Adding 2 more T-105 questions.

I do not think you will loose ANYTHING .. In fact you may well gain capacity or rather perceived capacity.

This is how my GP24 12VDC battery bank is configured using BLUE SEA Battery switches... I am currently now using a 600WATT PSW INVERTER setup.



If I was to use two groups of 6VDC T105's golf cart batteries I would probably hook it up like this drawing.


Using the meter shunt in the NEGATIVE TERMINALs of the battery bank would look something like this...




Roy Ken

Roy, great diagrams...

One question do I mix old and new 105's in one bank or keep them separate?

Ron

Moved from technology corner

I run a bank of 4 T-125's as one single bank and really like the simplicity and advantages. As long as the batteries are reasonably matched, shouldn't have a problem.

If old and new SG is close to the same I'd get a harbor freight battery load tester and using Mex's guidelines for 6V do a load test on old and new. If the results are reasonably close, I'd wire them as a single bank of 4.

Why?
1) if you run a heavy inverter load, voltage drop won't get you an undervoltage alarm (50+A)
2) under what may be "typical" discharge, you may actually gain useable AH vs. a bank of two. for a "typical" 5-10A draw, looking at Trojan data, you'll be near 500AH since your closer to a 40H rather than 20H discharge rate.
3) it's easier to wire, and can use a simpler battery disconnect switch.
4) you can run at least twice as long before needing to mess with anything.
5) when you do need to charge it's quicker both getting to a 90% or so SOC and getting to full charge than charging individual banks seperately.

Here is what I recall Mex suggesting for GC battery load test. test each battery individually, not wired in series as a 12V bank

220A for 20 seconds and measure voltage under load at 20 seconds. IIR you should see 5.5-5.6V on good batteries.

if the load test results are drastically different, then I'd wire them as two banks.

Batteries that check out that well can be paralleled. Just ID the weak sister cell of the original 6 and keep your eye on that one. I HATE splitting banks. Absorbsion charge amperage gets chopped in half. Finishing charges are ridiculously low amperage. it's OK jumping from RV park to RV park but then why even have four batteries never mind a switch.

SELECT 12 amps charge or 24 amps charge, or better yet, forget to switch and really make your day...

MEXICOWANDERER wrote:
Batteries that check out that well can be paralleled. Just ID the weak sister cell of the original 6 and keep your eye on that one. I HATE splitting banks. Absorbsion charge amperage gets chopped in half. Finishing charges are ridiculously low amperage. it's OK jumping from RV park to RV park but then why even have four batteries never mind a switch.

SELECT 12 amps charge or 24 amps charge, or better yet, forget to switch and really make your day...

Mex:
In my post above did I get close to the right test for GC testing that
you posted year(s) back? If not please correct. Thanks

Great JR,

You have a good understanding and are asking the right questions.

In simple response, lead acid batteries do not play well together - no matter what. I have done electrics on performance cruisers (read - retired racing yachts) for years and this is a constant issue. Even if you have batteries with consecutive serial numbers, they will age differently enough to mess up everything....

But, if you charge each bank separately, you can get each to full density and then combine them for discharge and get very close to rated capacity. If you try to do this with them joined, one will always be selfish and hog the charge current. The fact that one set is 5yo does not even have an effect on the overall situation. They could be twins and you will still see an advantage by charging each separately.

Then, it only comes down to the inverter holding the load. By the way, the labels on microwaves virtually always disagree with less than lab grade instruments. That is great, because the readings you get from a Kill-A-Watt (~30$) are closer to real world than what the lab grade stuff reports.

Matt

ktmrfs

You done good laddie.

Since there seemed to be some interest in my post above, I can add, when a month passes and voltage across each three cells differs by .2 volts for the entire group, STOP. The batteries are throwing spitwads at each other.

The older batteries would be lower and it's time to install a headache inducing inefficient switch or replace those pampered golf car originals.