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Need a small portable power source for diesel glow plugs

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filonic

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Hello,
I am working on a project that requires powering a diesel engine glow plug from a relatively portable power source. The diesel glow plugs come in a variety of voltages, most common are 6v, 12v, and 24v. From what I understand, the most commonly found ones are 12v and draw around 10 amps. I have tried a number of configurations with varying success and at this point I am pretty frustrated with the trial and error method and so I am here to ask for help. I have been successful using a small 12v lawnmower battery(capacity unknown) with the 12v glow plugs, but it is WAY too big and heavy for my intended use. When I tried hooking up the same 12v glow plug to a series of 8 x D cell batteries, I was able to achieve a glow, but it seemed to be nowhere near its full heat potential. I am going right now to buy a 6v glow plug in the hopes that by using the lower voltage, I will be able to supply enough current with the 8 x D batteries. The power sources I have already purchased that may work include:

1. 1 X 12v Lead Acid Lawnmower battery (way too large) https://www.oreillyauto.com/site/c/....oap?ck=Search_N0057_-1_-1&pt=N0057&ppt=C0218

2. 8 X D cell alkaline batteries and various holders for different configurations

3. 1 X 6v 4500mah Lead Acid Alarm System Battery

4. 1 X 7.2V 2000mah NiCad Battery

Obviously I am lost and have no idea what I am doing, so any kind of help would be much appreciated. The priorities are as follows:

1. HOT - it must reach full heating potential which is a glowing orange almost white hot.

2. Speed - it must reach that temperature in a relatively short time window, less than 20 seconds, by design these plugs are supposed to be fully hot at 5-10 seconds.

3. Size - I really need this to be portable, if it takes a car battery to do it, then its not going to work. I would like to keep the power source smaller in volume than a 12oz can of soda. If it could fit in a large pocket, that would be even better.

4. Capacity - It will need to be able to bring the glow plugs to full heat and maintain that heat for approx 10-15 seconds at a time. I am hoping to be able to complete at least 30-50 of these heating cycles before the power source is depleted.

5. Rechargeability - Preferably, it will use a power source that is rechargeable, however if the cost is too much or it will substantially increase the bulk to use a rechargeable power source, using disposable alkalines or nimh is a possibility, theoretically even a disposable 6v lantern battery could work.

I really appreciate any and all input that you guys can give me!

Thanks Alot,
-Alex
 
Its all about the $.

Lets do some envelope math:

10 seconds to heat 15 seconds on. Lets call it 30 seconds.

50 cycles X 30 seconds = 25 minutes. Lets call it 1/2 hour.

1/2 hour X 10 amps = 5 amp hours. This is the battery capacity needed.

Cheapest lead acid, but probably to big,

NICad or Nmhd. Nicad is better when it's cold.

Lipo: Best size and weight but expensive.

The alkalines have a pretty big voltage drop at the high current. Thats probably why you wern't happy with them.
 
Try ten sub-C NiCads. In series, that's about 12V under load, and they are rated for very high current (it's what powers cordless drills). NiCads have a much lower internal resistance than the others on the list. Part of the problem with getting a high power transfer is that the internal resistance of the battery divides down the power delivered to the load. A sub-C like a N-1250SCRL (available from Digikey and others) is only ablout .9" diameter and 1.35" tall, so 10 of them should fit the volume you require.

Look at the second "high rate" discharge curve on the spec sheet here, near the bottom right - https://www.electro-tech-online.com/custompdfs/2012/04/N-1250SCRL-1.pdf
It lists an "8It" rate (15.2A) and a "4It" rate (7.6A). You are at about a "5 It" rate, so the voltage will hold pretty flat at 12V out for a good 10 minutes or so.

What the heck are you building? A giant model airplane engine or something?
 
Last edited:
7 Ah SLA battery

The easiest would be to get a 12 Volt 7 Ah SLA battery.
They are reasonably compact and not too heavy.
Calculations are already done so you have enough Ah capacity.
 
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