OK I am thinking of adding a SI ACR for keeping my start battery charged.
I have solar and my solar charger does charge my start battery but I am guessing it does that when it senses a high charge rate and the starter battery some times is not always charged to at least 12.5 and I do have a switch to combine the house batteries with the start battery when needed .
I use the start battery for starting the Yanmar and my FP Gen.
So a lot of times I need to turn the combiner switch on when motoring or all day when the solar is charging but need to make sure I turn that switch off over night when anchored and so thinking of adding the SI ACR to always keep the start battery charged up with out draining down the house bank,are there different model SI ACR and if so witch one should I use.
Nick
We really need a lot more info on how the system is currently wired and set up.
#1 Battery switching?
#2 What solar controller do you have?
#3 How is the solar controller wired?
#4 Solar should NOT charge the start battery first with an ACR as this will cause relay cycling and the house bank may never get charged. All charge sources should be fed to house then a CMD (charge management device) such as the ACR can keep the start battery topped up once the house voltage attains 13.0V.
#5 If the system is wired correctly, all charging fed to house bank, then you can use the smallest ACR they make. The start battery should always be at or near full and should never need more than 65A (the smallest ACR). By wiring an ACR
incorrectly, meaning all charge sources to start battery the ACR will need to pass all the current necessary to charge the house bank, and it can suffer from "relay cycling" which will drastically slow house bank charging.. On cruising boats all charge sources go to house then the ACR passes the few amps necessary to keep the start battery topped up.
A start battery at 12.5V makes very little sense. Ideally you should rarely if ever see it dip below 12.7V except for a few minutes after starting the motor. Starting one of these motors uses about 0.1 to 0.3 Ah of battery capacity..
Make sure the solar panel isn't confusing the alternator. My panel supplied 14V to the batteries. The alternator saw 14V and did not charge. You may need to install a switch to turn the solar panel off when motoring. I don't know of a regulator that accounts for all sources of power automatically.
L
#1 If the solar is capable of maintaining the current to the battery to hold it at absorption voltage then the battery is nearly full charged anyway and the alternator current was not needed.
#2 Unless you have GEL batteries 14.0V is far to low to be healthy for your batteries. AGM and flooded deep cycles charge at 14.4V (min) to upwards of 15.0V depending upon brand and type). For example the most healthy abssorption voltage for flooded Trojan batteries is 14.8V., 14.0V would be grossly
under charging them. Any alternator shutting down at 14.0V (unless charging GEL batteries, and even then it should be 14.1V - 14.2V) is not charging the batteries correctly anyway.
#3 When charging in
bulk all current sources will provide all the current they can. When the batteries attain absorption voltage, using a small current source such as solar, the batteries are at or near 95% - 100% SOC anyway. A large current source can hit absorption voltage as low as 65% to 80% SOC depending upon
how much current you are feeding the battery. Where you hit the absorption voltage limit, in terms of SOC, depends upon
how much current you can deliver to the bank.
#4 A correct multi-charge source set up on a cruising boat includes "staging" of voltage limits. The largest current source gets the highest voltage eg: alternator regulator set 0.1V above solar controller. This way the solar controller can't bump the alternator off-line. When the alt is shut off the solar controller comes back on. This is another reason why it is best to purchase charge equipment that allows full programing capability.
#5 All the charge equipment we use in the marine environment is CC>CV or Bulk/constant current (
max potential for alts and solar and wind) and then constant voltage (absorption, float, "maintenance" or equalization).
All these charge controllers or regulators know is;
"
voltage has not been reached",
"
voltage has been reached"
"
voltage is over my limit".
"Voltage has not been reached." = Bulk/Constant Current / Max Current Potential. Battery voltage is always rising in this stage and all charge sources will deliver all the current they can.
"Voltage has been reached" = Constant Voltage / Voltage Limiting. The controller or voltage regulator
limits voltage to this level. Once voltage is held steady current has to decline based on terminal voltage and SOC. The first part of voltage limiting is called "absorption". During absorption voltage is held steady and the current declines until the battery is full, or darn close, (far too many crappy charge sources drop to a float voltage limit prematurely) before it drops to a lower voltage limit called "float".. The controller or voltage regulator is simply making sure its voltage limit is not over shot and it reduces charge current (via PWM) in order not to do this.
"Voltage is over my limit" = If system voltage exceeds the regulators "limiting voltage" the controller or regulator has no choice but to simply shut off until the voltage drops back to within its limit range.. If the source shutting off is one of your large current sources, such as an alternator, once it shuts off, and that current is lost from the system bus, voltage may drop. Voltage will drop if SOC is still low enough for the small current source to not be able to "maintain the voltage limit". When the large current source drops off the bus, but the small current source can no longer maintain the voltage limit, the large current source will simply kick back in. This is called "ping ponging" and can only happen at higher SOC's. The correct way to avoid this is in programming and regulator or controller choice.
Bottom line? If the small current source kicks an alt off line, and the alt is not kicking back in, it did not need to re-start because all the bank will accept, in current, is what the solar can provide. Proper controller selection and staging voltages based on how you use the boat is the Rx....
