Some thought on Battery charger settings

[knotflying]

As you know we always hear that we should not mix battery types since the charger settings can only handle one battery type setting at a time. As I was reading my manual on the Promariner Combi the difference in output numbers for the various stages seems so insignificant. Then I started to think, our alternators have no switch for battery type and they put out some pretty hefty voltage, like 14.4 Volts. I can see keeping battery types the same on a specific bank, but is it really necessary between banks. Perhaps tenths of a volt does make a difference. Anyone out there that can shed light on why mixing would really be of concern?

 

[NorthernFocus]

...Perhaps tenths of a volt does make a difference. Anyone out there that can shed light on why mixing would really be of concern?

According to theory the slight differences do matter for optimizing battery condition/life. How reality meets theory is probably different for each of us based on how we use the equipment. Plus if you routinely replace the batteries based on the calendar rather than condition it likely makes no difference.

Regarding the alternator output voltage for most applications that voltage is applied for short periods of time while the engines are running. If you operate for longer periods of time at low RPM (like we do) you will cook water out of the batteries due to the high voltage/overcharge. For that reason I've replaced the "maintenance free"(aka ignorance is bliss) batteries with old school lead acid types on our boat. They use enough water to require filling after every week or so of operation.

 

[BB marine]

I agree with NorthernFocus and good subject by Knotfling. Our boats have a good battery charger for maintaining all types of batteries. Different battery chemistries require different charging rates ,fast , slow, and higher voltage to maintain close to 100% charge. We have new school chargers with old school electrical systems. The electrical 12V system is no different then a boats electrical system built in the 80's. Alternator 14.3V regulator, , Battery isolator, battery switch, house battery, ( thruster) Cranking. To take advantage of the new technology batteries the complete charging system has to be encompassed in the design. Smart regulators have to be installed and alternators have to be sized up to maintain all systems while under way and also charge the batteries for their charging needs depending on battery type. Keep it simple use wet batteries of same capacities ( I prefer maintenance free 1000MCCA engine, 800 MCCA house and thruster) and plan on replacing them every 3 years. With the use of the Promariner charger if it does as advertised and does maintenance on the batteries maybe 4 years. I'm going on three years this season with our Cutwater. In the past I have always replaced after 3 . The batteries were still usable but why chance it? Mixing up batteries really isn't going to make a difference if I do this.Why spend extra money on new technology to get an extra year or two of life out of them, Maybe???

 

[Searaypaul]

I have personal experience and knowledge about mixing battery types. Our boat was delivered new with two big battery banks, bank 1 was flooded and bank 2 was gel cells for the house. It has “smart” ACR relays, regulators etc.

We burned thru 3 or 4 sets of wet cells in 3 years and 1 set of gel cells before I wised up courtesy of the school of hard knocks. The charger was set for charging gel cells since it could only charge one type battery at a time and the voltage regulator for the alternator was set the same.

What was happening was the charger and or alternator was trying to equalize the charge across all batteries and banks. This is not ever going to happen since the basic voltage of the two battery types is slightly different. Depending on what the charging source was seeing as the voltage of each bank at a certain moment in time it would apply what it determined to be the corrected charge to equalize and charge each bank. This is effect is best explained by remembering what happens with a shorted battery in a bank. The one battery will destroy the entire bank as all batteries attempt to equalize.

The next problem is that the different setting for the charging device causes a different profile at each setting. These profiles can reek havoc with the wrong type of battery. Charging is an exothermic reaction that produces heat. Different profiles produce varying amounts of heat if the battery load is wrong. Heat is not good for your batteries. I used a IRGun to track the battery temps vs profiles, very interesting.

The last thing is it will ruin your charging source. My charger died and the regulator died. At that point my lessons were over. I replaced the charger, regulator, and all batteries with flooded cells. The heat profile and the electrical profile were completely different than I had ever seen before. Hope this helps someone.

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[stwendl]

I wonder if anyone thought of disconnecting the charging leds from a gel, lithium or whatever alternate starting battery and use a separate dc/dc charger instead. That way you can have for instance a lithium light weight starter battery to tether with some lead based house batteries or vice versa. There is no rule that one has to have a single charger only. Some other changes may need to be made like disconnect the acr between the both systems. Yes it gets more complicated that way. I personally keep an emergency lithium battery on board for startup no purposes which simply gets charged by a 12v source and has its own intelligent charge circuitry inside. The is a carry on unit, which is strong enough to start my diesel truck alone without batteries connected. It’s made by noco model number gb150

 

[NorthernFocus]

Reading searaypaul's post reminded me of prior discussions about the ProMariner chargers that were supplied with the earlier boats. There have been various threads on this topic in the past. The small charging voltage differences for various steps for different battery types aren't much and likely not that big of a deal. However, the voltage that is sensed by the charger can goof up the works. Even with all flooded cell batteries this can be an issue as evidenced by prior discussions about forcing the ACRs open when on charge. With the charger on our boat even with ACRs open the charger never drops down to float charge. So while it all seems simple in theory the devil is in the details for each individual set up.