Newbie question, car lead acid batteries, 4x12v in a trailer. so weight not a problem.

Markja

Finding my (electric) wheels
Aug 8, 2017
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Have tried searching but no joy.
Can anyone help to either poo poo my idea or say it's a good 'un.
I can get 4x12v car batteries for free, (and swop for new when they die.) Can i put them in my trailer (so weight no issue) and just wire them (correctly wired with a fuse) to the power wire of my normal 48v battery on bike?
Would there be any issues with the control unit, or anything else?
 

cosybike

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Mar 30, 2009
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Have tried searching but no joy.
Can anyone help to either poo poo my idea or say it's a good 'un.
I can get 4x12v car batteries for free, (and swop for new when they die.) Can i put them in my trailer (so weight no issue) and just wire them (correctly wired with a fuse) to the power wire of my normal 48v battery on bike?
Would there be any issues with the control unit, or anything else?
Entirely possible. Stupid idea though. Send pictures when it's done. Get a wee honda generator in there while you are at it.

Sent from my Lenovo YT3-850F using Tapatalk
 
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Deleted member 4366

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You can wire them to your controller using the wires that would normally go to the battery. Take out the original battery.

It'll work, but seems pointless to me. Your motor will hardly have enough power to pull you and those batteries up a hill. Your bike won't be fun to ride.
 
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Markja

Finding my (electric) wheels
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Entirely possible. Stupid idea though. Send pictures when it's done. Get a wee honda generator in there while you are at it.

Sent from my Lenovo YT3-850F using Tapatalk

Thanks for the helpful reply. Maybe explain why it's a stupid idea? I bow down to your high intellect.
 

Markja

Finding my (electric) wheels
Aug 8, 2017
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Watford
You can wire them to your controller using the wires that would normally go to the battery. Take out the original battery.

It'll work, but seems pointless to me. Your motor will hardly have enough power to pull you and those batteries up a hill.
Your bike won't be fun to ride.
Thanks d8veh, it's not because i need to, its just an exercise in can i do it, and i have a 48v 1000w motor so hills aren't a problem. Sometimes i go to the local supermarket with the trailer for the weekly shop. No problems towing it all home. Just thinking maybe go to supermarkets further away.
At least your reply was helpful. (Yes, even my mates say I'm an idiot! Ha ha.)
 
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Deleted member 4366

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A 1000w motor will probably be worse if it's a direct drive one. They like to run at high speed otherwise they get too hot and burn.
 
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cosybike

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Mar 30, 2009
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I could explain why but life is too short to engage with a suspected forum troll who knows fine well he's asked a stupid question and wants a rise out of us. Pictures with a recent newspaper in shot or we are wasting our time. Sceptometer at 10.

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anotherkiwi

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Jan 26, 2015
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Can i put them in my trailer (so weight no issue)
Because you have a magical trailer with a force field that eliminates weight? The weight doesn't go away it is just moved behind the rear wheel and something (a motor?) needs to move it and brakes need to stop it.
 

Markja

Finding my (electric) wheels
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Because you have a magical trailer with a force field that eliminates weight? The weight doesn't go away it is just moved behind the rear wheel and something (a motor?) needs to move it and brakes need to stop it.
Nope, not what i meant. having the trailer will obviously not get rid of the weight but move it away from the bike its self. The trailer i have has, as stated in previous reply, been used for supermarket trips so i know it can be towed easily with weight in it. I wanted to try to understand any problems, limits, reasons why not to try using batteries in the trailer.
But it seems there are a few anal, better than thou' children on this forum. (Most forums have them.)
If i want a spot of trolling I'll go on Facebook.
 

Markja

Finding my (electric) wheels
Aug 8, 2017
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Thank you to d8veh.
I didn't know about the direct drive motors getting hot if under speeding. I would have thought that the greater the speed the hotter they'd get. So learnt something new today.
I will be trying the batteries in the trailer. Then I'll report back as to how successful the project was. Either a great trip to far away mystical supermarkets or an absolute pain cycling home with fried motor/electrics.
 

anotherkiwi

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Nope, not what i meant. having the trailer will obviously not get rid of the weight but move it away from the bike its self. The trailer i have has, as stated in previous reply, been used for supermarket trips so i know it can be towed easily with weight in it. I wanted to try to understand any problems, limits, reasons why not to try using batteries in the trailer.
But it seems there are a few anal, better than thou' children on this forum. (Most forums have them.)
If i want a spot of trolling I'll go on Facebook.
The weight is still there, whether you move it from the bike to a trailer or not is irrelevant. Having it in a trailer will mean greater braking problems than if it was on the bike for example. It still requires the same amount of energy to move.
 

rich_r

Pedelecer
Jun 23, 2017
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I ran with three 5Ah sealed lead acid batteries for a bit whilst waiting for my 36V lithium bottle battery to arrive. They went in a box on the rear rack, totaling about 15kg. The weight is very noticeable even with those small lead acid batteries.

Also the voltage started at 38V and when it gots below 35V performance starts to drop off noticeably. To be fair, I did only have 5Ah, so probably pulling a bit much current for the batteries on hills when the hub motor was consuming around 350W. However I guess your batteries won't have this issue if they're car ones.

Certainly no harm in trying it - just keep an eye on the voltage so you don't discharge them too much.
 
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Markja

Finding my (electric) wheels
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I ran with three 5Ah sealed lead acid batteries for a bit whilst waiting for my 36V lithium bottle battery to arrive. They went in a box on the rear rack, totaling about 15kg. The weight is very noticeable even with those small lead acid batteries.

Also the voltage started at 38V and when it gots below 35V performance starts to drop off noticeably. To be fair, I did only have 5Ah, so probably pulling a bit much current for the batteries on hills when the hub motor was consuming around 350W. However I guess your batteries won't have this issue if they're car ones.

Certainly no harm in trying it - just keep an eye on the voltage so you don't discharge them too much.
Yep, going to try car ones. Guy next door scraps cars and removes the batteries before taking them to scrapyard. So I'll try 4 same size ones.
Thanks guys, just needed pointers on anything to look out for.
 
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Deleted member 4366

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Thank you to d8veh.
I didn't know about the direct drive motors getting hot if under speeding. I would have thought that the greater the speed the hotter they'd get. So learnt something new today.
I will be trying the batteries in the trailer. Then I'll report back as to how successful the project was. Either a great trip to far away mystical supermarkets or an absolute pain cycling home with fried motor/electrics.
That's right. It's counter-intuitive. The faster a motor runs, the better it is for it. Turning that around, forcing a motor to give maximum power when it's turning too slow will over-heat it.

If you want to keep your motor, you need to keep stopping to check the temperature, and avoid any hills.
 

rich_r

Pedelecer
Jun 23, 2017
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Yep, going to try car ones. Guy next door scraps cars and removes the batteries before taking them to scrapyard. So I'll try 4 same size ones.
Thanks guys, just needed pointers on anything to look out for.
I'd got for the smallest you can find. Some modern cars have little 25Ah batteries which should be plenty of capacity for an e-bike and weigh the least. I suspect four 110Ah car batteries would be a bit of a strain on your trailer's axle, let alone the motor trying to pull it!
 

Danidl

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Sep 29, 2016
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Thank you to d8veh.
I didn't know about the direct drive motors getting hot if under speeding. I would have thought that the greater the speed the hotter they'd get. So learnt something new today.
I will be trying the batteries in the trailer. Then I'll report back as to how successful the project was. Either a great trip to far away mystical supermarkets or an absolute pain cycling home with fried motor/electrics.
Hi Marjka,
Now you have heard a number of facts from other experts so I will add my tuppence worth.
What you are doing is very feasible and unless you are cash strapped as sensible as reverting to vinyl disc records. ( That will raise a few hackles!!!).
Lead acid batteries , particularly for cars have been designed for a specific purpose.. huge current surges or cranking power, limited capacity and poor life cycle . When they were the only option they were used but that is three generations ago. Deep discharge batteries also called leisure batteries are better but only in comparison to car batteries.
The three problems are .. poor energy density .. energy stored per kilogramme.
Poor lifetime .. noticeable degradation in capacity after 50 charge discharge cycles, subject to sulphation.. if left discharged for any time they are knackered.
The only advantages is they were cheap and available. None the less there are still electric vehicles using lead acid batteries including milk floats, early generation forklifts and mobility scooters.. and submarines
d8veh is correct in that the motors used in ebikes need to be run close to their designed speed. If the motor is allowed stall, the current drawn by the motor becomes enormous, and can soon melt the windings. However a stalled motor will have a lot of torque, and hopefully starts rotating. When the motor rotates it creates a voltage which opposes the applied voltage and therefore reduces the overall current to a safe level.
So why not carry on and enjoy the experience (just like those vinylheads)
 
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Deleted member 4366

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One time when I was out for a ride, i met a guy towing a trailer, so I went closer to have a look. That's when I noticed that there was a big motor in his front wheel. It was one of those big 24v ones that you used to get on the bikes that had SLA batteries. He had two car batteries and his tools in the trailer. I tried lifting it to feel the weight, but I couldn't get it off the ground. It seemed to go OK, but that was a slow motor and only two batteries. I'm pretty sure that 4 batteries and a 1000w DD motor is not going to work, but you can try it anyway, so that we can learn from your experience. You'll need a pretty good coupling to handle that sort of weight.

It might be better if you get a 24v controller and use only two batteries. That'll run the motor at half speed, so it'll be a lot more efficient and lighter. Even 36v would be better that 48v. You'll need about 40 amps though, so the controller might be expensive.
 
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Markja

Finding my (electric) wheels
Aug 8, 2017
10
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63
Watford
Thanks guys, i will take note of the idea of maybe dropping the overall voltage and other suggestions.
As i said, batteries are free from neighbour so if they die i just get a new one.
This is just a bit of tinkering in my shed for my own experience. Not a radical reshape the world thing. (Think 'Last of the Summer Wine'.)
 

Nealh

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Aug 7, 2014
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Go for it their free, would be different otherwise.
 
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