Charging 12 volt battery from a larger 12volt battery

[Raj]

You could use two 50 to 60 amp hour 12 volt AGM batteries wired in series to make a 24 volt battery bank, a 24 volt PWM controller and a couple of 100 watt panels in series to charge them, then connect a 12 volt PWM controller between 24V bank and the 12V glider batteries for charging.

[Suprasoup]

Sensij is correct.The second charge controller was intended to protect the 7AH battery and provide the correct charging cycle and float when it is left unattended for a week or two. Yes AZ the 1212-15 would work for sure but its nearly $300 Australian.Ideally I would love to find a boost converter that has a charging algorithm for SLA all in one component but I don't know if such a thing exists. I suspect that is what the $300 chargers that AZ pointed to are.My setup if it will work would be only $40 or so but I do not know if it will actually work.

Morningstar makes a PWM controller that can charge two batteries simultaneously. Called the Sunsaver Duo. Each output can be configured separately for different battery chemistries. There is also an option to split the charge so one battery can be prioritized. Might simplify your setup.

Supra

[bcroe]

I know of no PWM controller that can control the charge from a "stiff" power source (DC-DC) converter.

Right, don't even try it. Bruce Roe

[Mike90250]

I know of no PWM controller that can control the charge from an "stiff" power source (DC-DC) converter. Either it will trip the DC-DC offline from the PWM spikes, or if the DC-DC is "stout enough", the Fuse or MOSFET in the PWM will blow.
Finding just the right balance between the DC-DC & PWM will be fun, so go ahead.

[Raypat]

Thanks Neoh. That looks exactly what I need. I could connect that to the load terminals of my solar charge controller and program it to safely charge the small batteries. Excellent.

[SunEagle]

This page from the same seller shows the 100 and 160 watt panel specs, side by side.

https://www.ebay.com/itm/100W-160W-1...IjlHfQQUgXocjg

Now that is clearer. It looks like the 160w mono cell panel uses larger cells since it is wider and taller then the 100w mono cell panel.

[littleharbor]

This page from the same seller shows the 100 and 160 watt panel specs, side by side.

https://www.ebay.com/itm/100W-160W-12V-PV-Solar-Panel-Poly-Mono-for-Battery-Charge-Car-Boat-Jeep-Home/351950052388?hash=item51f1db9c24:m:m46X3Hj02IjlHfQQUgXocjg

[littleharbor]

That size may be a typo on the sellers part. I see the same panel only just the panel, not the kit and it shows a 26.2" x 57.3" They carry 100 watt panels in the smaller 22' x 47" size.

[SunEagle]

These are 6" cells in a 4 x 9 arrangement. Typical 26" x 56" Approx. . Voltages are up a little but they are getting higher amperage from these more efficient cells. The Typical 100 watt panels are using 4" x 6" cells these days.
It does seem strange seeing 36 cell panels putting out more power than the 72 cell panels from not so long ago. There's still a viable market for 12 volt panels from my experience and these higher output modules are certainly welcomed.

I see that some of those higher wattage panels are 26" x 56" but some are still 22" x 48" which is the size of that 160watt one that NEOH posted and is pretty standard for 80 to 120 watt 12v panels using 5" cells. I have 6 panels in the 80w - 90 watt range which were purchase about 5 years ago.

Again the older cells are probably just less efficient so the output is limited to less amps then the newer versions.

Also it is nice to see the 36 cell panels have come way down in price per watt.

[littleharbor]

I see that. I guess I am a little confused since the number and size of the 36 cells is not more than say a 100 watt panel.

I am not sure how they are getting a higher Vmp or Imp to generate more wattage without using bigger cells.

I guess they have found a way to increase the efficiency of a 5" cell compared to the ones found on earlier version panels.

These are 6" cells in a 4 x 9 arrangement. Typical 26" x 56" Approx. . Voltages are up a little but they are getting higher amperage from these more efficient cells. The Typical 100 watt panels are using 4" x 6" cells these days.
It does seem strange seeing 36 cell panels putting out more power than the 72 cell panels from not so long ago. There's still a viable market for 12 volt panels from my experience and these higher output modules are certainly welcomed.

[SunEagle]

They're making 175 and 180 watt 12 volt panels as well.
https://www.ebay.com/itm/1-175-Watt-...YAAOSw-29ZXumz
https://www.homedepot.com/p/Grape-So...W-US/301024442

I see that. I guess I am a little confused since the number and size of the 36 cells is not more than say a 100 watt panel.

I am not sure how they are getting a higher Vmp or Imp to generate more wattage without using bigger cells.

I guess they have found a way to increase the efficiency of a 5" cell compared to the ones found on earlier version panels.

[littleharbor]

They're making 175 and 180 watt 12 volt panels as well.
https://www.ebay.com/itm/1-175-Watt-...YAAOSw-29ZXumz

https://www.homedepot.com/p/Grape-Solar-180-Watt-Monocrystalline-PV-Solar-Panel-for-Cabins-RV-s-and-Back-Up-Power-Systems-GS-STAR-180W-US/301024442

[SunEagle]

Raypat ,

Yes, you can charge your 7 AH 12 volt batteries from a 60 AH 12 volt battery.

All you need is something like this ...
https://www.amazon.com/OptiMATE-TM-5.../dp/B011J76CFE

I am not recommending that particular model.

If you do not understand the PV Solar Panel stuff,
then just buy a kit containing the 200 Watt Solar Panel & 12 Volt Charge Controller.

Like this ...
https://www.ebay.com/itm/160-Watt-Of...kAAOSwHsRYCDGF


Buy the 60AH Deep Cycle battery from Walmart
$80 = Marine Deep Cycle Group 24DC
$90 = Marine Deep Cycle Group 27DC

Interesting. I have never seen a 36 cell 160 watt panel before but I guess they are being made.

[NEOH]

Raypat ,

Yes, you can charge your 7 AH 12 volt batteries from a 60 AH 12 volt battery.

All you need is something like this ...
https://www.amazon.com/OptiMATE-TM-5.../dp/B011J76CFE

I am not recommending that particular model.

If you do not understand the PV Solar Panel stuff,
then just buy a kit containing the 200 Watt Solar Panel & 12 Volt Charge Controller.

Like this ...
https://www.ebay.com/itm/160-Watt-Of...kAAOSwHsRYCDGF


Buy the 60AH Deep Cycle battery from Walmart
$80 = Marine Deep Cycle Group 24DC
$90 = Marine Deep Cycle Group 27DC

[Raypat]

Sensij is correct.The second charge controller was intended to protect the 7AH battery and provide the correct charging cycle and float when it is left unattended for a week or two. Yes AZ the 1212-15 would work for sure but its nearly $300 Australian.Ideally I would love to find a boost converter that has a charging algorithm for SLA all in one component but I don't know if such a thing exists. I suspect that is what the $300 chargers that AZ pointed to are.My setup if it will work would be only $40 or so but I do not know if it will actually work.