Sailboat Power

[inetdog]

It sounds like I should run the high output alternator to the bus as well so that it charges all batteries at the same time. I make an assumption here, which may be errant, that with all the attached battery banks that the charge will distribute reasonably evenly to all attached batteries. Adding ACR's should help "sense" charging, but I wonder if they regulate the charging current to the bank once the batteries are down in charge for a Bulk charge? Perhaps I should add some device to regulate charging voltage. Preferably, I'd love to have some type of step charging that puts higher voltage during Bulk and lowers voltage at 80%-85% charge. Perhaps the ACR does this, but just thinking out loud here.

Take a close look at the SmartGauge website. http://www.smartgauge.co.uk/technical1.html.
I always refer people to his page on interconnecting batteries for some good advice and sample numbers. But there is a lot more information in the other pages concerning all the different way of using a single charger for multiple battery systems (the main application of his products) as well information on battery systems for canal boats ("longboats"), some of which may transfer to the sailboat environment too.

Spend some time there!

[D_e_n_n_i_s]

Holy cow !! I can see that I'll be spending hours at the Smart Gauge website !! Thanks for an incredible resource link !!

Peukert's Equation-That will change my battery computations !! The heavier the discharge current, the less apparent battery capacity ...

The real explanation behind that 50% charge rule - Less discharge=longer battery life with 50% a good balance

Dump the split charge diodes for alternator controllers - The diodes are supposed to only allow current flow in 1 direction to allow the alternator to charge each battery bank, but current can't flow back the other way to affect other battery banks ... but ... voltage drop associated with diodes is not constant so battery sees lower voltage from alternator drastically reducing charging capacity ... wasted energy warming up the diode ... so much good info!

Always discharge a battery by more then 5% or it can shorten the battery life ... Never heard of that

Battery Isolator Switches - Always wire to the positive side !!

Hooking alternator to charge both engine and house battery banks-Minimize connections to reduce resistance and always keep a load on the alternator so watch that battery isolators are set to "on" before charging ... other wiring options ...

Hours and hours to be spent on the website

Interconnecting Batteries - Terrific article !! Using diagonally opposite posts from positive (or neg) of last battery in bank to negative (or pos) of first battery in bank makes a tremendous difference in balancing the load across the batteries in the bank both for discharge and charging !! I would think this would be even more important in AGM batteries with lower internal resistance.

Great stuff - Thanks again !!

[ChrisOlson]

Peukert's Equation-That will change my battery computations !! The heavier the discharge current, the less apparent battery capacity ...

In theory it does. In practice, usually not so much. I got two battery monitors on our home off-grid system. One has Peukert compensation and the other (TriMetric) doesn't. On a long PSOC (Partial State of Charge) cycle with loads varying from bending the ammeter needles to trickle charging the TriMetric is usually more accurate than the fancy one.

Ralph Hiesey, who is a brilliant engineer and the inventor of the Bogart Engineering battery monitors, has lived and breathed batteries and tested them for almost 30 years. He explains why Peukert compensation doesn't really work in the real world:

http://www.bogartengineering.com/sites/default/files/docs/PeukertsComments.pdf

And the proof is in the puddin' as they say. I'll put a TriMetric up against any other battery monitor made for accuracy in measuring SOC and remaining capacity in the battery and it will usually win. Especially on PSOC cycling which few battery monitors built, except the TriMetric, are able to track properly. The new TM2025's give you information on cycle efficiency of your battery so you can plug in the correct CEF.

[D_e_n_n_i_s]

Ralph Hiesey, who is a brilliant engineer and the inventor of the Bogart Engineering battery monitors, has lived and breathed batteries and tested them for almost 30 years. He explains why Peukert compensation doesn't really work in the real world:

http://www.bogartengineering.com/sites/default/files/docs/PeukertsComments.pdf

Less important at the lower discharge rates typical of off grid power systems ...

Reason: The higher amps drag down the volts more than a lower amp load ... So you get to the final 10.5 volt finish line faster

Technically, this effect is caused by the internal resistance of the batteries, and also by what is called “polarization” of the electrolyte in the battery, which causes the voltage to be dragged down when the load current is higher.

Terrific explanation !! Thanks for the article link !!

[ChrisOlson]

Less important at the lower discharge rates typical of off grid power systems ...

Reason: The higher amps drag down the volts more than a lower amp load ... So you get to the final 10.5 volt finish line faster

Yeah, according to Peukert you can have say a L-16 6V battery with 401ah @ the 20hr rate. And that battery has only 330ah @ the 5 hr rate. But if you discharge the battery at the 5hr rate for awhile and use up 330ah out of it the battery monitor with Peukert compensation says the battery is dead - 0% SOC. The Trimetric says it still has 71 ah left in it. What I have found is that what Ralph says, and what the TriMetric says, is 100% true. Take the load off that battery, the voltage rebounds, and if you finish discharging it at the 100hr rate you can get your last 71ah out of it.

And that is why the Bogart Engineering monitors have become almost the defacto-standard that all others are measured against, and have been for over 20 years. The TriMetric can be off sometimes on a recharge because the cycle efficiency depends on DoD and how long the battery has been cycled in the most efficient part of its charge curve up to ~80% SOC. And you plug in a fixed CEF (Charge Efficiency Factor) into the monitor so it can't always compensate for that. But it's a heck of a lot closer than most others I've worked with and it keeps a history on the last five cycles that tells you what your cycle efficiency is so you can adjust the CEF to reflect how you normally cycle the battery.

The beauty of the TriMetric is its simplicity in setup and the fact that it's "close enough" without having to mess with settings all the time. I hate tools that you constantly have to calibrate and adjust to insure their accuracy in order to be able to trust what it says. And that's what I absolutely love about the TriMetric - if it says the battery is at 60% remaining and you can discharge to 50%, you can rest assured that the battery has 10% of its usable capacity left yet without questioning it. On a sailing yacht, 9 days out to sea, that sort of information is what I call "Critical. Need To Know. Information".