7Ah SLA Battery for 100W HID

[Helios]

Hey this isn't lasers but its batteries and still really cool!

I am building two 100w HID spotlights using the THOR Colossus as a base.

I am building these for some friends. They are not up to date on li ion charging procedures so the last thing I want is to make them a battery pack.

My question is will the stock 7Ah SLA battery be up to the task? The stock bulb is 130W so it would seem it should be no problem...however I know that the HIDs generally require a spike of current to start. Once started I have read that in reality it will draw less than 7 amps as they are exaggerated and more 80-85W kits.

I think I'm good but want to make sure before I drop $220 on the parts.

Thanks!

 

[djQUAN]

I don't have 100W kits but on 35W ballasts, Peak current draw at warm up is about 6.5A and drops down to about 3.5A at full brightness and at operating temp.

 

[Helios]

Yeah I'm guessing a 10-12amp start up... I think I read it somewhere but can't find it

 

[Things]

They will be fine with the startup. If they draw 7A while running, it means you should *in theory* get an hour out of 7Ah SLA. However SLA's capacity drops pretty rapidly so I'd expect maybe 45 mins or so at best from a fresh battery.

 

[Helios]

Thanks! I thought so I just wanted to air my thoughts here before I have two torn up spotlights and two hacked up HID kits that won't turn on.

 

[BShanahan14rulz]

You can always buy new cells when the old ones die, they aren't terribly expensive.

Halogen has a high startup current too.

 

[Helios]

The lights are here!

But I thought up a new potential problem...this battery will be 12ish volts after a fresh charge. After its on for awhile the battery will drop voltage. In a halogen it would just lead to a dimmer light but a ballast driven HID will abruptly shut off if the input voltage gets too low. So couldn't this make my run times like less than 10 minutes?! I could get a boosting voltage regulator but I didnt budget for that. :cryyy:

 

[Cyparagon]

They'll usually work down to 8V or so. Your SLA is long dead anyway by the time it gets that low.

You'll still only get 10-20 minutes, but that's because your battery capacity is so low. The 7AH rating is typically at a 1A draw, and you're pulling a bit more than 1A.

 

[Helios]

Gotchya. Well I will try it and if it sucks I do have 20 LiFePO4 18650 cells laying around I could play with. Need to charge the pack somehow though without breaking the bank.

Thanks

 

[djQUAN]

HID ballasts are a constant power load so they will draw more current when the battery voltage drops which will be very hard for SLA batteries.

 

[Helios]

I just tested it and it does indeed fire up! I only ran it for maybe 45 seconds so I don't know run times but I'm pleased it starts up just fine.

Thanks all