See full version: Connecting batteries in series
The reality is that no 6 volt battery is exactly 6 volts and no 12 volt battery is exactly 12 volts. Individual cell voltages differ, even with batteries of the same brand and manufacturer. A 6 volt battery might have a cell voltage of 2.2 volts and a 12 volt battery might have a cell voltage of 2.1 volts. This can however be fairly easy to read with a volt meter if one was to check.
In theory, a 6 volt 5 Ah battery and a 12 volt 5 Ah battery connected in series will give a supply of 18 volts (6 volts + 12 volts) and 5 Ah. A 6 volt battery is often three 2 volt cells and a 12 volt battery is usually six 2 volt cells. Therefore, all you have done is connected nine 2 volt cells together to get 18 volts … so what’s the problem?
Different wiring configurations give us different voltages or amp hour capacities.
The Sterling ProCharge Ultra uses a number of factors to adjust and adapt the duration of the absorption cycle to what it believes the battery needs. In terms of charge algorithms it works pretty well. A simple explanation is that the ProCharge Ultra examines the duration spent in bulk and can then add or subtract time spent in the absorption stage. This type of algorithm is certainly smarter than a simple egg-timer. While not perfect, it does a better job at keeping the batteries healthy than do many egg-timer based chargers. [links]
4- Try to find a location that is dry and will not have the possibility of water dripping on the charger. If there’s even a slight potential of water exposure a drip shield should be constructed to protect the charger. The drip shield should prevent water from damaging the charger, but also allow for proper cooling. This is not always an easy task so mounting in a known dry spot is always the best approach. Generally speaking, higher in the boat is often better than lower in the boat for a charger mounting location. Areas closer to the bilge, or with direct ambient access to the moist bilge air, tend to be more humid and corrosive environments.
The location your charger is mounted in plays a critical role in its life span & longevity. Care should be taken to follow your manufacturers instructions of orientation, access to air, moisture or battery gas exposure.
This 20A charger comes standard with three outputs which can be fed to three different banks. The output is distributed by demand not divided equally as some chargers are. So if a start battery was at 99% state of charge and your house bank was at 60% state of charge the house bank will be seeing the vast majority of the charging current and the starter would be seeing 1-2A or less.
The image below is for a single Group 31 Odyssey TPPL AGM battery. If you had four of these, for a 400Ah bank, you’d need 160A of charging to meet Odyssey’s “minimum” recommended charger guidance. The ProCharge Ultra can be run in parallel to achieve the minimum charge current guidance for batteries such as these. You can always choose to charge at a lower rate, but you are giving up cycle life by doing so.
11. Unplug the charger and disconnect from the battery.
2. Remove the battery from the boat when not using an on-board charger.
5. Wet cell batteries have caps. Open and inspect the fluid levels. Use distilled water to bring them to the proper levels. When needed, fill to just under the top of the ring leaving 1/4 inch of space for expansion. AGM batteries don't require this type of maintenance. here
Running out of power in the middle of a fishing trip can be frustrating and dangerous. It can leave you stranded and ruin your day. more
Does your new marine battery run out of power before it is supposed to?
12V to 24V Charging – BB122470:
Lead Acid Alternator Sizing – Sterling Power recommends that your alternator be sized (based on its SAE output rating) to be at least 30% larger than the B2B unit you choose. In our testing we found 30% to be a bit low for many “stock” alternators and find that double the B2B size means a much cooler running alternator. The reason for this is actually quite simple, you don’t want to tax your small alternator to death. Alternator output also varies based on RPM and winding temp. We see small alternators taxed to death quite regularly on boats. [links]
LiFePO4 Alternator Sizing – If you intend to feed a LiFePO4 battery bank with a ProBatt Ultra, and many do, then Sterling’s suggestion of 30% over-sized, for the alternator, we find to be rather inadequate. We recommend at least double the alternator rating, or larger for the B2B charger. So, if you want to use a 30A B2B on LiFePO4 then you would need an alternator rated at a bare minimum of 60A but preferably one sized for 80A would be much better. Each engine bay, and its heat characteristics, will be different, so predicting how much larger is impossible to really say. In our experiments with stock alternators we find double the B2B input rating for the alternator is a bare minimum. [links]
Just try to ensure your charge sources can exceed the demand placed on the B2B by the target bank. In situations where the B2B is charging only a start battery, this is not going to be a big deal, start batteries require very little charging hence little demand on the source bank charger, but as the target bank requires more current, such as a bow-thruster bank or LiFePO4 it can cause B2B on/off cycling so charge source sizing becomes more critical.