Still confused about charging!

Stu Jackson · Dec 23, 2015

Very good advice.

Maine Sail's own website discusses this in his How to Wire a Battery Monitor. And there's also this "Gotcha" I wrote some time ago:

For everyone installing a battery monitor: The "Gotcha Algorithm" thread, a "MUST READ"

http://c34.org/bbs/index.php/topic,4922.0.html

DEFAULTS are factory settings that are made to be modified to suit your setup.

Here's his:

How to Wire a Battery Monitor by Maine Sail: http://forums.catalina.sailboatowners.com/showthread.php?t=125606

Maine Sail said:
Seems like a battery monitor calibration issue as well as other sources possibly playing ping pong.

Maine Sail · Dec 23, 2015

gettinthere said:
Made significant adjustments to the victron per mainsail guidance. But they're never perfect. I havent been to 100% SOC in about 2 months.

Yeah you're waaaay off. These things can get out of whack in less than a week away from shore power.. Anything beyond a week start charging at 12.2V and ignore the bat mon for SOC...

Stu Jackson · Dec 23, 2015

Then it really sounds like a time to go thru the Gotcha thread and MS's and recalibrate the Victron.

Maine Sail · Dec 23, 2015

gettinthere said:
I wait till dark when the solar is off, turn off the wind gen, make sure the refer and other hi loads are off and check voltage. Try to keep it above 12.5v. I know that isnt fully rested but I feel its a good working level for a full time system. Watered batts last week after about 6 weeks and they were sipping very little.

Even if under your normal average house loads, not resting, start to charge at 12.2V.. Your bank capacity to discharge rate ratio is wide so 12.2V under load should be pretty close to 50% SOC under normal house loads......

Maine Sail · Dec 23, 2015

gettinthere said:
12.2 gets close to 50%. So starting charging at 12.5 will be around 70% which is even better, less strain on the system, eh?

Absolutely.....

Maine Sail · Dec 31, 2015

gettinthere said:
Due to lots of cloudy days and high heat and humidity, batteries have been dropping. Got down to 12.2v last night. Time for a heavy blast. But when I try, the Pro Mariner refuses to put out full. I changed it to the 14.8v manual setup and it does show 14.8 but only about 24 amps. I am also trying to run the zantrax trucharge 40+ charger and the solar panels are putting out 5 amps as well. Victron says 14.1v
When I had 2 zantrax 40s, I could run both of them, sunny day solar 280w, windy for the wind gen and run the engine at high idle and get well into upper 100s amperage. I dont think I like the pro mariner.

If the Sterling is at 14.8V, at its end of the wire, and the battery bank is at 14.1V (needs to be confirmed with a DVM) then there is some serious voltage drop between the Sterling and the bank, 0.7V worth.... Sounds as if the Sterling is at its limit voltage and it can't put out its full amperage because it is "voltage limited". No charge source can put out full amperage once it exits bulk/constant current stage and enters the voltage limited stage.

We really need clamp meter and volt meter readings of the various sources including voltage drops between charger end and battery end.

Maine Sail · Jan 10, 2016

Y

gettinthere said:
V at output terminal of charger 14.5V
V at battery terminal 13.8V

You have some pretty serious voltage drop in the system wiring, -0.7V at 27A is simply unacceptable. and your low amperage is a result of the charger being at absorption, holding voltage steady, and liming current, yet the batteries are only at 13.8V.

Voltage is the "pressure" that allows the current to flow into the batteries. You should see no more than about a 0.2V difference between the battery terminals and the charger terminals. If you do there is a serious voltage drop issue. Until this is corrected you won't get good charger performance.

Maine Sail · Jan 10, 2016

gettinthere said:
State if charge is low 70% area. Fire up zantrax trucharge 40+ and get about 38 amps. Fire up pro mariner 40 and get 40 amps for about 2 minutes and then 22 amps. This is with either or both chargers running. The promariner refuses to put out more than 25 amps continuous. Its the exact same wiring that the other zantrax was using and putting out 35 to 40 amps regularly. Promariner is set to manual and voltage is 14.8.

Based on the above post this is a voltage drop issue. Until that is corrected we can't really blame the charger.. Also it may be a battery temp issue too. Unplug the temp sensor and then run the same tests...

Maine Sail · Jan 10, 2016

gettinthere said:
Batteries are 77d. The old zantrax, and the other one, dont seem to have this issue. The pro mariner 'ultra sensitive' compared to zantrax?

Voltage is voltage you may have a loose connection. I have sold about 120 of these (Sterling version) and installed about 35-40 and they all put out full amperage, if the wiring is correctly sized. As I mentioned the charger simply can't put out full current with a -0.7V drop...

What GA wire, how long are the positive and negative cable runs and what do they pass through on the way to the batteries?

druid · Jan 10, 2016

I've never been a fan of the Idea that terminal voltage is proportional to charge, especially if you're talking a few 1/10ths of a volt. Go ahead: put a load on a battery for a while, then take the load off and watch the voltage change by like 1/2 Volt over the next hour. Or, fully charge two identical batteries. Put identical loads on them for a period of time, then take the load off and note the voltage. Bet it's different by over 0.1 volts. You can get an IDEA of charge state from the voltage, but there's surface charge, internal resistance, contact resistance, recovery...

The ONLY way to really tell the charge state of a lead-acid battery is with a hydrometer. Have one handy...

druid