First Battery Build 21700 Molicel P42A

[flippy]

I’ve had my lipo set at 3.67V LVC for years, with 32AH available and only taking half, I still get 20 miles which has been enough for me and cells stay balanced.

if you really want to prevent wear you put your LVC at 3.2V and stop charging at 4.05. you would be able to use more capacity and get even longer lifespan. or save a buck with a smaller battery. wich would be more useful i think. oversizing is great, but you can overdo it.

[kudos]

Just took the battery out for a spin, I hope you guys have somewhere you love to ride...

[kudos]

Change of plan.

Is there a meanwell that will do around 58V 8A?

[flippy]

Is there a meanwell that will do around 58V 8A?

put 2 HRP-300-36 in series. that set will do 9A all day between 57.6V and 79.2. just make sure you divide the voltage equally between them.

[kudos]

Battery now re-configured for 14S.

I have a cheap 4A charger arriving next week, if it’s good I’ll add another in parallel for 8A.

BMS should be here next week too.

[kudos]

BMS turned up today. Not bad really from China, ordered on 23rd March, only two weeks.

It came with absolutely zero instructions of course.

I’ve already managed to piece together most of the info I need, how to configure the balance harness for 14S:



The two temperature sensors are straight forward to install.

The one thing I’m not sure about is turning it on for the first time, do you need to actually install a button switch?
If so is it a switch or momentary switch?

Or can you just touch the on/off leads together once to get it going ?

[flippy]

usually its just putting the charger on it for a second or so or just jump the red/black wire on the left side.

[kudos]

I’m up and running with the ANT.

I tried the on/off wires but it didn’t turn on.

So I plugged the charger in as per flippy’s suggestion and that worked.

I use iPhone so tried Pairing directly with Bluetooth but got ‘pairing unsuccessful’ error.

Tried XiaoxiangBMS, it found the BMS, connected but data wouldn’t transfer.

Tried ANT BMS app, connected up fine. Still finding my way round the app. It only balances under charge so I’m running a manual balance for now...

[flippy]

if shorting the wires does not work you probably need to put a couple volts on it. grab a 9v battery or a fully charged cell and use that.

balance when its full, not half full. half full does not mean much. dont start balancing until you hit at least 4v.

ps: iphone does nothing. you need android for it to work.

[tmho]

I’m up and running with the ANT.

I tried the on/off wires but it didn’t turn on.

So I plugged the charger in as per flippy’s suggestion and that worked.

I use iPhone so tried Pairing directly with Bluetooth but got ‘pairing unsuccessful’ error.

Tried XiaoxiangBMS, it found the BMS, connected but data wouldn’t transfer.

Tried ANT BMS app, connected up fine. Still finding my way round the app. It only balances under charge so I’m running a manual balance for now...

I also use the ANT BMS. For the old version like mine, it is just for Android. For turning on, my seller's instruction was either plug in the charger, or you can connect a momentary switch and 12V or under (must not be over 12V, one cell of your battery should be ok) and press on the switch.
I found similar instructions from a lot of sellers from Aliexpress. May I know where and which model you buy so that we should avoid buying from that seller?

[kudos]

I bought from an eBay seller which seems to sell all sorts of generic Chinese tech, the seller name is freshcue.

I purchased the 16s 80A version.

Having a dig around on other sellers pages I now see this:



I didn’t find this when I’ve looked previously.

[st35326]

I had that same one. Grab 3-5 volts off the first series group and run either the positive or negative to a momentary switch. press for 2 seconds (beep) should wake up the Bluetooth in the BMS. Holding for 5 seconds (beep) will depower the charge and output leads. Essentially putting the BMS into energy efficency sleep mode.

[kudos]

I have some momentary micro switches on the way, so I’ll hook one up when they arrive.

I have another question, The cells were all at around 4.1 volts, so I set off a manual balance because this was going to be their first balance. Around 0.017V difference.

It took a long time so, I ended up leaving the manual balance running over night.

When I checked this morning the BMS had turned off overnight, I used the charger to turn it back on. The cells were not quite balanced either.

My question is, is it normal for the BMS to turn itself off?

I thought once it’s on, its on, unless you manually turn it off?

Is there a setting I need to check?

[TerrySavace]

Just fitted the same BMS to my first battery build - once you have switched on the BMS using a battery, you need to short the wires together to keep the BMS "on" - its actually on as the hours "on" still tick up - but the bluetooth seems to drop. So switch it on using a 3.5V or what ever battery you do, then remove the battery and join the two wires together

[mxlemming]

I've ordered 72 Molicel P42A 21700 which I'm planning to put together in 12S 6P

Sorry to hijack this... Could you share the exact dimensions? Diameter especially... I'm looking to build 20s4p of these and need to know because I'm going to 3d print a triangle rack for my bike.

These are sadly pretty much the only cells available now in the UK. But they seem pretty good!

[kudos]

Sorry they’re all wrapped up in the pack now so I can’t give exact dimensions....

Only cells left on fogstar, but they are supposed to be good.