Help me not kill another battery bank

[crayiii]

11 months ago I had three Mastervolt 225ah AGMs installed in the Caribbean. They now drop to 11 volts overnight with very little power draw.

I'm now installing six G31 Firefly Batteries but I'm really wanting to understand where it all went wrong with the Mastervolt batteries.

We are full-time cruisers on our sailing catamaran. We have 1000 watts of solar with Victron MPPT controllers, two D400 wind turbines, two 125 amp alternators, and 80 amps of chargers for shore/generator.

Two months after having the batteries installed, we sailed to the US and had the dealer do some work on the battery cables to ensure they met ABYC standards and were as efficient as possible. This includes increasing cable size, adding busbars, fusing, and installing a Victron battery monitor. Before the work, it is possible that the batteries weren't charged very well since all we really had was a voltage alarm (that never went off). We never ran the generator and rarely ran the engines so charging was mainly solar/wind.

Three times since installing the batteries we have been in a marina on shore power for extended periods of time. During this time, we leave the shore chargers on as well as continue running solar and wind. The batteries sit at 13.8v except in the mornings when the solar turns on and goes through a cycle.

Twice after leaving a marina and twice after extensive motoring (>24 hours), the batteries have shown full charge and over 13 volts but after the engines are shut off and there's no other charging source, the volts drop to below 12 rapidly. All but this last time, they've recovered and we've kept going. This time, even after a full day of sun and hours of generator run time, the alarm is going off by midnight (even with almost everything shut off).

Another data point is that I've never seen this battery bank take more than 50 amps when charging and most of the time, it maxes out at 30 amps. I tried running all charging sources yesterday when the bank was showing 11 volts and 40 was all it would take.

Were the batteries bad to begin with?

Did the first couple of months without solid charging (getting them to 100%) kill them?

Did shore power plus solar/wind overcharge them?

Are the wind turbines with their dumb dump regulators causing problems?

I'm really not wanting to repeat this again with the new Firefly Batteries but I'm just not sure where we went wrong and would welcome advice from those with a better understanding of this.

[Chotu]

Can you list the charge parameters from your chargers? Ie: bulk charge voltage, float voltage, etc?

Probably the solar and wind charge parameters are the most important.

[crayiii]

Both solar chargers have the following settings:

Absorption - 14.25 (Mastervolt spec)
Float - 13.8 (Mastervolt spec)
Absorption duration - Adaptive
Tail current - 2.0A
Equlization is off
Temperature compensation is on

The wind turbines simply send output to a dump resister at 14.2V

[Chotu]

And do you know how many AH your battery monitor shows you using each night when it’s not windy?

To determine the depth of discharge on a nightly basis.

[crayiii]

The only things running are refrigeration that in total take 16ah and have maybe a 50% cycle and the anchor light. I generally see about 8 amps being drawn when there is no wind.

[Chotu]

This is definitely a mystery and the only logical answer, assuming everything is working properly, is that the batteries were bad to begin with. Were they fresh?

You got them in the Caribbean. Depending where, they may have been sitting around a long time before you bought them.

Your system is remarkably similar to mine, except I have no engine charging capability.

Any equalization sessions performed over their life?

[crayiii]

Also, the slightest wind or sun and the voltage stays in the mid 12's even when we see 15A being drawn.

[crayiii]

Originally Posted by Chotu

You got them in the Caribbean. Depending where, they may have been sitting around a long time before you bought them.

We bought them in Martinique and have no idea how long they where sitting on their floor. It doesn't seem like the 225ah Mastervolts are very popular. I'm fact, I can't find them at all now.

[Chotu]

Originally Posted by crayiii

Also, the slightest wind or sun and the voltage stays in the mid 12's even when we see 15A being drawn.

Eh... this information is a gray area anyway. Once the charging sources come on line at all, even with damaged batteries, all bets are off looking at the voltage as a determinant of battery health.

You could pull the bank entirely out of the boat and still see the same mid 12’s with some solar starting to kick in. Not an important factor.

[Chotu]

Originally Posted by crayiii

We bought them in Martinique and have no idea how long they where sitting on their floor. It doesn't seem like the 225ah Mastervolts are very popular. I'm fact, I can't find them at all now.

This is a very likely situation then.

Can you check the serial numbers on all 3 batteries?

Format: YMddZnnnn
Y = Manufacturing Year according to DIN41314, always a letter
M = Manufacturing Month according to DIN41314, can be a letter or a number
dd = Manufacturing Day, always two numbers Z = Hardware version, always a letter
nnnn = Manufacturing index number, always four numbers.

[sailorboy1]

Where are you measuring the battery voltage and with what?

If you disconnect them frpm the system and each other and allow to rest what the voltage of each

[crayiii]

Originally Posted by sailorboy1

Where are you measuring the battery voltage and with what?

If you disconnect them frpm the system and each other and allow to rest what the voltage of each

I've measure each battery at the terminal, I've also measured at charge sources and battery isolators. I've also checked all these with a clamp to see if anything weird was going on current wise. The meters are Fluke.

Resting voltage is difficult while at anchor since we're living on the boat.

I know it's really just a guess but yesterday I ran the generator until we were seeing 14.2V and 5 amps being accepted. Everything but one fridge and the anchor light was off. The bank was 11.2V within 7 hours of the sun going down.

[Chotu]

Date of manufacture?

It’s pretty much the last variable unless a piece of equipment is malfunctioning

[crayiii]

Originally Posted by Chotu

Date of manufacture?

It’s pretty much the last variable unless a piece of equipment is malfunctioning

I'm waiting for the misses to wake up before getting down there and making noise. She was woken up at midnight to alarms then the generator so I'm tiptoeing.

[Chotu]

Originally Posted by crayiii

I'm waiting for the misses to wake up before getting down there and making noise. She was woken up at midnight to alarms then the generator so I'm tiptoeing.

Oooh. Yes! Please take your time. Ha ha.