Wiring lithium packs together?

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lbz5mc12
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Wiring lithium packs together?

I originally posted this in a different forum but this one seems more along the line of my query. My question is this, could two separate, already assembled, in their own cases lithium packs be wired together to run in series or parallel? Basically what I want to do is run both power connections from the packs into some kind of "Y" adapter into the single power connection on the controller. This way I could either use them at the same time for more power or individually for more range. My main concern would be any kind of electrical feedback between the batteries which could result in shorting them out. If this is possible, can anyone in here recommend a controller with a wide range from 36 to 72 volts? This is a concern due to some controllers having low voltage cutoff. The batteries will be a silverfish style pack from an LX1 bike (36V 10Ah) and a little frog style pack (39V 8Ah). I found the 39V battery on Dhgate for around $221.00 free shipping if anyone is interested. Just type in 39V 8Ah in their search and it should be the only item that pops up. I was amazed by the low price on the pack so I'm hoping it's not a piece of crap. Any help, "either positive or negative", would be appreciated. Little pun there.

Don Harmon
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Re: Wiring lithium packs together?

You have to choose. If you wire (2) 36V Packs in Series you would get a 72V output. If you wired (2) 36V Packs in Parallel you would get 36V output. If I understand your question that you want to be able to have both a 72V & 36V output simultaneously the answer is NO. It is possible however to use a Y connector between (2) 36V pannier Packs for example that would let you use one Pack at a time but your output would still be 36V. I believe this is correct advice unless someone else knows a way to do what I think you want?

lbz5mc12
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Re: Wiring lithium packs together?

That's what I was worried about. What I basically want to do is use the existing power cable plugs, you know the three prong power connection, and run both of their connectors into an adapter into a single two prong connection into the motor controller. Or I could just splice something together. Both the batteries will have key starts so that shouldn't be a problem. Thanks for the feedback.

IBScootn
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Re: Wiring lithium packs together?

Check out page 5 of 6 on the following link on how to use diodes when wiring packs in series or parallel.

http://www.pingbattery.com/usrguide/Wiring%20Guide%20V2.5.pdf

Good luck

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robert93
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Re: Wiring lithium packs together?

Wow, where to begin... The battery packs, When you connect two batteries for any configuration, they cannot safely be used if dissimilar ratings are involved. Either Voltage, or Amperage and drain type have to be matched, and depending on the style of connection, all must be matched. If parallel, the voltage has to be "identical", not "close" even then, varying amperages will result in poor performance in parallel. One pack would do all the work and the other would still have room to go, if properly isolated, but still would lead to premature failure of at least one of the packs. In Series, where the voltage would be addative, voltages could vary, but, Amphour rating would have to be identical, or one pack would flash charge the other, and fry them both. NEVER mix battery chemistries, no matter what. The discharge characteristics of both have to be the same. The safest way to use dissimilar packs is one at a time, and even then only if they meet the design specs for the controller and motor. The next level of complication is the Battery Management Systems might balk at all of these configurations, and leave you with a firey mess. Lithium battery explosions are not pretty. Voltages and Amperages of the level needed to drive these bikes WILL kill you if mishandled. Best of luck, but do tons of homework first.

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