# interlock battery

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#### Nordic

##### New Member
Hello!!

First time poster, long time rocketer...I just got into mid/high powered rockets and recently acquired the Aerotech Interlock controller. It says it can be powered by a car battery, but it's not always convenient for me to drive my car out to the launch site and use it. Are there any alternatives to using a 12v car battery? maybe something lighter and more portable?

TIA,

#### Handeman

##### Well-Known Member
TRF Supporter

I like a motorcycle/garden tractor/atv battery. The cheaper the better, they're smaller. 2.5" x 5" x 5" A rating of 70 Cold Crank Amps and fully charged will launch your MPR, even HPRs all day. You will need a car battery charger if you don't have one.

#### El Cheapo

##### Well-Known Member
I have everything from wet cel car batteries, a 12v hobbico or whatever it's called to an Odyssey 680 AGM race car battery. I use a 12v Peg Perego battery I acquired from my kids electric John Deer Gator when the gears wore out on it. Works like a champ. It's light, has a handle and is still at 95% charge after a full day of launching.

Hit Craigslist and see if you can find a cheap ride along toy, keep the battery and ditch the toy. Otherwise they're pretty spendy to buy.

Or, you can cut the leads, replace them w/a 12v Accessory plug and use the 12v jump box you have behind the seat of your truck.

#### Nordic

##### New Member
Thanks for the responses!! I've been looking around for a small "motorcycle-esk" battery..i found a dinky little 12v hobby battery at radioshack. But it doesn't even turn the warning buzzer on when the key is insterted. I think something a little more substance would do.

#### bobkrech

##### Well-Known Member
The most convenient 12 volt batteries for launchers are small VRLA (valve regulated lead-acid) gell cell batteries. They operate in any position, and are commonly found in computer UPS and emergency lighting applications. They have higher pulsed current capability (which is what you want for a launcher) for their weight than car or motorcycle batteries.

The link below lists a number of 12 V gell cell batteries. You typically use up 0.005 to 0.01 AH capacity per high power igniter, or to be conservative 100 launches per AH capacity. Our club launchers use 7 AH capacity batteries which are good for several hundred launches. For personal use a 2 AH battery is fine, but there is little difference in price for a 5 AH or 7 AH battery. Just remember that the batteries weight about 1 pound per AH so the higher the capacity, the heavier the battery.

Ref: https://en.wikipedia.org/wiki/VRLA

Bob

#### falingtrea

##### Well-Known Member
If you want something that is multi purpose, look at the automotive portable jumpstart or self powered air compressor units. What is nice about these units is that they typically include a charger. Some of these units also have a 12VDC aux power connector that you could use for other devices beside the launcher.

https://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=38391

https://shop.oreillyauto.com/ProductDetail.aspx?MfrCode=MTD&MfrPartNumber=11406&CategoryCode=3014

https://www.homedepot.com/webapp/wc...Id=10053&productId=100348465&N=10000003+90401

https://www.walmart.com/catalog/product.do?product_id=3992

#### hardinlw

##### Well-Known Member
I'm using one of the jump start devices and bought an adapter from Radio Shack that plugs into the accessory outlet. I put banana plugs on the battery leads from the controller and now I have the option of plugging the adapter into my car accessory outlet if the jump start battery goes dead.

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#### El Cheapo

##### Well-Known Member
That's exactly like the Hobbico I have however I've never used it for launching rockets. It came from a private party puchase when I bought my Initiator Launch set. I do plan on rewiring an estes charger and using this strictly for LPR and LPR clusters up to three motors.

https://www.hobbico.com/fieldequip/hcap0800.html

Here is what I'm using for my medium power stuff at the moment

If I can't find some broke racer to buy this from me for the very reasonable price of $70, I'll use this for my new MPR/HPR Launcher. I would never buy this kind of battery for a launch controller. It's too expensive at$120 new. It's a spare that we kept in the trailer for our two race cars.

https://www.odysseybatteries.com/battery/pc680.htm

If I had to actually go out and purchase something, I'd purchase a jump box. Oh, btw, I already have one of those too.

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#### MarkII

##### Well-Known Member
I'll second falingtrea's suggestion for using a portable car starter battery. I use a no-frills basic car starter (no air compressor or spotlight, but it does have a built-in charger) that I picked up on clearance at a local Radio Shack a couple of years ago. I use it with my Interlock Controller to power all of my ignition tasks, which never come anywhere close to taxing its power reserves. Like all lead-acid batteries, it loves to be kept well-charged; frequent chargings help to keep it healthy. I just clamp the battery clips from the controller and the battery together. Considering that it contains the charger, the battery is not all that heavy at around 7.5-8 lbs., and it has a built-in handle which makes it easy to tote out to the pad.

MarkII

#### Nordic

##### New Member
I'll second falingtrea's suggestion for using a portable car starter battery. I use a no-frills basic car starter (no air compressor or spotlight, but it does have a built-in charger) that I picked up on clearance at a local Radio Shack a couple of years ago. I use it with my Interlock Controller to power all of my ignition tasks, which never come anywhere close to taxing its power reserves. Like all lead-acid batteries, it loves to be kept well-charged; frequent chargings help to keep it healthy. I just clamp the battery clips from the controller and the battery together. Considering that it contains the charger, the battery is not all that heavy at around 7.5-8 lbs., and it has a built-in handle which makes it easy to tote out to the pad.

MarkII
Thanks for all the input!!