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Heltec BMS "idiot check"

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Indefatiguable

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Nov 18, 2021
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Hey all,

I'm looking at ordering:

heltec-bms.com

13-24S Smart BMS with 0.6A 1A 2A Active balancer

[vc_row][vc_column][/vc_column][/vc_row]
heltec-bms.com heltec-bms.com

For use in a 16s string of:


Discount China Wholesale USA STOCK FAST UPS DELIVERY Grade A CATL 280Ah Battery Lifepo4 Prismatic cells with free busbar [LF280]- $160.00 - PowerWholeSale

PowerWholeSale USA STOCK FAST UPS DELIVERY Grade A CATL 280Ah Battery Lifepo4 Prismatic cells with free busbar [LF280]- USA STOCK FAST UPS DELIVERY Grade A CATL 280Ah Battery Lifepo4 Prismatic cells with free busbar HOW TO ORDER? Step1. Please check the real price (different address with...
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and as someone who has never built a lifepo4 bank before wanted to double check its what I need.

I need 200amp discharge (actually need 180a), temp cutoff (having charge cutoff until reset is acceptable), and active balancing.

I had read that I need a bms with specifically 16s, otherwise bms will detect non existent cells and trip out like a rich kid at burning man who forgot to hydrate.

This unit seems to not have that problem?

Web page linked has like zero details?

Is there a better source of information on this unit somewhere?

Thanks in advance.
 
More complete information & Details here for this BMS.
www.aliexpress.com

45.94US $ 29% OFF|Jk Bms 1a 2a 5a Balance Current 8s 12s 13s 14s 16s 17s 20s 24s Smart Jk Bms 60a 80a 100a 150a 200a 600a Lifepo4 Li-ion Battery - Battery Accessories & Charger Accessories - AliExpress

Smarter Shopping, Better Living! Aliexpress.com
www.aliexpress.com www.aliexpress.com

A Thread which may interest you as well:
diysolarforum.com

JiKong (JK) (Neey/Hankzor/HelTec/etc) Smart BMS with Active Balancer BT/Can/RS485 (Input Discussion pre-purchase)

Good Day folks, I am now very seriously looking at these JK BMS' (common rebrands in title) after watching several review vids (Good Job Andy BTW) and doing my own digging into them. Ref to Andy's 1st vid that caught my eye on these. Can't help but love the Exhuberance. Small backstory: I...
diysolarforum.com diysolarforum.com

This will help you assemble you battery pack, download the PDF I prepared from here: Luyuan Tech Basic Lifepo4 Assembly Guide

That Battery Provider is NEW as in 1st Time I have heard of them, They are NOT within an AliBaba / AliExpress / DHGate Site Based which is where the majority of our members shop at. There are Known Good Vendors here that we know of and it may be more prudent to go with that versus an "unknown with no history". Some vendors have limited US Stocks as well and they have presence on here with reasonably good reports about them.

Hope it Helps, Good Luck
Steve
 
Indefatiguable said:
I had read that I need a bms with specifically 16s, otherwise bms will detect non existent cells and trip out like a rich kid at burning man who forgot to hydrate.
Click to expand...

Any of the Heltec/JK BMS that supports 16 or more cells will do (for example that 24s 200A version). Just check the diagrams in that link that Steve posted. By the way, that Hankzor store is a good one at the moment - several people have ordered from there without issues.
 
Awesomeness thank you guys very kindly,
After reviewing the info directed to me here I've decided to pull the trigger on it. Since it'll be in a mobile application (and it's cheap enough) I'll probably order a spare as well thus assuaging any lingering durability issues.

Thanks again for all the info you all are lifesavers
 
Hey final thing, how do I tell how many charge amps bms can handle? Just realized I don't think I've seen that parameter listed anywhere... or is the "200a" for both charge and discharge?

OK now I'm freaking myself out lol. They can indeed charge and discharge simultaneously correct?
 
Awesome that is definitely good to know, so is it - for say a 200a unit - 200 charge 200 discharge? Or is it mixed as in 180a discharge 20a (simultaneous) discharge?

Project is an ev boat, definitely intend on occasionally using the motor while the sun is out. Sorry for the noobishness xD

Thanks in advance
 
Indefatiguable said:
Awesome that is definitely good to know, so is it - for say a 200a unit - 200 charge 200 discharge? Or is it mixed as in 180a discharge 20a (simultaneous) discharge?
Click to expand...

Think about it: if you're charging, you're not discharging. If you're discharging, you're not charging. Both at the same time doesn't exist.
The BMS can take 200A in both directions - but if you need a load that takes 100A, and you're 'charging' with 50A, you're just drawing 50A from the battery, the other 50A from the charge controller.
 
Ah. Interesting...

Right out of the gate, I really appreciate your time, thank you.

Now so I understand:

if I'm actively - consistently (for this convo, unchangingly) using the electric motor at an rpm that requires 180 amps - and (simultaneously) my solar array and mppt are producing let's say 20 amps charging current does that mean (as pertains to bms function) that I'm discharging 160 (net?) Amps from bank - or that I'm discharging 180 amps AND wasting 20 amps that would otherwise be charging?

Hence, can an incoming charge and an outgoing load exist simultaneously or are they mutually exclusive?
 
Indefatiguable said:
Ah. Interesting...

Right out of the gate, I really appreciate your time, thank you.

Now so I understand:

if I'm actively - consistently (for this convo, unchangingly) using the electric motor at an rpm that requires 180 amps - and (simultaneously) my solar array and mppt are producing let's say 20 amps charging current does that mean (as pertains to bms function) that I'm discharging 160 (net?) Amps from bank - or that I'm discharging 180 amps AND wasting 20 amps that would otherwise be charging?

Hence, can an incoming charge and an outgoing load exist simultaneously or are they mutually exclusive?
Click to expand...
I'm new to the forum, but not new to electronics.

If you have a motor that needs 180 Amps and only use a 200 Amp controller, how are you going to start the motor without blowing all of the output FETs on the controller? Or is your 180 Amps the maximum startup current of your motor? Normally, one would want at least 100% overhead on the current rating.

And just out of curiosity, what is your (huge) motor doing?
 
Indefatiguable said:
Project is an ev boat
Click to expand...
Ahhh, there it was. It's a motor. I'd probably go with 100% headroom or more with the odds of running a boat motor at full throttle for quite a while. Maybe a BMS rated at 300 or 400 Amps would live longer.
 
Hey yep took me awhile to reply. Yeah project is an inboard 48v dc motor for a big 18000lb liveaboard.

Using the old diesels power rating @ rpm vs new motors power rating (and amp draw) @ similar ram (after gearing) I'm fairly confident that a 60 amp draw will equate to a similar hull speed as the old Volvos 2000 "cruising" rpm.

Same prop, prop shaft but different gearing.

So motor startup for normal usage should be well inside that 100% overhead margin.

That being said every other component in the system is rated to 800a (for 1 min) output. So. I will have to rig the throttle not to go past a certain amount or some such.

I'm considering a 1000a rec bms just to have that extra power in an emergency (imminent collision avoidance, submerged shipping container, drunk jet ski etc etc etc) but total cost is ... more lol and I'm less familiar with the system.
 
Indefatiguable said:
Hey yep took me awhile to reply. Yeah project is an inboard 48v dc motor for a big 18000lb liveaboard.

Using the old diesels power rating @ rpm vs new motors power rating (and amp draw) @ similar ram (after gearing) I'm fairly confident that a 60 amp draw will equate to a similar hull speed as the old Volvos 2000 "cruising" rpm.

Same prop, prop shaft but different gearing.

So motor startup for normal usage should be well inside that 100% overhead margin.

That being said every other component in the system is rated to 800a (for 1 min) output. So. I will have to rig the throttle not to go past a certain amount or some such.

I'm considering a 1000a rec bms just to have that extra power in an emergency (imminent collision avoidance, submerged shipping container, drunk jet ski etc etc etc) but total cost is ... more lol and I'm less familiar with the system.
Click to expand...
48v * 60A = 2,880 Watts.
2,880 / 746 Watts per HP = 3.9 Horsepower, give or take.

You didn't say what size Volvo diesel you have, but I'm guessing it is more than 4 HP.
 
Well again the 60a number is supposed to equate to cruising speed. Was a md2b, rated 16hp max. Hand crank start. So yeah that's about right, maybe a tad slow but it's a baseline #.
 
I've mathed this out so many times before buying the motor kit, I'm pretty sure the guy at thunderstruck and I agreed that relative efficiency gains vs Volvo pretty dramatically reduced rated output requirements, to the tune of like 20%. I have the power output chart pdf somewhere. 60a cruising is a good baseline.
 
Yeah I just checked power graph.

Md2b rated 52 ft lbs, had 2:1 reduction. Cruised at 2000 engine rpms.

Hpevs ac-34, 1:1 gearing, rated 105 ft lbs / 70 amps @ 1000 motor rpms.

So yeah, 60 works as cruising speed. Tad slow, tad efficient.

Dam you for making me recheck my design lol ?
 
Indefatiguable said:
Yeah I just checked power graph.

Md2b rated 52 ft lbs, had 2:1 reduction. Cruised at 2000 engine rpms.

Hpevs ac-34, 1:1 gearing, rated 105 ft lbs / 70 amps @ 1000 motor rpms.

So yeah, 60 works as cruising speed. Tad slow, tad efficient.

Dam you for making me recheck my design lol ?
Click to expand...
It doesn't add up....
105 ft-lb torque at 1000 RPM is ~14,909W, or ~20 HP.
14,909W / 48V = ~311 Amps.

The PDF performance chart I found for that motor shows 460 Amps at 1,000 RPM, giving ~102 ft-lbs torque.

Somebody is reading current from the left side, not the right side of that busy graph....
 
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