Refrigerated Charging

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jurba
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Re: Refrigerated Charging

it might just be cheaper to move to england nice n cool.
lovely scenery .

I am afraid of swain flu ((((-: .... I never seen any vectrix in Colchester where I am quite often

vectrixhoper

kevin smith
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Re: Refrigerated Charging

theres a cuppa tea n scone for you if you come to leeds and mybe a ride on my silver scoot .kev

jurba
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Re: Refrigerated Charging

theres a cuppa tea n scone for you if you come to leeds and mybe a ride on my silver scoot .kev

great it is worth façing swain flu then, I'll drop you a mail before so that you heat the oven !!!!

vectrixhoper

The Laird
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Re: Refrigerated Charging

Hi folks,

It really is time that someone got to grips with the vexed subject of batteries and heat produced. So I'll toss in my information.

First things first is to understand why the battery heats up and the reasons for this are as follows.

It is being charged. When the battery is charged from empty to about 80% of full, the conversion of electrical to chemical energy is high (around 95%+) and very little heating of the battery takes place. From 80% to 'full' much more heat is generated because the electrical to chemical conversion cannot take place quickly and 'forcing' current into the battery results in far greater heat generation.

The real solution to this excessive heat build-up within the battery is to reduce the charging current, when the charge level reaches 80%, to a level which allows the energy conversion to take place at a more efficient rate. Simply powering the plenum fans (sorry Mik - Impellers) and continuing to force current into the battery at too high a rate is NOT the way to solve the problem. Vectix's charger software is deficient in this respect. I will happily re-write it for them if I get the chance.

The second source of battery heating is when it is in use i.e. the bike is being driven. There will always be some heating due to the conversion of chemical to electrical energy and there will be additional heating due to the internal resistance of the battery cells. This is unavoidable and the effect is greater when the current supplied by the battery is greater.

The solution here is to provide for Plenum fan cooling whenever the bike is being used AND when the battery temperature is greater than the ambient temperature by more than 3 degrees.

Another source of heating is regenerative braking when the battery is over 80% full. Again there is a way of dealing with this problem. The rider knows when the battery is over 80% full because there are more than 13 'bars' showing on the fuel gauge, when this is the case DO NOT USE regenerative braking. This feature could also be programmed into the motor control software. There are ways of providing regenerative braking without heating the battery i.e dumping the heat elsewhere, if the safety aspect of 'not having regenerative braking available at all times' were to be an issue.

Just for interest. It requires about 1 Amp at 120 Volts to raise the battery temperature at the rate of 5 degrees Centigrade per hour. So when the charger is pushing 3 Amps into the battery as an equalising charge, about 3/4 Amp is driving the Plenum Impellers, between 1/2 and 1 Amp is producing heat and just over 1 Amp is going where it should, which is into the battery.

Oh, and the higher the battery temperature the greater the rate of self discharge.

So there you have it. Cooling the battery is good, but not heating it in the first place is far better.

Incidentally, the incompetent charger software is probably Vectrix's biggest cock-up and it has, without doubt, contributed to the company's demise by virtue of the fact that it has destroyed numerous batteries unnecessarily.

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Re: Refrigerated Charging

Hi folks,

It really is time that someone got to grips with the vexed subject of batteries and heat produced. So I'll toss in my information.

First things first is to understand why the battery heats up and the reasons for this are as follows.

It is being charged. When the battery is charged from empty to about 80% of full, the conversion of electrical to chemical energy is high (around 95%+) and very little heating of the battery takes place. From 80% to 'full' much more heat is generated because the electrical to chemical conversion cannot take place quickly and 'forcing' current into the battery results in far greater heat generation.

The real solution to this excessive heat build-up within the battery is to reduce the charging current, when the charge level reaches 80%, to a level which allows the energy conversion to take place at a more efficient rate. Simply powering the plenum fans (sorry Mik - Impellers) and continuing to force current into the battery at too high a rate is NOT the way to solve the problem. Vectix's charger software is deficient in this respect. I will happily re-write it for them if I get the chance.

The second source of battery heating is when it is in use i.e. the bike is being driven. There will always be some heating due to the conversion of chemical to electrical energy and there will be additional heating due to the internal resistance of the battery cells. This is unavoidable and the effect is greater when the current supplied by the battery is greater.

The solution here is to provide for Plenum fan cooling whenever the bike is being used AND when the battery temperature is greater than the ambient temperature by more than 3 degrees.

Another source of heating is regenerative braking when the battery is over 80% full. Again there is a way of dealing with this problem. The rider knows when the battery is over 80% full because there are more than 13 'bars' showing on the fuel gauge, when this is the case DO NOT USE regenerative braking. This feature could also be programmed into the motor control software. There are ways of providing regenerative braking without heating the battery i.e dumping the heat elsewhere, if the safety aspect of 'not having regenerative braking available at all times' were to be an issue.

Just for interest. It requires about 1 Amp at 120 Volts to raise the battery temperature at the rate of 5 degrees Centigrade per hour. So when the charger is pushing 3 Amps into the battery as an equalising charge, about 3/4 Amp is driving the Plenum Impellers, between 1/2 and 1 Amp is producing heat and just over 1 Amp is going where it should, which is into the battery.

Oh, and the higher the battery temperature the greater the rate of self discharge.

So there you have it. Cooling the battery is good, but not heating it in the first place is far better.

Incidentally, the incompetent charger software is probably Vectrix's biggest cock-up and it has, without doubt, contributed to the company's demise by virtue of the fact that it has destroyed numerous batteries unnecessarily.

I am playing around with 160 NHW10 batteries and 5 NHW20 batteries. The way to charge them is CV, causing an asymptotical approach to FULL (or 80% full, or whatever you wish). The same would be good for the VX-1.
Start with the maximum current the charger can provide, then keep the supply voltage at no more than 102 * 1.45V = 147.9V for a 100% charge, or about 102 * 1.40V = 142V for an 80% charge. That will limit heating even if you do a full charge, it will just take longer.

A further important addition would be much more re-circulating of air within the battery compartment, to equalize cell temperatures. The temperature gradient is massive when parked in the sun.

The charger only uses 10A = C/3 at full CP load, I guess that's why little heating occurs even when charging to 16/17th.

This information may be used entirely at your own risk.

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

AndY1
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Re: Refrigerated Charging

Hi folks,

It really is time that someone got to grips with the vexed subject of batteries and heat produced. So I'll toss in my information.

First things first is to understand why the battery heats up and the reasons for this are as follows.

It is being charged. When the battery is charged from empty to about 80% of full, the conversion of electrical to chemical energy is high (around 95%+) and very little heating of the battery takes place. From 80% to 'full' much more heat is generated because the electrical to chemical conversion cannot take place quickly and 'forcing' current into the battery results in far greater heat generation.

The real solution to this excessive heat build-up within the battery is to reduce the charging current, when the charge level reaches 80%, to a level which allows the energy conversion to take place at a more efficient rate. Simply powering the plenum fans (sorry Mik - Impellers) and continuing to force current into the battery at too high a rate is NOT the way to solve the problem. Vectix's charger software is deficient in this respect. I will happily re-write it for them if I get the chance.

The second source of battery heating is when it is in use i.e. the bike is being driven. There will always be some heating due to the conversion of chemical to electrical energy and there will be additional heating due to the internal resistance of the battery cells. This is unavoidable and the effect is greater when the current supplied by the battery is greater.

The solution here is to provide for Plenum fan cooling whenever the bike is being used AND when the battery temperature is greater than the ambient temperature by more than 3 degrees.

Another source of heating is regenerative braking when the battery is over 80% full. Again there is a way of dealing with this problem. The rider knows when the battery is over 80% full because there are more than 13 'bars' showing on the fuel gauge, when this is the case DO NOT USE regenerative braking. This feature could also be programmed into the motor control software. There are ways of providing regenerative braking without heating the battery i.e dumping the heat elsewhere, if the safety aspect of 'not having regenerative braking available at all times' were to be an issue.

Just for interest. It requires about 1 Amp at 120 Volts to raise the battery temperature at the rate of 5 degrees Centigrade per hour. So when the charger is pushing 3 Amps into the battery as an equalising charge, about 3/4 Amp is driving the Plenum Impellers, between 1/2 and 1 Amp is producing heat and just over 1 Amp is going where it should, which is into the battery.

Oh, and the higher the battery temperature the greater the rate of self discharge.

So there you have it. Cooling the battery is good, but not heating it in the first place is far better.

Incidentally, the incompetent charger software is probably Vectrix's biggest cock-up and it has, without doubt, contributed to the company's demise by virtue of the fact that it has destroyed numerous batteries unnecessarily.

Thank you for this wealth of information.
I, with the new battery I now have, use regen only at 13- bars and battery temperature <30'C. I also charge the bike, for regular trips (to work,...), only up to 14 bars and discharge down to only 7+ bars. For longer trips I will charge fully.

I have 2 questions, if I may:
1. When the time comes (after 12 hours of riding time) and it's cool enough in the garage, I will let it do the full charging procedure with 4 hours of balancing. Then, I will do 'until the red battery telltale discharge' after that full balanced charge to reduce voltage depression. Is that ok, or is the second part not necessary? I do as shallow discharges as I can (longer lifetime).
//priuschat.com/forums/attachments/knowledge-base-articles-discussion/16468d1247111587-understanding-nimh-hypercycles-prolong-prius-hv-battery-life-nimh-life-cycle-dod.gif)
2. I'm now riding only up to 70km/h (aprox. 1C discharge). Is it ok to ride faster if the battery temperature permits it (30-'C) or will higher loads reduce battery lifetime?

Thank you for your reply.

jmap
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Re: Refrigerated Charging

What "The Laird" says makes sense to me but by reducing charge between 20% to 80%, the equalizing process is not done. The equalization is very important because the BMS doesn't protect well the cells, so if we stop the charge at 80% how can it be done?

I'm trying to adapt to the best practice for getting a bigger lifetime for the batteries without putting them in risk. My daily commute is 26Km and since it is not much I've extended the Vectrix recommendations. Before I would charge the bike every time it was possible, but most of the time she was above 80% and seems pretty clear to me now that is not recommendable at all to do that as a normal procedure.
So, right now, I am trying a new approach. I will recharge it when the battery is above and near 20%. Then I let it charge all the way to the end. I will take special care when the ambient temperature is high (>28ºC) by applying the "Refrigerated Charging" when the long equalization process occurs. I will stop doing shallow discharges because it always need to drop bellow 20% of the charge and it seems that is only needed for process a more accurate display range (bars and distance estimations). Since My daily commute is lo I will do a deep discharge every 2 months instead of the recommended 1.

AndY1
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Re: Refrigerated Charging

My trip to work and back is 25km and I try to keep my battery SOC between 80%-40% (14 bars - 8 bars). Just like Prius' NiMH pack.

The Laird
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Re: Refrigerated Charging

Hi Andy,

I hope that I have not been misleading anyone but my post on charging was stating the correct / ideal way to treat these batteries. Unfortunately we also have to account for the way Vectrix have 'arranged' the batteries and their omissions in respect of cooling and charge regulating.

Because of the lack of 'forced air cooling' when riding the batteries heat up and some cells heat more than others. This uneven heating causes the hotter cells to have greater losses and the cells slowly become 'out of step' with each other. This situation is worse with high speed riding, with hill climbing and with heavy regenerative braking. So, whilst the ideals have been stated, we now have to consider the built in problems of the vectrix.

Because the cells become 'unbalanced' the only way to get them back in line is to perform an equalising charge. Because the cells are getting hot, they have to be cooled. Vectrix have tried to correct their incompetent design by building into the software (latest version - Oct 2008?) extra cooling and regular equalising charges. So, unless you can provide 'forced air cooling' at all times AND equalise the temperatures throughout the battery the best way forward is to use what Vectrix have provided and allow the equalising charges and run the battery down to the red light as instructed.

However, you can improve the situation and extend the battery life by the following. Don't use regenerative braking when the battery is more than 80% full. Don't use full speed / full throttle particularly when the battery temperature is already high ( the higher the current taken from the battery the faster the battery heats up ). Always use the maximum possible delay when charging (the hotter the battery the longer the delay should be ). When the battery is due to perform an equalising charge, try to stop the charge just before the equalising charge is due to start and set at least a two hours delay before switching the charger back on. This is to allow further cooling before the equalising charge begins, it is necessary because the equalising current is too high and thereby causes unnecesary heat generation . O.K. I know that this is a fiddle to do but it will extend your battery life and some of this could be automated (time switches and alarms).

Please remember that what I have written is my interpretation of the situation. Other peoples opinions may differ. My opinions are based on fact and my engineering knowledge. If anyone wants more detail leave a message for me and I will respond either directly or through the forum.

The Laird

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Re: Refrigerated Charging

Hi!

Thank you for above reply.

If you have time and will to write in detail, please do so. I'm very interested in the inner workings and all that you can share with us.

clagros
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Re: Refrigerated Charging

Hi, until the ABCool will be fully comercial, I need urgently to do something regarding cooling, specially during charging.
Since I couldn't find any portable air conditioner below $1K, and my charging point is in the floor level of a building, I have no any possibility of installing an air conditioner down there, with the low risk of annoying questions and the high risk of not to find it there in the next morning.

That's why I was thinking about the two following posibilities:
1- Just putting a small fan which will also help to cool down the batteries before/ during/ after charging. This fan can be either connected to the same plugging point of the bike (so the fan has to be 220V) or (if the 12v plug of the glove box is active all the time), using a 12v small fan.
2- A second option, something between a simple fan to a real air conditioner, is to cool down the air with cheap air cooler (see link below):

PORTABLE 12 V BATTERY POWERED AIR CONDITIONER COOLER
PORTABLE AIR COOLER

This last option, can be better than the fan, not expensive and lees prone to be stolen. (We can discuss about condensation later).

In both cases, the question is the same: WHERE THE AIR FLOW HAS TO BE DIRECTED?
Some threads tell somewhere just above the front whell, between the fork, from the front towards the back.
That is probably not enough- where the incoming does air go? In order to get heat exchanging, it has to 'flow'.
Does enybody know what is the air flow direction of the battery cooling, and where exactly to place the fan or cooler?

Thanks!
Claudio

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Re: Refrigerated Charging

Above the front wheel, in the black plastic cover, there are two grills. Those are air intakes. The air is sucked in both of them and vented out above the rear wheel, near back suspension.

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Re: Refrigerated Charging

Above the front wheel, in the black plastic cover, there are two grills. Those are air intakes. The air is sucked in both of them and vented out above the rear wheel, near back suspension.

Yes but I did some tests with 2 external fans pointed to those but appears that the air admission is only done when the internal air flowing system is running. Bottom line, any external help (cooled or not) can only work efficiently when the internal flowing system is working.

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Re: Refrigerated Charging

(...) So, unless you can provide 'forced air cooling' at all times AND equalise the temperatures throughout the battery the best way forward is to use what Vectrix have provided and allow the equalising charges and run the battery down to the red light as instructed. (...)

Discharging until the red light appears is only for measure proposes... I mean, that is done only for the bar reading accuracy, have nothing to do with battery care, right?

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Re: Refrigerated Charging

It does if the battery develops memory effect.

http://en.wikipedia.org/wiki/NiMH_battery#Additional_information

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Re: Refrigerated Charging

It does if the battery develops memory effect.

http://en.wikipedia.org/wiki/NiMH_battery#Additional_information

But by doing one deep discharge every 2 months, that means that the "memory effect" possibility is small or null... I think...
With the first pack of batteries (with the old software) I've run 2000km without doing deep discharges and the range dropped about 30% but 2 deep discharges later, I had almost the top range again.

The Laird
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Re: Refrigerated Charging

The reason for the 'red light' discharge is to enable battery meter calibration at the low end of the 17 bar scale and also to reduce the effects of 'voltage depression' (also known as 'memory effect').

Duracell say 'The extent of voltage depression and capacity loss depends on depth of discharge and can be avoided by discharging the battery to an 'appropriate' cut off voltage'. They then suggest that a cut off voltage of between 1.0 v/cell and 1.15 v/cell would minimise with the lower cut off resulting in the least effect.

They also say that any reduction in capacity (caused through partial charge /discharge cycles) is reversible by carrying out deep discharges (to 1.0 v/cell). This would explain Jmap's experience of regaining capacity and range.

The most important issues with the Vectrix batteries is, without doubt, the problem of unbalancing the cells due to heating effects and, of course, the total lack of individual cell management/monitoring. Duracell say that the cell temperature should be between 10 and 30 degrees C (Maximum permissible of 45Degrees C) when charging. On discharge the temperature limits are 0 to 40 Degrees C (maximum permissible range -20 to +50 degrees C). I think that using the maximum permissible range would seriously reduce the battery's life expectancy.

It is practical to not do the deep discharge every week (if you accept a slowly reducing range) then, when the range is down to lowest level you can accept, carry out a couple of deep discharges (down to the red light) to bring the range back up to normal.

The business of the equalising charge is very different. Due to the unbalancing of the cells (the heating problem again) it is necessary to equalise on a regular basis. It has been said before, that the equalising current on the Vectrix is too high and has a greater effect on battery temperature than is necessary. Indeed, an extended duration charge at a rate of 2% to 5% of capacity (0.6Amps to 1.5Amps) would do far more good and far less damage than the present 3Amp equalising charge used by Vectrix.

Unfortunately there appears to be no way of changing the rate of equalising charge as it is totally controlled by the charger software. It is feasible, but probably potentially dangerous, to provide an external source of equalising charge at a more appropriate rate. Alternatively we must wait for the Vectrix software to be re-written (released to open source preferably) in order to improve the situation.

Incidentally, it is possible to run the plemnum fans (impellers) from a totally separate 12 Volt battery which could be accommodated under the rear seat. A 12volt yuasa NP18-12B, a fuse (10Amps), a switch and some 10Amps electric wire and one connector for the plenum impeller input (which is under the front seat) could be a simple and effective solution. (total cost about £50, total saving, one Vectrix battery at £4000 (if you can get one)) This battery would power the fans for up to three hours before requiring a recharge. I have tried this and it is effective. This idea could be further used whilst charging the Vectrix, just add a separate 12volt 6 to 8amp charger, (the plenum fans draw 5Amps remember).

By the way, the Vectrix charger is virtually unrepairable. I have looked inside. It would be easier to rip out the inards and redesign and rebuild the whole charger from scratch, which is what I shall do if and when mine stops working.

The Laird

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Re: Refrigerated Charging

On discharge the temperature limits are 0 to 40 Degrees C (maximum permissible range -20 to +50 degrees C). I think that using the maximum permissible range would seriously reduce the battery's life expectancy.

Does the battery life, on discharge, gets reduced only by battery temperature being over 40'C or does high load (100km/h speed), even at battery temperature of 20'C, also reduce battery life?

In other words, can I drive up to 100km/h with battery at 20'C-25'C (at all times) without getting reduced battery life? 19'C - 20'C is my battery temperature after a partial recharge in the morning, before I drive off to work.

R
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Re: Refrigerated Charging

can I drive up to 100km/h with battery at 20'C-25'C (at all times) without getting reduced battery life?

Theorically, going at 100km/h the battery only lasts 35 km. This give us an idea of the consumption; 35km/ 100km/h= 0.35h; 3kwh useful capacity/0.35h = 8.57kwh of consumption at 100 km/h; 8.57kwh/ 3.75kwh total capacity= 2.28 C discharge rate.

The battery can handle this level of discharge, however, take into account that I'm considering a flat road. A long uphill at 100 km/h will demand a tremendous amount of energy from the cells, and some kind damage to the battery is really possible. What's more, if your battery has any bad cell with reduced capacity, it might be possible that this hi discharge rate will affect the weaker cells, resulting into further damage and fast reduction of the battery life, due to lack of BMS. If you can avoid going faster than 70km/h uphill, you'll probable get extended life.

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Re: Refrigerated Charging

Thanx. I will continue to ride 70km/h as max speed.

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Re: Refrigerated Charging

Thanx

You're wellcome!
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Re: Refrigerated Charging

(...) carry out a couple of deep discharges (down to the red light) to bring the range back up to normal.(...)

I think they call that a shallow discharge (until red light appears). The deep discharge is only when the bike's velocity is lower (at plain road) than 24km/h.

jmap
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Re: Refrigerated Charging

The reason for the 'red light' discharge is to enable battery meter calibration at the low end of the 17 bar scale and also to reduce the effects of 'voltage depression' (also known as 'memory effect').

Duracell say 'The extent of voltage depression and capacity loss depends on depth of discharge and can be avoided by discharging the battery to an 'appropriate' cut off voltage'. They then suggest that a cut off voltage of between 1.0 v/cell and 1.15 v/cell would minimise with the lower cut off resulting in the least effect.

They also say that any reduction in capacity (caused through partial charge /discharge cycles) is reversible by carrying out deep discharges (to 1.0 v/cell). This would explain Jmap's experience of regaining capacity and range.

The most important issues with the Vectrix batteries is, without doubt, the problem of unbalancing the cells due to heating effects and, of course, the total lack of individual cell management/monitoring. Duracell say that the cell temperature should be between 10 and 30 degrees C (Maximum permissible of 45Degrees C) when charging. On discharge the temperature limits are 0 to 40 Degrees C (maximum permissible range -20 to +50 degrees C). I think that using the maximum permissible range would seriously reduce the battery's life expectancy.

It is practical to not do the deep discharge every week (if you accept a slowly reducing range) then, when the range is down to lowest level you can accept, carry out a couple of deep discharges (down to the red light) to bring the range back up to normal.

The business of the equalising charge is very different. Due to the unbalancing of the cells (the heating problem again) it is necessary to equalise on a regular basis. It has been said before, that the equalising current on the Vectrix is too high and has a greater effect on battery temperature than is necessary. Indeed, an extended duration charge at a rate of 2% to 5% of capacity (0.6Amps to 1.5Amps) would do far more good and far less damage than the present 3Amp equalising charge used by Vectrix.

Unfortunately there appears to be no way of changing the rate of equalising charge as it is totally controlled by the charger software. It is feasible, but probably potentially dangerous, to provide an external source of equalising charge at a more appropriate rate. Alternatively we must wait for the Vectrix software to be re-written (released to open source preferably) in order to improve the situation.

Incidentally, it is possible to run the plemnum fans (impellers) from a totally separate 12 Volt battery which could be accommodated under the rear seat. A 12volt yuasa NP18-12B, a fuse (10Amps), a switch and some 10Amps electric wire and one connector for the plenum impeller input (which is under the front seat) could be a simple and effective solution. (total cost about £50, total saving, one Vectrix battery at £4000 (if you can get one)) This battery would power the fans for up to three hours before requiring a recharge. I have tried this and it is effective. This idea could be further used whilst charging the Vectrix, just add a separate 12volt 6 to 8amp charger, (the plenum fans draw 5Amps remember).

By the way, the Vectrix charger is virtually unrepairable. I have looked inside. It would be easier to rip out the inards and redesign and rebuild the whole charger from scratch, which is what I shall do if and when mine stops working.

The Laird

I did not have feedback from the forum users to an old post... The last official info I've receive from Vectrix was related with our battery characteristics. They said that:
- NiMH batteries should not work with temperatures above 40ºC. Damage can happen in these cases. But, the NiMH batteries used on Vectrix can work with temperatures above 50ºC, and damage can only happen above 60ºC. Above 80ºC, the damage will be permanent.

So, do we have special NiMH batteries? Or is this info wrong?!
In doubt, I will try to continue keeping the temperature bellow 30ºC. That will not hurt them for sure, but I would like to know your opinion... please...

Mik
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Re: Refrigerated Charging

...
Incidentally, it is possible to run the plemnum fans (impellers) from a totally separate 12 Volt battery which could be accommodated under the rear seat. A 12volt yuasa NP18-12B, a fuse (10Amps), a switch and some 10Amps electric wire and one connector for the plenum impeller input (which is under the front seat) could be a simple and effective solution. (total cost about £50, total saving, one Vectrix battery at £4000 (if you can get one)) This battery would power the fans for up to three hours before requiring a recharge. I have tried this and it is effective. This idea could be further used whilst charging the Vectrix, just add a separate 12volt 6 to 8amp charger, (the plenum fans draw 5Amps remember).

...

What do you think of this setup (The ABCool 4.2)?

Photobucket
//i281.photobucket.com/albums/kk217/Mr_Mik/Vectux/Battery/ABCool/th_ABCool42.jpg)
Could it really be that easy? Or am I missing something?

One could of course use a 9s NiMH battery (instead of the 6s) and would not need the resistor; it would be more efficient that way.

The nice thing about a 6s NiMH battery in that place is that the fans run at their lowest possible speed with such batteries - and I have a heap of them!!
And the impellers should stop running before the battery is too empty - no BMS needed!

I need to experiment with the exact resistor value, but the ABCool 4.0 is ready and has an additional connector; this will make it easy to plug in the battery when it's ready:Photobucket

For those who cannot read the diagram: The 7.2V to 8.5V battery will get charged automatically whenever the ABCool is plugged into 120V-240V to cool the batteries. With the flick of a switch the battery can then be discharged through the cooling impellers, so that cooling with reduced air speed and reduced noise can be done during riding or parking.
The only problem is that it will override the 12V delivered by the stock system at those times when the battery is so hot that the impellers run during or after riding or charging.
It might even be that the relay coil will still *just* be active at the time when the battery voltage is so low that the impellers stop running. That could be disastrous at the wrong time.

According to the datasheet for the impellers ( http://www.comairrotron.com/cgi-bin/dcimpellerdatasht.pl?Pnum=039829&voltage=&airflow_val=&airflow_unit=CFM&pressure_val=&pressu...) they can use between 7V and 15V. So I could even put two NHW10 battery sticks in series, making 14.4V nominal, but fully charged the 15V limit might get exceeded.

I shall experiment!

This information may be used entirely at your own risk.

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

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