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90% Battery Charger

Posted: Mar 24 2020 2:15pm
by MartynB85
Hi

I’m based in the UK and I’m looking for a charger for my 52v pack. I’d like a charger I can set to charge the pack to 80-90% rather than all the way to 100.

Is there anything out there other than the Cycle Satiator?

Thanks

Re: 90% Battery Charger

Posted: Mar 24 2020 2:23pm
by JackFlorey
MartynB85 wrote:
Mar 24 2020 2:15pm
I’m based in the UK and I’m looking for a charger for my 52v pack. I’d like a charger I can set to charge the pack to 80-90% rather than all the way to 100.
You can do a cheap version of that by just charging to 4.1 volts per cell.

Re: 90% Battery Charger

Posted: Mar 24 2020 3:54pm
by MartynB85
That’ll do! How do i do that?
Thanks

Re: 90% Battery Charger

Posted: Mar 24 2020 4:15pm
by Balmorhea
MartynB85 wrote:
Mar 24 2020 3:54pm
That’ll do! How do i do that?
You can use a series of power diodes whose forward voltages add up to however much voltage you want to drop. You will need enough heat sinking to dissipate however many watts that is at the charger’s maximum current.

Re: 90% Battery Charger

Posted: Mar 24 2020 10:50pm
by jonyjoe303
depending on what your input voltage is? also what amps you want to charge at?

You can get either get a
a. 30a buck (step down voltage) input 20-70 volts / output 2 - 58 volts about 40 dollars
b. 30a boost (step up voltage) input 10-60 volts / output 12-90 volts about 20 dollars

They sell dc-dc converters that are cheaper and handle less amps, you just got to make sure they handle the range that you want to charge at.

You can find these on ebay, the high amp models have large heatsinks but they will need a fan at higher amps. You can adjust the output voltage and also the output current. These work great as CC/CV chargers, the closer they get to the voltage you want they reduce the amps. I use these to charge my lithium battery's, once you setup the output voltage, they are plug and play.

picture of 30a boost converter
30a boost converter.jpg
30a boost converter.jpg (111.84 KiB) Viewed 363 times
Picture of some of the smaller 6 amp buck converters I used, you can add a 5 dollar led volt/amp meter (meter available in 10a and 50a) and you can better monitor how close the battery is to fully charged. You can build a decent cc/cv charger without spending too much money. I no longer use my balance charger, I just use these converters, I get a very good charge on my batteries, no more programming the balance charger everytime I want to use it.
buck converter 300 watt.jpg
buck converter 300 watt.jpg (104.02 KiB) Viewed 363 times

Re: 90% Battery Charger

Posted: Mar 25 2020 12:14am
by amberwolf
if your charger is not adjustable, you can get a meanwell hlg-xxx-54a led psu, where the xxx is the wattage. i use the hlg-600-54a for 12amp charging of a 14s 40ah pack.

if your charger is only a 2a charger, you can use the hlg-100-54a for about 1.7a, or the hlg-150-54a for about 2.8a max (can adjust downward from there to match the 2a charge if you need to).

the catch with these is there isn't a "switch" for percentage of charge, but just an adjustment pot for voltage, and another for current. so you would need to readjust the voltage pot every time you want to charge to a different percentage of full. if you always just charge to 90%, then you'd put your voltmeter on the psu's output (without battery attached), turn on the psu, and adjsut the voltage pot until it reads a voltage equal to 0.9 x 58.8v, which is 52.92, or 53v. (or if you prefer 4.1v/cell, then use a voltage of 57.4v).

then plug in the battery to the psu's output, and it will begin charging up to that voltage. it will not, however, "shut off" when done like a charger, so you will have to disconnect it when it's done. it wont' continue "charging" (because the voltages are equal at that point) but the voltage will still be present on the output until you disconnect the psu and turn it off.

Re: 90% Battery Charger

Posted: Mar 25 2020 10:14am
by 999zip999
What size is your battery ?

Re: 90% Battery Charger

Posted: Mar 26 2020 2:11pm
by electric_nz
Luna 52V charger has 80-90-100% charge setting and 3/4/5 Amp charge. I've used one for years

Re: 90% Battery Charger

Posted: Mar 26 2020 6:29pm
by dustNbone
For a 52V (14S) battery, using a 54.6V (48V) charger will give you about 3.9V per cell, which is probably somewhere in the 80-85% range.

Re: 90% Battery Charger

Posted: Mar 26 2020 6:57pm
by john61ct
We're ASSuming the pack is a LI chemistry @14S where each cell is 3.6-3.7V

are we?

OP, please verify that is the case before proceeding.

Re: 90% Battery Charger

Posted: Mar 26 2020 9:07pm
by John in CR
Just buy a common battery charger (the type with an aluminum housing) for your pack. Remove the top which snaps into place with the 2 top screws on each end plate holding it in place and adjust the potentiometer that controls the voltage cutoff to the voltage you want. There are plenty of youtube videos showing how to do this, but typically it is the pot nearest the charge output wires. You'll need a tiny flat head screwdriver, a phillips to remove the cover, and a multimeter to see the max voltage. Be careful not to electrocute yourself in the process, and it's good to insulate all but the tip of the flat head with electrical tape to reduce that risk, as well as reduce the risk of shorting something and damaging your charger. It's a quite simple process that I've done many times, and that's coming from a caveman when it comes to electronics.

If your charger runs pretty warm and you aren't concerned about fastest charging and you have an ammeter to measure DC current, then it's a good idea to turn down the charge current while you're in there. Heat in the copper goes up by the square of current, so reducing the charge current a bit will pay big dividends in terms of heat loss and make your charger less prone to failure, a common cause of battery fires. With summer coming soon to the northern hemisphere, it's a good time to think about keeping your charger(s) cooler and happier. Note that you'll need a partially depleted battery pack, so you can measure charge current, since near the top of charge current tapers off while the charger is in the Constant Voltage part of the charge cycle.