battery and charger problems

[Kiwi Biker]

Hi everyone, I'm a newbie here, names Bruce and I'm from New Zealand. I've had my Magic Pie3 1000w LIFePO4 48V 10ah for nearly 2 years with miner cosmetic issues and a controller replaced under warranty. The bike was outside and got drenched in a heavy down pour, I have put a DMM on the input charging side of the battery and it reads 49.0V, on the output to the motor it reads 41.3V.
I have pulled the battery apart and measured the 16 separately and they are reading 3.3 to 3.4V, can I assume the battery is OK and the BMS is at fault and needs replacing, or are there other tests I should do with the DMM. The other problem is the charger, when I switch it on it makes a click noise like a solenoid, the fan doesn't work, and the red and green light come on instantly. The charger came with the GM kit set,
Model:Li150-48AL, Input:110/220VAC 60/50Hz 3/1.5A, Output:58.4VDC/3A and it still puts out 57.8V on the DMM. What are your thoughts on the charger, try and get it fixed or buy a new one? The charger only started doing this after the bike got wet, as I bring the bike inside the house each night and put it on charge till the next morning.
I look forward to you comments on these issues, attached is a photo of the bike. Photo of bike.

Regards,
Bruce. 

[Bikemad]

Hi Bruce,

It sounds like the BMS has been affected by the rainwater, which can often affect both the charging and the voltage output.
If it has dried out completely and still does not work as it should, then it might need to be replaced.

I have the same charger and mine has an output of 58.1V when disconnected from the battery, but goes slightly higher while charging, so I don't think your charger is the problem.
Mine also does the same as yours if I turn it on without it being plugged into the battery (it makes a click noise like a solenoid, the fan doesn't work, and the red and green light come on instantly).

I suggest you also check the voltage across the switch contacts inside the battery end cover (while it is turned on and connected to the controller) to see if there is any voltage drop across the contacts, as the contacts can sometimes cause problems too. 

Alan
 

[Kiwi Biker]

Thanks Bikemad, Can I replace this faulty BMS with this one on eBay: sorry about the copy and paste.     http://www.ebay.com/itm/Battery-Protection-BMS-PCB-Board-for-16-Packs-48V-LiFePO4-Cell-max-15A-w-Balance-/251567009257?hash=item3a928fede9:g:BPYAAOSwBadTpu9k

If I can replace it with this one, will my battery charger be OK to charge it, or what charger will I need to recharge it with. I did a accurate reading on the 16 cells and five were 3.47V, seven were 3.31 and four at 3.45, will the new BMS installed level out the cells, or do I have to do that manually, thanks again for your help.

[Bikemad]

Hi Bruce, that BMS only has a maximum output of 15 Amps which is too low for the Magic Pie.

I would be tempted to try one of these instead:


Click for more details

They can supply twice the current and are only half the price, and I think the balance lead connector plug will be the same as your existing one.

Check the exact measurements of your existing BMS board to see if this one will fit. It looks as if it could be reduced slightly in length if necessary without interfering with the tracks on the board.

My only real concern with this BMS is that the balance voltage per cell is shown as 3.5V (± 0.03V) instead of the typical 3.65V. I don't know whether this is simply a misprint, or whether the LiFePO₄ cells are now being charged to a lower maximum voltage in order to increase their life expectancy.
If this is the case, you should be able to reduce the output of your charger by placing four 10A diodes in series between the charging socket and the charger connection on the BMS board to drop the charger's output voltage from 58.4V (3.65V/cell) to 56V (3.5V/Cell).

I would try to manually balance the cells as much as possible with the aid of a 12V 60W headlamp bulb placed across each of the higher voltage cells (one at a time) to bring their voltage down. It shouldn't take too long until it matches the voltage of the lowest voltage cell, but you will need to recheck the cell voltage after the bulb has been disconnected for a few minutes as the cell voltage will rise when the load is removed.

The BMS would probably take a long time to balance the cells with its inbuilt 80mA load compared to the ~2600mA load of a 12V 60W bulb.
I have several H4 bulbs which were replaced with new ones when the dip filament failed that I have kept specifically for this purpose, instead of throwing them away. 

Alan
 

[Kiwi Biker]

Thanks Alan,
I was thinking of buying this,   
http://www.ebay.com/itm/221876225660?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT 
as I never thought of bringing all the cells down to the lowest voltage, and I do have bulbs.
I measured up that BMS, and wires will be torn putting it back in the casing, what a bummer. My measurements are 130mm x 65mm flush with about 1mm spacing for the casing.
My options at the moment are buy a 10A BMS from my GM dealership for $75.00 and wait 6 to 8 weeks for it arrive. $200.00 shipped from Canada, I've e-mailed GM in China and will hear from them sometime. There isn't a lot on e-bay to choose from, or should I say to fit.
I'm wondering whether to fix this one in due course with the right price, and buy another battery kit set, LiFePO4 48V 30A battery, charger and mounting plate. I hear you get more distance with a 30A battery, but for every + there is a - What do I loose, top speed, acceleration or torque? I can't a ford to loose torque for the hills, as my hip won't let me peddle.
When I first started looking for the problem, I followed some threads and checked the 3 phase wires, then put 3 AA batteries in series to check the hall sensors, they seemed to work one day and not the next, I ordered a pkt of 20 ss41 bipolar hall sensors from China, are they generally any good or should I have dealt with Digi-key?
Thanks again for all your input.

Bruce.

[Bikemad]

Hi Bruce,

I have just had a look inside my GM battery and I'm pretty sure that BMS could be made to fit inside without too much hassle.

Here is my existing BMS in the end of the battery:



And here are the dimensions of the battery casing:



This is how the suggested BMS should fit, but you would need to file a slot at the edge of the board to allow the balance leads (and the red wire going to the charging connector) to fit between the BMS board and the battery casing:



The 16 pin socket could probably be bent up slightly away from the circuit board to allow a bit more clearance for the balance connector plug and wires, but I don't know whether the existing balance leads will be long enough to allow the connector to actually reach the socket.

It might even be possible to resolder the balance lead connector on the opposite side of the board to allow the balance wire connector plug to push straight in without the battery case getting in the way of the wires:



If it were my battery, I would definitely get that BMS to fit one way or another! 

If you are thinking about getting a 30Ah battery to replace your existing 10Ah battery then the only disadvantages will be weight, size and cost.
Top speed and torque should be the same (or possibly slightly higher) but the acceleration may be very slightly reduced by the additional weight of the battery.

Those Chinese ss41 Hall Sensors will hopefully work fine, but you will have plenty of spare ones just in case they don't. 

Alan
 

[Kiwi Biker]

Hi Alan,

Thank you for you help and advise, I have gone ahead and purchased the BMS board and also those 10A diodes for the charger. I feel confident that I can make it fit after reading how your make the board work for you when fitting it, and I don't have to wait weeks to get a BMS.
 
Bruce.