12vlts from a 16s?

[Upnorth]

Would it be possible to use a 16s LifePo4 pack as BOTH 52vlts and 12.8 vlts?

If I connect leads in a way that would essentially connect the pack as 16s x1p and 4s x4p could the hard wiring remains the same and I could have two power leads, one for 12vltS and one for 52vlts?

I think it will work, IF I run a BMS it could get tricky.....

[73Eldo]

The problem would be keeping the cells in balance. The 12v load would discharge that group faster than the rest and imbalance between cells in a multi cell system just isn't good. Its not going to blow up or anything but its going to be hard on the cells which will reduce their range and likely overall lifespan.

How much 12v power do you need and for what?

[Upnorth]

I agree, using just 4 of the 16 parallel groups would be a poor plan.
what I was thinking is to “tap” off all of the parallel groups so that they are all used.
essentially turning a 16s5p into a 4s20p I think it may be possible, without changing any of the nickel strips.

I have order 120 K2 lifepo4 cells, nominal 3.2volts, 3800mah.

Main purpose for the pack is for a BBSHD. In 16s I can boost it up close to the stock controller max of 60vlts, mostly though I’ll keep it at 58, it seems to like that voltage from my now dead WOLF, RIP

[Upnorth]

Post cut me off.....
I wanted to add that having a 12vlt 76ah 60amp battery to power an inverted would sure come in handy in our frequent winter storm power outages.

I’m building it my self so I might as well wring out everything I can.

this stuff isn’t cheap and keeping a few lights on in a storm would win me some points with the Misses.

[73Eldo]

The idea came up not that long ago here and someone posted links to some inverters that could run at least off a 48 but seems like maybe someone did it with a dire wolf.

[Upnorth]

*******DISCLAIMER*******
i am NOT an electrician. Do NOT attempt! I am just kicking ideas around right now.

I think that diodes are required. Because the cells are hard wired in series already there is a voltage difference between the “+” terminals...... see the hand scribbled diagram.

this likely won’t work as the diodes probably need to be in between the hard wired series connections not just the leads to the desired 12vlt side....... putting the diodes there would remove the 60vlt series power.....

I have a feeling I have just enough knowledge to really mess things up. Good thing we have forums!!!

[73Eldo]

Its too late at night for my brain to try and process your drawing. Since you need a new pack anyway how about building up a dual 24v system? I know 24 volt inverters are common so that covers your inverter use then stick them in series for the bike at 48v? Or see if 36v inverters are easier to find than 48-60? Then do dual 36's and get a Ludi V2 or Phase runner that can handle the 72v?

[Upnorth]

That likely is the best plan.
i have seen packs online meant to be “stacked” together to get the desired voltage. Far simpler, far safer.
Grin has “Ligo” packs......

Would be cool to have a plug for 12vlt and a plug for 60vlt in a tidy package. Could run lights and chargers, regular automotive stuff.

But it would also be cool to not burn the house down, or destroy a couple hundred dollars in cells.....

I know DC current control devices get big and expensive fast as amps and voltages increase....... hence the fact that IF there is a 60vlt inverter it’s higher price would likely more than cover the cost of dedicated 12vlt packs......

I‘m longing for the day’s when I had a nice working sealed up pack. But I just can’t stomach dropping $700cdn for a pack I can only expect 200cycles from.

Please help me cut off the rabbit trails!!
I just need to weld up the 16s pack and get on the bike!!

[AZguy]

What you are describing can't be done without active switching elements between the 12V groups, diodes won't do it. It's very non-trivial and you must cut the strips between the 12V groups. While it could be done with several passive switching elements (i.e. physical switches) that would be very dangerous as they would have to be switched in the proper order or catastrophic consequences could result.

The proper way to do this is with solid-state relays (or opto-driven back-to-back MOSFET's which is the usual approach in large commercial batteries that cell/group isolate, etc.) and a "smart" circuit or microcontroller to sequence them

[Upnorth]

I figured as much, if it was easy and safe it would likely be an option on many batteries.
Thanks for the responses, I’ll leave this alone now...

[K442]

The most simple method would probably be the DC DC converter. If it were me, I would probably configure the battery for what ever I expect to draw the most power, or if you have one use case where you want the battery to be the most simple/efficient configuration. Then get a DC DC converter for the other side. For example, if you want to run your hairdryer at 52V and a couple of LEDs at 12V, then configure the battery for 52V and get one of these: https://www.ebay.com/itm/113136860406 (or similar) or in the alternate case, 12V battery and a 52V converter. https://www.ebay.com/itm/123149199164 (or similar) You may also run into some adjustable converters covering nearly the whole range Going from lower volt battery to higher output is called a 'boost' or 'step up' converter, higher volt batter to lower output is a buck or 'step down' converter if you want some added search key words.