Unable to Get a Full Charge

[rebel heart]

Originally Posted by colemj

Those are low charging voltages. Do they stay that low all the way to float?

Our Victron charger, Iota charger, Morningstar solar controller and both alternator regulators have 14.8V as their flooded settings. As did our previous Outback charger and Trace solar controller. And the Xantrex charger before those.

Trojan's specific charger setting recommendation for their flooded batteries is 14.8V during bulk/absorption.

Your chargers and controller may be sensing their internal outputs and not accommodating for voltage drop to the batteries. If so, you should either add an external voltage sensor (if available) or adjust their outputs so that absorption voltage is proper at the batteries (if possible).

Mark

Well golly gee I'm learning new shiznit every day. Just read the PDF from my solar controller and here's what I need to do:

FLOAT VOLTAGE CALIBRATION: Battery float voltage is pre-calibrated to 14. 1 (28.2) volts. In
most installations the float voltage needs no adjustment. Check battery manufacture specifications
for proper charge voltage.
To adjust the float voltage, switch the meter selector to display battery voltage. Remove the top cover of
the M20+. Locate the float voltage adjustment, see wiring diagram. Using a 1/8” flat screw driver. Adjust
the float control in small increments until the desired float voltage is displayed on the M20+’s digital
meter. Clockwise increases the float voltage and counter clockwise reduces the float voltage. Reinstall the
top cover.
The battery float voltage is temperature compensated to properly charged the battery over a wide
temperature range. Battery voltage will be higher in cold temperatures and lower in warm temperatures.

[colemj]

Your float voltage is fine (if not a bit high - 13's would be better). What you want is to adjust your absorption voltage higher. This is where the charging work is done. Does the manual have similar instructions for adjusting the absorption voltage (may be called bulk voltage)?

Mark

[rebel heart]

Negative, that's the only setting. But you're talking about the actual bulk absorption phase, like in the mornings, right? I get the 14.2 all the way across regardless of the charging period. Sucks.. other than that I really liked this controller.

[colemj]

Originally Posted by rebel heart

Negative, that's the only setting. But you're talking about the actual bulk absorption phase, like in the mornings, right? I get the 14.2 all the way across regardless of the charging period. Sucks.. other than that I really liked this controller.

I didn't find a manual for a M20+, but looked at the 2000 manual. Blue Sky sets their bulk charge voltage at 14.0V and expects one to purchase the optional "battery manager interface" to, in their words, "...control a sophisticated three stage charge process which is precisely matched to battery electrolyte type and size in amp- hours. This charge regimen leads to the longest possible battery life while minimizing battery maintenance and water loss."

On this unit, you can set the "charge voltage", but that appears to be the float voltage - and you would not want that to stay at 14.8V.

But don't worry about it because most solar systems on cruising boats operate in bulk current mode without ever reaching float or even absorption because the daily loads are high. So you will get good charging current, but you won't get your battery voltage any higher than 14V. If you sit at float voltage most of the time, this isn't a problem. If not, a monthly charge at a dock with a properly set AC charger will help a lot.

Mark

[Hugh Walker]

Hi All,

Thanks for all the replies, here's an update.

I repeated the test on the 1st charger and it tripped into float early just like the 2nd one... this was a real bummer because I thought just one charger was the problem. It seamed unlikely two chargers would have identical faults so we had to once again consider that the fault could lie elsewhere. Anyway after another marine electrician had us beef up the wiring from chargers to batteries with no improvement we took it upon ourselves to buy (but kept the receipt should it not help) a new Xantrex 40A charger from Budget Marine in St Martin. The idea was if it works, brilliant we know the chargers were at fault, if it didn't help we could eliminate the chargers as a problem. Well... it worked, so we bought a second 40A Xantrex and their remote control/display panel that allows parallel installation (actually very nice to have the remote display to see what's going on). Now our charging is text book perfect!!! We see 80Amps going in during the bulk phase and it doesn't dwindle at all until the absorption stage begins. The Xantrex chargers also have an Equalization mode that runs for 1hr and we ran it 6 times and our hydrometer went from a best reading of 1.20 to 1.24 (still not perfect but a fair improvement, we'll do it again shortly). Our daily genset runtime has dropped from round 4hrs to less than 2!!!

With the help of the last technician after replacing the chargers we analyzed why the alternator was giving us a low output. This had been a big riddle for us because if the alternator was also having trouble charging the batteries how could we say the fault was with the chargers as they're on totally different circuit. This too pointed to the fault being with the batteries or in the wiring somewhere. Well the answer was we were reading the output on our Xantrex Link Pro which is only connected to the service bank, we weren't seeing the charge going into our start or bow thruster batteries. As these were also not fully charged because of the charger faults they were taking a big share of the alternator output, leaving us a low reading into the service bank.

I can't tell you all how much of a relief it is to have this solved, now we can get on with the job of worrying about far less important things

[btrayfors]

Congratulations on solving the puzzle, Hugh.

One thing: don't equalize the batteries too often....each time you do, it can damage the plates just a little, and the cumulative effect can be to shorten the life of the batteries.

Just charge 'em at 14.8, float 'em at 13.6-13.8, and you'll be fine.

Only do an equalization charge infrequently...probably once or twice a year is enough in your situation.

Bill

[Stu Jackson]

Congratulations for finding your problems.

For your Link Pro: Link-series Charging Algorithms -- The "Gotcha" Factor!