6v/12v dual system and maintaining batteries with a solar panel question

[WranglerX]

If it’s really just a 12 volt system as some have said then replace them with a single 12 volt lithium car battery and it should hold charge between uses.

Not quite sure about lithium batteries yet.... But good quality AGM would be my choice for 12 volt battery......

 

[Bill Guenthner]

Not quite sure about lithium batteries yet.... But good quality AGM would be my choice for 12 volt battery......

The pointy being that lithium batteries hold their charge on the shelf for a very long time, months or years depending on the specific type.

 

[WranglerX]

The pointy being that lithium batteries hold their charge on the shelf for a very long time, months or years depending on the specific type.

Maybe so but the 12 volt AGM battery in my VW dune buggy is over 16 years old and buggy start every time I try it....

 

[LittleBill21]

My experience with JD tractors that utilize two 12 volt batteries in series to attain 24 volts is if one battery has lower voltage than other then batteries will only charge to voltage on the battery with lowest voltage. Electrical load on both batteries must be very close to equal.

yep, this is slightly different then what i mean, in parallel, if the wiring is not of equal length the battery with the least resistance one battery will take the majority of the load as crazy as that seems.

 

[Tx Jim]

I'm not attempting to step on any toes BUT IMHO mentioning batteries attached in parallel in a thread that's been established that batteries are attached in series just adds confusion to an already confusing thread for some readers

 

[LittleBill21]

I'm not attempting to step on any toes BUT IMHO mentioning batteries attached in parallel in a thread that's been established that batteries are attached in series just adds confusion to an already confusing thread for some readers

it was mentioned, because a comment was made that the battery's would be at different voltage. they would not be. I was correcting a mistake.

 

[DaveMueller]

it was mentioned, because a comment was made that the battery's would be at different voltage. they would not be. I was correcting a mistake.

Connect two 1.5V and a 9V battery in series. Connect them to a 12V charger. Same current through all 3 batteries. Now tell me how the voltage will be the same across each battery.

Any new, modern, matching pair of 12V SLAs will be close enough in internal resistance to not matter. Put a new one in series with a 10 year old one, and it may or may not work well. But as I said, it's just a tractor. Arguing tenths of a volt is pointless.

Or, as someone else mentioned, if the whole system really is 12V, just put in a single battery.

 

[number two]

Once again,since it's not the case here.
My 1993 Chevrolet K2500 6.5 diesel with 2 Group 78 batteries-I rotated the batteries every year or two.
I was very surprised how long they lasted!

 

[WranglerX]

Connect two 1.5V and a 9V battery in series. Connect them to a 12V charger. Same current through all 3 batteries. Now tell me how the voltage will be the same across each battery.

Any new, modern, matching pair of 12V SLAs will be close enough in internal resistance to not matter. Put a new one in series with a 10 year old one, and it may or may not work well. But as I said, it's just a tractor. Arguing tenths of a volt is pointless.

Or, as someone else mentioned, if the whole system really is 12V, just put in a single battery.

Dry cells chemically produce 1.5 volts (+/-) per cell... Each of the 1.5 volt batteries is one cell.... The nine volt battery contains 6 (1.5 volt) cells ... So you actually have a total of 8 cells.... 8cells X 1.5volts = 12

BUT

A flooded cell actually chemically produces about 2.13 volt (-/+) per cell... So 2..13 volts X 6 cells Equals 12.8 volts... So your "12 volt battery" in your car or tractor is actually 12.8 volts..

SIDE NOTE: a Lithium Ion battery is 3.7 volts per cell.... So your Li-ion "12 volt" battery has is actually 14.8 volts...