So, my 84V3A output "lithium charger" from eBay reads 97V on the multimeter...

bakaneko

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So, I got this 84V3A output lithium charger from eBay and when I went to check the voltage it read 97V. Is this normal? Does it go down to 84V after it detects the battery? I am kinda scare to plug this into my 72V lithium battery pack now...

https://www.ebay.com/itm/84V-3A-Li-ion-lithium-Battery-Charger-for-scooter-ebike-lifepo4/183510256973?hash=item2aba104d4d:g:6fUAAOSw3LVb17zv
 
How many cells in series does your battery have? I'm guessing it's a 20s pack, and if so, you're right to be hesitant, because that charger is set way too high. Lithium chargers will commonly measure at the cutoff voltage when no battery load is present. 97V is a very conservative cutoff for a 24s pack and slightly high for a 23s pack. 97V is kind of an odd cutoff number, are you sure it's not a lead acid battery charger for a 7x12V pack (which would be an 84V pack. If the pack is LiFePo4, then the numbers are different. I'm referring to lithium cells with a 4.2V max per cell fresh off the charger, and a 24s pack.

Aluminum cased chargers are typically quite easy to tune the cutoff voltage using a tiny flathead screwdriver and adjusting the trimpot (adjustable resistor) closest to the charge output wire. Taking the cover off is usually just take off the top 2 screws on each endplate and pop the top off, so a 5 minute job to get the cutoff voltage you want. I adjust every charger I get, because I like to charge to only 4.10V or 4.15V per cell cutoff voltage.

Even after tuning personally oversee the first time you use it to make sure it cuts off at the voltage you want. Just to be safe in the event of a charger failure, I always use a timer on the AC supply to my charger as an extra safety precaution. I'm very familiar with my packs and charge times, so I can estimate charge times pretty well.
 
Chargers are usually labelled for the pack voltage they are intended to be used for, not their maximum output.

So...97v output is about right for a 23s lithum battery's full charge. 84v is about right for it's median voltage. But this one's ad is marked as a LiFePO4 charger, which would be about a 27s-ish pack for the 97v, though median voltage on that would be around 86v.

If yours is a 72v median (nominal) voltage pack, of 20s lithium (non-LiFePO4), then you need a "72v" charger. That will generally have a full charge voltage of around 84v, so I can understand your confusion.
 
Thanks guys. Now that I looked at the listing a bit closer. I misread it. It is for a 84V battery... But, then there are listings that say 72V and 84V output on the charger. I will get one that says 72V output on the charger now... Thx again
 
bakaneko said:
But, then there are listings that say 72V and 84V output on the charger.
That would be because they are for a 72v pack, which requires an 84v output to actually charge it fully, as I noted in my first reply above.
 
amberwolf said:
bakaneko said:
But, then there are listings that say 72V and 84V output on the charger.
That would be because they are for a 72v pack, which requires an 84v output to actually charge it fully, as I noted in my first reply above.

Yes, but then the 84V charger also saids 84V3A output on the label... Maybe, I am just confusing myself or China and America have different labeling and that confused me. This should be simple LOL... :roll:
 
bakaneko said:
Yes, but then the 84V charger also saids 84V3A output on the label... Maybe, I am just confusing myself or China and America have different labeling and that confused me.

Fair point. If they don't label things correctly you can't know what something *really* is. :/



Personally, I'd rather use something else than the cheap chargers like these things (of which I have a box of dead ones of varying types and ages).

The two best chargers I've had so far are the Cycle Satiator from http://ebikes.ca and the Meanwell LED PSUs (HLG-600H-54A in my case). But they're not exactly cheap, and I woudln't have mine if it werent' for generous members here.

Both are sealed and vibration/weather resistant, and can be mounted directly to the bike/scooter/vehicle/etc. My SB Cruiser has a MW attached to teh bottom fo the cargo / seat box as onboard traction pack charger.

The CS HV version should work on your pack (can't remember it's highest voltage though), and can be used on other packs too, you just make the presets you need and load them up via USB (or do it via the front panel display/buttons).

The MW is adjsutable voltage and current (with the A versions), and come in a variety of sizes and voltages. There are mroe than a few threads here about them wih more details, but you can series them for more voltage, and parallel them for more current.
 
Okay, I will look into that Mean Well when I am ready for an adjustable charger to go on the bike. I took a look and the only ones I could find were from Alibaba Express and hence overseas. Eventually, I would like to have a 72V adjustable charger that can go from 3-10A. Its gonna be pricey I am sure but would complete the idea for my build.
 
bakaneko said:
Okay, I will look into that Mean Well when I am ready for an adjustable charger to go on the bike. I took a look and the only ones I could find were from Alibaba Express and hence overseas.
FWIW, all those cheap chargers you're looking at now are probably "overseas".

You might want to look at Mouser, Digikey, Farnell, and other similar electronics distributor companies.

And remember, you're not just looking for Mean Well; almost all of what you will find on sites like Alibaba/etc will be "clones", which may or may not even operate the same way as the actual units, and aren't likely to be the same quality level. Some of them are actually junk in a box with a cord on it, based on some of the threads of people trying to use them as chargers.

What you are looking for is specifically and only Meanwell HLG series LED PSUs, in the "A" version.

Anything else may not be usable as a charger at all, or adjustable.
 
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