Been having some problems with batteries lately and my dock neighbor asked me which battery was dedicated to cranking. I have two batteries, how can I tell if one is dedicated to cranking.
Battery question
- Thread starter bigsick
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Follow the wiring. In most cases the batteries should be kept separate-- one deep-cycle for 'house' circuits and one for engine-starting circuits. If you have such a setup, under no circumstances should they be tied together by any wiring whatsoever. That includes the 1-Both-2-Off switch too. (The only exception is if you have a 'smart' two-bank charger.) These two different types charge and discharge at different rates and in different modes. Keep them separate.
In effect the 'cranking'/engine-start battery is a car's starting battery, only better-made and with proper marine-type connectors on it. It is rated in CCAs (cold-cranking amps). The deep-cycle (RV type) battery will be heavier, marked as 'Deep Cycle' and possibly larger. It is rated in Amp-Hours, reflecting how much load can be carried for how long before it reaches a critical 40-percent charge level, at which point it is considered 'fully' discharged.
Always keep both kinds topped-off as much as possible; although the deep-cycle will last longer if it is allowed to go through full cycles (full charge to fully 'dead' and back again).
In effect the 'cranking'/engine-start battery is a car's starting battery, only better-made and with proper marine-type connectors on it. It is rated in CCAs (cold-cranking amps). The deep-cycle (RV type) battery will be heavier, marked as 'Deep Cycle' and possibly larger. It is rated in Amp-Hours, reflecting how much load can be carried for how long before it reaches a critical 40-percent charge level, at which point it is considered 'fully' discharged.
Always keep both kinds topped-off as much as possible; although the deep-cycle will last longer if it is allowed to go through full cycles (full charge to fully 'dead' and back again).
I guess one way would be to disconnect one battery pos terminal and see what doesn't work.
Alternatively, I assume your boat has a battery on/off/??? Switch. What happens when you use it?
Diana, If both batteries are flooded lead-acid (even if one is "starting" and the other "deep cycle") surely they can be connected together for charging, can't they?
I have a Group 27 AGM for starting, and two G27 flooded for house. I was advised on this site, that there should be no problem connecting them together (even though it may not realize the full potential of the AGM).
The reason I connect them together for charging is that when I don't, and I leave the switch on "1", then the load from my use of appliances comes out of the "1" battery and is not topped up by the charger. Or, if I switch is set to "2" the load comes out of the "2" battery and is not topped up.
This surprises me, and I would like to know why, but in the meantime charging on "ALL" solves the problem.
Do you, or anybody else, have any ideas why this may be? The battery charger is stock for a 2006 Hunter 33 - ProMarine, Protech 4. Model 1230, part # 61230. Output 30A. It does have two independent charging circuits.
I'm also surprised that you say that the deep cycle will last longer if put through deep cycles. I've always thought that a lead acid should preferably be kept as nearly full charged as possible for longest life. Any comments?
The small auxiliary diesel engines found in the Hunters do not require the cold crancking amps of a starting battery as they can easily be crancked by a deep cycle battery. It is very common in small battery banks to just have deep cycle batteries to do double duty for house and starting. The simplest system is a two battery setup connected to a selector battery switch. Both batteries are the same and can be combined or isolated via the switch. By moving the selector you designate which battery will carry the electrical load. It does not hurt to check which type batteries are installed in your boat. Before doing anything else it is important to establish the current health status of each battery. The simplest way if possible is to remove the batteries and take them to an auto parts store and have them tested. You could do it in the boat but you will need some tools and some know how. If the batteries check out good and are fully charged then your problem lies in the circuit that you may be experiencing problems with. If one battery or both are low in charge it could be the problem could be traced to the battery charger. Understand that when underway the battery that will receive charge from the alternator is the one selected unless you select Both and then the two of them will receive charge. Let us know what problem you have been experiencing and perhaps we can offer some assistance in troubleshooting the cause.
Okay here is update. Pulled both batteries, put volt meter on charger and both battery cables register 15-16 volts when charger turned on. So probably not charger. Batteries are 2 years (deep cycle 690 CCA) and 3 years old (500 CCA). Had tested at auto store and the 500 CCA was down to 50 Amps, so it is done, the 2 year old is fine. I can only think that when I pulled out this winter the battery must of died. I did not put on a trickle charger this winter and they were stored on cement floor (I hear that is not good). So I should probably get another deep cycle battery comparable to the one I have. On boat I experimented and both battery banks start boat and run on board electronics, but battery 1 seems to keep CO2 detectors running while 2 does not. Maybe I should keep the 1 battery designated as house battery and as start battery.
That about sitting them on cement is a myth. You seem to have a hybrid deep cycle/starting battery and a pure starting battery. The lead plates on the hybrid are thicker than those on a starting battery but lighter than on a true deep cycle. I would recommend that you eventually go to true deep cycles as they will give you a longer useful life in the number of charge/discharge cycles. My personal preference in a two battery setup is to alternate between using #1 and 2# on outings. When using #1 I'll would leave #2 as a backup and next outing I would reverse the roles. This way I would exercise both batteries and always have one for backup. I would only combine and use "Both" when I needed a boost to start the engine or when motoring for a lengthy time tomake sure both received charge from the alternator. Beware that if one battery is down in charge and you join them the power will be drawn from the full one to the one with less charge. I hope the batteries were connected when you tested the charger. Voltage should be in the 13-15volts range and not as high as perhaps 16V. Get two good batteries and then test voltage again. Batteries even when not connected will discharge themselves over time. A discharged battery will sulfate and its capacity to hold power will be gratly reduced. The older the battery the quicker it can happen and that is probably what happened to your 2nd battery. I think you mean CO (carbon monoxide) and yes the emission of charging gases can trigger false alarms but it all has to do with the battery itself and not the position you may have assigned to it. A battery that is overly gassing can be on its way out but if the problem remains on the bat #1 location the charger or the way it is hooked up may need further checking. You do not want an overly high charging voltage cooking your batteries.
15V to 16V is waaaaaaay to high of a normal absorption charging voltage. 15V-16V is a very short term equalization voltage when someone is there to over see this otherwise it can be dangerous to leave unattended. Either your charger is bad or your volt meter is quite inaccurate. You should see 14.2V - 14.6V on most normal marine chargers in absorption mode and 13.2V to 13.8V in float mode.
This is simply un-true. Wet/wet can be charged combined 100% safely and effectively. It is myths like this that get spread around the net and scare people.
Batteries combined will get charged the same way a "smart charger" does and the only difference is that the charger uses diodes on the output channels to prevent cross flow between banks especially during starting or periods of high draw to save the relatively small wires from becoming "parallel" bank wires.. With combined banks each battery will accept only the current it needs and the voltage across the new "combined" bank will be the same so "over charging" of one bank vs. the other is not possible.
This is a popular misconception people often have about batteries charging "combined"..
As long as both banks are the same chemistry eg: AGM & AGM or WET & WET or GEL & GEL than there is absolutely no problem doing this. In fact companies such as Blue Sea, Victron, BEP, Yandina, Sterling Power, Newmar, ProMariner and many others offer automatic COMBINING relays that only combine during charging and then automatically disconnect when under discharge. They do exactly the same thing as the BOTH position.
Yandina invented this type of device and have sold over 20,000 of them all with an unconditional guarantee. Blue Sea has likely sold over 50,000 "combiners". They are one of the more reliable devices used on boats today. These devices are simple, eloquent and work all without the voltage drops associated with diode type splitters..
Yandina Automatic Battery Combiner (LINK)
Blue Sea Automatic Battery Combiner (LINK)
Victron Automatic Battery Combiner (LINK)
BEP Automatic Battery Combiner (LINK)
Sterling Power Battery Combiner (LINK)
ProMariner Battery Combiner (LINK)
Newmar Battery Combiner (LINK)
All of the above devices COMBINE batteries, just like the BOTH setting on a battery switch. The difference is they don't forget to un-combine during discharge, like a human can...
Most every battery manufactuere out there recommends 50% as the max depth of discharge for the best longevity and run times. A 40% SOC is a 60% depth of discharge and will lead to shorter life than going to 50% /SOC/DOD.
During break in you should cycle your bank to 50% or so. But after that the shallower the cycles, and the more often you get back to full, the longer the life of the battery. Running the battery to 50% SOC every time you use it vs. 70% SOC will result in less cycles than only discharging the bank to 70% SOC each cycle.
Thought that myth about setting on concrete sounded funny. I did not have batteries connected when checking battery charger (did I screw something up). I read my directions for protech 4 charger and it indicated to disconnect batteries when checking voltage of system. As far as reading on voltmeter, it may of been in the 14-15 range. I do not have a digital meter, just a meter with 0-50 and the needle was pretty much in the middle of 10 and 20.
Yes get a digital volt meter to get readings to 2 decimal points. Test the calibration against a kown voltage source. The purpose of disconnecting the batteries is to fool a multistage charger into going into bulk charge mode so you may check maximum output. When testing to see if a charger is good or not I prefer to test charger output voltage at the battery posts when these are connected. Any voltage above 14.5V would draw my attention to check further and over 15V would be a clear indication something is amiss. Readings in the 13V range may indicate the batteries are quite charged and the charger has gone into a maintenance mode. A voltage less than 13V may again indicate a bad charger or fouled connections.
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