Do the batteries need to be replaced?

[Maine]

I just installed a Truck Fridge TF-49 I was hopeful that we could be off grid for 48 hours or more. The TF is the only draw on the auxiliary battery system. On our first trip the when we parked the van the voltage on the auxiliary system was 12.8 v after about 12 hours it reads 12.5v by morning it was 12.2v. It was a fairly warm day but cool at night. We limited the times we opened the fridge. When we got home I checked the battery system and here is what I found:
Battery #1 starter battery Super Start #41-7 seven years old.
Initial reading 12.6v
After charge 13.65V
At 1 hour 12.98v
At 2 hours 12.96v
At 3 hours 12.94
At 24 hours 12.8v
Battery #2 (under the drives seat) Brightway Group HX 12-50 50Ah 5 years old
Initial reading 12.25v
After charge 13.15v
After 1 hour 12.82v
After 2 hours 12.79v
After 3 hours 12.75v
After 24 hours 12.6v
Battery #3 NAPA 821-31 N Deep Cycle 100Ah 2 years old (under the sink old hooked in parallel with battery #2)
Initial reading 12.32v
After charge 13.36v
After 1 hour 12.82v
After 2 hours 12.77v
After 3 hours 12.75v
After 24 hours 12.56v
Reading at starter battery when starting the van is 14.2V
The main draw on the auxiliary battery system is a Truck Fridge TF49 (about 2amp per hour).
I’ve had the batteries unhooked for longer than 24 hours and batteries #2 and #3 have settled in at about 12.5v whereas battery #1 (starter) has maintained 12.8v.
So is this what I can expect form the auxiliary system or does one or two of the batteries need to be replaced?

[bobbyblack]

House parallel setup is flawed. You'll have endless problems if you have mismatched batts like that.
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'87 Westy 'Flossie','86 Westy 'R1','86 tintop GL - Subi2.2 'J2','83.5 stock tintop L 'ZoomBus','74 Karmann Ghia, '63 Notch

[Tobias Duncan]

[MarkWard]

I would suggest Googling surface charge. When you recharge a battery you’ll see these higher battery voltages that need to be loaded off to know the actual voltage of the battery being tested.

Regardless, without a charge of some sort, you are running a deficit system. That’s where the appeal of the compressor fridge is lost with me. Battery anxiety.
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[Maine]

OK the auxiliary system
Battery #2 Brightway lead acid sealed
Go Westy Isolator kit we upgraded the wire last year
Negative cable for 1200 watt Coleman inverter
Battery #3 NAPA Deep Cycle
Positive cable for Coleman inverter
Truck fridge TF49
Propex 2000 heater
Shureflo faucet
Radio with CD player
Interior lights
Two USB ports
Battery Tender
I think that's about it. The TF uses the most power. We never use the interior lights we have battery ones. We only charge our phones when driving.

[Maine]

Also planning to install a Blue Sea fuse block this week to tidy up the system.

[oceanair]

What you're being told is that the parallel system doesn't work well. Mixing the two batteries. Looks like you should choose to use only one, the 150ah.
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84 Vanagon Pop Top Conversion from Tin Top, 1970 Ghia - all sweet rides! Love em!
Previous: Green 72 Tin Top, White 72 Westy, Blue 64 Beetle, Yellow 71 Squareback, 2014 Jetta TDI Wagon - wish I could have them all back!

[Maine]

Correction the NAPA battery #3 is 100Ah.

[Tobias Duncan]

It might be worthwhile you sketch out a schematic of how everything is hooked together. Much easier for others to grasp exactly what is going on.

[DuncanS]

Being in the marine industry and working on sailboats which typically will be off grid most of the summer, I totally agree on all the posts about the inadvisability of mixing batteries. Ideally, they should all be the same brand, type and bought at the same time. In your case, I would recommend dumping bat #2 and simply getting a duplicate of the deep cycle one. There is a big difference in the interior structure of a regular high amp quick draw battery--starter types--and a deep cycle--low draw over a long period of time. Do not mix and match. It will cause you problems and quite probably shorten the life of all the batteries. Recommend you research and read about this on Blue Sea and Balmar sites

Duncan

[Maine]

I'm having difficulty finding a deep cycle battery that will fit under the drivers seat. Anyone have specific name or know the BCI battery group number?

[SSWesty]

What type of battery are you trying to fit in there? There are plenty of 50 AH or less options but not so many above 50.

[kamzcab86]

[Maine]

Thanks everyone. kamzcab86 that's the battery I was looking for a 50Ah deep cycle to go with the 100Ah that I have under the sink. One thing I noticed when I was evaluating the batteries is that the 100Ah would charge quickly from 12.1v to 13.6v in 30 minutes or less then discharge to 12.5v also within a half an hour. This was with nothing attached to the posts. It will not hold 12.8v

[SSWesty]

Given the age of the batteries and what you describe your batteries are most likely bad. You'll want to replace them together so a bad battery doesn't damage a good battery. Not only is mixing sizes a not a good idea but mixing good and bad batteries is worse. The bad battery usually always drains the good battery.

Regarding your state of charge questions. Even though the voltage comes up to 13.6 doesn't mean the battery is fully charged so falling back to 12.5 is normal if the battery was discharged. A discharged 100ah battery will take much longer than 30 minutes to charge. The battery needs to be on the charger long enough to get a full charge. I would suggest charging it for 12+ hours with a 3 stage charger capable of putting out between 4-10 amps. A trickle charger isn't going to cut it. Then check the voltage 12 hours after you disconnect the battery from the charger. The battery needs time to "stabilize" post charge then check voltage. You should be seeing 12.7-12.8 volts. If the battery was new you should see 12.8 but it's old so hopeful 12.7.

[Maine]

SSWESTY very helpful. Will my NAPA 12v1 0amp 85-323A do the job? It has a deep cycle/gel/agm option. Can the auxiliary battery be recharged by driving?

[SSWesty]

Yep it looks like that charger should do the job. Not sure about your setup so I can't say if your setup will charge the auxiliary battery or not. For testing I like to use a charger because it's more of a controlled test with few variables.

[Abscate]

Rough rule of thumb

Charge a battery for three times the rating yo get full charge

Let’s suppose it’s an 80 amp hour battery
Charger rated at 4 amps output
Each 24 period would thus give you

4x24= 96 amp hours charge.

Thus, using 3x rule, charge for 21/2 days to reach full charge
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.ssS!

[Maine]

OK the battery is 105Ah the charger is 10 amps = 315/240 so charge for 1.3 days.

[Maine]

Following SSwesty charging advice I removed the deep cycle 105 Ah battery from the van and using Abscate formula I hooked it up to the 10 amp charger for 31 hours. After unhooking it from the charger last night I checked the voltage this morning (12 hours later) and the multi meter reading was 13.02v!!
So now that it is fully charged if I go off grid for a couple of days and it drops back to 12.6v will I have to do a long recharge again?