Looking after spare batteries

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jamesengland
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Looking after spare batteries

Can someone please advise me of the best way to look after spare NiMh cells? Whilst the batteries on my Vectrix seem fine, I was wondering about buying some spare cells, just in case I find some of mine have overheated or swelled up or whatever. But, of course, I don't want to get some and end up ruining them by incorrect storage (can they be stored for any length of time?). Each cell is 3,2v, right? So, I was wondering if spare cells could be made into blocks of 11 cells, making 35.20 and topped up occasionally with a 36v battery charger? Or maybe each cell charged individually?

I'm planning on testing all the cells on the bike to see if there are any obviously damaged ones. What would the test for each cell be using a voltmeter, then? Is it possible to establish whether a cell is dud by using a voltmeter?

All contributions to my steep learning curve appreciated....

LeftieBiker
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Re: Looking after spare batteries

I wouldn't charge them in large blocks - that's one of the big mistakes Vextrix made. Individually or pairs would be best. With no parasitic drains NiMH cells tend to 'level off' at a low SOC, but I don't know for how long they are stable that way. (I have no Vectrix, just some knowledge of NiMH cells.)

Mik
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Re: Looking after spare batteries

I would probably store them without anything connected, e.g. no temp sensor wiring harness. You can leave them in 8-cell or 9-cell modules.

Charge them to 40%SOC (12Ah) and store them at an even temperature below 30degC if possible. Cooler is better.

They should last well over a year without needing a topup charge.

They will need a few exercise cycles when put back into use.

Look up http://batteryuniversity.com/

This information may be used entirely at your own risk.

There is always a way if there is no other way!

Spaceangel
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Re: Looking after spare batteries

jamesengland
I seem to lost you on bats? 3.2 volt for NiMH? Are you talking about Lithium? I also thought VX-1 pack came in pack modules of 8 and some for 9 cells in a module. My scoot needs a charge every three weeks in winter but spare pack seem to hold a charge for many months. I test the two 9 cell module with my laptop which need 18 volt to operate and try to discharge the two modules and it last me all day on my computer vs maybe an hour or so driving a VX-1. I charge my spare module with Tenergy NiMH charger and put away module for another 3 or 4 months. I guess with James and England you are from Old England vs my New England across the pond. I think if it wasn't for a computer in VX-1 sucking precious juice from 125 volt pack it would last months vs the 3 or 4 weeks it takes to kill battery pack. Maybe you do have 3.2 volt modules or cell but NiCads and NiMH has a range of 1.0 to 1.3 maybe as high as 1.35 or 1.4 volts? But if you have Nickel type of cells it can't be in the threes, and Lead is in the 2's and Lithium will be in the 3's..

Each cell is 3,2v, right? So, I was wondering if spare cells could be made into blocks of 11 cells, making 35.20 and topped up occasionally with a 36v battery charger? Or maybe each cell charged individually?
So the modules are banded together in blocks of 8 or 9 so I think it be best to keep them banded together. So do you have a module? Or do you have some individual cells? Mine are pefectly balanced at 1.25 volt each cell. If you have individual cells just hook them up in series and charge them at am amp or so and measure voltage of each cell. I bet they will be about the same as it reaches full voltage of 9.6 or 10.8 ->12.15 volt for 9 cell pack. If a cell is dead or weak it will be highly whacked. either go short or something in between. rarely do they open up and go to high volts.

KB1UKU

antiscab
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Re: Looking after spare batteries

I normally discharge spare nimh batteries down to 0.9V then store them as is (with nothing connected)

that way I don't have to cycle them at all when I put them into service, and I know exactly how charged they are (0% SOC)

Matt

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km

doctor_of_music
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Re: Looking after spare batteries

Actually this discussion has reminded me that I have a complete NiMh battery pack, removed due to an upgrade, cluttering up my garage, in the UK.
It looks very much like this: http://www.owlhouse.f9.co.uk/vectrix_nimh_battery_pack.jpg

I'm unsure what to do with it at the moment. The pack had failed, but of course it's likely the vast majority of the cells will be OK. I'd be happy to break it up, and test the cells (when I have the time) or consider letting the whole lot go. Either way shipping's a problem (weight, and courier's restrictions) also I really don't know what would be a fair price to ask for single cells or the whole pack.

Just thought I'd mention this though – I'm in no hurry, and as the batteries aren't connected to anything, they shouldn't be discharging significantly at the moment. It may be a while before I have time to dismantle & analyse each cell. And at the moment it's freezing out there(!).

Mike.

wookey
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Re: Looking after spare batteries

Normal small nicad cells can be quite happily left discharged for years (unlike lithiums, and lead acids). I don't know if the large format ones that the vectrix uses are different in this regard. This is on of the good features of NiCd/NiMH - immunity to occaisional use and being left flat.

Wookey
Sakura s50 (Efun A)

antiscab
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Re: Looking after spare batteries

Normal small nicad cells can be quite happily left discharged for years (unlike lithiums, and lead acids). I don't know if the large format ones that the vectrix uses are different in this regard. This is on of the good features of NiCd/NiMH - immunity to occaisional use and being left flat.

lead acid is the only chemistry that can't just be left on a shelf somewhere

for both nimh and nicd, I would go further to say it is necessary to store them discharged to avoid the lattice effect

For lithium, it makes no difference what state of charge they are stored at
I have cells I put on my shelf 3 years ago that still behave the same today as they did back then

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km

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