Does anybody here think 12 volt is the way to go for flexibility?

[ksmithaz1]

I can't imagine suggesting to someone who is trying to get a modest size / beginner project done in a reasonable amount of time, that they should also go through the PITA to build their own battery from misc imported parts. Maybe project #3, but project #1 ?

Since we were talking about running 12's in series . . . The argument becomes 16x3v vs 4x12v. Assuming LP4 3.2v 13v, whatever for a 51.2v final voltage. Keep in mind the 12's are just a 4x3v in a box with a BMS.

1 BMS vs 4 in series with their own idea of what they need.

RE: shipping, a single 3.2 is not as heavy as a 12.
Single 51.2v 100AH rack unit is 16x3v inside, pop the cover and replace /return the bad cell.
DIY is much cheaper but requires a modicum of patience you might not have as pretty or convenient a box.

A lot less wiring and connecting on a single 51.2v 100AH rack unit, 2-#4 cables in open air to whatever bus.

I think the point is in for a penny, in for a pound. If you are willing to wire up 4 12v in series, now you have to find/build and/or buy the interconnect cabling, and come up with a box or shelf to put them on. Why not just go the extra mile and string 16 3's with the provided bus hardware, and slap a BMS on the side of the box. You only add the 16 sense/charge wires and the power cables to the BMS.

 

[HarryN]

Since we were talking about running 12's in series . . . The argument becomes 16x3v vs 4x12v. Assuming LP4 3.2v 13v, whatever for a 51.2v final voltage. Keep in mind the 12's are just a 4x3v in a box with a BMS.

1 BMS vs 4 in series with their own idea of what they need.

RE: shipping, a single 3.2 is not as heavy as a 12.
Single 51.2v 100AH rack unit is 16x3v inside, pop the cover and replace /return the bad cell.
DIY is much cheaper but requires a modicum of patience you might not have as pretty or convenient a box.

A lot less wiring and connecting on a single 51.2v 100AH rack unit, 2-#4 cables in open air to whatever bus.

I think the point is in for a penny, in for a pound. If you are willing to wire up 4 12v in series, now you have to find/build and/or buy the interconnect cabling, and come up with a box or shelf to put them on. Why not just go the extra mile and string 16 3's with the provided bus hardware, and slap a BMS on the side of the box. You only add the 16 sense/charge wires and the power cables to the BMS.

I can see it for large, stationary systems.

I mostly work on mobile systems with 2 - 5 kW-hrs of storage, occasionally 10 kw-hrs and significant potential for vibration.

For me, I have no interest in the liability that comes from a DIY battery pack or trying to re-purpose a battery designed for stationary use into a mobile use. Lots of people disagree with me, but when it comes to selling something, a DIY battery pack caries the risk of having zero or negative value. It is almost worse than buying a proprietary product because there is zero support for the non technically inclined.

When I do something, even as a hobby, I apply $10 / hr for my time. If I spent 3 days working on something, I could have just purchased a high quality product for $3 - 400 more and had fun with my family or worked a few more hours.

If I ever build a 20 - 30 kW-hr system for myself, I will have to think more deeply about it.


I really do understand why people do like to DIY a battery pack, I still would never suggest it to someone for a 2 - 4 kW-hr build, especially for their first project. It is enough effort for them to get that all going and a pre-made / off the shelf battery with manuals and support greatly reduces their risk for settings, etc.

 

[SparkyGage]

<snip>

When I do something, even as a hobby, I apply $10 / hr for my time. If I spent 3 days working on something, I could have just purchased a high quality product for $3 - 400 more and had fun with my family or worked a few more hours.
<snip>

I'm going to have too put this up as a sign in my shop: Harry's $10 rule - Add $10/hr to the cost of any project.

(although with inflation, it may need to go to $20/hr now.....)

 

[SparkyGage]

I don't know why so many continue to encourage fellow DIYers to buy costly, premade 12v packs and then link them all together in some way that is or isn't recommended by the manufacturer. Sidestep most of the issues discussed above by purchasing your own bms for whatever voltage you decide, along with much less expensive bare cells.

I didn't want to spend any more money or make things more complicated than they need to be. A bad cell will often be bad during the return window. I don't feel warranties are worth much, because I don't assume the company who sold them will be around in 4 or 8 years time.

Counter point: Of the 5 brands of off the shelf 12v and 24v batteries that I looked at when buying my first large battery, ALL of them were shown by their manufacturer to be able to be safely wired in series up to 48v. I know some aren't, but it is looking like most these days are.

I'm not saying its the best option, I'm just pointing out the manufactures are starting to promote this as an option.

 

[HarryN]

I'm going to have too put this up as a sign in my shop: Harry's $10 rule - Add $10/hr to the cost of any project.

(although with inflation, it may need to go to $20/hr now.....)

Perfect - I would also like one if you get that far.