Bmsbattery charger question

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cwah

100 MW
Joined
Jul 24, 2011
Messages
4,256
Location
Between paris and london
Hello there,

I have a charger from BMSBattery and I'm trying to adjust it. I know there are several thread about that but I couldn't find the information I'm looking for and I don't want to blow the charger.
BmsBattery_trim_pot.jpg


I've managed to find out that:
Trim pot A: Allows to change the voltage

But...
Trim pot B: What does that do?
Trim pot C: What does that do?

Basically, I'd like to lower the amps enough to limit the heat. Then reduce the fan noise by reducing the fan speed. So probably a resistor of X ohm.


Again, I know there are several thread about these charger but I couldn't find the info.

Thanks and I hope it's going to work well :)
 
you aren't really serious? this is a joke, right? you wanna reduce the fan speed because it makes noise? so you wanna reduce the charging current to nothing so it won't make heat and then allow you to reduce the fan speed? this has to be a joke.

this goes on the mary poppins bike? the sailbike?
 
Just amusing, at least to me. You could just buy a 2 amp charger that typically comes with no fan. Here in the US anyway, it would cost very little.

It's a little like buying a V8 engine, and wanting to run on 4 cylinders. Wouldn't a better solution be buy a 4 cylinder engine? It depends on how much you want to turn it all down of course. Maybe you aren't going that low. If the fan squeaks or something, you can easily find a replacement I'd think. Above 2 amps, I'd want that fan going full blast in my climate.
 
cwah said:
Why is it bad to reduce current and fan speed? :?:
Click to expand...
How long a time do you have to charge your battery between rides? The lower the current the longer it takes. The lower the fan speed the less air that moves thru the charger to cool it, so the hotter it runs even at lower currents.

I have a 3A charger here that is always as hot as if it was sitting in the sun, even when it is basically idle at only 1W charging power or less, after the fan has shut off after charging is essentially done. Even after it's been in that state for hours, it is still that hot, because it's just that inefficient or badly designed or whatever. I imagine if I actually used it for charging without a fan or at a very low speed, even at a very low current, it'd probably damage it from overheating.
 
I know it sound stupid, but my flatemates are getting crazy with my charger and they say they can't sleep :lol:

Now I'm thinking about buying silent fans. I'm hesitating between 2 choices:
- Get a fan of the size of the charger which is 40*40*10mm:
http://www.amazon.com/Scythe-Mini-Kaze-Silent-SY124010L/dp/B000LB0M8S/ref=pd_sim_pc_5

It would fit perfectly on my charger but as these are small fan, RPM have to be higher and it's going to be noisy.


- Get a bigger fan I'll put on top of my charger:
http://www.amazon.co.uk/Cooler-Master-Blade-Case-fan/dp/B0034AFDL4/ref=sr_1_1?s=computers&ie=UTF8&qid=1348923814&sr=1-1

Because it's bigger, it will be less noisy. However, I'll have to drill it on top of my charger and drill additional holes for air flow. Main issue is that dust will go inside easily and any water drop will be fatal...


What's the best?
 
ok, that makes more sense. small space, charger on all the time is going to annoy people. i hate listening to my refrigerator and the noise from the charger is like that too. i would turn off my single cell charger at night too because of the noise. it's annoying, so i get it now.

ping has a small 2A charger with a tiny fan and he used to sell a charger brick with no fan. i have a 12V power supply with no fan, just perforated case. that would work with a balancing charger like the 1420.

maybe you should consider putting the charger inside a sound absorbing box, with multiple partitions covered in sound absorbing foam but with vents that exit underneath so the noise that comes outa the box is directed down unto some carpet or pad.

you could put the charger inside the kitchen cabinets and run the charging leads out to where the battery is located or charge the battery inside the cabinet to trap the noise in there.

edit: to reduce the fan speed, look for the 100 ohm resistor that is line with the transistor that turns the fan on and off. you can add another resistor in series or swap that one for a higher value to reduce the speed. i plan to decrease the resistance on the chargers i hack up to higher currents so i can get more airflow, along with cutting out the grills that slow the airflow through the ends.
 
I have two 240W chargers from BMSBattery, a silver aluminum model purchased a couple of years ago, and a black aluminum case model purchased more recently. The fan noise from the newer unit is significantly louder than the older model and can be annoying. You could probably slow it down enough to quiet it w/o impacting the cooling all that much.

After today's ride I used each charger one at a time to recharge the battery. The case and the air exiting the newer model (EMC-240) felt cooler than the older model (EP6004JL). I also checked the efficiency of each by measuring the input ac power with a Kill-a-watt meter and the output power with a Turnigy in-line wattmeter. The results were the new model bested the old model 84.3% Vs 80.2%.



-R
 
If you want to reduce the noise, reduce the turbulence caused by blockage of the air path for the fan.

Primarily, that means removing all of the faceplate metal from inside the fan's blade circle, and removing any other fan guard it may have (probably none).

Enlarging the inlet air holes at the other end will also help.

Both may cause more dust buildup inside, but you can easily blow the dust out once a month or whenever using compressed air.

In the event of a gravity/liquid/container interaction event, liquid would get in anyway, thru any of the fan holes, so the worry about a different fan placement doesnt' really matter. You wouldn't want to be charging near where water could get into stuff that's plugged into the wall anyway.



BTW, remember that while it might be annoying to have the fan run for whatever period it runs for now as it charges, if you reduce the charging current it will have to run that much longer--if you reduce it enough to enable you to slow the fan down without overheating it, most likely it will have to run for several hours at a minimum, possibly all day or all night, to recharge. That might be even more annoying. ;)



Another option is to create a baffle tube. Get some cardboard boxes, and make a tube (square or rectangular, not round) about 3-4 feet long. Slit the tube in the middle of that for an area just large enough to stick teh charger into it and take it out, leaving the flap so you can "close" it. Run the cables out the corners of the flap with no space around the wires.

Staple or glue strips of cardboard across the width of the tube every few inches or less, in an alternating pattern, like little partitions or dams, so that they block about 2/3 of the tube's crosssection. Put the first one on the top of the tube, the next on the bottom, the next on the left side, the next on the right side, and so on. Thsi will help the sound be dampened by each succeeding baffle.

You can also put very dense foam (like a rubber floor mat) around the whole thing to absorb more sound.

The baffles will also restrict airflow a lot, so you may have to add another much larger diameter fan at the exhaust end of the tube, running at very slow speed, to help pull the hot air out of it (or the charger could overheat). Perhaps power this fan off the "charging" LED so that when it's done it will turn off, but if run slowly enough at large enough diameter, it should be so quiet as to be ignorable.
 
Thanks Dnmun and Amberwolf for this noise isolation idea. I'm definitely going to look for something to isolate the noise :))

I think you're all right, it doesn't make much sense to restrict the power in order to diminush the noise. Better work on the noise isolation.

I think I'm going to get one of these big 92mm fan:
http://www.amazon.co.uk/Nexus-92mm-Real-Silent-DF1209SL-3/dp/B001AZJJ9M/ref=sr_1_6?s=computers&ie=UTF8&qid=1348951140&sr=1-6

I'll drill holes on the top of my charger cover and see how noisy it is. These fans are supposed to be almost silent so it would be silent enough to not need a noise isolation box.

I'll still add a dust cover I think because with the fan on top, it will be much more dust prone!
 
no no, don't buy another fan yet, do like AW said.

since you don't run the charger continuously, you can get away with reducing the speed like you asked, but if you can cut open the grill and let the air flow smoothly and use some cardboard or even plastic foam tubes to direct the air flow, that will help a lot.

do consider putting the charger inside the cabinets or somewhere that the noise is less of a nuisance and extend your charging leads to where you park the bike. if you can remove the pack and put it in a cabinet or closet with the charger you will kill a lot of the noise right away.

plus, just give your roomies the option of turning it off when it is a problem for them, then maybe it will be less of a problem for you and you can turn it back on when they go out.
 
cwah said:
I'll drill holes on the top of my charger cover and see how noisy it is. These fans are supposed to be almost silent so it would be silent enough to not need a noise isolation box.
Click to expand...
Don't add any new holes unless you are going to use them for a new fan, or you will change where air comes from in the case and which components are cooled by it. Otherwise you must increase the exhaust airflow (faster/bigger/noisier fan) to make the same airflow happen at the original air inlets and keep that part of the charger cooled.

And if you do, make the hole as large as the blade diameter or larger, or you aren't changing the noise problem much to get the same airflow thru the case.

Always keep in mind that airflow is just that--flow. it has to come from somewhere and go out somewhere else, in a flow across the hot parts, or you might as well not have it at all. ;) Just picture it in your head or if necessary draw it on paper, but it's easy to see where air flows and heat comes from and where it has to go to be gotten rid of most efficiently (and thus more quietly).

I'll still add a dust cover I think because with the fan on top, it will be much more dust prone!
Click to expand...
Just remember not to put it on there while it's in use. ;)

And also remember that much much more dust will be sucked in whille in use than when it's just sitting there, so a dust cover will do very little for the insides.
 
this guy doesn't have dust. it's london, there is no exposed dirt for 40 miles. i am sure the place is like spotless too. so worrying about dust is like worrying about snow in phoenix.
 
Ok ok, I'll try a small plastic cabinet, remove completely the grill and cushion with noise isolation foam.

Will see how it goes.


I'm also considering changing the trim pot to a potentiometer. I'm not sure how to read the part number. It seems that the number 102 means 1K as resistance?

Can I get this one?
http://www.ebay.co.uk/itm/1K-Potentiometer-Variable-Resistor-Linear-Pot-RoHS-/130489960475?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item1e61cec81b#ht_1109wt_902

I would put it on top of my charger, so I can easily update the voltage/current when I need it.
 
Most of the dust in the home is from dead skin particles (so I have heard), and it sounds like he has a few bodies sharing a small space.. So, dust....
this guy doesn't have dust. it's london, there is no exposed dirt for 40 miles. i am sure the place is like spotless too.
Click to expand...
 
cwah said:
I'm also considering changing the trim pot to a potentiometer. I'm not sure how to read the part number. It seems that the number 102 means 1K as resistance?

Can I get this one?
http://www.ebay.co.uk/itm/1K-Potentiometer-Variable-Resistor-Linear-Pot-RoHS-/130489960475?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item1e61cec81b#ht_1109wt_902

I would put it on top of my charger, so I can easily update the voltage/current when I need it.
Click to expand...
You would be better off moving the existing pot there, because if you use a partial-turn pot like that it is much coarser than the probably multi-turn pot already there, making it it a lot harder to adjust exactly where you want it. Plus they are not sealed like the ones already there, so humidity can change the resistance and thus the charger's behavior.

Even better would be only to drill a tiny hole just big enough for a plastic adjustment tool to reach down to the pot inside, put a little straw on the end of the adjustment tool so it stays on the screwhead of the pot while turning, and do that when you need to instead of opening it up. Common on old TVs and radios and such for adjustments. (use plastic tools so if you drop it in there you don't blow it up). Tape over the hole when not in use if you like.

But if you have to adjust it so often that opening it up to do it isnt' really an option, you have a different problem that needs to be solved.
 
Ahah, you're right. I can maybe just adapt a bit of plastic to fit the trim pot!

Here's what I did why a small acrylic rod:
trim%20pot%20rod.jpg


I filed the end in order to fit the T shaped knob and added a drop of superglue in order to keep it straight.

Now I just have to do the same on my charger and add a bigger know for adjusting!


ps: I tend to adjust frequently the voltage depending on the situation:
- For daily commuting I charge to 70% (20s A123 at 67V)
- For longer tripe charge to 100% (72V)
 
I'd like to be able to carry the charger on my bike when travelling.

Xan I use some RTV sealant to protect from vibration?

I'm thinking that the sealant may cause the cooling more difficult... or is it ok :?: :?:
 
I think I'm going to get this variable resistor at 100ohm:
http://www.ebay.co.uk/itm/2x-Multiturn-Cermet-Potentiometer-Trimmer-/260979312541?pt=UK_BOI_Electrical_Components_Supplies_ET&var=&hash=item3cc394479d#ht_773wt_788

So I should be able to adjust the speed to my need. Would that work?
 
In case it hellps you, the Pot nearest the corner adjusts the voltage. I took one up from 42v to 60v without changing the other pots, and it didn't complain.
 
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