Are charging sources additive?

[Alpina]

If underway, with the generator running and a sunny day (335W solar panel) putting out 10A, are the energy sources additive for charging the batteries, or is there a limit? If so by what?

Trying to understand if I can charge faster with multiple sources.


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[Eric R]

Following this one, as I was just wondering this exact same thing yesterday while cruising!

 

[Craigmconrad]

Great question. I have a Victron MPPT Smart Controller providing solar charge to the House Bank and I also use the SmartShunt which is showing battery status and Volts/Amps to and from the House Bank. Tomorrow I will run my Air Conditioner using the batteries only (-70a draw). Then start the engine (+20-35a charge) and take a reading. SmartShunt should show -35-55a draw. Then I will close my solar breaker and note the solar output and see if it subtracts from the amp draw. So if solar is putting out +10a, I should see -25-45a draw on the SmartShunt (In Theory). I would expect to see the reverse if there isn't a high load on the House Bank. However, this would be hard since the Smart Controller and Eng. driven gen are smart, and throttling back the charge based on battery status.

Will post some numbers tomorrow.

 

[Alpina]

Following this one, as I was just wondering this exact same thing yesterday while cruising!

Displacement speed cruising gives you plenty of time to see and think. Very therapeutic.


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[Submariner]

You can have many charging sources for DC.

The OEM Factory Batteries support a max charge rate of .3C (C being capacity, .3 being 30% of). So 30% of 110ah = 33 amps per battery. A pair of Universal 110Ah batteries would then take upwards of 66amps as a max charge rate.

With the factory configuration of a 20 amp shore power battery charger, 20 amps from the engine at idle (thinking about the Yamaha F300 here), and 10 amps from the 160 watt solar (at near peak output)... You could run all 3 at once (tied up next to the dock). Turn everything off on the boat and you'd see about 50 amps (20 amp from shore power, 20 amp from the engine and 10 amp from solar) going into your house bank. That would re-charge your house bank back to 80% in well under 2 hours.

Realistically, you'd see less as the boat will consume some of those amps for the refrigerator and other loads, and the solar will rarely output at 10amps. But to see 35 amps total from all 3 sources is reasonable.

I upgraded our house bank to three Firefly Oasis batteries. 348Ah total capacity. Firefly batteries will take .5C (50% capacity) charge rate. Technically, I could feed them upwards of 170 amps to recharge them. There is no way I can generate anything near that amount. I'm almost done with my battery charger upgrade. I'm putting in a Victron Skylla IP65 battery charger (70 amps at 12volt). To run it with the Abso 20 amp charger, I'll be able to put in at least 90amps. Then idle the Yamaha F300 for another 20 amps. 400 watts of solar for say, another 20 amps. I may be able to get as high as 130amps charge rate, minus the current loads on the boat (usually about 10 amps). So 120 amps is what I think my max charge rate will be.

Charging sources are additive with multiple sources.

 

[Submariner]

It's also important to note the 3 stages of battery charging. Bulk, absorption and float.

In the bulk phase of the battery charging, the battery is less than 80% charged. That's where you can put the most amount of current back into them. It's in this phase that the max charge rate applies.

In the absorption phase, the batteries can't eat those electrons as fast. This phase takes hours to get from 80% to 100%. The closer to 100% the batteries get, the slower charge rate they will accept. Think 10 amps, then 9 amps, then 8 amps... etc...

The float phase is just as it sounds. That just keeps the batteries topped off because they are at 100%.

I've seen our solar controller flip to the "float' stage (0 watts) while underway. Plenty of sun, but the house bank is 100% charged.

When we're underway, the only phase I care about is the bulk phase as it's the only phase I can put those electrons back in quickly. If my bank goes above 80% charged, it's because of solar, or I'm back in our slip connected to shore power.

 

[Submariner]

It might also help to know what I have installed on Channel Surfing (R27-OB).
This is where I get all the numbers about electrical usage that I cite from.

Victron BMV-712 Battery Monitor
Victron MPPT Smart Solar Controller 100/30
Victron Voltage and Temperature sensors (one each for Engine, Thruster and House battery).
(The house Voltage and Temp sensor is paired with the MPPT Solar controller for accurate charging from solar)
Victron Skylla IP65 70amp battery charger (soon, almost done with the install).

Victron Cerbo GX which ties all the above together.
(The BMV-712, MPPT, and Skylla all plug into the CerboGX with a cable)
The CerboGX then connects via WIFI to the Garmin Chartplotter and to my phone.

Battery Monitor (Victron BMV-712)
http://www.tugnuts.com/gallery2.php?g2_itemId=79825
Showing a charge rate of 88 amps going in. (shore power with 2 battery chargers + solar power + engine power)

Solar Controller (Victron SmartSolar MPPT 100/30)
This shows 3 days of real-world usage with 400 watts of Solar.
http://www.tugnuts.com/gallery2.php?g2_itemId=79829
(this shows the 200 watt to 400 watt upgrade clearly)
http://www.tugnuts.com/gallery2.php?g2_itemId=79832

Garmin Chartplotter Victron app
Screen shot of the Victron app
http://www.tugnuts.com/gallery2.php?g2_itemId=79838
Victron App with real-world data, solar + DC loads
http://www.tugnuts.com/gallery2.php?g2_itemId=79841

Garmin Active Captain with Victron App data on my phone
http://www.tugnuts.com/gallery2.php?g2_itemId=79844

Victron Cerbo GX display on my phone
http://www.tugnuts.com/gallery2.php?g2_itemId=79835
This shows Solar (Pv) is giving me 154 watts and the boat is consuming 156 watts. My house bank is providing 1 watt. (I assume it's 1watt and not 2watts, due to a math rounding error in Victron's software).

I'm going to do a video for our YouTube channel here in the coming weeks over this.

 

[Alpina]

Thanks for the feedback. Conceptually I figured they were but wasn’t 100% sure. I’m finalizing my SmartShunt install so I will be able to monitor the input of various sources and the output as others have. Good call out in the state of the batteries in being a potential limiting factor on what they can receive as an input.


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