Diodes and connections questions

[avsmith66]

What size diodes are people using between battery packs when running in series. I have a 48v10ah and a 24v10ah LIFEPO4 on the way that I want to run in series for 72v and will be drawing 30-40 amps. When connecting the batteries together, should the diodes be on the positive side or the negative side?

Should I bypass the BMS on the batteries for discharge since my controller has an LVC setting and I am also running a CA and if so, would that eliminate the need for diodes between the batteries? . . .

AVS

 

[fechter]

It doesn't matter which side of the pack you put the diode as long as the polarity is right.

The CA and LVC in the controller only look at the full pack voltage, not individual cell voltages. Don't bypass the BMS on discharge.

Here's a diode that should work. There are probably cheaper ones if you look around:
http://www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMtEwUVCuofpuCZMqWOhwR1snv5s32nsIKE=

Here's the general configuration (see last post):http://endless-sphere.com/forums/viewtopic.php?f=16&t=1312

 

[avsmith66]

So I really only need the diodes to protect one bms pack from another of higher voltage in the series?

If connecting a 48v20ah LifePO4 and 24vSLA, would a diode be necessary? Since the BMS is on the 48v pack and is rated to handle that much, if it were to trip, then the most the 24v pack could run through it would be 24v, correct?


Would this also mean that if running a 48v LifePO4 and a 24v LifePO4 in series, the 24v LifePO4 BMS is the only one that needs to be protected, therefore no diode is needed on the 48v LifePo4 pack, I just need to put one diode across the 24v pack?

AVS