Poor man's monitoring...

[staft]

As a noob trying to learn without repurchasing everything, I am hoping for advice from those of you who are way down that road. I am trying to do this on the cheap, and a CA seems like a bit too much for my basic needs. So what would be the minimum I would need to monitor the charge of a 48v 10ah headway pack? On-bike would be good, but if that pushes the cost too high I can live with stay-home. I don't own a multimeter - should I start there? Models?

Watts up, wattameter, cell log 8's, ebay votage alarms - I have read about them, but am not really clear on what I need as a minimum. I know I will someday grow into a need for more, but what is a good place to start?
Thanks, as always.

 

[wesnewell]

You don't really *need* anything if your pack has a working bms. It should protect the pack. If you don't have a bms, then the controller LVC should shut off when voltage gets too low if the lvc is appropriate for your pack voltage. I use a led voltmeter to monitor my lipo pack voltage. Everyone that owns an ebike should have a vom to test with. When i first switched to lipo I didn't use anything except my brain. My controllers LVC was too low to protect the pack. After a couple of months I got a HK-010 wat meter from HK. When I started going to voltages over 60 I used a voltmeter that I got on bid for about $5 shipped.
http://www.ebay.com/itm/LED-Digital-Voltmeter-DC-15-120V-Red-Motorcycle-Waterproof-Voltage-Panel-Meter-/130694853453

 

[staft]

Thanks - very useful. Please pardon my ignorance, but where is the correct place to wire this volt meter? Is one good for the whole pack?
Also, VOM or DMM - does it matter? Is cheap acceptable?

 

[dogman dan]

A voltmeter would be the minimum. If you have a harbor freight store nearby, their budget model often sells under 5 bucks. Cut the probes off the wires from it, and attach to the same plug where the controller plugs in. So when you plug in the battery, you see how many volts you have. keep it above 48v idealy, you'd be charging it to about 58v, and see 52-56v most of your ride.

Other altenatives abound. I just bought a couple cheapo led voltmeters off ebay. Eventually they will come from china, I think they boat shipped em.

Since your pack has 16 cells, it would be quite nice to monitor each cell individually. Two cellog 8's, and some wiring, and you could have that.

But as said above, if you have a bms you trust, you can ride naked. With experience, just an odometer will give you a good idea when you will run out. I used to do this, but once I got a CA I got to really liking having real knowlege of my voltage, as well as a better way of estimating how far I can still go. Once you have a watthours per mile average on your dash, you really do know exactly how you are doing on that days conditions. Very nice when touring, not so needed on a well known daily ride.

 

[dogman dan]

The voltmeters came in. Not too bad for monitoring the difference between 56v and 48v. One reads .1v diffeerent than the other, so don't get 16 of these to monitor cell level. Definitely hard to read the display in sunlight, but they can be read if you stop the bike and shade it with your hand enough.

Decent enough for those on a budget, small, and cheap.

 

[999zip999]

We need to know the answer are you going to run a bms ? Where are you going to get the pack from ? And what are you going to run ?