Battery Care over Winter

This is a simple little project made in ½ hour from scrap parts I had lying around which I thought I’d share: The idea was to enable me to:

 

1) Partially discharge a fully charged e-bike battery to a suitable storage level for winter

2) Exercise the battery to extend its’ life when my e-bike batteries aren’t getting used much

3) Measure the true capacity of the battery

 

All this really involves is having a suitable load to drain the battery. I used 3 x 40-watt 12v halogen B&Q lamps I had spare. Wired together in series, this gives an ideal load of 120 watts for my two Phylion Lithium 36-volt, 374 watt, 10.4 amp e-bike batteries. The load is comparable to normal leisurely on-bike use: It’s neither too demanding for the cells, yet not so relaxed it takes ages to discharge. I added an on/off switch for ease and a 5-amp fuse for safety.

 

 

The idea came about simply because neither of my two e-bike batteries get used much over winter. Both are usually left stored at half-capacity after a ride. If the weather looks fair and I plan a morning ride, I’ll charge one/both to full capacity the evening before. If the weather then turns out to be truly horrible, I could be left with a fully charged battery that ends up not being used – perhaps for several weeks. Rather than leave the battery in this “stressed” fully charged state, an hour using this takes about 30% of the charge back out, 1¼ hours about 40% – perfect!

 

You can use a multi-meter to periodically check battery voltage, but the LED’s on the pack is probably enough to tell if the battery is at half-charge for storage, or near empty when the BMS should in any case cut-off the circuit when the cells are near flat before any damage occurs. Timing the battery over a full discharge gives you a good indication of what capacity is left in the battery: For me: A fully charged 374w battery / 120w load should take a shade over 3 hours if the cells are still performing as new (which they do seem to be).

 

 

There are probably neater ways of doing this, but for ½ hour time and a few spare garage bits, this works really well for me.

Those lamps are only nominally 60w. They could be wildly off, so you should be careful about making any judgements about the power or health of the battery other than it's working, but if you put a wattmeter between the lamps and the battery, you would get a reasonable measurement of its actual capacity and voltage.

 

The voltage when fully charged and at the cut-off point tells you the state of balance too.

 

https://www.ebay.co.uk/itm/100A-60V-DC-RC-Helicopter-Airplane-Battery-Power-Analyzer-Watt-Meter-Balancer-BG/292119038805?epid=1694235544&hash=item4403a6cb55:g:NrIAAOSwxH1UG-pp

Those lamps are only nominally 60w. They could be wildly off, so you should be careful about making any judgements about the power or health of the battery other than it's working, but if you put a wattmeter between the lamps and the battery, you would get a reasonable measurement of its actual capacity and voltage.

 

The voltage when fully charged and at the cut-off point tells you the state of balance too.

 

https://www.ebay.co.uk/itm/100A-60V-DC-RC-Helicopter-Airplane-Battery-Power-Analyzer-Watt-Meter-Balancer-BG/292119038805?epid=1694235544&hash=item4403a6cb55:g:NrIAAOSwxH1UG-pp

Yes, quite so... the lamps could be a little off their 40w rating. Rather than a dedicated watt-meter though (which I didn't have to hand) I use a Uni-T UT81B to measure voltage and current (measures up to 10A DC)... and these lamps do measure the rated 40w (+/- a very small margin of error). So it's pretty accurate as a simple, low-cost DIY discharger.

 

Yes, quite so... the lamps could be a little off their 40w rating. Rather than a dedicated watt-meter though (which I didn't have to hand) I use a Uni-T UT81B to measure voltage and current (measures up to 10A DC)... and these lamps do measure the rated 40w (+/- a very small margin of error). So it's pretty accurate as a simple, low-cost DIY discharger.

 

[ATTACH type=full" alt="Ebike_measure.jpg]22446[/ATTACH]

Appreciate that this is an old thread but interesting to me. I'm sure many expensive batteries would last much longer with some attention during winter months,.

Having read this I intend to build a similar discharger myself, I have ordered a discharge monitor to add in which will cut off at a predetermined voltage so that I can regulate the how far the battery is discharged.

........I have ordered a discharge monitor .........

Hi Ray - would you mind providing a link please?

 

Cheers, B4t

Hi Ray - would you mind providing a link please?

 

Cheers, B4t

No problem, I also bought a 22 ohm 50watt resister and I intend to make it so that I can switch in 3 or 4 lamps.

 

link to control

I did change that to 4 x 40w lamps: 12 x 3 =36v, and as we all know, a 36v battery charges to 42 v, so 3 are kind of over-volting a bit. The 4 lamps are still working.

 

I also did eventually add the wattmeter d8veh/vfr400 suggested; for a few quid, it's less hassle that putting a multi-meter in circuit, and gives you a lot of info inc. total/true battery capacity in Wh etc.

 

Those 2 old batteries in the above pic date from 2016 - they still measure 370Wh capacity. I cycle them once every 3 months or so as that ebike isn't used a lot as it's at a different location now.

 

For a few quid more (£10?), I was going to add a charge control board (switches charger on when voltage falls too low, and off at a user-set upper level - say 38v for storage). I didn't because those batteries don't use CanBus, so don't drain much at all on their own.

 

When you think about it you could really go to town: My idea was to keep it simple from crap I already had in the shed.

 

I'll look forward to seeing what you do.

Interesting to hear how well your system works, given the price of batteries it seems to be a sound investment.

Just waiting for the bits I've ordered to arrive then I'll set it all out and test it before I mount it on a board.

Two questions

Do you have a link to the watt meter you used? I've a fluke meter and a clamp ammeter but the watt meter sounds like a good idea.

The battery in your picture looks like the one on my halfords bike, which slots are the power output? I can't quite see in the pictures.

I also have a hopper shopper I bought for my wife but it has never been used so I will be using 24v and 36v batteries on my rig.

The wattmeter vfr400 suggested is the blue one here. It's worth using IMHO for the info it gives you, but especially total capacity over a full discharge.

 

Yes, they're Phylion SF06's, the same as Halfords Carrera but without the smart BMS's. The 4 centre slots are connected if you have the smart BMS, but it's always the outer two for +/- voltage.

 

I have three e-bikes and 4 batteries now - but you can't use them all at the same time. The occasional charge to full+balance, discharge, and partial charge to storage level again of those sitting most idle seems to keep everything working well.

 

I made a second simpler one too, just for draining a fully charged battery down a bit:

 

Cheers

I have ordered one, just need to have some time to set it up.

Bits all finally arrived, so I'm looking how to lay this out and mount on a board.

I intend to use one of the switches to interrupt power, and the other switch to cut in or out the fourth lamp, that way I can use with both my 24v and 36v batteries. I'm also wondering about feeding the watt meter and voltage control directly from the input and just use the power switch to connect the lamps.

I only used a 2-gang switch because that's what I had spare in the shed, and I only used any switch at all to stop sparking when connecting the lamps to the battery.

 

When I later added the wattmeter, because it was a 2-gang switch, one switch was used to disconnect the circuit completely, one used after the wattmeter to disconnect the load so the wattmeter (still powered by the battery) would retain it's values without then still applying the load.

 

So I guess for you, you can omit a main on/off switch as the wattmeter/lvc circuit on their own shouldn't draw enough to spark, and do:

 

battery - wattmeter - lvc - switch 1 - lamp 1/2/3 - switch 2 - lamp 4.

 

Switch 1 can be a 1-way, switch 2 would need to be a 2-way, but with MK, they're usually both the same - either 1-way or 2-way.

You highlighted my exact thoughts, don't want any sparking to damage the battery terminals and I would like to retain the watt meter readings.

Need to think it through and try to get it right, but these kind of projects seem to evolve and become modified.

At the moment I have rigged it up on a temporary basis to try the watt meter, in the next few days I will cut some board and make a better job.

So far I have spent just over £20 but I think it's a sound investment as i intend to use it to cycle my tool batteries as well as the bike batteries.

Bits all finally arrived, so I'm looking how to lay this out and mount on a board.

I intend to use one of the switches to interrupt power, and the other switch to cut in or out the fourth lamp, that way I can use with both my 24v and 36v batteries. I'm also wondering about feeding the watt meter and voltage control directly from the input and just use the power switch to connect the lamps.

A detail to watch for is the lamps themselves: halogens get very hot, so if to be left unattended, be sure nothing nearby can get dangerously hot.

 

Also, I like to have an additional lower value fuse in the circuit than the battery fuse, so any minor misdemeanors on my part have limited impact. 5 or 10A depending on what I have lying around.

A detail to watch for is the lamps themselves: halogens get very hot, so if to be left unattended, be sure nothing nearby can get dangerously hot.

 

Also, I like to have an additional lower value fuse in the circuit than the battery fuse, so any minor misdemeanors on my part have limited impact. 5 or 10A depending on what I have lying around.

Yes I discover that the lamp get hot, (ouch) that's when I nipped to toolstation and bought 4 of the ceramic sockets for them. I'm thinking of mounting the sockets on an aluminium strip, I am using an inline fuse which takes car type blade fuses 5 amp at the moment but may have to use 10 amp with the 36v batteries and 4 lamps.

I was all set to make the rig but it's freezing in my garage and I decided to order some soft silicon wire and do the final build in warmer days.

But I did a bit of a test rig, the kinder ones among you may call it a prototype.

It works fine and I can use it on 20v tool batteries 24v shopper battery or 36v batteries just by moving the blue wire to different terminals on the terminal strip which connects the lamps.

One design flaw I discovered is that the lamps are direct in your eyes and make it difficult to see the watt meter, need to look at that.

Let's call this one Mk 2

I am cycling my batteries to try and discover their true status, I suspect the temperature is playing a part in this

Thanks to [mention=16762]Ray Winder[/mention] and [mention=15833]cyclebuddy[/mention] for sharing their ideas on the battery discharger gizzmo and I've now 'knocked up' one for myself.

 

Here's some aditional details that might be useful to others and encourage greater takeup.

1. A basic schematic showing connectivity from the battery through the Watt Meter and Low Voltage cut-off device to the Load.
   
2. For my load I've used a 100w 18 ohm resistor which gets VERY HOT (around 270 degC). I used a resistor and that only drawing about 2A from the battery.
   
3. I put the switch 'after' the watt meter so that I could disconnect from the load without powering down the watt meter and loosing all the recorded data.
   
4. Setting up the low voltage cut-off device (XH-M609) required a bit of internet searching to work out how to do it - the youtube clip
   was useful in this respect. In summary:
   - by default, the display shows the input/output voltage (they are the same value as the switching is done via a relay)
   - setup is done through the the two push buttons marked '+' and '-'
   - the are 4 settings:
   (1) calibrate the display voltage reading against an external meter.
   (2) set the low cut-off voltage
   (3) set the off-set voltage for the device to switch back on, e.g. if the cut-off voltage were 30.00v and you wanted the device to switch back on at 32.00v then you'd set the off-set to 2.00v
   (4) this is a time delay between the when the 'back-on' voltage is achieved and the device actually switches on. Values are 0-5 but I don't know what exactlythe units are but '0' is no delay and '5' is arond 30s.
    
   To access:
   - Calibration - long press of '+'
   - Low voltage cut-off - double click the '+'
   - Offset - double click '-'
   - time delay - long press of '-'
    
   Once into either of the above, use the +/- to adjust the value. Once the value is reached, leave the buttons alone and after a few seconds the display returns to the input/output voltage.
    
   That's it - be aware that the press buttons are cheap items and so may not always registers presses
   
5. The schematic:
   
6. The 'Heath Robinson' item!
   

That will do the job, I used two switches one between the inlet power and the watt meter to avoid any possibility of a spark when connecting the battery.

The other switch is between the load and the voltage cut off , to disconnect the load while keeping the watt meter live.

The small halogen lamps provide a load just under 4 amps which falls off slightly as the voltage sags when approaching full discharge.

I tried a resistor as a load but I didn't like it getting too hot so I settled on the lamps which don't ge quite so hot.

Hi [mention=16762]Ray Winder[/mention] - I agree that the halogen lamps are a better idea rather than the concentrated heat from the power resistor. If I can find a source of resonably priced 12v halogen lamps, I shall probably go that way. I might pop to my local car scrappy and get some car headlamp bulbs .

I bought these : lamps link

But you may find cheaper, I also bought ceramic holders from tool station they were less than 90p each.

Using four in series ups the resistance and lowers the amps drawn from the battery

I prefer my switchable 26/52 ohm resistor in its metal, well ventilated box. No chance of unintended fireworks if left unattended.

I may be oversimplifying things, but I just bought 'normal' low-voltage incandescent bulbs in 100 watt and 60 watt power ratings. I made up a battery holder wired to a standard 13 amp trailing socket and I connect an ordinary lamp fitting to that.

 

https://www.lamps2udirect.com/standard-incandescent-light-bulbs/48-50-volt-60-watt-bc-b22mm-clear-low-voltage-gls-bulb/144680

 

After all the dire warnings about power losses following the recent storms, it's quite handy to have an emergency light source too.

I am my own dis-charger

 

The cost of replacing the 400Wh Yamaha battery on my 2015 Haibike incentives me to look after it as well as possible.

 

On those reasonably rare occasions that I have fully charged the battery and something happens to prevent me riding, I will at the earliest opportunity and certainly the same day ride the bike to a steep hill a few hundred yards from my house with a roundabout at the top and the bottom and ride it up and down to take 20 to 30% out of the battery.

 

I do this by using the maximum assist and letting the bike as much as possible do the work. I can reduce the battery down to a safer storage level surprisingly quickly, probably about a half an hour.

 

It helps that I live close to a steep hill.

 

The rules I have followed to look after this battery are pretty simple.

 

Always bring the battery into the house to store

 

Store it at around 60% capacity plus or minus the odd 10%

 

Fully charge the battery before you use it, but as close to when you plan to use it as possible.

 

Try to use your bike regularly, however my battery has on occasion been stored for around 6 weeks + or - without being used.

 

My battery will be 7 years old in around a weeks time and still works very well and I have so far ridden my 2015 Haibike Yamaha 15,230 miles.

 

However having said all this the silver fish battery on an old 2011 rear hub bike I use a lot lives on the bike in my unheated garage and is always ready to be used fully charged.

 

The last battery I bought for it was a relatively cheap (under £200) Yose one of Ebay and although I can tell that battery is losing some capacity it still works well enough and is now four years old. I use a timer plug so that the power is cut to the charger after a set number of hours.

 

I do use that bike pretty much daily for shopping trips and many other errands, and it is so convenient to know I can just jump on it whenever I need to, and simply plug it back into the charger/timer plug on my return before going into the house with my panniers.

 

So for me the expensive battery gets really well looked after and the cheaper one just gets used.

I am my own dis-charger

 

Ha ha, there's nothing better than keeping things simple - it get's my vote for sure.

 

However, although not an essential, I'm an inveterate tinkerer and couldn't resist the discharging gizzmo as I'd like to measure my Amp Hours as of now and maybe over time to see how (my cheap) battery is holding out.

 

I recently experienced a battery problem and I thought the battery might be knackered but it turned out to be the BMS - if I'd had the 'discharger' at my disposal then, I'd have found the BMS issue somewhat sooner than I did.

 

PS - the 18ohm 100w resistor in my device listed above, went open circuit today. I guess I was pushing my luck at running at 276degC!!! - onto plan 'B' but that's all part of the fun of it .

 

Thanks to those who have pointed me towards affordable lamps, but I'm sticking with resistors for the mo as halogen lamps are getting increasingly harder to find at reasonable prices. So this time around I'm spreading the heat dissipation across three 40 ohm resistors in parallel on a better heat sink and thermal paste.