Time to put the bike away..1 question..

M

Mudduck

10 W
Joined
Jan 25, 2012
Messages
92
Location
South Jersey NJ
Hey guys,first I just want to say thank you all for helping me with my first year with my ebike..I love my last kit the 7-t Mac is great..too my question how should I store my a123 battery for about 3-4 months..should I leave it on my slow charger?thanks.
 
Agreed. Store in a cool, but not really frozen place if possible. Disconnect the bms.

Personally I'd rather store it closer to fully charged just in case somehow a teeny tiny trickle discharge exists. But perhaps not completely full.

DO check on it from time to time. After a week, then two. then three. If nothing is dropping in voltage then longer intervals. If a cell seems to want to drop a lot, charge it again before it's too late.

Very unlikely to have anything going on, but checking on it a few times beats the hell out of ignoring it for several months and then finding out too late a cell discharged itself somehow.

The other approach, store fully charged with a bms connected, but better top it up about every two weeks. I do this now that I seldom ride due to my poor health. But I want to be able to ride anytime I do feel like it, and just try to take a spin at least once every two weeks. In my climate, riding in January is still quite comfortable.

During storage is the time to add modifications if you have any in mind. Very convenient to have some extra 8s jst plugs spliced into the sense wires so you can check each cell very quick and easy with a cellog 8, for example.
 
deleted because i misread :oops:

store it fully charged and disconnect the battery
 
dnmun said:
no, just disconnect the sense wires after draining it down a little from full charge. i think the recommended level is around 60% SOC.
Click to expand...

I agree with Dnmun, not the others. It's a LiFePo battery not a LiPo. So storage voltsge should not be 3.85 since that is above full charge voltage.

As Dogman says check them a few times for a month if it's lower tha it was charge it a little to bring up the low cells. About 3.4 for a LiFePo.

Make sure you disconnect the bms while it's sitting in storage.

Dan
 
My only problem is that the bms is shrink wrapped..the battery is made by cellman..John in cr..I will try to ride when I can,here in nj I go to work at 8am and come home around 4:30pm..it's dark when I leave for work and dark when I come home and around 35-45 degrees..
 
I have my spares for cross-country stored at middle-volt inside the house where the temp does not swing far. Since I didn’t ride this year, I gave them a little top-off, but they held a good charge… not dropping more than 0.5V from where I left them; let me explain: I keep them unified in series as 15S, so when I say the only dropped 0.5V - that's impressive. The reason why I picked middle-volt is because that’s how HK ships them.

That said, I keep my Commuter topped-off ready to go so I can bolt to a client with < 2 hours’ notice if need be.

I ride year-around. In the winter, I swap out to studs. This year will be a little different cos I’m running wider rims, so I won’t be able to install the Schwalbe Marathon Winters. Instead I have Schwalbe Ice Spiker Pro on the front (26x2.35) and the Panaracer Fire FR (24x2.4) knobby on the rear. Today I was looking at studs, and found two new suppliers which I added to the Rims & Tires Reference: It’s probably the same supplier – but there’s a scooter stud that has a shallow penetration useful for us ebikers, but – it’s wicked spendy… like $100 for 100 studs + another $10 for the tool.

I counted the number of block-sets on the Panaracer and there’s 36 of the same pattern, so my thinking is to get the 100 studs, and put 36 on each side (alternating) – so that the center of the tire is clean, but the edges will grip on cornering. The FWD Schwalbe has a monster 361 studs, so I’m not too terribly worried about losing traction. I just a bit more bite out of the rear.

Anyways... I hope your bike doesn't get used to being stored for too long :wink:
Stay safe, KF
 
I recommend you store it indoors where it is room temperature and avg humidity levels.

but more importantly
store at ~50% SOC (my company stores our LiFePO4 cells at 40%)

i strongly recommend against storing at anything near 100%SOC
We store batteries regularly at my work and it well known that storing them at high charge decreases their capacity over time.
 
Thanks all..I don't mind riding to work in the cold but I also work outside in the cold weather all day too..I'll bring the battery inside the house and drain the battery a little..
 
you have to disconnect the sense wire plug from the BMS. the battery doesn't like to have the stress of full charge so the less time it sits there under stress the better. so drain some charge off, not too much, but you have to disconnect the sense wires or they will drain the battery while it sits.

once the sense wires are disconnected, it will hold the charge until you get back to it next year. for lifepo4 cells.
 
Ok, last attempt:

The BMS is ALWAYS drawing power from a group of 3 or 4 cells (or cell group) in your battery. Not much, so let's say 30mA or 0.03A. Let's assume that your battery capacity is 15Ah.

15/0.03 = 500hrs = 20.8 days. So if you forget to recharge your battery for three weeks you would end up with 3 or 4 dead cells (or cell groups). To fix it, you have to open up your battery, cut the shrinkwrap, disconnect the BMS, unsolder the dead cells, buy new replacement cells, solder them back in and reconnect the BMS.

If you forget to recharge the battery for only 10 days, those cells are discharged by 50% creating a huge imbalance with the rest of the non-discharged cells. Your BMS would quit working and you can't recharge the battery. So you have to open up the battery, cut the shrinkwrap, disconnect the BMS, manually recharge the low voltage cells and reconnect the BMS.

Edit to add: I don't know your battery capacity, I don't know your BMS. So the 30mA and 15Ah numbers are just numbers used for the calculation.
 
I left my A123 battery (from Cellman) for about 5-6 weeks at about half charge and the voltage barely dropped at all, with the battery still strong afterwards.

I'd say charge it to 50% and remember (set a reminder in your phone or whatever) to top it up a little once a month.
 
atcspaul said:
i am with you john gonna ride all year :lol:
Click to expand...


I just noticed that of the 2 guys who said ride your ebike the whole year around, one lives in Paradise and the other the US Virgin Islands. :mrgreen: I am pretty sure that there is no snow in either location, as it would be quite perverted to have snow in Paradise. :D
 
Disconnect it anyway, UNLESS you have proven to yourself that your bms, with your wiring, and anything else unknown about that could be causing a tiny trickle of discharge is not discharging the battery.

Repeating it again, store the battery at the voltage you find best for your needs. 6 month storage at lower voltage makes some sense. If the riding seaosn starts 2 months from now, that's 2/3 less damage from storage. Those of us riding year round never store any way but full charged, and still get 4 years from lifepo4. I'm not scoffing storing part discharged, just saying that if something is causing cells to discharge, you get damage sooner. So find out if your pack holds voltage in storage or not.

THE MAIN THING, is check it once in a while. Don't just ignore it till easter eh? After a few weeks of monitored storage, you will have evidence that you do or do not need to recharge it some monthly, or yearly, or whatever. Time will reveal it if you have a cell that likes to self discharge a bit, or the bms or some other trickle is discharging the thing.

If all is good, discharge it some and store it. If the thing needs a full charge weekly, then do that.
 
after reading what sam said, i was thinking how the idea of the BMS circuit current being taken from the first 4 cells on the ping signalab, and now it looks like some of the new chinese limn2o4 BMSs use the circuit current for the digital controllers from the first 3 cells.

but the BMSs from Vpower and from BMS battery and the others we see on alibaba all take the circuit current that drives the mosfets from the top of the battery.

that current is regulated through a diode to drop it to the voltage that can be used by the transistors that drive the output/charging mosfets. those components all hide under the black goop.

that circuit current comes onto the BMS through the point that says P+ and B+ on the BMS. that is where people normally would connect the positive lead of the battery to the positive lead to the controller.

but it is not essential to bring the full size cable from the battery all the way back to the BMS and then send it out to the controller from the BMS. in fact having high voltage near the BMS increases the risk of shorting the pack to ground and creating a fire.

so i was thinking that if one was to remove the B+ and P+ cable from the BMS, and instead just bring the circuit current for the BMS to that spot using a small wire then you could put a switch in that small wire and when you turn off the switch, then the circuit current to the BMS would be cut off and the BMS would be shut off. this would also turn off the battery so it could be handled safely too.

so for those types of BMSs that do not take there circuit current from the lower 4 cells like the ping signalab, maybe it would be a useful adaptation to use just small wire with a switch and then turn off the battery by turning off the BMS with that switch. then you could avoid the hassle of building the precharge spark elimination techniques because you could then have the battery turned off when you make the connection to the controller and when the BMS was turned back on the current surge would be through the output mosfets which can handle it easily.

the added benefit is that the circuit current would be turned off when the battery is in storage, just as when you disconnect the sense wire cable on the signalab. the other benefit is the reduction in the risk of fire from having the positive lead from the battery running into the BMS. in fact the small lead that carries the circuit current could have a small 500mA fuse in case it was accidentally shorted and since this risk of shorting is the main reason for using the large 40A inline fuse, then maybe it would be reasonable to remove the large inline fuse to increase the quality of power delivered without the heating in the fuse holder from the contacts that have to carry all the current.

so for some batteries, just removing the sense wire cable for the winter would not work unless the connection to the B+ on the BMS was switched off too. the comparators on the individual channels of the BMS only use microamps of current so that is a no op in terms of storage imo.
 
dnmun said:
so i was thinking that if one was to remove the B+ and P+ cable from the BMS, and instead just bring the circuit current for the BMS to that spot using a small wire then you could put a switch in that small wire and when you turn off the switch, then the circuit current to the BMS would be cut off and the BMS would be shut off.
Click to expand...

The problem is people don't want to open up the battery, don't want to cut a wire, don't want to add a switch. And they shouldn't have to. The practical solution is for the battery builder to include a switch accessible from the outside to turn off the BMS. Label the switch properly with a friendly reminder like this: "Turn off your BMS for storage unless you want to make me richer X months from now. Sincerely. Signed: Your Battery Provider."
 
you don't have to be a jerk and insult the guy because he asked for advice on how to take care of his battery during the storage.

maybe sam can convince the chinese BMS makers to do his bidding but he doesn't believe in using a BMS anyway so i don't think it is relevant.

remember the BMS is there in order to make a battery usable by the 10's of millions of chinese who use electric bikes now with lithium batteries. the BMS is there to protect the battery and the manufacturer would be negligent to produce batteries that would fail when discharged because most of the these people just need something that is turn key and they don't have to understand or baby their battery to keep it alive.

the people here on the sphere are rich enuff they can afford to buy a new battery when they ruin their battery from using it without a BMS. which is where the separation really lies, rich white guys with money to blow and poor chinese who prize their electric bike or scooter as their most valuable possession.

i think the idea of using a switch on the B+ lead to the BMS on these more common chinese BMSs is worthwhile so that was why i yakked it up. if you don't use a BMS then it is of no interest to you. it solves the precharge problem and also inactivates the battery during storage. somebody should try it and do a thread on it so it can get wikified.
 
dnmun said:
maybe sam can convince the chinese BMS makers to do his bidding but he doesn't believe in using a BMS anyway so i don't think it is relevant.
Click to expand...
dnmun: You're partially right. I don't believe in using a BMS. But only because current BMSs are not helping. FWIW here are my issues with current BMSs:
1) partial voltage draw. I find it hard a accept a device that continuously creates an imbalance while claiming to be a balancing device.
2) balancing by bleeding the high voltage cells instead of boosting the low ones. Slow and wasteful.
3) I don't want a BMS to monitor the LVC. My controller is already doing it. My CA is already doing it. Albeit not at the cell level.
4) I want the BMS to be active only during charging.

I would love to own and use a BMS that actually helps.
 
I don’t use a BMS. Bought a kit, but never assembled it.

I know how to manage my pack well-enough after the first year of hard failure.

I consider my batteries to be quite tough and rugged; I’m not worried about a little over or under charge after seeing what they went through on the first road trip to California. Consider I have 84 lipos of the exact same time, and after 3 year, only 6 are completely dead… I’d say that’s pretty good performance.

What I want my BMS to do is passively balance the pack during or after charging. If I can have a balanced pack – that’s more miles for me down the road. Otherwise I might have a hot & greedy cell that throws the overall voltage askew and the charger shuts down too early.

So that’s my goal and project for next year – not so much a full-fledged BMS, but rather a real balancer. I prefer it not be a bleeder, I prefer that it manage the finishing charge, the final top-off by PWM through the balance wires cos at that point – current will be quite low. That’s really what I want Santa to bring me this holiday:

Gladness with a happy balanced pack, along a warm cup of cocoa with marshmallow bits :pancake:
~KF
 
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