Battery question

[Stoo]

I wasn't sure if I should put this in the engine forum, but i figure it's more an electrical question... and probably a stupid one at that..

I've been having a bit of a "reluctant to start" issue with my Yammy F150. On occasion, when I go to start, it seems like the batteries are week and almost dead. However, they are fully charged, and read a voltage of 12.6 - 13.0 or more typically.

I seem to recall someone telling me that the voltage is a relatively meaningless number when it comes to starting. It's the amperage that matters. Is that correct?

These batteries are 2 and 3 years old, so based on prior experience, getting old for boat batteries.

Am I right about this? Should I haul them in for a load test or something? Is there some way to test this without taking them to a shop?

I suspect that this has been dealt with somewhere, but I wasn't able to find anything.

Thanks for your insights~

[BogMonster]

In my experience (admittedly auto batteries, but quite a lot with those) a dud battery will usually show up as a low voltage and anything over 12.6 is pretty sound. But the only true test is a load test using a drop tester, given that you can't do anything with most batteries using a hydrometer these days, as they are all sealed.

I'd do two things to start with, firstly check the connections are tight (bad connection equals resistance equals poor starting) and secondly put a voltmeter on it and see what the voltage is when you are cranking the engine over, if it drops back a long way, the battery is kaput.

[Stoo]

Thanks Bog....

I know the terminal connections are clean and tight, so I will try that test tomorrow. One of these batteries is a heavy-duty automotive battery, the other is a deep cycle which I isolate and use when I'm sitting and running accessories. (I can buy automotive batteries with a pro-rated lifetime warranty, the marine battery has a limited 6 month warranty... go figure!)

Thanks again!

[jyasaki]

Actually, my F115 has a similar problem. I'm partly to blame, I think, as I fudged on the MCA rating when replacing. But, a single battery doesn't like to crank, switching to both, even with a mostly drained battery, cranks well and starts with no problem.

I have not gone through and checked all connections yet, as I'm fairly lazy when it comes to stuff like that, and the problem hasn't been bad enough to cause concern (yet.)

Simple course is to pull the batts and drag them down to the local auto shop and have them load test them. Assuming you can get to them.


jky

[Stoo]

I think this must me my battery death week. I picked up one new battery to change out on the boat, only to have the one in my truck suddenly die. So the not-so-good one from the boat is going in the truck, and the new one into the boat. I figure I'd rather be stranded in a parking lot than 40 miles offshore.

The new one is one of those fancy coil jobs... 10 year full replacement (as long as they don't figure out it's in a boat!) warranty. In theory, I shouldn't need to pay for another battery ever again. (Although, I suspect that any replacement battery won't have the same warranty...)

[jyasaki]

Originally Posted by Stoo

I think this must me my battery death week. I picked up one new battery to change out on the boat, only to have the one in my truck suddenly die.

Must have been contagious.

The new one is one of those fancy coil jobs... 10 year full replacement (as long as they don't figure out it's in a boat!) warranty.

What brand? Starting battery, or deep-cycle? And why do they exclude marine use?

jky

[boristhebold]

Ive done quite a bit of research recently on batteries and marine solutions for management and issues, from the reading ive done there is a difference between how marine batteries and vehicle batteries are constructed, the marine ones are built to withstand the knocks from a normal boating life so the construction is different. So you might find the truck battery doesn't last as long as you might hope. It's worth doing some searching around via google on the subject.

[Anchorhandler]

Very slightly off topic....

I borrowed one of these last month from a local(ish) HGV garage to help diagnose a problem with the batteries on my lorry.

BAT 131 Battery and Starting/Charging System Tester

Fantastic bit of kit. Found the problem instantly which was a dead cell in one of the two brand new batteries i had fitted a few weeks previously. Gives all kinds of information on the display without actually simulating a dummy load on the battery.

Simon

[Anchorhandler]

Ouch...

Just Googled the price of it though.....£750

Simon

[A1an]

For those that need a battery... Go Outdoors are selling Numax 75ah Leisure batteries for £60.