3 lights off 36v Battery

[awol]

Thanks to a recent thread on this subject I ordered/received my parts to wire my lights directly to my bike battery as I need to charge the small lights battery pack every day and would like to know if it will run ok without draining my battery too quick.
How can I work out how much power (amps?) it's all using?
I have a 36v-9vdc-dc reducer, 3A inline waterproof blade fuse(with heavy wire),3xcree front(floodlight),1xcree front(spot light)and a rear magicshine MJ-818 ,thanks 103Alex1, pretty much the same gear you mentioned in that thread. I find I need both front lights on full along the pitch black lanes then switch the 1xcree off when in town.
Will I be able to connect all this to the 36v light switch output wire direct from my controller or should I take it direct off the battery?

 

[tillson]

I am supplying more or less the same set up as you. I wired my DC-DC converter off the back of the battery connector on the bike with an in-line fuse. The DC-DC converter is rated at 3 Amps and it seems to run cool and has worked well for 12 months.

 

[Deleted member 4366]

Alex can probably remember what we calculated bbetter than me, but IIRC we figured out that yout 3 LED light is technically over the three amp limit of the DC/DC converter; however, somebody else said that he used one without problems. Whatever, 4 LEDs or more is asking for trouble. You need at least a 5 amp DC/DC converter. You must bear in mind that if it does fail, it'll dump the full 36v into your lights, so you'll end up with nothing. You could use two of them.

It would e better to connect them to the battery via a separate switch because the 36v wire running up to the controller and the one back to the light socket are very thin. I'd say 1 amp max for that setup.

With all lights on, you'll be taking 4.5 amps from the 9v, which is about 1.5 amps from your battery, so your range will be reduced by a fair amount.

 

[awol]

Believe it or not I happen to have just received a variable 36v-3v LM2569HV d8veh mentioned a while back which I ordered from china and forgot about until it arrived the other day and thought I wouldn't need it now. So I do have 2 and could set that one down to 9v. With 2 of those dc-dc reducers I could have the single cree front and magicshine rear on one dc-dc and the 3xcree front on the other separate.
So I will take it straight from the battery as tillson is.
Any tips of electrically wiring from the battery to 2xdc-dc reducers as my electrical knowledge is pretty slim and could someone point me in the right direction for suitable switches too as I'd not considered switches.
I will also need to make small housings for the dc-dc reducers too or is there any cheapie readymade ones?
For my range I could trial it a couple of days and see how it goes with various lights on.

 

[Deleted member 4366]

Can you just remind us what battery you have and how you disconnect it from the controller.

 

[Geebee]

I do love the convenience of running my lights off the main battery, but this may be another option SingFire SF-B12 13200mAh 8.4V 12 x 18650 Li-ion Battery Pack for 1200~5000lm CREE LED Bike Headlamp - Free Shipping - DealExtreme

 

[awol]

My battery is the 36v 10ah bottle style and lasts aprox 24miles the way I am using it and my commute is 20miles (20% max spare amps, is that how it works?)
That larger cree battery Geebee points out would be a good option for once a week charge but adds more weight for me, I have a mate who may benefit from that though.

 

[Deleted member 4366]

Bottle batteries have a switch to switch off the BMS, so you don't need a separate isolator switch for them, but if you decide to mount them in a box, it would be nothing much extra to add one or two 5 amp switches. It's probably a good idea to include some 5 amp fuses on the output too.

 

[awol]

So my +ve wire will go from battery +ve to 5a fuse to switch to dc-dc and my -ve will go from battery straight to dc-dc?
Should I be using 14g wire for it all with coming straight off the battery or can I use thinner?
Could you point me in the right direction for a suitable switch, my searching seems to find mains electric switches and will probably end up with the wrong one.

 

[Deleted member 4366]

Yes, that's all right except that you don't need 14g wire, which can handle 30 amps. The 36v wires will only have just over 1 amp in them so you can use any wire that's convenient for them, and 5 amp wire to your light connectors. I'd probably strip the wire out of a bit of 5 amp mains lead, like a table lamp lead or something.

 

[awol]

Apart from my difficulties wiring up 2x dc-dc light sets and the problem with limiting my battery range I have realized I need to keep 1 front light on it's own small battery as a backup anyway just in case, so am going for 1xcree front and magicshine mj-818 rear on the 9v dc-dc.
I don't need a switch just yet as d8veh pointed out I have the main switch on the battery for now but I'm struggling to find a suitable switch to wire in as there are lots of different types, could anyone point me to a suitable one/type.

 

[Alan Quay]

... I'm struggling to find a suitable switch to wire in as there are lots of different types, could anyone point me to a suitable one/type.

Pretty much any switch capable of handling 1A will work.

One of these will do the job, as long as you keep it in the 36v circuit, where the current will be lower.

http://item.mobileweb.ebay.co.uk/viewitem?sbk=1&nav=SEARCH&itemId=180684360322

 

[Deleted member 4366]

I was thinking that you could mount the converters in that aluminium box with your controller.Two switches and panel sockets to plug your lights in,In Maplin, you can get a standard toggle switch ans a rubber boot thing that males it waterproof.
Sub-Miniature Toggle Switch C | Maplin
Sub-Miniature Toggle Switch Cover | Maplin

 

[103Alex1]

In terms of the current these lights draw, this post might be helpful ....

http://www.pedelecs.co.uk/forum/electric-bicycles/12614-brightest-possible-front-light-6.html#post175868

As you can see, on 'high', the 3-CREE coupled with an MJ-818 draws 2.5A after a 36V-9V DC-DC converter and 0.6A before it.

If you are running a single CREE in addition it will draw about 1A after converter so as d8veh says, best to run a higher capacity step-down converter or else route your 3-CREE or 1-CREE through a separate 3A one like you are planning. It'll all likely draw about 3.5A after converter(s) with all lights on highest power. To be honest chance of making use of this much illumination is slim but since you can't easily by-pass having to toggle through the settings having some lea-way makes sense.

You can save a fraction of amps draw by rigging your converters to 12V instead of 9V but this will likely come at the expense of some minor loss of potency of illumination.

I only run one 3-CREE front + a rear off a 3A converter. The other 2 front lights on the bike are 36V (no step-down) and 22V (stepped down independently). Switch before the lights (and DC-DC converters) because there is latent power draw off both, or fit an isolator switch across the entire tapped circuit if running multiple accessories off it. My tapped circuit includes a 12V supply as well as the lights and the whole lot is switched with one of these, which is very capable :

http://www.amazon.co.uk/250VAC-DOUBLE-SWITCH-LOCKING-WATERPROOF/dp/B008OI2WT2

All the lights are separately controlled using a handlebar switch after the isolator switch, but unless you are running on/off single setting lights which don't need to be physically turned on via the back of the light or bezel (as my non-CREE lights are) this won't add anything and a single master isolator should be plenty.

You can fit separate fuses before or after each converter if you want to. Just depends how much you want to spend !

 

[awol]

Thanks for the great replies.
I've gone from potentially overloading the dc-dc and blowing all my lights and having no backup light either to now having an idea of how to wire a safer setup and also what switch will do and where to put everything.
Can I ask 103Alex1 what is your 36v light and does it simply switch on/off with no modes to cycle through? (an idea to run it off my controller)
A quick electronic question - when the term is used "draws 1A" (1A for example), is that the same as saying 1Ah therefore leave that item running for 1 hour and my will battery loose 1Ah of its 10Ah capacity ?

 

[tillson]

Thanks for the great replies.
I've gone from potentially overloading the dc-dc and blowing all my lights and having no backup light either to now having an idea of how to wire a safer setup and also what switch will do and where to put everything.
Can I ask 103Alex1 what is your 36v light and does it simply switch on/off with no modes to cycle through? (an idea to run it off my controller)
A quick electronic question - when the term is used "draws 1A" (1A for example), is that the same as saying 1Ah therefore leave that item running for 1 hour and my will battery loose 1Ah of its 10Ah capacity ?

Yes, Amp hour (Ah) is current x time. 1 Amp drain for 1 hour is 1 Amp hour, 2 Amps for 1 hour is 2 Amp hours, 5 Amps for 30 minutes 2.5 Amp hours. You are probably getting the idea now.

Things aren't quite as straightforward though, particularly with high rates of discharge. Foe example, a 10 Amp hour battery would be unlikely to be able to supply 20 Amps for 30 minutes, but with low demands like those above, a simple Current time multiplication is close enough.

 

[103Alex1]

Can I ask 103Alex1 what is your 36v light and does it simply switch on/off with no modes to cycle through? (an idea to run it off my controller)

It's this one : 12V 5W LED CREE Home Garden Waterproof Day Work Spot Decoration Light Outdoor | eBay

Scimitar and some others I think had trouble getting the right colour sent. Mine came in white which was as I requested. The current test on it came out at 0.23A off 36V battery.

It does indeed simply switch on/off with no modes to cycle through. I power it off a tapped supply switched by the high (secondary supplementary) beam setting through one of these Hi/Lo handlebar switches :

Trail Tech || Three Position Switch

The above switch is good for 10A & there's a kill button on top of the switch that I rigged a very ‘amp-hungry’ horn up to so was pretty useful for me, but you can get lots of simpler cheaper handlebar switches. The CREE and rear are rigged to low beam, are turned on manually and stay on. Then I turn the 36V light (and the main 27W headlight if fitted/connected) on and off as additional lighting in-ride using the high beam switch setting.