EM3 ev / Cellman Charger with 3 voltage switch.

dogman dan

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May 17, 2008
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Las Cruces New Mexico USA
I'm not going to lie or fudge about this, I was sent this charger freebie. Being jobless, I asked about a discount, and told Paul who I was on ES. He decided to sent me the charger completely free, and I promised to review it on ES.

Backstory. I have been a big fan of pingbattery for many years, but used RC lipo for higher power applications. Racing, Dirt riding, 40 amps stuff. Not daily riding, so charging with RC chargers was fine with me. But last year I put a large 5304 motor on my longtail cargo bike. And I put a 48v 40 amps controller on it. My pingbattery died of old age over the winter, and I used the last of my cash after I quit working to buy 48v 15 ah of new lipo. Using this big cargo bike now for daily transportation to grocery stores, I began to like the idea of bulk charging the RC lipo more. I also liked the idea of trying to do some touring with the longtail. I adjusted the voltage of my old 5 amps ping charger to 4.15v per cell of my lipo pack, and began to think a second charger would be really nice if I did need to charge a larger pack out on the road.

I needed another 48v charger. The idea of doing any business with bms battery had just about zero appeal. Then I read about EM3 ev's lithium chargers. They are pretty similar to the kingpan charger, with 5 amps of power, and a sturdy looking metal heat sink case. But what really turned me on, was the three way switch on the charger. At a flip of the switch, you get to choose between a 50% storage charge, a 90% lifespan extending charge, or a 100% charge when maximum range and voltage is desired.

I asked Paul to set my charger to match 14s lico. So the max charge is 58.8v for 4.2 volts per cell. The 90% setting is 57.4v for 4.1v per cell, and the storage charge setting is 53.2v.

Here is what it looks like. About 7" x 3.75"x 2" LTX appears to be the brand name. 48v 5 amps charger.EM3 ev charger.jpg

It has the usual two led lights. and as you can see it says clearly what they mean on the box. It has the CE certification, so nothing is risky homebuilt here. On the end of the charger is a recessed switch that selects either 110v AC or 220 v. I use andersons, so I was pleasantly surprised to see mine came with andersons on the discharge plug.

Here it is charging my 48v 10 ah pack, as it reaches top of 90% charge, with a wattmeter in line with the discharge cord.Three way switch bulk charger.jpg

Here is a close up of the wattmeter, as it tapers off the charge as the pack reaches 57.4v. When first attached to the battery, it definitely puts out the full 5 amps, more than 250w of charging power. But it nicely tapers off the charge to eventual zero as the pack reaches 57.4v. So far, no tendency whatsoever to overcharge the pack. I feel safe charging RC lipo with this charger, provided I have made sure there are no defective or user damaged cells in the pack.Top of 90% charge.jpg

Note that the wattmeter says 57.44v . Isn't that charger overcharging by .04v? No it isn't. Frankly, I'm quite amazed the cheap wattmeter in the pic measures even close to .05 v accuracy. Checking with a real DVM, I found that the charger was set precisely to the specified voltages.

Of course, I had to open the thing up immediately and look inside. I wanted to see if anything in there looked unable to take the shocks of riding around in a pannier bag on the bike. I've had bad experiences with funky daughter boards in cheap chargers. A few bumps, and the daughter board is shorting on the main board. Inside this charger there is a daughter board with some pots on it that look like they might be for adjusting the three voltage choices, but it's very firmly attached, and nothing else inside looks vulnerable to road vibrations.

I'm willing to say this charger can handle being carried around some.

I have been using this charger now for about two weeks, and I couldn't be happier, even if I had paid for it. Getting it free has no effect on my rating of it. It's a solid product, and Bulk chargers of Lico will love it for the three voltage settings. So convenient to just flip a switch when I want a 100% charge.

But if you have a pingbattery, a Sunthing lifepo4, or something like that, this charger can still be ideal. At a flip of a switch, you can have a higher voltage for kicking on the balancing functions of the bms, or a 90% charge that should extend the lifespan of the battery when you don't need to balance the pack.
 
MSRP? Any custom voltage options? How long did it take to reach you from ship date?

Thanks
 
how can it limit the cell voltage to 4.2V if it is a bulk charger? if one cell goes dead and shorts out to zero volts then how much will it overcharge them? i know you can assume that the cells are equal in voltage since the spread is always around 15mV, but if it is not the case how does it stop from overcharging?

if just one cell shorts out then the average voltage is 4.53V/cell, and you can assume that half are above and half below that voltage even if they usually have only a 15mv spread. jmho.

i still think it is safest to use a BMS to protect them. the idea that you can bulk charge sometimes and then use a balance charger occasionally would not pass a professional engineers test of the risk analysis. risk analysis doesn't work like that where you can assume stuff will not happen. you have to design safety in at each and every point. just like with an airplane or car or a manufacturing process. bulk charging lipo without a BMS is a risk imo.
 
If you don't understand the risks of bulk charging lithium cobalt RC batteries,,,,,, DON'T DO IT.

As pointed out above, the charger shuts off reliably at 58.8v. But if you have one bad cell in that big pile of cells, some will get overcharged and others undercharged. That's a big reason the switch is so nice to have. Charging to 57.4v gives you .1v of leeway, in addition to potential longer lifespan.

End of discussion, If you want to bulk charge, this is a decent tool for it IMO, with some handy voltage selections built in.

If you want to discuss the hazards of bulk charging, do it on a thread created for that.
 
Thats definitely cooler than the BMSBattery bulk chargers. I will have to check one of these things out soon.

I have 2 chargers that are basically setup like this already, one with about 10% higher voltage than the other one.
 
I have two of these for my cellman 14s9p LIMNC triangle pack. One at home and one at work. Cellman was nice enough to send me the 6A versions too. Does everything its supposed to do, has a cooling fan, LEDs and is well designed.
 
I should have mentioned the fan in the review. It's definitely keeping it's cool, between the heat sinking metal and the fan blowing.
 
i like this charger. Lets say you had new lipo packs and ditched the weak ones...would you charge to 90% on your packs everytime in between balance charges? I think I remember you saying every 25th cycle, you balance charge. Any recommendations for a balance charger for 18s3p (9 6s5000mAh lipo bricks)?
 
I have 2 of this chargers.

One for the 14s triangle pack and one for the wifes bike.

The switch is great. Like them and cheap to.
 
is this a Modiary charger?

it has no balancing current at final voltage so it will not balance a pack under a BMS so you have to use a balancing charger to balance the lipo packs.

if you do not want to have your pack sit at full charge for long periods you can just wait until it is needed and then charge it up to full charge just before use.
 
Can anyone crack one open and take some pics?
 
Would it balance a pack under a BMS if the voltage was set high enough in the 100% mode?

Could I use it with lifepo4 + BMS? I have a bit over sized pack for the daily commute and I like the idea of lifespan extending.

If I am right using it in the second mode after a while I would have some 100% charged cells and some low voltage cells!? If that's the case than I would need a more sophisticated BMS too... :(
 
The recent questions are way beyond my level of expertise. But I will assume they work with a bms since Paul sells them with bms equipped packs.

100% charge would be needed for bms balancing IMO.

How often to balance? As often as it makes you feel better. Nowdays, a year later into using this charger, I may go months without needing to balance my naked, no bms RC battery. I check about every 10 cycles for keeping the balance, but checked much more often when the packs were new. I now know and trust my cells pretty good, and I rarely discharge them very deep. Once they get old, it will be balance every use though.
 
cal3thousand said:
Can anyone crack one open and take some pics?

It would be nice to see the inside, I can say that in emails with Paul he told me that these chargers are not made by the same company that makes the "High Power" chargers both sold by Justin at Grin and supplied with Bionx bikes, even though they look fairly similar on the outside.

BTW, there he goes again, dispensing wisdom in language so clear and understated you didn't even know you just went to school... Dogman strikes again!
 
i have already worked on two of them. they both failed when the thermal fuse burned open circuit and the charger was dead. i tried to help AW fix his that also failed.

they have an nchannel mosfet on the back end that turns off at the end of charge and stops the charging. you can break off the mosfet at the legs by bending it back and forth, and then solder a jumper wire from the source to drain leg stump through holes.

you will see the mosfet under the last heat sink clamp. it is the outer one and can be accessed by removing then end plate. the three terminal voltage regulator is the other IC next to it. do not remove the insulator from behind the voltage regulator, and clamp it back when you remove the mosfet and short the source drain legs.
 
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