FUCKPUTIN2022LOL OP t1_iseb0ix wrote on October 15, 2022 at 9:12 AM

Reply to comment by MeasurementGrand879 in Not at all a "Hands on" person but looking to change that, need help with battery math. by FUCKPUTIN2022LOL

Not portable at all. Shielded and bolted down with easy access for maintenance. Proper ventilation. This is more of a stupid pipe dream than anything. But the only reason youtubers, myself or anyone is considering this is because I can create a battery 10x cheaper and with more capacity than anything out there. A jackery 2000 with the max solar array is 3x more expensive than my Frankenstein and twice the solar power.

hopingforabetterpast t1_iseegtj wrote on October 15, 2022 at 10:03 AM

There's a reason it's a fraction of the cost. Please listen to those who took the time to respond.

tafrawti t1_isfgin1 wrote on October 15, 2022 at 4:00 PM

If he won't listen to the other posters, I'm not gonna waste my time on him to try and keep him alive. I build battery packs for a living half the week.

dyyd t1_isipxo4 wrote on October 16, 2022 at 8:08 AM

Question to an experienced builder. Would such a pack be safer if built up from multiple 4s1p modules which each had their own BMS? If I am not completely mistaken then it should be possible to put packs in parallel without the BMS boards getting fried or going crazy.

tafrawti t1_isiujxj wrote on October 16, 2022 at 9:13 AM

Well I don't design them, I do the welding and heavy current soldering (radio guy here, this a power dude's design, or at least someone is his department)

One potential (pun intended, kinda) problem is that slight differences in characteristics between individual BMS boards could lead to strange things happening - if there is even a few mV difference between individual board calibration, placing several units in parallel could lead to things getting out of hand. This is especially true if the BMS has a lot of proactive monitoring on discharge (simple boards don't monitor the discarge so much, if at all - the cheapest are more corerctly called charge controllers)

Now, in a perfect world, good quality compnents, good design, attention to grounding to prevent EMC issues, low RF environment, stable temperatures, good quality cells all similar in characteristics, yeah, you MAY get away with such a multi-BMS pack. But I'm not sure I've seen that design commercially except maybe in EVs. So if you try it, be careful.

I have no idea if any given BMS chip would even tolerate that (check for reference designs on datasheets) and beware that most Chinese BMS boards sold are adequate-but-shoddy in my limited experience with them (solely from fixing up my friends power drills or converting old NiCad ones to lithium)

Like i say, I don't design them, I just spend my time on quiet shifts doing the tabs (bigass tab welder) and 0AWG soldering (gas torch) because I have years of experience with both procedures, But mainly because when they tried getting their usual contractors to do that kind of work they had several serious fires and two explosions that cost a lot of downtime and a lawsuit. So it was "hey old guy - can you help us with these?"

Batteries are dense in stored energy. Big ones are scary. Huge ones can kill. In many ways.

frzn_dad t1_isg6i9v wrote on October 15, 2022 at 7:02 PM

And when you burn your place down there isn't anyone to sue but yourself. Your insurance may even try to fight covering it because of what you were doing.