4s LiFeP04 Battery Pack - PCM Problem
4s LiFeP04 Battery Pack - PCM Problem
(OP)
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:

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:






RE: 4s LiFeP04 Battery Pack - PCM Problem
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
RE: 4s LiFeP04 Battery Pack - PCM Problem
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
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..
RE: 4s LiFeP04 Battery Pack - PCM Problem
Yeah, it sounds like it's probably defective - it happens. :/
Keith Cress
kcress - http://www.flaminsystems.com
RE: 4s LiFeP04 Battery Pack - PCM Problem
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?
RE: 4s LiFeP04 Battery Pack - PCM Problem
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
RE: 4s LiFeP04 Battery Pack - PCM Problem
http://www.batterysupports.com/24v-252v-7s-30a-7x-...
http://www.batterysupports.com/4s-144v-148v-168v-1...
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RE: 4s LiFeP04 Battery Pack - PCM Problem