Charge Controllers with Adjustable Low Voltage Cutoff

Hi,

Can anyone point me in the direction of a manufacturer of lithium solar charge controllers whose low voltage cutoff is user-configurable?

For some reason I can't find any that list this feature..


TIA!

yourtalking about overdischarge protection? The ecoworthy 20 ampmppt I use to charge my 4s 110ahlifepo4 goes as low as 10.2 volts.

jonyjoe505 said:

yourtalking about overdischarge protection? The ecoworthy 20 ampmppt I use to charge my 4s 110ahlifepo4 goes as low as 10.2 volts.

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Thanks for the suggestion

Actually, I wanted this feature to be able to set the overdischarge protection *high*. So that I could leave the load on to run while the sun is high, but I'd still have, say, 90-99% capacity for the night.

Most MPPT chargers have that function where you can program. Like PCM60x or am I missing something? (Though that is not pure lithium charger)

Victron SmartSolar MPPT controller look pretty awesome... many of them have a low voltage disconnect where you can set the cut-off voltage. If you need more amperage, you can always connect a relay to the load output and use it for control. The charge limit and voltages are also programmable. I don't own one of these yet, but I plan on buying one... Im just going off what I read and research.

https://www.victronenergy.com/solar-charge-controllers/smartsolar-mppt-75-10-75-15-100-15-100-20

Outback controllers also are programmable and can be controlled with web/phone app. Their systems are a little pricey though, though I haven't really looked at the PIP or others.

Alternately, there are other ways to make a LVD if the charge controller isn't the component that has control... a BMS can do it with something like a shunt trip, or even a Victron shunt with SOC or voltage monitoring to control a relay or contactor.

Just depends what you are trying to accomplish

jonyjoe505 said:

yourtalking about overdischarge protection? The ecoworthy 20 ampmppt I use to charge my 4s 110ahlifepo4 goes as low as 10.2 volts.

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After doing some research, I think I may buy this. But I'm a bit concerned that this charge controller doesn't explicitly support li-ion batteries.

This charge controller would be to charge a li-ion pack in my camper van. Long-term I'd like to build my own pack, but to get started I'm going to purchase this "TalentCell Rechargeable 12V/11000mAh", which uses Panasonic NCR18650B cells in 3s3p.

* https://www.amazon.com/TalentCell-Rechargeable-11000mAh-14500mAh-26400mAh/dp/B016BJCRUO/

This pack has built-in BMS, so I'm not too concerned about damaging the cells, but I do want to make sure I set the charge controller to the right settings.

Would it be a good idea to buy this eco-worthy mppt charge controller for this pack?

I would probably set the over-charge disconnect to 12.5V-ish and the over-discharge disconnect to 12.4V-ish during the day & probably just above whatever the low is when the BMS cuts-off for night.

But how do I figure out what the settings should be for the absorb & float voltages?

My goodness for $64 you can build yourself a massive battery pack On top of that, these types of cells works poorly in 12v configurations.

That battery pack is so small that its usefulness is going to be pretty limited in terms of what I would envision wanting to use it for in a camper van. What exactly are you trying to accomplish in this project?

CrimpDaddy said:

My goodness for $64 you can build yourself a massive battery pack On top of that, these types of cells works poorly in 12v configurations.

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I have a boost/buck voltage regulator that I was going to use to stabilize to 12v.

CrimpDaddy said:

That battery pack is so small that its usefulness is going to be pretty limited in terms of what I would envision wanting to use it for in a camper van. What exactly are you trying to accomplish in this project?

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I want to run the car's blower motor (cabin fans) for a few hours during the day and for 8 hours on a hot night. I think the blower motor will pull about 1 amp, and I expect the battery to get me 8 AH.

I was going to build the pack, but our local computer recycling shop (that used to sell dead 12-volt laptop packs for $5 each) suddenly stopped selling cheap/dead battery packs unless you buy them by the pallet. I wanted to get ~60 good ~2000 mAh cells.

What do you think I could build for myself for $64? I don't even own a soldering iron yet

You dont need a soldering iron. Just duct tape all the wires on to the cells and wire nuts for all your connections. It'll work juuust fine. Go full MacGyver!

no, don't, jk

Start with the iron, learn to use the iron before taking on bigger tasks like this. There are parts of the project where good soldering is needed so you don't short anything out and make a bigger mess in the end.

A blower motor I think will pull more than 1A. 3p would probably handle the current, but it won't last 8Ah. 3p would mean each cell would have to be minimum 2600mAh. And from use laptop cells, that's gonna be hard to come by. Now, if you went with 8-10p, that'd be great and you could have 1800mAh cells and you'd be safe.
Also, it would be better go with 7s instead of 3/4s and use a buck converter to get your 12V output. The LM2596S Buck Converter variants you can get off eBay would do the trick fairly nicely. There are 3 variants, and they distinguished by how many Trim Pots are on the board. 1 pot can only adjust output voltage. 3 pots can set output voltage and max current. I don't remember what the 2 pot (and the 3rd one on the 3 pot variant) is used for. But the are rated at 3A output. So you could run the motor fan off that. You might need 2 in parallel or one that can do 5A as the blower will draw 5A or more on start up. A way to get around that is to pre-spin the fan before turning it on. That lowers the current draw drastically. But you'd need to remember to do that (and be able to have access to it).

yes, find the fuse for the blower motor and you will see how much current it will draw.

Korishan said:

A blower motor I think will pull more than 1A. 3p would probably handle the current, but it won't last 8Ah. ...
A way to get around that is to pre-spin the fan before turning it on. That lowers the current draw drastically. But you'd need to remember to do that (and be able to have access to it).

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I'm very proud to have 10 fingers, and that motor scares the hell out of me D:

rtgunner said:

yes, find the fuse for the blower motor and you will see how much current it will draw.

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So the motor pulls a steady 2.2A on low. 5.8A on medium. 10.8A on high. It _will_ spin at ~1A, which is just a gentle drift of air (probably sufficient to get the humidity out during the day, which is my #1 priority).

Hahha, I didn't say turn it on while your hand is on it Give a quick spin and your hand is free from it then hit the switch. I do that on my house blower fan to pull outside cool air inside. I need to replace the start capacitor and just haven't gotten to it yet. To make it extra safe, the hand you use to spin the blower is the hand that triggers the switch


If it uses 2.2A on low, use that. Don't try to turn it on 1A. The reason is the motor needs air flow through the casing to keep the windings cool. If you turn it too slowly, there won't be enough air passing through it to keep it cool and you'll actually burn out the motor; even at low amps.
So do your calculations based on 2.5A (this helps to include some efficiency losses). If you use the above mentioned LM2596S Buck Converter that can output 3A, then you'd be almost on pitchers mound with the efficiency of that that board/chip. As long as the input voltage is >20V. Get lower than that and the efficiency starts to drop off pretty quickly.