Help Needed: Charger has 3 wires, Battery 2. How to connect?

[floatingdog]

Please forgive the rookie questions. I'm electronically challenged and don't want to blow up my first build before I even hook up the motor.

I have an BMSBattery.com charger I'm trying to put Andersons on. I only need two wires, + and -, to connect to my 48v SLA battery pack. The charger has 3 output wires as shown in the picture.

1. Should I run both the charger(-) wires into the negative wire going to the battery? (I just read the printing on the charger, that the brown output wire is (+) and the blue one is (-). I'm now guessing the answer is just to ignore the other wire.)

2. My charger puts out 54.6v and my 4x12v SLA battery pack is reading 50.6v right now. Does it sound like my charger is set up correctly for my 48v SLA pack (4x12v)?

3. I think the charger is primarily targeted for Lipo or Lifepo4. Anything I need to watch out for or worry about?

Thanks in advance. All answers and tips are greatly appreaciated.

 

[amberwolf]

1. Should I run both the charger(-) wires into the negative wire going to the battery? (I just read the printing on the charger, that the brown output wire is (+) and the blue one is (-). I'm now guessing the answer is just to ignore the other wire.)

This is probably the case, but it depends on what that other wire was intended for (a sense wire, perhaps, or perhaps is not even connected internally).

2. My charger puts out 54.6v and my 4x12v SLA battery pack is reading 50.6v right now. Does it sound like my charger is set up correctly for my 48v SLA pack (4x12v)?

That's not enough to charge your pack quickly, most likely. My 12V 17Ah batteries recommend 14.4V to 15V for cyclic use, so if yours are similar they'd need 57.6V to 60V to charge 4 of them.

Also, what current is your charger limited at? Check the label on the batteries themselves, (most SLAs I've had are marked with a recommended charge current and voltage). Mine have a max of 5.1A charge current.

3. I think the charger is primarily targeted for Lipo or Lifepo4. Anything I need to watch out for or worry about?

See above.

 

[deardancer3]

I had a charger something like yours. Cut the hokey connector off. you will find only two wires went to the connector. The middle pin is blank.

put red anderson on positive wire and black on negative. be sure to read up on the right way to do anderson connectors.


some Lifeo chargers are set to a slightly higher cutoff voltage than some SLA's want, so the float voltage may be a little high, shortening the life of your packs some if left on a long time. You would have too look up your brand and model of batteries, and record the voltage on your charger after it goes green. Also what current the charger wants to put out, and what the maximum current the batteries lik- most likely OK.

You need to make sure your 4 SLA's are pretty close to balanced on state of charge/ depth of discharge before starting. If not, then that makes this a little more complicated since this is a series charger sending the same curent to all cells, if some are overcharged and the charger is still pushing big amps, the overcharged cells get overheated shortening their life and making for a safety issue.

Monitor pack voltages and temperatures during the first charge cycles. I would disconnect the charger as soon as it goes green and report back here with the data. If any pack starts to get warm also turn the charger off. If the voltage goes much above 62v, turn the charger off. If any SLA goes above 16v, turn the charger off.

All this is just for the first time to prevent a problem until we know the particulars. AS always, wear safety glasses.

The voltage the charger is putting out open circuit is not the same it will put out at the ending of the charge cycle.

Talk sweet and some one here may do the research for you if you send the info.


d

 

[floatingdog]

deardancer3 and amberwolf,

Thanks so much for your detailed responses and sorry for my late reply. The wonderful world of computers and customers that expect their systems to work (imagine that) has kept me from installing a single Anderson connector all day. I have a 5 hour reprieve now and can maybe get as far as connecting up my charger thanks to your kind input.

The charger has 3 output wires, apparently all connected. Two act like (-). The label on the charger indicates the brown one is (-), so I think I'll just use it and ignore the other.

2. My charger puts out 54.6v and my 4x12v SLA battery pack is reading 50.6v right now. Does it sound like my charger is set up correctly for my 48v SLA pack (4x12v)?

That's not enough to charge your pack quickly, most likely. My 12V 17Ah batteries recommend 14.4V to 15V for cyclic use, so if yours are similar they'd need 57.6V to 60V to charge 4 of them.

Also, what current is your charger limited at? Check the label on the batteries themselves, (most SLAs I've had are marked with a recommended charge current and voltage). Mine have a max of 5.1A charge current.

I can presumably bump the charge voltage higher voltage if I pop the lid on the charger. I'd like to use the charger as is if it won't damage my batteries by undercharging them. I don't mind slow charging. One run per day is probably all I will do. I'm sure I'll spend the bucks for 'real' batteries if I get this thing running and have fun.

The batteries are good for a max of 2.2A charge current if I understand their label. Am I going to fry them with my little 240W/3A charger? Hopefully having them in series means I can charge them with more than 2.4A. Is this wrong?

put red anderson on positive wire and black on negative. be sure to read up on the right way to do anderson connectors.

some Lifeo chargers are set to a slightly higher cutoff voltage than some SLA's want, so the float voltage may be a little high, shortening the life of your packs some if left on a long time. You would have too look up your brand and model of batteries, and record the voltage on your charger after it goes green. Also what current the charger wants to put out, and what the maximum current the batteries lik- most likely OK.

You need to make sure your 4 SLA's are pretty close to balanced on state of charge/ depth of discharge before starting. If not, then that makes this a little more complicated since this is a series charger sending the same curent to all cells, if some are overcharged and the charger is still pushing big amps, the overcharged cells get overheated shortening their life and making for a safety issue.

I read various instructions for building Andersons and think I did a fair job. They seemed to snap together as advised. I crimped with no solder. My crimping tool was the weakest leak. I must find my good crimper! They seemed to snap together as advised.

So far I've put together 2 anderson and 8 f2 connectors connectors so far for my battery pack. I know those here are not easily impressed by such feats of engineering , but I was quite pleased to see the correct voltage reading after I wired my SLAs together. Included was a 30A inline fuse.

My SLA's were within .01v of each other. They have been on a shelf for a while and all read 12.60 or 12.59. So hopefully I'll be ok with parallel charging them and they are not ruined by being on the shelf too long.

Thanks again for your tips. I'll be careful and watch closely until I trust my charger and batteries. I guess I have to unplug every other battery wire to read the individual battery voltages to make sure they remain balanced during the charging process.

John

 

[floatingdog]

Separating my question from my previous post lest it be lost in all my jabbering:

Will my 240W, 54.6V ("4A") charger fry my small SLAs? I have 4 12v, 7AH SLA batteries wired in series for a 48V pack. The individual batteries are labeled as handling a max 2.4A charge current.

Update: I've been charging them for an hour now. Batteries and charger are cool to the touch. Is this an indication I'm not cooking the batteries with too many amps?

Update 2: Charged for a little over 2 hours. The pack voltage came up from 50.4V to 51.9V and the charger cut off. Sounds like I will need to adjust the charger to put out a little more than the 54.5V it is putting out.

Thanks!

John

 

[amberwolf]

The wonderful world of computers and customers that expect their systems to work (imagine that)

It is not even so much that people expect them to work, it's that they expect them to work the way *they* want them to, often a different thing from the way they are actually designed to do. (Although I think that in many cases the user is reasonable in expecting that, and that the program or hardware is not designed "properly", with the user in mind).

I can presumably bump the charge voltage higher voltage if I pop the lid on the charger. I'd like to use the charger as is if it won't damage my batteries by undercharging them. I don't mind slow charging. One run per day is probably all I will do. I'm sure I'll spend the bucks for 'real' batteries if I get this thing running and have fun.

Heck, my SLAs run me fine for most of my trips. With my newer more efficient 4-pole motor (used a 2-pole before) I get better acceleration *and* range; at an average of around 14MPH cruising speed, with at least a couple of dozen full stops and starts, I easily got 12 miles today, with plenty of power to spare (batteries still at 11.4V each with a 2A load on them).

My dislike of them is because of their weight, power density, and Peukert effect problems when drawing high currents from them, otherwise I would have no desire to change to something else. SLAs can be had for free, or at least very little, if one is always on the lookout for storm-destroyed UPS systems, people with powerchairs or electric wheelchairs that change out their old ones; things like that. They don't have the capacity they started with, but almost always have a significant amount of usability left! (like mne now!)

The batteries are good for a max of 2.2A charge current if I understand their label. Am I going to fry them with my little 240W/3A charger? Hopefully having them in series means I can charge them with more than 2.4A. Is this wrong?

If you have a way to limit the current downward in the charger, I would do so. If you charge the SLAs with too high a current, you will heat them up too much and boil off some electrolyte. Since they are "sealed", you can't put that back later.

If the charger has a current limit adjustment in it, use that. If not, you might be able to put a resistor (like a light bulb, perhaps) in series with the charger to battery connection. If you put anything in series to drop the current, though, it will also drop the voltage actually reaching the pack.

So far I've put together 2 anderson and 8 f2 connectors connectors so far for my battery pack. I know those here are not easily impressed by such feats of engineering , but I was quite pleased to see the correct voltage reading after I wired my SLAs together.

I cheated; my Andersons came pre-crimped out of a big server UPS, along with the SLAs they connected to. Saved me a lot of work! Looks ugly since the wire lengths are not really optimal for my arrangement, but they are very large wires (bigger than any wire stripper I have, probably 6 or 8 Gauge for the largest, and I think 10 for the smallest) and none are more than a foot or so long. Each battery has it's own Anderson on it, so I can swap them around or change them out relatively easily without unbolting from them. Wherever it was necessary to connect two batteries together, the harness Andersons were bolted together at their ends to make series connections, and then heatshrinked over this.

My SLA's were within .01v of each other. They have been on a shelf for a while and all read 12.60 or 12.59. So hopefully I'll be ok with parallel charging them and they are not ruined by being on the shelf too long.

Parallel charging is fine when they're close like that. The only thing you should do when leaving them unused for a while is to top off their charge every few months at most, or more often if possible. Any lead-acid battery sulfates (permanently degrades it's capacity) if it sits at less than full charge. It probably sulfates anyway, but much more the lower it's voltage. I top all my spares up every month if I can.

Thanks again for your tips. I'll be careful and watch closely until I trust my charger and batteries. I guess I have to unplug every other battery wire to read the individual battery voltages to make sure they remain balanced during the charging process.

You can get a quick idea even when they're charging and connected, if you just measure across each battery during charging. If they're badly out of balance you'll see it then, too, not just individually. You will also see it under load when running your motor.

Part of the reason I chose to andersonize each battery separately was so I *could* just quickly disconnect one from a pack, in case I needed to read a voltage, etc. But I also did it so I could charge the pack with my existing stuff, since I only have one SLA charger, which is 24V/3A, and I must use a separate CC/CV supply (Sorenson linear bench lab supply, adjustably current limited and precision voltage adjustable output, weighs a ton) for the other battery. I could also use the Sorenson for all three, but I'd rather use the SLA charger where I can.

 

[BLUESTREAK]

Just leave the third wire that is in the top of the triangle unhooked. The charge is designed for lead acid battries and the voltage is correct. it is not enough for lifpo4 thay need at least 58.4 volts output. Hope this helps.

 

[floatingdog]

Everyone, thanks once again for the thoughtful replies.

Amberwolf,

It looks like I lost my thoughtful response in my late night haze last night. I have to start learning to hit save more often. I liked your procurement stories. I bought most of my stuff retail after much searching for best prices. powerwerx.com has great deals on Andersons and a really nice fuse kit. Their packaging and prompt shipment was really impressive in contrast to some of my overseas purchases. My procurement score was a 12 ft. section of really nice 12GA (300v) 3 wire used power cord for $5. The individual wires look to be ptfe coated with really high strand count. It really contrasts with the skinny wires coming out of my motor and controller. I have a Bafang BPM (BMC sized geared motor) and a small ecrazyman sensorless controller (36v X 25a).

My lost email stated that my charger probably has three pots inside based on pictures of its bigger brother posted here on ES. One is for voltage, one for LVC, and hopefully the third is for current.

I've plugged my charger back in and it briefly went back on and the green light indicating charging complete came on pretty quickly. It is cutting off with only 12.85 avg in each cell. I thought I should be getting more like 13.5V full charge. I'll leave it running for a while. It seems like I've read the lifepo4 chargers like to cut on and off at the end of the charge. Perhaps it will cut back on after a while.

It sounds like you think my "250w/4A/54.6v" charger is pumping too many amps into my 4 serialized 12v 7AH batteries rated for 2.4A cyclic charging. I guess the proper thing is not to charge at greater than 2.4A even though the charger and batteries remained completely cool.

Bluestreak,

Thanks for your input too. I left what was presumably the third wire at the top of the triangle disconnected, but perhaps I got it mixed up with the negative. I can't seem to find the cut off connector to check. The wire I'm using works as (-) according to my multimeter. Do you think the charger might cut off prematurely if I chose the wrong wire? As noted, the charger was primarily designed for lipo or lifepo4. I don't really know what the third wire was for. It was in fact connected in the charger.

Thanks,

John

 

[BLUESTREAK]

HI FLOATINGDOG: The charger that you have was designed for 48 volt lead acid at 54.6 volts. I just checked my 48 volt lead acid charger and it put out 54.8 volts ,51.? volts is not enough.I also just checked my 48 volt lifpo4 chargers,one reads 59.5 volts and one puts out 58.4 volts.you need to find the proper ground wire from that triangle plug that you have, don't twist the two ground wires together the odd ground is designed to ground the metal frame of a syste m the other ground is for the battery ground, sorry i can't post pictures yet. that would help. Hope this helps. COOPER

 

[amberwolf]

It looks like I lost my thoughtful response in my late night haze last night. I have to start learning to hit save more often.

Type it up in notepad first, and save as a temporary copy somewhere (I usually use the desktop, then drag all the files into a "stuff" folder at the end of the night). Save early and often, and if you make major changes, save witha number on the end of the filename so you can go back if you really mess up what you were trying to say.

Alternately, if you use Windows, there is a program called Clipboard Magic, freeware, that you can setup to run on startup. Then every so often just press CTRL-A and then CTRL-C to copy everything, and it will be stored in CM's memory, along with every previous thing you've copied that way, up to whatever limit you set in the program. Then if you lose something, just go back to CM's little icon near your clock, and scroll thru it's list of what you copied. Double click the one you want out of the list and then go back to wherever you were to re-paste it in.

I liked your procurement stories. I bought most of my stuff retail after much searching for best prices. powerwerx.com has great deals on Andersons and a really nice fuse kit. Their packaging and prompt shipment was really impressive in contrast to some of my overseas purchases. My procurement score was a 12 ft. section of really nice 12GA (300v) 3 wire used power cord for $5. The individual wires look to be ptfe coated with really high strand count. It really contrasts with the skinny wires coming out of my motor and controller. I have a Bafang BPM (BMC sized geared motor) and a small ecrazyman sensorless controller (36v X 25a).

I'm not very familiar with either of those, but I've read of them here on ES. It seems like most motors and controllers don't have wire big enough to actually support the current they really draw or supply. Batteries and chargers too.

My lost email stated that my charger probably has three pots inside based on pictures of its bigger brother posted here on ES. One is for voltage, one for LVC, and hopefully the third is for current.

Those should help, if it is adjustable far enough.

I've plugged my charger back in and it briefly went back on and the green light indicating charging complete came on pretty quickly. It is cutting off with only 12.85 avg in each cell. I thought I should be getting more like 13.5V full charge. I'll leave it running for a while. It seems like I've read the lifepo4 chargers like to cut on and off at the end of the charge. Perhaps it will cut back on after a while.

It probably is not charging full enough because it is not a high enough output voltage, I think. You should get 58 to 60V while it is connected to the batteries and charging them, at the output of the charger. Each battery should have 14.4 to 15V across it during charge.

Otherwise, it's voltage is so close to the battery voltage that little current is being drawn. That is probably why nothing gets warm.

Right now you're getting 51.2 pack voltage, and the charger only outputs a max of 3.4V more than that based on it's stated 54.6V rating. I don't know what the internal resistance of the batteries is at that voltage, but I doubt it's enough to draw very much current.

What is the voltage across your pack *with the charger connected* to it and running a charge cycle? I suspect it's even lower than 54.6. If the Li pack it was made for was a 14-cell pack, with 3.8V cell HVC, then the pack HVC would be 50.4. That's even less than your current pack voltage.

Another thing is that a Lithium charger should have a HVC to prevent overcharging of the cells, and a 48V Li pack doesn't have as high a charging voltage as a 48V SLA pack, so that HVC is probably

It sounds like you think my "250w/4A/54.6v" charger is pumping too many amps into my 4 serialized 12v 7AH batteries rated for 2.4A cyclic charging. I guess the proper thing is not to charge at greater than 2.4A even though the charger and batteries remained completely cool.

I think they're staying cool because there isn't that much current flowing right now due to the lack of difference between the charger output and the battery no-load voltage.

I definitely would make sure that you aren't charging the batteries with a higher current than they are rated for--it will work, and they will charge faster, but they'll also age faster and lose capacity sooner. SLAs last short enough time as it is.

 

[deardancer3]

get yourself a .1 ohm 5 watt resistor and insert it on one leg of the charger.

Then you can measure the IR drop across this resistor and calulate the current.

this will tell you a lot.


d

 

[floatingdog]

get yourself a .1 ohm 5 watt resistor and insert it on one leg of the charger.

Then you can measure the IR drop across this resistor and calulate the current.

this will tell you a lot.

Thanks deardancer3! I'm completely out of my league here. Let me see what i can come up with.

From Google: V = I x R is the Ohm's law. (I've heard of Ohm's law, but don't have a clue what it is, yet.) So perhaps some how I can determine amps in by measuring volts in and volts out of the resistor of a known value. Back to Google.

Eureka! Duh! Many multimeters (like my nice Fluke 77III) have an ampere scale. I put the red cable on my multimeter into the 10A hole and twisted the knob to the 'A DC' position. Then I stuck the leads into the my red and black Andersons (+ to +, - to -), and plugged in the charger. It fired right up and read 4.05A. The charger is marked as 4A, so I think I did it right and the manufacturer didn't lie!

So my charger is putting out 54.6V @ 4A and my battery pack is 48V (4 12v SLAs with Cyclic charging capacity of 2.4A). So the question is: Can my pack take the 4A when charging it in series or do I need to reduce the charger amps to 2.4A? I don't know if connecting them in series allows for more amps, say 4 x 2.4A, or the limit for the pack is the same as the individual battery limit of 2.4A.

I think from the previous responses, I do need to reduce it. Right? I guess I'll have to add inline resistors or see if there is an internal adjustment.

Thanks!

 

[deardancer3]

Dont leave that ammeter plugged in for long, it may not have a shunt that can handle the current for long.

However, I would like to know how much current the charger is providing one the light goes green.

And yes, we would like to see the charging current go down. This charger is set up for bigger batteries.

d

 

[floatingdog]

d,

I didn't leave the multimeter hooked up long. The green light is on when the charger is plugged in and nothing connected. I stuck the multimeter leads in and and it went red and gave me some sparks that startled me. Nothing welded. Hopefully I didn't damage the andersons. I guess, I'm not ready for lipo. LOL.

I'm guessing you are wanting to see if it is putting out a low amp charge at the end when the red led goes off. I'll have to splice in the multimeter with the charged battery hooked up so that it will trip to green. Perhaps the 4A kicks down shortly after hook up and it will continue to charge at a lower rate. Maybe if I give it several hours, I'll see the batteries climb above 12.9V (x4). So far I've only brought them up from about 12.6 to 12.9. I didn't notice how long it stayed on red the first time I hooked up the charger. I'm haven't had a chance to hook up the charger for an extended number of hours when I can watch it.

I'll work on knocking down the charging current.

Thanks,

John

 

[amberwolf]

Eureka! Duh! Many multimeters (like my nice Fluke 77III) have an ampere scale. I put the red cable on my multimeter into the 10A hole and twisted the knob to the 'A DC' position. Then I stuck the leads into the my red and black Andersons (+ to +, - to -), and plugged in the charger. It fired right up and read 4.05A. The charger is marked as 4A, so I think I did it right and the manufacturer didn't lie!

I really strongly recommend you go back and re-read what's been posted about how to hook up the meter for reading amps, or you are probably going to at least blow the fuse on the meter, and potentially damage it (or the item you're measuring).

If you hook it up like you did there, you are creating a direct short across the item you're measuring!

That's what makes sparks and melts things, as you've already seen once.

Also, it only tells you what the maximum current is, not what it actually puts out under the load you are actually applying to it (charging your SLAs). To find that out, you must hook it up as described before.


EDIT: FWIW, I also have this meter (in the other style case) and it is a very nice meter. The 10A range can read that continuously, and can take up to 20A for around half a minute or less. Still, hooking it directly across any voltage when it is set to read Amps is a very bad habit to get into, so I recommend simply NEVER doing that. Otherwise, it makes for unhappiness eventually.

So my charger is putting out 54.6V @ 4A and my battery pack is 48V (4 12v SLAs with Cyclic charging capacity of 2.4A). So the question is: Can my pack take the 4A when charging it in series or do I need to reduce the charger amps to 2.4A?

What I posted before applies here.

I don't know if connecting them in series allows for more amps, say 4 x 2.4A, or the limit for the pack is the same as the individual battery limit of 2.4A.

Series means amps stay the same, but volts go up. Parallel means amps go up and volts stay the same.

 

[floatingdog]

Amberwolf,

Thanks! I will heed the advice you give. Hopefully no harm done so far. My apologies for making you repeat yourself. I skipped a posts by you and bluestreak by clicking on the latest post icon from the 'view your posts' screen and not scrolling backwards. I have a way to go before losing newbie status as a forum poster in general and a much longer way to go to lose newbie status on ES. The latter is a much bigger challenge.

Bluestreak,

As noted, my apologies for missing your last post. It looks like my charger is putting out 54.5V which is pretty close to your SLA charger. I may have to open up my charger to see if I've picked the real (-) wire, or the other seemingly (-) wire. I've cut off the computer three prong connector and can't find it despite saving everything else including wire trimmings and mis-crimped connectors.

Thanks,

John

P.S., I googled noob, and decided to call myself a newbie given my high opinion of myself. The definitions vary widely, but my decision was based on the following. LOL

http://www.urbandictionary.com/define.php?term=noob
II. Defining 'Noob'
Contrary to the belief of many, a noob/n00b and a newbie/newb are not the same thing. Newbs are those who are new to some task* and are very beginner at it, possibly a little overconfident about it, but they are willing to learn and fix their errors to move out of that stage. n00bs, on the other hand, know little and have no will to learn any more. They expect people to do the work for them and then expect to get praised about it, and make up a unique species of their own.
...
by Slyke The Phoxenix Aug 27, 2007 share this

 

[amberwolf]

Thanks! I will heed the advice you give. Hopefully no harm done so far. My apologies for making you repeat yourself. I skipped a posts by you and bluestreak by clicking on the latest post icon from the 'view your posts' screen and not scrolling backwards. I have a way to go before losing newbie status as a forum poster in general and a much longer way to go to lose newbie status on ES. The latter is a much bigger challenge.

Everybody starts out new at everything they do.

Two years ago, I rode bikes but didn't even know enough to adjust anything other than the little knobs on the brake levers when the brakes stopped grabbing.

Now I have built my own e-bike almost from scratch (since cutting up bikes and rewelding them into a new one doesn't quite count), and I have learned an awful lot. Still, almost every day I learn yet another thing about them that I feel dumb for not having known before. Sometimes I learn it the hard way, by breaking something. My most spectacular is probably my most recent:

That was a couple of days ago.

I've also destroyed SLAs by overcharging them, putting too much current thru them, and forgetting I had them on the shelf and not charging them for a year.

When I was a kid, I blew up a few multimeters...

I can't exactly afford destructive experiments or losses like that, so I try to be careful, and whenever I learn something that caused me a disaster, I try to pass it on as emphatically as possible.

 

[floatingdog]

Thanks amberwolf. Definitely new here, but I'm stubborn. You know 99% perspiration, 1% inspiration. The folks here at ES have pretty much guided my whole course here, from what to buy and how to put it together. I'm not quite there yet, but am confident I will be with all the generosity here at ES.

That is quite a job you did on your front gears. Fire? Crash? You didn't mention being injured.

John

 

[amberwolf]

Oh, nothing hurt but my pride (and the chainrings). I have a 4-pole 650W powerchair motor with gearbox on there, which outputs around 200RPM into a second reduction stage of a 28T on the motor and a 52T on the other side of the shaft from that taco'd triple above, for around 107RPM max output. Then that is shifted thru the regular 21-speed (currently 15-speed) bike drivetrain of which that triple used to be the front half of.

I had to stop suddenly for a right cross attempt, and was at highest gear. When I started up again, the torque load was so high on that ring it just pried it away like that. I never ever expected that kind of failure. Ever. Guess I know better now.