Batteries! How weird they are...

Grumpycat · Aug 2, 2021

LittleBill21 said:
sounds like the larger is sulfated. you would need a load test, your testing shows the smaller battery trying harder, but may be able to release more amperage.

Voltage while starting would be sucked lower if the battery is limiting current. That is why the starting voltage is lower on the smaller battery.

The large battery is not fully charged, that is why after 10 minutes running it is not up to 14.2. Is possible 5 of 6 cells are fully charged (or overcharged) and one is shorted. But that doesn't explain the higher starting voltage.

Fuddy1952 · Aug 2, 2021

Post #13 "I replaced that with a known good car battery." meaning a completely different car battery, one that starts a 4 cylinder car just fine. It also started this single cylinder motor fine, until I was back to square one after a few start/stop cycles.
What I realize now is I should never have posted this to begin with since it starts arguements. I know what works and it worked for me, just trying to help others was a big mistake.

K5lwq · Aug 2, 2021

Fuddy, I am glad you did post. It is interesting for sure and am confident it will be helpful in the future. I think everyone is trying to understand what you are experiencing and trying to relate it to what is understood about batteries.

stevem5215 · Aug 2, 2021

Test the battery properly with a real CCA / AH tester. This measures IR in the battery and will go a long way to telling you the status of the battery. The days of just checking the voltage are long gone.

rScotty · Aug 2, 2021

K5lwq said:
Fuddy, I am glad you did post. It is interesting for sure and am confident it will be helpful in the future. I think everyone is trying to understand what you are experiencing and trying to relate it to what is understood about batteries.

I am too. Fuddy has the courage to have a good idea, and got a lot of discussion started.

Fuddy1952 · Aug 2, 2021

stevem5215 said:
Test the battery properly with a real CCA / AH tester. This measures IR in the battery and will go a long way to telling you the status of the battery. The days of just checking the voltage are long gone.

Post #1 "Although battery was new, I had it professionally checked, it was good and actually measured 717CCA"

grsthegreat · Aug 2, 2021

I too think the tractors charg system will not charge the larger battery properly. I had a friend that had this issue with his dump trailer. After a bunch of trial and error results, he purchased a NOCO Genius prom50 battery charger. Expensive little bugger. But instead of only getting 2-3 lifts per battery charge (off truck alternator) hes getting about 15+ cycles.

Fuddy1952 · Aug 2, 2021

Well...the proof is in the pudding they say.
Remember me saying no matter what car battery I used, a new 700CCA or one out of a running car I could run tractor for hours and never get over about 13V.
Today I bought a 300 Everstart Walmart $39.95 mower battery. Tractor fired right up and running 14.54 volts. Headlights, tail spotlight on it drops to about 13v...but still bright. I shut it off, restarted several times it's like night & day. I even started with lights on...fired right up.
No it may not make sense, all I know is I'm happy and it works great. I just need to fabricate a holder for the smaller battery.

WranglerX · Aug 2, 2021

Fuddy1952 said:
Well...the proof is in the pudding they say.
Remember me saying no matter what car battery I used, a new 700CCA or one out of a running car I could run tractor for hours and never get over about 13V.
Today I bought a 300 Everstart Walmart $39.95 mower battery. Tractor fired right up and running 14.54 volts. Headlights, tail spotlight on it drops to about 13v...but still bright. I shut it off, restarted several times it's like night & day. I even started with lights on...fired right up.
No it may not make sense, all I know is I'm happy and it works great. I just need to fabricate a holder for the smaller battery.View attachment 708120

New hot charged battery with plenty of capacity vs used battery pretty tired and weak on capacity.... I have very old (maybe 15 year old) AGM battery in VW dune buggy... Funny it only gets stated and run for maybe 30-45 minutes once every 3-4 months, this battery contradicts all you science....