Advice Wanted! Dual Battery/Solar Set Up

[dms1]

@mmaattppoo, thanks for that info

 

[Greg_Volkman]

Educate yourself. Read: https://handybobsolar.wordpress.com/ then read it again.

This guy's site is great. he confirmed some things that i noticed when building my small little offroad trailer's system, and he also showed me I did a few dumb things that need to be fixed!!

what I don't see is an explanation of the types of charging. my optima's can be charged on generator or shore power to 15 volts. Optima says to float charge them at 13.8. Not sure what the difference is, other than the method, or why you'd float them at less. I have two Optima D31T batteries and a 100W panel. The batteries are yellow top, 75AH. I'd like to charge them up to 15 if I can, with my solar controller.

 

[luthj]

This guy's site is great. he confirmed some things that i noticed when building my small little offroad trailer's system, and he also showed me I did a few dumb things that need to be fixed!!

what I don't see is an explanation of the types of charging. my optima's can be charged on generator or shore power to 15 volts. Optima says to float charge them at 13.8. Not sure what the difference is, other than the method, or why you'd float them at less. I have two Optima D31T batteries and a 100W panel. The batteries are yellow top, 75AH. I'd like to charge them up to 15 if I can, with my solar controller.

Handybob rants too much, and is has a few incorrect assumptions. Wiring losses, shading, and components selection (including charge votlages) is important though.

Here is some reading about lead acid charging regimes. A true 3 or 4 stage charging profile is necessary to fully charge and maintain lead acid batteries. Lead acid batteries must be returned to 100% state of charge regularly if they are going to last any real length of time. Not 99%, 100%. This is why the correct length and voltage of absorb phase is so important.

http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery

 

[calicamper]

CTEK sells the D250S Dual 12V DC to DC multi-step smart charger. This product includes the ability to charge a house battery from both your vehicle's alternator and from solar panels using an inbuilt MPPT solar charge controller. This product is readily available in Canada and the States through the usual online sources.

There are other products out there but I'm not sure about their availability in North America.

I've been running the D250S Dual in my Jeep to charge a Northstar 76 Ah AGM deep cycle marine house battery for almost two years and more recently with 150 Watts of rigid monocrystalline panels. Charging from the alternator is at a maximum of 20 amps unless you opt for the Smart Pass add on which bumps the maximum charging current from your alternator up by an additional 80 amps (100 amps max total). Charging from the solar panel is limited by the capacity of the panels (minimum of 40 Watts I believe) and solar irradiance and environmental conditions.

For my setup (pictured below) I've seen charging currents of up to 6.5 - 6.9 amps from my panels under clear sky mid-day summer sun. These values decrease when the sun is lower on the horizon

Solar Panels

D250S Dual, inline power monitor, distribution panel, and house battery.

Based on my usage (primarily a 37 qt ARB fridge/freezer at approximately 312 Watt•hr per 24 hr period) my panels take approximately 4-5 hrs to recharge back to 100%); easily achieved where and when I tend to camp (southern British Columbia in the late spring and throughout the summer). YMMV. More sun, higher capacity panels, and/or a larger capacity battery would allow you to harvest more power each day and ride out days with less than ideal solar charging conditions.

I also hardwired a CTEK Multi US 7002 battery charger to my starting battery (pictured below) for the occasions when I have access to 120 Volt mains shore power. The battery charger charges the starter battery and the house battery (through the D250S Dual).

Battery Charger

NOCO weather resistant socket for plugging extension cord into battery charger.

Hope this helps.

Cheers.

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Cool set up. One thing did you box the battery in some way to prevent loose gear from contacting exposed terminals? Curious what you did given I'm eyeing a similar idea.

 

[mmaattppoo]

Cool set up. One thing did you box the battery in some way to prevent loose gear from contacting exposed terminals? Curious what you did given I'm eyeing a similar idea.

At this point I haven't boxed the battery. I have a battery box with lid but for the time being the main positive terminals and most of the secondary terminals are covered with self adhering silicone tape as protective insulation. The terminals associated with the 50 amp resettable breaker could do with some more protection beyond the rubber caps it came with.

The current configuration is potentially susceptible to having something short out one of the positive terminals but with the silicone tape, and not having any loose gear in the rear cargo area while driving (i.e. all gear is binned and secured in place with cargo straps) the potential is quite low.

Once I have my setup finalized I'll likely be placing the battery in a protective box.

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