Verner 3V (Battery time)

[Brock]

Today I started marrying the engine and airframe.  Mounting - Check, Plugwires - check, Battery - Uh?

So, I'm looking to purchase a small LifePo (did I spell that correctly) battery.  I'm going with the Arm-Strong starter thus no need for 18Ahr mega current/capacity.  So how big/small a battery should I get?  I have no idea what the current draw on from the ignition units (x2) are.  I'm thinking enough battery capacity to get me safely down in case the alternator takes a vacation.  This also is important info when I decide on wire & switch sizes.

Any suggestions out there?

[rv7charlie]

No electronic injection or high pressure fuel pumps?
If the only electrical load is electronic ignition, most these days draw about an amp or two per ignition. BUT. Be very careful when sizing batteries. Most batteries will show an 'AH' (amp-hour) rating, but it's almost always at a '20 hour rate'. If you install a 2 AH battery and draw 2 amps continuously, it may only last 10-15 minutes. The '20 hour rate' means to divide the rating by 20, and that's the max continuous current you can draw to achieve that rating on the label.

And don't just take my word on that 2A figure. Either get the actual number from the mfgr, or *test*, under actual flying conditions.

[Chuck in Indiana]

Bullet has a *very* small LiPo battery that cranks the Verner like crazy. So much for memory.. I went out and looked. 120CCA.
Just my opinion, but it's not a terrible weight penalty to have a starter.

[Tom H]

Chuck mentioned weight penalty of having a starter.  I just happened to have the starter from my 3VW off and weighed it - 6.0 lbs.

[Brock]

Chuck mentioned weight penalty of having a starter.  I just happened to have the starter from my 3VW off and weighed it - 6.0 lbs.

Removing the starter ring makes it 'closer' to 9lbs.  Then consider less wire, less switches, smaller battery, etc.  Total weight savings is closer to 10lbs.  I'm really hoping my engine is easy to hand-prop. 

[Chuck in Indiana]

It is easy enough to hand prop..but..it involves a 3 cylinder engine and it's difficult to prop from behind. That means at the least chocks, etc.
I'm old.. lemme push the button.