36v Charger resister identifying HELP!

[skeetab5780]

hi sorry that you have to click on the link to see the pictures, but please try and help me out. I just bought this charger for my 36v SLA ebike and successfully charged the bike 3 times. Then i had a genius idea to try and charge 2 sets of batteries at the same time in parallel. And when i connected the second bike the connectors Arc welded for a Bright surprise and startled me. Since this i plug the charger in and the light blinks red, and when i connect it to a battery the light goes solid like its charging....So i left it to charger the dead bike overnite...Went out with a meter in the morning to check the voltage which should sit around 39-41v since thats what it says on the charger. But instead the batteries read 29v (lower then my LVC off on the bike drains them to) (31.5v) So i opened up the brand new charger and i found the only suspicious looking faulty piece and its a green coated (painted) resister. Im hoping one of you tech savvy gentleman can help me identify if this is the problem. And if so what the resisters value is (or where i can find a replacement to soldier in).

Thanks for reading the post, picture links are below

http://www.facebook.com/photo.php?pid=2666917&l=454cffec4d&id=664853802

http://www.facebook.com/photo.php?pid=2666918&l=34065f0d56&id=664853802

http://www.facebook.com/photo.php?pid=2666919&l=6af17632b3&id=664853802

 

[dnmun]

wirewound power resistor. the value will be printed on it. looks like at least 5W maybe more. do you know if it is burned open?

did you try to find the manufacturer to see if they had a parts index for the charger?

you can post up your pictures in your thread too. use 'upload attachment' under the body of the message.

 

[skeetab5780]

all i know is that there are paint chips flaking off of it and yes the body of the resistor is metal since i tested continuity on itself...but theres no continuity on the leads of the resistor. I have not checked for a parts list online due to the fact that its a 19 dollar ebay charger any other info would be appreciated. and thanks for telling me about the upload feature i never quite figured that out

 

[skeetab5780]

also because of the paint flaking off everywhere i cant seem to see any writing on it. but i google searched 5w wirewound resistor and found some similar looking items. but im not sure where i can buy one atm? any ideas?

 

[dnmun]

of course i already told you my ideas, and of course a 5W wirewound you find on google will look like it because that's what it is. it is not solid, the wire is wound around a ceramic body and coated by ceramic slip before firing. if you don't know how to read the resistor value printed on it then you need to buy a new one just like it and read the resistor value on the resistor in the new one. if they are only $19 then you can buy a new one for the cost of repairing that one. that's the american way, and it helps the global economy by providing more jobs for poor people in china.

 

[TylerDurden]

As Dmnun says; if you get another identical charger, you can read the resistor value of the new unit and get the replacement resistor for the damaged one.

After repairs, you then have two chargers to accomplish the original goal.

 

[skeetab5780]

thank you for your replies, i was kind of hoping to fix it for mayb 50 cents. But it was worth a shot posting on here.

 

[dnmun]

some of the power resistors in that size are less than 50 cents, up to a little over a buck.

if you get an identical charger and it has the same part then you will know what to order and then be able to replace it with the correct resistor value. maybe you already have a charger made by the same people and they may have the same parts, except that shunt is likely specific for the charger current which is why they used a wirewound.

but then you have two chargers, which you needed anyway.

 

[skeetab5780]

well i went to Radio Shack today and purchased a 5w power resistor for under 2 bucks and soldered it into my cheap charger. Its seems to have done the trick although the one i took out was only a 3w. Im not sure what effects this will have with extended use, but the charger is testing 41v at the leads. On another note, the reason the charger broke in the first place has been identified! When i put the charger port (basic computer plug 3-prong) onto my 2nd bike i was trying to charge simultaneously with the first bike, i had the polarity reversed, therefore causing both bikes to in theory be connected backwards to each other. Thank you all for the posts and you help identifying the part/problem.

scott

 

[dnmun]

i don't know if you ever posted up a picture of the original position on the pcb and the resistor itself. but i have a 36V lifepo4 charger open in front of me and the shunt resistor on the output is about 3W and is brown black silver so i think that is 1 ohm. is your resistor tied to the negative leg of your charger output? maybe if you posted up something to look at we coulda helped you figure out the right part. or even read the value off the resistor.

is 41V the output voltage on your charger? this is for SLA right?

 

[skeetab5780]

yes it is an sla charger and there were pictures posted on my first post...3 links but i took them down because i fixed the charger. Thank you for your reply