Location: Ignacio Colorado (72.161.117.156) | Thought I would start a battery thread instead of adding to the fridge thread going on.
House battery's that are low on water should not be filled to top then charged. If top of plates are under the fluid, charge the battery first. The electrolyte soakes into the plates as the battery discharges and during charging it is forced back out. If you fill the battery while dead and charge you get more than it can hold and it runs over. If you can see plates above the electrolyte that portion of the battery plate is dead forever.
Plugging in to shore power does not charge the house battery unless you have a different converter/charger than stock. It holds the system at 12.7v or so. That's not charging its holding.
Now let's do some math. A 220 ah (amp/hour) battery bank will take some time to charge from dead. Say your charger is putting 20A (amp) into the bank. One hour later you have 20A times 1hour, so 20ah. That battery is still dead, 10 hours at 20A and you are back to close to what it should hold.
The alternator puts out 14.4V but I'll tell you that does not bring back a dead battery. Maybe gets you enough to think you are good but it doesn't "fill" the battery.
First guy that told me the car charging system does not recharge a battery properly got set aside as crazy. Well he was right. It maintains your battery but can't get it where it needs to be.
People that run their radio for hours with the engine off are slowly emptying the bank. They think they are charging it back up when driving but the battery salesman loves that guy. You get some put back but not the real charge it needs.
When I got involved with solar power charging batteries I learned a lot about battery condition. Also for the last 20 plus years battery design changed and a dead battery won't start to charge until it sees 16v. the voltage builds above that point then slowly comes down as the battery is reminded it is a battery. Voltage then slowly builds back up. When it is back above 15V you can watch the voltage climb, then drop a few tenths of a volt and start to climb again. That is the sulfation of the plates being dissolved and that portion of the battery coming back to life and storage increasing.
An abused battery acts like it is full but just gets smaller (ah) and smaller.
It's a science of its own and understanding how it really works may save you some $$ down the road.
Bill
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