Re:How do I connect 2 LiFePO4 packs in Scooter?

[Battboy]

I won't go any further on this. it is getting redundant a bit now. Like I said earlier, each person can decide for themselves......
DH

Well, let me try to help the OP, Snowryder, and anyone else reading.

It is quite possible to parallel battery packs, but you need a few precautions. If they are separate packs you can't just connect them directly together; you need some kind of reverse current protection, but its relatively simple to achieve that. You can connect them through a selector switch, or through reverse protection diodes. Some BMSs may have the equivalent of diode protection built in, but you need to check.

Where it gets difficult is if you want to also charge them with a common connection. Generally this is not possible unless you disconnect the discharge path from each battery pack first. So the simple solution is to have separate charging connectors. You then need multiple chargers or you have to move one charger from pack to pack.

With the above approach, you are treating them as separate packs. It works very well with removable packs, and you then have the choice of using one, the other or both, each time you go out

Another approach is to effectively combine the packs into one, keep them permanently connected, and charge and discharge them together. This is a bit more complex and a lot depends on the BMSs in the packs. Also, you can only do it with packs of the same chemistry. Despite some questioning, I just couldn't work out from Don Harmon (Battboy) whether this is what his system does. I learned stuff about lion tamers and army generals and their excellent regard for customers but not what LifeBatt's electronics actually does.

Forgive me Don, but a lot of the time it sounded as if you were talking about series combinations rather than parallel.

HTH,

Nick

It's OK, Nick - You described the problem with Parallel Packs very well. Pertaining to an e-bike you are correct. You need to make those accommodations for the Parallel system.
It's OK to connect (2) Packs in Series without doing this. However, that being said I think what I was trying to explain is the function of the IM (Not the VMS boards inside each Pack). The IM comes into play if you want to connect strings of packs together using both Series & Parallel or any number of Packs (above 2).

It then becomes the Master BMS for the entire system and protects said system from OVC / LVC and functions as a Cell Balancer as well. You can charge the entire system without disconnecting any individual Packs. Configurations can be all Parallel, all Series, or Series / Parallel up to 100 individual Packs. I know, this is mainly an e-bike forum, but some here are interested in learning more about larger systems.

View attachment New IM - Integration Module.jpg

Hope this helps clear things up? As for the colorful military references - those came from the circuit board Designer himself

Don Harmon

 

[snowryder]

Mr. Kang, Tiberius, Battboy and ALL,

So, this seems to be my current scheme to not disassemble the battery packs -

1) I purchased a Blue Sea Systems 48V 4 position(off; bank 1; bank 2 & banks 1 & 2 combined) battery switch(#6007) from ebay - check specs. at: www.bluesea.com/category/1/products/6007

2) a) I think I will connect the scooter battery(17ah) with a 14AWG C13 female to C14 male IEC 320 SJT 15A connector cord, to the seat box to manually plug/unplug into the controller/hubmotor power plug for emergency power only!!
b) And hook the the 2 separate 20ah battery packs to separate posts(banks 1 and then bank 2) of the switch. Switching from the 1st 20ah pack to 2nd pack or combining packs with the switch? Is that correct??? I will connect one set of anderson 45amp powerpole connectors to each of the two 20ah packs so, I can disconnect if needed. I think I will need to connect the positive discharge lead from 20ah pack #1 to the battery Switch bank #1 and the 20ah pack #2 to the battery switch bank #2 and the switches positive output lead to the hubmotor/controllers power input cable? Then I have to run the hubmotor/controller negative output wire back to the negative battery packs discharge wires(never bringing the negative wires to the switch) completing the circuit? Is that correct?? Can I connect both 20ah battery packs negative discharge wires to each other by twisting them into a Y connection and inserting that twisted double wire into a 45amp anderson powerpole connector and connect that to an anderson powerpole connector on the negative output wire coming from the hubmotor/controller ? If I turn one bank off, the power shouldn't be able to backup into the low battery because the circuit is closed(or do I need schottky diodes on the negative battery discharge wires?) and I should be able to charge the low battery thru the packs own charging terminal and BMS because the bank is closed to the motor while running the scooter off the full battery pack on the switches other bank #2 ? Correct? And if I combine the two banks on the battery switch the circuit should continue back to both battery packs to complete the circuit? Is that Correct????
c) They(Blue Sea) also say I could connect more than one positive(from different batt banks) to one post of the switch to combine more than two battery banks in parallel but, I may need the bigger model # 3002 or 3003 switch!!!
Thanks - What do you Think???

This is what Blue Sea Systems e-mailed me:

Dear Mr. DeFelice,



I believe I am the person you spoke with on the telephone this morning.



What I actually suggested to you was the possibility of permanently paralleling the batteries together to increase overall capacity without changing anything else in the system. This means not using any kind of battery switch because one would not be necessary unless you only want them parallel some of the time. If you goal is only to get extra capacity I do not know why you would only want it some of the time, but it is not my scooter.

What we can't help you with are any battery issues specifically related to your scooter's electrical system because as Erin pointed out we are not experts on your scooter or the type of batteries it uses.

The wiring diagram supplied with part number 3002 and 3003 is below (also available on our web site):

This diagram does not address the battery negatives because they are not connected to the switch in any way. For your understanding the "1 + 2" parallel position on the battery switch will only work if your battery negatives are already connected to each other. If you wanted to show the negatives connected together in the above diagram all you would have to do is draw an uninteruppted solid line connecting the negative post of the battery on the left to the negative post of the battery on the right. ******* This connection would not touch the battery switch in any way on the diagram.

******* I(snowryder) think he left out connecting the negatives from the batteries to the hubmotor/controller or it won't complete the circuit!********


Best Regards,



Terry Golombek

Customer Support

TEL: 360-738-8230, ext. 117

TOLL FREE: 800-222-7617

FAX: 360-734-4195

EMAIL: tgolombek@bluesea.com

WEB: www.bluesea.com



Confidentiality Notice:

"The information contained in this message may be privileged, confidential, and protected from disclosure. If you are not the intended recipient, or an employee, or agent responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately by replying to the message and deleting from your computer. “



Unfortunately, the diagrams didn't copy onto this forum!!!!!(snowryder) HELP ME Thanks Guys!!!!

 

[maydaverave]

Interesting vehicle. The extreme scooter website says its 52 volts 40 amps at 500 watts and 20mph top speed? somethings not right here What kind of top speed do you get and any idea of how many watts your pulling?

 

[Tiberius]

Mr. Kang, Tiberius, Battboy and ALL,

So, this seems to be my current scheme to not disassemble the battery packs -

1) I purchased a Blue Sea Systems 48V 4 position(off; bank 1; bank 2 & banks 1 & 2 combined) battery switch(#6007) from ebay - check specs. at: http://www.bluesea.com/category/1/products/6007

The problem with this is position 1+2 on the switch. It sounds like that directly connects the batteries together. I know boat and RV people with wet lead acid batteries seem to do this, but I really don't like it with other types for the reasons explained above (large cross currents if the batteries are different states of charge).

So, if you are going to use position 1+2, you should have diodes in the circuit.

How are you charging? If its a separate charger for each battery that's ok. Also ok is moving one charger from battery to battery. If you want to try using one charger on two batteries simultaneously, then it can be done if you know what you're doing, but you will probably have to disconnect the batteries from the scooter.

Nick

 

[tycreek]

I started with dual battery switch 1, 2, 1+2 but ended up with smaller toggle switches and a diode harness to tie 2 packs together in parallel.
First harness was with some 75A blocking diodes from a solar supply place and they seemed to work fine.

Then tried Tiberius's Ideal Diodes and they work a bit better and this is now my preferred parallel connector choice.

Good luck with however you decide to connect.

 

[snowryder]

Interesting vehicle. The extreme scooter website says its 52 volts 40 amps at 500 watts and 20mph top speed? somethings not right here What kind of top speed do you get and any idea of how many watts your pulling?

Where on the x-treme web site do you see 52V at 500 Watts? The specs are 48V with a max 40amp draw and the load is a 700 Watt hubmotor unless you are in Canada, then it is a 500 watt motor. I get 30 - 33 miles per full charge in the hill climbing capital of the Rockie Mountains. I cruise flats at 19 -21 mph, uphill it slws down depending on incline and length - alittle better than the XB-600 (SLA), (when I installed my 48V 20ah LiFePo4 to the XB-600 it went up hills at 21mph and 24 on flats) but, not as good as I want. So, I think the 700Li has a controller that is prepared for the LiFePo4 batt and controls any extra demand. I will know more after the Memorial WE is over, then I will install the 2 extra packs and switch? Thanks!

 

[snowryder]

Thanks tiberius and tycreek,

tiberius,
I will be charging the batt packs separately, now. I was thinking about combining my 2 spare 20ah(my second spare LiFePo4 pack just showed up and it is 2" higher than the first LiFePo4 pack and ways 4 -5 lbs. more than most other 20ah packs on ebay- maybe it is really 24-25ah?) packs into one 40ah so, I could charge it from one charger but, changed my mind because of all the great posts(convenience of removing any pack I don't need). I now am planning on hooking the positive wire of the scooter's 48V 17ah LiFePo4 pack to dual batt switch post #1 and one 48V 20ah LiFePo4 packs positive wire to batt switch post #2 and only recharge the pack that is turned off or both separately if they are turned to switch position OFF. I won't use the 1 + 2 position until I get a set of schottky diodes on the battery lead wires. And the third pack will be connected manually when needed only when I manually disconnect the switches' output and then connect the third pack. That way I won't have to carry all 3 packs when I don't need them.

tycreek,
Why did you change your mind on the dual battery switch? Is that setup 2 diodes or 4 diodes hooked together to combine 2 packs in parallel?

 

[tycreek]

tycreek,
Why did you change your mind on the dual battery switch? Is that setup 2 diodes or 4 diodes hooked together to combine 2 packs in parallel?

The battery switcher I had just didn't fit well anywhere and I wasn't willing to be creative enough to make a good mounting spot. Two 50A toggles work fine for me so far...

Yes, that's 4 diodes for 2 packs in parallel. The 2 ideal diodes per pack might be overkill but my thought was double up vs. trying to somehow fit heatsinks to handle 50A. Now in hindsight my constant current needs of say 30A would probably be fine with one per pack. Though, I do know this config works without getting hot on my bike when I run my 2 packs.

 

[new2thiss]

I have the same setup i did for my friend. It had 2 LifePO4 packs 48V/20Ah just like yours

instead of connecting it parallel together i decided to make a switch to choose between packs.
this to prevent any charge / discharge between the two packs together.

i found it more safe to do it this way. I used two 200Amp switches which normally used for incar audio amplifiers.

What did that switch look like? Can u show me one?I like this idea

 

[dnmun]

if you have two identical lifepo4 packs and wanna combine them in parallel you could join them together at the terminals, B+ and B- and connect the sense wires of the two packs together by soldering a connector wire between the two sets of cells. then you can use a single BMS to balance and protect it and have the maximum capacity. even reuse one of the BMS if you don't need higher current capacity from the BMS.

it is better to take power off of all of the available packs to keep the discharge rate lowest. and best to use the power from full charge, not from partially discharged. always wait to charge before use and then charge to full charge. long enuff to balance it.

 

[new2thiss]

if you have two identical lifepo4 packs and wanna combine them in parallel you could join them together at the terminals, B+ and B- and connect the sense wires of the two packs together by soldering a connector wire between the two sets of cells. then you can use a single BMS to balance and protect it and have the maximum capacity. even reuse one of the BMS if you don't need higher current capacity from the BMS.

it is better to take power off of all of the available packs to keep the discharge rate lowest. and best to use the power from full charge, not from partially discharged. always wait to charge before use and then charge to full charge. long enuff to balance it.

I'm sure you're already being quite specific but I'm not sure what you mean. What is b+ and b - and solder a connection where? I'm not so savvy with modifying batteries. I've modified my bike but batteries I don't know much about do you have any pics, or examples you can show me? I'm effectively contemplating having two duct tape lifepo4 battery packs in parallel, or being able to switch from a dead one to a fully charged one. I like the second idea better as I hope to be able to remove one and charge it, while still having the exact same still available and then remove that o e and charge it thereafter. How would I do this?

 

[dogman dan]

Once you expose the bms, you should see markings on the board where the bigger wires solder on, such as B+ and B-

To run one bms, then the smaller wires from each battery will have to be combined into one. So on that 16 or 17 wire plug, the same first wire on battery a connected to the first wire on battery b, then the second one, etc.

In other words, parallel connect all those small battery balancing wires into one plug without mixing them up.

This is instructions for connecting in parallel. I thought you wanted to connect in series?