Battery Bank

[Jacana]

Whats the best way to look after the battery bank,currently have solar power recharging,motors recharging(when in use) and can hook up to 240v when on my pontoon.Recently installed a new battery bank,is it better to recharge fully each night or only recharge when bank gets low.
Second question,how low do I let battery bank go before fully recharging.
Thanks
Geoff.

[Seahunter]

What kind of batteries and how many? How are they wired and what charging system do you employ?

[noelex 77]

Lead acid batteries are best kept as close to 100% as you can achieve. Discharge them as little as possible and recharge them ASAP to 100% for the longest life.

[Teeto]

Get a smart charger and battery monitor. Keeping batteries at 100% only happens when hooked up to the mains. Don't let batteries get less than 50% ever and charge them daily up over 80% in the morning then let the solar panels trickle charge them all day. Volts is a bad gauge of battery health, you have to know percentage of charge.

[noelex 77]

Originally Posted by Teeto

Keeping batteries at 100% only happens when hooked up to the mains.

You can get them to 100 % with solar, but they will not stay there.
I have not been hooked up to the mains for about 2 years.

[mbianka]

I agree it's best to charge lead acid batteries as soon as possible after discharge. With my electric propulsion bank I have rarely gone below 80% before I start using the Honda 2000 to recharge. But. I'm very conservative and want to avoid deep discharges as much as possible. I also use solar and a wind generator to keep things topped up.

[Seahunter]

Battery type is very important in how one maintains their batteries. Dry batteries (AGM) do not charge and are not charged the same way as wet (lead acid) batteries. Are you employing a 3 stage charge controller for your solar panels? Do you keep load on the system? Is your alternator a twin post or single? Are your batteries 6VDC, 12VDC and in what manner are they wired? Every battery manufacturer has different settings for charging and your charger(s) must be set accordingly dependent upon your battery setup.
It's easy to find the chart for the scale of charge a battery can take. Three month old batteries might only hold a true charge of 90% of their advertised amp/hours. (Nothing to do with voltage but the true indication of battery charge.)
Leaving solar panels unattended (trickling) without going through a charge controller is unconscionable. At minimal it will create stray electricity through your grounding system (to the annoyance of others in your marina), cause battery run away or worse.
Lead acid batteries give the most amp/hours for the buck but take extra care with the maintenance of adding distilled water once a month. Your battery system (if monitored) may drop as low as 10 VDC but it's important to understand how many amp/hours are remaining NOT the voltage. I like to have a separate starting battery on it's own charging system. There's a number of ways to do this; ours is done with a twin post Balmar with one side going to the "house" the other the "start".
Keeping your batteries in good health may entail ever evolving technological changes but remember it's a science, not an art.

[noelex 77]

Originally Posted by Seahunter

Leaving solar panels unattended (trickling) without going through a charge controller is unconscionable. At minimal it will create stray electricity through your grounding system (to the annoyance of others in your marina), cause battery run away or worse.
.

A small solar panel, say under 10w is fine connected to a large battery bank without a controler. This will replace the self discharge and keep the battery bank happy.
Stray current problems are much more common when AC battery chargers are used without an isolating transformer.

[Seahunter]

Originally Posted by noelex 77

A small solar panel, say under 10w is fine connected to a large battery bank without a controler. This will replace the self discharge and keep the battery bank happy.

Nonsense.

[Tristan]

Noelex is right -it's not nonsense. The trickle charging current should be around C/300 (chemistry dep.) which in case of larger battery bank, let say 1000Ah would be ~3A and this is around 40W solar panel.
Stray current problems are AC related. You do not have common ground with the other boats in the DC circuit.
T.

[noelex 77]

Originally Posted by Seahunter

Nonsense.

The solar controller will drop back to a float voltage (typically about 13.7v) when the batteries are fully charged, At this voltage the charge controller will be supplying the average marine battery bank with about 1-3 amps (depending on size).
A 10w solar panel will deliver a maximum current of 0.6A. This low current will not damage the battery and is preferable to allowing the charge state to drop due to self discharge.

I am not sure why you feel this would be damaging the battery. If you outline the reasons instead of just disagreeing we might both learn something.

[denverd0n]

Originally Posted by Seahunter

Nonsense.

No, it is absolutely NOT "nonsense." Noelex clearly understands the subject and the issues being discussed here. You... not so much.

[Matt sachs]

What reading materials would be best for someone like me that knows very little about solar/ battery banks, but wants to know more?

[Seahunter]

A small solar panel, say under 10w is fine connected to a large battery bank without a controler.

Even at 10 watts output without a controller a solar panel nearly .75 amp per hour (over 18 Ahrs per day) will be produced. This is enough to boil a wet cell away in a matter of days. As well a calculation based on 13.2 VDC (closer to a real voltage) and 10W produces nearly .76 Amp not .6 Amp.

It's a common myth that it's AC current that causes corrosion. A boat's main corrosive enemy is DC voltage.If the excess DC voltage exceeds a .5 VDC output you're going to start blowing off zincs. Here's a direct quote from ABYC. "Certainly it has been the ABYC party line for some time that AC is not a contributor to the metal corrosion we typically see on boats. There is no doubt, and certainly not much debate, however, that common causes of corrosion are distributed by the AC system at a dock, via the grounding conductor, or the green wire. These causes can be either at a galvanic corrosion level, or possibly by a stray DC current, induced at battery level potentials."

[Tristan]

Only if you use the metal hull of the boat as a one of the conductors in the DC circuit.
DC should be grounded to the hull at single point or not at all
T.