Add 2nd alternator for less charging time?

[rgleason]

Johnct61 wrote:
"> You need Solar, or Shore power > or a Honda or other generator
no ICE source makes sense for the long tail, when only say 10A or less are being accepted by the bank."

Also with a bank of 800ah you need a much larger alternator to reduce your charge time. You will probably need a serpentine belt (preferred) or double V due to the loads.

All very very true!

A diy second alternator might work, but replacing the old one is probably most cost effective. Depending on batt type you could use 200a continuous output when hot or more.

Get some solar 100-200 watts with a good regulator or plug into shorepower with a good charger once a week or twice a month. Then plan on equalizing spring and fall if you have FLA batts.

Read for equalizing
http://www.cruisersforum.com/forums/...d.php?t=201841

And for alternator considerationd even though it is for LFP.
http://www.cruisersforum.com/forums/...d.php?t=209089

Read this
http://www.cruisersforum.com/forums/...d.php?t=210628

[stormalong]

Keep in mind that if you replace your stock alternator on a diesel engine, or change the belt ratio you need an alternator with a tachometer tap and will need to re-calibrate your tach. Advantages of a second alternator, leaving the original in place is that you don't have to mess with that and you have redundancy.

I have the original alternator wired to the engine start battery and the second one wired to the house bank. Also have a Yandina battery combiner so both alternators charge both batteries.

[GrowleyMonster]

I am with KP44. A single large alternator (150 or 160a would be nice, 200a if you can find one that will fit) with double belt pulleys for bulk charging. A second alternator for just the start battery. That gives you possible redundancy to cover one or the other failing. For absorption and trickle charging, a couple of solar panels and a proper MPPT controller. That way you can bring the batts up to 100% now and again, which is a good thing for FLA. Charge them full from shore power at every opportunity, too.

[roland stockham]

You say charge rate does not exceed 60a, which is about normal for an 80a alternator, but you don't say how long it stays there for? If you are charging at 60a for an hour or more they you may get some benefit from a second {or bigger) alternator. If it drops from max in less than an hour it is unlikely.

Increasing alternator out put tends to be disappointing as a way of shortening charging time for 2 reasons. First the charge rate is limited by the batteries so once you reach that limit no amount of extra alternator output will make a difference. This is generally around C5 for FLA's. Second . If you increase the bulk charge rate from C10 to C5 the voltage goes up faster. That means you hit the voltage limit at a lower % charge and the current falls off. At C10 you may get to 85-90% still charging a full output. But if you increase that to the C% rate you can reach the voltage cutoff at a significantly lower level, say 75-80%. Result is you get to equalization phase faster but not to 100%. Generally a well balanced system should get from 75% SOC to 100% in around 3 hours. A cheaper and simple option than fitting a second alternator may be a small inverter generator powering the shore power charger. This would also save hrs on the main engine. Running a main engine, especially if it has a turbo under light load can cause maintenance problems