Automatic 80% soc cutoff charger?

[Squilt]

I have a 13s 3p 18650 pack I made. To prolong the cycle life, I've been trying to keep amps relatively low, not discharge below 3.2v, and avoid charging over 80% soc. I got tired of trying to guess when it gets there and checking, sometimes forgetting it and having it charge to full. I tried searching online for one that lets you set the soc cutoff to whatever, but I had no luck. Does this exist anywhere I haven't looked? Would it be practical or safe to try to diy this?

 

[Comrade]

I have a "smart" WiFi outlet that the battery charger is plugged into. A micro-controller monitors the voltage on the battery and then tells the outlet when to turn off.

The outlet also has energy monitoring too, so I can see how much energy the battery took.

 

[sitzme]

You can measure your charge rate by the voltage rise per hour and use a spring wound or electronic timer with an outlet. Not exact but I found it to be a cheap and effective solution.

 

[E-HP]

I have a 13s 3p 18650 pack I made. To prolong the cycle life, I've been trying to keep amps relatively low, not discharge below 3.2v, and avoid charging over 80% soc.

The ending voltage for many chargers can be adjusted via a potentiometer on the circuit board. I have a faster charger that I set to ~90%, and a smaller one that I can use to charge to 100% and balance once in a while.

 

[offGridDownUnder]

Does this do what you want?

Satiator - Grin Products - Product Info

The Satiator is a fast and powerful universal battery charger that can be configured to charge a multitude of different battery types and voltages. It allows for partial charging to increase battery cycle life and has an OLED display screen to show realtime charging statistics. This is one of...

ebikes.ca

 

[Sturmey]

I have put diodes in series with charger output that seems to work although it does slow up the switching 'on' of the finish green light. You would probably need two in series.

 

[Squilt]

You can measure your charge rate by the voltage rise per hour and use a spring wound or electronic timer with an outlet. Not exact but I found it to be a cheap and effective solution.

Good idea, I'll try this. Won't work when I'm not home but I try to avoid charging it when I'm out anyway. Thanks

 

[Squilt]

Does this do what you want?

Satiator - Grin Products - Product Info

The Satiator is a fast and powerful universal battery charger that can be configured to charge a multitude of different battery types and voltages. It allows for partial charging to increase battery cycle life and has an OLED display screen to show realtime charging statistics. This is one of...

ebikes.ca

It sure does but for $325 I could build at least 2 more batteries

 

[fechter]

Many chargers have a voltage adjustment pot on the board inside. Lowering the voltage will limit the SOC and you won't have to babysit the pack during charging.
The diode trick works but the diodes will get pretty hot depending on the charger current and may need some kind of heat sink.

 

[TDA78]

LUNA CHARGER 48V ADVANCED 300W EBIKE CHARGER

I have a 600W version of this and cannot for the life of me find where to buy another

 

[E-HP]

Should start at the part where he's measuring the before voltage, before adjusting it; in this case up, but for your case you'd adjust down.

 

[eMark]

I have a 13s 3p 18650 pack I made. To prolong the cycle life, I've been trying to keep amps relatively low, not discharge below 3.2v, and avoid charging over 80% soc.

One way to figure 80% SOC based on your 3.2v cutoff (13s = 41.6v) is the difference between FULL = 54.6V and your CUT-OFF (13s x 3.2v = 41.6v). This is just one way ... others may figure 80% SOC another way.

FULL 13s Charge = 54.6v - CUT-OFF 13s Voltage = 41.6v (54.6v - 41.6v = 13v). 10% increments would be 13v ÷ 10 = 1.3v. The change in cycle life of a 90% SOC (53.30v) instead of only 80% SOC (52.00v) is insignificant (IMO). You'd be better-off (improved range) charging to at least 85% SOC.

• 95% SOC = 53.95V (54.60V - 0.65V = 53.95V)
  90% SOC = 53.30V (54.60V - 1.30V = 53.30V)
  85% SOC = 52.65V (54.60V - 1.95V = 52.65V)
  80% SOC = 52.00V (54.60V - 2.60V = 52.00V)

IMO, any increase in cycle life with only an 80% charge (52.00V) instead of [even] a 90% charge (53.30V) is insignificant; especially considering your moderate to low amperage discharge and no lower than 41.60V and probably most of the time not even that low.

The following adustable 60V 5A DC chargers (under $100) aren't considered "Professional" ... still should last you for many charges keeping charge rate on low side (1.5-2.0 amps) ... 60V dc adjusrable power supplies - Google Search

 

[electric_nz]

The Meanwell adjustable LED power supplies can be adjusted down so the current drops to zero at a set voltage. I have mine at 57.4V for a 14s battery (4.1V per cell) and it cuts off nicely/

 

[Squilt]

I'll go with setting a timer based on some quick math. Got me within 1% of my desired soc when I tried it earlier today. Not going with changing the pot because I don't feel like opening the charger whenever I want a full charge, even if that's infrequent. If I find myself needing to charge a lot while I'm away I'll likely get the Luna charger TDA78 suggested. That's pretty much exactly what I was initially looking for.

 

[gobi]

Here is my solution

Riden rd6018
and a meanwell 48v PS
$76 + $40

You are over thinking the charging, I set mine to 4v per cell and forget about it, with the wire voltage drop you will probably be around 3.9x V

Riden has great features, auto shut off, wireless monitoring etc.

 

[batteryGOLD]

I have a 13s 3p 18650 pack I made. To prolong the cycle life, I've been trying to keep amps relatively low, not discharge below 3.2v, and avoid charging over 80% soc. I got tired of trying to guess when it gets there and checking, sometimes forgetting it and having it charge to full. I tried searching online for one that lets you set the soc cutoff to whatever, but I had no luck. Does this exist anywhere I haven't looked? Would it be practical or safe to try to diy this?

U dont have a smart BT BMS to set top cut voltage at 4,0V per cell??
if not U could just add some diodes to positive line of your normal charger to reduce voltage..
U have a 13S battery means 54,6V top charge 100% and U need 80% 4,0V per cell charge. this means top charge at 52V
soo doin some math (54,6-52)/0,7V equals 4diodes in series with positive to limit 80% using a regular 54,6V charger.. just sayin. you need to test this dirty low cost method to know if it needs more diodes and too see if it works fine..