Rewiring 36V battery ti 12V?

[Pedrinho]

Hi there people!

I'm very fresh here and I realise that my post might not be entirely within subject of this forum but as i take same principals apply around EV vehicle words I'm looking for help here.

My question is: -Is it possible to rewire 36V bicycle battery for 12V? I don't have an exact specs of battery but supposed most of them are build the same way?




I'd like to have second use for my bike battery as an RV/Motorhome leisure battery. RV system is 12V. I know I could use some step down module, but this will introduce voltage conversion losses and primarily, phantom drain.

The way I would like to use it is to connect everything via regullar 36V socket on my bike for bike

and in camper via DIY 12V loom through external BMS.

Your thoughts gents and gals?

 

[Deleted member 4366]

No, it's not possible.

 

[Pedrinho]

No, it's not possible.

Thanks for your answear, are you 100% sure? Any chances you could throw some light on how those bank are made? What cell types and arrangments are those?

 

[VictoryV]

Hi there people!



My question is: -Is it possible to rewire 36V bicycle battery for 12V? I don't have an exact specs of battery but supposed most of them are build the same way?

View attachment 15442

try a dc to dc converter

example: http://www.powerstream.com/dc5g.htm

 

[Pedrinho]

try a dc to dc converter

example: http://www.powerstream.com/dc5g.htm

"Output Current 1.67A continuous, 3A peak"

that's one of the problems.

 

[D8ve]

No, it's not possible.

Technically it is possible, but practically it's so difficult that it's not worth it. A 12 volt system for your camper is simpler and cheaper.
You need the power for cycling.

 

[eHomer]

.......Is it possible to rewire 36V bicycle battery for 12V? I don't have an exact specs of battery but supposed most of them are build the same way?........

I asked a similar question on here a couple of years ago, where I wanted a 12 volt Lithium battery (Lipo or Ion) to power my 12 volt lightweight canoe motor.

d8veh was very helpful in explaining how to build a high amperage 4s Lipo pack, which I did, using six 4S 5000mah packs from Hobbyking.

I can appreciate the extreme impracticality of "rewiring" a 36v lithium pack so that it can be switched between 36volts and 12volts, because the cells would have to be reconfigured in banks of serial and parallel, and the built in "BMS" (battery management system) would somehow need to handle 12v and 36v low power cutoff and overcharging safety cutoff.

I'm amazed that there still appears to be no commercially available 12 volt lithium packs like those available for 24v, 36v, and 48v bikes.

I assume it would be perfectly feasible for a similar sized casing and weight (and price) to provide a 12v 30ah or12v 60ah with a dedicated 12v BMS and charger.

At the moment, canoeists and rubber dinghy owners with lightweight outboards have to use lead-acid and AGM batteries, which are so much heavier and short-lived, hence their complete demise on bikes.

I think there's a massive sales opportunity for bike sized Lithium battery packs in 12v.

 

[Deleted member 4366]

Thanks for your answear, are you 100% sure? Any chances you could throw some light on how those bank are made? What cell types and arrangments are those?

It's not impossible. Your battery is made up of 10 groups of cells (10S) all welded together with a 10S BMS wired to them. You can divide it into 3 x 3S + 1S. The 1S would be redundant. Here's how to do it:

• Cut the welds to separate the three groups
• Add connectors between them to swap between 10S and 3S
• Cut all the sense wires and add 3S connectors to each group
• Make an adapter harness to convert from three separate 3S balance connectors to a 10S balance.
• Make an adapter harness to convert the power wires from each 3S bank to one 10S
• Buy a 3S BMS capable of carrying enough current.

Each time you wanted to convert, you'd have to open up the box/case and muddle your way through a birds nest of wires and connectors. One mistake and it'll go bang. Let us know how you get on.

Here's a plan of your battery's wiring:

 

[eHomer]

I'm grateful to Pedrinho for waking up my interest in this subject again.

I've just been searching through Ebay and found a drop down buck that sounds perfect for my purpose, so I've started a new thread on it, to avoid hijacking Ped's thread any more...

 

[Pedrinho]

Yes, I'm 100% sure. A 36v ebike battery has 10 cell groups. They're welded together and controlled by a BMS that's wired to each group. Firstly, if you could cut the welded strips, 10 doesn't divide by 3. Secondly, you'd need a It's not impossible. Your battery is made up of 10 groups of cells (10S) all welded together with a 10S BMS wired to them. You can divide it into 3 x 3S + 1S. The 1S would be redundant. [...]

That's enough. Thanks a lot for taking the time to explaining this d8veh. I think I will be looking for dc step down route then same as eHomer.

 

[Fordulike]

That's enough. Thanks a lot for taking the time to explaining this d8veh. I think I will be looking for dc step down route then same as eHomer.

You could be guinea pig number 2

http://www.ebay.co.uk/itm/DROK-Waterproof-DC-DC-Buck-Converter-48V-to-12V-25A-Step-down-Volt-Regulator-C-/331934500980?hash=item4d48d68874:g:SHkAAOSwHoFXqlcL

 

[Pedrinho]

You could be guinea pig number 2

http://www.ebay.co.uk/itm/DROK-Waterproof-DC-DC-Buck-Converter-48V-to-12V-25A-Step-down-Volt-Regulator-C-/331934500980?hash=item4d48d68874:g:SHkAAOSwHoFXqlcL

Well I'll be going for it after cmoing back from hollidays in October, so hope for eHomer to report something back Ideally I will be looking for converter allowing greater currents

 

[Pedrinho]

Gday!

I'd like to dig out this subject from the grave and modify an idea a little bit. I'm still thinking focusing on limiting use of resources and reporpuse.

How about creating DIY (or semi DIY) modular 12V packs, to be used as either, paraller 3x12V for use to feed my camper (LED's, water pump, charging gadgets, etc.) or serial as 36V to feed bike motor?

I'm thinking about something with total capacity of 360 which equals usual large bike battery. As i need to be able to drop it to the backpack, taking with me anywerywhere but also mount it on bike. Hence we talking about 10Ah 12V packs.
What you guys think? Has anyone done something similar? Is it possible to find cells that could be also charged by sources designed for lead acid batterires (vehicle alternator and cheap solar PMW regulator)? If not I'm still interested in setup even if it means charging via dedicated charger.

Thanks

 

[Deleted member 4366]

Get yourself a DC/DC converter. You only need the 36v pack then:

http://www.ebay.co.uk/itm/200W-12V-15A-DC-DC-8-60V-to-1-36V-Buck-Converter-Voltage-Power-Step-down-Module-/182192158691?hash=item2a6b7fb7e3:g:l8QAAOSwZVlXsXtA

 

[IR772]

Or a multi-pole switch!

 

[IR772]

Read through this thread. It has what you are looking to do but with RC LiPo's which are more compact than Lead Acid.

http://www.pedelecs.co.uk/forum/threads/voltage-drop-down-converter-to-12v-on-bike-battery-pack.25470/page-3#post-332367

Hobbyking are a source of good quality inexpensive batteries and accessories

A multipole switch will easily give you 12 or 36 volts from a back pack type setup.

These batteries use the standard XT connectors that you could use for your camper equipment as well.