Help! Introduction and request for advice on a new battery :)

[Fluffybirb]

Hello there! Very nice to meet you all

My name's Lee and I'm new here after finding these forums while researching how to affordably replace my ebike battery. Everyone seemed so friendly and knowledgeable so I thought maybe I could ask for some help here as I've been unable to use it since the beginning of the year and I'm desperate to get back out on it again.

Quick disclaimer of sorts at first - I have autism and ADHD, so it may take me a little time to fully understand and absorb any answers, and I often ask clarifying questions. I hope that's OK!

Background:
I bought a FreeGo Eagle a year or so ago second hand, and the battery was still working but I think was a bit old. The indicator light on top didn't work but that didn't seem to matter too much as I just charged it up. However, over the winter, though I brought the battery indoors, I did not charge it for a few months (combination of various reasons including memory issues) and didn't realise this would be a problem as I've heard conflicting advice about lithium ion batteries.

It still worked after I did charge it, but then after another gap in time, it stopped working entirely. I've charged it twice overnight and there is no response when I put it on the bike at all (the bike indicator lights don't light up at all). Unfortunately because the indicator has never worked on the battery itself, this is the only way I can tell whether it's working.

I suspect I killed it by not charging it regularly, which is a shame.

Question:
I'd like to buy a new battery, but getting an official one or getting this one repaired looks like it will cost way more than I paid for the bike itself, and I am on a very tight budget. I saw a couple of threads recommending off-brand ones on ebay, which looked affordable, but there was discussion about having to check the polarity of the battery. I would have no idea where to even start with that!

So my request for help is - what battery would you recommend to replace mine that is hopefully under £200 (pictures attached)? How on earth do I check the polarity of the battery and bike to make sure they are correct?

Please explain like I'm 5 there are a lot of things I'm fairly knowledgeable about and can understand, but for some reason batteries and the nuances of electricity have always really eluded me! A lot of replies I've read seemed almost in another language due to my lack of understanding.

Thank you so much in advance for your help, I appreciate you so much as my own google-fu has failed me

 

[saneagle]

That's called a silver fish battery. there are loads of suitable ones on Ebay and Amazon. The aluminium case is a standard size, but there are a couple of other standard sizes, and it's not clear from your photo which one you have. the length isn't important. It's the width (side to side) and thickness (front to back) sizes that matter. As long as the measurements in the listing are close, it should be OK.

I'm not sure, but I think the later Freegos had a narrorwer (fore and aft) battery than the earlier ones. Aliexpress is a good place to find them, but the searching is horrible.

You can choose the number of Ah you want. The more you get, the further you can go.

The battery should come with the separate base and the aluminium strip that it slots into. You can replace the ones on your bike with the new ones to guarantee that it'll fit, otherwise a different length one won't lock into the lock hole, or you can drill a new hole for the lock.

You need a meter to check the polarity. Set it to measure 200V D/C (see meter instructions). Then put the probes on the outside battery connection points. If it shows say 31.0v, your red probe is on the positive. If it shows -31.0v, your black probe is on the positive. You only need to make sure that they're the same way round on the new battery.

Tere's a typical meter. The black probe plugs into the "com" socket and the red into the right hand one. You can see the 200V in the 10 o.clock position.

Multifunctional Multimeter Tools High-precision Multimetro Tester (Black) UK | eBay

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36V15Ah Silver Fish Battery Electric Bike Battery E-bike Battery | eBay

If the battery has a switch, be sure to turn off the power switch.

www.ebay.co.uk

 

[Fluffybirb]

Hi there,

Thank you so much for taking the time to write such a helpful and detailed reply, I really appreciate it

I'm also very grateful for you explaining the 'whys' behind everything, it really helps me to learn and understand.

1. I measured the battery, and it looks to be 112mm front to back and 70mm side to side, wheras the one in the listing is 75mm side to side. Does that constitute a narrower one, or is 5mm probably close enough?

2. I also noticed that it says 36v/16Ah on mine, and the listing is 15Ah. I'm guessing 1Ah isn't going to make a huge difference, and I don't do long distances anyway.

3. Regarding the multimeter, would this work? https://www.amazon.co.uk/TESMEN-Multimeter-measurement-Auto-Ranging-Non-Contact/dp/B0BLZ7GN2X/ref=sr_1_1?keywords=multimeter&qid=1690642659&refinements=p_85:20930949031,p_36:118658031&rnid=118657031&rps=1&s=diy&sr=1-1&th=1 Or would that not be accurate enough for this scenario?

4. Finally, I took a look at the bottom to find the battery connection points (pic attached). I can see what looks like the two metal/coppery looking plates in there, would that be where I attach, or do I need to take the battery case off first?

Thank you again and apologies for all my questions! I like to try and understand as much as I can so that I can remember and apply it all in the future

 

[saneagle]

1. 5mm is OK. It's the front to back measurement that shows whether you have a different type. The problem is that some include the handle and some don't.
2. Correct. 10Ah would be OK too, but you wouldn't be able to go as far.
3. I guess it works OK. personally, I'd get a more conventional one, like I showed unless there is some specific function in the one you suggested that you need - principle of KISS.
4. The bottom of the battery is conventional. You probably wouldn't need to replace anything except for the aluminium rail (2 screws). The new battery should come with the blackplastic base piece and the base connector. Those parts are attached to your frame underneath the battery, where you'll see the two blades sticking up. You only need to replace those if there is a mismatch. If it turns out that the new battery has reverse polarity, you either have to remove the black plastic base from it and swap sides with the two blade things inside, or you swap the piece with the two blades in the frame.

 

[Fluffybirb]

Thank you so much! That's perfect. I'll go for that battery then (or equivalent) and look for a more conventional multimeter

I'm sure I'll be back to this thread many times to read over your answers and make sure I'm doing everything correctly. I really appreciate your effort and time to explain everything.

I'll update with how the installation goes - money's a bit tight right now so I'm not sure when, but I'm hoping end of the month/into next month I'll be able to purchase it

 

[Fluffybirb]

Hi @saneagle , I hope you are well!

I was able to borrow my dad's multimeter and we double checked my existing battery since the sensor on it doesn't work. After a whole night of charging, the red light on the charger didn't go out and it never went above 18.9v, so I think it's done.

I found this listing that is cheaper than the one above, and wanted to check if there's anything I'm missing in terms of risk vs getting the one over £200? Money is super tight so if I can save a bit by going for one that's £168 that would be great, as long there isn't a reason not to do that that I'm not aware of

Thank you again for all your help.

 

[saneagle]

Hi @saneagle , I hope you are well!

I was able to borrow my dad's multimeter and we double checked my existing battery since the sensor on it doesn't work. After a whole night of charging, the red light on the charger didn't go out and it never went above 18.9v, so I think it's done.

I found this listing that is cheaper than the one above, and wanted to check if there's anything I'm missing in terms of risk vs getting the one over £200? Money is super tight so if I can save a bit by going for one that's £168 that would be great, as long there isn't a reason not to do that that I'm not aware of

Thank you again for all your help.

It looks OK to me. When you get it or any other one, before connecting it to your bike, you must check that the + and - terminals are the same way round as your existing battery, otherwise the controller will pop and lots of pungent smoke will come out of it. It looks like it should fit your base, but if it doesn't, you can always swap over the bottom part of the battery - 4 screws and two wires.

 

[Fluffybirb]

Amazing, thank you so much for such a quick reply and I'll make sure to do that! I'll let you know how it goes

 

[saneagle]

Amazing, thank you so much for such a quick reply and I'll make sure to do that! I'll let you know how it goes

We always like to see a happy ending, so please report back and/or ask if you have any problems.