Current Draw on 26/27 Headlights

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Model T Ford Forum: Forum 2015: Current Draw on 26/27 Headlights
Top of pagePrevious messageNext messageBottom of page Link to this message  By Alan George Long on Saturday, July 25, 2015 - 04:25 am:

Wondering what the common knowledge is in terms of the expected current draw from a set of headlights on a 26/27 T. Assuming that all electrics and earth are in good condition. ie what would be considered excessive? Have you found issues within the headlight switch also.
Thanks. Alan


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Jablonski on Saturday, July 25, 2015 - 05:26 am:

Alan:

Depends...........
What wattage bulbs are you using ?
Standard 32/32 watt.... or the 50/32 watt bulbs ?
One or Two tail/stop light fixtures ?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Saturday, July 25, 2015 - 05:39 am:

Sure depends on what bulbs you have.. My very inexact 26/27 ammeter shows about 10A draw when I switch on the headlamps. To get the single taillight to lighten up I have to turn the switch just a little more - then the needle goes ~ another ampeere towards the discharge side.

I've adjusted the generator to charge to about one amp to the plus side with the lamps on, then I drive with lights on all the time for safety - plus it's the law here, so the modern drivers expect others to have lights to be seen.. Since I haven't got any electric starter, that's all the charge the battery needs. Let's see how the generator holds up in the long term :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kevin Whelihan Danbury, WI on Saturday, July 25, 2015 - 07:32 am:

I have 6 volt/25 watt halogen headlight bulbs and LED tails/brakes. I replaced my ammeter with a period Stewart unit that is pretty accurate. When turned on, they draw 8 amps on high or low beam (makes no difference with those). When I replaced the halogens with stock bulbs and they still draw 8 amps. Can't remember the exact bulb number of the stock bulbs though.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Walker, NW AR on Saturday, July 25, 2015 - 09:09 am:

p=ie, where p=power (in watts), i=current (in amps), & e=voltage.

Solving for current, the formula is i=p/e, or 32/6 if using 32-w bulbs @ 6-v. 32/6=5.33 amps draw per bulb x 2 headlights = 10.67 amps for both.

If using a different bulb or a 12-v system, just substitute those numbers into the equation to get the answer.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Saturday, July 25, 2015 - 01:26 pm:

Just to correct something here. CP=CANDLE POWER and is a measure of the bulb briteness and while higher briteness bulbs also are typically higher wattage too the 32CP bulbs that are commonly sold for a T are not also necessarily 32 Watt bulbs. 1 CP does NOT equal 1 WATT so you must not use CP and WATT as interchangeable in definition although that seems to be a common wrong assumption. Bulb briteness is now more commonly expressed in Lumens when comparing bulbs.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Larry Smith on Saturday, July 25, 2015 - 02:02 pm:

The original bulbs were 21-2 cp.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Walker, NW AR on Saturday, July 25, 2015 - 06:00 pm:

Thanks for that correction, John. I thought the bulbs were rated in watts, not CP. (It's all Jablonski's fault.) :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Jablonski on Saturday, July 25, 2015 - 06:18 pm:

Sorry Mike for the mis-info..... way before I had the first cup of coffee. Meant to type Candle Power.

But,,, I did make someone think !


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