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Old 08-03-2012, 11:09 AM   #43 (permalink)
Engineering first
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Location: Huntsville, AL
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We're in the same ditch, I've ordered 30 of these puppies from Eric and plan to build a two-stack, pack for our eBike:

It currently has a 48V, lead-acid battery and rated at 10 miles, one-way. I've gone 6-7 miles but my work is 10 miles away. My plan is to build two, 15 cell, stacks. I'll drive out on one and when it is exhausted, flip to the second and drive home.

I will still need a minimal BMS, more of a reverse voltage detector and shut-off. But if I have an opportunity to add a safe, minimal charge capability . . . carpe diem. I don't need 'fast' charge, 12 hours is good enough for my purposes. But that leads to my follow-up question.

Any recommendations on do-it-yourself, BMS chips and circuits? I know there are at least two around, Linear and TI if my memory serves me right. From what I remember the biggest glue piece for these ICs are the power MOSFETs which with a longer charge rate, can be 1-2A, fairly inexpensive. BTW, I had to build my own 48V battery charger from my 'junk box' when the original failed:

Crude, it didn't cost much from my 'junk box' but has turned out to be 'good enough.'

I got a note from Eric that my cells will take awhile to arrive. Then I will have to measure all 30 cells to normalize them and assemble balanced strings. I am interesting in any results you might have about the Ahr change after cycling the cells.

Now our NiMH batteries charge exothermic. Do you have any info about whether the temperature change you saw was charge or discharge?

I appreciate your efforts on cell interconnect. Once I get mine, I'll investigate some alternatives. They won't 'fit' exactly in the existing battery space, not without some clever work, but I have options.

Bob Wilson
2019 Std. Range Plus Model 3 - 134 MPG3 || 2014 BMW i3-REx - 117 MPGe, 39 MPG
JuiceBox 40 Pro (240 VAC, 40 A), KHONS portable (120-240 VAC, 12-32 A)
Retired engineer, Huntsville, AL (five times AutoPilot saved.)

Last edited by bwilson4web; 08-03-2012 at 11:36 AM..
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