Keeping my FLA batteries topped up during 6 months Winter storage in the Med

[Catnut]

Hi all,
I am looking for advice on how I should set up my battery charging systems to maintain the batteries for 6 months while afloat here in a marina in Marmaris Turkey.

I have 800 Ahr of FLA batteries, which I normally keep charged with 4 X 150 watt solar panels connected to 2 Victron MPPT controllers. I also have a 50A Victron Phoenix battery charger that I can run on shore power if I need to.

We are leaving the boat on Tuesday, and are unlikely to be back before Feb 2020 - 6 months.
The temperature here at the moment is 30+ deg C, and reading through old threads, I understand that leaving the batteries without any charging, is a real no-no and is likely to kill them. So, I am thinking of disconnecting 2 of the solar panels and their controller, and leaving the other 2 x 150W panels,
to keep the batteries in float via their Victron SmartSolar controller (100/30).
To protect the batteries from overcharging (I presume that the controller will cycle through Bulk/Absorb after start up every day) I will set the max charge current to 5A.

Does this sound reasonable ? Has anybody else tried this out ?

Tony

[Stu Jackson]

I left my boat for a month and a half. 400 ah FLA wet cells. I put an old 11W solar panel connected to an inexpensive pwm controller. Came back all was fine. That was three years ago, house bank is still just fine. This was in SF during the summer.


You may want to consider just using (getting) a smaller panel for when you're away, maybe not as small as mine was, but yours are sized for real use, not just float.


Other choice is to just leave your panels connected, the battery acceptance and the controllers will not overcharge as long as the V is in float. Consider reprogramming the controllers to always float.


Don't use shorepower when you're away.


Good luck.

[RaymondR]

Trojan has an autofill system for their FLA batteries, don't know how reliable it is.

[Catnut]

Thanks for the advice. I have left the boat now, after covering 2 of the panels and disconnecting them from their Victron MPPT controller. For the other 2 panels, I changed the max current to 2 amps in the MPPT, and max absorption time to 30 mins. So, hopefully that will keep them in float OK

[Bill O]

Originally Posted by RaymondR

Trojan has an autofill system for their FLA batteries, don't know how reliable it is.

Keeping the batteries filled w/water is an important consideration. We don't have any special fill caps designed to retain water and check/fill them once a month (could get away w/a 2 month watering plan if needed). It may be stretching it for 6 months.


There are other auto-watering systems being sold and need to look carefully at the dimensions to ensure it w/work w/your batteries. For example, the Trojan system mentioned is designed for their batteries and probably would not work on my Crown batteries.


Based on your short time frame of leaving, may opt for the expensive fill caps. Would want to monitor the new fill system for a while to make certain it would work unattended.


Bill O.

[RaymondR]

I eventually settled on Trojan T105s, after trying a few other batteries including Crown, and found that they had a considerable water capacity over the plates to where I could fill them entirely, set the solar regulator voltage down to about 13 V and leave them for 5-6 months without drying them below the top of the plates. They weren't being cycled during this period though.

[Bill O]

Originally Posted by RaymondR

I eventually settled on Trojan T105s, after trying a few other batteries including Crown, and found that they had a considerable water capacity over the plates to where I could fill them entirely, set the solar regulator voltage down to about 13 V and leave them for 5-6 months without drying them below the top of the plates. They weren't being cycled during this period though.

Had Trojans on several boats and felt they went down hill a bit on their quality. The Crowns have a bit more Ah (and lead) in them comparatively and been getting good life out of them. The newer caps on on the Trojans are a nice feature, but not enough to switch back.
Good idea for the OP to adjust the voltage down on the controller to reduce water loss. May want to have it slightly higher than 13.0V, but then again losing all the water/dry cells would be very bad.


Bill O.

[RaymondR]

Originally Posted by Bill O

Had Trojans on several boats and felt they went down hill a bit on their quality. The Crowns have a bit more Ah (and lead) in them comparatively and been getting good life out of them. The newer caps on on the Trojans are a nice feature, but not enough to switch back.
Good idea for the OP to adjust the voltage down on the controller to reduce water loss. May want to have it slightly higher than 13.0V, but then again losing all the water/dry cells would be very bad.


Bill O.

My rationale for the 13 V was that since I fully charged them before putting them into storage mode 13 V was probably sufficient to take care of the self discharge. No science to it, just a wild a------d guess.

[john61ct]

Any decent deep cycling battery, the mfg specs include very specific recommended setpoints,

which of course should be followed if you care about their longevity.

[barnakiel]

I noticed that some batteries loose plenty of water while others hardly any.


On one boat we had 6V Trojans wired for a 24V bank. These required monthly filling even when the boat was not used and the charge was a trickle.


On another we had what looked same technology Vetus 12V units wired for a 12V bank. These only required top up when used vigorously in quite demanding daily cycles. Left at trickle in 20 degrees, plates were still covered after 6 mths away from the boat.


Odd, I think. But there seem to be deep brand dependent variables.



b.

[Bill O]

Yes, one would think there would be mfd. specs for storage of deep cycle batteries but did a quick look and didn't see much in this Trojan white paper re; battery storage

Best thing I got out of it was this:
Storing the batteries in a hot environment accelerates the discharge characteristic.


Bill O.

[john61ct]

Every decent mfg has knowledgeable techies available to chat about such details, and send you the much more in-depth level of documentation.

[john61ct]

Bubbling is required to get to Full. But if excessive, just reduce voltage a bit.

As long as V is even .05V above the Full resting point, the bank won't get discharged, unles loads amps are higher than what tge charge source delivers.

But yes, those voltages vary not just by mfg but by product line.

[RaymondR]

Originally Posted by barnakiel

I noticed that some batteries loose plenty of water while others hardly any.


On one boat we had 6V Trojans wired for a 24V bank. These required monthly filling even when the boat was not used and the charge was a trickle.


On another we had what looked same technology Vetus 12V units wired for a 12V bank. These only required top up when used vigorously in quite demanding daily cycles. Left at trickle in 20 degrees, plates were still covered after 6 mths away from the boat.


Odd, I think. But there seem to be deep brand dependent variables.

b.

That is why you need to reduce the regulator or charger voltage. After the batteries are fully charged any further reverse current flow goes primarily towards electrolysing the water into gasses resulting in a water loss.

The current required is just that required to counter the self discharge and that will depend largely upon the Ah size of the battery bank.

[daletournier]

So, if the solar regs are programmed to stay in float mode will wet lead acids be fine for 6 mths without needing to top up the water.

If they are not bubbling which they won't be if held at 13.2v-13.4v I'm assuming they'll be fine?