Battery voltage loss

[pepmyster]

Here we go. We have 4 house batteries. All connected with 2 gauge on the rear 3 which are in parallel. If I was to do an amp test on just the rear 3, I get an average of 1450 cca. The 3 are 750 cca rated deep cycle(flooded). If I do the same test from the front main house battery, I get 1100 cca . So 4 house, all excellent shape, all 750 cca, and I get only this. Bull I say. The distance between the front house and the rear 3 is 8 feet, But, using proper connectors and wires. I did the voltage drop calculation and it should be around .01 volt dc. Even with our solar panels, we had 1 day on the hook which was cloudy, so the only thing running was the vacu-flush and fridge. The next day, it was like the fridge wanted to thaw. I wondering if the battery isolators have anything to do with my draw.

[Midnightsun]

What group size batteries are we talking about and whats the AH (amp hour) rating on them? CCA a is only an indicator of how much juice they can produce while cranking and not how much juice they can store. Point is, one can have a smaller group 24 battery that can produce 1000cca however it would not be well suited as house bank battery on a larger boat as it is too small

[pepmyster]

All group 27 . All have 170 ahr reserve.

[bud37]

Amp hours capacity and reserve capacity are two different values.

[pepmyster]

I get it . Trust me. I’m finding it hard to believe that with 4 house batteries my fridge starts to thaw after 1 bad day of clouds………

[km1125]

Well, 4 group 27's would be fine to run a fridge for 24 hrs, but what else was drawing current from them? What was the voltage at the fridge when it was in "defrosting" mode? Some have a low-voltage cutoff so even if the batteries still have capacity if the voltage drop to the fridge is enough it might trigger that "low voltage cutoff" circuit and would need to see ~13VDC to reset again.

[Viper]

QR_BBPOST.... We have 4 house batteries. All connected with 2 gauge on the rear 3 which are in parallel......

I'm assuming all 4 batteries are in the same bank and they are ALL wired in parallel correct?

QR_BBPOST....If I was to do an amp test on just the rear 3, I get an average of 1450 cca. The 3 are 750 cca rated deep cycle(flooded). If I do the same test from the front main house battery, I get 1100 cca . So 4 house, all excellent shape, all 750 cca, and I get only this.....

You're assuming because they're all in the same bank and the same batteries that they're all going to degrade at the same rate but that's not the case, there's just too many variables affecting performance and longevity for them to be consistent with one another over time. That's why it's common for just one in the bank to fail and bring the rest of them down with it.

Are all the batteries in the bank the exact same spec and bought at the same time? Are the fluid levels checked periodically and are their levels relatively consistent throughout? Is the area of the 3 any different in ambient temperature than the area of the single battery? Is the charger's output temperature compensated?

Are your charger outputs running through an isolator? It shouldn't be if it has enough output legs (banks) of its own.

[pepmyster]

All batteries relative to age. Very fussy on maintenance. Always checking the levels. When batteries are tested, individually, they are all stellar. Temp all the same. Very strange, when I noticed solar not perfect that day. Only fridge was on. No stereo , nada.

[bud37]

Well if all is ok then perhaps it is just that the fridge itself has given up.

Seems to me I remember you installing a battery monitor with a shunt when we were discussing your battery banks and solar panels a while back........that monitor should give you lots of very useful info as to what is going on here.

[pepmyster]

Yes, the Victron 500 amp shunt. That’s where I saw the batteries going low. You gotta live boats!