Extend battery with 94 cels lipo4

[Eduard48]

Greetings from Romania ! I have recently owned a sh phev 2014 and look for a alternative to increase the capacity of the battery,range and at the same time not to damage something or take risks.
Searching the internet I didn't find anything conclusive , someone in Austria use same 300v the battery and show picture can be increased with another battery in paralel cut some wires from the rear inverter and put a 2 sec delay contactor and some diode , not sound so complicated but my question is if anyone has seen something like this, is it real?

l will try to building 93/94 cels lipo4 (car have liion main bat.296v) , need some wires , 2 contactors one diode and bms for all cels , in that moment l have 64 cels /90ah lipo4 use my home fotovoltaic system and l need to buy more 2 series 16 cells (32 pcs ) for that test

If anyone wants to share other ideas talk here , thank you !

 

[nrayanov]

What would be the purpose of this very risky and expensive experiment?

 

[AndyInOz]

Hmm... This reminds me, we never did hear back from the guy that was going to stick solar panels to his car.

He was very unhappy with the responses from the forum if I remember correctly.

 

[kpetrov]

The question is... will the vehicle BMU figure out what is going on and how will manage it.
Charging the additional battery with this setup seems questionable as well.

 

[HeliNurse]

Surely adding weight is going to adversly affect range?

 

[kpetrov]

Surely adding weight is going to adversly affect range?

Sure but that's like saying filling up with gas will adversely affect range while in fact will extend it.
It will increase the power used to travel an unit of distance but total range will be extended.

 

[BobK]

Except the fuel level (and weight) decrease as you drive. Batteries stay at their maximum weight.

 

[HeliNurse]

I would have though a range extending trailer would be a better option, I note that the new Cybertrucks, long range pack takes up 50% of the load space, so you can go further but carry less?

 

[Stevepl11]

As long as the extra battery has it's own BMU built in and operates within the same voltage range I don't think the car will a problem. The 12kWh battery has 80 cells at 4.1 volts (4.2 is considered maximum and 4.1 basically doubles the life time) so 328 volts fully charged or 336 absolute maximum.

I think this guy means LiFePo4 which has a lower voltage so needs more cells as he says 93 or 94. They are also relative safer than the 'normal' type but less energetic.

I'm not sure why you'd go through all the effort and cost unless the cells are cheap, and petrol is really expensive.

Keep in mind that the drive battery is split into two banks of 150 or so volts with the contactor in the middle and no grounding connection. it would probably be a good idea to do any additional battery connections the same way

 

[Stevepl11]

I would have though a range extending trailer would be a better option, I note that the new Cybertrucks, long range pack takes up 50% of the load space, so you can go further but carry less?

How would you connect that? and every EV towing test on YouTube I've seen says it sucks. There's not just added weight but additional drag. At least a battery added in the boot limits the weight and adds no drag

 

[MiPHEV]

Looks like someone's already done it based on those pictures, if you have a link or any more details on the retrofit I'd be interested in seeing more. 100AH of LiFePO4 would take up about 90L of cargo volume and add approximately 200kg of weight, and should in theory over triple the EV range. Paralleling non-similar cells as long as the string voltages are close enough to each other before contactor cut-in tying them together is no problem at all, the internal equivalent resistance variation balances the current draw and state of charge without any concerns, you can see examples of this on YouTube where you can parallel a 1 AH cell with a 300AH cell, discharge by some arbitrary percentage, and then test the remaining charge of each cell, they are equivalently discharged.

Hopefully the person did a nice job of the safety aspects, fusing, thermal/bms, and contactor safety circuits, but as long as these cars are not smart enough to compare the coulombs/current in/out of the OEM HV battery to the coulombs/current consumed at the inputs of the motors/accessories, the OEM system will likely have no way of knowing this is happening. I would want someone else to take the hit testing all of that before buying a battery pack, that in the case of a 100AH add-a-pack, would cost almost $3500.