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Old 06-06-2021, 04:43 PM   #1
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Lithium Battery Confusion

I recently read a lengthy thread regarding conversion from AGM to lithium for the house battery for a Ford E350 van. Although I know a little about automobile electrical systems (maybe I should say I used to know a little but maybe not so much now) the post and responses were way over my head.



So, my question is this. I have a E350 sportsmobile with the powerstroke diesel engine. It was originally wired with the standard sportsmobile solar controller. After I owned it a few years, I had Sportsmobile install the solar panel I had originally deferred. It has worked great, but I'm looking to upgrade to a lithium battery.



The other post had a great deal of information regarding upgraded components throughout the electrics. Is this really necessary or is there a lithium battery that would be a simple one-to-one replacement for my AGM battery? If it would require a different controller or upgrade to my alternator and/or wiring, I would rather just replace the AGM when necessary.



There was also info in a reply about carbon foam batteries, which are completely new to me. Any advice about replacement with either lithium or carbon foam would be welcome.
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Old 06-06-2021, 05:31 PM   #2
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Early on the word was to go with stuff that had a lithium charge profile, normally this was a two stage charge, nor float. As information moved on the Lithium battery manufactures have all decided they can handle a float charge as long as it a certain voltage. This just happens to mean that most of the previous chargers will work for lithium. There is a caveat, although they will work, pay attention to the specified voltage requirements for (Absorption, Float) for the Lithium battery you are looking at. If your charger can't match up pretty closely, then as with all things battery, you will be cutting the lifespan of the battery. You might not get that high life cycle count that they advertise. With the cost coming down, that may not be as big of issue as it was a couple of years ago.

Now, the thing that I still recommend to change, the alternator to house charging. If you have a ACR, Separator, or isolator, you will need to change to some other device. I highly recommend a Battery to Battery charger, to go between the alternator start battery, and the house battery. This will be a buffer between the two different battery technologies and also be better for the alternator.

There are some ACR like devices that actually monitor some parameters to make sure the lithium battery does not get overcharged. My general recommendation would be not to go the direction. I'm sure that there are some people here, that have them and may say otherwise.

You should make sure that you size the Battery to Battery charger correctly, so as to not overtax your alternator ( The major concern being at idle). In general this was the same with a ACR. If your current ACR is cutting out at idle you may need to do some further investigation and choose a unit that can help manage that or possible a bigger output alternator.

So I wouldn't say they plug and play compatible, but certainly getting closer.

-greg
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Old 06-06-2021, 06:29 PM   #3
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As far as the Carbon Foam option, you would not have to change out any of your electronics (but if you don't already have a high output Alternator as Scalf77 suggests, that may be something you'll want to do in either case).
The carbon foam allows you to draw down to 80% SOC similar to the Lithium. They have about 3X the lifecycles as AGM, but only half of Lithium, and Carbon Foam is a little more expensive than AGM but cheaper than Lithium...so they become a good compromise.
Carbon Foam has become very popular in the Marine industry. I believe some of this is associated with the cost of upgrading electronics to cooperate with the change to Lithium, along with the perception of potential fires developing with Lithium (true or not, people still make comments as such - If a fire starts on a boat, its a little different than a vehicle...you don't just open the car door and walk to safety...more obstacles/issues to consider).
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Old 06-07-2021, 11:59 PM   #4
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with lithium and solar, you need a controller that can handle a situation where the bms activates. A bms activation whether from out of balance, over temp will cause voltage surges from the controller. Voltage surges will destroy any 12 volt devices connected to the battery that are sensitive to surges.

With the alternator charging, if the bms activates nothing happens, the 12 volt start battery will still be connected to the alternator and handle the output.

The only solar controller that I have seen that has protection for bms activation is the makeskyblue 50 and 60 amp mppt. One of its features it claims to prevent voltage surges from a bms activation. I wouldnt use a controller unless I knew how it would react if the bms activates. Some controller manuals are vague on the subject. The 2 controllers I have used previously mppt and pwm both produce voltage surges. I eventually bought the makeskyblue 60amp mppt (130 dollars) and its what I use.

If you plan to use your current controller you can also connect a 12 volt lead acid battery in parallel with the lithium, so the controller can have somewhere to send the output if the bms activates. Also you can connect all your 12 volt devices to 12 volt voltage stabilizers to protect from surges.
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Old 06-08-2021, 10:40 PM   #5
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Quote:
Originally Posted by jonyjoe101 View Post
with lithium and solar, you need a controller that can handle a situation where the bms activates. A bms activation whether from out of balance, over temp will cause voltage surges from the controller. Voltage surges will destroy any 12 volt devices connected to the battery that are sensitive to surges.

With the alternator charging, if the bms activates nothing happens, the 12 volt start battery will still be connected to the alternator and handle the output.

The only solar controller that I have seen that has protection for bms activation is the makeskyblue 50 and 60 amp mppt. One of its features it claims to prevent voltage surges from a bms activation. I wouldnt use a controller unless I knew how it would react if the bms activates. Some controller manuals are vague on the subject. The 2 controllers I have used previously mppt and pwm both produce voltage surges. I eventually bought the makeskyblue 60amp mppt (130 dollars) and its what I use.

If you plan to use your current controller you can also connect a 12 volt lead acid battery in parallel with the lithium, so the controller can have somewhere to send the output if the bms activates. Also you can connect all your 12 volt devices to 12 volt voltage stabilizers to protect from surges.
You seem to have the problem very well defined although there are still some questions.

What does a solar controller does when the BMS activates and the solar panels are still connected. I assumed this was a no-no.

It would seem like a solar controller should not be managing a load if it can't deal with load dump.
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Old 06-09-2021, 07:07 PM   #6
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When the bms activates it leaks voltage, while the bms wont allow amps to flow to the battery, the battery will still read about 11.7 volts. The controller will see a battery that is connected and is low, and will try to forcibly charge it, but since the battery won't take amps, the controller will cycle back an forth and I have seen voltages as high as 20 volts.

The bms leaks voltage because it uses electronic relays (mosfets) to stop the charge, if they used mechanical relays there would be no leakage.

If you completely disconnected the battery from controller still connected to panel (mechanical relays), the controller just cycle back and forth but wouldnt damage anything.

I lost 4 to 5x 12 volt fans and numerous 12 volt pumps from my swampcooler due to the voltage surges before I finally fix the problem. Even if you set the bulk voltage on your controller low enough to prevent the bms to activate, every once in a while it activates.
This isnt an isolated incident, I read about other people having the same problem. But this only happens with solar controllers and lithium. Thats why its important to know how a controller will behave if the bms activates. I read the features on many solar controllers and makeskyblue is the only one that even mentions the problem, its the only reason I bought it, even though the 60 amp mppt controller is overpowered for my modest 365 watt panel, it does the job.
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Old 06-09-2021, 07:15 PM   #7
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This sounds more like a BMS issue than a controller issue.

-greg
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Old 06-09-2021, 07:40 PM   #8
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This seems like a pretty fundamental problem one way or another.

It seems like if there was a 10k resistor to act as a pull-down resistor that voltage would drop way below 11.9v. Donít solar controllers have battery disconnect voltages? You would need to be below that. You would have milliamperes of constant load but nothing you would notice.

Also, I recall the Renogy dc-dc charger has a ď lithium activation ď mode.

Quote:
The DC-DC have reactivation feature to awaken a sleeping lithium battery. The protection circuit of Lithium batteries will typically turn the battery off and make it unusable if over-discharged. This can happen when storing a Lithium pack in a discharged state for any length of time as self-discharge would gradually deplete the remaining charge. Without the wake-up feature to reactivate and recharge batteries, these batteries would become unserviceable and the packs would be discarded. A small charge current will be applied to the
house battery to activate the protection circuit and if a correct cell voltage can be reached, it starts a normal charge
I could see this causing some overvoltage if they are not careful about it.
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LithiumActivation.jpg   Renogy_ElectricalFault.png  
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Old 06-09-2021, 08:02 PM   #9
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Reading that Electronic Protection table, it says to remove all other loads and expect that the Renogy DC to DC will pulse the battery to activate it.

It sounds like a situation where the batteries went flat and the BMS disconnected. This would only happen without any charging.

To "activate the lithium" disconnect all other loads I assume this probably means disconnect the solar controller as well) then let the Renogy do the dirty work. The Lead-Acid have to be removed and use an alternate charger if below 8V.

This does not cover a charging situation where the BMS disconnects due to overcharging. Does the DC to DC turn around from a disconnected overcharged charged battery and try and activate it with BMS?

This is a good reason to have an active balancer.

I attached the Rich Solar controller table. There is a whole bunch of things going on as you get to the low voltage before a (I assume temporary ) disconnect at 10.6V.
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Old 06-09-2021, 08:21 PM   #10
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Originally Posted by Scalf77 View Post
This sounds more like a BMS issue than a controller issue.

-greg
Based on that Rich Solar table, I have to agree.

Having a disconnect at 10.6V then a BMS should not present 11.1V when disconnected. The interaction will just cycle. Sounds more and more like uncoordinated voltage limits.
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