This upgrade included the addition of five (5) AGM batteries (GPL31XT), a new 90 amp charger, breakers, smart gauge, and 2/0 ga. wiring and one group 27 lead acid starting battery.
That is a hefty bank/s of AGM batteries @ 625Ah's. You will want to be sure your charge voltages are accurate 14.4V & 13.4V and that all charge sources are temp compensated..
As seen in the photo of bank 1 each battery has it’s own breaker and is wired to a + and - buss.
Issue #1 = Breakers
AGM batteries have enormous short circuit potential, upwards of 5000A + per battery, and breakers generally do not meet the recommended AIC (amperage interrupt current rating). You also do not need nor want one breaker per battery as they are redundant, increase the failure points in the system, and also lead to more voltage drop. In a dead short breakers can literally weld shut if they don't meet the AIC rating. Class T, ANL or MRBF fuses are the proper devices for main battery over-current protection.
There are two banks with there own buss (Bank 1 - three batteries, Bank 2 - two batteries) The buses are connected to an A/B/Both/Off switch so that they can be bridged together to make one complete 625ah bank.
Issue #2 - No need for this switch or two banks.
The most efficient way to wire a bank like this is contiguously as one large bank. This avoids voltage drop issues, keeps the batteries better balanced and leads to considerably longer life when the batteries are charged and discharged as a larger bank. There are a myriad of reasons you do not want two house banks. You already have a redundant / emergency bank there is no need for three nor all the extra connections, switches etc...
This is done for redundancy
You already have redundancy in the AUX / START battery. Splitting the house bank is an unwise choice especially with very expensive AGM batteries.
as well as the ability to be able to isolate each part of the system.
The only way to truly "isolate" a bad battery would be to have an ON/OFF for each battery. If you short a battery on Bank 2 the 10V or 8V battery is still in parallel with the other 12V battery and can still thermally run away. If you short a battery on Bank 1 the 10V or 8V battery is still in parallel with the other two 12V batteries and can still run away.
In a scenario such as this you still need to manually identify the bad battery with a temp gun or isolated voltage readings anyway. By the time you've figured it out a few turns with a 14mm wrench and the bad battery is out of the circuit and you can continue on. In the real scheme of things the dual banks serve no redundancy purpose. The start battery can be switched in to maintain house loads while you identify the issue and take that battery off line. If you never allow your bank to drop below 12.2V then this is such a rarity that it is barely worth worrying about. Best course of action is to leave two "stubby wrenches" sized for the battery terminals mounted close to the batteries. if you never allow your bank to drop below 12.2V then there is minimal possibility you'd ever need that redundancy and your house bank will have a nice loong life and your start/aux/reserve bank will get really bored.
The 90 amp charger has three leads (only two are being used). The charger is used to charge the House banks only and each feed, to each of the banks is also independently fused.
The charger only needs to feed one bank, the house bank, and the ACR can charge the AUX bank. All those extra wires and fuses are simply unnecessary.
There is also a lead acid starting battery for the engine and genset wired to its own on/off switch.
For a boat like your a simple three ON/OFF switch configuration would be ideal and you would not be carrying around "isolated dead lead" that could never be called on in an emergency.. Share the Start/AUX battery between the engine and the genset, for starting both, as well as allowing it to serve house purposes through an emergency paralleling switch. The engine and genset draw so little power for starting that a simple G-31 battery is a perfect match for both and if a deep-cycle is used it can also serve as emergency house loads..
I am now considering the rest of the system details. I originally was going to run an echo charger to charge the starting battery, as the 90 charger has a lead connected to each of the house busses and nothing connected to the starting battery since it is not the same profile.
A flooded battery will not be damaged by using charge voltages for Lifeline AGM's. You already have an ACR and it is a great choice....
I didn’t want to cook it.
You won't unless you believe all the wives tales you read on the net......
I am now wondering if I should just remove the starting battery all together and install another AGM and connect it to the second bank to balance the battery banks to three batteries in each bank for a total of 750ah. I would then use the house bank to start the engine / generator.
No... One battery bank, contiguously wired, for house and one bank for starting. The banks should have the ability to be selected to serve house and starting duties while also being able to fully isolate the other bank. The three On/Off or 1/2/B with extra ON/OFF does this.
I also have an ACR that was stock that I have kept in place. This is so that the alternator can charge the starting battery and the house at the same time. Since the house batteries are so much larger then the start, I am not sure that it will do much good.
The ACR is an ideal choice for this application because it will allow the genset alternator, in conjunction with the 90A charger, to also feed the house bank during bulk charging. The Echo charger can't do this.
**ALL CHARGE SOURCES, OTHER THAN THE GENSET ALT, FEED TO THE HOUSE BANK INCLUDING ENGINE ALT**
*NOTE: For "
full isolation" it is preferable to have a charge bus that can be isolated from the house bank via an ON/OFF switch. This switch should be as close to the bank as possible as in; BANK FUSE>ON/OFF>CHARGE BUS
By using a charge bus & switch the charging remains with the reserve bank once the cross over switches are switched and we're no longer charging a shorted bank.
I thought about removing the ACR and just running the alternator to the start battery.
Do not remove the ACR it is ideal for your configuration. You however DO NOT want to feed the main engine alt to the start battery, it should directly feed the house bank.
This of corse would not be an issue if I convert to all house batteries and remove the Start battery all together.
Again stick with the 625Ah house bank and keep a single starting battery for the genset and engine.
I am running the stock alternator on a Yanmar 3JH2E (55 amp). Since we only run the engine for short amounts of time ( less then an hour) to get out to the river to sail, I don’t see gaining much charge for the house batteries anyway.
It won't do much other than get hot and pump out 20-30A at best. With AGM batteries they deserve a better alternator and regulator but if this is the only time it gets used you can squeak by.
This is why I have not upgraded the stock alternator. I am wondering if I should go with an external regulator though to limit any possible damage due to the larger house bank even if I get rid of the start battery?
Putting an external regulator on that alt is like putting a prom dress on a pig. You can dress it up but it's still a pig. You're still not going to get much out of it and the expenditure would not be worthy of any decent quantifiable gains.
We have 30 amp service at our dock that supplies power to the charger to keep the AGMs topped off.
In order to be kind to your expensive AGM batteries it is not the
amperage we are concerned about it is the
VOLTAGE. The voltage of the charger needs to be carefully set to match the recommendations of Lifeline. The best profile is 14.4V and 13.4V
TEMP COMPENSATED. If your charger does not have an on-battery temperature probe it is not smart enough for Lifeline AGM batteries.
We have an onboard 6.5kw diesel generator that I can run to keep the batteries topped off while on the hook.
It is critical for AGM batteries to get back to 100% SOC as often as is possible for optimal life. Lifeline's also need to be equalized if regularly used in a PSOC environment. Keeping the batteries "topped off" however requires
TIME. Your max charge rate with the charger is 90A or 0.14C (14% of Ah capacity). Lifeline recommends a bare minimum of .2C or 20% of Ah capacity in charge current. At a 90A charge rate you are looking at well in excess of 6.5 hours to go from 50% SOC to 100% SOC, and this is with healthy batteries. Unless you plan to run the genset for hours & hours & hours "topped off" is pretty much Disney fairy tale and where solar can help. This is also why keeping the ACR is beneficial because now your small genset alt (if it has one) can add another 20-30A to the 90A charger in bulk.
We usually only go over night for a few days at a time so managing the AGMs back to 100% is not an issue.
If this is the case 625Ah of AGM is a huge expenditure when not taking advantage of the fast acceptance benefits.. I might suggest taking one of the 31XT's and use it as the new start battery and continue on with a 500Ah house bank.
It is only my wife and I and my largest draw is the refer. Everything else has been converted to LED. We also have a Gantz 55watt solar panel and regulator that is used to keep the start battery topped off while we have the power disconnected. I am looking at installing more solar (325 watts) in the future to help get the AGM’s to 100% during the day.
Do you actually know your daily consumption in Ah's? This would have been the
optimal starting point in the system design.
So I guess my questions are these:
- Should I remove the lead acid battery and install another AGM to the house system? If this is the case I need to do this now so that all my batteries are of the same series / age. Or is it better to have the redundancy of a stand alone start battery even thought the house banks are not the same size?
Keep two banks HOUSE and START. Remove one 31XT from the house bank and make it your new start bank. Wire the other four 31XT;s as your new house bank with no switch between any of them...
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Should I install an external regulator to the Alternator?
Not on that alt there will be little to no benefit. It is far to anemic to charge even 200Ah's of AGM's let alone 625 Ah's..
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Should I just remove the ACR all together and have the alternator charge the start battery if I elect to keep it or charge just the house battery and use an echo charger?
Se answers above..
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If I keep the Lead acid start battery, should I run the Echo charger from the house bank or can it be run off of the third lead of the charger?
If you stick with a 625Ah house bank just use the ACR to charge the flooded battery. All charge sources except the genset alt go to house.
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Am I missing something so blatant it has eluded me?
Might have been a good idea to ask some of these questions before committing...