No BMS Charging.

Trying to figure a way to charge individual cells ( P Groups ) in my 13S battery build. Looking for some means some what like the TP4056 . My hurdle seems to be I only want to charge the cells to 4.0V not the standard 4.2V. I can live without the Capacity loss and like the idea of extended battery cycle life.

Charging individual Cell groups would eliminate the need to Balance the battery, eaa?

Does anyone know of a Schematic or cheap Chinesium PCB that could be employed ?

I have no requirement for Over Discharge Protection. The Motor Controller provides that function along with my diligent battery monitoring.

Any Ideas out yonder ?

Jim

There's a lot more info in the various other "no bms" threads, but you could use individual CC/CV power supplies on each cell group, or use just one and move it between cell groups as each charges (either manually or automatically with some sort of DIY switching system). Or use a programmable RC charger that lets you change the max voltage.

However...if you are using quality cells that are well-matched, and you are using them well within their specifications, not pushing them hard either in charge rate or discharge rate, and not running them down too far in discharge, then they'll stay balanced on their own, and you could just use a bulk charger, and simply monitor the voltages as needed, and balance if they ever need it.

By the time they begin to have regular balancing issues, they probably will have other problems that would be best fixed by replacing the whole pack anyway.

That is pretty much the plan. The Battery is for a E-Bike 13S 6P. Was planing on just checking voltages with a monitor after every few charge cycles. It will be equipped with the BMS wiring so manual charging to balance won't be a big deal. I'm building three maybe four packs using batteries reclaimed out of Never Used Modem Packs . Other then Shelf Life these cells are all but new. Cell capacities are quite uniform so really don't think they're going to drift away from each other much. Using the RePackr Program the numbers look quite good.

Still would like to find a means to Individually charge each cell group bypassing any BMS requirements all together. Would be cool if I can figure out a way to switch a small CC/CV charger between the cell groups . Maybe via Arduino and FETS. I'll mess with the Idea when I have more time.

Capacity: 15038
Divergence: 0
Deviation: 55
Capacity: 15038
Divergence: 0
Deviation: 68
Capacity: 15038
Divergence: 0
Deviation: 111
Capacity: 15038
Divergence: 0
Deviation: 75
Capacity: 15038
Divergence: 0
Deviation: 62
Capacity: 15037
Divergence: -1
Deviation: 87
Capacity: 15038
Divergence: 0
Deviation: 56
Capacity: 15037
Divergence: -1
Deviation: 60
Capacity: 15037
Divergence: -1
Deviation: 42
Capacity: 15037
Divergence: -1
Deviation: 60
Capacity: 15038
Divergence: 0
Deviation: 92
Capacity: 15038
Divergence: 0
Deviation: 102
Capacity: 15038
Divergence: 0
Deviation: 96

Berquistj said:

I'm building three maybe four packs using batteries reclaimed out of Never Used Modem Packs . Other then Shelf Life these cells are all but new. Cell capacities are quite uniform so really don't think they're going to drift away from each other much. Using the RePackr Program the numbers look quite good.

Click to expand...

Keep in mind that capacity isn't the main thing that determines drift in use--internal resistance does. If soem cells have higher Ri than others, they'll drop in voltage more during discharge, and rise in voltage faster during charge, causing imbalance during current flow--but they may not appear imbalanced in a static voltage check.

Maybe via Arduino and FETS.

Click to expand...

I'd rather use a servo and a rotary switch, because a FET's primary failure mode is shorted...which might be a problem if it shorts across a cell group. The rotary switch is more likely to fail open. Bigger and clunkier, but safer. Can also be manually operated if you put a knob on it.

What's this battery for ?

Thank You for the Heads up. Not given much thoughts about the Internal Resistance . Yes the last box of modem batteries show quite a spread on the resistance. Guess that would not affect the P Groups but could cause drift between the Groups as a whole. Hopefully the variations would somewhat average out between groups and not be much of a issue ?
Rotary switch is a good Idea and could be a easier means to do my balance charging when and as required. Could just build a Dongle thing to plug into my charger interfacing to the JST-HX connector the monitor will be using. Would not need to be on the battery proper.

Post by 999zip999 » Sep 26, 2018 10:51 am
What's this battery for ?
Primary objective right now is a few E-Bike Batteries but a Small Power Wall is in the Mix. Want to deal with that in the same fashion.

Results of current modem batteries under test:
01 2228 40
02 2271 38
03 2222 40
04 2262 37
05 2255 62
06 2244 60
07 2221 46
08 2190 46
09 2293 40
10 2254 48
11 2229 48
12 2157 51
13 2138 49
14 2190 45
15 2238 42
16 2109 45
17 2273 42
18 2223 39
19 2220 39
20 2255 31
21 2253 66
22 2173 28
23 2198 52
24 2191 55
25 2301 36
26 2256 41
27 2206 38
28 2227 35
29 2184 68
30 2220 62
31 2255 65
32 2207 69
33 2147 57
34 2261 65
35 2074 50
36 2243 47
37 2209 33
38 2327 67
39 2270 65
40 2290 35
41 2284 40
42 2193 57
43 2239 10
44 2282 16
45 2257 10
46 2258 18
47 2135 22
48 2155 49
49 2261 67
50 2165 61
51 2101 10
52 2305 10
53 2209 10
54 2350 17
55 2249 73
56 2245 51
57 2148 68
58 2138 51
59 2234 71
60 2276 83
61 2209 68
62 2274 75
63 2291 20
64 2237 38
65 2296 10
66 2226 51
67 2328 38
68 2224 50
69 2275 10
70 2290 47
71 2228 29
72 2261 10
73 2109 42
74 2229 49
75 2164 50
76 2228 47
77 2290 16 ILV
78 2266 31 ILV
79 2301 10 ILV
80 2340 39 ILV
81 2105 54
82 2110 48
83 2272 76
84 2242 80
85 2133 10
86 2323 10
87 2259 13
88 2180 22
89 2278 65
90 2155 77
91 2221 62

. I'm going to give this a try ! On the Bench of course. Active Cell balance on Pack Charging. Using this Charge Set up the cells will all be charged to my preset voltage every time I use this charger. Not required all the time but by using this charger my pack will be balanced within the limits I set. I can do as I wanted charging my cells only to 4.00 Volts in a attempt to extend cell life and charge cycles. Order set to Tayda Electronics ready for me to come up with some chump change. Need to work on a PCB that I can burn here at home. Or just Strip Vero Board. I have the Lay File but no program to use in modifying same. Current PCB is set up for only 3S but just need to modify to S13. I think I can do it with the paint Program easy enough. Parts are only like $15 or so . Time is my enemy . Found this Idea on Youtube of course. Figure I will be able to use a standard charger off and on monitoring the Cells with the monitoring meters. When and IF they start to drift out of balance I'll simply use this charger to bring all back in alignment. In they're set up they employed the LM 317 as Voltage and Current regulation. I'll use a CC/CV Boost converter. To much current required for the little Lm317. Cool, eaaa? Someone let me know if you see any bad Ju Ju in the works please ? Emmmmmm I'm Clueless on how to post photo's here ?

If interested the Schematic and other info can be had here: http://www.kit-shop.org/zip/bsmeng.zip



[youtube]https://www.youtube.com/watch?v=v_RfcPI3WKc[/youtube]