one "shut down solar and restart in order to force the controller back into bulk mode if it doesn't do it automatically" ?
4) What does "lower threshold" mean: "lower threshold is for it to switch to Bulk on it's own"
5) What equipment will "do it on it's own when you disconnect shore power ?
. Sorry, I seem to be un-informed on some of this subject and would really appreciate a simple tutorial.

. Rod
I can answer some of those.

1) When at the equilibrated voltage, the converter will keep the battery at that same voltage. The converter has a limited amp output. It will fill demand up to that point. When you plug in or turn on more things, the converter can't produce any more, so the battery makes up the difference.

2) I'll leave this to Mike.

3) A good solar charge system design allows you to shut off current flow from the solar panels. Manipulating the system voltage by doing so may trigger the converter's algorithm for when it changes voltage levels within its (assumed) three stages. See this explanation by WFCO. Take into consideration that it is marketing information.

4) The diminished voltage level at which the manufacturer's algorithm senses the need to switch to the highest voltage level. For WFCO, that's 14.4. LFP batteries generally need 14.6 to be fully charged.

5) Without shore power, the battery is the power source. High-current demands like slide or jack motors will cause voltage to drop, if even transiently. The charger is still connected to the battery, even though it has no means of charging it. The voltage sag may trigger the charger to revert to bulk mode when shore power is restored.

In my experience on this trip, disconnecting the battery while on shore power caused the WF-8955 to increase voltage from 13.2 (trickle) to 13.6 (nominal operating voltage). After reconnecting the battery, it stayed there but I didn't track how long it stayed at 13.6 before dropping back to 13.2. I don't even know if it did. In the link above, WFCO states that happens in their system "if the converter detects no significant variation in current draw for approximately 44 continuous hours". My having disconnected the battery apparently restarted the clock on those 44 hours.
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Old 06-11-2021, 04:50 PM   #11
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Titan Mike, I just posted with similar questions at: Battery Charging, Solar vs WFCO Conv/Chrgr (Sorry, I don't know how to post a link) ...
Link: Battery Charging, Solar vs WFCO Conv/Chrgr
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Old 06-11-2021, 06:16 PM   #12
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I can answer some of those.

1) When at the equilibrated voltage, the converter will keep the battery at that same voltage. The converter has a limited amp output. It will fill demand up to that point. When you plug in or turn on more things, the converter can't produce any more, so the battery makes up the difference.

2) I'll leave this to Mike.

3) A good solar charge system design allows you to shut off current flow from the solar panels. Manipulating the system voltage by doing so may trigger the converter's algorithm for when it changes voltage levels within its (assumed) three stages. See this explanation by WFCO. Take into consideration that it is marketing information.

4) The diminished voltage level at which the manufacturer's algorithm senses the need to switch to the highest voltage level. For WFCO, that's 14.4. LFP batteries generally need 14.6 to be fully charged.

5) Without shore power, the battery is the power source. High-current demands like slide or jack motors will cause voltage to drop, if even transiently. The charger is still connected to the battery, even though it has no means of charging it. The voltage sag may trigger the charger to revert to bulk mode when shore power is restored.

In my experience on this trip, disconnecting the battery while on shore power caused the WF-8955 to increase voltage from 13.2 (trickle) to 13.6 (nominal operating voltage). After reconnecting the battery, it stayed there but I didn't track how long it stayed at 13.6 before dropping back to 13.2. I don't even know if it did. In the link above, WFCO states that happens in their system "if the converter detects no significant variation in current draw for approximately 44 continuous hours". My having disconnected the battery apparently restarted the clock on those 44 hours.
Chris,
. Thanks for the thorough clarifications, much appreciated. It seems you and I are traveling the same path here. I hadn't thought of disconnecting the battery to force the Converter to reset.
. In your OP you mention "disconnecting the solar panels", how did you do this? This would also be a good tool to evaluate the Converter output.
. Thanks so much for you help.


. Rod
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Old 06-11-2021, 07:45 PM   #13
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Chris,
. Thanks for the thorough clarifications, much appreciated. It seems you and I are traveling the same path here. I hadn't thought of disconnecting the battery to force the Converter to reset.
. In your OP you mention "disconnecting the solar panels", how did you do this? This would also be a good tool to evaluate the Converter output.
. Thanks so much for you help.
Rod, my solar charging system is DIY. I included a breaker on the wire from the solar panels, immediately before the charge controller. The easiest thing for you to do would be to add a disconnect switch on the solar charge wire at the battery. That allows you to isolate the charge control current from the OEM power center. (So does taking the positive solar cable off the battery. )

Don't obsess over this. Understand it well enough to optimize how the present system works, but focus on all the other stuff you need to figure out about your new trailer. The fact that you have LFP batteries and any solar charge system at all puts you at a significant advantage over any other boondocker with flooded lead acid batteries and no solar charge system.

After you've used it for awhile you can decide whether or not you want to change it. In the meantime, enjoy camping. That's why you bought the trailer.
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Old 06-11-2021, 08:28 PM   #14
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Titan Mike, I just posted with similar questions at: Battery Charging, Solar vs WFCO Conv/Chrgr (Sorry, I don't know how to post a link)
. Your input on this thread is very interesting, but I am unclear on some of it, as follows:
1) Could you clarify "the converter will handle the load with batteries handling any surge" ?What Surge?
2) Could you clarify "Converter is out of the picture and the Solar Controller takes over? How is the Converter out of the picture?
3) How does one "shut down solar and restart in order to force the controller back into bulk mode if it doesn't do it automatically" ?
4) What does "lower threshold" mean: "lower threshold is for it to switch to Bulk on it's own"
5) What equipment will "do it on it's own when you disconnect shore power ?
. Sorry, I seem to be un-informed on some of this subject and would really appreciate a simple tutorial.

. Rod
In #2 I was referring to when shore power disconnected or converter turned off.
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