Just bought and installed a group 51R battery on my '07 USDM Fit. I was worried about my Fit's battery (3 years/60K miles old) dying on a road trip and I have heard of shortages and delays getting a 151R from Honda. The 51R was a drop in replacement (Batteries Plus' catalog has even updated to show it as a replacement). You have to remove the original battery tray, but it's no problem, If you are anal about those kind of things, you can cut out one end to fit the larger battery. So come battery time I recommend an easy to get 51R over the hard to get, weak, and expensive 151R from you friendly Honda dealer.

 

I am thinking of buying a 2010 fit and am concerned about the small and hard to replace battery. How did you get the 51R into the small space? I've measured and the 51R is 2 inches longer and there isn't 2 inches of space left to right between the air filter housing and the headlight housing.

 

I have 100k miles on my original '07 battery. There is nothing wrong with them.

 

Can't answer for a '10. Mine is an '07. It was tight, but fits with no interference. I had to remove the plastic battery tray though.

 

You'll be fine. By the time you have to worry about a battery I am more than positive there will be a plethora of replacement batteries in stock.