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Victron 150/35, Outback
#21
(09-25-2019, 02:27 AM)Doin it Wrote: Would this charge controller do well for charging lithium.. it says it has bulk, absorption and float..
Which of those modes are needed for charging lithium.. I believe I’m supposed to set float voltage just under absorption for lithium.. for some reason tho I thought float wasn’t needed for lithium.. or one of the charging modes weren’t needed for lithium? lifepo gets charged differently I guess but I’m not getting lifepo
Were these the older versions of the midnites?

I use an Outback FM60 to charge my batteries - It was what we installed when we added solar to our original battery inverter system that was already Outback.
Robin Gudgel sold outback and after a few years rest he started Midnite solar and designed the classic MPPT.

If you want to charge lithium you really should have an MPPT controller that is controllable by your BMS - this means Schneider or Victron only if you use Batrium.
You need to be able to command a reduced charge current when you are nearing the end of the CV phase and you start bypassing/balancing.

Doing without this communication is a total pain in the arse - ask me how I know!
Aside from that, the MX/FM60 and FM80 charge controllers are robust and reliable.

You need to set your float voltage so you hold your batteries at their resting voltage when not subjected to load - so that your solar panels will carry your house loads when the sun is blazing down and your batteries are full by 11am Smile

I have my float set so my LiFePo4 cells sit at 3.35v/cell
Current system: 9.6kWh wet Nicad batteries, 16S1P Calb LiFePo4 210aH, Batrium WM4, Outback vfx3048 inverter, mx60 mppt controller, flexware 500 mounting hardware, 2.4kW solar array, 6kW lister diesel genset. MY'13 Vauxhall Ampera
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#22
Why does the charge controller need to be controlled by a bms.. I thought a bms keeps the cells equal. Wouldn’t the charge controllers float allow for the reduced charge
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#23
A BMS does not need to be controlled by the charge controller.

The charge function is responsible to push current to the battery bank and have enough smarts to avoid 'overcharge', but its at a total battery voltage level (not individual pack/cell level). The BMS can also see total battery voltage (and protect against overcharge) but is *also* responsible to see individual pack/cell info. The BMS's role is to disconnect the battery from the entire system (including the charging function) if it detects a critical event (over/under, bad cell, temp, etc).

In my case, I have multiple charging sources... and none are controlled by Batrium (BMS).
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#24
(09-25-2019, 04:11 PM)Doin it Wrote: Why does the charge controller need to be controlled by a bms.. I thought a bms keeps the cells equal. Wouldn’t the charge controllers float allow for the reduced charge


The charge controller has no idea what each individual cell group is doing... plus its not a CC/CV charge profile which is recommend for lithium.

As lithium cells get full, they switch from CC to CV, meaning that the charge current is reduced to maintain a constant voltage.

That said, I dont fully charge my batteries, and I dont charge at high current rates because my solar system isn't that large but my batter bank is.  In my system I have no concerns as I would never hit a stage where I would have switched to CV.  

I can completely understand why the other person is bringing up this concern.  This is going to vary from system to system and will change based on the design and capability of your setup.

If you have the option to allow the BMS and charging system to communicate, it is only going to increase saftey, but is also not required depending on the system.
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#25
Thx for quick responses.. Well I just looked at ppl here using batrium and I must say it’s above my skill lvl to set it up.. I was thinking of using like a 100$ bms thats easier to setup.. setting up the iotawatt was about as technologically advanced as I can handle..
I’m planning on charging my 16s battery pack to 64v, which isn’t full..
my charge current coming from charge controller is only 30 amps max..
So I’d be fine using the outback? It’s a good bit cheaper than a victron that can handle the same amps.. later I plan to add my other array for more amps but not any time soon.
Are the outback charging profiles adjustable enough for my size lithium?.. can i shut off equalization? I don’t need to worry about cc/cv charging profile if I’m not charging the 16s pack to full,,,? Setting float just under absorption voltage (which is below full) will work instead of having cc/cv charge profile?
Are they still making these outbacks? Are capacitors (or whatever) dried out from being made a while ago, or do they still make these outbacks today? Typically I see charge controllers with bulk, absorption, float and equalization, so for lithium I only use absorption and float?
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#26
I would tell you to just test it... all of this stuff changes depending on the setup. Its a DIY forum and you assume all responsibility for design / engineering / testing.

Even the cells you use could effect the end result. If you terminate at 4.0vdc per cells, watch the cell voltage until the point of charge termination. I have no idea of 30a is going to increase any of your cell voltages to a level that would create a problem. If it does you need to either back off charge current, increase the pack size, or lower the charge termination voltage.
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#27
I think what I want to ask has more to do with how some charge controllers say they are for lithium by using the settings.. I’d assume these aren’t cc/cv chargers but instead user would just use absorption and float? Is this ok to do or do I need a specific charger for lithium. so with this controller in the pic I would just set the absorption voltage and float voltage and that how it would be used for lithium? Can’t the current-amps be set in a charge controllers settings to get constant current for the absorption stage? I just dont want to buy the outback if it’s not going to work for a low mileage 3kw 50ah lithium battery pack.. I suppose the outbacks charging voltages can be set. But I don’t think it has a constant voltage charge mode.
Yeah crimp Ik I assume all responsibility and all that.. just picking some more experienced brains on the situation.. u said it’s not necessary for u to worry about the charge controller switching to constant voltage cuz u do not charge your batteries to full charge.. what info do u need to know from me to see if I can do the same?
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#28
By any chance, have you ever worked with an RC / balance charger?  Those always charge lithium in CC/CV and really helps you understand that charging profile better.  Just to get a better general understanding of how things work in an ideal setup for lithium.

I think it’s safe to assume most solar charge controller don’t have a formal CC/CV profile.  They only look at top end termination voltage.  The software internally may also vary in that some may simply shut off when the voltage is achieved, some may slowly ramp down as it gets closer to full.  Remember the batteries internal resistance / ability to take a charge will also change how this acts.

I don’t use anything other than Genasun and Victron so I can’t comment on what other brands do.  I would just buy, test, and observe.

My Victron is setup with a 100% custom profile.  I only concern myself with setting my absorption voltage, and disable any lead specific settings like temp compensation and equalization.

I also balance and maintenance charge if required using a RC balance charger.  I don’t run a BMS either as my cells are also pretty well matched.  My battery bank is made of high drain EV cells… I can stay in CC until its finished because and never really worried about needing to hit CV because 1) I don’t charge till full, and 2) can’t throw enough current at my bank for it to even matter.
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#29
No I’ve never worked with anything other than a car battery or trolling motor battery.. So u don’t use float at all? Wouldn’t a bms let u know if u have a cell going bad? The pic is a similar battery pack to the one I’ll be installing
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#30
I highly doubt you will have problem charging at 30A and terminating before full with a battery like that. EV cells are generally so low resistance that they would soak up a 30A charge rate without blinking an eye.

Floating voltage is a maintenance voltage for lead acid. You don't need/want to float lithium batteries as they dont drop voltage like lead when you remove a charge (not on a healthy cell at least) You can probably set float to the same voltage as absorption or even a little lower if you prefer.
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