I've been talking to a local supplier (relatively speaking, they're 1200km away lol) for a custom built 48v Lifepo4 battery pack to use with my Victron Multiplus 3000 / MPPT 150-70 / BMV-702.

Since it's not a branded off-the-shelf product, I've been trying to get more information on the pack itself --

1) Total size of 210ah using 45 CALB CAM72 cells (15s3p)
2) Some OEM BMS (I'm trying to push for bluetooth/connectivity based one) so I can get all the voltage information a bit easily -- but I understand it's not gonna be able to talk to my inverter
 

Now, I have some interesting questions that (I need @plonkster's and everyone else's opinion on!) --

1) Do you think 15s makes sense? I've seen people building 16s -- I guess both can work either way right with a Victron setup? Does the axpert not care too? (I'm thinking of getting an Axpert to run off of the same battery, but that a very future setup, just poking my brains into it)
2) Is it possible to identify the "cell" more accurately? I know this is a stupid question, but how to ensure I'm not being taken for a ride with a cell that isn't what is being promised?
3) Is there a preset (in Victron) that I can use to specify a custom charge profile? (i.e let's say I want to charge only up-to 90% and not discharge beyond 20%, for example) -- I'm not sure how reliable it would be to use voltage for this calculation?
4) Do you think it's possible to parallel with a similar pack in the future (provided both packs are same voltage during connection?)
5) Instead of a complete pack of 210ah, do you think it'd make sense to have 3 different packs (i.e 3 separate packs with their own BMS)? Different packs mean higher cost but I'm not sure how common it is to use the same BMS for a parallel pack.

 

Thanks -- look forward to everyone's feedback! Hope y'all are safe.

(sorry I haven't been so active here, life is pretty hectic ... hoping to be a regular member again!)

Edited June 9, 20206 yr by 9xsolar

2 minutes ago, 9xsolar said:

1) Do you think 15s makes sense? I've seen people building 16s -- I guess both can work either way right with a Victron setup? Does the axpert not care too? (I'm thinking of getting an Axpert to run off of the same battery, but that a very future setup, just poking my brains into it)

Not a problem. Just configure the voltages correctly and stick to no more than 3.5V per cell. Axpert's sometimes have an issue getting back into bulk once they reached float because they don't have a lithium curve and the need a 2V drop (or something) before they go back to bulk. Victron has a Lithium curve, you just select that.

5 minutes ago, 9xsolar said:

3) Is there a preset (in Victron) that I can use to specify a custom charge profile? (i.e let's say I want to charge only up-to 90% and not discharge beyond 20%, for example) -- I'm not sure how reliable it would be to use voltage for this calculation?

On the charger tab you select the lithium curve. Then assuming you'll be using ESS, you configure the dynamuc cut-off curve to cut discharge if the voltage goes too low under load. And you can set the charge voltage to 3.45V per cell or something. If not running ESS, just set the low-voltage cut-off. Ideally, you want to get a BMV-712 though 🙂

7 minutes ago, 9xsolar said:

4) Do you think it's possible to parallel with a similar pack in the future (provided both packs are same voltage during connection?)

The caveat to paralleling is to consider what happens in a fault condition. As an extreme example, if I have 50 parallel strings, and one of them develops a fault such that the other 49 starts dumping current into that path, ideally we don't want smoke and fireworks...

Paralleling should be fine as long as you use equal length cabling, busbars, and individual fuses per string.

10 minutes ago, 9xsolar said:

Instead of a complete pack of 210ah, do you think it'd make sense to have 3 different packs

I'd go for one large pack.