TSD2 range ?!

[Bogmonster666]

Thank you for the detailed remarks. I will look into how to optimise the motor for a specific cadence regardless of battery voltage.

I know osf is not something that will ever be covered by warranty. For the tsdz2 I suspect getting new firmware from the manufacturer is unlikely.

Out of curiosity I had a little peek in the OSF code on my phone. Field weakening is started to be employed over 48 rpm and progressively up to 105 rpm.

At my cursory glance it takes no account of voltage when setting the field weakening angle - but might be easier to read on a proper computer.

Assuming osf field weakening really works (and anecdotally it appears to), it's a great shame Tonsheng haven't baked this into the stock firmware.

I understand that machining and material costs to fix physical weaknesses can be high but a software change should be relatively cheap to implement. Of course flashing the tsdz2 is a faff with nasty error prone cables...so even if Tongsheg created a new firmware, it would not be easy for existing owners to flash. Of course, I think this is all somewhat academic as I get the impression the tsdz2 isn't being onwardly developed?

C

 

[Woosh]

as you said before, it's not a big issue because you would go out with a full battery most of the time. Still, manufacturers are naturally reticent to change the firmware for good reason, one mistake could sink the ship!
If you buy your kit from abroad, then OSF is the way to go because you are on your own anyway but most of my customers prefer to stick with the original firmware until the warranty runs out.
PS: I just took a peek at the add field_weakening_angle code and got lost in their math or logic.
Will look again over the weekend. Maybe possible to change the formula to add an extra factor for battery voltage.

/* // add field_weakening_angle
ui16_temp = (uint16_t) ui8_g_duty_cycle;
ui16_temp = (ui16_temp * 100) / PWM_DUTY_CYCLE_MAX;
if (ui8_g_field_weakening_enable_state)
{
ui16_temp += (((uint16_t) ui8_g_field_weakening_angle) * 14) / 10;
}
ui8_tx_buffer[15] = (uint8_t) ui16_temp;
*/

 

[saneagle]

Hi, on reflection I should have chosen a better title for this thread, probably "how accurate is the battery charge indicator?" The short answer is "not very". This is confirmed by forum comments and a few reviews like this one.


Initially I suspected that a voltage setting in the display was incorrectly set as you suggest, but I have been unable to find such a setting and if it were set to 36 volts then my 48 volt battery would register full charge throughout its 41v-54v cycle. Instead it has dropped one bar when the battery is just under 50% charge (76 miles). It is what it is so I am fitting a small digital volt meter to help me judge the state of the battery.

The battery inicator is very accurate. Only people that don't understand how it works say otherwise. It's basically a voltmeter that tells you when the voltage crosses various boundaries. Tht was explained by Woosh above. It uses a voltage divider to indicate to the LCD's CPU an actual voltage. The CPU uses software to send a repeatble instruction from its software to the LCD so that each bar on the display will change at exactly the time the battery voltage reaches the condition for each one. You can check it with a voltmeter, and you will find that it's consistent and accurate. It's up to you how you interpret and use the information, which is where the inconsistency comes in.

Battery voltage is not a good indication of range because not only is the voltage non-linear as it discharges at a constant current, but it also varies according to how much current you take fom the battery, which is varying all the time when you have a torque sensor system. When you pedal hard, the current will increase and the voltage will go down, then the voltage will bounce back up when you stop pedalling or pedal with less effort. Also, like Woosh explained, the motor's power decreases as the battery voltage goes down, so riders tend to demand more current from the system by pedalling harder, which causes increased voltage sag. In practical terms, that all means that the battery goes down slowly at first, then accellerates downwards during its discharge cycle.

To stop bars flashing on and off as you pedal, the software includes a damping factor, which is basically a moving average of the voltage that has the effect of averaging out and delaying the response of the battery level indication in the LCD.

To summarise, the LCD is not a range-meter. It's a voltmeter. To estimate your range at any time you need to understand how hard you're likely to be pedalling for the rest of your journey and how much hill-climbing you will be doing, and whether you expect to change your speed. No computer can know those things. What you will always know is exactly what voltage is in your battery when any segment goes out.

As suggested above, if you want an accurate indication of how much battery charge you have left, you can use a wattmeter in conjunction with the LCD. You can see at how many watt-hours you've used when each segment goes out, which will be consistent as long as it doesn't happen at a ime of excess voltage sag, like when hill-climbing. You can then interpret each bar on the display as a known percentage of charge remaining, and, as others have mentioned, there won't be much charge left when three of five are out.

I say again from my vast experience that if you do 60 miles on any electric bike and the LCD still shows all bars, either something is wrong or you did something exceptional that a normal e-bike rider wouldn't do, like riding with the power switched off or an exceptionally flat ride with the wind behind you. It can't just happen without explanation and you confirmed that you average 10 mph, so it wasn't that you were riding over the 15 mph cut-off, which would explain how that can happen with a fit rider on a fast bike, and your recumbent trike gives no advantage at that speed. In fact its additional mass and roolling resistnce would be a disadvantage. You should check the function of your battery indicator with a voltmeter.

When you said that the first indicator went out at 50% charge, that doesn't make sense to me. How did you figure out how much charge was left without a wattmeter? Also, the indicator levels are fixed by the hardware and software. The only way it could happen is if a wrong resistor were soldered to the PCB, but I never heard of that. I'm losing sleep over this. Please give an explanation so that I can make sense of it all.

 

[Bogmonster666]

as you said before, it's not a big issue because you would go out with a full battery most of the time. Still, manufacturers are naturally reticent to change the firmware for good reason, one mistake could sink the ship!
If you buy your kit from abroad, then OSF is the way to go because you are on your own anyway but most of my customers prefer to stick with the original firmware until the warranty runs out.

I made my choice to buy from a UK company with CS and a warranty that may actually be usable rather than importing. Tbh, it was mainly the lack of availability of batteries of a suitable quality and difficulty sourcing a 48v 250w motor.

I don't regret the decision to buy from the UK.

C

as you said before, it's not a big issue because you would go out with a full battery most of the time. Still, manufacturers are naturally reticent to change the firmware for good reason, one mistake could sink the ship!
If you buy your kit from abroad, then OSF is the way to go because you are on your own anyway but most of my customers prefer to stick with the original firmware until the warranty runs out.
PS: I just took a peek at the add field_weakening_angle code and got lost in their math or logic.
Will look again over the weekend. Maybe possible to change the formula to add an extra factor for battery voltage.

/* // add field_weakening_angle
ui16_temp = (uint16_t) ui8_g_duty_cycle;
ui16_temp = (ui16_temp * 100) / PWM_DUTY_CYCLE_MAX;
if (ui8_g_field_weakening_enable_state)
{
ui16_temp += (((uint16_t) ui8_g_field_weakening_angle) * 14) / 10;
}
ui8_tx_buffer[15] = (uint8_t) ui16_temp;
*/

This is the bit of code that works out the angle:

// Calculate Field Weakening max Angle based on current motor speed
// Field weakening max angle is 0 when cadence is below 48rpm
// Field weakening max angle is 6 when cadence is above 105rmp
// between 48 and 105rpm goes from 1 to 5
#define FW_COUNTER_MIN 65U
#define FW_DIVISOR 16U
#define FW_COUNTER_MAX (FW_COUNTER_MIN + (FW_DIVISOR*5))

if (ui16_PWM_cycles_counter_total >= FW_COUNTER_MAX)
ui8_fw_angle_max = 0;
else if ((uint8_t)ui16_PWM_cycles_counter_total <= FW_COUNTER_MIN)
ui8_fw_angle_max = 6;
else
ui8_fw_angle_max = 5 - ((uint8_t)((uint8_t)ui16_PWM_cycles_counter_total - FW_COUNTER_MIN) / (uint8_t)FW_DIVISOR);

I think the code you pasted above applies this. There may well be compensation for voltage elsewhere but I need a bigger screen... If not, I am sure it's possible to adjust the angle based on rpm and voltage, its only code, but I suspect it isn't important. Possibly tweaking the angle based on voltage might improve efficiency slightly but I don't know enough about motors to say either way.

My overall aim would be to get an elongated cadence range, I suspect the OSF field weakening logic is quite sufficient as it is.

I am guessing the Whoosh motor has the older controller supported by osf, not the V2? Like I say I'm, not in a hurry, but maybe when out of warranty...

C

 

[Woosh]

Which version are you looking at?

 

[Bogmonster666]

Emmebrusa - TSDZ2-v20.1C.2-update-2 for VLCD5-VLCD6-XH18, I think...

Motor.c line ~768...

 

[Woosh]

I think the code you pasted above applies this. There may well be compensation for voltage elsewhere but I need a bigger screen... If not, I am sure it's possible to adjust the angle based on rpm and voltage, its only code, but I suspect it isn't important. Possibly tweaking the angle based on voltage might improve efficiency slightly but I don't know enough about motors to say either way.

You have already seen that the cutoff speed of the motor is directly proportional to the battery voltage, the coefficient is known as motor constant Kv. It follows that you would want to increase Kv to compensate for the drop in voltage. The way to do that is by field weakening, So I imagine that you would want to apply a FW angle that depends on voltage instead of cadence, something like FW_angle = 0.5 * (54- battery voltage)

 

[Bikes4two]

The battery indicator is very accurate. Only people that don't understand how it works say otherwise. It's basically a voltmeter that tells you when the voltage crosses various boundaries.

• When I first read the above, I was not in agreement with it at all but I then read further (and more than once) and the bit that says:

Battery voltage is not a good indication of range

• had me re-thinking it all and coming round to agreeing with what you say.
• Within OSF you can change the voltage thresholds for the bar indicators which I guess is useful for those who understand the implications of doing so(not me - well, just a little bit anyway).
• In my case I have over time and a good many charges/discharges for varying rides/miles/conditions, noted through the use of a watt meter the amount of power consumed and have formed a reasonably accurate 'achievable range' for my batteries vs the sort of riding and conditions I undertake.

So thanks for the above @saneagle - every day is a school day.

 

[Simon Knight]

The battery inicator is very accurate. Only people that don't understand how it works say otherwise. It's basically a voltmeter that tells you when the voltage crosses various boundaries.

The point of my original post was to gain knowledge of how the display operates by comparing what I see with what other users experience. "Very accurate" is an unfortunate term perhaps you would care to specify how accurate and how you know.

Also I have two volt meters on my system, the one we are talking about on the display and the one on the battery. The four segment display on the battery appears to be the more useful of the two as it has dropped two bars whereas the display is still showing 5 with the sixth bar pulsing. To be blunt I trust the meter that is showing the lower value.

As suggested above, if you want an accurate indication of how much battery charge you have left, you can use a wattmeter in conjunction with the LCD.

The issue I have with a watt meter is that they are high current devices so need to be well insulated and protected from the weather. I have one and I don't think it is of higher enough quality to have in circuit. I will however use it on the charging side to get some idea of how much energy is being used in charging the battery.

It can't just happen without explanation and you confirmed that you average 10 mph,

What I wrote was that over many years my average speed when recreational cycling was 10 mph i.e. on non electric cycles.

When you said that the first indicator went out at 50% charge, that doesn't make sense to me.
How did you figure out how much charge was left without a wattmeter?

Quite, it does not make a great deal of sense to me which is rather where this thread started and no, I have not fitted a wattmeter. Half charge is an estimate based on the second volt meter which is now showing 2 bars from 4. The battery off load voltage is 47.1 volts +/- 0.5v. In a perfect world both volt meters would change at a similar rate.

Also, the indicator levels are fixed by the hardware and software. The only way it could happen is if a wrong resistor were soldered to the PCB, but I never heard of that. I'm losing sleep over this. Please give an explanation so that I can make sense of it all.

No need to lose any sleep it is what it is. The explanation is that the measuring device is cheaply made with little or no quality control and no calibration. None of this is surprising and it does not cause me to lose any sleep. The equally cheap volt meter I have just fitted will give me a better idea how the system is performing and when I start measuring joules in I will be to have some idea how the volt meters perform.

Moving on, so far I have not noticed any issues with regards to cadence but I probably have some way to go before the issues reported may become apparent.

Placing all of this post to one side I am happy with both the kit and the support from Woosh. To put it simply, fitting the kit has made my trike a better car replacement than when it was unassisted. The only negative is that in early spring a greater number of layers need to be worn owing to the wind blast from higher speed in conjunction with lower physical input from me.

S

 

[Simon Knight]

• had me re-thinking it all and coming round to agreeing with what you say.
• In my case I have over time and a good many charges/discharges for varying rides/miles/conditions, noted through the use of a watt meter the amount of power consumed and have formed a reasonably accurate 'achievable range' for my batteries vs the sort of riding and conditions I undertake.

So how does the six segment display of voltage operate on your rides? Does the rate of change of the display accelerate as the number of segments decrease and is there any correlation with what you see on your watt meter?

S

 

[Woosh]

to tell the truth, I know more about Lishui controllers and Bafang motors than the TSDZ2. Andy is on holiday this week, I expect he'll need a couple of days to catch up with his intray before we can set up a test rig to figure out the way the TSDZ2 kit reacts to the battery voltage.
On the Lishui, the LCD controls the 5 battery segments. In the OSF TSDZ2 firmware, the code controls the 5 battery segments. I just don't know how Tongsheng does it, LCD or code? A test rig will work that out in a few hours.

 

[Bikes4two]

So how does the six segment display of voltage operate on your rides? Does the rate of change of the display accelerate as the number of segments decrease and is there any correlation with what you see on your watt meter?

I use the VLCD6 display which only has a 4 segment voltage display and I tried several times via OSF to change the segment change points to give what I hoped would be a more proportionate indication of remaining battery charge, but without success.

So basically I now ignore the display totally. I check the voltge with a plug-in volt meter on my battery before setting off on a ride to ensure it's still fully charged (I re-charge after every ride of more that 10 miles) and I know from cycling more than 3500 miles on this battery what range I'll get.

As a 'belts and braces' measure, on re-charging the battery I always charge through a watt meter and take a note of miles vs Ah & Wh to detect any untoward behaviour.

Further, I ocassionally (once every 4-6 months?) fully charge and then discharge the battery though a watt meter into a resistive dummy load. In this way I can detect the gradual dropping of total capacity over time and charge/discharge cycles.

So far battery capacity has dropped maybe 5% or less but within that value there will be varyiations due to different ambient temperatures in my bike shed - but hey, I'm not looking for scientific accuracy here, just enough information for early detection of battery issues.

 

[Simon Knight]

to tell the truth, I know more about Lishui controllers and Bafang motors than the TSDZ2. Andy is on holiday this week, I expect he'll need a couple of days to catch up with his intray before we can set up a test rig to figure out the way the TSDZ2 kit reacts to the battery voltage.
On the Lishui, the LCD controls the 5 battery segments. In the OSF TSDZ2 firmware, the code controls the 5 battery segments. I just don't know how Tongsheng does it, LCD or code? A test rig will work that out in a few hours.

Crikey now I feel guilty it seems I've opened a Pandora's box . All I meant to do was express my surprise at how the display of battery state did not appear to be reacting to the use of assistance. If you do take a closer look I would be interested in how the four LEDs on the battery work. For example are they controlled by four zener diodes ?

(Just been reading on internet) Unfortunately any system that relies on voltage to estimate state of charge of a Lithium Ion battery is going to be inaccurate. A single cell will only drop 0.5v between 40% and 80% depth of discharge (https://www.powertechsystems.eu/home/tech-corner/lithium-ion-state-of-charge-soc-measurement/). I wonder if the following make any sense :

I don't know how my battery is built but a block of cells (21700) will be connected in series and then a small number of these series blocks will be connected in parallel. One method would be to connect 13 cells in series and connect three of these in parallel. This is based on a nominal cell voltage of 3.7 volts so 48/3.7 is just under 13 meaning that 13 cells have to be connected to achieve the nominal voltage of 48v. Each cell has a 5 Amp hour capacity so three blocks are needed to store 15ah. The maximum charge voltage is 4.2v which gives a maximum battery voltage of 54.6 volts for the nominal 48 volt battery being considered.

So if each cell drops 0.5v then the battery will drop 13* 0.5 volts or 6.5 volts between 40% and 80% depth of discharge (DOD) assuming a common drop across all cells.

I'm not saying this is how my battery is built as I am sure there are other methods but it suggests that using floating battery voltage as an indication of charge is dependent on battery configuration. It also suggests that a 36 volt system will have a smaller voltage drop for the same 40% to 80% DOD because fewer cells are used to achieve 36 volts. This implies that any software monitoring the voltage will have to account for this difference for it to be of value on both 36v and 48v systems (5 volts versus 6.5 voltage drop to indicate the same depth of discharge).

Its worth noting that at DODs > 80% the voltage drops off a cliff so it seems that it is important to consider the rate of change of voltage. When it accelerates its time to recharge.

Warning, the above may well be CUB!

S

 

[Woosh]

Crikey now I feel guilty it seems I've opened a Pandora's box .

I need to know too.

 

[Simon Knight]

So basically I now ignore the display totally. I check the voltge with a plug-in volt meter on my battery before setting off on a ride to ensure it's still fully charged (I re-charge after every ride of more that 10 miles) and I know from cycling more than 3500 miles on this battery what range I'll get.

As a 'belts and braces' measure, on re-charging the battery I always charge through a watt meter and take a note of miles vs Ah & Wh to detect any untoward behaviour.

Great post. Your use of a voltmeter appears to be the only meaningful way to assess the charge status of the battery i.e. measuring the floating off load value. On load voltages will be all over the place depending on the load.

I will be searching my parts bin for some connectors to add my cheap watt (coulomb ?) meter between the charger and the battery, (I'm hoping it can deal a continuous 2 amps). I see on-line that coulomb meters are available and that they utilise a clamp meter type method of measuring current meaning that the power line remains unbroken. This seems a safer method of measuring energy used than the in circuit ammeters. I'm also going to search for the Panasonic data sheet for the 21700 cells to try and determine the 0% to 80% depth of discharge voltages so that I can assess battery state mid ride.

As an aside I see that Grin Technologies of Canada produce a rather nice universal battery charger which allows various charging regimes to be pre-programmed and saved in memory e.g. Charge 48v battery to 80% capacity using a maximum of 4 amp charge rate. Its not cheap but could save money in the long run by helping keeping the battery charged in the ideal 80%-20% range and extending its useful life.

S

 

[Simon Knight]

I will be searching my parts bin for some connectors to add my cheap watt (coulomb ?) meter between the charger and the battery

The Watt meter is fitted to the charger and I have recharged my battery to full as indicated by the LED turning green on the charger. To recap following my first charge I rode 76 flat Lincolnshire miles mostly on road and was wondering why the battery display was still showing five and half (pulsing sixth segment).

In an attempt to get warm I started a couple of rides with no power and I adjusted the wheel size to get the speed matching the existing cycle computer and a handheld GPS I am working on the principle that I covered 70 miles on the first charge.

At the time just before the second charge the main display showed five solid bars with the sixth flashing on and off.
The four segment LED display on the battery showed two bars and the rested battery open circuit voltage was 47.1 volts.

Recharging the battery to full took approximately five and half hours and the watt meter indicated the following statistics:

Initial charge voltage : 47.6 volts
Final charge voltage : 54.5 volts
Charge current : 1.87 amps (stayed constant throughout the charge)
Amp hours added : 5.329 amp hours
Watt hours added : 267.3 Wh

Initial no load voltage when back on the trike is 54 volts but the battery needs time to settle post charge.

The meter is completely un-calibrated so its not possible to tell how accurate the figures are. They suggest that I have 'only' used a third of the battery capacity and am using 4 W per mile.

Thoughts and comments welcome.

S

 

[Woosh]

Thank you for the numbers. The first bar goes after 35% of charge used and you use 4wh per mile. I will check the LCD with lower battery voltages in the next two days.

 

[Bikes4two]

@Simon Knight -

I see on-line that coulomb meters are available and that they utilise a clamp meter type method of measuring current meaning that the power line remains unbroken.

• I've used clamp meters for various AC voltage/current measuring uses and to get an accurate, consistent and reliable reading, the single wire passing through the measuring ring needs to be held steady and more or less in the middle of the ring.
• I borrowed a friend's clamp meter that also measured DC current and the ring positioning was even more critical to get a reliable reading. By all means give one a go but I suspect that any reading will not be consistent.
• And in practice you will need to physically separte the '+Ve' and '-Ve' wires enough to pass one of them through the ring.

As an aside I see that Grin Technologies of Canada produce a rather nice universal battery charger which allows various charging regimes to be pre-programmed and saved in memory e.g. Charge 48v battery to 80% capacity using a maximum of 4 amp charge rate. Its not cheap but could save money in the long run by helping keeping the battery charged in the ideal 80%-20% range and extending its useful life.

• That charger is a pricey piece of kit as you've noticed. There are far simpler ways of achieving 80% capacity and I'm curious as to why you'd want to do this anyway?
• A lot of folk like to charge to a little bit just under the max voltage put out by the charger - to achieve this you could for instance insert a suitably rated diode in series with one of the charger leads to reduce the voltage at the battery charging terminals by something between 0.1v and 0.6v depending on diode type. That does of course require some fettling with a soldering iron and 'stuff' but for a fraction of the cost of a major wallet extraction.
• Charging current - standard 'as supplied' chargers are 2 amp and it is cheap to get a 4 amp charger if there is a need. Apparently a 2 amp charge rate will get you more charge/discharge cycles from your battery than charging at 4 amps but in practice you need to wonder if this is worth the bother.
• For instance, if you are getting 50 miles from a full charge at 2A and the batteries have a 'life' of 500 cycles, then you're good to 25,000 miles.
• Let's assume at 4A you're only good for 400 charge/discharge cycles - that's 16,000 miles.
• Now maybe that's not a lot of miles for you but it'd take me 5 years to do that in which time battery tech will have inproved and I'll be happy to build a newer battery with greater capacity/lighter weight.
• On the other hand, you might be a Bosch battery owner and you NEVER want to fork out for a replacement .
• I charge at 4A and am happy with that.

 

[Simon Knight]

Thank you for the numbers. The first bar goes after 35% of charge used and you use 4wh per mile. I will check the LCD with lower battery voltages in the next two days.

I am concerned that the 4wh per mile seems low as I do not class myself as a powerful cyclist. As the weather improves I will be using the e-trike more so will collect more data which I'm happy to report. I will try and collect more data points to enable the plotting of voltage to Wh used.

My search for a specific data sheet describing the Panasonic 21700 failed but I did find information that can be read across. Here are some the links :
Tentative Panasonic specification sheet for their NCR20700B cell : http://www.batteryspace.com/prod-specs/10873 specs .pdf
"A Guide to Understanding Battery Specifications" http://web.mit.edu/evt/summary_battery_specifications.pdf
Lastly for those who enjoy detail "Energy Density of Cylindrical Li-ion Cells: A Comparison of Commercial 18650 to the 21700 Cells: :https://iopscience.iop.org/article/10.1149/2.0281814jes

It seems that cells are made in two forms: high power and high energy with the two types having different discharge curves. However, it seems that the chemistry means that all cells have the same basic discharge curve with a starting with a short sharp reduction in voltage, then a gentle decline before falling down over a cliff at near the 80% depth of discharge which is the point where deep discharge occurs. Taking cells into either end of the charge curve shorten the life of the cells with deep discharge being the worst.


It appears that a single cell exhibits a voltage drop in the range 0.5v to 0.7v depending on load and where you decide the "cliff edge" is. This was taken from the Panasonic data sheet and another graph in the data sheet shows similar differences depending on cell temperature. So voltage drop depends on both load and temperature. Note that Panasonic is calling a single cell a battery which is possibly confusing.

Applying my recorded data to the graph my battery dropped to 47.1 volts. Divide this value by 13 gives (I believe) the single cell voltage of 3.6volts. Reading across to the black line suggests that the cell has been discharged by 1600 mAh. Again I believe my battery is made up of three series wired packs of cells wired together in parallel so 3x1600 = 4800 mAh battery discharge. The watt meter reported adding 5329 mAh meaning the graph is in the ball park.

Note Woosh reported above that the lowest battery voltage should be 41 volts. This equates to 3.15 volts on the graph and is just after the point where the curve takes the plunge downwards.

One final point I read is that some cheaper cells claim a theoretical capacity based on chemistry and physical size and were found to be wildly inaccurate. Whereas the big name brands tend to quote measured values. You pays your money and takes your chance.

Enjoy!

 

[Simon Knight]

• Let's assume at 4A you're only good for 400 charge/discharge cycles - that's 16,000 miles.
• Now maybe that's not a lot of miles for you but it'd take me 5 years to do that in which time battery tech will have inproved and I'll be happy to build a newer battery with greater capacity/lighter weight.

Trust me thats a lot of miles!

All the points in your post are excellent - thanks.

You are correct about the Grin charger being expensive but I do have several e-bikes in my household so it may be of value to me as it would simplify the charging equipment and possibly be more accurate than my cheap Watt meter.

However, I'm don't think I'm going to add any extras to my set up for the time being as they are unlikely to provide any more useful information at present. I need to use the Tongsheng more to gain an understanding of how it performs. In short I shall follow your advice given above (and further above) which I can now do since adding the Watt meter to the charger.

Woosh will be looking at how the display operates on the 48v system and I am now in a position to note the voltage at which the display reduces by a bar for comparison.

S