New batteries won't charge - Jetson

[mickand]

My 2 new Jetson batteries won't accept a charge - existing battery charges fine with same charger. I suspect both are really flat and the BMS won't allow a charge.
Batteries have 5 terminals, +, -, and 1,2,3.
Can the BMS be awakened with a voltage applied to the battery?

 

[Smaug]

What do you get when you measure DC voltage from + to -?

Is there a power switch, by which you need to turn on the batteries first?

Any instructions provided that you can check?

 

[mickand]

My meter only reads 12v - no voltage shown even on my fully charged good battery. Batteries are switched and 'on'.
No instructions supplied with the batteries. They were bought from a reputable supplier on eBay as Jetson had none in stock.
When plugged in to the charger, the red charging light comes on for about 2 minutes and then turns to green, indicating fully charged.
Install in the bike and all 4 LED power indicating lights come up as very dim and then fade to nothing, indicating a flat battery.

 

[Smaug]

My meter only reads 12v - no voltage shown even on my fully charged good battery. Batteries are switched and 'on'.

It may be that some of the other terminals need to see certain states to electronically enable the battery discharge terminals. That makes it hard to test, but it makes them less of a fire hazard in case of a battery terminal short circuit.

The aftermarket battery mfr may not know what signal the charger or bike controller is looking for.

...Or the bike mfr. changed it to discourage the use of aftermarket batteries.

 

[mickand]

In theory, they are genuine Jetson batteries.

 

[m@Robertson]

@mickand your original guess on the packs being down below the BMS threshold is not uncommon. I know of this happening quite a bit in a user group I am a moderator on, and your fix of applying voltage directly to battery terminals (you'll have to crack open the battery case) is the standard, don't-do-this-at-home-kids solution.

Obviously you need to know wtf you are doing and even if you do, there are safety risks.

Also I have never heard of this being done to a Jetson battery. So dunno how you would go about opening the pack and safely re-closing it after safely manually juicing it up.

AND... if you are reading 12v on a 36v battery, that is ridiculously low. If its a 36v, 10S pack, that means it is supposed to be 42.0v on a full charge, and 30.0v on a ZERO PERCENT charge. You are less than half that. Recovery isn't a given.

 

[major masingil]

Mickand when you plug the suspected full battery in and it fades quickly; do you see the charge level decline as the battery would when it's being used or does it just fade away with all charge bars staying like it's full?

When you said your multimeter only measures 12v, did you mean that's all its capable of measuring, or that's the measurement your meter provided? If its the former, you need to invest in a multimeter that you can use to measure voltage higher than 12v if you want to troubleshoot your ebike. I recommend getting one that measures continuity and resistance

 

[mickand]

Thanks for the replies. For clarity my meter shows zero volts when connected to any of my 3 batteries. It only measures voltage up to 12 volts, so probably won't recognize a higher voltage.
The charge bars fade from a dim 4 bars to zero as if the battery was full,.

 

[major masingil]

Klein Tools CL120 Digital Clamp Meter, Auto-Ranging 400 Amp AC, AC/DC Voltage, Resistance, Continuity, Non-Contact Voltage Tester Detection https://a.co/d/6WocyKx

Here's a versitile multimeter at a decent price. You can find them less expensive but still capable of most measurements.

 

[rustyron]

Thanks for the replies. For clarity my meter shows zero volts when connected to any of my 3 batteries. It only measures voltage up to 12 volts, so probably won't recognize a higher voltage.
The charge bars fade from a dim 4 bars to zero as if the battery was full,.

Have you checked the output of your charger? Just asking.

 

[mickand]

Yep - the charger charges my one good battery to full.

 

[rustyron]

Are the voltages the same? I have 2 chargers and one doesn't seem to charge as fast. I have a 10 amp and a 23 amp batteries.

 

[danhunt56]

Thanks for the replies. For clarity my meter shows zero volts when connected to any of my 3 batteries. It only measures voltage up to 12 volts, so probably won't recognize a higher voltage.
The charge bars fade from a dim 4 bars to zero as if the battery was full,.

Obviously you need a different meter, in all my years I have never seen a max 12 volt meter, wouldn’t even be good for 12 volt batteries as they are above 12 volts.

 

[danhunt56]

My 2 new Jetson batteries won't accept a charge - existing battery charges fine with same charger. I suspect both are really flat and the BMS won't allow a charge.
Batteries have 5 terminals, +, -, and 1,2,3.
Can the BMS be awakened with a voltage applied to the battery?

Will the seller take them back? There is a good chance they aren’t repairable. “New” batteries that don’t charge in my experience aren’t new, they have likely sat for years uncharged, making them new old stock which doesn’t work for batteries. I bought a factory made e-bike that sat for a long time in a warehouse before shipping, like two years, it was good enough that the charger responded, but it wouldn’t take a charge enough for the controller to turn on. The battery had to be replaced.

That said I did recover a 12v motorcycle lithium battery by opening it up and hooking the charger to the battery side of the bms and the positive terminal. This bypassed the bms and the cells charged to the point where I could finish it off through the normal terminals that went through the bms. I would not do that to newly purchased batteries unless I had to.

 

[Rawly Old]

My 2 new Jetson batteries won't accept a charge - existing battery charges fine with same charger. I suspect both are really flat and the BMS won't allow a charge.
Batteries have 5 terminals, +, -, and 1,2,3.
Can the BMS be awakened with a voltage applied to the battery?

I'm just glad this is not my problem, but with a certainty something else will be eventually.

 

[RoostChucker]

If your problem really is a low voltage condition on your new batteries there is a well known hack... BUT you absolutely need to check with a multimeter first, for all you know they sent you a fully charged battery with a different voltage. Are you sure they aren't supposed to be wired up in series? Batteries set up in series multiply the voltage.

Go buy a new multimeter from Harbor Freight for $5 and it will read the higher voltages and last you a lifetime.

If the new battery is super low, as you suspect, it won't charge for your own safety!

The hack goes like this - - > The way to cheat this charger safety feature on 12V car batteries is to use jumper cables and a second known good battery (with a charge on it). A cheap jump pack usually works too. Typically a 12V battery won't be recognized by a modern battery charger if the voltage drops below a certain threshold. I believe its a safety thing to prevent shoving a 14V charge into a smaller size battery like a 6V battery for example. The charger has no idea what you plugged it into. This is to prevent fire, explosion and chaos... etc.

The same technique may work but it hard to say with the BMS, but I've even resurrected rechargeable AA batteries with another AA battery.

If you have one battery of the same voltage you use some appropriate sized wires (I'd recommend 12 AWG wire or better) and put positive to positive and negative to negative and let it go. After a few minutes you should have enough of a charge in the new battery for it to be recognized by the charger and it should charge your new battery the rest of the way.