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Old 08-07-2017, 03:58 AM   #1
hartvige
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Default Radio board deep discharge of rear I2/X2 battery: Idea fox fix

I got bitten by this issue yesterday and ended up with a dead Segway, even though I had been trying to follow the discharge state of the batteries by regularly powering on the segway and checking the charge level on the InfoKey. Fixed it by manually (external power supply) charging the rear battery to around 65V (it was around 10V initially), then sticking it onto the SegWay and letting it fully charge there.

However, I got an idea for improving the segway which I wanted to float here. The idea would be to modify the machine so that the radio board is powered through two diodes, one from each battery, instead of being directly connected to the rear battery only.

This would provide many benefits. First of all, it would mean the batteries (when idling in storage) are balanced by the quiescent current of the radio board - the battery with highest charge will supply the radio alone until they are even, and then they will in parallel supply the radio from there on. Secondly, this means the InfoKey battery indicator would (if monitored every month during storage) show the actual state, allowing one to recharge the batteries regularly, trying to keep the charge around 50% to maximize battery lifetime. Thirdly, if forgotten, it will now take the radio board twice as long before fully depleting both batteries.

Any comments/suggestions?

Does anybody have schematics or wiring diagrams, or is it easy to find the connection path from the rear battery to the radio board (and the optimal interception point) once you start poking around?

A second step that would improve the situation even more would be to add a low-voltage cutoff circuit on the path from the output of the two diodes to the radio board, so that a voltage of 60V or so would completely shut off the power to the radio board and reduce current draw to essentially zero. But this is more complicated to do, and might be unnecessary once the diodes are added and if you remember to check the charge level regularly.
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Old 08-07-2017, 10:39 AM   #2
Don M
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The mod I would like to see done . . . . which makes even more sense to me . . . . would be to install a switch so you could power down the radio board when the Seg is in storage - Switch it back on when you get ready to use the machine

I know from personal experience that Seg batteries will sit for many months without losing their charge when they're not on the machine. I've gone 6 or 8 months and I'm pretty sure a once per year 'top off' charge would be all that's needed . . . . *if* the radio board wasn't sucking them down

I have no idea why a key switch to shut it down completely wasn't included in the original design - It seems like an obvious solution to me

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Old 08-07-2017, 01:14 PM   #3
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Why no radio switch might be answered with the owner's use pattern they were designing for with these?

Disassembled awaiting sale from the store to the owner, then assembled in the hands of the owner who uses it regularly, was likely the way Segway thought it would be use.

A radio switch would just be another failure point and potential cause for accidents. Furthermore, a switch would hurt the design aesthetics. So advanced they don't have an off button

The minipro has a button but I bet a key fob simply couldn't be implemented in the build budget.
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Old 08-07-2017, 08:09 PM   #4
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Quote:
Originally Posted by hartvige View Post
The idea would be to modify the machine so that the radio board is powered through two diodes, one from each battery, instead of being directly connected to the rear battery only.

Any comments/suggestions?

.
Certainly possible - although I suspect that a bit of additional circuitry would be required to drop the battery voltage to what's needed to power the radio and, of course, the circuitry from the rear battery would have to be modified to compensate for the voltage drop across the battery.

Of course, just keeping the Segway on AC power (with a timer to only apply the power for a few hours each day) would eliminate the "problem" without any modifications.


Quote:
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Any comments/suggestions?

A second step that would improve the situation even more would be to add a low-voltage cutoff circuit on the path from the output of the two diodes to the radio board, so that a voltage of 60V or so would completely shut off the power to the radio board and reduce current draw to essentially zero. But this is more complicated to do, and might be unnecessary once the diodes are added and if you remember to check the charge level regularly.
IMO, very dangerous. Could result in turning off the power to the radio board while gliding. [And the same danger results from having a manual "on/off" switch.)
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Old 08-08-2017, 10:59 AM   #5
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The manual ON/OFF switch could be a key switch where the key is only removable when it's in the 'ON' position - No chance of it turning itself OFF while gliding

A $5 switch which would save a $1K battery seems like a reasonable design goal. I would hate to guess how many batteries have been trashed because the radio board ran them flat - Gotta be in the thousands

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Old 08-08-2017, 11:43 AM   #6
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The manual ON/OFF switch could be a key switch where the key is only removable when it's in the 'ON' position - No chance of it turning itself OFF while gliding
Don
So, the operator would be expected to turn it on and remove the key, and .....

Put it in a pocket?
Leave it at home?
Lose it? [after how many operations?]

Consider the human factors. Most folks wouldn't remove the key.

A manual switch could be implemented with software/firmware that would not turn off power (without warning) if the device had a rider on board. Just one more complication, of course. In any case, a manual switch isn't present on Generation 1 and 2 models, and would be inconvenient to retrofit.
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Old 08-08-2017, 05:24 PM   #7
Don M
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Quote:
Originally Posted by dale@thecoys.net View Post
So, the operator would be expected to turn it on and remove the key, and .....

Put it in a pocket?
Leave it at home?
Lose it? [after how many operations?]

Consider the human factors. Most folks wouldn't remove the key.
I would keep mine on the key ring with the keys to the padlocks we use to lock them up when we go inside to shop or to dine

If they lost the key, no big deal - They would have the spare key at home in a safe place and even should both of them eventually end up lost, where would they be??? Right back where we are now with no way to turn it off!

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Old 08-08-2017, 05:59 PM   #8
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Quote:
Originally Posted by Don M View Post
The manual ON/OFF switch could be a key switch where the key is only removable when it's in the 'ON' position -
Don
Quote:
Originally Posted by Don M View Post
I would keep mine on the key ring with the keys to the padlocks we use to lock them up when we go inside to shop or to dine
Don
So, it would be removed (ON) when you go inside to shop or dine?
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Old 08-08-2017, 07:13 PM   #9
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I would turn the key on when we load the Segs in the van to go touring and it would stay on for however long we're gone - Usually a week or so. We're using them everyday, recharging either in the motel room or with the inverter in the van. The key switch would only be off when the Segs are stored at home, not being used

When we lock them up to go into an establishment, we padlock them together with a heavy chain and then put the InfoKey in the 'Lock' mode, remove the InfoKey and take it with us. The Segs remain powered up and make a racket if anyone tries moving them

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Old 08-08-2017, 08:53 PM   #10
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Thanks. I now understand how you would use that feature.
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