Help Design Booster Multi Dual Batt Pack -> 60v 88v Maybe ?

[deVries]

I was on another thread when Nick asked...

My booster pack long-ride pack will consist of 2 Milwaukee 28v packs that are in parallel adding about 5ah @28v, and my daily pack will top-off at 59v 8-9ah and start running nominal in the mid-50's, I'm guessing. So, adding that 2pack of parallel Milwaukee's in series to the main pack will cause these two Milwaukee's to run down first and go off-line with less AH. Initially, my volts will be way up there at about 85v, though I'm not going to use this to be a speed demon. This should allow my controller to still function correctly with the regular 50v pack, because the BMS in the Milwaukee's will cut these two 28v off first.

I think we need to check on the series/parallel arrangement here. Can you list the batteries you want to use, and then we'll try to work out the best configuration?

Nick

So, here is my design diagram using 64 A123s and 2 Milwaukee 28v packs. Hope many will offer their design ideas, and, yes, critiques are 'the most' welcomed too for improvement.

TIA

View attachment Battery Pack with Booster.JPG

 

[deVries]

In my notes for the diagram I wrote:

Note: I did 8pack groupings with 2series + 4parallel. I did the 2series because I theorize these will stay well balanced in pairs, rather than going with 4p1s packs. Experienced battery builders can comment if I'm totally off-base here. I am just wild-guessing with this 2s pairing idea vs 1s. COMMENTS ???

Docbass has suggested to me that putting 2 in series to make 8 packs is not a wise plan. He suggests this will raise the rate/risk of battery imbalance, so I will redo my diagram to include his advice and post it here. I will do 16 packs of 4p1s instead.

Modified and improved design showing X -mistakes with design change in upper left...

View attachment Battery Pack with Booster 4p Packs.jpg

 

[Tiberius]

So, here is my design diagram using 64 A123s and 2 Milwaukee 28v packs. Hope many will offer their design ideas, and, yes, critiques are 'the most' welcomed too for improvement.

TIA

Hi,

I'm afraid I don't quite follow the diagram. It probably helps here to go back to basics. Like Docbass, I do not like the idea of different pack types in series. I think I see what you are trying to do, but the normal way of combining packs to extend range is this: Group the cells into packs of about the same voltage and then combine them in parallel.

You didn't say what motor and controller you are using, but it sounds like you want to get to about 60V. That means using the 2 Milwaukee's in series to get 56 V and then setting up the A123s to give something similar. Possibly 16S packs of the A123s would work out.

What is the cell configuration inside the Milwaukee packs?
What BMS will you be using with the A123s?

I've never used these cells. Perhaps someone with direct experience can contribute.

Nick

 

[deVries]

So, here is my design diagram using 64 A123s and 2 Milwaukee 28v packs. Hope many will offer their design ideas, and, yes, critiques are 'the most' welcomed too for improvement.

TIA

I'm afraid I don't quite follow the diagram. It probably helps here to go back to basics. Like Docbass, I do not like the idea of different pack types in series. I think I see what you are trying to do, but the normal way of combining packs to extend range is this: Group the cells into packs of about the same voltage and then combine them in parallel.

See attached graphic with this post.

You didn't say what motor and controller you are using, but it sounds like you want to get to about 60V. That means using the 2 Milwaukee's in series to get 56 V and then setting up the A123s to give something similar. Possibly 16S packs of the A123s would work out. What BMS will you be using with the A123s?

BMC Motor
64 A123s ~ 59v w/new BMS ES Designed Richard & Gary, etc. OR Docbass DC DC Converter and a balancer of some kind. Pro/Cons about this?
2 Milwaukee in Series 56v using its own BMS

View attachment Battery Pack with Booster 4p Packs.jpg