# Russco charger malfunction (again)



## Russco (Dec 23, 2008)

madderscience said:


> Hi all
> 
> My 3-year old russco 24-120 charger seems to be acting up again.
> 
> Any ideas?



Perhaps the Russco Factory might know what's going on. 

Maybe.


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## Russco (Dec 23, 2008)

madderscience said:


> Hi all
> 
> My 3-year old russco 24-120 charger seems to be acting up again.
> 
> ...


Well, no one else has replied to your question, so I'll give it a try.

I know a little about Russco chargers. 

So you're charging a 126 volt pack?

Are you aware your SC24-120 charger is for charging 132 and 144 packs ONLY? Read your manual.

Operating this charger into a 126 volt pack will over-current the charger. Your 11 amp output verifies this.

No wonder you're having problems! The charger has been mis-applied. 

You can't blame the charger for that.


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## madderscience (Jun 28, 2008)

Russco said:


> Well, no one else has replied to your question, so I'll give it a try.
> 
> I know a little about Russco chargers.
> 
> ...


Huh. Well I dug out my manual, and on page one, the specifications say:

Voltage, output: 100-212 VDC (adjustable)
and a few lines down...
Amperage, output 12.5 Max Amps (adjustable)

And the sticker right on the front of the charger says:

Voltage: 80 - 200VDC
Max amps: 15

(a little grainy, but readable here) :
http://amphibike.org/images/640_chargerAndTransformer.jpg

The only specific mention of 132 and 144 volt charging in my manual has to do with setting up the boost transformer. (which I determined by trial and error is also necessary with 126V). It is worth noting that there are some significant discrepancies in the manual vs. my actual charger (specifically, the timed shutoff is completely different in my charger compared to what the manual describes, and of course the differences in output specifications between the manual and the charger as seen above)

I am guessing that perhaps the specification maybe have changed since I got my charger, or I got a transitional unit in-between designs, maybe unintentionally. The only other explanation is that I got the wrong manual (with the right cover page) and also the wrong stickers got applied to the charger, and I doubt the latter more than the former.

Given this, any further ideas? Failing that, diagnostic steps? Not interested in fixing blame, only fixing problems 

In the meantime I'll keep the current turned down.

thanks for your replies.


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## Russco (Dec 23, 2008)

madderscience said:


> Huh. Well I dug out my manual, and on page one, the specifications say:
> 
> Voltage, output: 100-212 VDC (adjustable)
> and a few lines down...
> ...


The _Introduction_ on page 1 of the SC24-120 manual states:

"The RUSSCO Safety Electric Vehicle Battery Charger provides on-board charging of both flooded and sealed lead acid battery systems of 132 and 144 volts."

The charger label has minimum-maximum ratings that may not relate to your case. As an example, the 212 VDC rating is calculated by taking the 120 volt line voltage + the 32 volt boost voltage = 152 v. times 1.414 for the peak voltage = 212 volts. But charging a 144 volt pack to 15 volts/battery = 180 volts, so the 212 volts means little.

Your shut off difference may be due to your charger having an analog vs. digital shut off option. Don't know without your serial number.

Best bet is to have your charger evaluated/repaired by the Russco factory. We have been manufacturing and servicing our chargers for 12 years now.


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## JRP3 (Mar 7, 2008)

Russco said:


> The charger label has minimum-maximum ratings that may not relate to your case.


This seems like a really bad idea. I think most people would assume a label that shows 80-200 volt range means anything within that range is in spec.


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## madderscience (Jun 28, 2008)

OK, well my confusion is well founded it seems. Yes, the introduction does say 132 and 144, I probably ignored that given the other specs in the book and the label on charger itself which suggest a much wider voltage range is fine, as has already been pointed out. So I will concede that I am apparently abusing the charger. I would humbly suggest however some clarification to the manual and labeling and some added emphasis to the voltage range requirements.

So back to fixing it. Right now I can't find a serial number on the charger. It is in a recessed location in the car behind the driver's seat (plenty of ventilation though; I made sure of that) and I can't find the number. That will have to wait until I pull the charger. This may not be for a while since it IS working and I have other stuff to attend to. So I'd like to just gather some more information at this point. Since it is out of warantee anyway, I would like to fix it myself if possible (I am not new to fixing electrical equipment) but I am humble enough to know when something is over my head and at that point I would be willing to send it in. So In the meantime, if it is a given that this charger is misapplied for a 126V pack, and it is also a given that I don't really want to replace the charger, a couple questions:

1) realistically, is a 6V difference (less than 5% overall relative to the 132V minimum) in nominal pack voltage really enough to cause the charger to have problems? (bearing in mind that for about the first 6 months my car was running I used this charger (without the boost transformer) to charge a 102V pack with no problems at all, before I added 24V of additional batteries to get to my current battery configuration)

2) if the answer to 1) is yes, then would keeping the current setting turned down to something below the maximum mitigate any further issues with the charger owing to the lower voltage battery?

3) what about this charger makes it limited to 132 to 144V nominal battery voltage? I'm sure the LC filter and the igbt/mosfet/whatever that throttles the current can handle a slightly lower battery voltage than that as long as the current is kept to a manageable level. What component(s) are operating out of spec here? Maybe it just is a bit out of its peak efficiency range?

More random info: My settings with the 126V battery have always been a voltage knob setting of about 75 to 80 depending on the ambient temperature (warmer == lower number) and I have always had the current knob set to its maximum except for times when I was charging off of a 15A circuit or using a long extension cord (most of the last 6 months actually, I recently moved and I did not get a good charging outlet installed until only a few weeks ago). I've never popped a 20A mains breaker with the charger unless something else big was plugged into the same circuit and the charger's own 20A pop-out breaker has never popped except for when it had the bridge rectifier failure. As for overcurrent on the output side, I have popped the 15A output fuse once or twice due to my own stupidity, but in normal usage it has never blown until this most recent issue started occuring.

Thanks


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## Russco (Dec 23, 2008)

madderscience said:


> OK, well my confusion is well founded it seems. Yes, the introduction does say 132 and 144, I probably ignored that given the other specs in the book and the label on charger itself which suggest a much wider voltage range is fine, as has already been pointed out. So I will concede that I am apparently abusing the charger. I would humbly suggest however some clarification to the manual and labeling and some added emphasis to the voltage range requirements.
> 
> So back to fixing it. Right now I can't find a serial number on the charger. It is in a recessed location in the car behind the driver's seat (plenty of ventilation though; I made sure of that) and I can't find the number. That will have to wait until I pull the charger. This may not be for a while since it IS working and I have other stuff to attend to. So I'd like to just gather some more information at this point. Since it is out of warantee anyway, I would like to fix it myself if possible (I am not new to fixing electrical equipment) but I am humble enough to know when something is over my head and at that point I would be willing to send it in. So In the meantime, if it is a given that this charger is misapplied for a 126V pack, and it is also a given that I don't really want to replace the charger, a couple questions:
> 
> ...


Engineering 101: The Russco SC24-120 is a beefed up SC18. This is done by taking a 15 amp input/output SC18 and using a mandatory 32 volt boost transformer, allowing a 20 amp input with the 15 amp output. This works since the 25% boost in input voltage will drop the output current by 25%.

Of course, the input components of an SC24-120 has to be heavier, but the output components can be the smaller SC18 size.

If you understand the preceding statements, then not using the boost, as you did with your 108 volt pack, will place the output at 125% rated current and over-stress the output wiring and components such as the FWB, wiring, and inductor. Using the boost wired for 16 volts, will also cause the output current to be too high.

This is why the manual states to use the mandatory 32 volt boost transformer, which would be required for 132 and 144 volt packs anyway. 

The SC24-120 charger could pull 20 amps from the AC line. The more popular SC18-120 can pull 15 amps; That's 2400 vs. 1800 watts. 

The SC24-120 information on the Russco web site and retailers always stated the charger was for 132-144 volt packs and the boost transformer (32v) was required. So now you know why the FWB failed.

End of class.


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## madderscience (Jun 28, 2008)

Thank you for the explanation. I fully understand basic electrical concepts and I would not intentionally use the wrong tool for the job. We have already gone over why I ended up misapplying the charger. I am just trying to diagnose what is actually wrong at this point and determine what I can do to avoid issues in the future. 

Given that the SC24 is a SC18 with a bigger input side, I am not sure why a slightly lower boost voltage might not be another option in my case though, based on your description. I was going to ask that but it sounds like you think that won't work. To me anyway, it sounds like its all about keeping the current under control and that would do it.

You didn't answer whether or not you thought turning down the output current would mitigate this problem. Or put another way, What is the maximum sustainable output current for an SC18 or SC24?

Define FWB please. I am assuming that is the control board.

I will post to this thread again if and when I figure out what the issue is.

Thanks again.


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## Russco (Dec 23, 2008)

madderscience said:


> Thank you for the explanation.
> You didn't answer whether or not you thought turning down the output current would mitigate this problem. Or put another way, What is the maximum sustainable output current for an SC18 or SC24?
> 
> Define FWB please. I am assuming that is the control board.
> ...


Operating any Russco charger at a Current setting of 100 is recommended and within the charger rating. Of course, this assumes the charger is connected to the proper voltage pack and using the boost transformer, if required. If, however, in your case, turning your Current down makes the charger happy, go for it.

FWB is Full Wave Bridge, a 4 diode, single phase rectifier.


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## CPLTECH (Sep 14, 2007)

I may be totally off-base, but could it possibly be a defective fuse holder?
Never have seen one of those chargers, but 15 amps is a lot of heat should the holder not make a good, firm connection. I know my K&W had a poor output fuse holder & the excessive heat caused the fusible element to melt. How warm does your fuse holder get?

In my experience, a solid state semiconductor is either good or permanently bad [shorted], therefore the above comment as higher amps are delivered.


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## madderscience (Jun 28, 2008)

The fuse holder is fine. I did have a recurring fuse holder issue elsewhere in the charging circuit (not part of the charger) but I recently have changed to a bigger form factor of fuse. 

I really don't think anything is wrong with the current handling components of the charger (LC filter, bridge rectifier and current limiting silicon (mosfet, or whatever it uses, I haven't dug that deeply into it) despite the previous suggestions from Russco. I base this on the facts that

1) It works fine with the current knob set low. So whatever actually switches the current is working.

2) The current ramp-down and shutoff timer are working. 

My own theory is that whatever measures output currrent to limit it when the current knob is maxed out is at fault. If the charger uses a hall effect device to measure current, it may have failed. I had such a failure occur in a welder I have with similar behavior (unstable, too-high current) Without having yet disassembled the charger to actually look at how the control board works, I am only speculating however. 

Another theory that was posited to me out-of-band from this forum thread was that the current knob potentiometer was noisy or making poor contact. This came from another person with a russco charger who has experienced this. I don't think its the problem in my case though.

I probably won't take anything apart anytime soon since I can put up with charging at a somewhat lower rate. If and when I do identify the problem I will post again to say what it was.


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## electricmotorcycles (May 9, 2010)

i also have a russco charger [SC 18-120] that has some issues, when i got it it would oscillate between full and half amps. i sent it back but the manufacture said there was nothing wrong with so i just dealt with it for four year now. however now it shows it only charging at zero or low amps and the 30 minute time out activates as soon as i plug it in, no matter how i adjust it. do you think it can be fixed? i don't think the manufacture will be of any help in this case.


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## Russco (Dec 23, 2008)

electricmotorcycles said:


> i also have a russco charger [SC 18-120] that has some issues, when i got it it would oscillate between full and half amps. i sent it back but the manufacture said there was nothing wrong with so i just dealt with it for four year now. however now it shows it only charging at zero or low amps and the 30 minute time out activates as soon as i plug it in, no matter how i adjust it. do you think it can be fixed? i don't think the manufacture will be of any help in this case.


Russco still supports Russco chargers. Contact the Russco Factory for information.


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