Battery Health & Charging Options

[BrucePerens]

John and Jessica, See my Norcold install here. It's been working out fine, my rather radical 400W solar install is able to power it full time using two GC2 batteries.

This trip, we ran the Norcold, the Fantastic Fan at full speed, and the bathroom fan overnight and the Blue Seas state-of-charge gauge said 70% charge in the morning. I'm not sure the state-of-charge gauge is properly calibrated, I'll check it with a hydrometer sometime.

That one Optima might be kind of thin for running the Norcold overnight. If you read the Optima specifications, they say it lasts 55 minutes, and they don't say at what current. A house battery would give time for different current drains, this seems to be mainly for the trolling motor crowd.

If you run into problems, go with two GC2s. They're just as robust as the Optima if not more, and less expensive, and two of them have about twice the capacity of the Optima.

[tentcamper]

Battery Maintained or Battery Storage???

Big Difference: One is where you maintain the battery to be fully charged and ready for service on demand. The other is where you want to extend the battery life as long as possible and you have time to charge it when needed.

I have been following the storage method from an article I read by Battery Council several years ago. The issue with maintaining a battery full charged is the chemical reaction on the plates from not cycling the state of charge. I let my battery discharge to about 12.4v before recharging for 24 hours. If you do not have the discipline to check the battery state of charge, you are better off using a battery tender then allowing the battery to discharge to low which can cause permanent damage.

I can not find the article by Battery Council, but Trojan reference it in there storage procedure. They use less than 12.4v before recharging.

Here is what Trojon has on battery storage:

My current battery is 4.75 years old and is at 98% its rated capacity using a load tester. I only have had to add water twice.

[BrucePerens]

There is a high probability that the battery council wrote that before the advent of microprocessor chargers, or even before good current or voltage regulators were common in chargers. Because if cycling a baftery down to 12.4 before recharging was good for the battery, a maintainer with an algorithm to do that would be easy to make.

[tentcamper]

Trojan has this method on there web site for battery storage. Not sure a minder has the current capability to property charge back up from 12.4. I think it would be a full size battery charger.

[BrucePerens]

I think the problem is that the proper float voltage starts with a manufacturer-specified value and a negative temperature coefficient, and the manufacturer doesn't assume that you can reliably program those into your charger or that you have a temperature probe on the battery at all. If you get everything right, being fully charged is the healthiest state for a lead-acid battery. If you don't get those values right, you're always going to be either overcharged or undercharged, and both are sub-optimal for the battery life.

It happens that I can program all of the right voltages into my Morningstar MPPT, and my converter errs on the low side so it doesn't get in the way. And I have a temperature probe. But getting all of that right is probably the exception more than the rule.

[BradS7535]

Just thought I'd post what I've just put on our batteries and how we keep them charged.

Just installed a Pro-Fill battery watering system. Easy to install and my dad has used it on his RV batteries with great success. Fill port is outside of the battery boxes so easy to hook up to distilled water jug and fill without opening battery box. Fills all cells. Also have a battery tender Jr installed with the plug accessable from outside the battery box. When parked at home I just connect directly to the plug and let it do its thing. Keep the tender running all the time while at home.

Also have a 30A circuit breaker installed on the positive battery side that also acts as a battery disconnect switch. I leave the batteries disconnected while parked at home. I haven't mounted the breaker outside the box yet, but it is waterproof for when I do. Once installed outside of the box I'll never need to open my battery boxes!

[jola1925]

Hi, how much solar do you have?
I think I will also try your idea of plugging into my home shore power a few days a month to maintain the battery.

Thanks,
jola

[Bill]

I have a battery tender Jr installed with the plug accessable from outside the battery box. When parked at home I just connect directly to the plug and let it do its thing. Keep the tender running all the time while at home.

I also have a Battery Tender Jr hanging on my garage wall, for when my 2720QB is parked at home. In my case, I leave it connected full-time into the Bargman connector, where the 12-volt line is (of course) connected directly to the battery. Easy to connect or disconnect, no need to remember to connect or disconnect, no need to open the TM. I don't like plugging the TM's power cord into a wall socket. The TM's converter is not well-controlled enough for long-term maintenance.

Bill