Charging 12 volt battery from a larger 12volt battery

[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.

[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

[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.

[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.

[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.

[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

[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

[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.

[Raypat]

Hi Raj, Yes I could do as you suggest and spend um I dunno but it sounds like plenty. Or I could just buy a charger like the one Neo has suggested. No boost converter needed so I guess I avoid the problem mentioned by Mike and Bcroe. If I understand correctly I should be able to connect that charger direct to the load terminal of the charge controller and be good to go. The charger will handle the voltage boost as well as the correct charge cycle ending in a float charge for the glider batteries. Am I right in my assumptions here or will the charger and the Charge controller not get along? Thanks again to all who have replied.

[Suprasoup]

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

He could use a hobbyist charger like this...

https://www.amazon.com/dp/B01HXHGARY/ref=dp_cerb_2

almost all of them have settings for lead acid batteries. I personally use a Hyperion eos0606i. I use it to charge HT radio batteries when out in the field. Whether it

[Mike90250]

......., then connect a 12 volt PWM controller between 24V bank and the 12V glider batteries for charging.

any PWM controller will last about 1 second before it blows out, PWM cannot protect itself. You have to use a MPPT controller, rated to work with batteries, in addition to solar sources. (Morningstar MPPT gear is approved for this use)

[Raj]

any PWM controller will last about 1 second before it blows out, PWM cannot protect itself. You have to use a MPPT controller, rated to work with batteries, in addition to solar sources. (Morningstar MPPT gear is approved for this use)

Thanks Mike, I forgot that the controller charging the 12V bank needs to be MPPT.

[NEOH]

Hi Raj, Yes I could do as you suggest and spend um I dunno but it sounds like plenty. Or I could just buy a charger like the one Neo has suggested. No boost converter needed so I guess I avoid the problem mentioned by Mike and Bcroe. If I understand correctly I should be able to connect that charger direct to the load terminal of the charge controller and be good to go. The charger will handle the voltage boost as well as the correct charge cycle ending in a float charge for the glider batteries. Am I right in my assumptions here or will the charger and the Charge controller not get along? Thanks again to all who have replied.

Do not attempt what Raj suggests in message #23 - bad idea.

You are on the right track by using ...

A) PV Charge Controller to the main battery bank and then use a DC-to-DC Battery-to-Battery Charger to recharge the small 7AH battery
This method will recharge the small 7AH during the night, so the 7AH battery will be ready to use first thing in the morning.

B) A Dual Battery Solar Charge Controller method
The problem with the Dual Battery Solar Charge Controller is ... it only recharges the small 7 AH during the daytime on sunny days - but that is when you actually need to use the 7 AH battery.

[Raypat]

OK Thanks Neo we finally got there. That is what I will do. I get it now that the second pwm charge controller was a bad idea and all I need is one of those with a DC-to-DC Battery-to-Battery Charger. The last piece of the puzzle for me is this. Can I connect the DC-to-DC Battery-to-Battery Charger to the load terminal of the solar charge controller to protect the big battery from over discharging which would be unlikely anyway or do I need to go direct to the big battery?

[AzRoute66]

If the Load terminals of the charge controller will provide enough amperage, and is smart enough to do a low voltage disconnect, I don't see why not. The risk of connecting it directly to your big battery is very minimal though, once the smaller battery is charged the current drawn by the charger should be minimal.