Battery Ignoramus Question

[Captain_Mike]

Let me start by saying that I have no knowledge of electrics whatsoever!!

I recently purchased a secondhand "Elysium Relay" ebike, fitted with a Cyclotricity 250/500 rear wheel motor.

The bike has been modified by a previous owner and is now fitted with a Bosch Powerpack 300/400 battery, that has 30/40 cells, 36 volts, and a capacity of 8.4/11.6amp hrs.

If I wish to fit a larger battery, is there any maximum electrical limit in terms of volts or amp hrs that I need to consider.

I would be grateful for any advice.

 

[sjpt]

You will need to keep to 36 volts (or change the controller and maybe other bits). Your current battery must either be the Powerpack 300 or the 400. Unusual to use a Bosch battery with a non-Bosch system. You shouldn't have any issues with a larger capacity battery because of the capacity. You may have issues with physical connections, and arrangement of battery/controller; I suspect the original owner already did some juggling to fit the Bosch battery. I think you will need to wait for more from the experts ... they'all almost certainly need more details before they can give much more advice.

 

[Captain_Mike]

Thank you. There certainly has been some "juggling". The bike is also fitted with a thumb throttle. When charging the battery, I have to disconnect the motor negative lead and connect a separate negative lead that comes from the battery, together with the standard positive lead that connects the battery to the motor.

There is also a "black box" attached to the frame, from which a multitude of cables protrude

 

[vfr400]

Are you sure it's a Bosch battery? I'm pretty sure that you can't get any power out of a Bosch one unless it's connected to a Bosch motor.

If you want to replace the battery, you need either a lot of amp-hours, one with high discharge rate cells or one with both.

 

[Danidl]

Thank you. There certainly has been some "juggling". The bike is also fitted with a thumb throttle. When charging the battery, I have to disconnect the motor negative lead and connect a separate negative lead that comes from the battery, together with the standard positive lead that connects the battery to the motor.

There is also a "black box" attached to the frame, from which a multitude of cables protrude

Please attach a few photos ..it will help us identify options

 

[Captain_Mike]

Thank you Danidl
I hope that the following give an idea of the setup. The first shows the battery, the second shows the wiring coming out from the battery, and the third shows the wiring from the black box. If you require more detail as to where the various wires then go, I can take a more detailed look tomorrow.

 

[soundwave]

that is a gen 2 bosch battery case and no way would it work unless it has been gutted and a diy batt put inside of it.

 

[Nealh]

I agree somewhat with SW, with the wiring as it is looks like someone has either recelled or replaced the bms and instead of having a charge port has done something strange with the wiring.
It is possible he has used a two port bms which uses the discharge for charging, possible he has added the thin charge ground so he only disconnected the red to prevent a cross polarity mix up with the main supply and the Andersons would be easy to connect wrongly.
What I don't understand is why didn't he also add another v+ thin wire for charging to save messing about add a proper charge port, to know for sure the only way is by by opening the case to see.

OP the black box with wiring you talk of is the controller (bikes brains) without this the bike wouldn't work.

 

[Nealh]

If the op wants another battery then he can use any 36v battery with as many ah/wh as he wishes, to maximise capacity you need a battery with 3500mah cells inside so GA, 35E, MJ1 pr M36 cells or opt for the 21700's with more capacity.
4 cells = approx. 14ah, 50 = 17.5ah & 60 =21ah, More mah/capacity means a larger heavier battery for the last two options.
Without knowing the controller details then 36v is the only safe option.

 

[Captain_Mike]

Thank you everyone. I think my first step is to open the “Bosch!!?” battery case and see what is inside. Another issue is that when charging, the charger immediately displays a green light, which I didn’t expect to see until the battery was fully charged.

 

[vfr400]

My worry is that somebody has simply bypassed the BMS discharge controls, so those wires go straight to the cell-pack.

 

[Nealh]

My worry is that somebody has simply bypassed the BMS discharge controls, so those wires go straight to the cell-pack.

It is a possibility and only a fool would do it and the sell on the battery /bike as it is.
If the seller has done so then it is damn dangerous to do so especially for the buyer if unaware. As we know it is ok to do so without a BMS, but in place there needs to be a system/way of checking cell groups for individual voltage's.

 

[Nealh]

Thank you everyone. I think my first step is to open the “Bosch!!?” battery case and see what is inside. Another issue is that when charging, the charger immediately displays a green light, which I didn’t expect to see until the battery was fully charged.

Opening is a very good idea to find out/know what has occurred, post pics to aid us and you in to identifying what has been done.

If the charger shows a green light then indications are that a cell group is already at full voltage and if a BMS was fitted will not allow further input.

What is the current SOC (state of charge ) ?

 

[Nealh]

Cpt Mike you will need to get your self a mutli meter to carry out any diagnosis/voltage checking, get one from ebay or any other electrical store for 5- 10 £££'s and one that has the continuity beep function.

 

[Nealh]

Cpt Mike another issue if a BMS has been bypassed (we hope not) is that it will also be unfused, if any current isn't fused then chance of controller damage or wire damage is of concern and possibly worse could occur. For now I wouldn't want to be keeping the battery indoors or in a flammable environment.

Do post pics of the opened case and wiring /bms for us to see.

 

[Captain_Mike]

Once again. Thank you for all the advice. I've now been placed on domestic duties, so it will not be until this afternoon that I'm able to post more details.

 

[Nealh]

If no bms is fitted then charger won't input more charge once terminal voltage has been reached, this could mean over charged cells which is dangerous and poses a risk to you. As mentioned keep battery outdoors until you know what has occurred.

 

[vfr400]

Another not so obvious way to get power out of the battery is to bridge the output MOSFETs, which will keep them switched on, but it's the same as bypassing the BMS.

 

[Captain_Mike]

Finally released from domestic duties and managed to open the battery case, and source an avo. The avo gives a voltage reading of 36V.

Attached is a photo of the interior of the battery. I have no idea of the relevance or otherwise of the following, but I can see that between the 5th and 6th batteries down on the right, the thin grey wire appears to have been cut. And then at around the mid-point, two thin grey wires look to have been joined together.

I suspect that I'm nearing the point where I will have to visit a local ebike servicing centre!!

 

[Captain_Mike]

P.S. Finally managed to remove the whole battery array from the case and add the following photos