Two Batterys

[DavieH]

Hi has anyone fitted two batterys together. My bikes own battery sits in behind the seat tube on the frame I was thinking of adding a bottle battery.
Would there be any problems on having them both connected at the same time.
Davie

 

[jerrysimon]

They would have to be connected in parallel if connected at the same time. IMO given all the problems that would result in terms of matching and balancing I see no benefit in doing it.

Best would be to unplug one when it ran out and plug in the other one, so making sure you had all the correct connectors and wiring to enable that would be required.

Regards

Jerry

 

[Cyclezee]

Hi Davie,

There is the option for a dual battery set up with eZee bikes.
The batteries are run in parallel, this gives the bike an extended range and when used together increases the longevity of the batteries.

See the example below


Here is a a link to the technique courtesy of Onbike http://www.onbike.co.uk/media/upload/docs/eZee-Parallel-Wiring-April-2010.pdf

 

[Deleted member 4366]

You could use an additional bottle battery or rack battery. The bike below has two batteries on top of each other. They were removed from their aluminium cases to save weight and then the two red power wires and the two blacks were joined together at one outlet connector. One of the charge connectors became redundent because the other one will charge both. As both batteries have their own Battery Management System, there's not too much chance of problems, but there's still theoretical risks. You can use totally different batteries as long as their voltage is approximately the same and you use the charger with the lower voltage on the label (they'll probably be the same.

Don't connect the batteries together until they are at exactly the same voltage, i.e both fully charged - not one charged and one flat.

 

[kitchenman]

Best would be to unplug one when it ran out and plug in the other one, so making sure you had all the correct connectors and wiring to enable that would be required ..

I use two batteries at the moment and use this method. I don't always need two batteries so this suits me very well. I use the same battery which has advantages but I can't seem to think of them at the moment! .. they do look good:

I'll have a cup of tea and add more when my brain is working at full voltage! ...

 

[Geebee]

IF the 2 batteries are the same capacity and exact type then it is fine and may also extend the life further than an individual pack (lower depth of discharge, lower C rate discharge) otherwise you will most likely shorten the life of one pack sometimes drastically, with some types mix and matching can cause possible fire risk.

 

[NRG]

ideally you should connect two different battery types together (in parallel) via some sort of protection cct IE it could be a simple diode. Don't rely on just the BMS if the chemistry is different. Trouble with a diode is it drops voltage and wastes power, the device also will need to be rated well above the expected power draw. An ex member tiberius cam up with an small cct called an 'ideal diode' but I'm not sure if he still makes them available.

Re-Voltage Home

 

[donkeydoo]

I have just connected my Ezee Torq with two battery's in parallel one li-po and the other li-po4. I used these diodes (thought I better be on the safe side) Blocking Diode 30A Schottky Wind Generator Solar Panel | eBay

Everything is working fine and I am now thinking of adding a bottle battery to give me 30AH but then again do I go that range?

 

[NRG]

I have just connected my Ezee Torq with two battery's in parallel one li-po and the other li-po4. I used these diodes (thought I better be on the safe side) Blocking Diode 30A Schottky Wind Generator Solar Panel | eBay

Everything is working fine and I am now thinking of adding a bottle battery to give me 30AH but then again do I go that range?

Good find, they would only dissipate about 3w each under full load and the price is right!

 

[Cyclezee]

As far as eZee batteries are concerned, I do not know about other brands, Schottky diodes are not required when running 2 batteries in parallel.

The eZee Forza shown in my previous post in this thread has a 14Ah LiPo and a 8.5Ah LiFePO4 and has been running with this configuration for more than 2 years without any problems.

I have not heard of anyone else who is running eZee dual battery setups experiencing problems.

 

[Scottyf]

The two chemistries have slightly different discharge voltages.

Ideally if your doing this yourself without any form of protection for each battery unit it should be the same chemistry and voltage.

The amp hr capacity does not matter.

Also, They need to be charged and dischargeed at the same rate. Do not connect an empty battery to a fully charged battery.

As the fully charged battery will dump its charge into the empty battery trying to bring it up to the same voltage and equalising it.

People have done that with LIPO as it dumps 30c or 150amps into the other battery. The wires get super hot and it is no good for the cells.


You can mix and match amp hour capacity all you like so long as its the same voltage there is no worries.


All this changes if you run them in series though.



Its better to run both batteries in parallel all the time if you can. It gives better range, a faster speed for longer and lowers the dischage rate as you've effectivly got a much larger battery thats not being stressed.



Bigger as they say. Is better.

 

[jhruk]

It is certainly preferable to run two batteries in parallel, rather than switching between them, but I think the necessity for diodes may depend on the design of the BMS.
The OnBike instructions, and the experience of Cyclezee, suggest that the Ezee BMS has diode protection on the output, and their batteries don’t need additional protection. However the instructions from Ping suggest that their BMS doesn’t, and recommends the use of diodes with their batteries - unless you’re very careful.

If you’re not sure about your BMS protection, on both batteries, and plan to run that configuration regularly, I would think fitting the diodes a good idea. A mistake could be very costly.

 

[flecc]

The Panasonic unit batteries also have protected BMS, so can be run in parallel with another battery at low risk. I can't say if that's true of the Kalkhoff-BMZ batteries for those units though.

 

[donkeydoo]

As far as eZee batteries are concerned, I do not know about other brands, Schottky diodes are not required when running 2 batteries in parallel.

The eZee Forza shown in my previous post in this thread has a 14Ah LiPo and a 8.5Ah LiFePO4 and has been running with this configuration for more than 2 years without any problems.

I have not heard of anyone else who is running eZee dual battery setups experiencing problems.

I have two different batteries one from Ezee (original getting old li-poly) and the second from BMSbattery (new from china li-po4) so I thought by adding the diode it would stop cross charging no matter what state of charge the battery is in. Might be overkill but with the expense of batteries as they are and for the sake of diodes £2.99 each I don't want to ruin the batteries.

 

[JamesC]

This old thread predates the arrival of the eZee kit for adding a second battery, but describes the process in some detail. It may be useful.

Torq Double Battery Arrangement

James

 

[donkeydoo]

I know my Blocking Diode 30A Schottky Wind Generator Solar Panel | eBay

were a bit of a b*gger to solder and they look like leftovers from sputnik but hey I gave it a go. If its working or not? Well I can say it's working for now. Sometimes I charge one battery and not the other due to work and not enough chargers (if I can get away with it depends if management are down). Trouble is how can you prove its working or not? if I take the diode away and it FUBAR my batteries. You probably would have to be a company to test this and have the resources to fail or not.

I think play safe unless someone knows better

Thanks for the excellent threads on this site otherwise i wouldn't even be be talking about this. It is because of you I have attempted to do what I have done. Well done every one. I have ony had a Ebike for 6 months due to my knee failing due to a motorbike accident in the past. I did have a "normal" push bike but in the end couldn't get up the hills but the ebike has let me cycle again and a new lease of accidents (LOL). Thanks everyone. Great website.

 

[flecc]

With two different battery chemistries and not being able to charge both at times, definitely play safe and leave those diodes in circuit. Having one battery charged and the other low without diode protection is asking for trouble.