Max Charge 612 Problems

[Leighton]

I have recently upgraded my charging system with a Zena 200 amp alternator controlled by a Max Charge 612 regulator supplying 4 X 100 amp house batteries.
The regulator has a display which indicates the parameters to which its operating. Before I switch on the alternator the battery voltage is 12.4V (indicated by the BU reading on the regulator) and the target voltage (indicated by CU on the regulator) in 14.6V).

As soon as I engage the alternator the output from the regulator to the alternator rises to 100%. However within 5-10 seconds the battery voltage quickly climbs up to the target voltage and the output from the regulator to the alternator drops back to 30-40%.

The battery bank is well discharged so it s not a case of the battery being fully charged.

To test the system I separated the batty bank into two sets. One set was used to provide a reference voltage (the BU reading) to the regulator and the second set was used as a load. As was expected the BU voltage remained at 12.4 and a large charging current flowed into the second set of batteries. The output from the regulator to the alternator (FE reading) remained at 100%, as was expected.

I’ve carried out the tests to the alternator as recommended in the Max Charge manual and all seem OK.

Can anyone explain why the battery voltage quickly rises to the regulator target voltage?

Leighton

[Kapena]

11.8 volts is 50% discharged. 12.4 volts is not well discharged...at rest it is fully charged, depending on temperature. Are you confused between the charging voltage and the resting voltage?

Sounds like everything is working properly and the regulator is going into the float mode. This is probably around 13 .4 volts (engine running).

If not....easy to check. Measure battery voltage at battery and compare to altenator output. Should be within 100 millivolts. You can measure at battery switch in and out also. Another factor is the current shunt (if you have one) in the battery ground. Measure the voltage from the ground terminal of the battery to the ground of the engine. It should measure only a few millivolts (a factor of charge current).

[senormechanico]

I also suspect everything's working ok. You're just getting to float very quickly at a 200 amp charge rate. If the batteries are conventional lead acid, you shouldn't charge them at more than 25% of capacity, i.e. 400 ah should not be charged more than 100 A. If there's a max charging current adjustment in your system, back it up to 100 amps and see what happens.

Also, with that current capability, I'm assuming you have at least 2 belts driving it.


Steve B.

[Leighton]

Thanks for the response Guys,

I thing you are perhaps correct and I'll carryout a test with the batteries more depleted.

The drive systems is indeed a twin belt system. Although the system is over capacity for charging the floaded wet cells at the recommended 25% of amp hour capacity my aim is to install AGM batteries once the system is working which will accept a higher charge rate.

Leighton

[senormechanico]

Please forgive the following OT.

Let us know what you find in that scenario.
I've had boats with flooded batteries as well as gell cells before, but I'm taking my first shot at AGM's in our house right now. They're supposed to be able to take up to 100 amps per battery as long as the max voltage of 14.7 isn't exceeded.

I just installed 8 100 ah AGM's, a 403 wind generator, an auto transfer switch and an inverter for backup power. We've had several outages lasting up to a day or so this year. Whenever we get a lot of wind, we lose the grid, so the wind generator almost keeps us even if we're careful. Parts of the island were without power for almost a week. It's pretty nice when the power goes out and 2 seconds later, back in business!

[Kapena]

Just remember not to discharge the batteries more then 50%. If they are 100 amp/hrs batteries only take out 50 amp/hrs (it will take 100 amp/hrs to recharge). Any more then this and the battery life is reduced dramatically.

[Rick]

Hey guys, long ago in this section (ELectrical: batteries, etc.) is a detailed discussion as to how "fast" you can charge your batteries. This comes from the Amp-hour law published first between 1920 and 1930 in an industry regognized text book and has subsequently been published and verified several times since then.

You can safely charge ANY lead-acid battery designed to perform proper duty on your boat WITHOUT excessive gassing or temperature rise at a current equal to the number of Amp-hours "missing" from your battery. Even then, the values may be vastly exceeded for short periods of time.

This is true for gel-cell, AGM and flooded-cell (yes, they are all still lead-acid chemistry). Just try to find an authoritative source from a battery designer electrochemist stating than one should only charge at 25% of the Amp-hour rating of a battery. This is a myth that I read in sailing magazines and forums like this one that keeps getting passed on like a wispy rumour.

In some cases the charge voltage will be equal to 15 Volts to initially do this (assuming that you have a current source capable of delivering such amounts). The three-step charging regimen was developed as a simple practical way as a first approximation to achieving the Amp-hour Law charge regimen.

Back to Leighton's problem: Keep in mind that if your battery has lost significant capacity due to sulphation it will not charge accept much current and the voltage will quickly rise to 14.6V WITHOUT recoverning its lost capacity. It may need to be equalized. There could be other problems as well yet this is my first cut at a determination. If the battery is properly equalized so that its internal resistance is low again and that it will charge accept a large current when discharged then you will discover that using the 14.6V (measured AT the battery) acceptance voltage will go a loooong way towards keeping that battery in good shape. Never let that acceptance voltage go below 14.4 V @ 20 deg C else you will be back in your present situation eventually.