Our new bus (as yet unnamed) project!

[Native]

Originally Posted by brokedown

Yes it's just a hint

A rather bizzare hint that I just can not fathom.

[JDSquared]

Originally Posted by Native

Nirvana - Lithium ... I love the song or at least how they do it. I never did catch all of the lyrics while listening to it over the years. I just now looked up the lyrics ... and I was right in that they do not make a whole lot of sense to me.

I didn't listen to it when I posted it but just watched the video now. Dave Grohl looking 20 and skinny and all that hair. Man we got old fast.

[JDSquared]

Originally Posted by Native

A rather bizzare hint that I just can not fathom.

I'm just guessing but my first thought went to his house batteries.

[Native]

Originally Posted by JDSquared

I'm just guessing but my first thought went to his house batteries.

Now that you have said it .... DUH!!! Just *way* too subtle for me I guess.

[musigenesis]

Originally Posted by Native

Now that you have said it .... DUH!!! Just *way* too subtle for me I guess.

My brain started at "he's making a rock video?" and then never went anywhere.

[brokedown]

Nope not making a rock video. i came across some great prices on power system components that hopefully will start arriving at some point soon. While I've generally been against Lithium, it was entirely around the costs of the batteries and BMS, but I worked a deal to get 4kwh with bms for less than lead acid. More info as stuff starts to arrive and i've convinced myself I haven't made a terrible mistake!

PS - I like Amy Lee's song better than Kurt's.

[JDSquared]

Originally Posted by brokedown

Nope not making a rock video. i came across some great prices on power system components that hopefully will start arriving at some point soon. While I've generally been against Lithium, it was entirely around the costs of the batteries and BMS, but I worked a deal to get 4kwh with bms for less than lead acid. More info as stuff starts to arrive and i've convinced myself I haven't made a terrible mistake!

PS - I like Amy Lee's song better than Kurt's.

I like them both actually. I think I held onto my teenage angst well into my forties.

I'm trying to get my lithium batteries at a decent rate. If you want to share any information from your supplier

[brokedown]

The particular ones I got are these: https://batteryhookup.com/collection...lipo-batteries

It will require some DIY but my plan is to convert the packs from 9s to 2p7s for 48v operation, the 10A BMS is still adequate for me in the grouping I'll be using.

I ordered a couple extra packs to account for potential dead cells. That supplier has a lot of other great deals but this one takes the cake for price vs capacity not to mention the included BMS.

[brokedown]

4x 390w solar panels! I've got some more kit to go with them, i have some paint blemishes to fit on the roof and then to decide on a mounting system for these bad boys for my next update.

[kazetsukai]

Originally Posted by brokedown

The particular ones I got are these: https://batteryhookup.com/collection...lipo-batteries

It will require some DIY but my plan is to convert the packs from 9s to 2p7s for 48v operation, the 10A BMS is still adequate for me in the grouping I'll be using.

How many of these did you get, two for 29.6Wh of capacity? 4x 390W panels is 1560W. At ~25.9V that's 60A. Can these handle the 30A-ish charge rate each?


I use Tesla batteries, so I'm no stranger to DIY lithium, but looking at this I'm sorta tilting my head. You likely know more about your plans than I do, but one of the reasons I consider my setup to be safe is that I'm _far_ below the limits on charge rate for these packs. Not even close.

[brokedown]

Originally Posted by kazetsukai

How many of these did you get, two for 29.6Wh of capacity? 4x 390W panels is 1560W. At ~25.9V that's 60A. Can these handle the 30A-ish charge rate each?


I use Tesla batteries, so I'm no stranger to DIY lithium, but looking at this I'm sorta tilting my head. You likely know more about your plans than I do, but one of the reasons I consider my setup to be safe is that I'm _far_ below the limits on charge rate for these packs. Not even close.

I've altered my plans a bit to use them at their native voltage with a programmable charge controller rather than move cells around. As such they're roughly 36v and will all be attached in parallel. I've got 40-something packs that took a charge and passed tests so I'll be putting under 2A charge rate per pack if I were to max out my 60A charge controller.... Nowhere near their max charge rate.

[kazetsukai]

Originally Posted by brokedown

I've altered my plans a bit to use them at their native voltage with a programmable charge controller rather than move cells around. As such they're roughly 36v and will all be attached in parallel. I've got 40-something packs that took a charge and passed tests so I'll be putting under 2A charge rate per pack if I were to max out my 60A charge controller.... Nowhere near their max charge rate.

If I may, whats your final bank configuration? 40 9S packs in parallel? Or 9 40P packs in series? And what BMS / balancer are you using for the bank, or are you using a balancer per pack?

[EastCoastCB]

yall aren't messing around with this one are ya?

[brokedown]

Originally Posted by kazetsukai

If I may, whats your final bank configuration? 40 9S packs in parallel? Or 9 40P packs in series? And what BMS / balancer are you using for the bank, or are you using a balancer per pack?

The packs are 9S with a built in BMS, per pack. That gives them a voltage range of 25.2 to 37.8V, and the BMS expects around 42v to charge them. They use XT60 connectors, which I'm using to connect to bus bars in parallel.

At least, that's the plan.

Here are the packs I bought: https://batteryhookup.com/collection...12478159945807

[kazetsukai]

Originally Posted by brokedown

The packs are 9S with a built in BMS, per pack. That gives them a voltage range of 25.2 to 37.8V, and the BMS expects around 42v to charge them. They use XT60 connectors, which I'm using to connect to bus bars in parallel.

At least, that's the plan.

Here are the packs I bought: https://batteryhookup.com/collection...12478159945807

So there's no parallelization at the cell level? You parallelize at the battery level (parallelization is _after_ serialization)?

[brokedown]

Correct, the packs are 1P9S -> BMS -> 44P or so at the busbar,

[kazetsukai]

Originally Posted by brokedown

Correct, the packs are 1P9S -> BMS -> 44P or so at the busbar,

I ran my three Tesla packs in parallel (for a 24V bank, parallel-after-series) for a little over a year. I just recently converted to series (for a 48V bank) because I'm upgrading my solar (700W of PV -> 3000W of PV), and my charge controller was limited to 2400W PV at 24V. Quite a few people poo-pooed me running parallel-after-series...

I think, due to how Tesla packs are designed, they're for the most part safe to run packs in parallel. The reason for this is, they are each configured in 6S74P. Each of the following six highlighted areas represents a cell containing 74 cylinders wired in parallel, each with its own fuse:


I don't want to reject what you intend to do, I just want you to think of a possible failure scenario. Maybe I'm preaching to the choir or you know something I don't. Lets just take the following hypothetical. Take a pair of 6S Lipo batteries for RC cars, and run them in parallel. Now lets say one cell in one of the batteries fails, causing the voltage for the bad pack to drop 3.7V. What happens?

The good pack will dump energy into the bad pack due to the difference in voltage. And as you charge the packs, the charger will try and bring the bank up to your desired top voltage, which will overcharge the good cells in the bad pack. If your BMS can _reliably_ disconnect the bad pack from the array upon cell failure, this isn't a problem. If your "BMS" only balances the pack internally and can't cut it out of the array, it is insufficient for the task.

If it is possible, I think you should parallelize at the battery level, serialize at the bank level. In my case it is not, but as I have high parallelization at each cell already, its very unlikely I'd experience such a failure, and my BMS _will_ cut the pack out of the array if that happens. I'll likely parallel again when I have 4 + batteries (I only have 3, so one is at rest for now).

I love folks to do DIY lithium. I'd rather say something unwelcome / unnecessary than not voice a safety concern. Hope this helps.

The packs you got are a sweet deal in terms of price per watt. Got me beat there.

[WIbluebird]

Love your build so far. It's great to see fellow AARE owners on this site, especially the early 2000s ones like ours.



Have you disabled your ignition interlock yet? If so I'm curious how you accomplished it. I'm in the middle of figuring out the best way to disable it on my 2001 AARE.

[brokedown]

Originally Posted by kazetsukai

I love folks to do DIY lithium. I'd rather say something unwelcome / unnecessary than not voice a safety concern. Hope this helps.
.

The BMS does appear to kill the pack with a cell failure. I have a couple packs that didn't perk up after adding some voltage manually, even though the total voltage is above the minimum rating for the pack. As of yet I'm not sure of the exact parameters that constitute a failure, and the BMS itself appears to be proprietary to these packs. I'm for sure aware of the possibility of batteries leeching off each other, but I'm assuming that keeping an eye on the voltage will alert me to a problem. Being connected via XT60 makes it really easy to disconnect and test.

The way the cells are constructed it's relatively difficult to split and repurpose the packs without damage, so I'm pretty darn motivated to make them work as-is!

[kazetsukai]

Originally Posted by brokedown

The BMS does appear to kill the pack with a cell failure.

Proper system monitoring is a must for any solar setup. Looks like you've done your homework.