Sakura Charger query

[electric.mike]

Yes I am, although I have only just started getting used to riding a bike again, let alone an electric one. The last time I got on a cycle was over 70 years ago, so you can guess what fun I had learning to ride the Sakura. I thought first of all it was too heavy (40 kilos) but I have gradually got used to it and have bought it mainly to get me to and from my Golf Club. I am getting rid of my car and going back to basics but only time will tell over the Winter whether I manage it or not.

With regard to the Sakura, as long as the batteries last and my knees don't give way, I am very happy with it. By the way, the only concern I have is the location of the battery L & N connections at the bottom of the battery case where they sit in the frame and connect to the motor wiring circut. When it rains, have you ever experienced water forming in the bottom tray and affecting the electrics, as it seems an obvious water trap to me. I have not been out in the wet yet, so don't know if I am worrying over nothing but perhaps you can enlighten me.

Regards
Bernie

Cant help with the water situation as our sakuras are different.

 

[Bernie2]

The only way to tell is to measure the voltage of the battery, while it is connected to the charger once the charge cycle is complete. SLA's can be safely held at a standby voltage by a charger with the capability to do so.

I'm sorry but I don't quite understand your reply. I can certainly measure the voltage at the end of the charge cycle and frequently do but what does that tell me in so far as knowing if my charger has switched off. Or are you saying I could measure the current when the green light appears and whilst the battery is still connected. That would probably tell me if the charger has stopped charging or whether it continues a trickle charge. As I don't want to get any shocks while I'm doing this, can you confirm that that is what you had in mind, as I regret that I don't understand your second sentence.

 

[Alan Quay]

.... I don't want to get any shocks while I'm doing this....

36v is extremely unlikely to do you any harm. Because the battery is isolated from Earth, you would have to grasp both positive and negative terminals at the same time. If you did this there is a theoretical chance of a dangerous level of current passing through you, but in practice, you won't even feel it.

I guess the biggest danger is from burns caused by shorted battery, but this is pretty low risk/consequence.

 

[danielrlee]

I'm sorry but I don't quite understand your reply. I can certainly measure the voltage at the end of the charge cycle and frequently do but what does that tell me in so far as knowing if my charger has switched off. Or are you saying I could measure the current when the green light appears and whilst the battery is still connected. That would probably tell me if the charger has stopped charging or whether it continues a trickle charge. As I don't want to get any shocks while I'm doing this, can you confirm that that is what you had in mind, as I regret that I don't understand your second sentence.

No, I mean voltage. Measuring current will tell us something, but it won't tell us if the battery is being charged or held at an incorrect voltage. Also, measuring voltage is usually easier since the circuit doesn't have to be 'broken' as when measuring current inline. As long as you don't go probing inside the charger, the risk is minimal. As Mike said, the biggest risk would be if you were to accidentally short the battery.

Having had time to think about this, I would be surprised if it wasn't safe to leave the charger connected for longer periods of time. If the charger has the logic built in to tell you the charge is complete, it would seem silly to not also have the charger cut the current at this point. This isn't a given though - often many a corner is cut to save a few pence at manufacturing.

To test, you will need to find a way of connecting a multimeter or wattmeter while the battery is charging. If you wish to do so, I will provide further information.

 

[Bernie2]

No, I mean voltage. Measuring current will tell us something, but it won't tell us if the battery is being charged or held at an incorrect voltage. Also, measuring voltage is usually easier since the circuit doesn't have to be 'broken' as when measuring current inline. As long as you don't go probing inside the charger, the risk is minimal. As Mike said, the biggest risk would be if you were to accidentally short the battery.

Having had time to think about this, I would be surprised if it wasn't safe to leave the charger connected for longer periods of time. If the charger has the logic built in to tell you the charge is complete, it would seem silly to not also have the charger cut the current at this point. This isn't a given though - often many a corner is cut to save a few pence at manufacturing.

To test, you will need to find a way of connecting a multimeter or wattmeter while the battery is charging. If you wish to do so, I will provide further information.

 

[Bernie2]

Many thanks once again. Having read what everyone has to say, including your goodself, I have decided to leave well alone and accept that I may never know if the charger switches off or not. Like you say, I don't think it will do any harm to leave it on for a while after the "Green" light shows and I have decided to use a timed plug socket just to be on the safe side and adjust the "on" hours if necessary. Many thanks all of you for your helpful input.

Happy E-biking !

 

[Blew it]

I have decided to leave well alone and accept that I may never know if the charger switches off or not.

There is a simple way to find out. Purchase an energy consumption monitor for a tenner. When the charger is actively charging the batteries, the monitor will show around 50-70w. When the charge indicator turns green, the consumption will reduce to just a couple of watts...the power used by the chargers electronic components.
These consumption monitors have many uses around the home, so not a waste of money.

The resident "experts" will of course disagree

http://www.maplin.co.uk/p/13a-plug-in-energy-saving-monitor-n67fu

 

[danielrlee]

There is a simple way to find out. Purchase an energy consumption monitor for a tenner. When the charger is actively charging the batteries, the monitor will show around 50-70w. When the charge indicator turns green, the consumption will reduce to just a couple of watts...the power used by the chargers electronic components.
These consumption monitors have many uses around the home, so not a waste of money.

The resident "experts" will of course disagree

http://www.maplin.co.uk/p/13a-plug-in-energy-saving-monitor-n67fu

This will not tell you the whole story. I have come across SLA chargers that hold the cells at a voltage higher than is recommended and although at this point very little current flows, the electrolyte continues to boil away.

The saving grace with lead acid batteries though, is that they are about as 'safe' as a battery can be. Although there is a small risk of an explosion due to over-pressurisation, the fire risk is pretty much zero. In reality though, an explosion is unlikely because of the way that the hydrogen produced is vented. This is what the hissing sound is when an SLA is charged to an excessive voltage.

 

[Blew it]

It's an electric bike, not a WW2 diesel-electric submarine. Nice example of "gish-galloping" though.

Bernie2 wanted a safe way of finding out if his charger shut down when the battery was fully charged. The electrolite in the lead-acid batteries used in electric bikes is in gel form. When gel batteries reach the end-of-life due to high internal resistance, some corrosive liquid may escape through the venting ports but no appreciable gassing will occur.

 

[danielrlee]

It's an electric bike, not a WW2 diesel-electric submarine. Nice example of "gish-galloping" though.

Bernie2 wanted a safe way of finding out if his charger shut down when the battery was fully charged. The electrolite in the lead-acid batteries used in electric bikes is in gel form. When gel batteries reach the end-of-life due to high internal resistance, some corrosive liquid may escape through the venting ports but no appreciable gassing will occur.

What Bernie has asked isn't all he needs to know and I can only repeat what I've already said. A watt meter that sits between the mains socket and charger will not tell him the voltage that the charger is holding the battery at. This is an important piece of information and needs to be known if we are to tell him that it is safe to leave the charger connected. Anything else would be guessing.

EDIT: In my opinion, the best SLA chargers never 'turn off', but instead monitor the battery voltage and when it drops below the 'float voltage', momentarily applies power to make sure the battery is always fully charged. It will then return to the monitoring stage and continue this cycle indefinitely. This solves the self-discharge issue that SLA's suffer, especially when there are long periods between usage.