Battery and motor cut out

[architect]

Hi All,
I have just installed a 500w 36v front hub wheel to my bike, everything works fine until I go up hills and the motor cuts out. I have read previous posts and they say that my batteries may not be putting out enough voltage. I have 3x12v 7ah sla batteries and I think due to the low amps they are creating the cut outs.

I was wondering if it would be ok to add another 6v 7ah sta battery to the other 3 so that it increases the voltage to 42v. I thought that this may solve the problem of the lag, but it could over heat my controller?

I havent got much money at the moment and was wondering if there was a solution to the problem without upgrading to larger batteries?

Would it help to have thicker wiring from my batteries to the controller, and what type would you recommend?

Anyway everything else seems to work fine at the moment and I am still in testing stage.

If anyone has any suggestions it would be helpful

Cheers 

[Philip Lynott]

Thicker wires may help I can't say exactly what thickness to get,

As regards the batteries your 36V SLAs are actually giving out 41.4V when freshly charged (13.8V x 3)

A 6V SLA will give out 6.9V when freshly charged, so your really looking at 48.3V from your proposed pack.

I think my lifepo4 48V pack, which I use with a 48V BAC0281 controller, puts out around 61V when fully charged (I'll have to check this) so in my opinion the your controller should not be damaged - but I have not tried this and can't make any promises.

It think the pack itself should be safe and work fine, but you would have to charge the 6V battery seperately with a 6V charger.


Wheter or not your modification to your battery setup will fix your problem is a different question - it would surely help but you may find your bike still cuts out on step hills especially after riding the bike for a while and draining the batteries

[architect]

Thanks Phil,

i think I will try the thicker wires first then look at getting another 6v battery if that does not work. I don't mind a little cut out on steep hills, but as I run the batteries down the problem gets worse.

If I go with adding a 6v battery to my setup, will all batteries drain evenly or will power be lost to the 6v battery first? I just don't want to damage my batteries.... but am willing to gfive it a try.

Some of the old posts say that if u put 46v through a 36v controller then u will fry it.... but I have not read anyone trying this battery combanation.

Anyways thanks for the reply...


Cheers.

[ccbreder]

You need to get your battery output higher. more volts do that. But, higher amp hour batteries would be better. 
Put 3 more sla in parallel. If you can only afford one battery, I would try the forth 12 volt battery in parallel with one of your existing batteries.
it may not work, but then you could use it in series (48v). Pulling too much currant takes the voltage down, resulting in auto cut out.

[Philip Lynott]

Architect,

The batteries will be drained evenly because they all have the same aH, however the proposed set-up will only add 16% more energy and will prevent your controller from protecting your batteries as they become exhausted, which my cause problems.

In my opinion you need to just buy bigger or better batteries,

   I had 4 x 12aH SLA batteries and they were pretty good on hills but would sometimes cut out,

   I have 48V 20aH lifepo4 battery which is big and expensive but it never cuts out on my  daily commute which is almost 40 miles @ an average of 20mph

So I would recommend you cut to the chase and get something like a 36V 10aH pack - you will save money in the medium to long term.     

[architect]

Thanks for the advice Phil,

i will update my batteries mid next year, the problem is I have just purchased new 12 7ah bats so I will hold onto them util I get some cash.

I thought that I would add a switch to the 6v extra battery and only use it when I come to moderate hills. The rest of the time I will just ride with the 36v 7ah setup, I have little problems when I am on the flat. I think that if I add the switch it will help protect the batteries because I wont be drainig them all the time.

I do agree a 10ah setup would be good and I think it should climb modt moderate hills...... I don't have really steep hill where I live.

Cheers.

[zeusmorg]

 You would be better off increasing the aH capacity, rather than the voltage. If you increase the voltage of the pack, like has been stated, you would run the batteries down too low before cutout. and too high a voltage may also damage your controller (don't know how high you can go before that happens)

 to figure the wire sizes needed, there are many resources on the web.. look it up.

[architect]

Thanks guys for the imput,

i was wondering if the batteriese discharge too much does this show on the battery power indicator that comes with the kit?.... my power indicator has 3 leds that show full medium and low power. If I fix a switch to the added 6v battery so I only use it for steep hills, wouldnt that save the batteries from over discharge?

Does battery discharge show on the power indicator or is it something else?


Cheers

[biohazardman]

As stated in the above posts you need more AH so better batteries or more of the same batteries in parallel with what you have.  Another six volts is not going to do much.  Three more of the 7AH batts in parallel, with what you have, will get you down the road ten or twelve miles.  How they do on the hills depends on the maximum discharge ability of the batts, what the controller can handle and how much you are able to help.  Batteries are usually the most expensive part of the build.   

When I wanted better hill climbing performance, I went to 48v with the correct controller and decent batteries.  There is a world of difference between 36 and 48v when it comes to hills.  Good luck

http://goldenmotor.com/SMF/index.php?topic=279.0

[architect]

Hey Bio,

had a look at the link, u do have a nice bike there.... the kit is similar to mine but I have the front hub setup and standard controller.

I totally understand what u said about adding more bats for exstra AH, but unfortunatly I don't have the money at the moment to add 3 more. I did get a 6v sla and added it to the existing bats with a switch that can be turned on when I need the exstra power for hills.... I have tested the bike over 8km range and everything is ok, I have no problems on the flat roads and when I reach steep hills I need to use the exstra 6v to get up without any problems. I am still in testing but at the moment I think it is fine aslong as I don't use 42v max for the total ride.

I recharge the bats when I get back from riding just to prevent deep discharge, and I only need to ride a total of 6km max to and from work or shops.


i will keep posted on how this setup goes.


thanks for the input and please post any of your future projects...

Cheers