Batteries.

[Howmanygoes]

I read somewhere, whilst trying to work out my electrical issues, that it’s quite key to have 2 matching batteries (same tech, same amp, same cca)

Having just popped out to check mine they are same make and range but different ratings.

As you look front front to rear

LH-95ah 680 cca
RH-60ah 420 cca

Looking on line at replacement batteries the offerings seem to confirm this. The fitted units came with the vehicle so no idea of age or suitability. Should I swap these before spending more on the alternator swap out.

 

[Towpack]

If the batteries are always connected in parallel I don’t believe it’s that imperative that they’re the same capacity rating. In an 80 series they’re also used in series to give 24v for starting which makes matched rating much more important. What is also just as important is the the batteries are in a similar condition as a bad one will pull the good one down irrespective of what individual rating they have.

 

[uHu]

The important spec is the charge rate/status vs voltage, which in practical terms means that they have to be designed equally and have the same chemical properties.

As an example, say a pair of unequal batteries both have a voltage of 12.8 V when resting after being fully charged, and 12.1 V at 10 % charge. Then, at 90 % charge, one might be at 12.7 volt and the other at 12.6. That means that one battery will be feeding the other. Then, at 50 % charge, it might be the other way around, with number one at 12.3 and number two at 12.4. This means that the two will always fight (or help) each other, and always be at the same voltage but at different charge levels, being forced there by the other in the pair.
Now, if the voltage is different for two batteries at full charge as well, then one battery will never be fully charged.
You only get the full potential out of a set in parallell if they are a matched pair. Otoh, batteries of the same general construction are not that different, so all this theorizing might be a bit ott.

If these two are similar, even if different size, it probably works reasonably well. After all, they have been working well for some time, have they not?

 

[Howmanygoes]

@uHu , thanks for your reply.

You question have they been working well for a while. Well this I don’t fully know. The vehicle was purchase around Christmas and hasn’t had that much use. I have had a number of issues sorting out Tc, IP switch, diff locks etc which have kept it from more frequent use. I have had some starting issues and a leisure battery which may have drained the main batteries p, even with a split charge set up. I have now gone to a dc 2 dc unit but still having trouble.