48v Charger blown

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online4yourmind
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48v Charger blown

Today I connected my 48v 5amp charger to my 48v 10ah lifepo4 battery as I've done for the past month with no problems and today it decided to blow.. Something went pow as it does and nothing at all works, no lights, no fan.. So I decided to try my other 48v 2amp charger which came with my e-bike kit and that also went pop.. Now that just has a ticking noise with the light blinking on and off with the fan but nothing working right..

I've ordered another 48v 5amp charger from ebay but before I connect it I need to know if its going to blow again.. The battery is working fine, it wasn't completely flat before I tried to charge it and still has life left in it..
I took a meter reading from the battery at both ends (the recharge end and lead to controller) and got a reading of 52.6V on both sides.. is this normal?
Does anyone have any idea whats going on and why my chargers have blown?
ps - I also open both chargers and dont see any burnt out fuses or diodes.. fuses on both chargers are ok..

colin9876
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Re: 48v Charger blown

what kind of connector is there from your charger? (My number1 suspect would be that the +ve & -ve of the charger has been connected the wrong way round to the batt, but obviously that cant happen if you have a connector that cant be plugged in the wrong way)

also what make lifepo4 battery is it? Does it have a BMS? (that would be my number2 suspect that a faulty BMS is shorting it)

marylandbob
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Re: 48v Charger blown

If you did not turn the charger ON before connecting it, there may have been a reverse flow of power, from the battery INTO the charger, damaging it, as the capacitors were suddenly charged by the battery.--Some chargers perform best if energized BEFORE connecting the battery, especially in cases such as yours, where the battery already has a significant charge! (Your voltage is OK)--Also, be ABSOLUTELY CERTAIN that battery + and - polarity is CORRECT!-If reversed, damage is VERY likely!--Bob C.

Robert M. Curry

online4yourmind
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Re: 48v Charger blown

Hi Colin, thanks for your reply.. the battery and bms is one of those custom makes ones from China, http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=170607383446#ht_3292wt_1139

All with connectors, so +ve and -ve was correct.. I'm also thinking too about the BMS being faulty and sending a fault.. Is there anyway of finding out if the BMS is sending a short to the battery terminal.. I have a Multi meter and one of those electrical tester to help but I'm not sure on what are the tell tale signs..

online4yourmind
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Re: 48v Charger blown

Hi Bob.. thanks for your reply, I'm pretty certain I turned on the charger first before connecting the charger and battery together, I have done it the other way in the past and weary about the sparks that fly off when I connect the charger plug to the electric socket while the battery is connected, so i usually out of habit connect the charger first..
The + and - polarity is defiantly correct, I got it wrong once before and nearly jumped out my skin, so I know it wasn't that..
Any Idea's on how to check if the BMS is sending a short?

colin9876
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Re: 48v Charger blown

Yes to test for a short turn your multimeter to Resistance testing, (select the lowest Ohms Range) then see what it reads when you connect the probes to the -ve and +ve power outs.
Im not sure what the Resistance ought to be on one of those packs but I would imagine its at least 10miliohms per cell, so maybe 0.5 ohms for the pack?

I personally dont use a BMS anymore. My lastest 'work around' is to use my BalancingBus invention, it parallels up all the cells when Im not using the pack which self levels it. I only connect the SeriesBus when driving or charging.
It didnt get much comment when I posted it on here but in my mind its the discovery of the year! lol.

I got the idea from mf70, just brought all the cells out to Anderson connectors, and a SeriesBus or ParallelBus is connected. I still series charge to an av cell voltage of 3.59v, but then put the BalancingBus on to even out any variations
balancebus.jpg

SeriesBus for running and charging
block.jpeg

online4yourmind
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Re: 48v Charger blown

Well I put the multi-meter on the lowest omhs range which is 200omhs and tested the + and - power outs.. Nothing happens at first but when I remove the multi-meter pongs I get a flash reading from between 150.0 to 180.0.. Does that make any sense of being normal... I'm lost.. But as I was saying before when I connect the battery to the wheel it runs fine.

As for the BalancingBus invention, I'm a complete newbie to all this electric world.. So for now I'm just keeping it simple as the battery pack is completely wrapped up and lots of small cables running off it to the BMS.. but I guess if my BMS is faulty then I guess I'll have to resort to those suggestion..

colin9876
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Re: 48v Charger blown

Sorry to hear that, Unfortunately thats the problem with those taped-up packs, its difficult to diagnose or fix when theres a prob.

The headway cells I now use dont have that problem, because each cell is its own unit and they can be screwed together to make any pack size.
If you bought 16 of those would cost about $300. Not cheap I know but in the long run you have a system where its easy to monitor and exchange any cell if required

IMG135.jpg

Just out of interest what type of bike do you have? and which country are you in?

JLGRAU
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Re: 48v Charger blown

I think you can safely recharge the pack by alligator clipping on to the black and red that's beyond the bms.
In other words bypass or remove the bms, charge then reattach bms.
Did you check fuse inside blown charger? The fuse is probably designed for something you described.
If your charger went up in a puff of smoke, then it's unrepairable (unless you are technical).
I have charge my 48 v lifepo4 packs with alligator clips. I stick paper clips into the charge plug and connect as per polarity onto the main battery wires.
I don't think reverse polarity is your problem as you would have seen and heard a snap, crackle and pop with melted insulation.

colin9876
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Re: 48v Charger blown

If you bypass the BMS (you may see better performance if its removed altogether as no current limiting) its worth monitoring the cell voltages now and again to maintain balance. Any particularly higher than average cells, use a resistor or bulb on to dissipate some of its energy until its back to average.

I also wouldnt aim to go over 3.59v as the cell average if ur not using a BMS, as then you have fair safety margin if one goes bit high.

online4yourmind
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Re: 48v Charger blown

I'm using one of those electric bike kits off ebay, dont know the model name or anything, just turns up in a cardboard box. I'm also in Australia, hence the over night replies..
It seems like I'm am heading towards bypassing the BMS as JLGRAU says, don't fancy burning out another battery charger, I'm back to primitive pedaling at the moment and its hard work and all those people who I'm usually flying past are probably laughing at me.. lol

Most people seem to have more joy when they manage their own battery or building there battery pack from scratch.. so maybe I'll look at that in the future.

ps JLGRAU, both fuses inside charger had not blown.. and I reckon both chargers are heading for the bin.. I've asked a few electricians and they run a mile from things like these..
As soon as my new charger comes I'll give it a go with the bypass instructions.

JLGRAU
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Re: 48v Charger blown

I have read that cell balancing is less of an issue with lower amp packs. If you had a 48 v 20 amp pack like me, the bms is more important as there are more cells.

colin9876
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Re: 48v Charger blown

If you go without the BMS you can still use the little wires coming out of the pack to measure the cell voltages. If you get them in order then putting your voltmeter on the nth, and the (n-1)th tiny wire will give you the voltage of the nth cell. For the First cell you use the 1st little wire and the Main Pack wire, For the last cell you use the last small wire and the other main pack wire)

If you remove the BMS completely you will just solder the connector on to the Main +ve and -ve coming out of the battery. That way you dont have the BMS affecting the output either!
If you do the other suggestion of just jumping clips onto the main wires for charge then the BMS will still be active on the discharge. (Pros and cons of this, supposedly it can offer some low cell protection, but if it was me Id remove it completely and just make sure I dont run the battery right down)

Balancing really isnt too much of a problem, as long as the cells arent charged too high, If your new 48v charger is a generic Lead Acid type one it will be good as it wont have a too high final voltage, and your cells will be around the 3.5-3.6v mark.

Look on the positive side of this, if you get it going without the BMS youll have better performance, and less wasted energy.
In my experience poor BMS systems have damaged more batteries than they've saved Lol!

online4yourmind
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Re: 48v Charger blown

Sounds like good advice.. I heard its not good to run the batteries down to nothing too much, I've got the throttle level lights to a tee now, so I know exactly how long left I have when it drops down to the red light..

The Charger I have coming is the same fast charger 5amp for lifepo4 batteries and I know it takes 1hr 40min to fully charge my battery plus I have a switch off timer so I can always use that when charging.

So do you think by removing the BMS and soldering the connections will work because I had a time when the connector on the bms was slightly off and the battery wouldn't re-charge, maybe because it was half connected. I think this sound more like what I want to too.. Reminds me of the car, first there was no ECU boxes and fixing problems was simple, now the more you add the more stuff to go wrong and complicated to fix.. So no BMS equals less to worry about.

I also read by having a pretty good battery charger is a plus and not one of these cheap ones from asia.. anyone know of any decent chargers with full protection?

colin9876
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Re: 48v Charger blown

A Cheap SLA charger can be just as good, really its the cut-off voltage that matters.
The SLA chargers generally have a slightly lower cut-off value than the specific Lifepo ones, and fractionally undercharging can be helpful when not using a BMS.

My 48v charger has a 57v cutoff - Gives an average cell value of 3.6v when used on a 16cell Lifepo4

When your charger arrives, use it to charge the pack (remove the BMS or jump it)
Post the final voltage of the pack here (while still connected to the charger)-Then we can do the Maths

online4yourmind
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Re: 48v Charger blown

Well the charger finally came after 2 weeks of waiting.. Removed the BMS, connected the battery and guess what.. there goes another battery charger, just went pow like the others.. so I've just decided to get down to the nity gritty, totally stripped the battery pack down to the individual cells, removing all the grey tape.. and remove all the little wire, they were probably the problem, then I've gone out to the local store and brought a 12v battery charger, divided my cells into 4, that gives me 12v each to charge, that will have to be my solution till I figure what ill do next.. all I need to know now is how long to charge each 12v pack for on a 2amp charger..

colin9876
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Re: 48v Charger blown

Sympathies for your problems with the charger.
Good idea to dissasemble and charge them in blocks of 4 for the time being, the 12v charger will terminate around 14v which will be fine for your cells (3.5v each)
You can always measure them as its charging if you are worried.

online4yourmind
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Re: 48v Charger blown

So far so good.. Its was only a cheap battery charger with no cut off, but has a green light to indicate when battery is full, but I use my multi meter to monitor the voltage upto 14v volts then I move onto the next group of cells.. I accidently fell asleep during one cell group charging and it measured 17v, which I guess is not a good thing.. is it worth burning off the excess voltage with a 12v bulb or something?
I have another 48v charger on its way so this is just a temporary solution anyway as I'm not planning on pedaling to work in these windy conditions..

I read your post elsewhere on this site and now I'm understanding more about what your balancingBus is all about, when I get a chance I will rig one up, but tell me, did you take wires from every single 3v cell or do you think I could do it from every 12v, just worried about how much wires I'll have floating around..

marylandbob
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Re: 48v Charger blown

Letting any 12 volt section of your 48 volt battery get to 17 volts is very dangerous! The cells might VENT, or even catch on FIRE, when pushed above 16.0 volts. Check to see if you see, of smell anything strange on or near that battery section.Discharging it down to 14.5 volts is probably a good idea, but I would NOT advise using that charger again, as consequences could be catastrophic, with a battery fire. Use a charger that will not exceed 15 volts, no matter what, and plug it into a TIMER, charge in a "FIRE SAFE" area, if you are going to forget it, or go to sleep!

Robert M. Curry

colin9876
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Re: 48v Charger blown

Yes use a bulb to discharge any of the cells that are higher that 3.6v, u were lucky that the 17v didnt do any damage! I suppose its time you had some luck lol!

Yes BalancingBus does require lots of wires and connectors, you could go in groups of 4 but then you would have to keep an eye on individual cells ocassionally.
The advantage with doing groups of 4 though is you could charge all the groups in parallel from one 12v charger.

Also as you have those fiddly cells it would save messing around doing lots of soldering on Tabs.

If you do ever move to new batteries I do recommend the headway cylindricals because they have screw ends that can be either screwed together, or put eyelet type connector round a screw you just twist in where-ever you want to connect, so no soldering required.

Through this hassle just think of it as a learning curve, its not a question of IF but WHEN these fiddly BMS packs go wrong, so dont feel its just you ...., we've all been there... (however I dont think Ive ever lost quite so many chargers as you in one month LOL!)

online4yourmind
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Re: 48v Charger blown

Lol.. yes its all a learning curve so I don't mind spending the money and if things go wrong from time to time, since I've had this wheel its been one thing after another, from front wheel falling out of the forks (fixed with touque arms) to near exploding batteries.. although the batteries seemed ok at 17v, no Smells or over heated or sizzling, but i guess i was just lucky its probably just a cheap battery charger it couldnt even get that right lol, but I was striaght down to kmart the next day and brought a mains cut off timer even though its only for this week till my 4th charger arrives which I paid express delivery from china.. I was thinking about charging in parallel with the 12v but I had plenty of time so I did them individualy..

I've already been looking at Headway cells, everyone seems to be using them, I saw a company in Australia selling them for $30 (without delivery) each 3v which I thought was a bit expensive as I saw they where around the $20 mark buying direct from the makers from some women called Lorraine in China with delivery, so that will be my next direction when its time too..

But so far so good, battery is on the bike running well at 56v ,the front lights seem a bit brighter than usual, but all good, so as soon as the red light shows on the meter it will be charging time, I remember when the BMS was on I got a few more Ks before it shut down the bike.. but I won't take any chances.. straight to the charger..

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