Still looking for the right charger

[jak]

Well, here's a homemade charger you could build for about $25-30 if you can scrounge a few bits:

DC to DC boost regulator CC/CV (18-35$)
old PC power supply (0-25$)
4.7 ohm 10w resistor (2-5$)
14 guage wire
plug for charge port (rca fits most batteries)


This is about as simple as you can get. Old PC power supplies are basically free, 250-350w is adequate... anything that is rated 20 amps at 12v. The 10w resister is for the 5v rail (expect it to get warm/hot = normal). 12v out goes to DC-DC regulator input. I suggest a boost regulator with a numeric display, 10a+ rated, and output up to ~90v so you can charge any battery. (search the bay for "converter step-up 90v" and look for one with a display). Reg output wire should be long enough to conveniently reach the bike.


I added xt90 plugs to match my bike power leads so I can swap in my watt meter to see how much it takes to charge up the battery or an adaptor for my 12v motorcycle battery. I repurposed an ancient ide disk drive tower for a case... you could certainly make something prettier. 10a@12v gives me a little over [email protected] (~85% for my 48v battery). It basically stops charging when it reaches the set voltage, but may overshoot a small amount if you leave it for days. Voltage matches the meter pretty closely.

 

[Gionnirocket]

Jak... You're a mad scientist my friend!

It works but I think my Frankenstein is more elegant. But I am partial to my own

 

[tomjasz]

 

[jak]

mad scientist indeed. however, I do use thicker wiring than any expected load, have an extra fan for cooling, I only charge it when I'm around to monitor it... and, I've been running PCs for decades 24/7 and never had a power supply failure that didn't just shut it down. YMMV, but I'm even LESS comfortable trusting the several 54.6v chinese chargers that came with the batteries. I'd definitely trade it for any GRIN product... but, it costs more than my bike, and I didn't build it, so where's the fun in that??? My desk is covered with laptops to repair, a UV-C germicidal lamp that I built, bits of stove displays and relays, some 18650 cells that I need to build a spot welder to assemble, a broken EVSE to fix for my Fiat 500e... do you want me to clean my desk?!?!?!? I was bored once... I vowed never again! It's stopped raining... I think I'll go ride my bike.

 

[Gionnirocket]

I hear you... A pc power supply is probably tested and built with better components compared to the cheap chargers that come with our batteries. I've worked closely with IT departments in my travels and have seen more than one power supply smoke... but never burn.
I understand your setup though it's beyond what I would feel comfortable building without guidance.

I rode this morning before the rain, It was nice and cool out... But take one when you can get one... Enjoy!

 

[MeDotOrg]

Since many people are buying a second charger because of the 80% limit and trickle charge, would it be cheaper to build a unit that ONLY charged to 80% at 1 amp? The vast majority of people still have their original chargers for the times they need to get to 100%. Perhaps a cheaper solution?

 

[6zfshdb]

I just use my OEM charger on an $8 timer. I've learned through experience how long to set the timer and almost always get the battery between 70 and 85%. I usually charge to 100% just before a ride so the BMS can balance the cell strings. I've been using this process for 3 years now on all five of my batteries with no noticeable loss of capacity.