Keep It Simple Solar

[dreadlocks]

4A is only like 48W, into a >200AH battery that's pissing in the ocean.. thats about what your trailer plug is gonna see.. part of the abuse deep cycles take better than starter batteries is going days without a recharge, but all lead chemistries should be recharged to 100% SOC asap for longevity.. nothing lead based particularly likes to sit partially discharged.. and very slowly absorbing a battery risks overcharging it.

Generally I try to shoot for (1C = Capacity in AH as a Charge Rate)
Flooded: 0.05C Minimum / 0.1C-0.15C Ideally / 0.2C Max
AGM: 0.1C Minimum / 0.2C Ideally / 0.4C Max
LFP: 0.2C Minimum / 0.4C Ideally / 0.5C Max

So for 200AH of Flooded * 0.05 = 10 Amps of Charge current Minimum / 20-30 Amps Ideally / 40 Amps Max

Max for Flooded/AGM is kinda loose, you can hookup any size charger you want and it wont take more than is safe for it.. but if you go over max ur not really getting anything for your money because you'll never really see much more charge current, Ideal is best bang for buck as more wont necessarily charge it that much quicker.. Max for LFP is a hard max, as those will take way more than is safe and you need to be limiting current.

With the gear you have, I'd use the onboard Genius charger for float/maintenance.. and your 15A shop charger when you get back from camping to Bulk/Absorb it up for best health.

 

[FosterWV]

4A is only like 48W, into a >200AH battery that's pissing in the ocean.. thats about what your trailer plug is gonna see.. part of the abuse deep cycles take better than starter batteries is going days without a recharge, but all lead chemistries should be recharged to 100% SOC asap for longevity.. nothing lead based particularly likes to sit partially discharged.. and very slowly absorbing a battery risks overcharging it.

Generally I try to shoot for (1C = Capacity in AH as a Charge Rate)
Flooded: 0.05C Minimum / 0.1C-0.15C Ideally / 0.2C Max
AGM: 0.1C Minimum / 0.2C Ideally / 0.4C Max
LFP: 0.2C Minimum / 0.4C Ideally / 0.5C Max

So for 200AH of Flooded * 0.05 = 10 Amps of Charge current Minimum / 20-30 Amps Ideally / 40 Amps Max

Max for Flooded/AGM is kinda loose, you can hookup any size charger you want and it wont take more than is safe for it.. but if you go over max ur not really getting anything for your money because you'll never really see much more charge current, Ideal is best bang for buck as more wont necessarily charge it that much quicker.. Max for LFP is a hard max, as those will take way more than is safe and you need to be limiting current.

With the gear you have, I'd use the onboard Genius charger for float/maintenance.. and your 15A shop charger when you get back from camping to Bulk/Absorb it up for best health.

That makes sense and would work. Thx again it took me awhile to grasp all the options but I def have a plan now.

 

[john61ct]

EPM is in general a great company, but their AGM line is meh for true deep cycling, but may well be "fine" for 4-6 years depending on your care, temperatures, avg DoD% etc

Here’s a link to the battery not sure what the ah value

"20 Hr Cap" is the spec to use, figure over estimated by 10% or so

and 50% of that is the maximum usable Ah you want to pull out, unless in an emergency.

Getting back to 100% Full as per endAmps, as quickly and often as possible is important for longevity

takes at least 6-8 hours, and couple/few times per week should be the goal, "most cycles" even better.

 

[FosterWV]

@dreadlocks suggestions on how to know when I’ve reached half charge? To keep from damaging the batteries. Budget friendly if possible. Thanks

 

[dreadlocks]

The most budget friendly way is simply an accurate voltage monitor, once you get to around 12.0v you should find a charge source.. print this out and put it near the monitor.

Something like the Victron Battery Protect LVD can be installed to drop all loads automatically when voltage drops too low, that way if something runs away while your rig is unattended it will failsafe... gotta be carefull about which way the current flows through it though, chargers needa bypass the LVD and go right to the battery.

 

[john61ct]

Voltage is a **very** rough guide to SoC

the correspondence table varies a lot from one model / type to the next

and changes as the bank ages.

But if you are going to go that way then at least make sure you are letting the bank rest isolated for a few hours first

really 24hrs for accuracy, some chemistries take even longer to settle.

Note there are cheap Ah counting wattmeters, maybe $30-40?

 

[FosterWV]

Dreadlocks, I’ve seen a chart like that on the East Penn site. John I saw this on amazon had good reviews, thoughts? There’s a 100A and 350A model

AiLi Battery Monitor Voltmeter Ammeter Voltage Current Meter 8-80V 0-100A Auto Car Motor Boat Caravan RV Motorhome https://www.amazon.com/dp/B07CTKYFTG/ref=cm_sw_r_cp_api_i_24VdFb32XHWQ9

 

[FosterWV]

I picked up two Sam’s Club GC2 which are Deka East Penn model GC10. The website states 215 ah. Correct me if I’m wrong but 215ah x 2 batteries would be 430ah and useable to 1/2 charge would be 215ah and for easy math I pull 1ah that would be 215 hours of power or 8.95 days. I see why these are so popular and such a bargain at $89 each.

 

[dreadlocks]

I picked up two Sam’s Club GC2 which are Deka East Penn model GC10. The website states 215 ah. Correct me if I’m wrong but 215ah x 2 batteries would be 430ah and useable to 1/2 charge would be 215ah and for easy math I pull 1ah that would be 215 hours of power or 8.95 days. I see why these are so popular and such a bargain at $89 each.

Your wrong, it would be 430AH if you had a 6v system.. but you have a 12v system, so your wiring em in series to get to 12v, its gonna be 215AH @ 12VDC.. Wiring em in Parallel would double the AH Capacity, but wiring em in series doubles the voltage instead, capacity remains.

Ive not used one of those gauges so cant say if thats quality or not, but it looks good at first glance..

 

[FosterWV]

Your wrong, it would be 430AH if you had a 6v system.. but you have a 12v system, so your wiring em in series to get to 12v, its gonna be 215AH @ 12VDC.. Wiring em in Parallel would double the AH Capacity, but wiring em in series doubles the voltage instead, capacity remains.

Ive not used one of those gauges so cant say if thats quality or not, but it looks good at first glance..

ok thanks for the heads up 215AH and you can use 1/2 that before recharging would still be a nice 107AH that’s double the available usage of a Group 31 so that’s good enough for our 4-5 day trips.

 

[john61ct]

John I saw this on amazon had good reviews, thoughts? There’s a 100A and 350A model

Yes seen good feedback on those, just realize without Victron level programming of CEF, Peukert, updating declining SoH% etc

it will be a rough guide

but heaps better than voltage even at rest.

 

[john61ct]

Again, great value batteries those, best on the planet

but even a top lead vendor like EPM exaggerates Ah capacity.

To be conservative use say 85% as real when new.

Then deduct 5% for age/wear per year, or more if not well cared for.

And get recharged on average before usage hitting 50% of that.

 

[FosterWV]

ok thanks for the heads up 215AH and you can use 1/2 that before recharging would still be a nice 107AH that’s double the available usage of a Group 31 so that’s good enough for our 4-5 day trips.

@dreadlocks dude u have helped me a ton got another stupid question for ya tho....

So the Sam’s Club Deka Duracell GC batteries have been great thanks again for the tip!
My question is if I keep the trailer plugged into the vehicle when possible (at night) wouldn’t that add to my battery capacity? If that makes sense?

 

[FosterWV]

Assuming your car to trailer connection remains energised when the car is switched off...
Overall battery capacity is increased albeit at poor efficiency.
That also presents risk of discharging the car battery. But for some people thats not a problem.
Btw, some cars are configured where its trailer connector is constantly energised. Some are energised only when ’ign is switched on.

I will check if it’s key sensitive, thanks

so far 3-4 days it’s been fine I was just thinking if we do 4 days maybe leave the trailer plugged in the first evening/night.

 

[228B]

Hey Foster! Just read through your thread here and you did well for the money with your dual 6V/215 Ah batteries. Yes, wired in *series* you'll get one 12V/215 Ah battery bank. Use the appropriate wire gauge to interconnect them, and which AWG (wire gauge) you select will be the result of the 12V accessory loads you plan to use (look for their watts and/or amps rating).

As for solar, you can get roughly 6 amp from one 100W monocrystalline panel, but you must use at least 10 AWG wire for a short run to the solar charge controller, or 8 AWG for a longer (20'+) run, because the resistance along 20' of cable is a 40' distance there and back. And if you use solar, be sure to position the charge controller as physically close to the battery bank as possible, but be mindful of the batteries' outgassing when charging. Be certain to provide exterior air ventilation of the battery bank.

Learn how best to charge those batteries, first and foremost. Everything else is secondary. If you're not starting your day or your trip with a 100% fully-charged battery, you're going to be limited. This is why you want a good, basic solar setup in order to keep that battery at a healthy state of charge (and fully re-charged at least! once per week if not every day).

I am a student of Bob's, here. You will see me post this link often. I profit nothing, I only wish to help others realize a dialed house battery setup. Good luck.

The RV BATTERY CHARGING PUZZLE

Written in 2004 and continuously updated since. Last extensively revised December, 2010. If you found this by having somebody send you to it, you may not realize it is only one part of an extensive…

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