4s LiFeP04 Battery Pack - PCM Problem

[RyanRDB]

Hey everyone, I built an 18650 4s battery pack with a PCM, but I’m having trouble with the PCM part. I followed the wiring diagram they provide & I could swear that I have it wired correctly, but I’m not getting any voltage out of the lead wires from the PCM.

I know I have the batteries connected correctly because the voltage is correct when I measure it directly from the (-) and (+) tabs on the pack. Maybe the PCM is defective..?

It’s damn near impossible to find a video or clear instructions on the web, for how exactly to wire these things, so I thought this would be a good place to get some feedback. I’d appreciate it if anyone could point out any mistakes I’ve made or something(s) I should have wired differently.

Here’s a pic of the wiring diagram they provide, and a pic of how I have the batteries wired to the PCM:

 

[itsmoked]

Looks fine to me. I believe you've got it correct. You do know which end is which on the batteries?

I'd expect the PCM to NOT give you any power if the batteries are low as that is an important aspect of the PCM function - preventing overdischarge.

Of course they can also protect from over current draw.

Could be your batteries are too low or your load is to great?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[RyanRDB]

Itsmoked,

Thanks for the reply. Good to know it's wired correctly (I'll take your word for it -- from your website, it looks like you know what you're talking about ).. It's been driving me crazy trying to determine if it's my connections or the PCM that's screwed up. The cells are perfectly balanced, fully charged, and I haven't used it to power anything - just checked the voltage at the end of the "p" leads (0v).

I just re-checked all the connections & they're all solid, with no short circuits. Wow, this is super frustrating. I guess I'll have to contact the place I bought it from (all-battery) and tell them I think it's defective. Hopefully they stand behind their products..

 

[itsmoked]

I need to seriously update my dated looking site but thanks for the kind word.

Yeah, it sounds like it's probably defective - it happens. :/


Keith Cress
kcress -

http://www.flaminsystems.com

 

[RyanRDB]

Well after some tinkering I was finally able to get it working. Just thought I'd give you the update. It's really odd, but after short circuiting the "B" tabs really quickly, it started getting power at the "P" tabs..

I honestly have no clue why that did the trick, but I guess ignorant tinkering gets the job done in some situations .

I just realized the wiring diagram / directions doesn't show where to connect the charger leads though.. I can't decide whether to connect it to the "P" or "B" tabs -- It seems like the P tabs would be the wrong ones, as they're the outlet for the power, but I don't see how the PCM would be able to cut off the charging / prevent overcharging if I were to connect the leads to the "B" tabs.. Plus, I don't want to fry the circuit from an improper connection.

I'd take your word for it though -- where would you connect the charging leads?

 

[itsmoked]

Huh. Weird I agree. Next time buy something with a manual!! LOL

A big hazard is charging so yeah, I'd really expect the PCM to protect and BALANCE the charging of each cell, so yes, I vote for the Ps.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[IRstuff]

I think that's typical; the assumption is that the battery/PCM are not loaded during charging for these devices.

http://www.batterysupports.com/24v-...thium-ion-lipo-battery-bms-pcm-pcb-p-258.html

http://www.batterysupports.com/4s-144v-148v-168v-12a-liion-battery-pcb-pcm-circuit-board-p-240.html

TTFN
faq731-376

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[RyanRDB]

P tabs it is - I just soldered them on earlier today and it charged up perfectly. Thanks for all the help