T7 Ocean Battery Upgrade

[blind_oracle]

So Ocean has two 40Ah LiFePo4 batteries behind the fridge, and around/between them there's a lot of free space. I think one can easily fit 140-150Ah single one in there.

Problem is that the batteries seem to be connected to the car over some data buses (from their BMS?) and I'm not sure what would happen if I just replace it with a "dumb" battery that doesn't talk to the car. Has anyone tried that yet?

 

[Rubinstein]

So Ocean has two 40Ah LiFePo4 batteries behind the fridge, and around/between them there's a lot of free space. I think one can easily fit 140-150Ah single one in there.

Problem is that the batteries seem to be connected to the car over some data buses (from their BMS?) and I'm not sure what would happen if I just replace it with a "dumb" battery that doesn't talk to the car. Has anyone tried that yet?

View attachment 143086

Interesting idea, I’d have a go if it was possible

 

[blind_oracle]

For testing I've plugged a 80Ah LiFePO4 battery in parallel with the ones that came with Cali. So it's now (40 + 40 + 80), double the capacity. First, of course, one need to equalize the voltages.

I've put it into the cupboard above the battery compartment - it has a removable shelf with a fuse box under it. One can remove the handle from this shelf (non-destructively) and get a hole through which you can pass the wires to the cupboard.

Overall it works fine, the load is spread more or less evenly between them since the capacities (that is - internal resistances) kinda match. The only downside is that when looking at the charge/discharge current on the camping dashboard or in app you will see half of it, since it reads directly off the batteries it seems and doesn't see the 3rd one.

In a 2-3 weeks I should get 230Ah cells and will try to use them instead in parallel, they should also fit into a cupboard. The capacities won't match, but it shouldn't be a problem probably. Only the current in the stats will be much off.

 

[Rubinstein]

For testing I've plugged a 80Ah LiFePO4 battery in parallel with the ones that came with Cali. So it's now (40 + 40 + 80), double the capacity. First, of course, one need to equalize the voltages.

I've put it into the cupboard above the battery compartment - it has a removable shelf with a fuse box under it. One can remove the handle from this shelf (non-destructively) and get a hole through which you can pass the wires to the cupboard.

Overall it works fine, the load is spread more or less evenly between them since the capacities (that is - internal resistances) kinda match. The only downside is that when looking at the charge/discharge current on the camping dashboard or in app you will see half of it, since it reads directly off the batteries it seems and doesn't see the 3rd one.

In a 2-3 weeks I should get 230Ah cells and will try to use them instead in parallel, they should also fit into a cupboard. The capacities won't match, but it shouldn't be a problem probably. Only the current in the stats will be much off.

good stuff, if you could post a few pics to show what you have done/doing would be very helpful

 

[blind_oracle]

good stuff, if you could post a few pics to show what you have done/doing would be very helpful

Will do more photos once I get the 230Ah ones.

Currently there's not much to see, just a box with a battery hooked up using two wires to one of the original batteries below:


That's how stuff looks under this shelf (solar controller lives there for now, I've posted about solar in a separate thread):

 

[Amcali]

battery is connected via CAN you won’t just be able to plug n play. I believe any battery change would have to be coded in to the vehicle if even possible?

 

[blind_oracle]

battery is connected via CAN you won’t just be able to plug n play. I believe any battery change would have to be coded in to the vehicle if even possible?

Yeah, that's the reason I am currently going in the direction of adding parallel battery.

I have somewhere the CAN analyzer, maybe if I have time at some point I will try to decode the battery protocol and emulate it...

 

[Amcali]

Cool! Interesting setup! Stay safe and keep focus pls when making these changes. Looking forward to outcome!

 

[Rubinstein]

Yeah, that's the reason I am currently going in the direction of adding parallel battery.

I have somewhere the CAN analyzer, maybe if I have time at some point I will try to decode the battery protocol and emulate it...

This is logical as your not replacing the battery, your just adding capacity, so in theory the system will not pick it up

 

[blind_oracle]

This is logical as your not replacing the battery, your just adding capacity, so in theory the system will not pick it up

Yup, but if I want to see the real (dis)charging current and whatnot I will have to convert my battery BMS data into something VW controller would understand...

 

[WelshGas]

Yup, but if I want to see the real (dis)charging current and whatnot I will have to convert my battery BMS data into something VW controller would understand...

So the T7 uses the BMS data from the Lithium batteries for its display?
Who makes these Lithium batteries.?
Is the BMS data provided in a standard format or is it VW specific?
If it is VW specific does the manufacturer make a larger capacity battery?

 

[blind_oracle]

So the T7 uses the BMS data from the Lithium batteries for its display?
Who makes these Lithium batteries.?
Is the BMS data provided in a standard format or is it VW specific?
If it is VW specific does the manufacturer make a larger capacity battery?

1) Yes, it seems so. The batteries have additional connectors for data bus (CAN probably). When I connected another battery in parallel which was with a bit higher voltage - camping screen showed a burst of current flowing into leisure battery while they equalized.
2) No idea, the stickers say VW, but probably some OEM. I couldn't find anything online
3) Also no idea, probably VW specific, but I haven't sniffed it yet
4) Well at least officially there's no larger capacity