BalacingBus (no BMS), Positive feedback
I had been using a Lifepo4 pack with no BMS, just occasional cell monitoring and manual topping up if required.
All was ok, but I want to report that this new method with the Self BalancingBus is easier.
I took all the batteries and wired them to a block of Powerplugs.
These are connected to a SeriesBus for charging and driving
and I connect the BalancingBus when Im not using the scooter. This has all the +ves and -ves connected in parallel and levels the cells
I can feedback that its keeping the cells in the pack at similar voltage without any other intervention - Dont know why I didnt think of it before!
Nice idea, simple when there are only a few cells.
You could also achieve even better balancing if yo use a charger designed for a single cell, but charge with the balancing bus in place. The balancing bus could be the charger connector.
a powersupply like this:
when connecting in parallel you should not use a simple wire but put some current limiting resistor
If you have a cell a little lower than others this cell when you do the parallel connection get brutally charged from the other cells without a current limit and can be damaged.
Paralleling is a good strategy to balance a small pack and save the money of BMS but you still need to do it in a proper way
For example if you do a parallel between a cell charged at 3.3 and another charged to 3.4 you can have current up to 10A-20A flowing between the batteries
One option is to do a balance before and after charging so you can reduce the imbalance.
In your case paralleling is very easy , you can consider paralleling every time the battery is not in use.
Hi Colin, although I don't have any problems with batteries out of balance so far, I am considering applying your solution for the future. Indeed, you even don't have to charge the batteries in parallel configuration: just a balancing period ofter serial charging will do the job. However I have a few practical questions: while driving, the current can be high, the current during balancing is limited.
I have 4 12V 38 AH SLA-gel Greensaver batteries. My HUB motor has 1500W. Did you use the 15A, 30A or the 45A contacts? I am planning to use the 45A for connections to the batteries and for the SerieBus and 15A for the BalancingBus. The wires for the SerieBus seem a little thin, what is s their Gauge. What current will they be able to take?
And one last question: is it easy to plugg and unplugg the connectors, it needs to be done almost every day? Do they not get unplugged while driving?
I would like to follow your method for my 16cell 48v 12a headway battery pack. I'm guessing that i need 16 pair of andersons for series connection...running and charging. 16 pairs in paralell for balancing.
Would this be correct? Any advice or recomendations would be truely appreciated...
My 1st bms has cost me 6 dead cells....I'm not going the game this way any more.....
Thank you for your quick reply.....I'm forced to stick to a set battery arrangment....I custom made my bicycle to take the battery pack in this particular way, I hope that the photo's make this clear....I can purchase 5 pair of anderson's for $7.00 aussie...I have emailed the supplier to see if this price still stands...I am thinking that with a block of 16 pairs, I might be able to fiberglass the connectors into a ridgid block eg 150mm long by 25mm wide....If this is the compromise that I have to make to follow your wonderful method,then so be it.
I just recieved an email from the anderson supplier....I've ordered 50 pairs @ $65.00 aussie delivered to my front door...I ordered the large number because I will make mistakes and I would like some spairs at the end of the day.Now I've just got to get the crimper...
Thank you for the reply....yes,I did make the battery housing....I used 40mm dia pvc tube from the local plumbing supplier,I found that there was 2 types available...a loose fitting and a snug fitting, there appears to be a slight difference between manufacturers pvc tubes.I went for the snug fitting sized tube.
I contact glued the 16 tubes into the shape...I filled the outside valley's of tube pack with expanding foam...sanded the foam back to the level of the tubes...then fiberglassed the outside of pack with course matting....pack width is 83mm...narrow and strong.
in to the bottom end of each tube I gluded a 5mm wide pvc ring..this acted as a stop for each cell,I could now drop each cell into it's tube...I made a fiberglass strip 2mm thick, same length and width as pack with 16-20mm holes,this was gluded to the bottom of pack...with this in place the end of cells terminal was at the same level as the pack.
The pack is connected in series with terminal 1-neg at rear end of pack,right hand side +,-,+,-,to cell 8,front of pack...across to cell 9,left hand side now +,-,+,- down to cell 16-pos at rear end of pack.cells 1 and 16 are output and input terminals.I use the flat metal busbars that come with the headway cells.I had to elogate each hole 3mm to fit....GEE I hope this makes sense....
Do you have any photo's of your battery pack all wired up and connectors in place? Please excuse me but my little brain is having trouble seeing the full picture...Is your pack wired up in series to the permanent block and stays put, for running and series charging?.... and the removable block is in paralell for balancing and/or paralell charging?...please set me straight if I have this wrong
Thank you for the kind offer...I actualy ordered 4 more cells last night...hopefully I'll have them in a fortnight...I'll use 3 and have 1 spare....By following your bms free method I hope that I can get a good run out of my batteries this time....Do you run a low voltage alarm or something of that nature?...Or do you know the limits of your pack through experience?
Thank you for the reply and photo,..Things are alot clearer now that I've had a few days to digest the info and reread your posts many times....I'm sure that I can wire my pack into groups of 4 as per your recommendation..I'll have my andersons' in the next couple of days and I can play and do some trial fit-ups to see how things look in the real world...I will need to make a new top cover for the battery pack...
When I was reading up about bms's I came across many examples of over charging of individual cells...that didn't help me,I was having the opposite problem - the discharging of cells to death...I came away with the impression that maybe 50% of users had problems with the bms that led to damaged cells...many gave up headways and went to lipo to avoid the bms issues.
I inclued 2 photo's of my pack..one showing the bottom with the fibreglass strip with 16 holes@ 20mm dia....The other photo showing cells in place,no busbars in place....I believe this is what you mean when you say 1up,1down,ect,ect?...
Man you must be psychic...Battery chargers was the next thing that I wanted to ask you about...I have a quality 12v 6a charger that I used for charging 12v 80ah agm batteries,I'll start with this to get the ball rolling.
I'll definitely take you up on the single cell charger offer...I'll PM you in the next day or two with my details..Thank you very much for this offer.
My next question is wire guage...my cells are 12a...the andersons are 15a...controller 15-20amp[ it handles the 48v-12a battery pack no problems ]...I am thinking 15a wire from the local auto parts shop...
Any advice would be much appreciated...
Thanks for pointing out amps and amphour...I'm at the bottom of the learning curve and have a long way to go with the technicalities and terminologies of the 'E'world...I'm a fitter and machinist by trade.
The rear hub motor that I'm running is rated at 400watts...My set up is what I consider an entry level arrangment...I wanted to learn and make my mistakes with this kit which only cost $400.,before moving up the scale with power and costs...got to walk before I can run.
Your right about the anderson's, They are fiddley buggers and that was the reason I got extra's...another learning curve,LOL...
Hopefuly you got my PM.
I will be using the same crimping eyelet as per your photo..their cheap and easily available from local auto parts shop...I'm very conscious and watchfull of polarity...I have a white paint pen with which I mark 3 + around the outside of the positive end of each cell....the same thing 3 - at the negitive end...the markings stick out like dogs balls...
If the single cell charger is unmarked I will colour the positive lead red.....so everything should be very clear and idiot proof...
What voltage will the single cell charger stop at 3.6v or 3.7v or more?....What voltage do you charge to?
After you have charged the cells do you connect the cells in paralell to balance out any slight differances?
the +ve and -ve of the original pack was connected together with the flat metal busbars that came with the headway cells..
There's a supplier in Australia who is testing out some 25A single cell chargers which will cost about $200 ... still a bit expensive but I'm assuming you wouldn't need to monitor the batteries whilst charging. Otherwise there are some cheap 10A ones on eBay.