Do ebike controllers protect SLA batteries?

[James M]

I have been using an ebike conversion kit for nearly 3 years now. Recently I purchased a new conversion kit, both kits were 24v 250watt.

It seems this new kit has control over the batteries and my battery meter on the bike tells me the battery is flat and the motor cuts out for a few seconds then comes back on.
I usually can cover 5miles confortably with two 12v 12ah sla batteries,

After purchasing two brand new sla over xmas, I found the batteries cut out before I get to and from work, I put it down the battey, then thought maybe the controller has some sort of device that stops the battery getting too discharged because I measured the voltage of my batteries straight after my journey ''after the batteries were supposed to be dead'' and the voltage on both read 12.60v

Its annoying my bike motor cuts out on me even though it seems the batteries are ok.

Anyhelp or advice and even knowledge on this would be grateful!! nice one

 

[Deleted member 4366]

It sounds like you've bought the wrong type of batteries. What's the designation written on them and the brand name?

The controller limits the discharge to about 20v. Your are sagging under load, so the controller cuts off. The voltage then bounces back up and the controller allows power again, but as soon as you take power, down they go.

 

[selrahc1992]

I have been using an ebike conversion kit for nearly 3 years now. Recently I purchased a new conversion kit, both kits were 24v 250watt.

It seems this new kit has control over the batteries and my battery meter on the bike tells me the battery is flat and the motor cuts out for a few seconds then comes back on.
I usually can cover 5miles confortably with two 12v 12ah sla batteries,

After purchasing two brand new sla over xmas, I found the batteries cut out before I get to and from work, I put it down the battey, then thought maybe the controller has some sort of device that stops the battery getting too discharged because I measured the voltage of my batteries straight after my journey ''after the batteries were supposed to be dead'' and the voltage on both read 12.60v

Its annoying my bike motor cuts out on me even though it seems the batteries are ok.

Anyhelp or advice and even knowledge on this would be grateful!! nice one

Hi James, here's to teh least knowledgeable and experienced member of teh forum replying to your post! but here goes: as far as i know yoru controller will have something called a LVC (low voltage cutout) to protect batteries - i.e. it will cut off power from teh batteries (using - i think - something called a shunt that regulates/monitors current by measuring resistance over a thick wire). It would be good to know which kit you have? other form members may know how/whether you can adjust LVC in the software

 

[James M]

Thankyou both for the replies, the batteries I am using at the moment are two 12v 12ah lucas batteries.

My previous ebike conversion kit was from a comapny called vkpower. Not very expensive but i had it a few years until last november. It packed in which now I believe was the controller. But anyway, i purchased a new kit from the same company, same power and all, slightly differrant in design, but since I have used this kit, my new lucas batteries are performing the same as a pair of batteries I have had for about 8-10 months.

Now I am unsure if its the batteries or the new kit controller which is just protecting the batteries abit TOO much. But as I say, i dotn have technical knowledge on these things,

I will say, on my old kit when the batteries would cut out, the used to measure about 12.2, 12.3, but now on this new kit, last night they measured 12.6, that to me is not a dead battery, its jsut very annoying when you have to pedal a heavy ebike beacuse the motor cuts out!!

Maybe the new design of kit is only designed for the more expensive lithuim or lifePo4?

 

[James M]

View attachment 10400 Thankyou both for the replies, the batteries I am using at the moment are two 12v 12ah lucas batteries.

My previous ebike conversion kit was from a comapny called vkpower. Not very expensive but i had it a few years until last november. It packed in which now I believe was the controller. But anyway, i purchased a new kit from the same company, same power and all, slightly differrant in design, but since I have used this kit, my new lucas batteries are performing the same as a pair of batteries I have had for about 8-10 months.

Now I am unsure if its the batteries or the new kit controller which is just protecting the batteries abit TOO much. But as I say, i dotn have technical knowledge on these things,

I will say, on my old kit when the batteries would cut out, the used to measure about 12.2, 12.3, but now on this new kit, last night they measured 12.6, that to me is not a dead battery, its jsut very annoying when you have to pedal a heavy ebike beacuse the motor cuts out!!

Maybe the new design of kit is only designed for the more expensive lithuim or lifePo4?

Sorry the company is vpower not vkpower

 

[Deleted member 4366]

We need the number written on the side of the battery.

 

[James M]

Which number D8veh?
YOu think they might be wrong type? they are 12v 12ah designed for electric vehicles, I have used these types of batteries before, probably got thru about 4sets over 3 years, differant makes like Yuasa.

 

[Deleted member 4366]

Every battery has a designation written on it. Something like LSLA12-12.

 

[James M]

Hi there, it has exactly what you wrote LSLA 12-12

 

[Deleted member 4366]

They should be OK if they were sold in good condition. Your theory about the controller cutting high is good, but unlikely. All controllers cut off at a certain voltage, but I've never heard of one getting it wrong apart from 36v/48v dual voltage ones, where they were set to 48v with a 36v battery. If your controller was a 36v one, it would cut off at about 30v, so it would never allow power with a 24v battery.

To solve your problem, you need to fit a voltmeter that you can see while riding your bike so that you can see if the voltage drops when you open the throttle.

The other possibility is a bad connection on the battery somewhere or anywhere between the battery and controller. If you have a loose or dirty spade connector on the battery, you'd get the symptoms you've described.

You can get digital voltmeters from Ebay for a couple of quid, or you can get a cheap wattmeter (£8), which you can use as a fuel guage, so you'll know how much further you can go.

 

[James M]

Nice one, I have a voltmeter so I will try that on my travels tomorrow. I will post results. Thanks for your help

 

[James M]

Hi again,

The motor cut out at 19.5 volts,
5mimutes later when igot home the batteries measured 12.61volts each after they had been discnected and put on to.charge

 

[Deleted member 4366]

The cutting out is at the correct voltage. For whatever reason, your batteries are behaving as if they're worn out. Did you leave them flat for a bit, which damages them? You'll need new batteries whatever the reason for their demise.

 

[James M]

Thanks for your help,

I just think I have been sold dodgy set of batteries. I should be able to get a refund or new set sent as I have only had them 1 month.

Weird though that the voltage reading is so high once I disconnected them and put the volt meter on each one. In the past when the motor cuts out, the reading on the battery would usually be like 12.20, and its usually the one battery that is very low compared to the other, but these are both the same. Anyway, it's the batteries, so least I can get a new set knowing its not my controller cutting out at a higher voltage.

Again thanks for the tip on connecting the volt meter!

 

[Deleted member 4366]

It's called voltage sag. When you take current from a battery, the voltage sags down. The amount of sag depends on the battery's ability to provide current. Knackered and unsuitable batteries sag a lot. The voltage will bounce back when the current reduces. You should be able to see this effect with your voltmeter.

 

[James M]

Yeah, I noticed it bounced back up to about 23.5 or higher just after the motor cut out.

Was interesting seeing it though, didnt realise the volatage dropped so low under load.

Again, thanks for your help.

 

[flapajack]

This happens a lot with a knackerred battery. Voltage sags hugely as soon as you draw current, but notices back once stop. The batteries are not holding charges. Most noticeable on a motorbike when trying to crank the starter motor.

 

[jimmyhackers]

12ah should be enough for 250w. i run 4x 12v 20ah sla on a 48v 1000w, and they're all second hand

what are you using to charge the batteries? maybe its not topping them up correctly. i use an official skyrc b6 max, its probably the best smart charger out there for the money, 20quid on ebay, if you do get one make sure you get an official skyrc, ive had a naff cheap clone go funny on me.

sla's should charge at/upto 14.7 volts and sit at around 13volts for a few days after a good charge. if you have a voltmeter handy see what volts its at on and after charging

having a volt meter connected up to each battery individually (one at a time if you only have one meter like me) and then going for a ride will let you see what the battery is upto under load and the scale of the battery sag.

ive been through a fair few second hand slas (about 20 in total) testing this way to find the best 4 for my rig (plus 4 spares ).

you said yours are new so just take em back if they fail either of the above tests (unless your chargeres at fault then get a new one).

i thought id just add some info if they wernt new batteries.

ive had about a 1 in 4 success rate with broken slas, just by adding about 10ml of distilled water to each cell, leaving to sit for a week. then recharging.

1 in 4 are fine/near full restored capacity
1 in 4 half restore capacity
2 in 4 go dead, get really hot, debalence badly, overvolt, make lovely paperweights.

how far gone usually decides how far they can come back

hope that helps

p.s. sorry to whine about the skyrc b6 max, but when/if you progress to a lifepo4 or lipo battery itll charge them perfectly too.

 

[James M]

12ah should be enough for 250w. i run 4x 12v 20ah sla on a 48v 1000w, and they're all second hand

what are you using to charge the batteries? maybe its not topping them up correctly. i use an official skyrc b6 max, its probably the best smart charger out there for the money, 20quid on ebay, if you do get one make sure you get an official skyrc, ive had a naff cheap clone go funny on me.

sla's should charge at/upto 14.7 volts and sit at around 13volts for a few days after a good charge. if you have a voltmeter handy see what volts its at on and after charging

having a volt meter connected up to each battery individually (one at a time if you only have one meter like me) and then going for a ride will let you see what the battery is upto under load and the scale of the battery sag.

ive been through a fair few second hand slas (about 20 in total) testing this way to find the best 4 for my rig (plus 4 spares ).

you said yours are new so just take em back if they fail either of the above tests (unless your chargeres at fault then get a new one).

i thought id just add some info if they wernt new batteries.

ive had about a 1 in 4 success rate with broken slas, just by adding about 10ml of distilled water to each cell, leaving to sit for a week. then recharging.

1 in 4 are fine/near full restored capacity
1 in 4 half restore capacity
2 in 4 go dead, get really hot, debalence badly, overvolt, make lovely paperweights.

how far gone usually decides how far they can come back

hope that helps

p.s. sorry to whine about the skyrc b6 max, but when/if you progress to a lifepo4 or lipo battery itll charge them perfectly too.

Yeah, Iv been using an elec bike for about 3 years now, Have gone through a few sets of batteries,

The chargers I use will charget he batteries to about 14.7 then the light on the charger goes green.

I got rid of the Lucas batteries, the company who sold them wanted me to post them back and await a test to see if I was basically telling the truth, not worth the time or money.

Bought two 12v 15ah batteries, They are the same weight and size as the 12ah, These ones are fine, can get to my destination with no struggle on the batteries.

4x 20ah you use?!!! I thought 2x 12ah were heavy! YOur bike must weigh a tonn! haha

 

[jimmyhackers]

28kg of batteries. 15kg of bike and about 5 kgs of hub motor. probably best that i only weigh ten and a half stone : D

the static weight of it is something you can really feel (so could the three bike stands ive broken) pushing/manouvering it about under my steam is some exercise.

funny thing is as soon as im up n running, its feels like its as light as air.