Dilemma with replacing my SLA batteries

[Footie]

I can't make up my mind - anyone care to advise?

The batteries in my electric MTB style bike are 8 months old and unable to give me a range greater than 7.5 miles (I have hilly terrain). I believe they are 7ah.
I can’t decide if it’s worth renewing the batteries – like for like. I only use the bike for leisure and pleasure. However, I would like a bigger range - say 12 or 15 mile.
I have been trying to decide if I were to replace them with 12ah batteries (slightly bigger and an increase in weight - about 5kg) would my distance be greatly improved?
.

 

[jimmyengland1000]

Do you mean that the increase in weight is 5kg? Or total weight of the battery? What's the weight of the present battery?

 

[john]

You would get much better range with 12Ah SLA than 7Ah.

The reason is that on an e-bike, you do no not get the full 7Ah from a 7Ah SLA battery because that rating is for lower current (1A if I remember). However, with a 12Ah battery you will be getting a greater proportion of that 12Ah since the battery will be better able to deliver the high current (due to it's lower internal resistance).

 

[Footie]

My original size 7ah batteries are rarer than rocking horse manure (110 x 85 x 100).
If I modify the case (length wise) I could fit modern 7ah batteries - on their ends. They are 151 x 95 x 65.
But, even replacing with 7ah means the weight will go up, as the batteries are bigger than the originals.

The weight difference is:
3 (12v 7ah batteries) = 6.3kg
3 (12v 12ah batteries) = 11.1kg
Increase of 4.8kg.
.

 

[Jeremy]

You could look at switching to a different battery type altogether. My 36V 10Ah LiFePO4 battery weighs 3.4kg without the case and cost around £150 including the charger. It's directly compatible with a 36V system, so should work OK.

My guess is that it would more than double your range and most probably pep the performance up a bit too, as the voltage on these LiFePO4 batteries doesn't sag down anywhere near as much under load.

If you're prepared for a bit of DIY, you may find that you can fit such a battery into the case you already have, although I've no doubt that some head-scratching and ingenuity might be required.

Jeremy

 

[Beeping-Sleauty]

LiFePo4 ?

My original size 7ah batteries are rarer than rocking horse manure (110 x 85 x 100).
If I modify the case (length wise) I could fit modern 7ah batteries - on their ends. They are 151 x 95 x 65.
But, even replacing with 7ah means the weight will go up, as the batteries are bigger than the originals.

The weight difference is:
3 (12v 7ah batteries) = 6.3kg
3 (12v 12ah batteries) = 11.1kg
Increase of 4.8kg.
.

had the sme problem with the size, just can't get these no more, and wanting more juice & range, i risked it and went for a set of Li Pings' 'duct tape LiFePo4 36v 10ah slim packs' these will fit the original case, in fact they will need extra packing, they weigh only 4.3 kgs in the case, as opposed to 10.6kgs for the SLA, i get 25 miles per charge from a brushed hub motor on a 40kg steel bike, they don't cut out ever and stay strong to the end of the battery, about £160 post paid on eBay, Li Ping is a good guy and instantly replaced a faulty BMS, communication is good, delivery time is good, i hope i'll have to wait about four years before i can tell you whether they're good for a 1,000 cycles tho'....LOL,


good luck, whatever you decide.

 

[Erik]

LiPing store: eBay Store - PingBattery: 36V LiFePO4 Batteries, 48V 24V Battery, Electric Bike Scooter

 

[Footie]

Thankyou Erik for posting the link.

i risked it and went for a set of Li Pings' 'duct tape LiFePo4 36v 10ah slim packs' these will fit the original case, in fact they will need extra packing, they weigh only 4.3 kgs in the case, as opposed to 10.6kgs for the SLA ....

Before I email Li Pings - Was this pack a special build just for you? Or was this one "off the shelf" so to speak?
No dimensions on the packs so don't know sizes.
.

 

[Beeping-Sleauty]

Li Ping LiFePo4

Thankyou Erik for posting the link.



Before I email Li Pings - Was this pack a special build just for you? Or was this one "off the shelf" so to speak?
No dimensions on the packs so don't know sizes.
.

look for one like this:

36V 10AH LiFePO4 Electric Scooter E Bike Li-Fe Battery! on eBay, also Parts Accessories, Scooters, Outdoor Sports, Sporting Goods (end time 18-Mar-08 17:36:02 GMT)

Slim Sized, 280x110x80 mm, 11x4.5x3 inch, <8 lbs - this will fit your SLA case, it will be loose and will need extra packing, especially underneath as these are soft cell protected only by duct tape,

see some photos & a good ( if lengthy ) forum item here:

Endless-sphere.com &bull; View topic - Duct Tape E-Bay Lifepo4s???

email Li Ping (pingping227@hotmail.com) with the type of motor you are using and state this spec + size, he will build one and list it on eBay, this is his normal practice, make sure you get a BMS ( battery management system ) that can handle the peak amps draw of your motor, 20 amps should be enough.

delivery is about 10 days, Li Ping will send you a tracking number, it will arrive EMS via Parcel Force. ( a modern version of 'knock down ginger') so make sure someone is in to sign for it.

ensure you have a fuse & a keyswitch in the circuit, if you have any problems please let me know.

good luck
beeps

 

[Footie]

Thanks Beeping-Sleauty
I tried emailing you but not able to do so, that option is being blocked.
So I will have to contact you via the forum.

I know very little about electrics, etc, and I have a feeling I'm going to make myself look foolish now, but I have to ask this - what's a battery management system? This is something I'm unsure about.

The bike is fitted with a key switch and inline 25 amp fuse inside the battery box.
I’m confident enough to compare what already in the box and follow the basic logic of how it’s wired up. I’m hoping I can just pop the new batteries in, connect the power leads and away I go. Are there major differences between SLA batteries and LiFePo4 batteries? I'm I being too optimistic?

My motor is a built in, brush-less rear hub - 36V 200W motor.
That's all I know - Is that enough information for Li Pings do you think?
.

 

[Jeremy]

Footie,

You don't need to worry about the Battery Management System (BMS) as it's a sealed unit that is already connected to all the cells in a Li Ping LiFePO4 pack.

The BMS monitors each cell voltage during discharge and cuts the power off if any cell reaches a critically low state of charge, as a protection measure. It also monitors the discharge current and will turn the pack off if the rate of discharge is too high. Finally, the BMS works as a "smart charger" to ensure that each cell in the pack reaches exactly the same state of charge when being charged up, by balancing the cells.

The only practical implications of this are that the battery pack has three wires coming from it, rather than just two. The positive lead is used for both charge and discharge, but there are two negative leads, clearly marked. One is for charging and the other is for discharging. It's important that you connect the charging socket to the charge lead and wire the bike electrics up to the discharging lead. Both connect to the same positive lead.

There are instructions with the packs that come from Li Ping, making it fairly easy to connect up. He also supplies the connector to match the connector that the charger supplied comes with, making it fairly simple to hook everything up.

As one or two of us here have already done this mod, I think you should find it easy enough to get the advice you need, should you decide to go down this route.

Jeremy

 

[Footie]

Thankyou Jeremy.
I did some searching and, as you say, the BMS should be part of the battery pack.
Think I've messed about long enough - I've just sent an email to Li Ping - so I've started the ball rolling
.

 

[Beeping-Sleauty]

Thanks Beeping-Sleauty
I tried emailing you but not able to do so, that option is being blocked.
So I will have to contact you via the forum.

I know very little about electrics, etc, and I have a feeling I'm going to make myself look foolish now, but I have to ask this - what's a battery management system? This is something I'm unsure about.

The bike is fitted with a key switch and inline 25 amp fuse inside the battery box.
I’m confident enough to compare what already in the box and follow the basic logic of how it’s wired up. I’m hoping I can just pop the new batteries in, connect the power leads and away I go. Are there major differences between SLA batteries and LiFePo4 batteries? I'm I being too optimistic?

My motor is a built in, brush-less rear hub - 36V 200W motor.
That's all I know - Is that enough information for Li Pings do you think?
.

Hi Footie, wandered off to watch a movie & missed this posting,

when you have both batteries before you, it will be obvious what goes where with the help of Li Pings' wiring diagram.

the BMS is the shrink wrapped card taped to the side of the battery and the wires come out of it, i put extra padding on this side of the battery to protect it.

the first time you charge up the battery it may take 10 hours, this is normal, the charger keeps re-starting and is balancing the individual cells.

following instructions i read elsewhere, i conditioned the pack by charging & discharging to empty 3 times.

after the conditioning, the first distance trial returned 21.5 miles, have now charged the battery 10 times and the distance is up to 25.1 miles, so it seems to be still bedding in.

After using a rather well-worn SLA, this LiFePo4 battery made the bike feel like new.

i'm delighted with this battery (so far), hope you will be too.

let us know how you get on.

beeps

 

[keithhazel]

after the conditioning, the first distance trial returned 21.5 miles, have now charged the battery 10 times and the distance is up to 25.1 miles, so it seems to be still bedding in.
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is that miles pedal assist or power alone ?
keith

 

[Beeping-Sleauty]

after the conditioning, the first distance trial returned 21.5 miles, have now charged the battery 10 times and the distance is up to 25.1 miles, so it seems to be still bedding in.
-------------------------------------------------------------------------
is that miles pedal assist or power alone ?
keith

That's comfortable pedalling all the time.... no pedal assist, just enough throttle to keep the pedalling nice'n'easy. Haven't tried power alone.

looks like a nice day, so might give it a whirl.

yee-hah, whup that donkey
beeps

 

[Footie]

Just paid Ping for new battery.
$299.00 USD
A few emails and an easy straightforward transaction through PayPal.
All I can do now is wait for it to arrive
.

 

[Footie]

Ping has just emailed me, to say my battery has tested ok and has been shipped.
Just hope the weather stays good for a safe and speedy crossing
.

 

[Footie]

By the way, if anyone does not want to go down the LiFePO4 battery route.
I have found some of the old size batteries at Powered Bicycles - size 110mm X 86mm X 101mm
Unfortunatly, they are no good to me as my North Cornwall hills kill my 7.2ah SLA batteries, which is why I have gone for a LiFePO4.

Parts - electric bikes - moto352
.

 

[Footie]

My new battery has arrived.
2 weeks and 2 days from order to arrival

LiFePO4 on Flickr - Photo Sharing!
.

 

[Beeping-Sleauty]

good luck fitting your new batt Footie, let us know how you get on,
beeps