Batteries and Solar on the hard?

[KnuckleDragger]

Will be putting the boat on the hard in a couple of months in Puerto Escondido Baja Sur.
Last season when I did this I turned all the loads off, topped up the battery fluid (lead acid batts) and left the solar panels connected thinking that they would keep them at a charged state.
Well, when I returned to the boat in November (6 months on the hard) the fluid level was well below the plates and the batteries were toast!
A cruising friend tells me that he always disconnects the battery cables and leaves them to fend for themselves.
What are the forums thoughts?

420 watts solar through a Morningstar MPPT controller.

[Ryan H]

I would grab a 5 or 10 watt solar battery tender panel and leave it with that.

[zeehag]

once charged, disconnect your batteries. you donot need to continuously charge batts when they are at rest--hook em back up when you return to the boat.
batteries do not lose charge when unattached to anything. if they do, they need to be replaced.

[hellosailor]

420 watts into how many ah of battery?
And how was the controller set?

If you leave wet lead acid batteries standing, due to self-discharge they will form sulfite and take pemanent damage after 30 days of just sitting. Not my opinion, every make says the same thing, some may say 60 days instead.

If you overcharge batteries you will boil them out and damage them--which it sounds like you did. If you match the panel size, or the controller settings, to your battery capacity, they will stay happy unless they are overheating and drying out from that anyway. So you might want to match the charging, but also to top up the electrolyte "over" fill before you leave them.

[KnuckleDragger]

Originally Posted by zeehag

once charged, disconnect your batteries. you donot need to continuously charge batts when they are at rest--hook em back up when you return to the boat.
batteries do not lose charge when unattached to anything. if they do, they need to be replaced.

Battery self discharge rate for lead acid batteries can be from 5-20% according to the research I've done...
Brand new fully charged batteries sitting on a shelf will discharge over time.

[Paul Elliott]

Originally Posted by zeehag

batteries do not lose charge when unattached to anything. if they do, they need to be replaced.

Flooded-cell lead/acid batteries have a self-discharge rate between 1% and 20% per month. I've seen numbers all over the place, but practical experience has shown that self-discharge should not be ignored. AGM batteries have a significantly lower self-discharge rate.

A solar panel with a properly-set regulator (charge-controller) should not fry your batteries. I use my solar panels to keep my batteries charged, and the boat occasionally sits unused for months at a time. My 11-year old AGM's are probably more sensitive to overcharge than are flooded-cell types, and they are still going strong.

[KnuckleDragger]

Originally Posted by hellosailor

420 watts into how many ah of battery?
And how was the controller set?

If you leave wet lead acid batteries standing, due to self-discharge they will form sulfite and take pemanent damage after 30 days of just sitting. Not my opinion, every make says the same thing, some may say 60 days instead.

If you overcharge batteries you will boil them out and damage them--which it sounds like you did. If you match the panel size, or the controller settings, to your battery capacity, they will stay happy unless they are overheating and drying out from that anyway. So you might want to match the charging, but also to top up the electrolyte "over" fill before you leave them.

Two 4D X 180AH=360AH
Yes, they were topped off to the max before I buttoned up the boat. The Baja summer in a closed up boat is obviously pretty brutal! I will revisit the manual for my controller. I assumed that the controller would just keep them topped off like a trickle charger...

[Dos Gatos]

Originally Posted by zeehag

batteries do not lose charge when unattached to anything. if they do, they need to be replaced.

not true

[sailr69]

Originally Posted by hellosailor

420 watts into how many ah of battery?
And how was the controller set?

If you leave wet lead acid batteries standing, due to self-discharge they will form sulfite and take pemanent damage after 30 days of just sitting. Not my opinion, every make says the same thing, some may say 60 days instead.

If you overcharge batteries you will boil them out and damage them--which it sounds like you did. If you match the panel size, or the controller settings, to your battery capacity, they will stay happy unless they are overheating and drying out from that anyway. So you might want to match the charging, but also to top up the electrolyte "over" fill before you leave them.

not true, charged batteries will last for months before fully discharging. how many of you have left your car unattended for months?

[hellosailor]

OK, 69. You're right, and every battery maker who says that every battery self-discharges and takes permanent damage is wrong. You know better than all the battery makers and all the chemists.

And they'll also tell you that if you leave your car unattended for "months", it will kill the battery sooner or later, and there will be permanent damage. The only question is the details, how long a particular car takes, and how much damage.

Not my opinion: The unanymous voice of the entire industry says this. There are plenty of reference books (Eveready and GE used to mail them out for free) and nowadays web sites, but they also all answer technical support calls and will be glad to tell you the same lies directly.

And the problem is not confined to lead acid batteries, it affects all batteries, including NiCd, NiMh and lithium. Look up Sanyo Eneloop batteries, NiMh designed to still retain something like 75% of their power after on eyear on the shelf. Some brands are fully discharged within 60 days. Lithium batteries? Best shelf life of all, but that's why they still have to be replaced in EPRIBs after five years, when they've lost 50% of their power from self-discharge. Any battery that is "ready to go" with electrolyte, etc. in place, starts rotting on the day it was made. The only question, is the details.


KD-
Sounds like the controller is bad, or just mismatched on voltages. With 180AH of batteries, let's say a typical 3% per month self-discharge loss since we don't have a figure for your batteries. That's about 5AH per month lost, divided by 30 days, you should only need 160mAH per day to keep them charged up. Say, about 20mAH continuous trickle from a solar panel all day, so a "dumb" panel of 20-50mA power would probably be a safe blind guess. Assuming I didn't make a math mistake, I do that from time to time.

If your MPPT controller goes into float mode and stays there, and isn't doing something else (some will do an equalize charge every 30 days need it or not) or it isn't using the wrong voltage point...In theory your panels could be idling at something like 20amps, fully 100x more power than the batteries need to see if you just want to prevent self-discharge.
Morningstar should be able to point you at some specifics, confirm voltage points, etc. to make sure the controller is set up properly. If you can't find the gremlin and get rid of it, well...I'd try to check the self-discharge numbers from your battery maker, and if something cheap and simple like a 50mA solar panel is enough to compensate for that, (bleep) it, stow the big panels in the dark and just leave a little one with a dumb charger trickle charging the batteries. When the current is that low, the voltage does't really matter, it will self-limit.

I've seen enough variation between mfr's spec and controller spec (i.e. between Genasun and Deka) so that what one calls "optimum" the other calls outright excessive. With battery types varying 0.2-0.3v, and with "hot weather service" batteries shipping with a different electrolyte to begin with...That's another point, if your batteries weren't made for southern use, they'll be especially vulnerable too.

[Kettlewell]

Also, just the heat of a closed up boat left in Baja will cause some loss of fluid. I can leave my boat with wet LA batteries and solar panels hooked up over the winter in New England for six months with no problems and no major loss of water, but when I leave the boat someplace like Florida with lots of sun and heat I leave only the smallest panel hooked up in case something goes wrong with the controller.

[KnuckleDragger]

Hellosailor,
It's 2X180AH=360AH
The controller has always seemed to be operating correctly. When I'm out and about sailing and not on shore power, it will fully recharge the batts and then go into float mode putting out just a few amps and keeping up with usage.
Don't have it setup to due an automatic equallize. Have to tell it to. Will ordinarily equallize with AC charger.
Thanks all...
Still stumped.

[sailr69]

Originally Posted by hellosailor

OK, 69. You're right, and every battery maker who says that every battery self-discharges and takes permanent damage is wrong. You know better than all the battery makers and all the chemists.

And they'll also tell you that if you leave your car unattended for "months", it will kill the battery sooner or later, and there will be permanent damage. The only question is the details, how long a particular car takes, and how much damage.

Not my opinion: The unanymous voice of the entire industry says this. There are plenty of reference books (Eveready and GE used to mail them out for free) and nowadays web sites, but they also all answer technical support calls and will be glad to tell you the same lies directly.

And the problem is not confined to lead acid batteries, it affects all batteries, including NiCd, NiMh and lithium. Look up Sanyo Eneloop batteries, NiMh designed to still retain something like 75% of their power after on eyear on the shelf. Some brands are fully discharged within 60 days. Lithium batteries? Best shelf life of all, but that's why they still have to be replaced in EPRIBs after five years, when they've lost 50% of their power from self-discharge. Any battery that is "ready to go" with electrolyte, etc. in place, starts rotting on the day it was made. The only question, is the details.


KD-
Sounds like the controller is bad, or just mismatched on voltages. With 180AH of batteries, let's say a typical 3% per month self-discharge loss since we don't have a figure for your batteries. That's about 5AH per month lost, divided by 30 days, you should only need 160mAH per day to keep them charged up. Say, about 20mAH continuous trickle from a solar panel all day, so a "dumb" panel of 20-50mA power would probably be a safe blind guess. Assuming I didn't make a math mistake, I do that from time to time.

If your MPPT controller goes into float mode and stays there, and isn't doing something else (some will do an equalize charge every 30 days need it or not) or it isn't using the wrong voltage point...In theory your panels could be idling at something like 20amps, fully 100x more power than the batteries need to see if you just want to prevent self-discharge.
Morningstar should be able to point you at some specifics, confirm voltage points, etc. to make sure the controller is set up properly. If you can't find the gremlin and get rid of it, well...I'd try to check the self-discharge numbers from your battery maker, and if something cheap and simple like a 50mA solar panel is enough to compensate for that, (bleep) it, stow the big panels in the dark and just leave a little one with a dumb charger trickle charging the batteries. When the current is that low, the voltage does't really matter, it will self-limit.

I've seen enough variation between mfr's spec and controller spec (i.e. between Genasun and Deka) so that what one calls "optimum" the other calls outright excessive. With battery types varying 0.2-0.3v, and with "hot weather service" batteries shipping with a different electrolyte to begin with...That's another point, if your batteries weren't made for southern use, they'll be especially vulnerable too.

without getting into arguments about this, you are right, all batteries do discharge all by themselves. however: lead acid batteries lose charge around 5% a month. more or less. a good set of deep cycle batteries at around 450 amps loosing 5% a month should last 8 months or more to go to 50% discharge or, 22.5 amps a month. hardly anything to worry about for 3-4 months I have been doing this for years with Trojan T105's and they give me 10 years of service. on the second set now for the past 19 years. Trojan said 10 times for complete discharge will ruin the batteries. have not done it once. six T105's now on the boat for the winter disconnected since Sept. the voltage is at 12.1. please don't respond, this is what I do, not asking anyone else to do the same. seems like most people have their own opinion on 12 V DC anyways

[cfarrar]

I leave only the smallest panel hooked up

This makes a lot of sense.

[roverhi]

Batteries will discharge if left without a charger connected. Does not seem to be constant for different types of batteries. Battery in my 300D Mercedes sulfated in 4 months. Have had other batteries go for that long without problems. Small solar panels are so cheap, just easy to buy one and be sure the batteries keep up a charge.

Be very careful hooking up a largish solar panel to batteries without a charge contoller without a regular load. Blew up 4 brand new 400 amp hour batteries when we went on vacation for two weeks. Solar wouldn't keep up with anywhere near our usage in the house but too much input without constant draw down. FWIW, my 225 amp battery bank with 135 watt Kyocera panels and a BZ controller set to 14 volts need water every six months or so. There is stll water above the plates after that time but the liquid is getting down.