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Charge Monitors - see your voltage, current, and input battery capacity while charging!


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Thanks to all of those who bought one of my first batch of charge monitors! I've re-stocked and streamlined things a bit to make them better, cheaper, and faster to build!
 
Features:
*Fully compatible with the "Roger Charger" and most other chargers / wheels
*XT60 connector at each end.
*Handles up to 50A of charge current
*I can offer a $5 discount for the first four 10A versions! Perfect if you will never charge above 10 amps
*Compatible with all wheels, even eBikes and other PEVs.
*Connects between your EUC charger and the EUC itself
 
The charge monitor displays, in real time:
*Battery voltage (1 decimal point up to 99.9V, then rounds to the nearest volt)
*Current draw (amps) while charging - down to 0.01A so you can see when balancing is 100% complete. Note: the green LED on your charger is lying to you! 😮
*Capacity that the charger has supplied to the battery (measured in either Amp-hours or Watt-hours - it can be toggled between the two). This value is saved in memory until cleared by the user.
 
I am happy to supply adapters for 84V, 100.8V and 134.4v wheels (GX16-4, GX16-5, and GX20-4 connectors respectively), as well as Y splitters if you want to charge at high current (12A+) through two connectors. These additional adapters and splitters are available at a small surcharge.
 
The case is 3d printed so you can select a choice of many colours.
 
Thanks to volume discounts from my suppliers and a more streamlined build process, I'm now offering these for $50 plus shipping for the 50A version with XT60 connectors on each end ($45 for the 10A version). Additional adapters, if needed, start at $5 each (Prices may increase later; I have to figure out what's sustainable). Each unit is tested and calibrated before shipping. Note that many chargers' displays, even Roger chargers, may not be completely accurate!
 
Please post here or PM me directly if you'd like one, would like a shipping quote (please include postal / zip code) or have any questions.
 
EDIT: I've started a Telegram group for general discussions, ordering info etc. Join here: https://t.me/+38e-toZUzTJkMTcx

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Edited by Mantraguy
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Very nice! What I would want as a feature that I could set a voltage above which it automatically disconnects the charger.

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On 9/23/2023 at 4:00 AM, Mono said:

Very nice! What I would want as a feature that I could set a voltage above which it automatically disconnects the charger.

The Charge Monitor does not interfere in any way with the charge status of the battery or charger - modern chargers and BMSes (even 'dumb' BMSes) handle things well enough that interference by a third-party device is not required, or normally desired. Through using this device for the last couple of years or so, I've found that all of my stock chargers from Begode and Veteran, as well as most after-market chargers, work very well with the wheels to control charging perfectly. Occasionally the output voltage of the charger isn't 100% accurate, but beyond that, they do very well to gradually decrease current (once the peak voltage is reached) in order to fully balance the packs, and eventually shut off charging altogether, showing full voltage and 0.00A on the Charge Monitor display.

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11 hours ago, Mantraguy said:

The Charge Monitor does not interfere in any way with the charge status of the battery or charger - modern chargers and BMSes (even 'dumb' BMSes) handle things well enough that interference by a third-party device is not required, or normally desired. Through using this device for the last couple of years or so, I've found that all of my stock chargers from Begode and Veteran, as well as most after-market chargers, work very well with the wheels to control charging perfectly. Occasionally the output voltage of the charger isn't 100% accurate, but beyond that, they do very well to gradually decrease current (once the peak voltage is reached) in order to fully balance the packs, and eventually shut off charging altogether, showing full voltage and 0.00A on the Charge Monitor display.

I don't see how monitoring voltage and current should give you any (somewhat) conclusive insights into the (dis-)functioning of the BMS. The current depends on the voltage difference between charger and battery and will at some point gradually decrease to zero with increasing charge status, that's neither remarkable nor an indication of a functioning or dis-functioning BMS.

I got the impression that you didn't quite understand my feature request as it has little to do with interfering "with the charge status of the battery or charger" :(. I just would want the device, which is connecting charger and wheel, to be able cut this connection (that is, stop charging) depending on the measured voltage. No worries though, I am currently not in need as I already have a ChargeDoctor which does exactly that, among other things.

Edited by Mono
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1 hour ago, Mono said:

I don't see how monitoring voltage and current should give you any (somewhat) conclusive insights into the (dis-)functioning of the BMS. The current depends on the voltage difference between charger and battery and will at some point gradually decrease to zero with increasing charge status, that's neither remarkable nor an indication of a functioning or dis-functioning BMS.

I got the impression that you didn't quite understand my feature request as it has little to do with interfering "with the charge status of the battery or charger" :(. I just would want the device, which is connecting charger and wheel, to be able cut this connection (that is, stop charging) depending on the measured voltage. No worries though, I am currently not in need as I already have a ChargeDoctor which does exactly that, among other things.

I don't believe that I stated that monitoring the voltage and current with the Charge Monitor would, in any way, show you how well (or not) the BMS was working. However, most chargers on the market now only give you an LED that turns green at some point during the CV phase, as the current drops below a set limit. That may be taken by some users as an indication that the pack is fully charged, but that's not strictly true - the pack is still taking current, and it's during this phase that the BMS does its job to balance the cell groups within the pack. The Charge Monitor is simply showing the user that, despite the LED on the charger turning green, the battery is still accepting a charge current and the charge (including balancing) is not 100% complete.

I do understand your feature request. By definition, cutting a connection between the charger and wheel (battery) is interfering with the charge. The Charge Monitor measures - that's all it does, and I have no plans to alter it to do anything else as it works great for its intended purpose. My point was that most chargers available these days work well, so a device that cuts the charge at some point isn't really necessary. We now know that charging your battery to less than 100% is not beneficial to the long-term health of the battery, as it would never get balanced. Back when the Charge Monitor was offered, there was some question about this, so some users preferred to charge to 80% or 90% voltage. It's generally accepted now that this is not the best way to do things. However, if your charger is attempting to over-charge the packs (deliver too high a voltage) to the point that you want a device that cuts the charge at a set voltage, I would suggest that the charger is not safe to use and should be replaced or repaired.

I'm familiar with the Charge Doctor, and used it for a while on my first EUC, a Gotway Tesla V2. However, it's only rated up to 100v so on most modern wheels, at 100.8V, 126V and 134.4V, the Charge Doctor would be outside of its rated limit and may not be safe to use. I'm not sure what the rated current is but it's almost definitely not 50A (perhaps 10A, probably much less); the Charge Monitor can handle 50A of charge current which is more than anyone I'm aware of will charge at these days (some 'superusers' use multiple fast-chargers together to exceed 30A after bypassing certain systems built into the EUC, but most wheels won't accept a charge of more than about 13-15A without modification). It does have a few features that my Charge Monitor does not have (such as interfering with the charge when a certain limit is reached), but I think those features are no longer required with modern chargers and EUCs.

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On 9/27/2023 at 6:27 PM, Mantraguy said:

We now know that charging your battery to less than 100% is not beneficial to the long-term health of the battery, as it would never get balanced.

I actually don't know this :). I do know that deep cycles and storing the battery at high charge status lead to quicker degradation. I also know that some (and probably most) battery packs don't need to be balanced every (full) cycle to stay perfectly balanced. Anyway, I was just writing what I would want, it's obviously totally up to you what you (don't) provide, no need to justify that.

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